Engineer Intelligence Dossier I. . ' Strategic Study CAROLINES VSuth'Ie 19 ANALYSIS OF THE ‘ NATURAL ENVIRONMENT MILITARY GEOLOGY OF TRUK ISLANDS, CAROLINE ISLANDS ' PREPARED UNDER THE DIRECTION OF THE CHIEF OF ENGINEERS, U. S. ARMY BY THE INTELLIGENCE DIVISION, OFFICE OF THE ENGINEER HEADQUARTERS UNITED STATES ARMY PACIFIC ‘ ' WITH PERSONNEL OF I/ “ THE UNITED STATES GEOLOGICAL SU VEY 1958 MILITARY GEOLOGY OF TRUK ISLANDS, CAROLINE ISLANDS by John T. Stark, James E. Paseur, Richard L. Hay, Harold G. May, and Elmer D. Patterson with Section on climate by David I. Blumenstock Section on water resources by Max H. Carson DOCUMENTS DEPARTMENT NOV 10 1.96! mem1 UNIVERSITY OF CALIFORNIA Prepared under the direction of the ' Chief of Engineers, U.S. Army by the Intelligence Division, Office of the Engineer Headquarters United States Army Pacific with personnel of The United States Geological Survey 1958 Distribution List - Military Geology of Truk Islands, Caroline Chief of Engineers, Department of the Army, washington 25, D.C. (For ZI distribution and reserve) . . Commander in Chief, Pacific Commander, Naval Forces, Marianas Commander, Fifth Air Force . o O o I I o o a a Commander in Chief, United States Army, Pacific . . . . . . . Commanding General, United States Army, Ryukyus Command and IX Corps . . . Commanding General, Fleet Marine Force, Pacific . . . . . Commanding General, Air Ground Task Force, Marine Corps Air Station, Kaneohe Bay, T.H. . . . . Commanding General, Eighth United States Army . . . . . . . Commanding General, United States Army, Hawaii and 25th Infantry Division . 0 Commander in Chief, United States Air Force, Pacific . . . . . Commander in Chief, United States Pacific Fleet . . . . . Commanding Officer, United States Army Command Reconnaissance Activity, Pacific Chief, United States Navy Security Agency, Pacific . High Commissioner, Trust Territory of the Pacific Islands Engineer, United States Army, Pacific (Staff distribution and theater reserve) . islands 50 Distribution list addressees requiring additional copies of this publication should submit requisitions to: Army, Pacific. ii Engineer, United States .> .»- . H 4: Ljiy’Ltugb ' U 57;; awn: SCSEHCES meuv FOREWORD Ju1y 1958 Engineer Intelligence Study - Truk Islands, Caroline Islands This study on the Military Geology of Truk Islands, Caroline Islands, has been prepared as part of the Pacific Geological Mapping Program. This program is designed to produce information on the military geology of selected areas of the Pacific by field mapping and analysis of selected islands. This report presents general basic data on the geology, soils, water supply, vegetation. and climate of the Truk Islands. From these basic data have been interpreted engineering data on construction of roads, airfields, underground installations, and construction ma- terials. Tactical interpretations on amphibious and airborne opera- tions and cross-country movement have also been made from the basic data. This study was prepared in cooperation with the U.S. Geological Survey, Department of the Interior. (33% Brig , Engineer iii 1'73 CONTENTS Distribution List . . . . . . . . . . . . . . . . . . . Foreword . . . Introduction . Previous Investigations and Reliability of Data . . Acknowledgements . . . . . . . . . . . . . . . . . General Nature of the Area Terrain Features, by John T. Stark . . . . . . . . up, location and size . . . . . . . . . . . . . . Topography and drainage . . . . . . . . . . . \g Vegetation . . . . . . . . . . . . . . . . . . Cultural Features, by John T. Stark . . . . . . . . Villages . . . . . . . . . . . . . . . . . . . Population . . . . . . . . . . . . . . . . . . World War II military installations . . . . . History . . . . . . . . . . . . . . . . . . . Communications and access . . . . . . . . . . Climate, by David I. Blumenstock . . . . . . . . . General statement . . . . . . . . . . . . . . General climatic setting . . . . . . . . . . . Broad climatic characteristics . . . . . The seasons . . . . . . . . . . . . Dry trade-wind season (January through March) . . . . . . . . . . . . . . First rainy trade-wind season (April through June) . . . . . . . . . Doldrum season (July through October) Second rainy trade-wind season (November and December) . . . . . . . . . . Geographical variations in the climate . ASpects of climate of particular practical interest . . . . . . . . . . . . . . . Insolation and illumination . . . . . . . . . Barometric pressure . . . . . . . . . . . . . Temperature . . . . . . . . . . . . . . . . . Wind . . . . . . . . . . . . . . . . . . . . . Humidity . . . . . . . . . . . . . . . . . . . Cloudiness . . . . . . . . . . . . . . . . . . Visibility . . . . . . . . . . . . . . . . . . Rainfall . . . . . . . . . . . . . . . . . . . General characteristics . . . . . . . Annual rainfall variability . . . . . . . Geographical variations in rainfall . . . The diurnal rainfall regime . . . . . . . Rainfall frequencies and intensities . . Drought . . . . . . . . . . . . . . . . . Stoms and Squalls I O O I I I I O O O 0 I O I Topics of special interest . . . . . . . . . . References . . . . . . . . . . . . . . . . . . Oceanography and Special Geophysical Phenomena, by Ri Chard L O Hay O O I I O O I O O O O O O O O O O Page ii iii [UNI-J FSEEEE 15w4<~14 owwm H h) Tides and currents . . . . . . . Nerth Pass . . . . . . . . Northeast Pass . . . . . . Salat Pass . . . . . . . . Otta Pass . . . . . . . . . Minami-suid5 . . . . . . . Piaanu Pass . . . . . . . . Waves and surf . . . . . . . . . \ Tsunami . . . . . . . . . . . . \a Earthquakes........... Topography, by Richard L. Hay . . . . General statement . . . . . . . Volcanic islands . . . . . . . . Upland areas . . . . . . . \* Coastal lowlands . . . . . Fringing coral reefs . . . Lagoon and barrier reef . . . . Coral islands . . . . . . . . . Structures and installations . . Geology, by John T. Stark . . . . . . General statement . . . . . . . ~1Rock types . . . . . . . . . . Stratigraphy and struc ure . . . Eastern islands . . . . . . ‘4‘ MDen . . . . . . . . . Falo . . . . . . . . . Yanagi . . . . . . . . Dublon Island . . . . Eten . . . . . . . . . Fefan . . . . . . . . Param. . . . . . . . . Tarik . . . . . . . . Tsis . . . . . . . . . Uman, Tako, and Atkin Faneu . . . . . . . . Central islands . . . . . . Pyroclastic deposits . Lava flows . . . . . . Dikes . . . . . . . . Udot . . . . . . . . . Eot . . . . . . . . . Eiol . . . . . . . . Western islands . . . . . . Tol . . . . . . . . . Fala-beguets . . . . . Ulalu . . . . . . . . Reef islands . . . . . . . Lagoon deposits . . . . . . Centers of eruption . . . . . . \JWeathering . . . . . . . . . . . Age . . . . . . . . . . . . . . Physiographic development . . . Economic deposits . . . . . . . vi Soils, by James General st Introducti E. Paseur . . . . . . . . . . . at eme nt 0 I I I C I O O I O O I on C O I I O O O I C O I . O 0 Classification and genesis . . . . . . . . Soil units «Unit Unit Unit Unit Unit Unit unit Unit 1. Truk clay . . . . . . . . . General features . . . . . . . . Topography and drainage . . . . Profile descriptions . . . . . . Range in characteristics . . . . Inclusions of other soils . . . Modification of the natural soil Vegetation . . . . . . . . . . . Utilization . . . . . . . . . . 2. Truk stony clay . . . . . . General features . . . . . . . . Topography and drainage . . . . Profile descriptions . . . . . . Range in characteristics . . . . Inclusions of other soils . . Modification of the natural soil Vegetation . . . . . . . . . . . Utilization . . . . . . . . . . 3. Fefan soils . . . . . . . . General features . . . . . . . . Topography and drainage . . . . Profile descriptions . . . . . . Range in characteristics . . . . Inclusions of other soils . Modification of the natural soil Vegetation . . . . . . . . . . . Utilization . . . . . . . . . . 4. Rockland . . . . . . . . . . General features . . . . . . . . Topography and drainage . . . . Range in characteristics . . . . Modification of the natural soil Vegetation . . . . . . . . . . . Utilization . . . . . . . . . . 5. Muck and peat . . . . . . . General features . . . . . . . . Topography and drainage . . . . Profile descriptions . . . . . . Range in characteristics . . . . Inclusions of other soils . . . Mbdifications of the natural soil Vegetation . . . . . . . . . . . Utilization . . . . . . . . . . 6. Shioya loamy sands . . . . . General features . . . . . . . . Topography and drainage . . . . Profile descriptions . . . . . . Range in characteristics . . . . Vegetation . . . . . . . . . . . Utilization . . . . . . . . . . 7. Fill . . . . . . . . . . . . 8. Mangrove swamps . . . . . . vii Page General features . . . . . . . . . . . . . 106 Range in characteristics . . . . . . . . . 106 Inclusions of other soils . . . . . . . . 106 Modification of the natural soil . . . . . 106 Vegetation . . . . . . . . . . . . . . . 106 Utilization . . . . . . . . . . . . . . . 107 Water Resources, by Max H. Carson . . . . . . . . . . . . 109 General statement . . . . . . . . . . . . . . . . . 109 Introduction . . . . . . . . . . . . . . . . . . . . 109 Eastern islands . . . . . . . . . . . . . . . . . . 112 \. Mben . . . . . . . . . . . . . . . . . . . . . 112 Dublon Island . . . . . . . . . . . . . . . . . iiu Fefan . . . . . . . . . . . . . . . . . . . . . 116 Param . . . . . . . . . . . . . . . . . . . . . 117 Tarik . . . . . . . . . . . . . . . . . . . . . 117 Tsis . . . . . . . . . . . . . . . . . . . . . 117 Uman . . . . . . . . . . . . . . . . . . . . . 117 Central islands . . . . . . . . . . . . . . . . . . 117 Udot . . . . . . . . . . . . . . . . . . . . . 117 western islands . . . . . . . . . . . . . . . . . . 118 T01 . . . . . . . . . . . . . . . . . . . . . . 118 Fala—beguets . . . . . . . . . . . . . . . . . 119 Outer reef islands . . . . . . . . . . . . . . . . 119 Vegetation, by James E. Paseur . . . . . . . . . . . . . 121 General statement . . . . . . . . . . . . . . . . . 121 Description of vegetation units . . . . . . . . . . 121 Unit 1. Mangrove swamp . . . . . . . . . . . . 121 Unit 2. Strand vegetation . . . . . . . . . . 125 Unit 3. Fresh-water marshes . . . . . . . . . 125 Unit A. Fill vegetation . . . . . . . . . . . 126 Unit 5. Grassland . . . . . . . . . . . . . . 127 Unit 6. Coconut-breadfruit forest . . . . . . 128 Unit 7. Ficus-Pandanus forest . . . . . . . . 129 Tactical Aspects of Terrain Avenues of Approach, by Richard L. Hay . . . . . . . . . 131 General statement . . . . . . . . . . . . . . . . . 131 Amphibious operation conditions . . . . . . . . . . 131 Approaches and anchorages . . . . . . . . . . . 131 Landing sites . . . . . . . . . . . . . . . . . 132 Beach exits . . . . . . . . . . . . . . . . . . 135 Piers and docks . . . . . . . . . . . . . . . . 136 Canals . . . . . . . . . . . . . . . . . . . . 137 Airborne operation conditions . . . . . . . . . . . 137 General terrain characteristics . . . . . . . . 137 Parachute-drop operations . . . . . . . . . . . 138 Assault aircraft operations . . . . . . . . . . 139 Helicopter operations . . . . . . . . . . . . . 140 Discussion of units . . . . . . . . . . . . . . 1h1 Cross-Country Movement, by Richard L. Hay . . . . . . . . 1H3 General statement . . . . . . . . . . . . . . . . . 143 Vehicular movement . . . . . . . . . . . . . . . . . 1h3 Movement of foot troops . . . . . . . . . . . . . . lHS viii Page Engineering Aspects of Terrain Engineering Materials, by James E. Paseur and Har'old G I my . Q . O . . O O . C O O O C . C C O . . 1&7 General statement . . . . . . . . . . . . . . . . 1A7 Introduction . . . . . . . . . . . . . . . . . . 148 Unit 1. Hard compact lavas . . . . . . . . . . . 159 Unit 2. Hard mixed lavas . . . . . . . . . . . . 160 Unit 3. Moderately hard lava . . . . . . . . . . 161 Unit A. Hard mixed breccia and lava . . . . . . . 162 Unit 5. Mixed volcanic breccia and conglomerate . 162 Unit 6. Coral limestone . . . . . . . . . . . . 163 Unit 7. Calcareous beach sands . . . . . . . . . 16h Unit 8. Deep stony clays . . . . . . . . . . . . 16h Unit 9. Deep residual clays . . . . . . . . . . . 165 \“Unit 10. Thin clays on hard compact lavas . . . . 166 Unit 11. Thin clays on hard mixed lavas . . . . . 167 Unit 12. Thin clays on moderately hard lava . . . 167 Unit 13. Thin limonitic gravelly clay on hard compact lavas . . . . . . . . . . . . 167 Unit 1h. Thin limonitic gravelly clay on hard mixed lavas . . . . . . . . . . . . . 168 Unit 15. Mangrove—swamp deposits . . . . . . . . 168 Unit 16. Marshland deposits . . . . . . . . . . . 169 Unit 17. Fill . . . . . . . . . . . . . . . . . . 169 Unit 18. Coral boulders, cobbles, and gravel . . 169 Pits and Quarries, by Harold G. May . . . . . . . . . . 171 Roads and Airfields, by Harold G. May . . . . . . . . . 175 General statement . . . . . . . . . . . . . . . . 175 Japanese roads . . . . . . . . . . . . . . . . . 176 Airfields . . . . . . . . . . . . . . . . . . . . 176 Unit 1. Dry lowlands . . . . . . . . . . . . . . 177 Road construction . . . . . . . . . . . . . . 177 Airbase construction . . . . . . . . . . . . 178 Heliport construction . . . . . . . . . . . . 178 Unit 2. Upland flats . . . . . . . . . . . . . . 178 Road construction . . . . . . . . . . . . . . 178 Airbase construction . . . . . . . . . . . . 178 Heliport construction . . . . . . . . . . . . 178 Unit 3. Moderate to steep uplands . . . . . . . . 179 Road construction . . . . . . . . . . . . . 179 Airbase construction . . . . . . . . . . . . 179 Heliport construction . . . . . . . . . . . . 179 Unit A. Steep to precipitous uplands . . . . . . 179 Road construction . . . . . . . . . . . . . 179 Airbase construction . . . . . . . . . . . . 179 Heliport construction . . . . . . . . . . . . 179 Unit 5. Wet lowlands . . . . . . . . . . . . . . 180 Road construction . . . . . . . . . . . . . . 180 Airbase construction . . . . . . . . . . . . 180 Heliport construction . . . . . . . . . . . . 180 Underground Installations, by Elmer D. Patterson . . . 181 General statement . . . . . . . . . . . . . . . . 181 Classification . . . . . . . . . . . . . . . . . 181 ix Underground installations units . . . . . . . . . . Unit Unit Unit Unit Unit Unit Unit Bunker-type installations . . . . . . . . . . . . . Tunnel—type installations . . . . . . . . . . . . . Existing caves . . . . . . . . . . . . . . . . Problems of tunneling operations . . . . . . . Special problems . . . . . . . . . . . . . . . . . Access . . . . . . . . . . . . . . . . . . . Concealment . . . . . . . . . . . . . . . . . Unit areal relationships . . . . . . . . . . . . . Eastern islands . . . . . . . . . . . . . . . Moen . . . . . . . . . . . . . . . . . . Falo . . . . . . . . . . . . . . . . . . Yanagi . . . . . . . . . . . . . . . . . Dublon Island . . . . . . . . . . . . . Eten . . . . . . . . . . . . . . . . . . Fefan . . . . . . . . . . . . . . . . . . Param . . . . . . . . . . . . . . . . . . Tarik . . . . . . . . . . . . . . . . . . Tsis . . . . . . . . . . . . . . . . . . Uman . . . . . . . . . . . . . . . . . . Faneu . . . . . . . . . . . . . . . . . . Central islands . . . . . . . . . . . . . . . Udot . . . . . . . . . . . . . . . . . . Eot . . . . . . . . . . . . . . . . . . Eiol . . . . . . . . . . . . . . . . . . Western islands . . . . . . . . . . . . . . . Tol . . . . . . . . . . . . . . . . . . Fala-beguets . . . . . . . . . . . . . . Ulalu . . . . . . . . . . . . . . . . . . Reef islands . . . . . . . . . . . . . . . . . w]0\\J‘I-F-‘UUI\DI‘-‘ Glossary of Terms . . . . . . . . . . . . . . . . . . . . . Bibliogaphy I O o n I o I C c O n o t o I o O o 0 I I O I 0 [DH \0 004mm: w Tables Illumination and insolation, Truk Islands . . . . . . . Monthly mean and extreme air pressure, Dublon Island, Truk Islands . . . . . . . . . . . . . . . . . . . . . Mean air pressure at h-hour intervals for four selected months, Dublon Island, Truk Islands . . . . . . . . . Mean and extreme temperatures, Iruk Islands . . . . . . Mean relative humidity, Mben, Truk Islands . . . . . . . Sky cover and sunshine, Dublon Island, Truk Islands . . Monthly and annual rainfall, Truk Islands . . . . . . . Mean number of days with rainfall of specified amounts, Truk Islands . . . . . . . . . . . . . . . . . . . . . Greatest 2h-hour, 6-hour, and 4-hour rainfall by months, Truk Islands . . . . . . . . . . . . . . . . . . . . . Page 183 183 183 18h 181+ 18h 18h 181+ 184 185 185 185 186 186 186 186 186 186 188 188 188 189 189 190 190 190 190 190 191 191 191 191 191 191 192 192 192 195 203 11+ 16 16 17 l7 25 32 31+ Page 10 Mean number of days with thunderstorms, Truk Islands . 3h 11 Areas and elevations of the Iruk Islands . . . . . . AL 12 Chemical analyses of soil samples, Truk Islands . . . 83 13 Distribution of the soils units, Truk Islands . . . . 85 in Soils of the Truk Islands . . . . . . . . . . . . . . 89 15 Chlorides of ground-water samples, Truk Islands . . . 119 16 Vegetation of the Truk Islands . . . . . . . . . . . . 122 17 Engineering materials: field conditions affecting operations, Truk Islands . . . . . . . . . . . .-. . 1H9 18 Areal distribution of engineering materials units, ITuk Islands . . . . . . . . . . . . . . . . . . . 151 19 Engineering test data, Truk Islands . . . . . . . . . 153 20 Soil mechanics test data, Truk Islands . . . . . . . . 155 21 Engineering materials suitability, Truk Islands . . . 157 22 Quarries, Truk Islands . . . . . . . . . . . . . . . 173 23 Underground installations units, Truk Islands . . . . 182 Figures 1 Truk Islands and index map . . . . . . . . . . . . . 4 2 Wind roses for Dublon Island, Truk Islands . . . . . . 19 3 Monthly rainfall variability, Truk Islands . . . . . . 2% AA Comparative rainfall totals for five stations, Truk Islands, 1933 . . . . . . . . . . . . . . . . . 29 B Comparative rainfall totals for five stations, Truk Islands, 1934 . . . . . . . . . . . . . . . . . 3o 5 Diurnal rainfall frequencies, Moen, Truk Islands 31 6 Estimated rainfall intensity—duration-frequency curves, Truk Islands . . . . . . . . . . . . . . . . . . . 35 7 Geologic section, Chukuwdn, Meen . . . . . . . . . . . 56 8 Geologic section, Witipon, Moen . . . . . . . . . 56 9 Geologic section, Mount Teroken (Chukumong), Moen . . 57 10 Geologic section, Winifourer; Mben . . . . . . . . . . 58 11 Geologic section, Foukenau, Dublon Island . . . . . . 61 12 Geologic section, Mount Uinku, Eten . . . . . . . . . 61 13 Geologic section, Mount Iron, Fefan . . . . . . . . . 6h 1h Geologic section, Mount TUmuital, T01 . . . . . . . . 69 15 Probable centers of eruptions, Truk Islands . . . . . . 76 16 Photo index map, Truk Islands . . . . . . . . . . . . . 207 Maps 1:25,000 scale (in pockets) Geology and Water Resources Maps, Truk Islands . . Geology, Engineering Materials, and Water Resources Maps of Coral Islands, Truk Islands . . . . . . . Soils Maps, Truk Islands . . . . . . . . . . . . . Vegetation Maps, Truk Islands . . . . . . . J . . . Avenues of Approach and Suitability for Cross— Country Mbvement Maps, Truk Islands . . . . . . . Map numbers . 1 through 7 8 9 through 15 16 through 22 23 through 29 Engineering Materials Maps, Truk Islands . . . . . . 30 through 36 Suitability for Road and Airfield Construction Maps, Truk Islands . . . . . . . . . . . . . . . . . . . 37 through #3 Suitability for Underground Installations Maps, Truk Islands . . . . . . . . . . . . . . . . . . . uh through 50 xi Photo Plates Following Page Plate 1. Panorama of abandoned airfield, Eten . . . . . . Ah 2. Panorama of abandoned airfield, Param . . . . . an 3. Panorama looking toward Witipdn mountain, Moen . MA A A. Mount Tolomen, Dublon Island . . . . . . . . . Ah B. Summit plateau, Witipdn mountain, Moen 5 A. Mount Tumuital, Tol . . . . . . . . . . . . . . an B. Basalt cliff, Uman 6 A. Rock surface of benchland, Uman . . . . . . . . #6 B. Nbrthern Fefan from the sea 7 A. Mangrove swamp, Tbl . . . . . . . . . . . . . . #6 B. Airphoto of Falo 8 A. PiS islarld D I C . C C C C . C . D O . I C I O C 1+8 B. Beach rock on Onamue 9 A. Dense forest on South Island, Northeast Islands. #8 B. Japanese pillbox, Dublon Island 10 A. Causeway and bridge in mangrove swamp, Fefan . . #8 B. Causeway crossing Nemonon bay, Dublon Island ll A. Village on Ulalu . . . . . . . . . . . . . . . . #8 B. Native weaving thatch, Ulalu 12 A. Copra-drying shed on Tbl . . . . . . . . . . . . #8 B. Native house on northeast T01 13. Quarry in andesite, Moen . . . . . . . . . . . . 58 l#. Breccia boulders, south Udot . . . . . . . . . . 66 15 A. Nepheline basalt mesa (Mount Unimor), T01 - , , 70 B. Melilite-nepheline basalt plateau, T01 16 A. Weathered pinnacles on nepheline basalt, Tol . . 72 B. Ocean-facing beach, Edat .17 A.- OceaIl-faCing beaCh, Uijec o o o o n n u o o I c 72 B. Sand spit, Iamoil 18 A. Seawax'd beaCh, Fanan I I I O I O I I O D I l I O 72 B. Closeup of coral cobbles and boulders, Fanan 19 A. Surface of fringing reef, Uijec . . . . . . . . 72 B. Niggerheads between Tora and Ruac 20 A. Beach rock, Ollan . . . . . . . . . . . . . . . 76 B. Beach rock, Uijec xii Following page 21 A I We athered lava, Moen I I I I I I I I I I I I I I I I 76 B. Exfoliation weathering of boulder on northeast Eten 22 A. Soil profile in Truk clay, Moen . . . . . . . . . . 92 // B. Closeup of eroded surface of Truk clay, Moen 23 A. Roadcut exposure of Truk stony clay, Moen . . . . . 96-/ B. Roadcut exposure of Truk stony clay, Moen 24. Soil profile, Witipdn mountain, Mben . . . . . . . 96 ,/ 25 A. Soil profile of Fefan soils, Sopuk peninsula, Moen . 98 /’ B. Ferruginous concretions at surface of Fefan soils, Ulalu 26. Bomb crater in Fefan soils, Ulalu . . . . . . . . . 98 27. Boulder talus, Moen . . . . . . . . . . . . . . . . lOO"‘ 28. Causeway through mangrove swamp, Moen . . . . . . . lO6<’ 29. Mangrove swamp, Mben . . . . . . . . . . . . . . . . 12h /” 30 A. Swamp taro patch, Udot . . . . . . . . . . . . . . . 124 B. Closeup of swamp taro, Udot 31 A. Vigna marina on £111, Dublon Island . . . . . . . . 126 B. Phragmites karka on fill, Dublon Island 32 A. Vigna marina and coconut trees, Dublon Island . . . 126 B. Vegetation on marshy fill, Dublon Island 33 A. Closeup of Merremia peltata, Moen . . . . . . . . . I26 —’ B. Grassland vegetation on MDen 3A A. Upland vegetation, Uman . . . . . . . . . . . . . . 126 B. Grassland vegetation, Uman 35. Closeup of Scleria sp., Moen . . . . . . . . . . . . 126" 36 A3 CO 0011th 'breadfruit forest J TO]. 0 o n u o I o o o o a 128 B. Coconut-breadfruit forest, Udot 37 A. Clinostigma carolinesis on Witipdn mountain, Moen . 128 B. Banyan tree on Mount Uroras,_Uman 38 A. Beach I, Dublon Island . . . . . . . . . . . . . . 132 B. Beach 2, Dublon Island 39 A. Western part of Beach 3, Dublon Island . . . . . . . 132 B. Eastern part of Beach 3, Dublon Island 1+0 I Beach 7, Moen I I I I I I I I I I I I I I I I I I I 132 41 AI Beach 8’ Moen I I I I I I I I I I I I I I I I I I I 132 B. Northeastern part of Beach 9, Moen xiii £12 A. B. 113 A. B. AM A. B. #5 A. B. 46 A. 47 A. B. 1+8 A. B. 1+9. 50 A. BI 51 A. BI 52 A. 53 A- B. 51+. 55 A- B. 56 A. 57- 58 A. 59 A- 60 A. B. Southwestern part of Beach 9, Moen . . . . . . . . . Beach 10, Moen American pier, west Moen . . . . . . . . . . . . . . American pier, west Mben Fuel-oil pier, south Dublon Island . . . . . . . . . Fuel-oil pier, south Dublon Island Fuel-oil pier, south Dublon Island . . . . . . . . . Pier at former naval base, Dublon Island Pier, south Dublon Island . . . . . . . . . . . . . Pier, south Dublon Island Pier , Ulalu I I I I I I I I I I I I I I I I I I I I Pier, Ulalu Pier, east man I I I I I I I O I I I I I I I I I I Seaward end of pier, east Uman Pier, west Param . . . . . . . . . . . . . . . . . Ne tutu c haunne l , To 1 I I I I I I I I I I I I I I I I Netutu channel, Tol Uitonap mountain, Udot . . . . . . . . . . . . . . Exposed bedrock, Udot Concrete—surfaced seaplane taxiway, south Dublon Island- I I I I I I I I I I I I I I I I I I I I I Marshy fill, southeast Dublon Island Former airfield, Param . . . . . . . . . . . . . Dense Phragmites karka on marsh adjacent former airfield, Param Netutu chme l , TO]- . 0 o I I 0 I O 0 I O I O I O I Trachyte exposure, WitipSn mountain, Moen . . . . . Flattish upland area on southeast Uman Dense grass and vines near summit of Winifourer mountain, Moen . . . . . . . . . . . . Grassland vegetation, south uman Coconut-breadfruit forest on northwest Tol . . . . . Former Japanese path, Ulalu . . . . . . . . . . . . Former Japanese road, east Ulalu Former Japanese coastal road, west Tsis . . . . . . Former Japanese road, southeast Dublon Island Former Japanese road on northeastern Dublon Island . Footbridge in coastal road, southeast Dublon Island xiv Following page 132 136 136 136 136 136 136 136 136 138 138 138 1110 1111+ 1th 1111+ 176 176 _ 176 61 A. 66 A. B. Following page Former main Japanese coastal road, south Dublon Island 176 Coastal road, east Uman American coastal road, west Mben . . . . . . . . . . 176 Young coconut trees on the northeast end of abandoned airfield, Param . . . . . . . . . . . . 176 Former Japanese airstrip, Param Breached seawall, northeast end of former airfield, Par‘am O I I I l O I C C I O O I I O O I C I O I O 176 Unfinished extension of former airfield, Param Japanese gun, covered, Tanaachau mountain, Moen . . 186 Japanese gun, covered, Tanaachau mountain, Moen . . 186 Japanese gun, Witipdn mountain, Moen MILITARY GEOLOGY OF TRUK ISLANDS, CAROLINE ISLANDS INTRODUCTION Military Geology of Truk Islands, Caroline Islands, is one of a series of military geology reports resulting from detailed geologic and soil surveys conducted under the Pacific Geological Mapping Program which was established as a part of the Corps of Engineers Post Hostili- ties Mapping Program. Other reports in this series are based on simi- lar surveys of Okinawa-jflna, Ishigaki-shima, and Miyako-jima of the Ryfikyfi-retto; Saipan, Tinian, Guam, and Pagan of the Mariana Islands; and Palau Islands and Yap of the Caroline Islands. The purpose of these surveys is twofold: first to collect scien- tific infonmation on the rocks and soils of Pacific islands and, second, to publish it in a form usable by the U. S. Armed Forces and civil ad- ministrators working in these islands. Basic data, though somewhat specialized, are included in the report to enable reinterpretation for presently unforeseen needs. The Military Geology of Truk Islands presents basic geologic and soil data both for base development and for engineer intelligence, and presents militarily important facts about the general nature of the terrain. These are presented as a preface to the more detailed cover- age of the tactical and engineering aspects of the terrain. A field survey of former Japanese defenses on Truk was made in l9h6: there is no attempt here to duplicate this excellent report, which is as perti- nent now as when it was published (U. S. Navy Department, CINCPAC— CINCPOA, 191.6) . The first section presents factual data on terrain, culture, cli- mate, oceanography, topography, geology, soils, surface water, and vegetation. The text is illustrated with photographs, tabular data, diagrams, and maps (maps 1 through 22). The second section, Tactical Aspects of Terrain, has chapters on amphibious and airborne operations and cross-country movement. Photo- graphs and one set of maps (maps 23 through 29) illustrate this section. The third section, Engineering Aspects of Terrain, contains infor- mation on construction materials, road and airfield construction, and underground installations. Tables, photographs, and maps (maps 30 through 50) illustrate these chapters. A bibliography of all references and a glossary of terms are given at the end of the report. The Truk field party, consisting of JOhn T. Stark, party chief, Richard L. Hay, Harold G. May, Elmer D. Patterson (U.S.G.S. geologists); James E. Paseur (U.S.G.S. soil scientist), and Eula B. Paseur (U.S.G.S. administrative assistant), worked in the Truk Islands from early Octo- ber l95h until June 1955. Max H. Carson (U.S.G.S. hydrographer) was with the party from 2M January to 18 March 1955. David I. Blumenstock, Climatologist of the U. S. Weather Bureau, Department of Commerce, though not a member of the field party, is the author of the chapter Climate. All photos are by members of the field party. Figure 16, photo-index map, shows location and direction of View for the photos in this report. Approximately 6 months were devoted to island traverses, collec- tion of samples, and field mapping, and 3 months to preparation of maps and text, microscopic study of rock thin sections, and analysis of the laboratory tests on rock and soil Samples. Previous Investigations and Reliability of Data Reports on the Truk Islands by Japanese scientists, published and in manuscript, have been concerned chiefly with the studies of coral reefs and vegetation with only brief summaries of the geology. Some of these are available in translations by the Engineer Intelligence Division, U. S. Army Forces, Far East. More helpful than these gener- alized accounts of the geology are the field notes of Josiah Bridge, who was in the Truk Islands from 13 to 16 August l9h6, and his section on Truk in Mineral Resources of Micronesia (unpublished references, Bridge, 19162.). A detailed account of the peoples and culture of the Truk Islands is given in Truk: Man in Paradise (Gladwin and Sarason, 1953). Field Survey of Japanese Defenses of Truk (U.S. Navy Department, CINCPAC-CINCPOA, l9h6) has proved especially useful with its numerous maps, diagrams, and photographs. The base for all maps at l:25,000 scale in this report are sheets of AMS Series W856. Complete coverage of the Truk Islands is available on 27 sheets. In this report the seven sheets covering the larger more important islands in the lagoon are used. Coverage of other signifi- cant islands in the lagoon or on the reef not shown on these seven sheets is obtained by special insert maps or mosaic maps of individual islands. A few small islands have not been covered by maps in this report, and reference to the complete 27-sheet AMS Series W856 should be made. Acknowledgements Acknowledgements are made to Ernest W. Bishop, geologist-in—charge of the Guam Field Office of the U. S. Geological Survey for aid in preparation and transhipment of materiel from Guam to Truk. Special appreciation is expressed to Willard C. Muller, District Administrator for the Truk Islands and to all members of the Trust Territory adminis- tration and affiliated agencies on the islands for their interest and cordial cooperation in all phases of the work. Considerable logistical support for the field party was provided by the 63l9th Air Base Wing, U. S. Air Forces on Guam. Acknowledgements are due the Base Develop- ment Officer, Commander Naval Forces Marianas, for the soil and rock engineering tests provided by the Base Development Test Laboratory under the direction of Charles Shirley. Thin section of rocks were prepared by Mr. K. S. Iwamoto, Tokyo, Japan, and chemical analyses by Japan Inspection Company, Ltd., Tokyo, Japan. Much information and assist- ance in preparing the section on Climate was given by Mr. E. J. Saltsman of the U. S. Weather Bureau, Washington, D. C. and the staff of the Japan Meteorological Agency, Tokyo. I I I T I , I I , L . I, 25' 30' 35' I5I°4o’ 45 50’ 55 I52 00 r a. « 05 North Pass ,. 2 ‘?°' '°°' '?°’ '53:» mgshi Pass (Ushish/ma Pass) w’ ,1 w , ~ Onao W33 be 'He Pass a " I—4o PIs Tonelik Ushi E ” . . _: j; I; 4° w, Alonenkobwe Lap Tara Pass (TorashIma Pass) ‘ ‘ LOmOII TOFO [EI'GI‘II‘ fir Ruac I’ QFalalu Holop I 0 , f / A Mlduay 41/4," L'll'l'I' I; Marcus I - .‘ ISL‘ “1% .Woklo , MS /"u:W/. O -20' § _ ofifim "m" Norfheasf Islands \ w/ x c __ 35‘ -v/.:;Z.’,‘.'"'"° Q93 ‘7 4, m oFanueIa 35'— GILa-Enr (92:53 WW “ ' EM ‘ Infing‘AiA " Liball We ' " ISEA WmLJA ".51!“ F @FOI’IUCI Is- I. "\ '1 I . |; .Is- OIOS " 2° 6° °° °' 5‘” €33 g 9 {$3, eFanamar Quoi ‘ Bosislslond EIYawaIa-shima Mor NorfheasfPass o ' —7°30' Fan oSand Island 7 3° ‘ Scheibenlsland -A {6? go a m fiOsakura Taua/ap Pass I “Allei Reef -Small Island Fa/ea/lej Pass ‘ IaBush Island . . —25l Lelom Reef 3 ‘3' I 0 @Herif 25 — Faleosicz- mum,” ' Lelom Pass q, 1~ Yanagi FanufanReef ~ 3. E '2- n I , UDOT ° ¢%DUBLON ISLAND Pafa Peninsula ‘ " TOL up ; . @ aFanamu Piaanu Pass %3 FALA—BEGUETS Eiol 4@Param . diam Onamue" ‘ _ I Tarik "' 2d~ 20 FEFAN 90”” . Pisinmelikomo - lySInzhmo ‘ ~ u w UMAN sMeryberyb PISCII’ ‘3; sFanurmoI @Tsis Bernard afisobu Reef @Tonuamu eFaleaI Alanseiru Islands b Tako Afkin Fananan e. g @ aOnnoram °fiaLeneperer Reef '9 OZOIUK Reef WFaneu , mPueilap Reef 9 Pagura Reef CO , —'5 233T R f Paguerion Reef zen Feinif '5‘ . amar r ee . ' In TRUK ISLANDS o'lonW. I “W “9:” 3"” “‘ “I“? 3““ Emma Nona Falasn U/ifauro Pass limp/s P055 Neurui Pass AND INDEX MAP Fanusamoz Pass a ' _ Panes :PIZIOD Pass Aua/ap Pass q. Fanan Minami-suido’ wleasioz Reef . . o 5 Iosmim miles ‘gfl . Ud'doha “”5"” P055 ‘ "6 [WWII Il I II III II I II I I I II I II J v xiv Ud’da” P055 '°‘ 0 5 IO I5 Kilometers 0H0 Pass OIIO UIIec Nenna F’CISSI ‘ Mesegon 25’ 30' 35’ I5I°4d 45’ 50' (”W/90’ P055 55' I52°oo' 015' l I I I I I l I GENERAL NATURE OF THE AREA EEEEEEELEEEEEEEE by John T. Stark Location and size The Truk Islands, the largest group of islands in the central Caroline Islands, are located between 7°08' and 7°hl' north latitudes and 151°26' and 152°02' east longitudes. They lie 2,089 statute miles southeast of T6ky5, 3,029 statute miles southwest of Honolulu, and 636 statute miles southeast of Guam (fig. 1). The Truk Islands are surrounded by a 125-mile barrier reef roughly triangular in outline, 38 miles east-west and 33 miles north-south. The total land area, as measured by planimeter, is 35 square miles and the water area of the lagoon is approximately 820 square miles. There are 21 passes in the barrier reef (U.S. Navy Department, Hydrographic Office, lthb), seven of which are navigable by AK-class vessels. Topography and drainage There are 19 high volcanic islands within the Truk Lagoon. The two small islands of Atkin and Tako, on the fringing reef just off the south coast of Uman, are considered a part of Uman. The volcanic is- lands may be separated into an eastern group consisting of Moen, Falo, Dublon Island, Eten, Yanagi, Fefan, Param, Tarik, Tsis, Uman, and Faneu; a central group consisting of Udot, Eot, and E101; and a western group consisting of Tol, Fala-beguets, and Ulalu. The high volcanic islands range in size from T01 and Moen, 5 by 2 miles and h by 3 miles respectively, to E101 and Faneu, each less than a quarter of a mile in greatest width. The highest elevation is Mbunt Tumuital on Tol at l,h53 feet (hh3 meters) above sea level; Mbunt Tolomen on Dublon Island and Mbunt Teroken (Chukumong) on Mben are both over 1,100 feet. Other prominent peaks, rising to nearly 1,000 feet, are Mount Iron on Fefan and Mount Uroras on uman. In general slopes average more than 30 percent and the upper slopes are commonly greater than 60 percent. Within the lagoon, in addition to the volcanic islands, are 2h low reef islands. 0n the barrier reef are #1 low islands. NOne are more than a quarter of a mile wide. The longest, Mbsegon, on the southeast part of the barrier reef, is slightly more than 1.5 miles long. The surface materials of the islands within the lagoon and on the barrier reef are mostly calcareous sand, gravel, and cobbles with small amounts of indurated reef rock exposed at the strand line. Elevations on a few of these islands are as much as 8 feet but most of the low islands rise to only 5 to 6 feet above sea level. Seaward beaches are commonly strewn with coral rubble and boulders in contrast to the sand and fine gravel on beaches on the lagoonal side. Fringing reef flats of various widths surround most of the high and the low islands. The high volcanic islands are drained by many small streams during the rainy season, but only a few streams persist throughout the dry months. Many of the low reef islands of the barrier reef have central depressions containing swamps from which small amounts of potable water may be recovered. Vegetation Vegetation on the high volcanic islands is commonly more luxuriant than on the low reef islands. The upper slopes of such mountains as Mount Tumuital on 'I‘ol, Mount Teroken (Chukumong) on Moen, and Mount Tolomen on Dublon Island are covered with dense forests. These forests were originally more extensive, but have had to give way on the lower and middle slopes to breadfruit and coconut groves. A large percentage of the coconut and breadfruit groves, as well as additional forest areas, were cleared during the war because of the need for greatly increased food production as well as for lumber. These areas are now overgrown with grasses. Most of the low islands are covered with for- ests, mainly coconut palm, Pandanus, and breadfruit trees. Cultural Features by John T. Stark Villages The smallest political unit on Truk is the aif'which is a group of families. Aifs are arranged into villages. Each inhabited island has one or more villages. Prior to the coming of Europeans, the villages on the high islands were scattered both along the shores and on the sides of the mountains for protection during civil wars. With the ad- vent of Europeans and the abolition of such wars, the mountainside vil- lages were moved down nearer the water. During the bombardment by the Allied task force, the villages were moved to sheltered spots on the sides of mountains. Since the war, most of the villages have again been moved down to the shore. The villages consist of one or two rows of scattered houses along coastal roads. The houses are generally flimsy structures of boards or strips of corrugated tin with walls com- monly only part way to the roof. Coconut and ivory-nut fronds are used for thatching. In villages, house floors are often built 2 or 3 feet above the ground. Woven mats are sometimes used for walls. Isolated houses in the jungle and on the hillsides commonly have dirt or sand floors. On the larger islands, especially Dublon Island, there are several more elaborate structures built by the Japanese, generally of wood but a few have concrete walls. POpulation In March 1955 the Micronesian population of the Truk Islands was 10,295 with the following distribution: Eastern islands Central islands Mben 2,256 Udot 538 Dublon Island 1,342 Eot 172 Tsis lh6 Total 710 Uman 1,028 Fefan 1,299 Western islands Param 135 Tol 2,753 Total 6,206 Ulalu 2&0 Fala—beguets 212 Barrier-reef islands Total 3,205 Pis 174 Total 17E World War II military installations . An excellent short history of the military development on the Truk Islands is given in Field Survey of Japanese Defenses on Truk from which the following excerpts are taken. "Prior to 15 November, lgho, (the date of the organization of the 4th Defense Unit on Dublon) Truk was used chiefly as an anchorage for the hth Fleet which had been organized in November, 1939. The hth Defense Unit was originally a part of the 5th Base Unit having headquarters on Saipan, and it had about 850 personnel. However, in Nbvember, l9h2, the Defense Unit became the hlst Naval Guard Force, and was still in existence at the end of the war. ”After December, l9hl, there was a period of continuous offensive action and Truk was used principally as a fleet base - the fleet being engaged in attacks in the Solomons and Marshalls areas. As the advance of the Americans in the Solomons became more and more successful, Truk was used as a staging area for airplanes which were to be transhipped into a more active area. After the American task force raid of 17-18 February, 19th, the main force of the Japanese fleet left Truk. "Truk was divided into five defense districts - Moen, Dublon, Fefan, uman, and the Western defense district with Head- quarters on Tol Island. I O O O O O C I I O "The Army units on Truk - the 52d Division, the 9th Independent Engineer Regiment and the Slst Independent Mixed Brigade - had the mission of defending Truk against the Anglo—American forces by joint action with the hth Fleet and air forces. They emphasized the following: anti-tank warfare, wellemined waters and beach obsta- cles, strong and persistent delaying actions, strong positions among rocky cliffs, and steps to make Truk self-suffi- cient in food. "In July, l9hA, the mounted guns on some of the small islets of the reefs were removed to the main islands inside the atoll for the following reasons: (1), to place the batteries in caves, rather than in the open so as to gain more protection from bombardment and bombing; (2), to lay stress on the attack of ships which might manage to get inside the atoll, and to gain mutual support between batteries; (3), to protect the main islands as long as possible. "Wire was strung between buoys on the surface at west Moen and north Dublon. This was done in front of possible landing points and the aim was to forestall any landing attempt.” (U.s. Navy Department, CINCPAC- CINCPOA, 191.6) Total Japanese strength, at its height in June l9h5, was as follows. Civilian Officers Enlisted personnel Total Army 7&1 13,558 - 1h,299 Navy #19 9,h22 iuzeeo 2hzo61 Tbtals 1,160 22,980 1h,220 38,360 History The following is a brief history of the Trukese based on Truk: Man in Paradise (Gladwin and Sarason, 1953). The first recorded visit of Europeans to Truk was by a Spaniard, Alonso de Arellano, in 1565. It was not until early in the 19th centu- ry however, that ships of various nationalities began to enter the lagoon in sufficient numbers to be of any consequence. Dumont d'Urville, a Frenchman, explored the islands rather thoroughly, but fol— lowing a misunderstanding the natives were fired upon and d'Urville escaped with his two small ships. As a consequence, when an English- man, Andrew Cheyne, visited Truk 6 years later he was attacked by an overwhelming force and retired with several casualties. He made it widely known that the Trukese were dangerous and treacherous; conse- quently during the short—lived whaling boom, which was over about 1860, there were far fewer contacts between Whalers and Trukese than those which created such havoc on Ponape and Kusaie. During Spanish rule (1886 to 1899) the nearest administrative center was on Ponape, and Truk was left alone, due largely to the war- like reputation of the people. Traders visited the islands from time to time. Some stayed to intermarry with the islanders and a few of their descendants remain today. At first their contributions were pri- marily the introduction of tools. Later the hundreds of guns intro- duced by the traders increased the violence of interisland and clan warfare which had characterized the islands. The Spanish, following the Spanish-American War, sold the Mariana and Caroline Islands to Germany which sent an expedition to Truk in 1903. Somewhat surprisingly, the people obeyed quietly the German order to turn in their guns and stop internal warfare. FOur hundred and thirty guns were surrendered. The few attempts to continue the wars were suppressed by imprisoning leaders on Ponape. To the present day the acceptance of a foreign administration preserving law and order remains throughout the islands. At the outbreak of WOrld War I Japan occupied German territory in the Caroline, northern Mariana, and Marshall Islands. At the peace conference after the war the Japanese claims were recognized, and the mandate was confirmed by the League of Nations in 1920. The United States, however, did not agree to the mandate until the washington Conference in 1922. Economic developments under the Japanese adminis- tration included the establishment of large fishing fleets and refriger- ation and drying plants for fish, the planting of trochus beds (trochus being the shellfish most commonly used for making buttons), the culti- vation of manioc (tapioca), and other less successful ventures such as the introduction of pearl oysters and sponges. Under the Japanese the steps to a money economy and dependence upon some imported goods were carried far beyond the German beginning. The fortification of Truk as a bastion for the Japanese in World War II proved disastrously in- adequate. The Allied air strike against Truk in l9#h and the blockade which followed destroyed the fruits of the Japanese efforts at economic development, and the necessity of supporting some 35,000 foreigners in addition to the almost 10,000 Trukese caused a serious depletion of island resources. Under the Japanese and American administrations, the relatively simple native organization gradually became topheavy and uncontrollable. Following economic crises, the Americans eliminated the existing hier- archy and introducted a simpler system with only a single chief over each island, large or small. Communications and access The Trust Ibrritory maintains a radio station on Moen which is open for public correspondence. It is one of five major stations in the Trust Territory districts serving centers of population in outlying areas. Point-to-point contact is available with Guam, ships, planes, and interdistrict and intradistrict areas. A Transocean Airlines plane from Guam services the districts of Ponape, Majuro, and Truk once a week. The plane usually makes a first stop on Truk on the way out to and again on the return flight from Guam. Ships of the Pacific Micronesian Line, on a flexible schedule, stop at Truk about once every 2 months. 10 Climate by David I . Blumenstock General statement The 'Jlruk Islands are warm and humid throughout the year. Average monthly temperatures cover a range of only 1°, fran 80.3° to 81.3° Fahrenheit (F.). 'l'ne usual daily temperature range is 10°, fran the middle seventies at night to the middle eighties in midaf‘ternoon. However, extremes of 69° and 9h° F. have been experienced. the rela- tive humidity ranges from around 55 to 100 percent, with usual values in excess of 75 percent. Cloudiness is high in all months, but the cloud cover is virtually never so dense and extensive that an approach- ing aircraft cannot safely descend to within sight of the water and the islands. Ellie average annual rainfall on the islands is about 160 inches, with somewhat lesser amounts in west-coast locations on the high is- lands and somewhat greater amounts on east-facing mountain slopes. However, the annual rainfall has varied from less than 100 to over 200 inches, and there is equally marked variability in monthly rainfall amounts. Winds of over 20 miles per hour (m.p.h.) are rare. There are very occasional tropical storms, but these are mild compared with the true typhoons of the far western Pacific Ocean. In contrast, local squalls are moderately frequent, especially from July through October. Illhe four seasons and their chief characteristics as regards wind and rain are as follows: (1) Dry trade-wind season (January-Larch) - Winds, often 15 to 20 m.p.h. are dominantly from the northeast. Month- lyrainfall is usually6to9 inches, with 2to lIkweelts of droughtto be expected, especially in February. (2) First rainy trade-wind season (April-June) - Winds are seldom over 15 m.p.h., usually has easterly directions. Rainfall averages over 12 inches per month with the great- est rainfall variability in April. (3) Doldrum season (July-October) - Winds are light and variable with frequent calms. Rainfall averages over 12 inches per month. (h) Second rainy trade-wind season (Novem- ber-December) - Winds are chiefly easterly at speeds that seldom exceed 15 m.p.h. Rainfall averages over 12 inches per month. General climatic setting Broad climatic characteristics: Like all oceanic islands that lie deep within the tropics and are far removed from the continental land masses, the Truk Islands are warm and humid throughout the year. In all months the afternoons are warm, with temperatures in the eighties or, rarely, in the very low nineties. In contrast, the nights bring temperatures that seem refreshingly cool, tauperatures that are often in the low seventies and sometimes even the high sixties. Since the air in which the islands are imersed must always come from over warm tropical waters, the humidity is high both day and night, with the values typically ranging from a low of between 70 and 85 percent in themthoftheafternoontoahighofbetweenBOand95percentin the cooler hours before dawn. Cloudy sides prevail at all times of the year, but it is unusual to have days that are canpletely overcast and there is often considerable variation in cloud conditions frun one day to another. In contrast with the unifomity of temperature and humidity, the wind and rainfall conditions are highly variable at Truk from year to year, season to season, and even from one day to the next. High winds, blowing steadily at speeds in excess of 20 m.p.h. , are rarely experi- enced; but from November through June , when the trade winds predominate, there are often sustained periods with fresh easterly winds and these create many local wind effects upon the high islands of the group. Winds of under 5 m.p.h. occur often even in the trade-wind months, but are most frequent by far during July through October, when light varia- ble winds and frequent calms are the rule. As for the rainfall of the Truk Islands, the average monthly and annual values obscure the very significant facts that the rainfall in any one year may be as little as 100 inches or as much as 200 inches and that even during the normal 9-month rainy period, which extends from April through December, the total rainfall in any one month may vary by a factor of 300 percent from one year to the next. In the most extreme instance, that of April, the monthly rainfall has ranged from under it inches to over 1&0 inches. In any one of the dry months of January through Web, the rainfall may be under 1 inch or over 13 inches. The wind and rainfall regimes, including especially the variabili- ty in rainfall, are two of the three major factors that endow the 53m]: Islands with a distinctive climate. The other factor is the character of the weather. local showers, sometimes of considerable intensity, are cannon at all times of the year, but especially from April through December. thunderstorms , however, are rare. So also are distinct large -scale tropical disturbances, such as tropical storms and ty- phoons. Therefore in a descriptive sense the character of the weather at any one time is expressed on a far more local scale on the m1: Is- lands than it usually is in middle latitudes or even in many other is- land groups of the tropical seas. Very often conditions may be only partly cloudy over one of the Truk Islands while at the same time there is overcast with torrential showers on sane other island; and where the larger high islands such as 'lbl, Dablon Island, and Moen are concerned, very different weather conditions may exist simultaneously even from one side of an island to the other. line seasons: It is convenient to recognize the existence of four sea- sons in the m Islands, as follows: the dry trade -wind season, from Jamary through lurch; the first of two rainy trade-wind seasons, from April through June; the season of the doldrums, July through October; and the second rainy trade-wind season, November and December. Dry trade-wind season (January through March): 11113 is the season of strongest winds, often in excess of 15 m.p.h. hey are from easter- ly directions over 85 percent of the time, chiefly from the northeast. Average monthly rainfall. is 6 to 9 inches, with monthly totals some- times less than 1 inch. 'nmugh humidities are high and cloudy condi- tions prevail, this is the season of lowest humidities, of least cloudy conditions, and of the greatest amount of sunshine. First rairqr trade-wind season (April throgg‘riJ'une): During this season winds are seldm in excess of 15 m.p.h. and usually less than 10 m.p.h. Winds are easterly over 80 percent of the time, but without the great dominance of northeasterly winds that is characteristic of the dry trade-wind season. he rainfall averages in excess of 12 inches in each month, with, however, great variability from year to year, espe- cially in April. Sky cover is 0.8 or more about 60 percent of the time and 0.1; to 0.7 during the remainder of the time. Doldrum season (July thflugh October): Winds are light and varia- ble, with frequent calms. The rainfall averages in excess of 12 inches in each month, with frequent moderate to heavy showers as well as peri- ods of prolonged light to moderate rains. 81¢ cover is 0.8 or more about 60 percent of the time. Second rainy trade-wind season (November and December): Once more the winds are dominantly from the east. However, wind speeds are usu- ally below 10 m.p.h. and seldom above 15 m.p.h. The rainfall exceeds 12 inches in each month on the average. This is the season when wide- spread tropical disturbances, such as tropical storms, are most likely to occur. However, well-defined tropical storms are not common, occur- ring only once every 3 to it years on the average. Humidities are slightly higher than in any other season and 0.8 or more sky cover is to be expected two-thirds of the time. Geographical variations in the climate: On the high islands of the Truk group there are significant variations in wind, cloud, and rain- fall conditions from one location to another, chiefly as the result of differences in exposure and elevation. Among the low islands, the only significant variations are on a microscale and are associated with variations in vegetative conditions. {mess climatic differences are considered under their separate headings. Aspects of climate miculer practical interest: those aspects of the climate of the Truk Islands that are of particular interest from a practical engineering and military point of view are the wind condi- tions as related to airborne and small-boat operations; rainfall as related chiefly to problems of construction, water supply, and traf- .ficability; and storms and squalls, which are important from many prac- tical points of view. These three aspects of the climate are therefore emphasized in the following pages, and, in addition, climatic condi- tions as related to comfort and variations in microclimatic conditions, two topics of special interest, are considered separately. Insolation and illmnination Including the times of civil twilight, when there is sufficient light before sunrise or after sunset for unimpeded outdoor activity, the length of day at the W Islands varies from 12 hours 27 minutes on the average in December to 13 hours 20 minutes on the average during June. The total daily insolation at the outer limits of the atmosphere varies from 788 gram calories per square centimeter (gm. cal./cm.2) on December 22 to a maximum of about 890 gm. cal./cm.2 in late March. Insolation at the ground ranges from a minimum of about 250 an. cal./r..'m.2 on an overcast day in December to a maximum of about 550 gm. cal./cm.2 on a partly cloudy day in March or April. Table 1 presents more detailed values for these variables. 13 wt Table 1. Illumination and insolation, Truk Islands A. Duration of daylight and civil twilight on the 17th of each month at 7°30' N. lat. 1/ (in hours and minutes) Jan. Feb. Mar. Apr. May June July Aug. Sept. Oct. Nov. Dec. Daylight 11 H“ 11 5h 12 05 12 18 12 28 12 3H 12 3O 12 21 12 O9 11 57 ll 47 ll #1 Twilight 22 21 21 21 22 23 23 22 21 21 22 23 B. Total daily insolation at the top of the atmosphere on selected dates 2/ (in gram calories per square centimeter) mar. 21 Apr. 13 June 22 Sept. 23 Oct. 16 Dec. 22 889 885 831 878 860 788 1/ Data obtained by linear interpolation from Tables 171 and 172 of List (1951). 2/ Data obtained by linear interpolation from Table 132 of List (1951). Barometric pressure Tables 2 and 3 present infomation concerning monthly and diurnal variations in sea-level pressure and extreme pressure values that have been recorded. The salient facts brought out by these tables are that the mean pressure varies from a low of 1005.8 millibars (29.701 inches) in December to a high of 1007.8 millibars (29.760 inches) in June; that the diurnal variation in pressure is greatest in the dry trade-wind season (3.1 millibars or 0.091 inch in January) and the least in the doldrum season (2.1 millibars or 0.063 inch in July) 3 and that the ex- tremes observed to date are 995.7 millibars (29.h02 inches) and 1013.0 millibars (29.913 inches). It is important to note that the doldrum season is the season of lowest pressures. Temperature Air temperatures in the W Islands vary remarkably little from month to month, each month having a mean value of between 80.3° and 8L3“ F. The greatest extremes of record are 69° and 91V. Tempera- tures below 72° or above 89° occur but rarely, except at the highest elevations, above 1,000 feet, where nighttime temperatures in the high sixties are moderately common at all seasons. The temperature march on any particular day is related primarily to the cloud conditions, rather than to the duration of daylight or the altitude of the sun. Accord- ingly, with a dense cloud cover above one portion of an island and with only broken clouds across another portion, the temperature difference between two localities only a few miles apart may be as much as 5° at any one time. Detailed temperature data for the Truk Islands are dis- played in table is. ' Wind The general wind conditions over the Truk Islands are represented by the series of wind roses that appear in figure 2. In that figure, the February roses are representative of conditions during the dry trade-wind season; the May roses, of the first wet trade-wind season; the August roses, of the doldrum season; and the November roses, of the second wet trade -wind season. 'me most important features of the general wind regime are that wind speeds are distinctly higher during the dry trade-wind season than at any other time and that speeds are considerably lower during the doldrum season than at any other time. As for wind direction, once more the dry trade-wind season and the doldrum season represent the two extremes, with highly constant winds fran the northeast quadrant during the former season and with extremely variable winds during the latter season. In all but the dry trade-wind season, wind speeds are slightly higher in the afternoon and evening than they are in the early morning around sunrise. The wind roses of figure 2 quite reasonably represent the general wind regime of the 'Bruk Islands, but they do not reflect the local vari- ations that occur because of the influence of topography upon the wind nor do they show the extreme wind speeds that sometimes obtain during gusts. From the wind observations of the American period, 1916 to the present, at the edge of Moen Airfield and from a general consideration of the kinds of weather situations that prevail in the film]; Islands, it 15 Table 2. Monthly mean and extreme air pressure, Dublon Island, Truk Islands y (in inches and millibars of mercury at sea level) Mean pressure Maximum pressure Minimum pressure in. mb. in. mb. in. mb. January 29.705 1005.9 29.862 1011.3 29.563 1001.1 February 29.756 1007.7 29.913 1013.0 29.602 1002.5 March 29.728 1006.7 29.886 1012.1 29.559 1001.0 April 29.720 1006.5 29.862 1011. 3 29.602 1002. 5 May 29.756 1007.7 29.870 1011.5 29.630 1003.1; June 29.760 1007.8 29.909 1012.9 29.650 10011.1 July 29.71411 1007.3 29.878 1011.8 29.567 1001.3 August 29.7% 1007.3 29.898 1012.5 29.598 1002.3 September 29.7118 1007.h 29.913 1013.0 29.583 1001.8 October 29.7118 1007A 29.898 1012.5 29. 567 1001.3 November 29.709 1006.1 29.882 1011.9 29.5117 1000.6 December 29.701 1005.8 29.870 1011.5 29.1102 995.7 Annual 29.736 1007.0 29.913 1013.0 29.102 995.7 _/ Mean based on observations at 0200, 0600,1000, 1100, 1800, and 2200 standard time, 150° E. long. Extremes are absolute extremes for individual barometer readings, and are from the East Asia Research Institute (19112) . Table 3. Mean air pressure at h-hour intervals for four selected months, Dublon Island, Truk Islands 1/ 0200 0600 1000 11100 1300 2200 January in h s: .6 . . 6.66 . . mmfisn $305377 E8083 E8032 $851.6 5 $3022 $3083 April inches: 29.713 29.728 29.756 29.689 29.713 29.7611 millibars: 1006.2 1006.8 1007.7 1005.1; 1006.2 1007.9 July inches: 29.732 29.710 29.768 29.713 29.721; 29.776 millibars: 1006.9 1007.1 1008.1 1006.2 1006.6 1008.3 October inches: 29.728 29.752 29.776 29.705 29.710 29.780 millibars: 1006.7 1007. 5 1008.3 1005.9 1007.1 1008. 5 y Based on Japanese observations, 1935-1938 inclusive. l6 G IIdable 14. Mean and extreme temperatures, 'Iruk Islands y (in degrees Fahrenheit) Mean Mean Extreme Extreme Mean maximum minimum maximum minimum January 80-9 85-3 76.5 89 71 February 81.0 85. 5 76.5 91 72 March 81.3 85.9 76.7 91+ 72 April 81.2 85.7 76.6 90 71 May 80-9 85.9 75.9 91+ 71 June 80.5 86.1 7h.8 90 71 July 80.3 86.6 7h.0 90 70 August 80.3 86.3 7h.2 91 70 September 80.7 861; 75.0 91 70 October 80.7 86.6 714.8 91 70 November 80.8 86.3 75.2 90 71 December 81.1 85.8 76.3 89 69 Annual 80.8 86.0 75.5 . 9h 69 l/ Mean, mean maximum, and mean minimum values are from U.S. Dept. of Commerce, Weather Bureau (1951:) , and are based both on Japanese records from Dublon Island and U.S. records from Moen, for the period, 1921-1950. Extreme values are based on American records, 1916-1955, and upon Japanese records at Dublon Island, 19311-1938. Table 5. Mean relative bmnidity, Moen, ‘Bruk Islands y (in percent) ime°.o 0 1000 1 2200 January T 79 79. 82 February 83 78 7s 7 82 March 82 78 76 > 82 ‘ April 83 78 78 82 my 85 80 80 , 85 June 88 82 81- 86 July 90 80 " 80 86» August 88 79 80 86 . September 87 79 79 86 October 88 80 80 87 November 88 83 83 37 December 86 83 83 86 Annual 86 . 80 80‘ p 85 y Data from U.S. Dept. of Commerce, Weather Bureau (1951+). All values except those for ohoo are based on ‘1 years of records; ohoo values are based on 2 years of records. 17 f i 2 is possible to describe some typical local wind effects and to cite some actual instances of gust velocities. fibers are two effects that have been observed on Moen when the trade winds are blowing at speeds in excess of about 5 to 8 m.p.h. Moen Airfield is situated. in the northwestern corner of that island and is bordered by the lagoon on the northwest and by Tanaachau moun- tain to the southeast which rises to a height of 751 feet (229 meters). Under the trade-wind conditions described, and especially with the wind from between the east-northeast and southeast, an eddy is formed at the southwestern end of the runway so that the wind direction there is southwest. Simultaneously, the wind direction at the northeastern edge of the runway is northeast. This type of situation is certainly not confined to Moen. Wherever there are lowland areas that lie to leeward of a prominent hill and whenever simultaneously the winds are in excess of 5 to 8 m.p.h. , local eddies will be formed that give rise to aberrant wind directions in the lowland and also, occasionally, to local gusts and updrafts, especially when the overall. wind is blowing at speeds above 15 m.p.h. A second local wind effect that has been observed on Moen con- cerns the funneling of winds through the saddle that is oriented ap- proximately northeast-southwest and that lies between Tanaachau and Vinifauren Ridge to the southeast. Winds from an easterly direction, and especially those from between north-northeast and east-northeast, blow through this saddle area at speeds that are decidedly water than over the open water. Thus northeast winds of 15 m.p.h. over the water may yield steady wind speeds of 20 to 25 m.p.h. in the saddle with gusts sometimes as high as 35 m.p.h. Effects of this kind most certainly are felt also in other saddle areas that are oriented in a general east-west direction so as to catch the strongest winds from the trade directions. Eyes without the presence of standing eddies or of funneling effects, winds are often gusty so that high velocities not reflected in figure 2 are sometimes momentarily reached. Fran a review of 5 years of observations at Moon, using the 5—a-day observations for Feb- ruary and for August, it is apparent that strong gusts occur chiefly during the trade-wind months. To cite a few examples for February: in one instance gusts of 25 m.p.h. were superimposed upon a 1% m.p.h. steady wind. In another instance, gusts of 23 m.p.h. were superim- posed upon a wind of 9 m.p.h. In still another, 12 m.p.h. steady winds yielded gusts of 28 m.p.h. According to Mr. William Taliaferro, who was the Official-in-Charge of the U. S. Weather Bureau station at Moen during 19514-55, in extreme instances gusts of up to 1&0 m.p.h. have been experienced during the trade-wind season. During the doldrum season conditions are not nearly as gusty, but there are very occasional situations with gusts up to 15 or 20 m.p.h. and, even more rarely, there are sometimes conditions with steady wind speeds well in excess of those shown in figure 2. During the 5-year period, 1952-1956, only one such event of anomalous high winds was ob- served. Ou August 8-9, 1953, the winds exceeded 20 m.p.h. at several observation times and in one instance reached 25 m.p.h. In all these instances, the strong winds were from the south or south-southwest and there were heavy rain showers. Although this is an isolated example, it is certain that in all parts of the Truk Islands area there are very occasionally winds of this magnitude during the doldrum season, because of intense local circulations associated with vigorous con- vection and resulting showers. In fact, it is most certainly a 18 Standard Time l50° E l I400 percen’rage frequency scale <——percen’r of wund speed In mules per hour [44441 I I I I I J calms __:—:— ° '° 2° 3° 4° 5° 6° <—number of 0-5 5-l0 l0-l5 l5-20 20-25 all values To nearest Whole percent FEBRUARY |65 observations MAY AUGUST Figure 2 WIND ROSES FOR DUBLON ISLAND,TRUK ISLANDS (compiled from original Japanese records,I9l9-l92l,l934-l938) NOVEMBER S‘landard time I50°E l9 characteristic feature of the winds of the doldrum season that at any one point wind speeds will fluctuate rapidly with changes in cloudiness and in shower activity. Usually, the winds will not exceed 10 m.p.h. , but below this limit their speed will vary abruptly as will also their direction. This type of wind behavior is a common feature of doldrum situations over the tropical oceans as is evident from many shipboard observations during the war, when the commanders of aircraft carriers had to maneuver their ships to find a particular local spot in which wind and cloud conditions favored the dispatching or receipt of air- craft. In conclusion, it is important to note that even though the Thai: Islands have occasionally experienced a tropical. storm, the winds gen- erated in mm by these storms have not been excessive, at least within the period of observation. Certainly the chances are at least even that during a period of 25 years, with or without a tropical storm, the steady wind speeds over the water will never exceed ho m.p.h. , although with a general wind of over 30 m.p.h. wind speeds in saddle areas and similar topographic situations might reach 50 m.p.h. in gusts. Huinidi‘by As is evident from the data of table 5, relative humidities in the m1: Islands are high throughout the year with only a very slight maxi- mum during the second rainy trade-wind season and with the usual diur- nal variation whereby the highest relative humidities occur during the night and the lowest during the afternoon. Not reflected in table 5 is the fact that in exceptional instances, as with local warming on an unusually sunny day, the relative humidity may fall as low as 55 percent; while during the nighttime in particular, although also occa— sionally during the day as well, humidities of 100 percent are fairly common. In absolute moisture terms, mixing ratios of 20 yams of moisture per kilogram (gnu/kg.) of dry air (1% grains per pound [fin/lbj) are very common; mixing ratios of 22 gm../kg (151+ gr./lb.) are fairly com- mon; and in extreme instances there are mixing ratios of 28 gm./kg. (196 gr./lb.), or even very slightly higher. Cloudiness 'me gross features of the cloudiness regime at the Truk Islands are evident from the data of table 6. As these data indicate, there is slightly less cloudiness during the dry trade-wind season than at other times of the year and slightly more cloudiness than average during the second rainy trade -wind season (November and December). Not evident from the data of table 6 is the difference between the trade-wind and doldrum seasons in the thickness of the clouds that partly or wholly cover the sky. In the trade -wind seasons, the slqr is chiefly covered by thick, relatively low cumulus clouds that often entirely obscure the sun. This same condition frequently occurs in the doldrum season as well; but in addition there are frequent periods in the (101an season when the slq is covered or partly covered only by high thin clouds that neither obscure the sun nor greatly reduce the intensity of sunlight. Despite the high average cloud cover in the Truk Islands, it is virtually always possible for an approaching aircraft to find breaks in the overcast through which to descend safely to altitudes from which the water and the islands can be seen. Even on the cloudiest days there are rarely continuous cloud decks such as are common in middle latitudes; rather, there are broken cloud layers at several different levels and these are interspersed with cumulus cloud masses that some- times tower to heights of 50,000 feet or more. According to Commander Iarry Booda, USER, who was engaged in photoreconnaissance in the Caro— line Islands region during the latter part of the war, it was always possible from a navigational viewpoint, safely to penetrate the cloud cover over the Truk Islands, either for photoreconnaissance or for sow- ing of mines. Upon the islands themselves, there are minor variations in cloud conditions that are associated with the topography. The higher moun- tain peaks on Moen, Tbl, Dublon Island, Fefan, Udot, and Uhan tend to hold small cloud masses high on their windward flanks when there is a pronounced circulation of air across the islands, as when the trade winds are blowing. For this reason, the west (leeward) coasts of the high islands are somewhat less cloudy than the east coasts. Thus the cloud data given in table 6, which reflects conditions on northeastern Dublon Island, are too high by a factor of about 10 percent for such locations as the west coasts of Moen and Udot; the west coast of north- ern Fefan; and the west coasts of Tel and Dublon Island in those local- ities where mountains that rise to 1,000 feet or more lie between the coastal location and the easterly to northeasterly trades. There is, however, some oversweeping of clouds at the altitudes of the higher mountain peaks as well as a carryover of cloud higher aloft. Further- more, dnring the doldrum season the mountains have relatively little effect upon cloud distribution. Across the water the bases of the clouds are nearly always above 1,500 feet except when rain is actually in progress. Even shower ac- tivity rarely lowers the ceiling to below a height of 500 feet above the water, and then only over limited areas. Mere general rains some- times lower the ceiling over wide areas, but seldom to heights below 200 feet. Visibility Except where visibility is briefly diminished in one or more lim- ited sectors because of showers and except when visibility is generally reduced as the result of more prolonged widespread rains, it is always possible to see for distances of 10 to 20 miles across the waters of the Truk lagoon. limitations on visibility upon the land are related to the distribution of low clouds as already described. Rainfall General characteristics: The monthly variations in rainfall are shown in table 7 and in figure 3. So far as the mean monthly values of table 7 are concerned, the most reliable means are those from Moen (table 7). The means for Eten (table 7) are not highly significant because of the shortness of the record and particularly because of numerous interrup- tions of the period of observations. 22 Table 6. Sky cover and sunshine, Dublon Island, Truk Islandsi/ A B c D E F a? ’5 7:? 5’ 3% g A :3 ”a “a s ° “6 ° '8 '3 a H H g Q :4 a) g H '3 o m (n a) to g 3 m 0 >, m '3 0 8. H m ,0 h H ,0 '8 O «P g 0 2s 53“ a°t a . 5.: .5. O a a 0? :1 3?? “3'7. :1 8 w :1 ,q 0 5°3 5%? a e 539 at? a§* £55 £33 sis £33 £35 ems January 7.9 o 13 18 1 61 February 7.7 0 12 16 O 62 March 7.6 o 11 20 1 56‘ April 7.5 o 12 18 2 56 May 7.7 0 10 21 1+ ‘6 June 75 l. 12 17 2 55 July 7.6 o 1.1 20 1 53 August 7.h * 10 21 1 50 September 7.1+ 0 l3 l7 2 51+ October 7.5 1 12 18 2 5h November 7.5 0 ll 19 3 1‘3 December 7.9 o 11 20 h #9 Annual 7.6 2 138 225 23 5‘» y Data for column A are for 1927-1928 and 1930-1938 (South Sea Bureau, Meteorological Observatory, no date, and East Asia Research Institute, 191+2). All other data are for 193h-1938 (East Asia Research Institute, 19h2) and have been adJusted proportionately in columns B, C, and D to correct discrep- ancies in the original tables between total entries and total days in each month. * lass than 0.5. 23 d W. /o e h I . d m a all! 0 1-:J d e 9 rlllll. e w 0 n d m x m I N m .m e w w % d nlu m... .m b w e 7 T I i e f e.” C A o .m w Ana x o/o N S r.I e _MMMMMAU A r S H 0 5 I L G r 0 e e r P e a f h b a X Y w. n l e /o .I I y e H o E s f m c w r Bangs 2 o m a 2 .m IV. h Ill U e m c ,m c o If" .I / r m n e m.” BBEE§ m e O h 0 O | D. m T r p C. 8 E 2 _.iiii.Iiiiiiiiiiii. D V‘“\‘\‘\“‘\\‘\\~\~\\“‘A E u vMQHOHOHONOHOnOu. lg -_I_-_I_-_-_-_-_l_-_!-_u...— ‘§‘~“§§§“‘A 28 NOV. E VMOMOHONOM§H MONO“. % _-_-_-_Elia—I.-_I_-=_-_-_I_-.-_-_-_I: 29 OCT. UMOMOMOHQNONOMQHA % I.Iii—Iii...2-3—5222!!— w--~§§§§§§$ 29 SEPT. G. Ill “”“H ””"H." = 2335.55: _\\\\\\ \\\\\\\\\\\\\ \ 29 AU WV/xx // ///////V/////////// 1I|l E VHOHOMQMOHOHOHONOHONOH. % _-_SEE-ii:—-_-_I.-_-_-_-_-__ V“-“‘~‘“‘~‘-‘~A 29 JULY 8 2 JUNE V _.-.-i...I.-_Iii—22.33.22... r//////////// // ///////_ MAY R. O P 3 A R A M B. E F N. 9 ii A 2 -.-_-=_-_-_-_-_—_-_-__ J s----~““‘~“fi _ _ _ _ _ _ ‘ q _ J 0 0 “a 4 w 3 a w w m 5 a $28: :85? questionable reliable maximum rainfall minimum minimum rainfall Figure 3 MONTHLY RAINFALL VARIABILITY,TRUK ISLANDS (records in doubt) rainfall (based on table 7, with all values‘adjus’red lo Moen means) mr Table 7. Monthly and annual. rainfall, Truk Islands (in inches) Year January February March April May June J'tfly August September October November December Annual 190% 7.17 7.05 10.87 10.%7 12.8% 17.66 11.97 13.31 16.85 %.37 7.68 3.35 123.59 1905 - 8.11 3.86 8.39 9.25 10.75 15.28 12.01 5.71 6.30 11.3% 6.18 - 1906 2.8% 3.62 7.09 17.52 13.27 6.%2 10.59 8.%3 12.6% 6.3% 12.72 19.80 121.28 1907 11.97 8.35 12.6% 5.71 13.11 10.32 6.93 - - - - - - ‘1 1908 - - - - - - - - - - - - - '* 1909 11.89 7.95 7.2% 5.79 9.%9 16.02 11.69 11.10 12.80 - - - - 8 1910 - 12.6% %.80 15.20 1%.69 16.02 15.12 12.36 13.27 11.3% 18.35 9.%5 - E3 1911 2.13 13.90 11.97 - - - - - - 1%.%1 6.97 %.25 - 1912 3.82 5.67 0.91 1%.17 9.96 %.53 11.38 - 15.0% 16.68 1%.8% 12.95 - 1913 0.20 5.59 6.1% 13.9% 15.2% 8.27 1%.25 21.93 - - - - - MBans 5 72 8.10 7.28 11.%0 12.23 11.25 12.15 13.19 12.72 9.91 11.98 9.33 125.26 1927 7.52 6.81 %.33 2.52 11.72 12.36 3.70 8.60 6.08 5.87 8.56 5.96 8%.03 1928 5.%8 %.36 2.52 10.61 9.72 18.%7 10.60 7.0% 3.19 3.10 5.61 3.5% 8%.2% 1929 5.91 0.85 0.88 5.8% 9.58 10.77 15.72 10.71 11.16 9.56 13.27 6.18 100.%3 1930 2.80 2.%8 10.91 13.21 7.65 1%.29 1.80 1.%% 1.23 0.59 9.5% 5.29 71.23 201 1931 0.59 0.07 6.36 2.58 11.52 10.88 8.%9 20.58 9.3% 20.89 11.38 9.25 111.93 .5 1932 - - - - - - - - - - - - - a 1933 5.56 3.3% 10.1% 28.13 8.65 1%.%2 12.9% 13.29 15.06 16.35 11.65 9.27 1%8.80 3 193% 17.52 11.39 6.83 9.89 16.78 8.15 9.80 5.88 17.97 10.21 13.90 10.%7 138.79 ** 1935 %.%9 7.95 5.55 11.55 1%.06 9180 18.53 8.66 13.82 8.5% 13.%7 23.6% 1%0.06 8 1936 2.6% 3.%7 %.53 %.53 1%.02 8.31 9.53 11.%6 7.80 13.5% 16.22 13.07 109.12 :3 1937 6.10 2.%8 3.35 10.71 13.11 10.71 15.59 10.87 9.72 1%.92 15.79 11.69 125.0% 3 1938 17.72 %.29 17.73 15.32 13.62 13.50 9.37 15.20 16.15 9.61 15.59 16.%7 16%.57 1939 5.28 1.%6 7.09 5.55 7.05 5.75 8.%7 10.12 12.05 17.51 7.56 9.25 97.1% 19%0 10.79 10.98 9.06 10.71 11.81 13.15 15.08 19.39 17.25 20.35 5.20 6.5% 150.31 means 7.11 %.61 6.87 10.09 11.%8 11.58 10.7% 11.02 10.83 11.62 11.36 10.05 118.37 l9h6 10.31 7.31 3.7% 15.85 15.17. - - Moen _3_/ 19%7 - - - - - 15.35 8.81 15.3 15.60 9.68 - 19%8 9.78 1.89 2.97 6.78 15.06 1%.38 9.97 11.22 10.50 13.68 8.63 2%.1% 129.00 19%9 - - - - - - - 5.37 7.39 8.0% 12.%8 7.37 - 1950 %.55 0.8% 2.30 12.5% 15.57 21.72 18.39 11.33 18.78 1%.29 7.91 17.90 1%6.12 1951 15.73 7.31 6.56 17.71 - - 11.71 15.0% 7.89 21.29 7.83 8.5% - 1952 10.13 2.93 7.39 5.62 11.37 16.50 11.91 1%.51 11.98 11.69 13.71 6.95 12%.69 1953 8.26 6.3% 8.96 18.30 8.%1 15.30 11.10 20.%2 9.%9 15.31 18.29 9.95 150.13 195% %.13 10.52 6.26 9.70 22.%7 1%.38 13.65 1%.07 17.02 12.69 13.60 23.6% 162.13 1955 8.92 %.75 %.88 23.03 23.57 11.76 1%.30 15.89 21.17 22.%2 13.20 9.88 173.77 1956 10.59 8.78 12.21 23.38 17.11 12.%1 15.76 10.92 15.75 9.8 means 9.16 5.63 ° 6.1% 1%.77 16.09 15.21 13.35 13.%1 12.88 1%.%6 12.36 13.12 1%6.58 l/ Data from Mitteilungen von Forschungsreisenden und Gelehrten ans den Deutschen Schutzegebieten (1905-19110 . 2/ Data from Central Meteorological Observatory (195%). g/ Data from U. S. Departnent of Comerce, Weather Bureau (195%-1956). - No observation. 25 The means for Dublon Island (table 7) are slightly suSpect because an examination of the original records for the period 1935-1938 has shown that on many days, sometimes as many as five or six in a single month, no rainfall observations were made. Most significant of all for many practical purposes are the median monthly values shown in figure 3. Of special interest in a practical sense is the variability in rainfall from one year to another, the geographic variations in rain- fall, diurnal rainfall variations, the frequencies and amounts of heavy falls of rain, and the frequencies and intensities of drought periods during the dry tradeawind season. Each of these topics is considered separately in the succeeding paragraphs. Annual rainfall variability: The extreme variability of rainfall from year to year is evident from the data presented in table 7 and shown graphically in figure 3. The most important practical conclusions to be drawn from figure 3 are as follows: (1) During the dry trade-wind season the chances are at least 1 in 10 that there will be less than 3 inches of rainfall in any one month. (2) February is by far the driest month at the Truk Islands and the chances are about 1 in h that in February the rainfall will be less than 3 inches and l in 10 that the rainfall will be less than l.h inches. (3) The remarkable variability in April rainfall makes it clear that April is a transitional month between the dry tradedwind season and the first rainy tradeawind season. In one-quarter of the years of record, April has been almost as dry as the usual March, and in one-half of the years of record, April has been rainier than the rainiest March of record. (A) Except for April, the months of greatest rainfall variability are December and January, al- though the variability is almost as great during the months of the dol- drum season. Although figure 3 is certainly subject to sampling error and al- though, more seriously, it is based in part upon records that are not complete, it is sufficiently reliable to be used as a general index of the probability of getting various amounts of rain at the Truk Islands in the different months of the year. However, in applying figure 3 in this manner, allowances should be made for geographic variations in rainfall, as discussed below. Geographical variations in rainfall: The only data that are available to illustrate geographic variations in rainfall at the Truk Islands are the monthly totals for the years 1933 and 193A, for five observing sta- tions, one each on Tol, Udot, uman, Dublon Island, and Moen. These comparative values are shown and also are represented graphically in figure h. They bring out the fact that in any one month rainfall dif- ferences from place to place may easily be 1 to 2 inches and may some- times be as great as 10 inches. This geographic variation is not sur- prising because much of the rainfall occurs in local showers and since even within one local shower area there will be variations of several hundred percent in the amount of rain falling at one particular point as against some other. Thus solely on this basis one locality may in a given month happen to receive 15 or 20 more showers than some other locality a few miles away. This same kind of mechanism accounts in part for the great variability in rainfall from one year to another at any one particular location. In addition to these virtually random geographic variations in the rainfall in any one month and year there are the variations that are associated with the topography of the high islands. 0f the five sta- tions for which data are presented in figure h, one was in a shielded 27 leeward position. This was the\ tation on the west coast of Udot. It is significant that, as the com tive data show, Udot received far less rainfall both in 1933 and in 1 31+ than did any of the other four stations, all of which were in exposed locations. It is significant also that in 1h instances out of 16, Udot received either the lowest or the next to lowest monthly rainfall during the three tradeawind seasons; whereas during the doldrum season Udot received the lowest or next to lowest rainfall in only five instances out of eight. While these data are not conclusive, they strongly indicate that the low an- nual values for Udot are associated with its leeward trade-wind loca- tion since it loses its leeward position during the doldrum season. From the data of table 7 and figure A, and from the general con- sideration of the kinds of weather situations that give the Truk Is- lands its rainfall, it is certain that the chances favor higher rain- fall on the windward coasts and these chances would doubtless be re- flected in any long—term means or medians. In quantitative terms the difference between the long-term mean rainfall on a windward as against a leeward coast for an island such as Mben or Tbl would certainly be at least 10 percent and might be as high as 15 or 20 percent. There are also geographic variations in rainfall associated with differences in the elevation of particular localities. Sites on the east to northeast slopes of the higher mountains must receive 5 to 10 percent more rainfall than sites with the same exposure but located at sea level. This fact is in accord with what is known from other tropi- cal island areas, but is also inferentially supported by occasional visual observations on Mben, where showers are often seen to be in pro- gress on the higher mountain slopes at times when there is no rainfall in the saddle or along the coast. So far as the low islands are concerned, there is no reason to suppose that there are any appreciable differences among them in the chances of their receiving rain, except in those few instances in which a low island lies to the west or southwest of a high island and close enough to it to be shielded from the tradeawind air. This is notably true only of a few scattered islets that lie between Udot and T01, to the west of T01, and between Dublon Island and Fefan. The diurnal rainfall regime: Because figure 5 is based on so few ob- servations, its minor features are not significant. 0f significance, however, are the two diurnal maxima during the late nighttime in the two rainy tradedwind seasons. Also significant, although less pro- nounced, is the late nighttime maximum of the doldrum season and per- haps also the secondary maximum during the early evening both in the rainy trade-wind seasons and in the doldrum season as well. Rainfall frequencies and intensities: The mean number of rainy days with total falls of various amounts are shown for Dublon Island and for Moen in table 8. Where a rainy day is defined to include days on which the falls are as little as 0.00# inch, the rainfall frequencies are essentially uniform from May through December. However, where the rainy day is defined as one on which there is 0.0h inch or more of rainfall, November, December, and the 3 months of the dry tradedwind season become relatively low-frequency months, with only about one-half of the days being rainy. During the remainder of the year, April through October, there is 0.0h inch of rain or more on approximately two-thirds of the days in each month on the average. Thus the first rainy tradeawind season and the doldrum season are the periods of most frequent moderate to heavy showers; whereas very light showers are 28 -|80 O 0 O 0 0 w m o. 6 3 _ _ _ _ _ mow.”0.4%.?Wurmowwuwnwurmomonouonowowaafla. allll’llllllllllllllll’d HONOHOHOMONOHQMOHOHQHONONQHONOHON. a””””””¢ ANNUAL NOV. DEC. OCT. VNOHOHOHOMOMOMQHOHOHOHOMOMONOMOH‘ V"”’"“ i‘~““‘““k "OHOHOMQNOMQHONQM Vlll’l’la SEPT. AUG. . . omouowouflwuwuwwuwwomom all/’IIZ‘IIQ JULY w . \\\N\\\\\.\\.\ V“““‘L .NOHONONONOHONOMQH vlllllllll’lfi JUNE MAY xxxxxfixfixxxxfixxxx.\.\\\.\.\\. . nom.“on.”owmafia.noumuowowomownouowowomomagma. "I‘ll““llga s---5 ONOMQHOHOMOMOHOMOHOH allllillllgll APR. MAR. l4.07 FEB 2.54 JAN. 30- 25- 20 IS I0 5 0 $2.25 2858 Will) L\\\\\‘ Udof-—————— 5.96 To! ———————-—— 8.” 4.26 3| 9 Moen— —- ———— 5.37 25.33 IO.| 3 Il.85 Umon——————— 7.43 28.!3 IO.I4 3.33 Dublon ls.— ——_ 5.56 Figure 4A COMPARATIVE RAINFALL TOTALS FOR FIVE STATIONS,TRUK ISLANDS, |933 (dofa from The Soufh Sea Bureau,Me’reorologicoI Observatory) mm 0 0 0 0 _ _ _ _\\\\\\\\\\\\\\\\\\\\\ nsMQMOHQMOMOnOHOHOHQMOHQHONOHO”NON“.HQHQHOHOMQM , v””””””’”””””l -—|80 0 5 _ —|20 9 6 3 HONON H M NONOHQHOHQNOMQHON. V””””””¢ ERQQSQfiQm wwwowmnvnrmowomnouonflo.mafia“ , fol‘flldrdrlf §\\\\‘\\L Eu «‘nouonfiouou.» xxxxxmxxxxxxxmxmx. no.".nowon«flour...»wwmnouowowowmnmum all/flfllllld VNONOHOHOMONOMOMQNOM algl’lll" VV\\\\\\\\\\\\\\ flONOHONOMOHOMOMOHOMON agfilgll.’ 5““a‘l E w HOMOHOMONONONOMOMOMOH. ggglll’lé ,0HOHQNONONOMONONOMONONOMOHOMQMONO >>>>> afiflgfifigfil" 30— 25‘ O 5 IO‘ 5 0 Rogue: :35? ANNUAL DEC. 8. V. O II.36 l3.67‘ l5.70 l5.42 l3.80 N OCT. I2.62 13.34 SEPT. AUG V JUNE JULY Y A I L68 I353 I086 M R. p ||.39 I3.05 l|.6| l2.90 A AR. M 6.4 FEB. JAN. Udo’r -———--———|4.9 I ”5.82 — 9 I509 l4.97 l8.78 I872 I797 58 9. 9.77 IO. 78 9.8 9 I309 2.| IO.|2 5 9 IO.52 2.5 9.6 Vlllll] |53.2| I4.36 I373 86 :90 6. 8.7 ||.60 5.9 6.8 -_______2o.33 Moen——————— 21.37 To! I486? 7.54 9.77 IO.22 7. O 6 6 ”.39 L\\\\\‘ 89 l0.47 9. 4 3 9.4 Uman———-—-—— I922 I40.77 85 8.|4 9.8! 7. I6.78 9.89 Dublon |S.-—--—-—l 7.52 Figure 4B COMPARATIVE RAINFALL TOTALS FOR FIVE STATIONS, TRUK ISLANDS, I934 ( da’ro from the Sou’rh Sea Bureau,Me’reorologicol Observa’rory) we TE JAN- Percent of time rain observed FEB. (observations on the clock hour) MAR. APR. :xzzxzzi More than 25% MAY BEE] 20 t ° JUNE 0 25 /0 Y E JUL '5 to ZOO/o AUG. VIIA IO t I ° SEPT. ° 5/° oat. E Less than IO°/o NOV. DEC. II 0 I 2 3 4 5 6 7 8 9 IO II l2 I3 I4 I5 I6 I7 I8 I9 20 2| 22 23 24 standard time (hours) I50° E. Figure 5 DIURNAL RAINFALL FREQUENCIES, MOEN, TRUK ISLANDS (each entry based on 89 to I55 observations by U. 8. Weather Bureau) Table 8. Mean number of days with rainfall of specified amounts, Truk Islands y A B C Rainfall 0f Rainfall of Rainfall of 0.01% inCh 0.01 inch 0.004 inCh or more, or more, or more, Dublon Island, Moen, Dublon Island, 193h-1938 1950-195h 1933-1938 January 15 14 19 February l3 l2 17 March 16 11+ 18 20 16 22 (‘t April .3 May 22 22 28 June 21 22 2% July 21!- 21 26 August 20 24 26 September 19 23 21 October 21 23 26 Nbvember 15 2h 26 December 11+ 21 25 Annual 220 236 278 y Column A is computed from values given by the East Asia .— Research Institute (l9h2); column B is taken from U. S. ( Department of Commerce, Weather Bureau (l95h); and column C is computed from values given in the South Seas Bureau, Meteorological Observatory (no date), and the East Asia Research Institute (l9h2). 32 about equally frequent throughout all of the year except for the dry trade-wind season. The fact that moderate to heavy showers are less frequent in the second rainy trade-wind season by no means contradicts the data pre- sented in table 9, which shows the greatest 2h-hour, 6-hour, and h-hour rainfall experienced during each month during the years of record at Moen, Dublon Island, and Eten. As this table shows, the greatest 2%— hour fall of rain was experienced during December, lO.hh inches having been received in one instance during that month as contrasted with a maximum of 7.72 inches in June, 7.36 inches in August, and 6.13 inches in November. As will be elaborated upon in the section on storms and squalls, November and December are among the h months when there is the greatest chance of a wide-scale tropical disturbance influencing the weather of the Truk Islands. The very heavy fall of 10.hh inches dur— ing December and several of the other 2h-hour falls in excess of 3 inches in these months were associated with Just such a trOpical dis- turbance. In contrast, high 2h-hour falls, virtually all during the other seasons, were the result of intense shower activity. The available data do not lend themselves to an accurate analysis of rainfall intensity-duration-frequency relationships for the Truk Is- lands. However, it has been possible to construct from the data esti- mated intensity—duration-frequency curves for Qh-hour amounts of rain- fall and for mean return periods of l, 2, and 3 years. These curves certainly have a probable error of no greater than 15 percent as to amount. The points to which the estimated curves were drawn are shown in the figure and were obtained by the simple frequency count method without the usual adjustments, which could not be applied in a direct manner in view of the nature of the data. From figure 6 and the data of table 9 it is possible to form a reasonable Judgment as to the order of magnitude of the rainfall intensities against which it is necessary to guard in undertaking construction work and engaging in other activi- ties in which rainfall intensity is an important factor. The following sample reading is taken from figure 6. Rain falling at the rate of 0.72 inch per hour for 6 hours may be expected once every 2 years. Drought: The dry tradeawind season is clearly the time of real drought threat. This is true not only because of the relatively low rainfall amounts received during this season but also because of the high wind speeds, which maximize the evaporation and transpiration. Pan evapora- tion measurements obtained by the Japanese during l93h-38 give mean evaporation values for the dry trade-wind seasons that are 50 percent higher than the corresponding values for the doldrum season and 35 to ho percent higher than for the wet trade-wind seasons. The actual pan evaporation values obtained by the Japanese indicate that the condi- tions of measurements are at least suspect. Therefore, the absolute values obtained by them are not given here; but the relative values are nonetheless significant. No anaJysis is available, nor was one made, of the frequency of dry periods of various lengths during the dry trade-wind season. Hew- ever, from the data presented in figure 3 it is possible to estimate the frequency of intense drought through considering that less than M inches of precipitation in any one month will yield severe drought at least by the middle of the month regardless of what the rainfall has been in the previous month. This approach is in line with the findings of Dr. E. C. J. Mohr (cited in Schmidt and Ferguson, 1951) whose work was carried out in the East Indies. 33 Table 9. Greatest 2h-hour, 6-hour, and #-hour rainfall by months, Truk Islands l/ (values are for set times of observation only) 2h Years of 6' Years of 4h Years of hour record hour record hour record January h.30 12 1.95 2 1.85 h Fabruary h.06 1h 2.03 2 1.22 A March 1.33 it 1.75 2 2.8L A April 5.13 13 1.12 3 2.82 h May h.h5 13 2.60 3 2.31 1 Jnne 7.72 in 2.82 3 2.00 h July n.56 13 2.01 3 2.10 h August 7.36 1h 2.50 3 3.30 h September h.h9 12 2.h2 3 2.10 h October n.98 11 2.38 2 2.11 h Nbvember 6.13 10 1.65 2 2.50 h December 10.11 1b 8.71 2 2.91 h Annual 10.11 8.71 3.30 l/ Based on records as follows: Daily values from U.S. station on Moan, 1953-1956; daily values from Japanese station on Dublon Island, 1919-1921, 1934-1938; maximum daily values by individual months from German station on Eten, 1905-1913; 6- hour values from U.S. Weather Bureau, Moen, l95h-l956; h-hour valges from Japanese station, Dublon Island, 1919-1921, l93h- 193 . Table 10. Mean number of days with thunderstorms, Truk Islands l/ January Fabruary Nbrch April May June JUly August September October Nbvember December Annual :r F‘ LU no F‘ rd F‘ F' r: * F’ * +4 H l/ Based on U. S. observations, Mben, 1951-1955 and Japanese observations, Dublon Island, 1935-1938. * Less than 0.5. 3h SS 0' O O (inches 'per hour) intensity rainfall Figure 6 ESTIMATED 3 4 rainfall RAIN FALL EXPLANATION Frequency of Occurrence (return period) A ._ ________ __... once every 3 years once every 2 years X once a year Sample determination: A Once every 3 years a rainfall of 0.45 inches or more per hour will last for l3 hours. 5 6789l0 IS 2024 30 duration ( hours ) lNTENSlTY-DURATION-FREQUENCY CURVES, TRUK ISLANDS On this basis a severe drought of at least 2 weeks duration is to be expected about once in 5 years during January; once in 3 years during February; and once in # years in March. These are reasonable minimum figures as to the frequency of droughts that are sufficiently extreme to pose a severe water supply problem where water supply for a population concentration of a few hundred or more is concerned. With rough proba- bilities of this order of magnitude, it appears that it would be unusual for there not to be at least one drought period of 2 weeks or more in duration during any one dry season in any particular year. Also, once every 5 to 10 years there may be extreme drought situations that persist for from h to 6 weeks. The term drought period as used in the foregoing discussion refers to a period during which there are no appreciable additions of water to the streams or to the soil on the Truk Islands, and no additions to open catchments above those that would be lost very quickly through evapora- tion. These figures are all approximate, but serve to indicate the mag- nitude of the water supply problem. Storms and squalls The storms and squalls that are readily recognizable as distinctive weather events in the Truk Island area fall in two classes depending on their size. On the one hand, there are thunderstorms and local squalls whose influence is felt at any one moment over areas of not more than a few square miles. On the other, there are major tropical disturbances, including tropical storms and possible typhoons, whose influence is felt at one time over an area of hundreds or thousands of square miles. Of these two classes of disturbances, the smaller scale ones are of greater significance than the larger scale ones because of their far greater frequency. However, there are very occasional large-scale storms that do have an effect upon the weather at the Truk Islands. That thunderstorms are infrequent at all times of the year is evi- dent from table 10, which indicates that only in October and Nbvember is there more than one thunderstorm on the average in any one month at any one locality on the islands. Even in October and Nbvember, the mean monthly frequencies are less than four. Furthermore, since a thunder- storm is recorded by the meteorological observer whenever thunder is heard, no matter what its distance from the observing point, thunder- storm frequencies at a particular point are even lower than is indicated by table 10. The thunderstorm is therefore a rare phenomenon indeed. When thunderstorms do occur they give rise to local squalls charac- terized by moderate to extreme gustiness, frequent changes in wind di- rections, and heavy showers that are often intermittent. Squalls of this type are not, however, limited to situations that produce thunder. Therefore squalls, though still fairly rare, are somewhat more common than thunderstorms. Squalls occur chiefly over the water areas, where they may occur during any month of the year but are most likely to occur during the doldrum season. Quantitative data are not available, but it is reason- able to suppose that throughout the entire Truk Lagoon there must be squalls on at least 5 or 6 days during each month of the doldrum season and on at least 1 or 2 days each month in other seasons. none of these squalls affects an area of more than a few square miles at any one mo- ment. A few of them travel 10 miles or more across the lagoon before dying out; most travel not more than 5 or 6 miles. 36 (1.. 0 Major tropical disturbances occur chiefly from October through January, but they may occur in other months as well. These disturb- ances are commonly classified on the basis of their intensity in terms of the wind speeds that are produced and the surface air pressure as- sociated with them. In these terms the most mild disturbance is a pres- sure wave that is not sufficiently pronounced to produce a closed storm system or to yield winds that are more than a few miles an hour greater than is average, but that often yield moderate to heavy amounts of rain— fall. More pronounced is the tropical depression, which can be recog- nized on the weather map as a closed pressure system but which still does not yield notably high winds even though, once again, excessive rainfall may result. Tropical storms are closed pressure systems about which the air moves counterclockwise in the northern hemisphere with wind speeds of from 28 to 6% knots (32 to 7% m.p.h.). Typhoons are similar to tropical storms, but with wind speeds of 6h knots (7h m.p.h.) or more. Both the tropical storm and the typhoon commonly yield very high amounts of rainfall. There is no certain record of a typhoon ever crossing the Truk Is- lands or coming close enough to them to influence pronouncedly the weather there. It is true that the Germans reported a typhoon on No- vember 18, 1905 which yielded 5 inches of rainfall at Truk within a 36- hour period. It is dubious, however, that this was a real typhoon in the technical sense that the wind speeds exceeded 6h knots (7h m.p.h.). It is far more likely that it was a tropical storm, with winds of 28 to 6% knots (32 to 7h m.p.h.), or even merely a tropical depression, with still lower wind speeds. This does not mean that it is impossible to experience a true typhoon at the Truk Islands; but the chances of such an experience are so slight, being certainly less than 1 chance in 25 in any one year, that the Truk Islands cannot be said to lie in a true typhoon area. During the 6 years of 19h6-h7 and 1952-55, there were nine weak tropical storms or depressions that passed within a distance of 138 statute miles (120 nautical miles) of the Truk Islands, according to the typhoon reports of the U. S. navy, Fleet weather Central, Guam. During the period l9h0 through l9h5, there were three tropical storms or de- pressions that passed within 138 statute miles (120 nautical miles) of the Truk Islands according to the trajectory maps of the Central Meteor- ological Observatory, Tbkyo. Combining these frequencies, during 12 years there was a total of 12 storms that passed within 138 miles of the Truk Islands. These were distributed by months as follows: two each in June, October, and Nbvember, and one each in January, February, May, JUly, September, and December. In addition there as what appears to have been, from the synoptic weather maps, a distinct tropical wave which occurred in the Truk Islands area December 25-26, l95h and which produced the record rainfall amount of 10.hh inches in 24 hours. This same wave appears to have produced a fall of almost 3 inches in 2h hours on POnape about 2h hours earlier. In checking the dates of passage of tropical storms or depressions .against the rainfall records for the period since 1951, it was found that of the seven storms passing within 138 miles, four were associated with no precipitation at the Truk Islands, one was associated with a 2&- hour fall of 1.25 inches, one with a fall of 2.h8 inches, and one with a fall of 3.08 inches.. Thus, it would seem that not only are tropical storms and depressions rare, but that they only occasionally produce exceptional amounts of rainfall, and this appears to be true despite the very excessive rainfall of December 26, 195%, as already described. 37 The foregoing frequency figures of one tropical storm or depres- sion per year may be slightly too low. Nonetheless tropical storms are certainly not frequent at the Truk Islands nor do they produce anything like the extreme falls of rain and the very high winds that are yielded by them at a later stage of their development when they haye moved far- ther westward into the region of the western Caroline Islands and be- yond. Topics of special interest Two topics of special practical interest warrant brief comment even though these topics can be treated only in a general descriptive manner. These topics are climatic conditions as related to comfort and variations in microclimatic conditions. Applying the standards that have been given by Robert G. Stone (19%), the climatic conditions at the Trek Islands would be found to be comfortable so far as nighttime temperatures and humidities are con- cerned by 50 percent or more of those individuals who come from the continental United States. Furthermore, in time, through acclimatiza- tion, all or virtually all these individuals would find the nighttimes to be quite comfortable at all times of the year. As for daytime conditions, only during the doldrum season would virtually all the individuals from the continental United States find the weather to be unpleasantly oppressive. During the tradeawind sea- sons between one-third and one-half of them would find the conditions oppressive in the daytime. Again, there would be a change with accli- matization. It would be expected that virtualky all of the individuals would within a few months find the weather of all three tradeawind sea- sons to be perfectly comfortable in the daytime as well as the night; and one-half of them would, within a few months, find the weather to be comfortable even in the daytime during the doldrum season. As regards the microclimates of the islands, those features re- lated to elevation and exposure have already been discussed in connec- tion with wind conditions, cloud, and rainfall. There are, however, the additional influences of the vegetative cover. From a series of comparative measurements made on the island of Penape, it is clear that temperature differences at a height of 5 feet between the air beneath a forest canopy and that above a field of grass will be 2° to 5° F. during the daytime, the precise difference depending upon the amount of sunshine, the wind conditions, and the density of the forest canopy. The most extreme temperature differences will occur on a sunny day with relatively little wind and when the forest canopy is dense. However, even on a cloudy day with a wind of 10 to 12 m.p.h. the temperature above a field of grass will be 2° or so higher than beneath a forest canopy. Similarly, there are slight but real differences in the humid- ity of the air as between grassland and forest. In all instances the humidity is higher within a forest and in extreme instances the differ- ences in relative humidity between forest and grassland are as much as 25 percent. 6 References Central Meteorological Observatory, no date, Trajectories of tropical cyclones 1940-1950: Tfilwfi, Japan. [In Japanesg7 , 1951+, Climatic records of Japan and the far east area: 16%, Japan. [in Japanesg7 East Asia Research Institute, 19112, East Asia meteorological data: v. 6, Japan, Central Meteorological Observatory, Tokyo, Japan. [in Japanese] Japanese Meteorological Agency, Original observational records Dublon Island, Truk Islands, 1919-1921 and 1931:4938 (unpublished). [in Japanesg7 List, R.J. (editor), 1951, Snithsonian meteorological tables: 6th ed., Washington, D.C. Mitteilungen von Forschungsreisenden und Gelehrten aus den Deutschen Schutzegebieten: Band 18, heft l. 1905; Band. 19, heft 1+, 1906 3 also 1907-1908 and 1909-191h. [In GermaI_17 Schmidt, F.H., and J .H.A. Ferguson, 1951, Rainfall types based on wet and dry period ratios for Indonesia with western New Guinee: Kementerian Perhubungan DJawatan Meteorologi dan Geofisik, Verh. 1+2, Djakarta, Indonesia. South Sea Bureau, Meteorological Observatory [Japan], no date, Annual reports, Palau, West Caroline Islands (various years). [in Japane s27 Stone, R. G., 1941, Health in tropical climates, in Climate and Man, U.S. Department of Agriculture, Yearbook of Agriculture l9hl, p. 21-16-261, Washington, D.C. Tallinan, Hubert, 1936, Die Niederschlagsverhflltnisse der Sfldsee-Inseln: Archiv der Deutschen Seewarte, Band 56, nr. 5, Hamburg, Germany. [in German] U.S. Department of the Air Force, Anderson Air Force Base, 1952, 5th annual report, typhoon post-analysis board: Agana, Guam. U.S. Department of Commerce, Weather Bureau, no date, Original obser- vational records, Truk Islands (unpublished). , l95h-l956, local climatological data (W): Washington, D.C. U.S. Navy Department, Chief of Naval Operations, Aerology Section, 19%, A climatic smmnary of the Caroline Islands: NAVAER 50-IT-h, Washington, D.C. U.S. Navy Department, Fleet Weather Central Guam, 1952—1955, Annual typhoon reports: Agana, Guam. U.S. Navy Department, Pacific Fleet Air Force, Meteorological Squadron One, 1916, l9h7, Typhoon reconnaissance of 19%, of l9h7: Agana, 39 Oceanography and Special Geophysical Phenomena by Richard L. Hay Tides and currents The range of tides in the Truk Islands is usually small. The aver- age tide range is 1.5 feet at Dublon Island and 1.6 feet at Mben. The tropic range, which is the increased diurnal range occurring semimonth- 1y when the effects of the moon's maximum declination is greatest, is 2.0 feet at Dublon Island and 2.1 feet at Mben. The maximum tide is approximately 3 feet. Tides generally occur twice daily except when the diurnal inequality is greatest and there is but one. The following data are taken from Sailing Directions for the Pa- cific Islands (U.S. Navy Department, Hydrographic Office, l9h5). Cur- rents in the lagoon are variable. Available observations indicate northerly sets, with drifts of from one-half to 1 knot (0.58 to 1.15 miles per hour). Nbrth of Truk sets are generally northerly, tending to northwesterly. Observations to the south and east of Truk show a northeasterly set. Within the lagoon, currents are complicated, tend- ing to bend around the islands, but seldom exceed one-half knot (0.58 miles per hour). The barrier reef of Truk is breached by a number of passes, and the tidal currents of some have been recorded. The most important, reading clockwise from the north, are Nbrth Pass, northeast Pass, Salat Pass, Otta Pass, Minami-suido, and Piaanu Pass. Nbrth Pass: H. 0. Chart 60h7 (U.S. Navy Department, Hydrographic 0f- fice, 195Ec) indicates that North Pass has been swept for mines to a depth of 55 feet over a width of about one-half mile; the general depths are over 20 fathoms (120 feet). The flood current sets south- ward through the pass with a velocity of 1 3/h knots (2.02 miles per hour). The ebb sets northward with a velocity of three-fourths knot (0.86 miles per hour). Nbrtheast Pass: H. 0. Chart 6051 (U.S. Navy Department, Hydrographic Office, 1935f) shows that Northeast Pass has been swept to a depth of 59 feet over a width of 200 yards (600 feet). Other areas in the pass were swept to depths of 27, 37, and 55 feet. General depths of the pass are from 10 to over 20 fathoms (60 to over 120 feet). The flood current sets southwestward through the channel with a velocity of 2 knots (2.3 miles per hour). The ebb sets northeastward with a velocity of l l/h knots (l.hh miles per hour). It is reported that northeaster- ly winds send a heavy swell through the pass, and the current may reach 5 knots (5.76 miles per hour). Salat Pass: H. 0. Chart 60h8 (U.S. Navy Department, Hydrographic or- fice, 19HEd) shows that the pass, a narrow one, has been swept to depths of 55 feet, and the pass has depths of over 20 fathoms (120 feet) in midchannel. The flood current sets northward through the pass with a velocity of 2 3/l+ knots (3.17 miles per hour). The ebb sets southward with a velocity of 2 l/h knots (2. 59 miles per hour). Otta Pass: This pass leads through the reef about three-fourths mile west of Otta island. It has general depths of 7 to 9 fathoms (#2 to 5h feet) in midchannel. H. 0. Chart 601:8 (U.S. Navy Department, Hydrogrsph- ic Office, 19hhd) indicates that it has been swept to 39 feet over a width of about 700 yards (2,100 feet). There are no tidal data availa- ble for the pass. hl Minami-suido: H. 0. Chart 6051 (U.S. Navy Department, Hydrographic Office, 1933f) shows the pass to have a charted depth of 21 to about 28 fathoms (126 to 168 feet). The flood current sets southwestward out of the pass with a velocity of 1 1/2 knots (1.73 miles per hour). The ebb sets northward with a velocity of l knot (1.15 miles per hour). The Sailing Directions do not recommend Minami-suidd. Piaanu Pass: H. 0. Chart 6019 (U.S. Navy Department, Hydrographic Office, l9Ehe) shows the western entrance to the Truk Islands is over 1 mile wide between the edges of the barrier reef on the south and the submerged coral reefs on the north. There are charted depths of 16 to 2h fathoms (96 to lhh feet), and a least width of 1,800 yards (5,hOO feet) has been swept to a depth of 59 feet. The flood current sets westward out of Piaanu Pass, and the ebb sets in a general easterly direction through the pass. The velocity is one-half knot (0.58 miles per hour). Further information on pass locations, depths, and general usabil- ity can be obtained from the Sailing Directions for the Pacific Islands (U.S. Navy Department, Hydrographic Office, 1935) and from Hydrographic Office charts. Tides are summarized in Tide Tables, Central and west- ern Pacific and Indian Oceans (U.S. Department of Commerce, Coast and Geodetic Survey, 1955). Waves and surf The waves within the Truk Lagoon reach their greatest height dur- ing the dry season, January through March. The wave pattern follows the contours of the various islands, flowing around them and combining with other patterns. The result of the wave movement is a choppy pat- tern which often makes navigation difficult. wave heights seldom ex- ceed 7 feet. During January and February on windy days, travel is safe only in larger small craft or very seaworthy small boats. local inhab- itants report that the most dangerous lagoon area during windy days is east and south of Udot, in the central part of the lagoon. The experi- ence of the author indicates this statement to be generally true. lbunami There is no known occurrence of tsunami, or high water, following stonms which caused damage on the inner islands, and it is believed that the wave energy is expended in crossing the outer barrier. In re- cent years the outer inhabited reef islands have experienced no diffi- culty with tidal waves, and the l9h6 tidal wave which swept the Hawai- ian Islands was reported only as high water rising about 4 feet higher than the highest normal tide. A few taro patches were flooded on the reef islands (U.S. weather Bureau, Truk Islands, personal communica- tions . Earthquakes The Truk Islands lie in a part of the Pacific Ocean that is today structurally stable and there probably has been no volcanic activity in these islands since the beginning of Pleistocene time. Nb earthquakes have been reported from Truk and, because no geologic evidence suggests faulting of Recent age, the possibility of future earthquakes is very slight. Topography by Richard L. Hay General statement .The Truk Islands include low coral islands and high volcanic is— lands in a large lagoon encircled by a barrier reef, upon which lie other low coral islands. There are 19 islands and islets of volcanic rock and about 65 coral islands, approximately two-thirds of which lie on the barrier reef. Total land area of the Truk Islands is approxi- mately 35 square miles (91 square kilometers) including salt-water man- grove swamps; of this, 33.8 square miles (87.5h square kilometers) are found on the volcanic islands within the lagoon. The volcanic islands range from low islands less than 10 feet (3 meters) above sea level to islands having maximum elevations between 1,000 and 1,500 feet (between 300 and #50 meters); areas range from about an acre on the smallest is- let to about 10 square miles on the largest island. Nanmade topographic features are widespread on the Truk Islands. The largest proportion are Japanese fortifications and installations. The American occupation has added one-story sheet-metal houses and office buildings in a settlement on northwest Moen. The Trukese have chiefly built small flimsy dwellings and small coral jetties. Volcanic islands Table 11 gives the areas and the maximum elevations of the vol- canic islands. See figure 1 for island locations. Upland areas: The high islands, exclusive of Yanagi, Atkin, and Tako, comprise both upland and lowland terrain of very different character. The upland terrain, on volcanic rock, is generally rugged; the lowland is largely swamps, marshes, beaches, and raised-beach deposits, all of which are less than 3 feet above high-tide level. The larger high is- lands have very irregular shapes. Tbl is most irregular and is indent— ed by four large embayments which nearly separate the major upland blocks into four islands. Both Mben and Dublon Island are indented by embayments. All seven of the large islands except Udot are asymmetric in profile. The east slopes of Mben and Dublon Island are gentlest, as are the south lepes of Fefan and uman. The slopes of Mbunt Tumuital are gentlest to the southwest. The upland terrain includes hills, ridges, scarps, and flat to gently sloping areas. Most of the upland terrain has slopes steeper than 30 percent, which generally become steeper upward to form steep- faced peaks and relatively sharp ridgecrests (pl. h A); however, some peaks and ridgecrests have relatively flat summits (pls. 3 and h B). Twelve peaks have elevations exceeding 800 feet (2hh meters); the high- est3 Mount Thmuital on Tbl, is about 1,h53 feet (#43 meters) high (pl. 5 A . Vertical and near-vertical scarps are widespread on the six larg- est volcanic islands, but are less common on the smaller islands. Scarps range from ledges 5 feet high and 25 or more feet long to cliffs 150 feet high and as much as a mile long (pl. 15 B). Mbst common are scarps from 25 to 50 feet high and several hundred feet long (pl. 5 B). #3 Table ll. Areas and elevations of the Truk Islands Total Area less area (in mangrove Maximum elevation (in square swamps (in feet) and peak name Islands miles) square miles) where known Eastern group Mben 7.19 6.h9 1,22% Mount Tbroken (Chukumong) Falo 0.13 0.13 165* Yanagi < 0.01 < 0.01 15* Dublon Island 3.39 3.17 1,125 Mbunt Tolomenl/ Eten 0.19 0.19 200 Mount Uinku Fefan h.68 h.06 995 Mbunt Iron Param. 0.h9 0.h9 177 Tarik 0.18 0.18 lh8 Tsis 0.22 0.22 220 Winipou Oman 1.55 1.h2 896 Mbunt Uroras Faneu 0.01 0.01 75* Tako < 0.01 < 0.01 10* Atkin IOO‘ x “”300 ' . N j lllllllll olivine basalt (poorly exposed) v ———————— -— a roximate contact — zoo llllllUllllll osolt P" c 50_ o u auobrecma o _ mm) ll olivme basalt . z _ 000:1. l'vine basalt autopreccm g j '00 LEQJJ‘LUUJL--Q-L~~,—ar\iproximate contact % d AAAA lpyroclastic breccm [5100 20100 feet I I I I I T I I I I I I I I I T I I I I I I I I I I I T I l I I T ICC 200 300 400 500 so 700 meters A distance A’ Figure 7. GEOLOGIC SECTION, CHUKUWbN, MOEN Blank areas are undivided volcanic rocks. Summit elevation 24I meters or 790 feet. See map 6 for location. U) L Q) o- 4' Q.) 0.) e 4‘.’ 3001 ,~ :esoo S - -— 250— *5 r800 trachyte ‘- _ O a. _ g- _~7oo —————— approximate contact x 200— m u _-600 8 : llllllll andesite (poorly exposed) ”{- ISO-"“500 m _ > - x ——400 no- outobreccia - H ande5ite 9’, I00— autobreccio —~3oo S _ . .fif autopreccm ; wgoo MHHIifli andesne g 50— 2 _ ‘” : llllllll andesite (poorly exposed) *_Iflll_ andeSIte approximate contact 20100 feet III I I l l I I ' I l I I l I I I I I I l I II II IT IOO 200 300 400 so 600 meters D distance D’ Figure 8. GEOLOGIC SECTION, me'oN, MOEN Blank areas are undivided volcanic rocks. Summit elevation about 270 meters or 886 feet. See map 6 for location. 56 LQ 2 92 s Q) E 33 :t—IZOO 350— —Iioo lllllllllllll olivine basalt (poorly exposed) _ lllllllllll olivine basalt ( poorly exposed) g3oo__|000 I _ § 2—900 IHlllllllHl olivine basalt (poorly exposed) U’ - . . c» _ olivme basalt 3 250 r800 m fl H+HH+HHW autobreccuo a, y olivme basalt (poorly exposed) E 4—700 Illllllllll olivine basalt (poorly exposed) ._ 200— ‘- - olivine basalt 5 r600 , . . ,(DHHHU' autobreccna ’ - basalt x '_ N (50: 500 c L400 Illlllllll ,andesite (poorly exposed ) O c . f, loo— 30° IIIIIIIIIIHI andesute ( poorly exposed) i, : andesite ‘1’ L200 —————— approximate contact 5°: AAAA pyroclastic breccia (morly exposed ) : 500 l 0100 I 5100 aoPo 25100 30100 35‘00 40'00 feet lTlllTl'IrllIlllYlIITlli'lllerlll‘lllrl'llirl'IlllerTlll'V‘ITllIll I00 200 300 400 500 600 700 890 900 I000 “00 1200 I300 meters B distance 8’ 3” Figure 9. GEOLOGIC SECTION, MOUNT TEROKEN (CHUKUMONG), MOEN Blank areas are undivided volcanic rocks. Summit elevation 373 meters or I,224 feet. See map 6 for location. 89 meters 3501 l ) 0' o o l exaggeration N 0t 0 I 1 1 (2x vertical elevation feet :-|lOO —IOOO —SOO -800 F700 l-600 '500 -400 IHHHH “mum ondesite lllllllllll andesite lllllllll IIHHIIIII 0ndesi‘fe |l||l||||| ondesite (poorly exposed) andesite approximate contact Jill pyroclostic breccia or conglomerate (poorly exposed) l||||||ll| olivine basalt (poorly exposed) umnm basalt (poorly exposed) ondesite (poorly exposed) ondesite (poorly exposed) andesite (poorly exposed ) meters alt 590 IQPO Isoo 2989 2590 3q00 3590 feet I I I I I I I I I I I l I I I T T ‘l 1 l l I r I I I II I T I I I I I l I I [T I I l l I l I I‘T l I I l l TI’l—I ICC 200 300 400 500 600 700 l 800 900 IOOO IIOO IZOO C distance 0’ C” Figure )0. GEOLOGIC SECTION, WINIFOURER, MOEN Blank areas are undivided volcanic rocks. See map 6 for location. Summit elevation about 345 meters or I,I 32 feet. 5 Quarry in andesite, Moen. Looking south at face of quarry in lower part of andesite flow on northwest Moen. Columnar jointing is conspicuously displayed; columnar blocks are 2 to 3 feet in diameter in lower part of flow but narrower columns are visible at top. The quarry face is an unusually good exposure of engineering mate— rials Unit 1. 195u—55. Plate 13 few irregularities due to channelling and the uneveness that might be expected from the variations in thickness of the flows. An attempt was made to measure the attitude of the flows exposed in steep escarpments with aneroid barometer readings along the outcrops. A general dip di- rection of northeast and possibly east is indicated. The attitude of the upper trachyte flow capping Witian (pl. 3) is not apparent due to erosion of the top part of the flow and lack of basal exposures, but it appears to strike northwest and dip approximately 2 l/2° NE. One ex- tremely porphyritic basalt flow, mapped for a distance of 1 mile on the north side of Mben, strikes N. h5°W., and dips 3° to 3 l/2° NE. Numer- ous andesite flows exposed on the southern sides of Mount Teroken (mapped as undivided) and Witipéin dip 2° to 2 1/2° E. If the conglomerate exposed at an elevation of approximately 350 feet on Tanaachau correlates with the thick breccia unit 1 mile to the southeast, in the Wichen River valley, then the breccia strikes approx- imately north-south and dips 3 l/2° E. However, as the differences in elevations are small and the suggested correlation may be erroneous, the attitude of the pyroclastic unit is probably not as reliable as that of the porphyritic basalt flow. Faulting on Mben has been extremely rare or, if it occurred, the evidence is now largely concealed by soil and vegetation. At only one locality on Mben is the field evidence strongly suggestive of faulting. An outcrop of andesite half a mile long and 500 feet wide is exposed on the northern tip of the island, adjacent to Mben Airfield. The andesite has been quarried for road material and a vertical section of the lower part of the columnar-Jointed andesite flow is exposed in 80-foot bluffs of fresh rock (pl. 13). The flow rests on a boulder and cobble con- glomerate. Traced laterally, the andesite appears to end abruptly a- gainst olivine basalt flows, although the actual contact between the two lavas is obscured by erosion, vegetation, and soil. Near 350 feet elevation, upslope and southward from the quarry, there is another out- crop of andesite resting on conglomerate. The contact is well exposed along an old Japanese road and in several caves excavated for gun in- stallations. Both of these conglomerate outcrops are composed of cob- bles and boulders showing rounding by water action. The conglomerates and their relations to the overlying andesite flows are strikingly similar in both outcrops. A normal fault with relative movement down- ward of the north block approximately 350 feet would explain the field relations, but actual trace of the fault surface or zone is not exposed. A cave at the west end of the lower andesite outcrop shows highly shear- ed and weathered rock along fracture planes and may represent shatter- ing due to faulting. However, local shearing in weathered autobreccia of the lava flows is evident in a number of caves throughout Mben and Dublon Island. Because of the absence of conclusive evidence for fault- ing here and the fact that at no other place on Mben has evidence for major faulting been found, the fault is shown on the geologic map (map 5) as probable rather than certain. An alternative explanation to faulting is that the lower flow may represent a steep-walled-valley filling. This interpretation receives possible support from the difference in chemical composition of the flows, the upper flow being an andesine andesite not far from basalt and the lower an oligoclase andesite; and also from the absence of simi- lar faulting elsewhere and the occurrence of steepawalled valleys and even canyons filled with lava tongues on southwest Mben, and the unusu- ally great thickness of the lower flow - a feature characteristic of valley-filling flows. 59 ) The source of the Moen lavas can only be inferred as no dikes or vents have been found on the island. The general northeast dip of the lavas suggests a source to the southwest. This is supported by the northeast trend of valley-filling lava flows at the southwest end of Moen. The uncOnformity inferred between nonporphyritic andesite and porphyritic basalt flows on Mount Teroken (Chukumong) and Winifourer also suggests a southern source for the upper porphyritic lavas. Falo: Falo is a small island 1 1/2 miles north of Mben (pl. 7 B). It consists of an upland area, chiefly olivine basalt flows, as much as 160 feet high surrounded by patches of fresh-water marsh deposits and calcareous beach sands. At the southwest end, in the lee of the island ridge, the beach sands cover an area approximately one-quarter of a mile squared (map 5). The basalt flows are well exposed in cliffs on the north side of Falo and in separated outcrops on top of the ridge. They vary in tex- ture from massive and even grained to porphyritic with abundant olivine phenocrysts. No observations on dip were made but, from their proximi- ty to Mben and their similarity in composition to some Mben basalt flows, a similar gentle northeast dip is probable. Yanagi: Yanagi island, 500 feet long and half as wide, lies ap- proximately halfway between Moen and Dublon Island. It rises about #5 feet above the fringing reef and is composed entirely of coarse pyro- clastic breccia. Blocks of andesite and basalt lava as much as 3 feet in diameter are embedded in a fine-grained matrix of the same composi- tion. The lava blocks are similar in composition to flows on Moen and Dublon Island. No indication of the attitude of the breccia was ob- served (map 6). Dublon Island: Dublon Island is next to Mben in complexity of to- pography and geology (maps 6 and 7). Detailed traverses across the four prominent peaks - Mbunt Tblomen, Foukenau, Mbunt Uhimakur, and Mbunt Urikobosu - show no agreement in the sequence of flows and inter- bedded pyroclastic deposits. Isolated outcrops of andesite and basalt in the western half of the island are widely separated and over three-fourths of the area is mapped as undivided volcanic rocks. On Mbunt Tolomen, the contact be- tween the base of an andesite flow and the autobreccia of the flow be- low is exposed at 865 feet (26h meters) on the west side of the moun- tain and at 750 feet (229 meters) on the east side. These aneroid measurements at extreme west and east ends of the outcrop indicate a dip of at least 3 1/2° E. On the less dissected uplands of the two peninsulas extending in a general northeast direction, basalt and andesite cover the crests. At the western end of the northern peninsula, there is an outcrop of a nepheline basalt flow. This outcrop is unique in the eastern islands; the only other outcrops of nepheline basalt in Truk are on T01 and Ulalu in the western group. The nepheline basalt flow on Dublon Island is of special interest because it is stratigraphically below a series of basalt and andesite flows in contrast to the nepheline basalt flows of the Hawaiian Islands which occur as the uppermost and last phase of thi volcanic activity (NacDonald, 1953; Stearns, l9h6; and Winchell, l9 7 . (n \— 2 2;, ° m E u- A 250 andesite c >800 li'ii'iL'JU' outobreccio .9 — CW olivi'ne basalt E -~700 cong omero e 3200: _-:—:—: tuff g rsoo X _. Q) _ l50"5°0 D .9 - . . t $400 llllllllll olivme basalt (poorly exposed) g) _ 100— x -—300 N _ 4—200 8 50d -- ‘ lllllll olivine basalt ‘c; : "' outobreccaa % ~ soc IOIOO I500 feet I l l l I l l l l I I T T l I l T , T I I I l T’j IOO 200 300 400 500‘ meters E distance E’ Figure ll. GEOLOGIC SECTION, FOUKENAU, DUBLON ISLAND Blank areas are undivided volcanic rocks. Summit elevation 24? meters or 8|O feet. See map 6 for location. U) \— +3 1;, A E :3 C 2604—200 0 L Q) . . 350— olivme g —l50 basalt CD 4o~ D '9 __AA“A.A lopilli tuff grading into E, 30—‘l00 _._I:ti:.;-‘;_: pyroclastic breccio > :1:::1:3:::1:3:3:3 xzo— UH“ basalt E” _50 A; _ —— tuff and breccio //, // minor unconformit c to— contOrted interbed ed lava, tuft, and .9 // breccio Cut by breccia- filled crevices 2;, / 490 590 690 too 890 feet a, I l l T l I l l l l l l 3 20 40 so so IOO l20 l40 l60 160 200 ago 240 meters F distance F’ Figure I2. GEOLOGIC SECTION, MOUNT UlNKU, ETEN See map 7 for location. 61 The thick porphyritic flow of basalt forming the eastern part of the northeast peninsula (from the Mount urikobosu area to Kntua Point) strikes approximately N. 30° W. The dip varies considerably but aver- ages h° NE. Several scarp faces on Dublon Island show the scarp-form- ing flows have a gentle eastward dip direction. Near the crest of Foukenau, a 12-foot bed of lapilli tuff is suc- ceeded by about 100 feet of undivided volcanic rocks, 8 to 10 feet of conglomerate, about 50 feet of basalt and is capped by andesite (fig. 11). The conglomerate is composed of well-rounded cobbles and boulders, as much as h feet in diameter, indicating local modification of the volcanic fragments by water action. In its composition and relation- ship to the overlying andesite flow it resembles closely the Moen con- glomerate on Tanaachau. Although the breccias on Dublon Island also re— semble those on Mben, nowhere was a breccia unit found to be as thick as the thickest on Moen (300 feet). A dike of andesite cutting an olivine basalt flow crops out along the road at the west side of Dublon Island. The dike is 15 feet wide, strikes N. h0° W. and dips 52° NE. A source of the lava flows and explosively ejected pyroclastic ma- terial to the west of Dublon Island, between Mben and Fefan (fig. 15), is suggested by the directions of dip on these three islands. The spotty distribution of outcrops on Dublon Island may be explained by the tonguelike shapes and lenticular nature of successive lava flows, by channel fillings, and by erosion between eruptions of pyroclastic material. In the western half of Dublon Island, dominated by the peaks of Mbunt Tblomen and Foukenau, the distribution of outcrops is extreme- ly spotty with little or no correlation between exposures. Where the uplands trend in the direction of the flow dips, as on the northeast peninsula, the outcrops are more continuous, representing the same flow for three-quarters of a mile along the direction of dip. The southeast peninsula is composed largeLy of basalt flows with fill and small expo- sures of andesite near the west end. Eten: The small island of Eten (map 7), Just half a mile south of Dublon Island, is about h,000 feet long in a northeast-southwest direc- tion and 1,500 feet wide. Reclaimed land forms most of this island, but volcanic deposits form a hill, Mbunt Uinku, about 200 feet (61 me- ters) high on the south side of the island and a small knoll 15 to 20 feet above sea level at the east end. Mbunt Uinku is composed of conglomerate, basalt flows, and pyro- clastic deposits. Conglomerate, consisting largely of water-rounded cobbles and boulders, is exposed at the base of the southwest end of the hill. The eroded surface of the conglomerate is overlain by a ba- salt flow extending almost the entire length of theisoutheast side of the hill. This flow is at least 50 feet thick at the south end of the hill; 100 yards to the northwest the flow thins to several feet. Simi- lar basalt - probably the same flow - is exposed for about 1,000 feet along the northwest side of the hill. Volcanic breccia and lapilli tuff with interfingering flows of olivine basalt form the remainder of the hill. The pyroclastic deposits range from lapilli tuff in which most of the fragments are less than 0.h inch (1 centimeter) in diameter to breccia consisting of blocks as much as 6 feet long. An excellent section of weathered lavas and pyroclastic deposits (fig. 12) is ex- posed on the northeast end of Mbunt Uinku. Here lapilli tuff and vol- 62 canic breccia are interbedded with several lava flows. Although most of the fragments in the lapilli tuff are less than an inch in diameter, blocks of lava as much as 3 feet in diameter are sparsely scattered in the lapilli tuff. The lava flows and pyroclastic deposits in the lower 25 to 30 feet of the sequence are contorted and have near-vertical dips; the lavas are fractured and crevices are filled with breccia. The de- formation was very possibly due to mud flow of the lower deposits prior to deposition of a nearly horizontal tuff and breccia bed which over- lies the contorted lava flows and pyroclastic deposits. The Small hill of volcanic deposits at the east end of the island consists of about 10 feet of pyroclastic breccia overlain by 5 to 10 feet of basalt. The attitude of the volcanic deposits on Eten is difficult to de- termine as no unit could be mapped extensively. However, a 20-foot- thick flow cropping out for 300 feet on the north central side of Mount Uinku has a dip of approximately 5° NE. The thinness of most of the lava flows and the coarseness of the breccia in some lenses suggest a source nearby. The lack of water stratification of the breccias and lapilli tuff suggests an eruptive rather than a detrital origin; the thickness suggests a local source. A source to the southwest or west is suggested by the northeastly dip of one lava flow. Suggestive of a source to the south or southwest is the pinching out of the valley-filling lowest basalt flow toward the west and northwest. Fefan: The geology of Fefan is simpler than that of Moen or Dublon Island. The island is a continuous mountain ridge with four prominent peaks. Mangrove swamp fringes most of the volcanic upland but lowland marsh deposits and beach sand occur locally. Basalt flows, most of which are very prophyritic, greatly predominate over andesite flows on Fefan. On the northwest side of Mount Iron a 1,000-foot-thick section of interbedded basalt and andesite flows is well exposed (maps 6 and 7 and fig. 13). The thickest single flow observed on Fefan, a porphyritic olivine basalt at an elevation of about 150 feet on the northwest part of the island, forms an 80-foot cliff but neither the base nor the top of the flow is exposed. A porphyritic olivine basalt flow, at 330 feet elevation, forms a 50-foot cliff in which columnar jointing is poorly developed; widely spaced irregular fractures produce blocks as large as 10 by 8 by 5 feet. Four separate basalt flows are mapped in continuous outcrops ranging from three-quarters of a mile to l l/h miles in length. These occur on the north side of Mbunt Iron, the east and west sides of Chukuchap, Chukusou, and Winifouno mountains. TWO separate andesite flows are mapped, one near sea level along the west central part of the island, and one on the crest of Winifouno (maps 6 and 7). A small outcrop of pyroclastic rock is exposed below one of the basalt flows on the west side of Chukusou mountain. Here a l-foot-thick bed of volcanic tuff rests on autobreccia of the undivided flows and grades upward into an 8-foot-thick bed of pyroclastic breccia which contains angular blocks as much as h feet long. The attitude of the Fefan flows shows a persistent dip to the south. The elongated outcrops of slightly porphyritic basalt on the east and west sides of the island strike east-west and dip from 1° to l l/2° 3. (map 7). A highly porphyritic basalt flow on the northwest 63 V9 (2X vertical exaggeration) elevation *- O Q) q,— 3oo—_*'°°° |||||| basalt I~9oo ‘ Illlllllllll basalt (poorly exposed) 250— . . reoo lllllllllll olivme basalt (poorly exposed) i—7oo . 200_ ummm andeSIte (poorly exposed) ’600 llllllllllllll basalt float moi—50° andesite (poorly exposed) 3—400 . . _ olivme basalt loo— autobr ccia -—soo andesu e :_200 olivine basalt 50— “ andesite (poorly eLposed) ”>100 20100 25100 3090 35100 40100 4.300 feet I I I I I I I I I I I I I l I I I I] I I I I I I I I I l I T I I Tfll [I l I l I I I I I T I l l I I I I I I r I I I ICC 200 300 400 500 600 700 800 900 looo I too |200 (300 I400 meters 6 distance 6’ Figure I3. GEOLOGIC SECTION, MOUNT IRON, FEFAN Blank areas are undivided volcanic rocks. Summit elevation 303 meters or 994 feet. See maps 6 and 7 for location. (9 corner of the island apparently dips more steepLy southward; neither the top nor the bottom of the flow is exposed. No evidence of dike intrusion or of faulting was found. Param: Earam.consists of a number of deeply weathered lava flows bordered by fresh-water marsh deposits, calcareous beach sand and, on the southern side of the island, by reclaimed land formerly used as an airfield (map 7). Scattered exposures of fine-grained andesite and porphyritic basalt crop out in roadcuts and small excavations on the north side of the island. Four or more lava flows were observed in the sequence on the east end of the island, where borrow pits afford rather good exposures. At the base of the sequence is a weathered porphyritic lava, probably ba- salt. Slightly porphyritic platy basalt crops out at elevations from #0 to 50 feet. This basalt is overlain by 20 to 25 feet of weathered, vesicular, amygdaloidal, porphyritic autobreccia, which is in turn overlain by weathered porphyritic basalt (probably olivine basalt) of which ho feet are exposed. No outcrops are visible above the olivine basalt to an elevation of 177 feet (5h meters), the highest point on the island. However, abundant float blocks of fine-grained andesite above the basalt indicate that an andesite flow almost certainly forms the uppermost rock of Parana Tarik: Bedrock exposures on Tarik are rare (maps h and 7). The sides and crests of the eastern, central, and western peaks are covered with loose blocks of basalt. Different textures in the blocks, from fine grained and massive to abundantly porphyritic, suggest more than a single flow. Two outcrops are exposed near sea level in the east cen- tral part of the island. For a distance of nearly 300 feet along the shore a vesicular highly weathered flow is exposed, and 10 feet upslope a fine-grained porphyritic basalt crops out in a small ledge. The top and bottom of the ledge are not exposed and the eroded surfaces of the vesicular flow at tide level obscure any indications of dip. Tsis: The island of Tsis, Just southwest of Fefan, is composed chiefly of porphyritic olivine basalt flows, fringed on the north by fresh-water swamp deposits and calcareous beach sands (map 7). Expo- sures are not continuous enough to map the flows separately. On the middle slope of the southwest end of Tsis, a spring horizon occurs on tOp of a vesicular flow. The apparent direction of dip at this small lava outcrop is S. 25° E. The surface dip of the flow varies from 1 to 6 degrees, and probably represents erOsion rather than the dip of the flow. Uman, Tako, and Atkin: Uhan is a conical mass of volcanic rock rising to a central peak, Mount Uroras, 895 feet (273 meters) above sea level (map 7). The island is 2 miles long in a north-south direction and 1 mile wide. Several small peaks occur around the lower slopes. Areas of mangrove, fresh-water marsh deposits, and calcareous beach de- posits occur on the north, east, and south coasts. Only basalt flows have been found on uman; andesites, if present, form a very small por- tion of the sequence. One h-foot-thick bed of breccia was found. In two outcrop areas of olivine basalt on the lower southern slopes, the rocks of both are porphyritic, but a difference in plagioclase suggests that the two outcrops represent different flows. A basalt flow with abundant olivine phenocyrsts is exposed in a bluff on east central uman. Nb dip is apparent. The thick basalt flow on southeast uman appears to 65 be dipping very gently to the south, but the top and bottom boundaries are not exposed. On southeast uman, a fault with a vertical displace- ment of 5 to 10 feet is suggested by an unusually straight valley and a difference in elevation of the benchland surface on either side of the valley. The two small islets of Tako and Atkin, 900 feet south of Uman, are surrounded by coral reefs continuous with the fringing reef of Uman (map 7). Tako, 200 feet long, and Atkin, #00 feet long, rise 10 and 8 feet, respectively, above sea level. The islets are composed of porphy- ritic olivine basalt and probably represent the same flow, as the ba- salts of both islands show well-developed columnar Jointing and are simi- lar in composition. Faneu: This is a nearly circular island about 2 miles south— southeast of uman (map 7). It is about 250 yards in diameter and con- sists of a hill of volcanic rock approximately 75 feet high fringed by a sand beach and older beach deposits. The volcanic hill is about 200 yards in a north-south direction and 100 yards from east to west. Auto- breccia is exposed several feet above sea level in the base of a torpedo cave on the south side of the island. The autobreccia is overlain by a columnar-jointed basalt flow, the columns of which are 3 to h feet in diameter. The lower 5 to 10 feet of the flow are sparsely porphyritic; this grades upward, through a thickness of several feet, into very por- phyritic lava, 30 to ho feet thick. Above this, and capping the hill, is a sparsely porphyritic lava resembling the lower 5 to 10 feet of the basalt flow. The contact of the very porphyritic lava with the capping flow was not found. Central islands: The central islands of Udot, Bot, and Eiol are charac- terized by a dominance of pyroclastic breccia and by many dikes. The pyroclastic deposits, dikes, lava flows, and autobreccias of Udot and Eot differ from those elsewhere on Truk. Pyroclastic deposits: Coarse pyroclastic breccia greatly predomi- nates over other pyroclastic types, but a tuff matrix of fragments less than 0.16 inch (h millimeters) in diameter is locally abundant enough to form tuff-breccia. Mbst coarse fragments in some other beds are less than an inch in diameter; this rock is properly termed lapilli-tuff. All pyroclastic deposits consist of angular to subangular, and rarely rounded, fragments of rock in a fine—grained tuff matrix. In the brec- cias most coarse fragments are between 1 and 12 inches in diameter, but blocks as long as 6 feet have been found. Some breccia consists almost entirely of blocks 1 to 3 feet in diameter. The proportion of tuff ma- trix ranges from 5 to 75 percent; more generally it is about 25 percent. The pyroclastic deposits are uniformly well indurated and, when broken, commonly fracture across fragments and matrix alike. These deposits are unstratified and commonly form smooth rounded cliffs 50 feet high. The breccia weathers into boulders 20 feet in diameter that commonly are difficult to distinguish from bedrock ledges (pl. 11;). Boulders of the breccia as much as 50 feet long occur along the south coast of Udot. The blocks of lava in the breccias range from fine-grained nonpor- phyritic andesite and trachyte to andesite porphyries consisting large- ly of plagioclase phenocrysts. Many of these blocks are amygdaloidal, many are vesicular, and some are scoriaceous. Blocks of coarse-grained phaneritic gabbro are widely distributed. Individual crystals in the gabbro are most commonly one-eighth to one-fourth inch in diameter. Some blocks of gabbro are cut by fine-grained dikes of trondhjemite and a (C Breccia boulders, south Udot. The boulders have slumped 25 to 50 feet stratigraphically below the source bed. Many of these boulders are 10 to 20 feet in diameter and are suitable for cyclopean riprap rock. 195lt—55. Plate 1h some contain inclusions of metamorphosed volcanic rock. Blocks entirely of metamorphosed lava and pyroclastic rock have also been found. Sever- al fragments of limestone less than 2 inches in diameter were collected from the breccia on Udot and Eot. Lava flows: lava flows are widely distributed on Udot and Eot and one flow occurs on Eiol. Both fine-grained and porphyritic lavas are common. Thin-section study shows that andesite flows are most abundant, but basalt and trachyte are present. Some of the trachyte contains quartz, a mineral not found elsewhere in the Truk lavas. Alteration of olivine, augite, and, in some cases, plagioclase is common in the flows on Udot and Eot. Much of the lava is vesicular, and many flows are a- mygdaloidal. Autobreccia is abundant and widespread on Udot and Eot. In general, it consists largely of angular fragments of fine-grained lava. Vesicular to scoriaceous autobreccia is common at the tops and bottoms of the lava flows. In many flows compact lava is fractured and grades into autobreccia. Single lava flows do not form prominent scarps as on the eastern islands, and the thickness of a single flow was no- where determined accurately. Most flows are probably less than 20 feet thick. lava is irregularly intermixed with breccia in several exposures and does not form well-defined flows. These irregularly shaped bodies of breccia commonly contain included blocks of lava similar to those of the pyroclastic breccia, and grade into breccia having lava in the ma- trix. Dikes: Dikes are abundant on both Udot and Eot. Most are between 1 and 5 feet thick. They are generally andesite, ranging from nonpor- phyritic to very porphyritic, but some dikes consist of quartz-bearing trachyte. Minerals in the dike rock show alteration similar to that in the flows. Pyrite crystals in a number of dikes are commonly dissemi— nated in fine grains. In one trachyte dike, fracture surfaces are ve- neered with small pyrite crystals. Generally the dikes have a uniform thickness and attitude although some are irregular in shape and have a variable attitude. Small dikelets, about an inch thick, commonly branch from some of the irregularly shaped dikes and penetrate the country rock for several feet. Multiple dikes, side by side, are exposed in several places. Where dikes of different attitudes intersect, the irregular sinuous dikes are cut by the dikes of uniform trend and thickness. The attitude of dikes, both the irregular and uniform types, is varied; dips range from 10° to vertical and strikes are in many directions. Mbst of the dikes, however, fall into a radial pattern having a projected center north of Udot and west of Eot. Udot: Udot consists of three major upland segments connected by low narrow divides and fringed by wide fresh-water marshes, mangrove swamps, and calcareous beach deposits (map 3). Udot is 2 3/h miles long east-west and is about half a mile wide in the central and eastern por- tions and l l/h miles wide in the western segment. The elevations of the upland segments, from east to west, are hho, 470, and 790 feet (13%, lha, and 2h2 meters). Several small peaks rise from the lower slopes of the upland area. The large conical mass of Uitonap mountain is largely andesite lava flows and autobreccias. Andesite flows interfinger south- ward with breccia on the north side of the central segment. Elsewhere, breccia and related pyroclastic deposits predominate over lava flows and autobreccias. The dips of several poorly exposed lava flows vary as much as 30 degrees in exposures several tens of feet wide. Much more reliable is the attitude of the gabbro-rich breccia bed on the central segment of Udot; this bed strikes east and dips 5° to 10° S. Bedding appears about horizontal in a small exposure of stratified lapilli tuff 67 at an elevation of about 400 feet (122 meters) on the west side of the eastern segment of Udot. Dikes are common on all parts of Udot. Attitudes of the dikes 4" differ considerably, but many dikes have a radial orientation with the center lying approximately 1 mile north of east central Udot. Eot: Eot, a small island a quarter of a mile north of Udot (map 3), 1375mm 1,000 yards north-south and 500 yards east-west. An up- land area of volcanic rock rises to an elevation of 190 feet (58 meters) in the central and approximately 135 feet (ho plus meters) in the south parts of the island. A fresh-water swamp borders the southwestern part of the upland. Calcareous sand fringes this swamp on the west and also borders much of the eastern side of the upland area. Calcareous debris is cemented to form a hard compact matrix for pebbles, cobbles, and boulders of volcanic rock at about sea level at the north end of the island. One small patch of mangrove swamp lies on the eastern side of the island. The upland area consists of pyroclastic breccia except for an outcrop of lava on the west central point. The pyroclastic breccia contains a few fragments of light-gray and reddish limestone. Many (r‘\ dikes cut the breccia and lava; their strike ranges from west to north- west, conforming with the radial dike pattern exhibited by the dikes on Udot (map 3). E101: Eiol, approximately 1 mile east-southeast of Udot, is about #00 yards long in a north-south direction and 200 yards from east to west. This island is a small hill of volcanic rock about 100 feet high bordered by calcareous beach sand below 5 feet elevation. The hill consists of breccia overlain by 15 to 20 feet of fine-grained andesite very likely representing a single flow. The breccia, exposed in sever- al caves, is moderately well indurated where unweathered and consists largely of angular fragments of lava from less than an inch to 15 inch- es in diameter in a tuff matrix which generally forms 20 to 50 percent of the breccia. Some rounded boulders several feet in diameter were found in the breccia at one place. Western islands: The western islands consist of the large sprawling island of T01, with Fala-beguets to the east, and Ulalu to the north- east. T91: T01 island is formed by four upland blocks of volcanic rock separated by long embayments. Narrow channels joining the embayments (l are crossed by wooden bridges and by rock causeways. Mangrove swamps are more extensively developed around T01 than around any other of the lagoonal islands. They have a width of three-quarters of a mile be- tween Pata and the northeast uplands, averaging in general one-quarter of a mile, and are entirely absent only in a few places. Muck.and peat occurs in isolated patches between the mangrove swamps and the base of the upland. Beach deposits of calcareous sands form a few narrow strips, chiefly along the north and south shores of the island (maps 1 and 2 . The highest elevation in the Truk Islands is reached on south-east Tol where the peak of Mbunt TUmuital is 1,h53 feet (hh3 meters) above sea level. The geology of the T01 uplands differs from that of both the east- ern and central islands. Nearly all of Tel consists of basalt and an- ti desite flows out by vertical fractures and dikes having a northeast 68 69 (2X vertical exaggeration) elevation 450— : ,. olivine basalt —I4OO a) ‘ 0 — 9— 40° —|3OO ll||||||I oIivine basalt _ IIIIIIIII olivine basalt ‘—i200 . . 350— ollvme basalt eiioo ‘ . olivinfebbasqlt “—Iooo au 9 reccm 300— andesite. _ .outobreccw j—eoo olivme basalt 250i 800 Zeroo zoo- -~600 'wj”5°° |||||||l|l olivine basalt 2—400 _ _ lllllllll olivune basalt (poorly exposed) loo— 50— : 590 l 0100 l5l00 20'00 2 5‘00 30100 35loo 40100 feet [I1IIIIIIIIIIIIIITIIITT‘TTTYI FrlrrllIIIITIIIIIIIIYrIIIIIIIl' ICC 200 500 400 500 650 700 800 900 IOOO I ma I {:00 mete rs H distance H' Figure l4. GEOLOGIC SECTION, MOUNT TUMUlTAL, TOL Blank areas are undivided volcanic rocks. Summit elevation 443 meters or |,453 feet. See inap 2 forlocafion. trend. This series of flows is unconformably overlain on northeast T01 by one flow of melilite-nepheline basalt and one of nepheline basalt. Most of the basalt and andesite flows are between 20 and 60 feet thick, but flows as thin as 2 feet occur. The tops and bottoms of flows are commonly characterized by slightly vesicular to scoriaceous auto- breccia. At one place two dikes, 3 inches and 12 inches thick, cut overlying autobreccia several feet thick. These intrusions are similar to the underlying lava flow and probably represent lava squeezed upward from the flow before the lava had solidified. A high proportion of the flows is vesicular or amygdaloidal throughout, and many flows consist largely of vesicular or amygdaloidal autobreccia. Plagioclase, olivine, and augite are commonly present in recognizable phenocrysts. Basalts and andesites are generally very similar in appearance, and on Tel the distinction between the two is particularly difficult without microscop- ic examination. Except for the plateaulike summits on northeast Tbl, exposures are so poor that no basalt or andesite flows could be mapped singly. Pyroclastic beds are rare, having been found only just east of Neaut channel and on Pata. Dikes have been found on all of the volcanic uplands, and are un- doubtedly more abundant than are shown on the geologic maps of Tol (maps 1 and 2). Dikes, however, appear to be most abundant on the southeast half of northeast Tol. Andesite dikes predominate but basalt dikes are common and several soda trachyte dikes have been found. The dikes range from 15 inches to 8 feet in width. Several dikes commonly crop out side by side and have a total thickness of as much as 10 feet. The dikes are vertical and uniformly strike northeasterly; the most prevalent direc- tion is N. 60° E. Joints, or fractures, in the lavas parallel to the dikes can be seen at many places. Such fracturing, possibly accompanied by faulting, are probably responsible for the prominent northeast—south- west orientation of valleys and scarps on northwest and southwest Tol. Although the present topography is suggestive of faulting no conclusive evidence was found. TWO lava flows forming the relatively flat upland surfaces on northeast Tol overlie unconformably the dikes and fractured lavas. These flows form palisades around the east and southwest sides of this upland area. The southern capping flow extends 1 l/h miles northwest- southeast and averages one-quarter of a mile wide. The flow surface slopes from about #30 feet elevation at the north to 200 feet at the south. The flow ranges in thickness from 150 feet at the south to 50 feet at the north. The down-dip thickening of the flow suggests the filling of a valley to the south. The rock is melilite-nepheline basalt. The summit flow to the north (pl. 15 A), topographically higher than the southern flow (pl. 15 B) and separated from it by a 300—foot- wide saddle, is underlain by the undivided lava flows of basalt and an- desite which extend under both of the capping flows. The northern flow averages 100 feet in thickness and the outcrop is 1,500 feet long with an average width of 500 feet. At one exposure the summit flow unconform- ably overlies a steeply dipping surface eroded on a fractured dike~in~ truded lava. This old erosion surface strikes N. 20° E. and dips h5° to 50° W.; very likely it is part of one side of a former valley. The present eroded surface of the summit flow is essentially horizontal; no contrary indications of dip were observed in any part of the outcrop. The flow is nepheline basalt. 70 A. Nepheline basalt mesa (Mbunt Unimor), Tol. The mesa is a remnant of a single flow of nepheline basalt and is encircled by a cliff generally lOO to 150 feet high. 1954-55- B. Melilite-nepheline basalt plateau, Tol. Looking west to thick flow on northeast Tol. A scarp generally 100 to 150 feet high fringes this plateau about a mile northwest and southeast (right and. left). 1951+-55. Plate 15 unusual pegmatitic zones characterize the upper part of the 100- foot-thick outcrop of nepheline basalt flow. A 2-foot-thick zone show- ing pegmatitic segregations is exposed 30 feet below the eroded upper surface of the flow, and in the upper 5 feet of this exposure the peg- matitic segregations are extremely abundant. 0n the eroded surface of the upland, pegmatitic areas range from a few inches to tens of feet in length and are of various widths. They form more than 50 percent of the eroded surface outcrop of the flow. Some crystal grains are one- half inch long but in general they average from one-eighth to one-quar- ter of an inch. Every gradation is shown from the coarse pegmatitic texture to the even-grained fine texture characterizing most of the flow. The surface of this lava flow has weathered into fluted pinna- cles several inches to several feet high (pl. 16 A). The stratigraphic relations of the nepheline basalt and melilite- nepheline basalt flows are not definite. Both flows rest upon the dike- intruded surfaces of the undivided basalt and andesite flows. There is nothing to suggest that the topographically higher nepheline basalt overlapped the melilite-nepheline flow to the south. They may have issued from different vents, analogous to the late valley-filling nephe- line basalt flows on Oahu (Hawaii). These flows were erupted from vents on the flanks of the Kbolau Range which is itself a product of fissure eruptions (Wentworth and Winchell, 191W, p. 75-77). Most of the volcanic rocks on Tol appear to dip westerly but only in a few outcrops are definite measurements possible because of the deep weathering and heavy vegetation cover. On Pata pyroclastic beds have an apparent strike of north and apparent dip of 15° W. Autobreccia beds in the eastern part of this northwest block strike N. 25° E., and dip 10° W. The uppermost lava flows on Mount TUmuital, observed from the southeast, show apparent dips of 5°-7° SW. An exception to the westerly dips is the melilite-nepheline basalt flow described above. It has a dip of 2° SE, apparently due to valley filling. Fala-beguets: The elongated dome-shaped island of Fala-beguets lies 1.5 miles east of Tol. It is 1.2 miles north-south and averages slightly less than half this in width (map h). Mangrove swamps border the west shore. Beach deposits of calcareous sand extend westward for half a mile from the north tip and also occur as two narrow bands on the mangrove-free east shore of the island. The volcanic rocks forming the upland are mostly basalt flows. Pyroclastic breccias, if present, are not exposed. The slopes are cov- ered with lava blocks; outcrops are few and so limited in extent that at no place are separate flows mappable. Ulalu: The small island of Ulalu is 3.3 miles northeast of Tbl. It is oval in shape with the east-west axis 1+,ooo feet long and about 2,000 feet north-south. A small peak (Wichuk) at the east end has an elevation of 58 meters (190 feet), but most of the island is less than 100 feet above sea level. Fresh-water swamp deposits border the up- lands on the south side of the island. Calcareous beach sands surround all but the northeast and east shores. The volcanic rock on Ulalu is nepheline basalt, apparently a single flow. Because this rock is similar in composition to the nepheline ba- salt flow on Tol, Ulalu is classed with the western group of islands. Reef islands: The Truk Islands include about 65 islands composed of calcareous material. Approximately ho of these islands are on the bar~ rier reef, and about 25 lie on lagoonal reefs (fig. 1). Reefs of the Truk Islands were not systematically studied, but field examination was made of 15 islets on the barrier reef and one reef island in the lagoon. Some other islands are mapped from aerial photographs. Reef islands are widely distributed in the lagoon and on the barri- er reef but are largest and most numerous on the northeast and southeast parts of the barrier reef. The largest coral island, Mesegon, is about l 3/# miles long and has a surface area of about 0.26 square miles. (Surface areas of some other reef islands are given in the Topography chapter.) The largest barrier-reef islands are elongated parallel to the reef. Where the barrier reef is widest, islands lie on the lagoonal part of the reef; elsewhere most islands lie on the central part of the barrier reef. Falas island, in the northern part of the lagoon, lies on an elongate reef, but other lagoonal reef islands lie on relatively small coral knolls which are steep faced'to the floor of the lagoon at depths of from 20 to ho fathoms. The reef islands consist largely of unconsolidated material. Calcareous debris is most abundant, but fresh- water marsh deposits and salt-water mangrove-swamp deposits are wide- spread on a number of the larger islands on the barrier reef. Consoli- dated calcareous beds are common at and near sea level. Distribution of materials is shown on map 8. Sand occurs both on beaches and in the interiors of islands. Sand beaches encircle nearly all of the lagoonal islands. On the barrier- reef islands, sand beaches are common on the lagoonal sides but occur to a lesser extent on the seaward faces (pls. 16 B and 17 A). Sand is pre- sent on cobble beaches of many barrier-reef islands. The beach sand con— sists almost entirely of Foraminifera, coral detritus, and shell frag- ments in varying proportions. Sorting of the beach sand is generally rather good. Sand beaches are generally from 10 to 30 feet wide at low tide; at high tide most sand beaches are less than 10 feet wide, and many sections of beach are under water. Foreshore gradients are gener- ally between 1:6 and 1:10; where present, the backshore is generally flatter. Sand spits occur on a number of islands (pl. 17 B). Calcareous sand predominates over other materials in the interiors of most islands. 0n the smaller islands and islands with very little vegetation, the sand is similar to that of the beaches. On the larger islands the sand is intermixed with silt-size organic matter, and com- monly also with coral rubble. Material of pebble size (h-6h millimeters) occurs chiefly on beach- es of barrier-reef islands, where it is most commonly rounded and inter- mixed with coarser debris. Only rarely do pebbles predominate over cobbles on beaches. Angular material of this size - chiefly fragments of coral - is widespread in the interiors of barrier-reef islands, but only at a few places does it predominate over sand. Detritus of cobble size (6h-256 millimeters) is largely restricted to barrier-reef islands, where it forms much of the beach area (pl. 18) and is a major constituent of the interior. most of this detritus is subangular, but local stretches of beach consist of moderately well- rounded cobbles; angular blocks of coral are very common both on beaches and island interiors. Coarse cobble beaches predominate over sand beaches on the seaward faces of the barrier-reef islands. The average size of cobbles is generally somewhat less on most lagoon-facing beaches 72 Plate 16 / / A. Weathered pinnacles on nepheILine basalt, Tol. Fluted pinnacles locally forming the surface of a flow of neph- eline basalt on northeast Tol. This is an example of rockland in engineering materials Unit 1. Similar pinna- cles have not been found elsewhere on the Truk Islands. 1954-55- a B. Ocean-facing beach, Edat. Looking east along a the south coast of Edat on the southwestern part of the barrier reef. The beach consists largely of coarse sand. About high tide. February 1955. «a A. Ocean-facing beach, Uijec. Looking southwest along Uijec on the southeast side of the barrier reef. Beach consists of medium- and coarse-grained sand. About low tide. February 1955. B. Sand spit, lamoil. Looking north on the north side of lamoil on the north side of the barrier reef. About mean tide. February 1955. Plate 17 Plate 18 A. Seaward beach, Fanan. Looking northeast along the seaward (southeast) side of Fanan on the south- east side of the barrier reef. Beach consists largely of coral cobbles and boulders. Near low tide. February 1955. B. Closeup of coral cobbles and boulders, Fanan. Closeup of beach in photo above. February 1955. 4 Plate 19 A. Surface of fringing reef, Uijec. Looking southwest along the ocean—facing side of Uijec on the southeast part of the barrier reef. Coral blocks as much as 6 feet in diameter litter the reef limestone forming the land- ward part of the reef. About low tide. February 1955. B. Niggerheads between Tora and Ruac. Looking west at several niggerheads or projections of reef limestone on the northeast part of the barrier reef. The limestone projection at the left, con- spicuously undercut, is a good example of a mush- room rock. Elevation of the mushroom rock is about 6 feet at low tide. About low tide. Feb- ruary 1955. than on the seaward—facing beaches. On many islands the seaward-facing cobble beach merges inland with a rubble ridge having an elevation of from 5 to 10 feet at low tide. Mbst ocean-facing beaches are from 10 to 30 feet wide at low water; at high tide most are from 10 to 20 feet wide. lagoon-facing cobble beaches are generally somewhat narrower. Cobble beaches generally have foreshore gradients l/ of 1:3 to 1:5 and equally steep faced berms on the backshore. Coral boulders (rounded blocks more than 256 millimeters in di- ameter) and blocks of equivalent size are widespread on the barrier-reef islands. They are scattered along most cobble beaches and offshore on the surface of the reef (pl. 19 A). Marshes and mangrove swamps are restricted to the larger islands on the barrier reef. The fresh-water marsh deposits of interior depres- sions consist of a layer of muck and peat 0.5 to 2 feet thick. The mangrove-swamp deposits are chiefly sand where fringing the shoreline. Several interior areas of brackish or salt-water mangrove swamp contain chiefly a 0.05- to l.O-foot-thick layer of muck and peat. Consolidated deposits, namely limestone, include those that have grown in place as well as those made up of fragmentary calcareous detri- tus. Reef deposits that have grown in place are chiefly exposed above sea level as mushroom rocks and larger eroded areas of reef limestone exposed chiefly at low tide. Mushroom rocks are common on the barrier reef (pl. 19 B) and on reefs fringing the volcanic islands; eroded areas of reef are found chiefly on the barrier reef adjacent to reef islands (pl. 19 A). Maximum elevations of the mushroom rocks are about 6 feet at low tide; most eroded areas of reef are exposed onky at low tide. Consolidated reef rock, probably grown in place, is exposed in a small area of the interior of Pis island. Consolidated detrital calcareous deposits are exposed both in the lagoon and on the barrier reef as beds fringing the islands. Some beds form ledges from a few inches to 1 1/2 feet high; others form a beach pavement which is commonly veneered with unconsolidated detritus. The deposits range from cemented calcareous sand to cemented coral rubble. Both the finer grained and coarser ma- terial form individual beds, but the two are interbedded in some expo- sures. The cemented coarse detritus forming some seaward-dipping beds (pl. 20 B) is lithologicalxy similar to some deposits exposed on the upper surface on the reef. Elevations of consolidated detrital beds rarely if ever exceed h feet at low tide, and most beds are submerged at high tide. These beds generally strike parallel to the shoreline and dip 5 to 10 degrees seaward (pl. 20). However, the strike of con- solidated beds departs approximately 30 degrees from the elongation of Onamue island, in the western part of the lagoon (map 8). Some beds extend along the strike beyond the limit of several barrier-reef is- lands. Lagoon deposits: Information about the deposits on the floor of the lagoon is largely taken from hydrographic charts (U.S. Navy Department, Hydrographic Office, l9hhc, l9hhd, and l9hhe). From sea level to the greatest depths in the lagoon, #3 fathoms (258 feet), coral is shown to predominate over all other material. Whether the coral is living or dead is not known. nearly all of the remaining bottom material is in- dicated as sand. Both fine and coarse sands are present, according to the hydrographic charts, and the presence of shell material is indi- cated in several soundings. 17 In this chapter, gradient is expressed as the ratio of vertical to horizontal. 73 I I I I I I I I I I 25 30' 35' I5 Pad 45' 50' 55' I 52°00' 05' North Pass P ‘ ) Ushi ass (Ushishima Pass EXPLANATION 6:3 Ebarm Pass - Onao e _ 40- 7. . _ P's T H Ushi 40'- \< True ““9 0“ 5"”‘9 Alanenkobwe onet LOP T335 Tara Pass (Tarashima Pass) 77 . . LomOII Tdro \ \ Apparent dip and strike AgFalalu Ruac \ Dikes _ % Holop Direction of lava flow determined ' I from alignment of valley walls % AOL Inferred centers of eruption. NOFIhGOS' ISIODdS / |\ o ._ ' s2 '_ 35 \\\ Probable shape and limit of former volcano €53 °Fanuela - 35 9 fl ————————— °Buet Liball 6? P ///// Falos “Fanuet \\\\ é //// §3 aFanamar \ \\ Quoi _ EXaWata-shima \\ 3%?” Island _____ \ , / ,_ ,_ -— -' "' "' ‘ ‘ \ g \ V “”30, /f ,z”" \\\ Sand Island \\ Northeast Pass 7°30,— / / / /’ . \ Falo ° \ // / / Ago Schetbgn Island 5‘ \ / ' \ TauaI/ap/ Pass 6? / / ——————————————— #9 \QOsakura \ / a/ x’” “ 3% M, .- \ \ a I / _ — / A“; Reef /,/ ’ . 3‘ {‘36 “it, \ Small tstant}\ / I /// A! 6%k‘f?’ , \\ . \ ' / /. . ' . \ Faleallej Pass / / MOEN :7 2-'-\ \ / / V 2 to h l I d\ / / - I?" 7 \ \ ”S s on \ - Eli Kanibu _ . Lelom Reef / / aKU“ ., GWhite Sand Islet § {6 ’ .\ . t \ , 25 Lelom P / F | ' Y°"09'\ 4‘ ‘Hertf 25—1 t / / "“55- Qwow \t/ “‘5 l l / / '3 ‘ , , —o- —o— \l/ Fanufan Reef I, I .. ' . / |\ /|\ 7I\- D/UgJ-ON ”SLAND I : I ‘ ' ._ UDOT Eot I IPata Peninsula I ‘2 TOL . Param FEFAN 6" I I I I‘ I‘ g g "'2. 5 50' Q, \ I—é Fanamu / II 5:96 Piaanu Pass onamue' \\ \\ if A- Q Q @FALA-BEGUETS "1; age" // // ‘ Boquet \ ' / " , / ‘ _ 20' Polle Peninsal‘afif ‘ Tarik \- 'L// " / Onena / 20-- \ V” a " .. / / I. . . . .. Al I Torres Island E\dat \\ \ - //’L/=§' k UMAIj// Mews:Wt}/Ptsmmelikgir‘gcgar ngnjeJJ'mo Fanueranu \ ”“93 \\ ganurmot ///%T / . ' I \ //’ sis - / Alansetru Islands \\ \\ \ ° ,// ’ //fako Atkin // \ I} \__E _____ /// . Q QOnnaram \\ Neneperer Reef a / //’/ thu// Fananan \\ eetlt’ueil‘ap Reef , ,/ ’ ’ 10"“ Reef // _ '5. \ ‘o... \ \ \ ‘ ‘ _'G _______ -- " Pogura Reef / / oOzen . ‘f I5'— \\\ ‘izg‘Tamaryr Reef Paguerion Re/ef/// smut ' Felm . Lamas Reef 1‘, . Faleu ,,/// 3E0 . SalatPass figure I 5 OIGW l—“cxszs— lit—yu—REeL’P‘a , [ll/eon Pass Fem P05; ”0"“ ' F ‘1— — — — .— 1“ 6.659 .' Lepis Reef Uput . PROBABLE CENTERS OF ERUPTION °'°S' wttguro Pass P i rourup ' «a a ~euuPass anusamoz ass s ' Panes TRUK ISLANDS , _ gPizion Pass Aualap Pass P’SP’S P055 Fanan Minami-suidé xgleasioz Reef . o 5 l0 Statute miles 2;; Udidang Ultgar Pass ._ ' 1 I t‘.".' ,v'vlg' ' ' _ IO IIIIIIII II I II I I I II I I' I I I I I ‘ I a ./r .IJdldan P055 IO 0 5 l0 l5 Kilometers , Otta Pass Otta ‘ UI 18C Nenna Pass' :1":- V ‘. 25' 30' 35' l5l°40' 45' so' unnug‘” Pass 55' |52°OO' 05' I - l l 1 l l g l l 6 Plate 20 A. Beach rock, Ollan. Looking north- west along the southwest corner of Ollan on the southern part of the barrier reef. Seaward-dipping beds of cemented calcar- eous debris (beach rock) in center. About low tide. February 1955. B. Beach rock, Uijec. Looking southwest along the ocean-facing side of Uijec on the southeast side of the barrier reef. A seaward-dipping ledge of cemented coral debris is at left. About mean tide. February 1955. Plate 21 A. Weathered lava, Mben. Roadcut exposure of deeply'weathered olivine basalt flow on the east side of Tanaachau mountain. Residual unweathered blocks are visible in the upper part of the photo. April 1955. B. Exfoliation weathering of boulder on north- east Eten. l95h-55. flows may have been erupted from a central crater rather than a linear fissure system. (3) The abundance of coarse unstratified pyroclastic breccia and of thin brecciated lava flows on Udot suggests a source nearby. The andesite and quartz-bearing trachyte flows are mineralogically similar to dikes on Udot and Eot, and many of the flows and autobreccias, and some of the pyroclastic material, may have been erupted from these old fissures. An additional source is indicated by the occurrence of gab- bro blocks and blocks of metamorphosed volcanic rock unlike any dike rock. The dikes on Udot and Eot have a radial pattern outward from a point about a mile north of east central Udot and half a mile west of Eot. By analogy with the dikes radiating from a central crater in some other volcanoes, as Borabora (Stark and Howland, l9#l), a central cra— ter north of Udot and west of Eot seems very likely. The southward dip of the gabbro-rich breccia bed on Udot also suggests a source to the north. This central crater may have erupted many of the lava flows and autobreccias as well as much, if not all, of the materials in the pyro- clastic breccias. (h) The innumerable dikes on Tol are petrographically similar to the basalt and andesite flows on Tol.and Fala-beguets and very likely fill the fissures from which most, if not all, of these lavas flowed. A very analogous dike complex is believed to mark the source for the thick sequence of lava flows forming much of Oahu (Stearns and Vaksvik, 1935)- Other smaller eruptive centers were undoubtedly widespread, but data is inadequate to suggest more than two of such minor centers: the vents which erupted the nepheline basalt of T01 and Ulalu and the melie lite-nepheline basalt of T01 and the vents which erupted the pyroclas- tic deposits and thin lava flows of Eten. The former vents were proba- bly located north or northeast of Tbl, possibly between Tbl and Ulalu. The latter vents very likely lay west or southwest of Eten, between Fefan and Eten. Weathering Rock ledges, palisades, and stripped surfaces on gently dipping lava flows are exposed in many places on the volcanic islands and fresh unaltered rock specimens are readixy obtained. In general however, the rocks are intensely weathered, from a few inches to an observed 30 feet in the lava flows and to as much as 50 feet in the pyroclastic breccia and conglomerate. Only about 5 percent of the volcanic terrain is ex- posed bedrock; the remainder is covered with vegetation on soils weath- ered from the underlying flows. In the deeply weathered flows, residual centers of joint blocks composed of hard unaltered basalt and andesite are in a matrix of limo- nite-stained clay formed from weathering of the igneous rock (pl. 21 A). Boulders and blocks of lava in the pyroclastic breccia and conglomerate show exfoliation and alteration to limonitic clay. large boulders com- monly show nests of small Joint blocks rounded by exfoliation and sur- rounded by the less altered walls of the inclosing boulder (pl. 21 B). In most basalts and andesites the plagioclase, augite, and magnet- ite are fresh and unaltered. Olivine, however, is generally altered in varying degrees to serpentine, antigorite and other forms of chlorite, 77 and probably to saponite, one of the clay minerals. Similar alteration of interstitial glassy material to chlorite and saponite is common in some flows. Age The exact age of the Truk volcanic rocks is undetermined due to the lack of any certain criteria. No fossils have been found in the bedded tuffs or in the fine-grained matrix of the pyroclastic breccias and conglomerates although a special search was made for them at all exposures. Tayama reports that a pyroclastic breccia of Truk, which he calls an agglamerate, has, though very rarely, fragments of "limestone con- taining fossil Foraminifera, Cycloclypeus and Miogypsina (?)" (Tayama, 1952, p. 69 of original Japanese and p. 8% of Intelligence Division translation). These fossils, if present, would indicate Miocene age for the limestone fragments and Tayama has indicated this in the origi- nal version of his report (Tayama, l9h2). Although Tayama does not mention any special locality in the Truk Islands, he called the breccia from which the limestone fragments were reported ”Udot Beds”. The pyro- clastic breccia on Udot is of special interest not only for the possi- ble occurrence of limestone fragments, but also for the abundance of coarse-grained gabbro blocks with inclusions of metamorphic rocks which are unique among the Truk volcanic rocks. For this reason the well-ex- posed surfaces of the Udot pyroclastic beds were carefully examined and specimens collected of all types of fragmental constituents. Only three small limestone fragments less than 2 inches in diameter were found on Udot. On Eot, the small island to the east of Udot, four fragments of red limestone were collected from a pyroclastic breccia similar to the Udot breccia. These limestone fragments contain abundant Foraminifera, coral, algal, and echinoid fragments. The presence of Miogypsina indi- cates Miocene age for the limestone. The pyroclastic breccia is there- fore Miocene or post-Miocene in age. In the absence of conclusive fossil evidence, the age of the Truk volcanic rocks can only be estimated on the basis of erosion and by analogy with other volcanic areas. MacDonald assigned geologic ages to various rock units on Hawaii on "..... estimates of the length of time required to produce the observed amounts of weathering and erosion, either on the present surface or on older erosional surfaces preserved as unconformities between rock units; and on estimates of the length of time re- quired to build the observed volcanic structures." (MacDonald, 1953, P- 112) Nepheline basalt and melilite-nepheline basalt flows overlie un- conformably the older fractured lavas and dikes of Tbl, filling valleys probably 1,000 to 2,000 feet deep at the time of eruption. This se- quence of events closely resembles that of the Kbolau Range of Oahu (Hawaii), a volcano on which 2,000 feet of relief was developed prior to extrusion of the nepheline basalts (Winchell, l9h7). The valley- filling lavas on Oahu are scarcely eroded, whereas on Truk the valley walls have been eroded away; and the valley-filling flows, also exten- sively eroded, now form flat-topped ridges. Subsidence of 1,000 to 2,000 feet probably occurred submerging all but the topmost peaks of the former volcano. The oldest rocks of Oahu are Pliocene or older 78 (MacDonald, 1953). The subsidence and later dissection such as occurred on Truk are not seen on Oahu; hence Truk volcano is very likely older, possibly Miocene. Physiographic development During the height of volcanic activity the Truk Islands were very likely an elongate, domical shield volcano which became deeply dissect- ed by erosion when volcanic activity ceased. The volcano slowly sub- sided until only the rugged peaks of the former dissected volcano re- mained above sea level to form the present volcanic islands. Bays in- denting the coastline of Tol, Mben, and Dublon Island are very likely drowned valleys. During the earLy stages of subsidence, the volcano became fringed with a coral reef which continued to grow upward while the volcano sank, finally forming a barrier reef enclosing a large la- goon in which are scattered a number of islands of both coral and vol- canic rocks. The amount of subsidence can be estimated only within broad limits; the volcano has almost certainly sunk 1,000 feet and pos- sibly as much as 2,000 or 3,000 feet. Most of the lagoonal coral islands and reefs probably originated as reefs fringing volcanic terrain; submergence of the volcanic rocks resulted in coral reefs and reef islands. Distribution of the lagoonal reefs and islands suggests that the eastern half of the barrier reef has grown outward toward the east and northeast beyond the margin of the volcano while the western half remained static or even grew lagoon- ward. Marine terraces have been reported to occur wideky on Truk by Jap- anese observers (Tayama, l9hgyhl, p. 18 and 19 of English translation; Tayama, 1952, p. 39 and 1+0 _/_p. 15 of Intelligence Division translation]; (hmkai, l9h2, p. 7, 8, and 92 of English translation). The most wide- spread surfaces were reported to occur at elevations of 1-2 meters, 30- 50 meters, and 100 meters. Evidence is indeed widespread for a former erosional and depositional surface at a mean-tide elevation of 3 to 6 feet (1 to 2 meters): coral mushroom rocks, raised-beach deposits, and local abrasion of the volcanic bedrock. Reliable evidence is lacking for terraces at any other levels. Economic deposits There are no concentrations of economic minerals on Truk of suffi- cient size and grade to be of commercial value. Bridge (l9h8) described a small area of bauxite, about "200 acres on the summit of Mt. Witipon” at the east end of Mben. The "200" is evidently a misprint as the en- tire outcrOp of trachyte on Witipdn is only 63 acres. Present exposures of bauxite cover less than 20 acres. The bauxite consists of reddish- tan vesicular nodules, which are from 2 to 3 inches in diameter, and which superficially resemble dried sponges (pl. 2h). The nodules occur in a clay which is a weathered residue of the fine-grained trachyte flow capping Witipan (map 6). Chemical analysis showed the bauxite to be low in A1203 (h2.78 percent in the Bayer process) and Bridge con- cluded that it was of no commercial importance at that time. The small deposit is less well exposed now than when Bridge saw it and there is nothing in the present survey that modifies his conclusions. Concentrations of limonite (Fe203, anO) in the form of concre- 79 tionary nodules (pl. 25 B) from the weathering of olivine-rich basalt lavas occur on several of the volcanic islands. locations are shown as soil Unit 3 (map 13); areas of deposits in table 13. None of the de- posits are large enough to be of economic value. The concretionary nodules are described in detail in the Soils chapter. Soils by James E. Paseur General statement The soils of the Truk Islands consist primarily of clays and stony clays, saturated marsh and swamp soils, and sand. By far the most ex- tensive soils are the clays and stony clays which together mantle 63 percent of the land surface of the Truk Islands. Saturated, partialxy or periodicalxy flooded, organic soils of mangrove swamps and fresh- water marshes cover 21 percent of the surface, primarily around the pe- ripheries of the volcanic islands. Well-drained lime sand constitutes only 5 percent of the land surface of Truk but constitutes the princi- pal soil cover of the barrier-reef islands and low coral islands in the lagoon. The following minor soils account for the remaining 11 percent: bedrock outcrops and boulder talus (3 percent), artificial fill ( h percent), coral cobble and boulder fields (2 percent), and silt and clay containing limonite in the upper part (2 percent). The relationships of the soils of the Truk Islands are most clear- ly recognized if three primary environments, based on topography, are delineated: volcanic uplands, coastal lowlands and reef islands, and mangrove swamps. Mbst of the land surface (68 percent) of Truk consists of volcanic uplands on the larger islands within the lagoon. Within these areas are found the clays, stony clays, bedrock outcrops, boulder talus, and the silt and clay overlain by limonite concretions. The clays, named Truk clay, cover 23 percent of the volcanic uplands and are deeply weathered, granular, slightly plastic, well-drained, red to reddish- brown Latosols on gently undulating to steep slopes. The upper 10 feet are generally free of boulders. Truk stony clay differs in containing 15 to 50 percent boulders and generally occurring on steeper slopes. It is the most extensive single soil on Truk and covers 69 percent of the volcanic uplands. Fefan soils is the name given the silt and clay with limonite. These soils are characterized by a surface layer 1 to 3 feet thick having from 30 to 70 percent of gravel-sized limonitic con- cretions, the remainder being a dark grayish-brown to yellowish-brown, granular, friable, slightly plastic clay or clayey silt. These are the least extensive soils on Truk, covering only 2 percent of the volcanic uplands on high plateau areas. Bedrock exposures and boulder talus account for the remaining 6 percent of the upland areas. Coastal lowlands and reef islands constitute 17 percent of the Truk Islands. Within this environment are found freshawater muck and peat deposits, well-drained lime sand, coral cobble and boulder fields, and artificial fill. One third of the lowlands have saturated muck and peat deposits. On the volcanic islands these fresh—water deposits range from h to 15 feet in depth but on the reef islands they are only 1 to 2 feet deep. Another third of the lowlands, but constituting most of the reef islands, is Shioya loamy sand, 3 deep, light-gray to light- yellow or white, loose, lime sand occurring behind, slightly above, and including most of the present beaches. It forms most of the reef-is- land surfaces and, in some localities, occurs behind the mangrove swamps on the volcanic islands. Coral cobble and boulder fields, primarily on the reef islands, constitute 12 percent of the lowlands. Artificial fill, consisting primarily of volcanic rock and clay, constitutes the remaining 23 percent of the lowlands and is found principally on Dublon Island, Meen, Param, and Eten. 81 Mangrove swamps constitute the third distinctive environment and cover 15 percent of the Truk Islands. Although both sandy soils and muck and peat soils occur in the swamps, their areas are delineated as a single soil type because of the uniformity of all other factors. These swamp soils are submerged or tidally inundated and occur around portions of nearly all the volcanic islands and some of the barrier- reef islands. The vegetation consists of salt—water-tolerant trees most of which have branching aerial prop roots. Introduction During a 6-day visit to the Truk Islands in late June 1954, the soils were briefly studied on Mben, on southeast T61, and on Fefan and the distinctive soils to be mapped were decided upon and defined in a preliminary mapping legend under the supervision of Edward H. Templin, Senior Soils Correlator, Soil Conservation Service, U.S. Department of Agriculture. However, as the field work, which began in late October l95h, progressed some minor revisions had to be made in the preliminary legend so that it would more nearly conform to the overall conditions found on the various islands. The general approach was to identify and describe the soil units and to delineate them on aerial photographs of l:l6,000 scale. These field sheets were inked and the soil units transferred to the topograph- ic base map of l:20,000 scale. The soils were examined in numerous hand-auger borings, road cuts, borrow pits, trenches, and excavations. Soil-sampling trenches 2 feet wide, 8 feet long, and 5 feet deep were dug in the major soil units. The soil-sample sites are identified on the soils maps, maps 9 through 15; the soils mechanics test data for the samples are presented in table 20, chemical analyses in table 12, and profile descriptions of the sample sites are in the text discussion of the soil units. The areal extent and distribution, by islands, are given in table 13. The methods followed and the nomenclature used are in accordance with the Soil Survey manual (U.S. Department of Agriculture, 1951). The soil colors are described according to the Munsell color notations. The soil reaction was tested with the Truog pH field kit. Some of the term definitions are taken from Soils and Men, Yearbook of Agriculture (U.S. Department of Agriculture, 1938). The gradients were divided, according to the prevailing natural slope breaks, into three phases - level to 25 percent slope, between 25 and 65 percent slope, and over 65 percent slope. The undulating to hilly phase (level to 25 percent slopes) is normally divided into three phases; however, no attempt was made to further divide this broad phase because only 26 percent of the total volcanic uplands, including all the areas of Fefan soil, areas of Truk stony clay, and areas of Truk clay were mapped in this slope phase, and because the acreage of arable land was very small. The two phases 25 to 65 percent slope and the over 65 percent slope were established arbitrarily on their suitability to engineering construction and on the natural slope break. Some plants mentioned under the vegetation subheadings in each soil unit discussion are not fully described. Concise data concerning the growth habits, uses, and scientific, Trukese, and English names of the principal plants found in the Truk Islands are in table 16. The coral and boulder fields of the barrier-reef islands are dis- cussed in the Geology section. 82 _Table 12. (Analyses by M. Ikawa and T. Asari, Japan InSpection Co., Ltd., Tokyo, Japan, December 1955) Chemical analyses of soil samples, Truk Islands Table 12 Soil samples ME/lOOg % (depth from Cation H20 ground surface % % % % % % % % % % % % % N/C Excg. Ignition Content in inches) $102 A1203 Fe203 FeO MgO Cao Na20 K20 T102 P205 mno $03 002 Ratio Cap. Loss % (Dry Base) Fefan soils, sample 1, map 14 0 — 22 11.18 18.04 44.76 1.08 0.57 0.66 0.05 0.06 4.32 1.16 0.28 0.16 0.018 0.14 17.2 18.22 4.53 22 - 40 22.30 21.82 27.67 0.97 0.61 0.60 0.05 0.06 7.00 0.54 0.20 0.24 0.022 0.18 9.3 17.91 4.87 40 - 63 25.68 24.82 23.11 0.75 0.94 0.36 0.03 0.03 5.12 0.75 0.20 0.17 0.004 0.13 12.1 18.54 5.52 Truk clay, sample 2, map 13 0 — 4 ' 21.82 22.25 18.95 1.43 1.17 0.13 0.29 0.10 3.81 0.05 0.13 0.11 0.070 0.08 37.5 28.25 9.81 4 - 16 25.11 24.29 19.36 1.43 1.29 0.09 0.30 0.12 2.76 0.14 0.12 0.13 0.036 0.11 29.8 24.44 10.38 16 - 28 25.90 22.94 19.28, 1.43 1.56 0.17 0.26 0.13 3.00 0.04 0.27 0.12 0.029 0.10 36.1 22.73 10.61 28 - 54 25.05 22.56 26.06 1.07 1.42 1.43 0.36 0.16 3.40 0.12 0.27 0.12 0.018 0.09 29.3 20.27 10.09 54 - 66 27.14 22.06 19.38 1.22 1.70 0.17 0.21 0.12 3.81 0.06 0.26 0.11 0 0.13 38.8 22.35 11.22 Truk clay, sample 5, map 14 0 - 3 24.07 19.26 16.81 0.92 1.07 0.77 0.05 0.07 3.59 0.15 0.26 0.16 0.018 0.00 48.9 31.61 9.48 3 - 7 27.29 22.51 20.66 0.81 1.16 0.15 0.04 0.06 3.80 0.54 0.21 0.25 0.029 0.00 37.2 22.06 8.85 7 - 34 25.67 20.93 20.45 0.97 0.78 0.44 0.03 0.03 4.20 0.55 0.21 0.23 0.051 0.05 22.3 22.73 8.20 34 - 54 27.30 21.92 21.48 0.48 0.52 0.19 0.03 0.06 3.72 0.48 0.17 0.34 0.039 0.07 23.8 21.46 8.80 54 - 84 28.07 23.29 21.59 0.86 1.08 0.14 0.03 0.03 4.40 0.49 0.36 0.32 0.036 0.10 15.3 18.91 6.45 84 Plus 28.06 23.23 20.13 0.70 0.82 0.18 0.04 0.03 3.80 0.48 0.51 0.31 0.029 0.09 21.8 19.68 7.33 Shioya loamy sands, sample 6, map 14 0 - 6 0.35 0.10 0.56 0.34 0.028 51.52 0.36 0.13 Trace 0.48 Trace 0.32 35.50 0.08 4.1 14.96 1.54 6 e 15 0.50 0.005 Nil 0.14 0.028 52.66 0.59 0.084 Trace 0.29 Trace 0.27 36.65 0.104 7.9 13.17 1.70 15 - 30 0.25 0.04 Nil 0.14 0.028 53.68 0.64 0.15 Trace 0.26 Trace 0.29 39.20 0 1.1 14.27 0.77 Fefan soils, sample 7, map ll 0 - 7 0.78 16.47 51.63 1.22 0.23 0.39 0.28 0.064 5.36 3.88 0.14 0.13 0.051 0.08 7.3 18.20 5.20 7 - 15 0.61 18.68 51.06 1.22 0.17 0.26 0.20 0.088 4.96 3.89 0.14 0.20 0.043 0.00 6.5 18.77 5.47 15 - 24 0.99 19.80 44.39 1.05 0.17 0.23 0.28 0.046 6.72 3.84 0.13 0.23 0.070 0.00 7.4 20.93 6.11 24 - 32 1.08 20.48 46.24 0.93 0.15 0.25 0.24 0.084 5.93 2.63 0.10 0.19 0.039 0.04 5.9 20.49 5.53 Truk stony clay, sample 8, map 14 0 - 7 18.43 29.25 17.34 1.23 0.38 0.44 0.03 0.02 4.28 0.14 0.11 0.27 0.066 0.13 18.9 27.88 6.71 7 - 15 23.06 26.39 19.80 0.86 0.25 0.38 0.01 0.02 3.76 0.25 0.11 0.27 0.072 0.01 16.2 24.62 7.91 15 - 60 25.22 27.54 20.78 0.70 0.01 0.40 0.05 0.02 3.72 0.33 0.17 0.30 0.046 0.11 13.4 20.71 7.35 83 Table 13. Distribution of the soils units, Truk Islands (in acres). See also soils maps 9 through 15. Volcanic uplands Coastal lowlands and reef islands Total area Total Total area excluding Volcanic Islands Unit 1 Unit 2 Unit 3 Unit A Unit 5 Unit 6 Unit 7 Unit 8 mangrove upland area Truk clay Truk stony clay Fefan soils Rockland Muck and peat Shioya Fill Coral cobbles Mangrove SWEEPS loamy sands and boulder swamps 0 — 25% 25 - 65% 0 — 25% 25 - 65% over 65% fields 1/ slopes slopes slopes slopes slopes Eastern group Mben 95A 10 228 1,535 38h 26 235 #33 126 252 - #20 u,183 3,372 h,603 Falo 18 — h 22 - - 1 u 31 - - - 80 A5 80 Dublon Island 217 321 61 737 7h 2 60 #3 #0 A73 - 125 2,028 1,u72 2,153 Eten ' 2 - — 23 — - 1 - — 95 - - 121 26 121 Fefan 268 - 186 1,081 580 60 130 91 131 - - ##5 2,527 2,305 2,972 Param 77 — — 90 - - - 60 25 61 - - 313 167 313 Tarik 13 - 6o - - - - 13 38 — - - 1211 73 1211 Tsis 29 — 8 61 - 1h — 7 22 — - - 1&1 112 141 Uman 10 — 3h 55h 138 2h 19 69 6o - - 84 908 779 992 Central group Udot 232 11+ — 510 35 - 35 139 93 - - 66 1,058 826 1,121 Eot 23 - - M9 — - 2 ll 15 - - 3 100 7h 103 Eiol — - - u - — - — 9 - - - 13 h 13 Western group NE Tol 312 1&6 21 758 86 237 38 61 29 - - 7&9 1,688 1,598 2,h37 SE Tol 13h - 125 l,h27 186 - 157 11A 79 12 - 277 2,234 2,029 2,511 NW Tol (Pata) 6A 135 - 161 125 - 51 62 M3 — - #35 6A1 536 1,076 sw Tol (Polle) h02 - - 931 - - 60 129 91 - - 610 1,613 1,393 2,223 Fala-beguets 118 ho 33 66 - 11 1 - 38 - - 91 307 269 398 Ulalu 13 - 22 33 - 80 l 25 36 - - ‘ 210 lh9 210 Barrier—reef islands - - - - - - - - 320 - 450 10 770 - 780 fatal 2,886 666 782 8,0u2 1,608 h5h 791 1,261 1,226 893 A50 3,315 19,059 15,229 22,373 l/ Not mapped separately but included in Unit 7. 85 Classification and genesis location and climate place the Truk Islands well within the zone of tropical weathering. Some of the soils of Truk are lateritic soils, types which develop under tropical weathering. In this kind of weather- ing, the bases (such as calcium, potassium, sodium, and magnesium) in the parent material are dissolved in sufficient quantities to raise and maintain the reaction of the solution medium at about neutral. At pH values of from 6.5 to 7.5 the silica and bases are removed by leaching and the iron and aluminum oxides are retained by precipitation. The resultant soil from this type of weathering is high in iron and alumi- num oxides and low in silica and bases; it is also very low in cation exchange capacity. A total of h5h acres of Fefan soils, which are characterized by a surface layer of gravel-sized limonitic concretions (pl. 25 B), were mapped on the various islands. In these areas, the soil profiles are usually shallow and are underlain by either olivine basalt or nepheline basalt bedrock, most of which is porphyritic. One small area, mapped as Truk stony clay, on the summit plateau of Witip8n contained a 3- to 5-inch-thick horizon of bauxitic concretions situated 3 inches below the surface in a soil profile whose depth ranged from 2 to h feet (pl. 2h). The bedrock in this area is a trachyte which is relatively high in aluminum. The uplands of the Truk Islands are composed entirely of volcanic material. The upland terrain features are rough broken sharp ridges, steep to precipitous mountain slopes with a few undulating terracelike lava-flow benches, a few undulating to hilly summit plateaus, and some undulating to hilly footslopes. There are no mature stream valleys and no areas of alluvium large enough to be mapped separately. These facts support the theory that the islands are still subsiding. The low, mostly level, coastal terraces, which average about 2 feet above high-tide level, are made up of calcareous sands, fresh- water muck and peat marshes, and, within and slightly below the tidal zone, mangrove swamps. The three major soil divisions of the Truk Islands are those soils covering the upland volcanic areas, those found on the low coastal plains, and those composing the mangrove swamps (table 1h). Approxi- mately 70 percent of the total area of the islands is in the volcanic group, about 15 percent is in mangrove, and about 15 percent is in the low coastal-terrace division. Four soils were mapped on the volcanic area. They are rockland, Fefan soils, Truk stony clay, and Truk clay. Truk clay is the most deeply weathered soil on Truk. As observed in borrow pits, Truk clay is weathered to depths of as much as 50 feet. It contains a thick ho- rizon of highly weathered parent material from which the primary miner- als have been removed. The structure of the parent rock has been pre- served in variegated colors, the white specks showing former positions of plagioclase phenocrysts and zeolites (pl. 22 B). Truk stony clay is similar in color and appears to be similar to Truk clay in most physical characteristics except boulder content and depth. Its depth is estimated to be 1 to 30 feet and its boulder con- tent is 15 to 50 percent (pl. 23). This soil is the most extensive mapped on Truk. It is divided into three slope phases. The undulating 87 Volcanic uplands little or ngihorizontal development or parent material morification Escarpment faces and horizontal surfaces of nearly flat-bedded hard volcanic flows, steeply inclined unweathered breccias, and steep to precipitous colluvial rock debris exposed in 50 to 100% of surface I ROCKLAND l Well-defined horizontal development and parent material modification Brown, reddish-brown, red, and reddish-yellow clay, silty clay, gravelly clay, and stony clays Coastal lowlands Soils occupying the level low coastal terraces and reef islands Areas filledland stabilized with earth and rock material, paved with crushed volcanic rock and coral gravel or with either bitumen concrete or portlandrcement concrete l FILL Residual Llay and silty clay 10 to 50 ft. thick on gently sloping to rollingihillcrests, gently sloping to steep footslopes; surface 10 ft. free of brulders TRUK CLAY Residual stony clay and stony silty clay l to 30 ft. thick on undulating to hilly summit plateaus, saddles, footslopes, and on hilly to precipitous mountain sides and ravine walls; surface and profile contain 15 to 50% cobbles and boulders TRUK STONY CLAY I Residual gravelly clay and clayey gravel l to 8 ft. thick on gently sloping summit plateaus and terrace- like benches. The surface 1 to 3 ft. contains 30 to 70% gravel-sized limonitic con- cretions, the remainder clay; where present, clay layer separating the gravelly surface from bedrock is finn and slightLy plastic FEFAN SOILS Light-grey, light-yellow, and white, poorly graded, loamy, coarse and fine calcareous sands; the surface few inches stained dark with organic matter; coral fragments l to 2 in. diameter common SHIOYA LOAMY SANDS Freshawater mgrshes com- posed of very dark grey, very dark brown, and brown muck and peat, 3 to 15 ft. thick, mostly over lime sand MUCK AND FEAT Table 11+. Soils of the Truk Islands Marginal lowlands Soils mapped within and slightly below the intertidal zone. Shallow saltdwater or brackish swamps either permanently submerged or inundated tidalLy; soils either loamy lime sands or muck and peat underlain by lime sand WW 89 to hilly phase differs from the two steeper phases in being more shal- low, from 1 to 10 feet deep. Rockland. which includes areas of both bedrock and bouldery talus, is one of the smaller units mapped on Truk. With the exception of Fefan soils, which are generally underlain by olivine basalt bedrock, there is no apparent correlation between the soils and their parent materials. This is probably the result of the intense weathering which funnels the development of different basic parent materials toward a common end product. The low coastal terraces are made up of three soils - Shioya loamy sands, muck and peat marshes, and fill. The term fill is used arbi- trarily instead of made land and denotes areas in the coastal lowlands which have been filled and stabilized for construction. The mangrove swamps are not subdivided; even though the swamp soils are composed of areas of loamy sands and areas of muck and peat, they are mapped together. Soil units Unit 1. Truk clay: General features: Truk clay is composed of brown, reddish-brown, red, and reddish-yellow clay or silty clay which is friable and firm, slightly plastic and sticky, and slightly to strongly acid in reaction; depth to bedrock generally ranges from 10 to 50 feet. The surface 10 \feet is relatively free of boulders. Iruk clay is the second most extensive soil mapped on the Truk Is- lands. It is extensive on all the maJor volcanic islands, and is found on all the smaller volcanic islands except Tako, Atkin, Faneu, E101, and Yanagi. Ibpography and drainage: Truk clay is not restricted to any cer- tain topographic positions within its lepe range. It may occupy areas of rolling crests, divide saddles, hilly to steep mountain slopes, or gently sloping foothills. The slope surfaces are usually uniform or smooth and have very few deep erosional gullies. The soil is composed of residual clay developed on volcanic bed- rock, talus, or colluvial boulders. It is well drained; its surface runoff and internal percolation are moderate except in a few localized spots where perched water tables on shallow bedrock create marshy con- ditions. The depth to the water table is uncertain. No wells were seen, however a few seepy areas over rock outcrops were noted. The average depth to the water table is estimated to be about 25 feet with a range from the few surface seeps to 50 feet. Profile descriptions: Truk clay is mapped in two slope phases which are differentiated by the prevailing natural slope break. They are shown on the soils map as: Map Slope Total area smflbol Name percent facres) lD Truk clay, undulating to hilly o - 25 2,886 m Truk clay, 11111;; to steep 25 - 65 666 91 Approximately 80 percent of the Truk clay is in the undulating to hilly phase. More than 85 percent of this phase has slopes greater than 8 percent. The following is a profile description of Truk clay, undulat— ing to hilly phase (0 to 25 percent slope), one-fourth mile north of the Trust Territories administration buildings on Mben. The location of this profile is also sample site 2 (map 13); for chemical analysis of soil from this site see table 12 and for mechanical analysis see table 20. 0 to u inches, dark-brown (lOYR 4/3) clay; moderate medium (2-5 mm) granular structure; porous, well drained; friable, slightly sticky; pH 5.5; numerous roots; dark coloring probably due to organic matter content; grades to / u to 16 inches, reddish-brown (5YR u/u) clay with few fine faint brownish-yellow mottles (lOYR 6/6); moderate medium granular structure; friable, firm, slightly plastic; pH 5.0; numerous roots; grades gradually to 16 to 28 inches, reddish—brown (5YR 5/h) clay, numerous faint to distinct fine mottles of colors ranging from yellow and gray to red, dark brown and some black; moderate medium granular; riable, nonplastic; porous; pH 5.0; grades abruptly to 28 to 54 inches, very dark-gray to very dark grayish-brown (lOYR 3/1, 3/2) clay with numerous medium prominent mottles of white, black, and red; reticulate mottling divides the horizon into h—inch to 6-inch blocks by irregular yellowish-brown (lOYR 5/6) veins; nonplastic, hard-dry; appears to be clay weathered from a float boulder whose relict structural outline has been preserved; slightly porous; massive structure; pH 5.0; white mottles appear to be weathered plagioclase pheno- crysts; grades abruptly to 5h to 66 inches, reddish-brown (5YR 5/h) clay with numerous faint to prominent medium mottles of red, yellow, brown, and black; strong medium blocky structure; pH h.5 to 5.0; surface of peds coated with dark film; porous, numerous voids that are char- acteristic of highly weathered volcanic rock The following is a profile description of Truk clay, undulating to hilly phase (0 to 25 percent slope), one-half mile north of the airfield on southwest Mben (pl. 22 A). The location of this profile is the same as sample site 3 (map 1h); for results of soils mechanics test on soil from this site see table 20. 0 to h inches, very dark grayish-brown to very dark-gray (lOYR 3/l.5) clay; moderate medium (2-5 mm) granular structure; po- rous; friable, slightly plastic and sticky; pH 7.0; numerous roots. The higher than usual pH is related to the many small clam shells seen in this horizon; this dark organic layer to- gether with the clam shells strongly suggests the location of a former dwelling; grades to h to 7 inches, reddish-brown (5YR h/3) clay; moderate medium gran- ular; porous; firm, hard, slightly plastic and sticky; pH 6.5; contains many roots; transitional zone to the underlying ho- rizon 92 Plate 22 A. Soil profile in Truk clay, Moen. Entire 60-inch profile, in sampling trench, consists of clay, the chief differences being color. The upper part of the profile is reddish brown, the lower part is mottled in various shades of red, brown, yellow, and gray. February 1955. B. Closeup of eroded surface of Truk clay, Mben. Relict structure of weathered basalt flow visible. March 1955. 7 to 23 inches, reddish-brown (2.5YR h/h) clay; strong medium granular; firm, slightly plastic and sticky; porous; pH 5.5; contains some roots; grades to 23 to 60 inches, horizon is varicolored - hues 2.5YR to 2.5Y, values 1 to 7, and chromas l to 6, predominant color is red- dish brown (5YR 5/h); the reticulate mottling is indicative of highly weathered or completely altered volcanic parent material, possibly a breccia. The horizon is clay; weak me- dium granular to massive structure; porous; firm and sticky; pH h.5 to 5.0; few coconut roots The following is a profile description of Truk clay, hilly'to steep phase (25 to 65 percent slope), one-eighth mile north of the air- field on southwest Mben. location of this profile is also sample site 5 (map 1h); see table 12 and 20 for chemical and mechanical analyses of soil from this site. 0 to 3 inches, dark-brown (7.5YR 3/2) clay; moderate medium gran- ular structure; porous; friable; pH 6.0; roots numerous; dark color related to organicamatter content; grades to 3 to 7 inches, reddish-brown (5YR h/h) clay; moderate to strong medium granular; porous; firm, friable, slightly plastic and sticky; pH 5.5; roots abundant; few fine faint mottles of red (10R h/6) and few coarse prominent mottles of brownish yellow (lOYR 6/6); grades gradually to 7 to 3h inches, dark reddish-brown (523 3.5/3) clay; strong medium to coarse granular structure; porous; hard-dry; pH 5.0; many roots present; grades gradually to 3h to 5b inches, weak-red (10R h/h) clay, with numerous fine to medium mottles of reddish brown (5 IR h/h); moderate to strong medium granular structure; porous; friable, firm, slightly hard; pH h.5; some roots present; grades to 5k to 8h inches, reddish-brown (5YR h/h) clay with few fine faint yellowish mottles or flecks; moderate medium granular; porous; pH h.5; few root channels present; grades gradually to 8k plus inches, brown (7.5YR 5/h) clay (highly weathered rock) with numerous white, reddish-yellow, and black mottles (most- ly distinct medium and fine); massive structure; porous; firm, friable; pH h.5 to 5.0; reticulate mottles and streaks are common Range in characteristics: The surface structure of Truk clay ranges from strong medium (2-5 mm) to moderate coarse (5-10 mm) granu- lar; in the lower horizons, below a depth of about h feet, the struc- ture is commonly massive. (See glossary for definitions of soil struc- ture terms.) Both round limonitic concretions and flat, porous (presumably baux- itic) broken crusts or concretions were found on an old excavated sur- face about one-eighth of a mile north of the Trust Tarritories adminis- tration buildings on Meen. Since the amount or depth of soil removed from the area is unknown, the depth in the soil profile where the con- cretions formed is uncertain. Similar concretions were not observed in 93 borrow-pit walls at southwest Mben and on east Dublon Island and were seen in only a few of the many auger examinations made of this soil. Inclusions of other soils: The principal soil included in this unit is a dark grayish-brown, friable, firm to very firm, plastic clay exposed on a steep slope immediately east of the former radio station (now a Catholic school) on east Mben. Other inclusions are isolated irregularly shaped small patches of the Truk stony clay (Unit 2). Modification of the natural soil: Prior to World War II, a large part of this soil was forested with coconut and breadfruit trees. Dur- ing the war the Japanese cut most of the coconut and breadfruit trees and planted subsistence crops, principally sweet potatoes and some tap- ioca. Borrow pits were excavated on south Mben, west Dublon Island, and southeast Param. An intricate network of trenches, 2 feet wide and 2 to 6 deep, is common on knobs and ridges. A number of military instal- lations, such as search lights, antiaircraft guns, and barracks were located on this unit. Vegetation: About 70 percent of the Truk clay is either grassland or grassland interspersed with sparse coconut, mango, and breadfruit trees. A few isolated garden patches up to one-fourth of an acre are planted to tapioca, taro, yams, sugar cane, sweet potatoes, watermelons, and tobacco. The principal plants growing in the grassland vegetation are Miscanthus floridulus (swordgrass), Ischaemum muticum (fetinniap grass), Stachytarpheta indica, Cassia occidentalis, and Paspalum conju- gatum. Other plants found in this unit are listed in the vegetation section under the grassland vegetation unit and under the coconut- breadfruit forest unit. large areas are burned over annually because little effort is made to control fires which are set during the dry season to clean up the small garden areas. Because of the annual burnings, only partial re- forestation by native trees and shrubs is possible and the hardier grasses and weeds thrive. As a result, some areas support a pure stand of swordgrass, Miscanthus floridulus; other areas are covered with fetinniap grass, Ischaemum muticum. Utilization: Truk clay has developed under conditions favoring lateritic weathering; the resulting natural low fertility was further aggravated by its continuous use by the Japanese during the latter years of World war II in the production of subsistence crops (one crop of sweet potatoes every 3 months). However, as demonstrated by recent agricultural experiments on Mben, the soil will produce satisfactory crop yields with heavy applications of commercial fertilizers. The reaction of nearly all this soil is slightly to strongly acid. However, the low pH condition can be easily corrected by applications of the readily available lime sands of which the Shioya loamy sand is largely composed. As the population of the Truk Islands increases, a larger acreage of the undulating to hilly phase of this soil will have to be used in the production of subsistence crops. However, before satisfactory yields can be produced, the annual grassland fires will have to be stopped, and the land owners should be convinced of the merits of the agricultural practices entailing the use of commercial fertilizers and 91+ crop rotation with legumes, possibly Crotalaria intermedia. The por- tions of the hilly to steep phase which are in grassland vegetation should be reforested with plantings of coconut and breadfruit seedlings. The Truk clay will furnish an abundant source of binder materials that may be used for fill. Uhit 2. Truk stony clay: General features: Truk stony clay comprises about 57 percent of the total soils acreage, excluding mangrove swamps, mapped on the Truk Islands. It occupies parts of all the volcanic islands in the Truk La- goon except two tiny bare rock islets, Tako and Atkin. The soil is mapped in three slope phases: Map Slope Total area symbol Name percent (acres) 2D Truk stony clay, undulating to hilly O - 25 782 2E Truk stony clay, hilly to steep 25 - 65 8,0h2 2F Truk stony clay, steep to precipitous 65 -100 1,608 The 2D phase, a complex of two soils, ranges from 1 to 10 feet in thickness over volcanic bedrock. About 70 percent of this phase is a reddish-brown to a yellowish-red, friable, slightly plastic, porous granular clay with boulders and cobbles composing 15 to 50 percent of the soil profile. A few of the boulders and cobbles are scattered on the surface. The remaining 30 percent of the phase is a dark-brown to dark-gray, granular, firm, plastic, somewhat poorly drained clay. The 2E and 2F phases, which range in thickness from 1 to 30 feet over volcanic bedrock, are reddish-brown to yellowish-red, granular, friable, firm, slightly plastic, well-drained clays. Fifteen to 50 percent of the soil profiles are composed of volcanic cobbles and boul- ders. Some 5 percent of the two phases are made up of bouldery talus which is composed of 50 to 90 percent volcanic-rock blocks which range in diameter from h inches to 10 feet. The clay fraction of the boul- dery talus is granular, finm, and slightly plastic to plastic. Topography and drainage: Truk stony clay is mapped on terrain having slope ranges from gently undulating to precipitous. The undu- lating to hilly phase (2D) is found on the gently sloping summit pla- teaus, divide ridges, and footslopes. The hilly to precipitous phases (2E and 2F) are found on mountain sides, steep ravine walls, and sharp steep ridges down mountain sides. Although the rainfall is relatively high, especially during the wet season, surface runoff is seldom excessive, partly because the granular soils allow fairly rapid percolation of the water. Except in the minor plastic soil of the undulating to hilly phase, the unit is moderately well drained as evidenced by the relatively low runoff from its surface and the absence from its profile of the mottlings charac- teristic of poorly drained and aerated soils. The depth to the water table is unknown but when it is in the soil profile it is believed to be very near the contact of the soil and bed- rock. Seeps issuing from the top of bedrock outcrops are common. The position of the water table probably is extremely variable. In the 2D 95 phase, which is relatively shallow in comparison to the other two phases of the unit, the water table may be found as local seeps or may be completely absent above the bedrock. In the 2E and 2F phases the water table probably exists as perched water lenses on the flat bench- like steps of the nearly flat-lying volcanic flows. Profile descriptions: The following profile descriptions are re- presentative of the Truk stony clays. 2D, Truk stony clay, undulating to hilly phase, at Epinup village on Mben. O to 3 to 3 inches, very dark-gray (lOYR 3/1) clay; strong to moderate medium (2-5 mm) granular structure; porous; plastic and sticky, firm; pH 5.5 to 6.0; numerous roots; dark coloring probably due to organic matter content; some cobbles and boulders on surface; grades to 21+ inches, olive-brown (2.5Y h/h) to dark-brown (lOYR 4/3) clay; strong to moderate medium (10-20 mm) blocky to coarse (5-10 mm) granular structure; somewhat porous; very firm, strongly plastic and sticky; pH 5.0; contains some roots; cobbles and boulders from h to 10 inches in diameter common; grades gradually to 2% to 33 inches, very dark grayish-brown (2.5Y 3/2) clay, with few fine distinct mottles of dark reddish brown (5YR 3/fi); moder- ate medium subangular blocky to coarse granular; porous; plastic but nonsticky; pH 6.0 to 6.5; contains some ferrugi- nous concretions up to 10 mm in diameter; volcanic boulder or bedrock at 33 inches 2D, Truk stony clay, undulating to hilly phase (pl. 2h) on gently sloping plateau near summit of Witipdn on Moen. O to 3 to 7 to 3 inches, yellowish-brown (lOYR 5/h) clay; moderate medium granular structure; porous; friable; pH 6.0; roots numerous; grades abruptly to 7 inches, horizon contains about he to 60 percent irregularly shaped bauxitic concretions, measuring up to 2 inches in dia- meter, and ho to 60 percent clay. The clay, which is light yellowish brown (lOYR 6/h), is moderate medium granular; po- rous; friable, firm, slightly plastic; pH 5.5 to 6.0; roots common; grades abruptly to 20 inches, reddish-yellow (5YR 6/6) clay; moderate medium granular; somewhat porous; friable, slightly plastic; pH 5.5; grades gradually to 20 to 36 inches, brown (7.5YR 5/h) clay with few, fine to medium, faint to distinct mottles of grayish brown, yellowish brown, and dark grayish brown; weak medium granular; porous; friable; pH 5.0 to 5.5; grades abruptly to 36 to h8 plus inches, highly weathered trachyte bedrock 2E, Truk stony clay, hilly to steep phase, in roadcut one-fourth mile west of the church in Wichap village on Mben (pl. 23 A). Location 96 Plate 23 A. Roadcut exposure of Truk stony clay, Moen. Blocks of unweathered rock are present in a clay matrix. About 6 feet of soil profile are shown here. April 1955. B. Roadcut exposure of Truk stony clay, Moen. Boulders of rock 3 to 18 inches in diameter compose 30 to #0 percent of this 4-foot soil profile, most of the remainder being clay. April 1955. Plate 2h Soil profile, Witipo'n mountain, Moen. Complete profile of soil on tra- chyte lava flow near the summit of Witipon. Soil profile is about 3 feet thick. A layer, A to 5 inches thick, of bauxitic concretions is present several inches below the top of the soil profile (arrow). February 1955. C of this profile is also sample site 8 (map 1h); for chemical analysis of soil from this site see table 12 and for mechanical analysis see table 20. 0 to 7 inches, dark grayish-brown (lOYR h/2) clay; strong medium granular structure; porous; friable, slightly plastic; pH 6.0; numerous roots; grades gradually to 7 to 15 inches, yellowish-red (5YR 5/6) to strong-brown (7.5YR 5/6) clay; strong medium granular; porous; friable, fimn, slightly plastic; pH 5.5 to 6.0; highly weathered and un- weathered hard volcanic boulders up to 7 inches in diameter compose about 20 percent of horizon; roots form mat around both the weathered and the unweathered boulders; grades gradually to 15 to 60 inches, reddish-brown (5YR 5/h) clay; strong medium gran- ular; porous; friable, firm, slightly plastic; pH 5.0; yel- lowish to nearly black mottles and streaks common. Horizon contains 20 to 30 percent of volcanic float boulders (both highly weathered and unweathered) which range in size from 3 to 15 inches in diameter. This profile was not examined be- low 5 feet Aside from the steeper slope, nothing different was seen in the few exposures of 2F except that in general the percentage of boulders in the profile was considerably higher than in 2D and 2E. Range in characteristics: Truk stony clay, undulating to hilly phase (2D) generally does not contain many surficial boulders, but the phase includes a few small boulder fields as much as 2 acres in size. Also, there are numerous small areas where the profile is relatively free of boulders. Inclusions of other soils: Bouldery talus, estimated to range in thickness from 1 to 50 feet, is mapped under the rockland unit. How- ever, certain areas of it are included in the hilly to precipitous phase of Truk stony clay because they could not be separated accurately within the time allotted for this survey. The undulating to hilly phase also contains a few isolated areas of Truk clay and Fefan soils that were too small to be mapped separately. Modification of the natural soil: Both collapsed and well-pre- served trenches, caves, and tunnels and gun emplacements and search light sites are common in this unit on all of the larger islands and on many of the smaller islands; a few concrete buildings were constructed on this unit on both the northeast and southeast peninsulas of Dublon Island. Only a small part of the total area of the unit, however, has been modified by construction. A few acres of the undulating phase were cleared and planted in gardens during the last 2 or 3 years of the Japanese occupation. These areas have long since been abandoned and are now covered with grassland vegetation. The absence of severe erosion is due chiefly to two factors, the porous nature of the soil and the dense vegetative cover. Vegetation: The vegetative cover of the shallow undulating to 97 hilly phase is divided about equally between the two vegetation units grassland and coconut-breadfruit forest (see section on Vegetation and maps 16 through 22). The hilly to steep phase vegetation is predomi- nantly coconut-breadfruit forest with minor areas of grassland and some small areas of Ficus-Pandanus forest. The steep to precipitous phase is predominantly grassland and Ficus-Pandanus forest, but contains some coconut-breadfruit forest. Utilization: The small gentky sloping areas of relatively boulder- free, well-drained soils, 5 to 10 feet thick, found in the 2D phase are probably best suited for truck cropping. Although this phase is gener- ally somewhat less fertile than the 2E and 2F phases, it should produce fair to excellent crop yields under good management. The agricultural practices should include moderate to heavy applications of complete commercial fertilizers, sufficient applications of backshore lime beach sands to maintain a favorable pH, and a crop rotation system with leg- ume vegetative cover at least during the first part of the wet season. In l95h cacao was planted in an area of 2D on a footslope near Penisence village on Mben and the following year appeared to be making favorable growth. Because of their high gradients, and in places their inaccessibil- ity, the 2E and 2F phases are best suited to tree crops such as coconut, breadfruit, and mango. Even though these phases are recognized among the more fertile soils on the Truk Islands and although small patches as much as one-eighth of an acre are planted in upland taro, sweet po- tatoes, ymns, tobacco, and watermelons, it is believed that extensive clearing and clean—cultivation cropping would soon render them infer- tile through sheet erosion and leaching. Truk stony clay should furnish a good source of fill for construc- tion work. Unit 3. Fefan soils: General features: Fefan soils, which range in depth to bedrock from 1 to 8 feet, are characterized by a surface horizon which is com- posed of from 30 to 70 percent gravel-sized, mostly limonitic concre- tions, the remainder being clay or clayey silt (pl. 25 B). The thick- ness of the concretionary zone usually ranges from 1 to 3 feet. Where the depth of the soil is more than 3 feet, the gravelky surface horizon is generally separated from the bedrock by a stratum of granular, fria- ble, firm, slightly plastic to nonplastic, relatively concretion-free, yellowish clay which is divided (or discolored) into 2- to 5-inch ir- regularly shaped blocks by an intricate network of semi-indurated to soft, red ferruginous seams or veins from one-eighth to three-eighths of an inch in thickness. The Fefan soils is one of the smaller soil units mapped on Truk; its total area is fish acres. Topography and drainage: Fefan soils unit was mapped in the low- est slope range. The predominant slope range is from O to 8 percent with the larger areas having gradients of less than 5 percent. The soil is found chiefly on summit plateaus, as on Tbl and Ulalu, and on terracelike benches, as on Fefan and uman, but about 10 acres of it is found on the point southeast of Wichap village of Moen on the gently undulating low footslope. Drainage patterns are absent on all the areas except two located on the west side of south Fefan. Internal r"“ 98 5) A. Soil profile of Fefan soils, Sopuk peninsula, Moen. Upper 22 inches of profile consists of Mo percent loose limonitic concretions and 60 percent friable clay; middle zone consists of clay seamed by semi-indurated limonitic veins; and basal 20 inches consists of clay seamed by unconsolidated limonitic veins. February 1955. ,3 K 3%: I’ fij’"“ilgéfiffi¢y§3’ , * “a; “va§;4Q?~ntsf§aw j. ‘9', ," ; .. 0.9!: <1? B. Ferruginous concretions at surface of Fefan soils, Ulalu. 195h-55. Plate 25 Bamb crater in Fefan soils, Ulalu. vicinity is about 6 feet below the The water table is this surface. February 1955. Plate 26 Q drainage of the Fefan soils is moderately well to somewhat excessive in the surface gravelly horizon. The clayey substratum, where present, is somewhat poorly drained. The depth to the water table is varied and in some places the water table may be completely absent from the soil pro- file, but, where present, it seems to be at the contact of the soil and bedrock which averages about 3 feet below the surface (pl. 26). Profile descriptions: As the whole soil unit was mapped as a sin- gle slope phase, a wide range in the soil characteristics is inevitable. TWO profile descriptions of Fefan soils are given below. Profile described one-eighth mile north of the pier on Sopuk pen— insula, Mnen (pl. 25 A). This location is also sample site 1 (map 14); see tables 12 and 20 for chemical and mechanical analyses of soil from this site. 0 to 22 inches, dark grayish-brown (lOYR h/2) gravelly clay; clay fraction moderate medium granular structure; porous; friable, slightly sticky; pH 6.5; ferruginous (probably mostly limo- nite) concretions, ranging in size from 2 to 25 mm, make up about ho percent of the horizon; cobble-sized fragments of weakly to strongly cemented ferruginous concretions common in the horizon; numerous roots, mostly breadfruit, permeate the mass; grades abruptly to 22 to #0 inches, light yellowish-brown (lOYR 6/h) clayey material. Clay fraction with numerous medium distinct light-gray'mot- tles; strong medium granular; plastic to slightly plastic; pH 6.0. An intricate coarse reticulate mottling network of one- fourth inch thick veins of semi—indurated, red (2.5YR h/B) ferruginous material divides the horizon into irregularly shaped sections 2 to 5 inches in diameter; internal drainage moderately slow; grades gradually to ho to 63 inches, yellowish—brown (lOYR 5/6) clay or clayey silt with numerous medium to fine distinct mottles of various col- ors from reddish brown through light gray; horizon has net- work of veins similar to that described in horizon 2, but the veins in this horizon are soft; clayey material is strong me- dium granular, slightly plastic, porous; pH 5.5 Profile described on central part of Ulalu. This location is also soil sample site 7 (map ll); see table 12 for chemical analysis and table 19 for engineering test data. 0 to 7 inches, very dark grayish-brown (lOYR 3/2) gravelly clay - about 60 percent clay or clayey silt and ho percent limonitic gravel. Clay fraction moderate medium granular structure; porous; friable; pH 7.0; breadfruit and coconut roots numer- ous; grades gradually to 7 to 15 inches, dark-brown (lOYR u/3) gravelly clay; granular; firm, slightly plastic and sticky; porous; pH 6.5; some roots; gravel-sized limonitic concretions make up about 30 percent of the horizon; grades gradually to l5 to 2% inches, yellowish-brown (lOYR 5/h) gravelly clay; differ- ent from the above horizon in color and in having some aggre- gated limonitic concretionary fragments from h to 10 inches 99 in diameter; pH 6.0; grades gradually to 2h to 32 inches, yellowish-brown (lOYR 5/6) gravelly clay with many medium faint, strong-brown mottles; clay fraction is moderate medium'granular; firm, plastic, and sticky; pH 6.0; grades abruptly to irregular contact of soil and bedrock Range in characteristics: The principal variations in Fefan soils are the depth of solum (l to 8 feet), the presence of the clayey sub- stratum, the texture of the surface horizon (may be gravelly clay or clayey gravel), and the presence of volcanic boulder and rock outcrops. Inclusions of other soils: A few acres mapped as Fefan soils probably contain a lower percentage of limonitic concretions than is normal for Fefan soils. Two such areas mapped on the westward slope of the southern half of Fefan and one area mapped on the tip of the penin- sula east of Wichap village on Moen probably could have been mapped more correctly as gravelly phases of Truk clay. However, because the total extent of this soil was not sufficient to warrant the establish- ment of a gravelly phase of Truk clay, it was more practical to map these small areas as inclusions of the Fefan soils, the soil they next most nearly resemble. One large area of about 30 acres on the summit plateau of the southeast peninsula of northeast T01, is mapped as Fefan soils on soils map 10 and as rockland on engineering materials map 31. This seeming anomaxy is justified because the average gravelly-soil depth of the area is only about 15 inches, the hard pinnacled volcanic bedrock out- crops are numerous, and volcanic boulders are common. Modification of the natural soil: The Fefan soils unit has been altered only slightly by major construction. Small areas, totaling about 10 acres, were used on Ulalu as sites for a large single-story concrete building, a baseball field, and for three radar towers of which only the foundations were completed before the end of world War II. Some of the gravelly surface has been used as road metal on the causeway and the dock on Ulalu (pl. #7). About one-third of the total Fefan soils area was used as gardens by the Japanese, but nearly all of these gardens have since been re- planted to breadfruit and coconut trees by the Trukese. Because of its gravelly surface horizon and of its level to gently sloping terrain, the Fefan soils seem to be very resistant to surface erosion. Only on two small areas located on the west slope of southern Fefan are there watercourses and these are merely extensions of water- courses from higher elevations. Vegetation: Some 70 percent of the Fefan soils unit is forested with coconut, breadfruit, and mango trees; 5 percent is planted in gar- dens, chiefly taro, bananas, and tapioca; and 25 percent supports a shrubby cover. About 60 percent of the largest area of Fefan soil, the southeast plateau of northeast T01, is grown up in shrubs, mostly Hibiscus tiliaceus, and a few mango trees. Utilization: Based on the luxuriance of its vegetative cover, the Fefan soils appear to be one of the most fertile soils on Truk. Even though most of the unit on Ulalu and on the east peninsula of Mben was reportedly cropped intensively by the Japanese, it is still very pro- 100 Plate 27 Boulder talus, Mben. Talus slope about one-fourth mile east of abandoned airfield on southwest Mben. Mbst of the boulders are angular and 3 to h feet in diameter. March 1955. ductive. However, in one area of about 30 acres located on the south- east plateau of northeast Tol, the soil is very shallow, averaging about 15 inches in thickness over volcanic bedrock, and is too droughty, especially during the dry season, for favorable crop production. Aside from this shallow bouldery area, the Fefan soils seem to be well suited for truck cropping or for subsistence farming. However, as long as the present crude agricultural practices are followed, the acreage that can be planted to clean-row crops on the normal family-sized basis is lim- ited to from about one-fourth to one—half of an acre. Uhit 4. Rockland: General features: The rockland in general consists of exposures of volcanic bedrock (pls. 16 A and 55 A) and areas of bouldery talus (pl. 1h) in both of which the unweathered rock composes from 50 to 90 percent of the surface. The bedrock areas are gently dipping lava flows, steeply sloping breccias, and cliff faces; the bouldery talus (pl. 27) is found on steep to precipitous slopes. Rockland is the second smallest soils unit mapped on the Truk Is- lands. It is generally found at altitudes above 50 feet, but in some areas, as along the south side of east Udot, it is exposed at sea level. Topography and drainage: Gradients in the rockland range from nearly level to vertical. It is found on mesas, as on northeast Tol; on gently undulating plateaus, as on northeast Tbl, northeast Dublon Island, and Moen; on rolling slopes, as on the east side of Witipdn on Mben; and on cliff faces and as steep bouldery talus on all the major islands and on many of the smaller islands. Range in characteristics: The unit ranges from level rockland containing small shallow pockets of soil to precipitous bouldery talus and vertical cliff faces. Modification of the natural soil: The level to nearly level areas have not been altered by construction. The cliff faces however, have been extensively used as sites of caves for heavy gun emplacements, am- munition dumps, and tunnels. At lower elevations, the cliff faces have been quarried on some islands. Vegetation: Vegetation on the level rockland is limited to sparse growth of drought~resistant grassland plants, chiefly Dimeria and Gleichenia (pl. 33 B). Bouldery talus generally supports a dense vege- tative cover of breadfruit, coconut, Pandanus, and mango trees; in some areas the luxuriant forest is partly replaced by fitau vines. At the higher elevations, as on the highest part of uman and Mount Thmuital on southeast Tol, the bouldery talus vegetation is predominantly Ficus- Pandanus forest. Utilization: The level rockland areas, where accessible, would be excellent sites for founding heavy structures. Cliff faces, where ac- cessible, are well suited as quarry sites. Bouldery talus, where ac- cessible, is excellent for production of tree crops, such as breadfruit, coconut, and mango. Such areas should also be excellent quarry sites for riprap rock. Uhit 5. Muck and peat: General features: The muck and peat is composed of various depths .101 and percentages of very dark-brown to black organic silty ooze (muck) and brown to reddish-brown, fibrous residues of partially decomposed vegetation (peat). These deposits occur in fresh-water marshes which are found on all the larger volcanic islands, most of the smaller vol- canic islands, and in smaller areas on some of the barrier-reef islands. The largest area of muck and peat is located along the western coastal flat of Moen. Topography and drainage: On the volcanic islands, where the muck and peat deposits are always located along the coastal lowlands, the fresh-water marshes are separated from open sea and from brackish embay- ments by areas of either Shioya loamy sands or mangrove swamps and are bordered upland by one of the volcanic soils. Where found on the barrier-reef islands, the small shallow muck and peat marshes usually occur as shallow elliptical depressions near the centers of the islands, but in some occurrences, as on Mesegon, the marshes occupy elongated depressions immediately behind the lagoonward- facing berm. Profile descriptions: The following profile was sampled at the edge of the currently (1955) used highway on Mben directly across the road from the Trust Territories transportation garage. O to 56 inches, black to very dark-brown (lOYR 2/1 to 2/2) muck and peat; friable and very fibrous; contains some silt and coral sand; water table is at the surface; grades gradually to 56 to 8h inches, light brownish-gray to grayish-brown (2.5Y 6/2 to 5/2) loamy coarse to medium sand; the color grades to a lighter gray with depth. This horizon resembles a Shioya sand profile except its texture appears to be somewhat coarser. The following profile was sampled and described on the low coastal marsh one-eighth of a mile west of the Trust Territories transportation garage and 6 feet north of the currently used highway in an old swamp- taro bed on Mben. O to 12 inches, water 12 inches deep over surface of muck 12 to 2h inches, very dark-brown (lOYR 2/2) mucky ooze or organic matter with some undecomposed plant fibers; pH 7.0 2h to 66 inches, dark-brown (lOYR 3/3) peat and muck; very fibrous with some organic silt; pH 7.0; grades gradually to 66 to 8h inches, dark grayish-brown, medium to coarse loamy sand containing a few coral fragments as much as one-half inch in diameter. Hard pan or semi-indurated layer at 8h inches. A 3-inch penetration of this hard pan with a regular 1-inch hand auger required 50 complete turns with a reasonable amount of pressure. little material could be recovered from the hard pan boring because of the water-logged condition of the profile; pH 8.0 to 8.5 The following profile description was made in a swamp-taro patch about three-eighths of a mile east-northeast of the Oror en Newacho dock area on Moen. 102 {Q C. O to 6 inches, mat of dead reeds, resulting from cutting or clear- ing of Phragmites karka and leaving the material on the sur- face. Water table is immediately under the mat of recently cut reeds. 6 to 12 inches, very dark-brown (lOYR 2/2) unconsolidated fibrous muck and peat; friable; very porous; pH 7.0 12 to 2h inches, very dark grayish-brown (lOYR 3/2) peat and muck; about 70 percent undecomposed plant material, 30 percent very dark-brown muck; friable; pH 7.0; grades gradually to 2h to 72 inches, dark reddish-brown (SYR 3/2) peat and muck; some- what more compact or consolidated than the overlying horizon; fibrous; 70 to 80 percent peat; friable; pH 7.0 to 7.5 72 to 96 inches, very dark grayish-brown (lOYR 3/2), coarse to medium loamy sand with about 20 percent muck and peat. Sand fraction is composed of tiny shells up to 2 mm in diameter; loose, very friable; pH 8.0 to 8.5. Because of the water- logged condition of the profile, it was not possible to re- cover more than minor amounts from this horizon. Range in characteristics: Sampling of the central portion of the larger areas of muck and peat was not attempted because of the diffi- culty of cutting through dense tangled reeds and of the danger involved in wading marshes of unknown depths. Thus, the information concerning the depth to and the composition of the stratum underlying the organic layer is based on minor explorations, mostly within 100 feet of the margin of the marsh. At the sites investigated, the thickness of the muck and peat deposits ranged from about h to 15 feet. The percentage ratios of the muck and peat vary considerably but in general the peat accumulation appears to be more consolidated or matted in a horizon which begins at about 12 inches below the water table and extends down- ward as much as 3 feet. Muck and peat marshes are usually acid; however both the water and the organic material in the Truk fresh-water marshes were neutral to distinctly alkaline everywhere tested. Inclusions of other soils: Some isolated areas of Shioya loamy sands too small to be mapped separately are located in the muck and peat marshes. Also, some small areas of mangrove are probably included in the unit. Mbdifications of the natural soil: Raised roadbeds built with rock and earth fill were constructed across the muck and peat marshes in several places, as on west Mben, southeast Dublon Island, and south Param. Also parts of airstrips and adjacent ramps and parking aprons on north and south Mben, on south Dublon Island and on Param were probably constructed on this unit. Vegetation: The predominant vegetation is Phragmites karka, a giant marsh reed. Scattered small patches of Hibiscus tiliaceus, Pandanus tectorius, and other shrubs are also found in the muck and peat marshes. The vegetation of the unit is discussed more fully in the Vegetation section under the heading Fresh-water marshes. Utilization: During the later years of the Japanese occupation, 103 small areas of the marsh on Dublon Island, Fefan, Ulalu, and northeast and northwest Tol were planted to sweet potatoes. The sweet potato beds were prepared by mounding the peaty fraction into h—foot beds about 1.5 feet above the water table. unfortunately, no production yield data or information concerning the suitability of this type farm— ing are available. It is believed, however, that these areas would produce good to excellent sweet potato yields where the height of the mound is maintained to provide adequate aeration. The Japanese reportedly attempted to grow rice in the muck and peat on west Moen and on Dublon Island but had little success. Accord- ing to the Trukese, the rice in these experimental plots would not head. Whether the failure of the rice to form seed heads was related to the length of day, temperature, intensity of sunlight, or to some elemental soil deficiency is not known. The marshlands are probably best suited to growing such subsist- ence crops as the different varieties of hydrophytic taro. Excavated muck and peat may be used advantageously in establishing lawns and in landscaping. Unit 6. Shioya loamy sands: General features: The Shioya loamy sands unit is deep, light-gray, light-yellow and white, fine to coarse calcareous sand composed of frag- ments of marine skeletons and coral and is stained to a depth of several inches by organic matter. It is one of the smaller soil units mapped on Truk. On Moen the largest single area extends from the north side of Moen village southward about 1,000 yards; its average width is about 100 yards. Another large area of Shioya loamy sand is a strip which bends around the western point of southwest T01 and is 2,500 yards long and averages about 60 yards wide. Inside the Truk Lagoon there are several low reef islands composed entirely of Shioya loamy sands. The unit also comprises parts of most of the barrier-reef islands, but on the barrier-reef islands the loamy sands are usually shallow and in places mixed with cobbly and bouldery fragments of coral. Beaches are included in this soil. Topography and drainage: This soil is excessively drained in the surface 12 inches. It is essentially level (not over 2 percent slopes) and it occupies terracelike benches some 2 feet above high-tide level. On the volcanic islands, Shioya loamy sands are normally bordered by muck and peat marshes or Truk stony clays on the inland boundaries and by either mangrove swamps or the open sea on the seaward side. Where the sand adjoins marshlands, it interfingers with the muck and peat in places for distances of 10 to #0 feet. Profile description: The following representative profile was described near 0ror en Nepung pier on Moen. This is also soil sample site 6 (map 1h); see table 19 for results of engineering tests run on sands from this site and see table 12 for chemical analysis. 0 to 6 inches, dark grayish—brown (2.5Y h/E) loamy sand with vari- ous colors from very dark grayish brown to white; loose; sand fraction poorly grades from fine to coarse and composed of marine skeletons and coral fragments; excessively drained; pH 8.0 to 8.5; organic-matter content responsible for dark color- ing; grades gradually to 10h 6 to 15 inches, grayish-brown (lOYR 5/2), loamy medium to coarse loamy sand; loose sand fraction mostly angular and composed of fragments of marine skeletons and coral; pH 8.0 to 8.5; some dark-colored particles of either minerals or organic matter; grades to 15 to 30 inches, white (2.5Y 8/2), poorly graded fine to coarse sand; loose; pH 8.0 to 8.5; water table probably fluctuates slightly with tides but averages about 16 inches below sur— face Range in characteristics: The greatest variation is probably in the organic-matter content of the surface horizon. A few local depres- sions where the organic-matter content approaches that of some marshy areas and the barren calcareous beaches where organic matter is virtu- ally absent are mapped in the unit. Vegetation: The vegetation of the unit is predominantly very productive coconut trees and a few breadfruit trees. Very few garden sites were seen on the unit. The other plants on this soil unit are listed under vegetation unit 2, strand vegetation. Utilization: About 80 percent of the villages on the islands are located along the seacoast; of these, some 90 percent are located on Shioya loamy sands. - Because of its accessibility and workability, the Shioya loamy sands unit with heavy fertilization, including minor-element supplemen- tation (especially Fe), should be good for production of truck crops that are not extremely susceptible to elemental deficiency chlorosis under alkaline conditions. From an engineering point of view, the Shioya loamy sands unit is very important. It is the only source on Truk from which sand may be obtained easily. The poorly graded, fine to coarse lime sands are sub- rounded to angular. This calcareous sand is rated only fair in making concrete because some of the sand particles are porous and contain or- ganic matter and many of the sand particles are more angular and weaker than more desirable silica sands. However, it probably would make a satisfactory concrete for semipermanent construction if less sand were mixed with the cement than is normal when using silica sand. The Shioya loamy sand has a good bearing capacity. In addition to utilization for village sites (pl. 11 A), coastal roads and trails have been built on it insofar as practical. It is believed that the former Japanese airstrips on Moen, Dublon Island, Param, and Eten were con- structed on areas occupied in part by Shioya loamy sands; but this fact could not be determined with certainty because power augers and core- drilling machines were not available. Exposures of loamy sands, how- ever, were found on the west-southwest end of Mben Airfield on north Moen, on the south side of the west end of the airstrip on Eten, and on the east end of the airstrip on Param. Unit 7. Fill: The fill areas are coastal lowlands that have been fill— ed with volcanic riprap and crushed rock or coral or both, and stabi- lized with clay. Some areas, such as the dock and the seaplane ramp on south Dublon Island, the seaplane ramp and airfield on southwest Moen, the dock on north Eten, and part of the airstrip on Param, were paved with portland-cement concrete. The Moen Airfield airstrip on northeast Moen is paved with coral gravel. 105 With the exception of Mben Airfield, which was repaired during the early postwar period, most of the fill areas contained numerous bomb craters in 1955. The airstrips on Param.and Eten have been partially replanted to bananas and to coconut trees. Some of the bomb craters on northwest Moen have been planted to swamp taro. Dublon Island contains #73 of the total 893 acres mapped in the fill unit (see table 13 for acreage on other islands). Unit 8. Mangrove swamps: General features: Mangrove swamps are the shallow salt-water or brackish-water swamps along the coasts and in embayments. The swamp vegetation consists of maritime trees and shrubs, most of which have branching aerial prop roots. The swamp soils, which are usually sub- merged l to 3 feet at high tide, vary in their composition from loamy coarse and fine sands in the open seaward margins of coastal areas to muck and peat l to h feet in thickness over loamy sands in the protect- ed embayment areas. This soil unit is the third largest soils division mapped in the Truk Islands; its total area is 3,315 acres. The mangrove swamps, ranging in density and size from small isolated spiderlike shrubs to dense tangled thickets or forests of about 300 acres, fringe portions of most of the volcanic islands (pls. 28 and 5h). Swamps of less than 5 acres grow adjacent to some of the lagoon-reef and a few of the bar- rier-reef islands. Range in characteristics: The principal variations in the sub— merged swamp soils are in the texture of the sandy areas and in the thickness of the organic layer in the muck and peat areas. Also, in some areas the vegetation is more dense than in others. Inclusions of other soils: Some isolated patches of Shioya loamy sands that are too small to be mapped separately are included in the mangrove swamps. Mbdification of the natural soil: Many Japanese causeways and, probably, parts of the Japanese airfields on Mben, Dublon Island, Eten, and Param were constructed on areas formerly occupied by mangrove swamps. The Trukese have constructed several coral-boulder piers across the mangrove to the open water as on the north and northwest coasts of northeast Tol, the northeast coast of northwest Tol (Pata), the east coast of southwest Tol (Polle), the northeast coast of south- east Tol, the west side of Fala-beguets, and on numerous other islands. Vegetation: The plants in the mangrove swamps are predominantly Rhizophora mucronata and Bruguiera conjugata, both of which have branch- ing aerial prop roots (pls. 10 A and 297?, A dense forest of these trees forms an almost impassable barrier because their numerous branch- ing aerial prop roots form a thoroughly tangled interlocked mass. Other trees found mostly along the island margin of the units are Xylocarpus granatum, Inmnitzera littorea, Excoecaria agallocha, and Clerodendrum inerme. Mangrove swamps do not seem to be restricted to any side of the island so long as the following factors, which appear to favor their growth, exist: soil submerged from 1 to 3 feet by shallow salt or brackish water at high tide; area protected from strong wave action, 106 Plate 28 Causeway through mangrove swamp, Moen. Japanese —built cause- way from northeast Moen to nearby Upwein island. December 195M. as on the landward side of wide shallow reefs or in protected embay- ments; and soil composed of sand and discernible amounts of organic matter or silt or both. Utilization: The mangrove swamps are of little economic value. The tall slender Rhizophora mucronata is used as rafters and ridgepoles in the construction of native houses and copra sheds (pl. 12) and for carved souvenirs. During their occupation of the Truk Islands the Jap- anese used the Rhizophora mucronata for making charcoal. other species or shrubs in the mangrove swamps are used as firewood for cooking and for smudging. While the mangrove swamp produces no edible vegetation, it harbors the edible black crabs, which measure up to 1h inches between the tips of spread claws. Also, some edible fish live among the mangrove roots in areas that are submerged at low tide. As evidenced by the fair condition in 1955 of the Japanese cause- ways built through mangrove swamps on the southwest and west sides of northeast Tbl, on the south side of southwest T01, and on east Mben (pl. 28), the sandy substratum on the mangrove swamps appears to have a good to fair bearing capacity. The Japanese causeway built through the mangrove forest on southeast Mben, is no longer usable in a number of places; this is believed due more to wartime bombing than to failure of subgrade. 107 Water Resources by Max H. Carson General statement Supplies of fresh water in the Truk Islands are obtained chiefly from small streams, shallow wells, and waterholes and by the catchment of rainwater from the roofs of buildings. The only deep wells are three in the Trust Territories administrative area on Moen, from which part of the water supply for that area is pumped. All surface water and water in open wells and waterholes in the Truk Islands is subject to pollution. In this report, water is con- sidered potable if it contains less than 300 parts per million chlo- rides. No other analysis was made of either chemical or bacterial content. On all of the islands ground water is available from shallow wells or waterholes at, or near, sea level. On some it may be available up to several hundred feet elevation and, if so, would be less subject to pollution and would need little or no pumping. On the low coral islands in the lagoon and on the barrier-reef is- lands, fresh water is obtainable from swamps or marshes near the cen- ters of the islands and from shallow wells or waterholes around the perimeters of the islands. Fresh water is also available on the vol- canic islands from fresh-water swamps and marshes at low altitudes. water from swamps and marshes would have to be led to sumps filtered, chlorinated, and pumped. The absence of streams on the low coral islands and the scarcity of streams on the volcanic islands carrying even a moderate supply of fresh water during dry weather, makes the recovery of ground water the most practical means of supplementing the present water supply on Truk. However, the catchment of rainwater from roofs of buildings and from artificial rain catches could provide an important additional supply of fresh water. Rainfall at the U. S. Weather Bureau station on Mben ranges from 125 to 175 inches a year and the mean annual rainfall is lh7 inches. This would make possible a supply of about 87 gallons a year for each square foot of catchment surface developed. Introduction A rapid general reconnaissance of the water resources of the Truk Islands was made from January 2h to March 18, 1955. The following sum- mary of the results is preliminary to a longer report on water re- sources to be published separately after further field work has been completed. The field work was during the dry season, which generally extends from January through March, and pending a determination of the regimen of the streams and springs, the following comments must be confined largely to that season. The dry season of 1955, reportedly, was unusu- ally severe and, therefore, it may be considered as representing condi- tions approaching the most unfavorable to be expected. The reconnaissance consisted of only a single trip, mostly on foot, completely around 12 of the high volcanic islands and 16 of the low 109 coral islands on the outer reef. The high islands are steep and rugged and, presumably, during heavy rains myriads of small watercourses will cascade down their sides. Discharges were noted of all watercourses containing running water at the time of observation or, in the case of ”seeps”, evidence of very recently running water, and all these are as- sumed to be perennial. However, since rainfall in the high islands of the Pacific characteristically comes in showers over small areas with the higher intensities and frequencies at the higher altitudes, it is possible that some of these ”streams” had been affected by showers in the mountains at the time of observation and are really only intermit- tent. There is a narrow coastal flat practically surrounding each of the high islands which usually widens out at the mouths of valleys and sometimes disappears entirely where ridges jut out into the sea. On the inner edge of this coastal flat there are usually marshes or swamps, into which most of the small streams empty. Villages are built on the high outer edge of the flats. There was not time during the reconnais- sance to follow the streams from source to mouth to determine their ex- act length or position and the points of observation were usually at or near the trail crossings. locations of observed springs, wells, pools or waterholes, and ma- jor swamps or marshes were noted but no claim is made that the list is complete, since it is expected that these features will be studied and reported on by a ground—water geologist. It should be noted, however, that many of the springs and waterholes are hard to find without a guide, as they are reached by trails, known only to the villagers, across the swamps to the base of the mountains and are sometimes con- cealed by dense vegetation. very few of the wells have curbings and these even in the villages are easily overlooked. Only four of the islands had surface streams large enough and so situated as to be of any value as a major water supply. These are Mben, Dublon Island, Fefan, and T01 (maps 1, 2, 5, 6, and 7). Observed dis- charges on the southeastern and Pata peninsulas of T01 and at two points on Fefan were affected by recent rains and were undoubtedly con- siderably higher than in normal dry weather. Elsewhere observations were made during dry weather and the discharges noted are assumed to be at, or near, minimum. At the time of the reconnaissance, moderate to small amounts of surface water were available on Moen in Wichen River on the north side of the island (map 5) and on Tbl in the combined discharges of several streams near the north ends of each of the two southern peninsulas (map 2). Small amounts were available on Mben from the streams back of the Trust Territories administrative area on the northwest side of Mount Teroken (Chukumong); on Dublon Island at the head of Nemonon bay; and on Fefan at the head of the bay, near the middle of the west side. The area at the head of Nemonon bay, Dublon Island, was developed by the Japanese and diversion works, concrete settling tanks, and considerable concrete pipe is still in place so it could be rebuilt rather rapidly, but the amount of water available in dry weather would still be small. No plans showing the layout of the pipe lines are available. Elsewhere in the Truk Islands the streams are small and the discharges were small to meager although streams are numerous and rather evenly distributed on the four islands mentioned above and on Udot and Uman (maps 3 and 7). There are no streams on the smaller volcanic islands or on the low coral islands in the lagoon or on the outer reef. llO (”\ an The dryaweather period runs from January through March and a pro- gram of stream gaging over a period of several years will be necessary to determine the average rates of discharge throughout the year and the rates at which stream discharge subsides as dry weather comes on. Two staff-gage stations were established on Tel, one on Mben, and one on Dublon Island. Mr. Ott, Superintendent of Public Works in Truk for the Trust Territories, was furnished plans for installing additional sta- tions, and expects to establish several on the public water supplies on Moen. Rain gages to supplement the U. S. Weather Bureau gage on Mben were established on Mben, Dublon Island, Eot, T01, and on Pis on the outer reef. It is hoped that the gage on Dublon Island will help to correlate the records of the present U. S. Weather Bureau station with those collected by the Japanese, and that the additional gages will give a better idea of the areal distribution of rainfall. The records from these stream gages and rainfall stations should, after a suffi- cient period of time, make it possible to get a clearer idea of the regimen of the streams and springs and of the amount of water that sinks into the ground to augment the supply of underground water. The fresh-water swamps and marshes common along the inner edge of the coastal flats are a source from which fresh water can be obtained at low altitudes. Many of the marshes are used by the natives for grow- ing taro, but even there the taro grows among tall marsh grasses and small trees. Water from these sources would have to be led to sumps by trenches, filtered, chlorinated, and pumped. Recoverable ground water is available on all the islands and in most cases could be developed rapidly. Shallow wells are feasible al- most anywhere at low altitudes. In some localities, there appeared to be possibilities of grounddwater development at relatively high alti- tudes. Indications are that the ground water will be well within stand- ards of potability so far as chlorides are concerned (see table 15), but the low-level shallow ground water will almost certainly require chlorination, probably filtration, and will, of course, have to be pump- ed. If high-level water can be developed the danger of pollution will be less, the water should be clear, and less pumping will be required. Small springs and seeps occur at elevations from sea level to several hundred feet but those observed were meager and they do not appear to be a likely major source of water supply. The whole groundawater prob- lem should be studied by a ground-water geologist to determine the best methods of ground-water development. If high-level water is available, there should be careful mapping of perched formations so that attempts at development will not destroy them. A study of safe yield should be made of low-level water so as to avoid the danger of intrusion by sea water, and the possibility of securing water from deep wells should be investigated. There are no streams on the coral islands in the lagoon or on the outer reefs, but on nearly all of them there are fresh-water swamps or depressions near the centers. Wells around the edges of the swamps and in the depressions will yield fresh water in small quantities, but here there is most certainly danger in overpumping and chlorides should be carefully watched. As most of the islands lack streams carrying even a moderate sup- ply of fresh water during dry weather, the possibility for developing ground water is an important part of the water supply problem in Truk. However, one other source of fresh water should not be overlooked. lll This is catching rainwater on the roofs of buildings or other relative- ly impervious surfaces. Most of the fresh water used by the natives for drinking and cooking they catch from their roofs. Water from streams, wells and waterholes is used almost exclusively for washing /" clothes and for bathing. On the island of Ponape, where the rainfall is somewhat heavier than in the Truk Islands and there are streams of considerable size, the entire water supply for Kblonia, the capital of the island, runs off an airfield (now abandoned) through a concrete ditch to settling and filtration basins, and thence through a pipeline to the town. Rainfall at the U. S. Weather Bureau station on Moan averages about 1&5 inches a year. At 0.6 gallons per square foot of catchment area per inch of rain this gives about 87 gallons a year per square foot of catchment area. Storage to carry over from one rain to another would have to be provided, and this would vary, depending on the season of the year and the size of the catchment area. A study of the rain- fall frequency figures in figure 6 will give some idea of the condi- tions to be met. Since this station is near sea level it is probable that rain at higher altitudes is heavier and more frequent. (Also see (;-\ Climate chapter.) Eastern islands Mben: The administrative headquarters of the Truk district, Trust Ter— ritory of the Pacific Islands, is on Mben. There are two small streams on the northwest slopes of Winifourer (maps 5 and 6) from which water is taken, by gravity, for the water supply of the administrative area. They are reported to furnish an adequate supply 8 months out of the year. Hewever, during March 1955, their combined flow dropped to about ho gallons per minute (g.p.m.). Wichen River, the largest stream in the Truk Islands, drains the north flank of Winifourer and Witipdn mountains just over the ridge from the administrative area. A. M. Piper, U. S. Geological Survey geologist, called attention to the pos- sibility of utilizing Wichen River in the following words: 'About O.h road miles upstream from its mouth, this creek affords a site for a short dam with foundation and abutments in dense, fresh basalt; also a reservoir site of considerable capacity .... Catchment area above the dam site is estimated - as 350 acres; thus the potential yield per inch of rain sal- ( vaged would be about 9.5 million gallons. Uhder these con- WW' ditions, development of a firm dry-season yield of several hundred thousand gallons a day seems entirely feasible. This site for a suggested dam is about 1.3 miles nearly due east of military-government headquarters and about 0.6 miles from the fringing reef along the north shore of the island. Accordingly, pipelines of moderate length would reach any prospective developments in the northwest part of the island. Because the dam site is only about 75 feet above sea level, a pump station and a pressure tank or reservoir on the ridge to the west would be necessary. Thorough engineering inves- tigation of this suggested development is believed warranted.” (A. M. Piper, unpublished references, l9h6-l9h7) In March 1955, during the extremely dry season when there was rig- id water rationing in the administrative area, Wichen River was flowing about a quarter of a million gallons a day. 112 On March 11, 1953, Theodore Arnow, U. S. Geological Survey geolo- gist, in a letter to the High Commissioner of the Trust Territory, re- porting on the condition of the public water supply for this area, made the following comments on the available ground water: "During the dry season,_however, plant 2 received water from drilled well number 2 [map 5, grid reference 7362327 which is pumped 2h hours a day at the rate of 30 gallons per minute. "(2) There is a well-developed seepage area on the north slope of Mount Teroken adjacent to the pipeline leading to the storage tanks of water plant 1 [map 6, approximately 73823é7. Water from this seepage area could be easily divert- ed to the pipeline, thus providing an additional flow of sev- eral thousand gallons a day.” He recommended the following steps to develop additional ground water: ” 6) Drill one or more additional wells in the Nob Hill area Trust Territories administrative area7. These wells should be deep enough to penetrate the fragmental tuff layers that are interbedded with the massive basaltic rocks that make up most of Mben Island. Judging from the geology and the performance characteristics of the existing wells, the new wells, even though they penetrate far below sea level, could be expected to yield fresh water perennially if they are pumped with the least practical drawdown - that is, lightly and steadily rather than heavily and intermittently. ”(7) The coastal flat west of the administration area extends inland to the base of the upland on which the hotel is built. The flat is a raised beach deposit of coralline sand and earthy detritus that probably is underlain by reef limestone. Such beach deposits are normally very permeable and the existence of a large fresh-water swamp on the flat Vsuggests that much of the underground drainage from the north- west flank of Mbunt Teroken is being held close to the ground surface by the less permeable underlying platform of reef lime- stone. It would be possible to utilize this water by the con- struction of large diameter shallow dug wells or horizontal galleries from which the water would be skimmed off the surface in order to prevent the possibility of drawing in salt water. water obtained in the coastal flat could be pumped up to the storage tanks at water plant 2 or could be pumped directly to the dock area. "(8) Several hundred yards south of the hotel, on the northwest flank of Mbunt Teroken overlooking the coastal flat, the Japanese developed a small source of water supply. It consists of a concrete sump and spillway by means of which ground-water seepage is diverted to a small surface stream. The sump is at an altitude of about ho feet and therefore there will be no possibility of salt water infiltration. If the sump were enlarged to increase the rate of infiltration and provide additional storage it might be possible to service the complete dock area from this source and also to provide additional water for the administration area." l/ 17 Arnow, Theodore, March 11, 1953, letter to High Commissioner of Trust Territory reporting on public water supply of Truk Island. 113 Besides the three streams mentioned above there are five small streams on the north side of the island, five on the west, and four on the east side of the southern spur, none of them, however, appeared to be of much importance at the time of my visit. Two springs on the west side of the Tanaachau mountain are at about 50 feet altitude and three on the north side are at about 25 feet altitude. On the ridge between the administrative area and Peniesence there is a small spring [map 5, 7512h27 at about 250 feet altitude that supplies water to Saint Cecelia Seminary (Girls) and one [map 6, 7672357 on the north side of the eastward ridge, about 1 1/2 miles west of the east tip of the island, at about #00 feet altitude. Other springs observed on the north side of the eastward ridge are; one at about 50 feet altitude about a mile west of the east point, one at about 25 feet altitude about two-thirds of a mile west of the east point, one at sea level about a half-mile west of the east point, and one at about 25 feet altitude about a quarter-mile west of the east point. Two small seeps were seen on the east side of the southern spur of the island at 50 feet altitude. None of the springs, except the one above Saint Cecelia Seminary, were yielding more than a trickle of water at the time they were observed. They do, however, indicate the presence of perched water in the areas and at the approximate altitudes noted. Wells and waterholes are scattered along the western shore and a- long the western half of the northern shore. There are two springs at about 100 feet altitude in the saddle near the east end of the island, probably indicating high-level ground water at that location. There is a well near sea level just south of the saddle and a small well at the eastern tip of the island. Two caverns, excavated in the side of the hill east of the former airfield on south Moen, at altitudes of about 80 and 100 feet contain standing water supplied by seepage from the sides and roofs. Dublon Island: There follows a report, dated February 18, l95h, by Theodore Arnow to Dan A. Davis, District Geologist, Ground Water, U. S. Geological Survey, Honolulu, on the water supply for Dublon Island (maps 6 and 7): "I was on Dublon on February 25 and 26, 1953, which is during the dry season. The coastal flat bordering the south flank of Mbunt Tolomen ranges up to 300 feet in width and con- tains many marshy areas because the water table lies at, or very close, to the surface The Japanese had developed an ex- tensive system of surface concrete drains in Nukura to carry the excess seepage out to sea. TWO large wells (6-8 feet in diameter), with masonry casing were seen and there are also numerous 12,000-gallon concrete cisterns scattered about. Several of the native houses have running water piped from seeps at the top of Mount Tolomen. Many wells could be de- veloped along the coastal flat and infiltration galleries or trenches could be developed along the toe of Mount Tolomen. The water obtained from such trenches would be primarily drain- age from Mbunt Telemen and there would be little danger of salt-water infiltration. "Fanis Spring [map 6, approximately 767lh17 is at an ele— vation of about 300 feet on a plateau on the south flank of Mbunt Tolomen overlooking NUkura. water issues from the ground in a stone-cased sump which is four feet in diameter, llh (Japanese construction) and about 3 feet deep. The water is piped 10 feet to a mortar sump which is about 3 feet square and then is piped part way down the hillside. About 800 additional feet of pipe would be required to carry water to Nukura. The flow of the spring was measured early in Janu- ary by Trust Territory personnel to be 10 gallons per minute. I measured the flow on February 25 as 2.5 gpm (using a Parshall flume). The chloride content was 12.5 ppm. "There is a 200,000 gallon steel tank inland from the pier. East of the main pier is a Japanese fuel pier. Inland from this is a concrete tank with a steel inner lining which supported a roof which is now gone. The tank is buried flush in the ground. It is 31 feet deep (measured) and 100 feet in diameter (estimated). It is now full of rain water but was originally a fuel oil tank. Excellent storage tank. "The Japanese constructed a filtration plant at the foot of the northeast side of Mount Tolomen. The water enters a concrete tank about 30 x 30 x 9 feet via a buried transite 10- inch main. The tank has two concrete baffles. The water then drops by gravity to three concrete settling tanks which are approximately the same size as the first tank. Each of the three settling tanks has an outlet through a separate concrete sump in which there is a weir. The water then flows by gravity to another concrete tank which contains a single baffle. This tank is about 20 feet square and 12 feet deep. The water is pumped from this tank. The pumps are in place but are no longer usable. None of the tanks are now covered but native informants state they were originally possessed of thatch covers. The total calculated storage for the plant is 250,000 gallons. 'Ehe water is pumped from the filtration plant to two concrete tanks on the east flank of Mbunt TOlomen, at an ap- proximate elevation of 300 feet. The tanks are each ho feet square and 12 feet deep and thus have an approximate storage capacity of 2h0,000 gallons. The tanks are covered only by a screen mesh which held thatch or some type of camouflage. Presumably from these tanks the water was distributed to ' service. Native informants Spoke of another, larger buried tank above the last two, but I didn't see it and am.not abso- lutely certain that it exists. "The main sources of water for the filtration plant are two springs that originate on opposite sides of the valley between Mbunt Tolomen and Mount Foukenau, one spring on the flank of each mountain. Both Springs have been developed by the Japanese - concrete sumps and drainage area - and the flow of both coalesces to form the Tumunu River which now flows out to sea. Formerly, most of the water had been piped off to the filtration plant. A measurement by Parshall flume on the Tumnnu about 100 feet upstream of the bridge (by means of which the cross-island road passes over the river) on February 25, 1953, showed 89 gpm. The Japanese started to build a concrete dam across the valley between Mount Tolomen and Mbunt Foukenau in order to dam up the flow of the TUmunu River. The dam had been constructed half way across the valley when work ceased due to World War II. "A second source of water for the filter plant is a small spring northeast and above the filter plant on the flank of Mount Tolomen. The Japanese developed it with a concrete sump 115 and drainage area and native informants state that the water formerly was piped to the filter plant, now flows under the road between the previous stream described and Thmunu River. The flow was measured on 26 February, 1953 by Parshall flume to be ll gpm. ”Native informants said that the flow of all springs is flashy and responds rapidly to fluctuations of rainfall. "According to native informants, the entire piping system is buried and of transite construction. At my request, Mr. Kan Adatani, a Japanese national employed by the Trust Terri- tory, attempted to obtain a piping diagram in Japan. He was informed that copies of the diagram had been only on Truk and in the Naval Headquarters Building in Tokyo. Both were de- stroyed." l/ Three water development tunnels at about 50 feet altitude were discovered back of the concrete cisterns near Nukura, mentioned in Mr. Arnow's second paragraph. These were caved-in and overgrown with vege— tation and it is believed several others would,be found by thorough search. Undoubtedly they supplied at least part of the water for the cisterns. The streams Mr. Arnow mentioned as supplying the filter plant are at the head of Nemonon bay. Almost directly opposite these, on the west side of the island, are three small streams, which when observed in February, 1955 were flowing an estimated 6, 3, and h g.p.m. One stream on the north side of the island was flowing about h g.p.m. add one on the south side of the island about 1 g.p.m. Near Kutua Point, at about 100 feet altitude, is a group of four springs and at the top Mbunt Drikobosu, back of these springs, are sev- eral concrete tanks or cisterns, the concrete foundations of buildings, remains of a Japanese bath house, sidewalks, and other evidence of Jap- anese occupation. The four springs mentioned above probably supplied part of the water for this settlement, though it is reported that they also collected rainwater from the roofs of their buildings to fill their cisterns. Near Uhun en Nekuk (point) there are three small springs at about 25 feet altitude. In the Penior area there are seven or more shallow wells (not all of which are plotted) at only a few feet above sea level, and one small spring at about 30 feet altitude. The extent to which the springs and wells on this island can be developed for augmenting the meager amount used by the natives will have to be determined by a ground-water geologist. Fefan: Fefan (map 7) has six small streams on the east side, seven on the west, and four on the north. Nine of these (four on the west and five on the east) are clustered around the saddle between Chukuchap and Chukusou mountains. Stream.discharges ranged from 2 to 5 g.p.m. on the east and 10 to 20 g.p.m. on the west. In either of these two groups (the one on the east or the one on the west) the discharges might be combined to form a single supply. This grouping of streams around the saddle in the middle of the island suggests the possible presence of high—level ground water, which should be investigated. There are Springs at 25 to 30 feet (7.5 to 9 meters) altitude along the southwestern face of Chukuchap, the western side of Mbunt l7 Arnow, Theodore, February 18, l95h, memorandum to Dan A. Davis, District Geologist, Ground water, U. S. Geological Survey, Honolulu, T.H. 116 Iron, and at around 50 feet (15 meters) altitude in the Wininis area. There are also two sea-level springs on the western shore below Mount Iron. On the southern end of the island there are springs from 10 to 50 feet (3 to 15 meters) in altitude along the northwestern and western side of Winifouno, and, at least one on the eastern side of Winifouno. A few wells, mostly at low altitudes, are scattered between the streams and Springs but they are not common. They do, however, indicate the presence of low-level ground water obtainable from wells. Param; (map 7) There are no streams on the island and springs are scarce. Only four low-level wells were seen. Extensive fresh-water marshes on all three sides of the triangular island, a rather large fresh-water pond back of the former airfield, and the small population probably account for the scarcity of wells. Relatively large quanti- ties of fresh water could be secured from the pond and marshes. Tarik: (maps h and 7) There are no streams on Tarik. One spring at about 30 feet altitude on the southeast side yields about 0.5 g.p.m. and there is one well on the northwest side. These are almost directly opposite each other on the sides of the southern hill. Tsis: (map 7) There are no streams on Tsis. Three springs at about 90 feet (27 meters) altitude flow from the sides of Winipou mountain, two on the west, and one on the east; and there is a sea-level Spring on the east side of the hill. There are two low—level wells on the west sides of the north end of the island, one on each side of the north end of Winipou and another north of the sea-level spring. There is a large fresh-water marsh on the north end of the island. Uman: (map 7) Three small streams flowed southeast, one north, one northwest and one west, all from the central mountain mass of Mount Uroras. Their discharges were estimated at from less than 1 to 6 g.p.m. There is one spring on the northeastern spur of Mount uroras and one on each side of the northern Spur, all at about 25 or 30 feet altitude. Several wells have been dug back of the fresh-water marsh on the east central coast and a few wells and waterholes on the northeast edge of Mount uroras and back of a freshawater marsh at the north end of the island. There are fresh-water marshes at the north and south ends of the island and also on the east coast. No springs, wells, or other evidences of ground water were seen along about the southern two thirds of the west side of the island. This stretch of the coast has little or no coastal flat and the moun- tains come right down to the seashore. Central islands Udot: (map 3) Eight small streams flow down the sides of 79h-foot Uitonap mountain (2h2 meters) at the western end of the island: two on the south, one to the west, three to the northwest, and two to the northeast. The one on the west and the northernmost of the three on the northwest were estimated to be discharging 10 to 12 g.p.m. The others were estimated at less than 1 to h g.p.m. A stream on the west side of the central peak was discharging about 6 g.p.m. and one on the northeast side of the central peak about 20 g.p.m. Four small springs at 20 to 50 feet (6 to 15 meters) altitude were 117 observed on the western end of the island and one at about 50 feet al- titude at the eastern end. There was also a spring at about 150 feet (h6 meters) altitude on the northern spur of the central peak. Four waterholes at the eastern end of the island were almost dried up. Between the central and eastern peaks of the island there is a considerable area of fresh-water swamp in which the water table stood some 10 to 20 feet above sea level. Several shallow wells and water- holes had been dug around the edge of this swampy land. Western islands Tol: (maps 1 and 2) Tol at the western end of the high islands com- prises four land areas separated by mangrove swamps through which boat channels have been cleared. These are Pata, the northeastern, the southeastern, and Polle peninsulas. Pata is on the northwest and Polle is on the southwest. On January 28, the day the southeastern peninsula was visited, 1.3 inches of rain fell and more rain fell during the night. Pata peninsula was visited on January 29. So observations on these two peninsulas were not typical of dry weather. On Pata there are three streams on the northeast and five on the south sides. Al- though the discharges from these streams were undoubtedly increased by the effects of the rain the preceding day, two streams (map 1, streams 2 and 8) in the valleys between Berg Faumuig and Berg Fangaden on Pata appear to be pretty good streams. The northeast peninsula is a doublet lying in a northwest-southeast position, the two parts separated by a low isthmus. There are two fairly good streams on the west side of the part northwest of the isthmus, one discharging at the time of observa- tion 25 g.p.m. and the other 76 g.p.m. However, the larger stream was visited after a heavy rain, and the normal discharge is probably around 25 g.p.m. On the southeastern half of the doublet comprising the northeast peninsula there are three small streams on the southwest side and two on the northeast side. One discharging l3 g.p.m. to the southwest and the two flowing to the northeast at 67 g.p.m. and #5 g.p.m. respective- ly are probably Spring fed. The other two flowing to the southwest are insignificant. On the southeast peninsula there are four streams on the north and northeast and seven on the west side. Although the dis- charges observed at the time of the visit were considerably larger than they would have been had it not been raining, the two close together at the northern end of the east side and the three at the northern end of the west side had the appearance of being of a more permanent character than the others. On Polle there are three streams on the east side, four on the south and nine on the north. One on the east was discharg- ing about 225 g.p.m., two on the south and two on the north about 112 g.p.m. each. The others on Polle ranged from less than 1 to about 10 g.p.m. Springs ranging from 10 to 50 feet altitude were noted on the western and northern tips of Pata, on the northern edge of the north- east peninsula, at the southern tip of the southeast peninsula, and at the eastern and western ends of the south side of Polle. High-level Springs at about 250 feet altitude were seen in the southeast hills of the northeast peninsula around the head of the large valley south of Mount Unimor and on the northeast side of this same crest. TWO springs are reported near the top of Mbunt Tumuital but were not observed. A few wells and waterholes, at low altitudes, were observed near the 118 north end of the northeast peninsula and along Netutu channel, at the north point of Pata and, on Polle near the south point, the west point and the northeast. But in general wells are scarce on T01. There are rather extensive fresh-water marshes near Netutu channel, on the east side of the southeast peninsula, and on the south side of Polle. Fala-beguets: (map h) Only two small streams were found on Fala- beguets, both on the west side of the island; one discharging an esti— mated 6 g.p.m. and the other only 1 g.p.m. There are numerous wells at the northern tip of the island and others scattered rather closely along the west side, most of them near sea level. A few at the north- ern tip of the island are 10 to 30 feet above sea level and one tunnel contains standing water. Two springs at about 15 feet altitude were seen, one on either side of the southern tip of the island. Ulalu: (map 3) No streams were observed on Ulalu, but five springs are rather evenly distributed around the crown of the island and a large well with concrete sides and curbing near the center of the island con- tains water standing 5 or 6 feet below the surface of the ground. There are also five low-level waterholes near sea level. The marsh in the southeast corner consists of two distinct environ- ments. The part west of the causeway is partially mangrove in somewhat brackish water. The part east of the causeway is entirely fresh water, due probably to the causeway acting as a barrier to brackish water from the west. Table 15. Chlorides of ground-water samples, Truk Islands location Chlorides (in of sample parts per million) Remarks T01 map 1, 436165 12 Well map 1, M5163 12 Well map 1, h5017l+ 56 Well map 2, 1.77110 8 Marsh Outer-reef islands Iamoil #1 164 waterhole Pis #1 62 Well Pie #2 62 Well Ushi 1,311 waterhole Tora #1 18h waterhole Salat #1 100 waterhole Salat #2 300 Marsh Fanan #1 220 waterhole Masegon #1 3O waterhole MBsegon #2 6O Waterhole Ollan #1 8h waterhole Ollan #2 79 waterhole Outer reef islands The outer reef was visited February 20-26. During this time nearly all the islands on the outer reef were visited. There are no streams 119 on any of them and no springs were noted. All but two or three of the smallest islands have one or more wells or waterholes on them and most have fresh-water swamps near the centers. Samples were taken from 11 wells or waterholes and one marsh and were examined for chlorides f"\ (table 15). All but the one on Ushi and the marsh sample contained r less than 220 parts per million (p.p.m.) of chlorides. The Ushi sample contained 1,311 p.p.m. but it is probable that even there fresh water can be found. The swamp sample contained only 300 p.p.m. In general, therefore, it may be assumed that as far as chlorides are concerned there is potable water available on all these coral islands. Such water is close to the surface of the ground and, in the swamps, at ground level. It should be remembered though that it is all subject to pollution, and the water in the swamps and most of the wells and water- holes would need to be filtered and chlorinated. 120 Eggetation by James E. Paseur General statement The vegetation of Truk Islands is tropical. The volcanic uplands are covered by three principal vegetative types. The summits and pre- cipitous slopes of the higher mountains support semiopen to dense for- ests of banyan and Pandanus trees entwined with vines and shrubs. The somewhat less precipitous slopes at intermediate and low altitudes, that were cleared and planted to subsistence crops by the Japanese dur- ing the last 2 years of World War II, are covered with various types of grass and shrub vegetation. A third upland vegetative type, also found at intermediate and low altitudes, is composed mainly of coconut-bread- fruit mixed forest. Three vegetative types grow on the coastal lowlands and the reef islands. The fresh-water marshes support a dense growth of tall slen- der marsh reeds interspersed with scattered shrubs. The sandy coastal lowlands and the reef islands are covered with forests consisting prin- cipally of coconut pahms and shrubs which, on the barrier-reef islands, are admixed with occasional breadfruit and Pisonia trees. The low coastal-fill areas support a wide variety of vegetation - coconuts, marsh reeds, short grasses, and shrubs. Mangrove trees grow within and slightly below the intertidal zone around parts of all the major volcanic islands and, to a smaller extent, adjacent to some of the barrier-reef islands. Description of vegetation units Okabe (l9h2) studied the vegetation on Dublon Island and reported having seen 298 species belonging to 252 genera and 90 families. Table 16, Vegetation of the Truk Islands, contains the following information about the principal plants: scientific names, Trukese and English names (when known), growth habits and uses, and vegetation unit in which plants are growing. The vegetation units are shown on maps 16 through 22. Unit 1. Mangrove swamp: The mangrove-swamp vegetation, which is com- posed principalLy of Rhizophora mucronata and Bruguiera conjugata with xylocarpus granatum, lumnitzera littorea, Excoecaria agallocha, and Clerodendrum inerme growing along the inland margins of the swamps, is described under soils Uhit 8. The mangrove vegetation is sufficiently dense in many areas to form a closed canopy. However, because of the inverted conelike growth of the Rhizophora trees which average about 25 feet tall, the average height of the closed canopy is about 10 feet. Horizontal visibility is limited to about 20 feet; horizontal and vertical concealment are gen- erally good for foot troops. The branching aerial prop roots of Rhizophora mucronata and Bruguiera conjugata form a tangled mass that is impassable to amphibi- ous vehicles and is practically impassable to foot troops. Some trees growing in the mangrove swamps are suitable for con- struction. The long slender Rhizophora, which seldom exceeds 6 inches 121 BET Table 16. Vegetation of the Truk Islands Scientific name Trukese name English name Growth Remarks Occurrence habit by unit Artocarpus altilis mai, echer breadfruit tree lumber and edible fruit 2, 5, 6 Barringtonia asiatica kun tree Fruit used to stupify fish and to cauterize wounds 2 Bruguiera conjugata wong mangrove tree tree Sap used to repaint canoes l Cassia occidentalis stinking weed or herb Pest h, 5 negro coffee Chloris inflata finger grass grass Wasteland pest 5 Clerodendrum inerme apwoch shrub Grows in mangrove swamp l Clinostigma carolinensis kiniau pahn tree 7 Cocos nucifera nu coconut tree Edible fruit a source of potable water; trunk may be used in hasty fortifications, short piling; fronds suitable for temporary camouflage 2, 6 Colocasia esculenta swamp taro herb Cultivated for edible tuber 3 Cyperus sp. sedge herb Fest 3 Cyrtosperma chamissonis giant swamp taro herb Cultivated for edible tuber 3 Derris elliptica up derris herb Poisonous plant; root and stems used for poisoning fish and insects 6 Dimeria grass 5 Eleocarpus tree Durable lumber 7 Eleusine indica goosegrass grass Wasteland pest 6 Excoecaria agallocha ausus, usus poison mangrove tree Poisonous sap l Ficus prolixa au banyan tree 7 Flagellaria indica nikasuk vine Used by Japanese for making baskets and fish traps 6, 7 Gleichenia linearis staghorn fern herb Wasteland pest 5, 7 4‘9 SD Sat Table 16. Vegetation of the Truk Islands (continued) Scientific name Trukese name English name Growth Occurrence habit by unit Hernandia sonora akurang tree 2 Hibiscus tiliaceus sapwo tree Small tree or shrub used some in native construction 2,3,h,5,6,7 Ipomoea pes-caprae sea-beach morning- vine Wasteland pest 2 glory or goatsfoot morning-glory Ischaemum muticum fetinniap grass Can be used to limited extent for dunnage 5 Jussiaea suffruticosa aukenipwin herb 3 Lantana camera herb Obnoxious thorny pest 5 leucaena glauca koahaole shrub 5 (rare) Inmnitzera littorea adhoro mangrove tree tree 1 Macaranga carolinensis tup shrub 5 Mangifera indica mangko, kangit mango tree Edible fruit 5, 6 MBrremia peltata fitau vine Coarse climbing vine 5, 6, 7 Metroxylon amicarum rupung ivory nut tree Fronds used in thatching; trunks may be used as short pilings 3 Miscanthus floridulus aset swordgrass grass Leaf-blade edges bordered with very sharp cutting barbs S Mbrinda citrifolia nopur tree 2, h Musa spp. uch bananas herb Cultivated for edible fruit h Pandanus tectorius fach screwpine tree 2, 3, 6, 7 Paspalum conjugatum fetin hilo grass grass Suitable for grazing 5 Paspalum sp. grass h Passiflora foetida pompom passionflower vine Pest h, 5, 6 Pamphis acidula engi tree Small strand tree or shrub, temporary camouflage 2 WEI Table 16. Vegetation of the Truk Islands (continued) Scientific name Trukese name Englisn name Growth Remarks Occurrence habit by unit Phragmites karka grass Tall, coarse, close-growing fresh-water marsh reed 3, h Pisonia grandis mok tree Large softwood tree restricted to the sandy portions of coastal lowlands and reef islands 2 Remirea maritima sedge herb 2 Rhizophora mucronata chia mangrove tree tree very difficult to penetrate because of numerous branching aerial prop roots 1 Scaevola sericea not shrub Small tree or shrub common along strand or beach; suitable for camouflage 2 Scleria sp. nikaunoun, sedge herb Pest with cutting barbs in leaf edges h, 5 amana, moirer Sida rhombifolia sioinen Queensland hemp, herb Wasteland pest 5, 6 iron weed Sonneratia caseolaris saras pagatpat tree Grows in mangrove swamps l Sporobolus virginicus dropseed grass Tough procumbent grass found along open sandy beaches 2 Stachytarpheta indica sakura false vervain herb Wasteland pest h, 5 Thespesia populnea pono Pacific rosewood tree WOod used for carving, suitable for temporary camouflage 2 Vigna marina wonjika vine Procumbent legume common along calcarous sandy beaches; good for permanent camouflage if soil is alkaline 2, h Wedelia biflora atiwot herb Found mostly in cleared areas; suitable for permanent camouflage 5 xylocarpus granatum punopun mangrove tree tree Produces round "cannon ball" fruit and tiny white flowers 1 "A 5 3 ”0 Plate 29 Mangrove swamp, Moen. The plants in center and right background are either Rhizophora or Bruguiera, which have aerial prop roots- Spikelike breathing roots in foreground belong to Sommeratia casiolaris (native name saras) shown in extreme left background. April 1955. 63“ Plate 30 A. Swamp taro patch, Udot. Young swamp taro (Cyrtosperma) in muck and peat marsh. Dense brush in marshland in background. l95h-55. B. Closeup of swamp taro, Udot. Cyrtosperma chamissonis in margin of muck and peat marsh. 1953-55 . in trunk diameter, can be used in hasty fortifications, foxhole covers, and, in emergency cases, as cribbing timber and as short piling. One tree, Sonneratia caseolaris (native name saras), which attains a height of about 50 feet and a trunk diameter of 15 inches, has spike- like roots (pl. 29) whose function is not known but is believed to be related to aeration. The spikelike roots, which average about 1 inch in diameter, protrude vertically 8 to 12 inches above low-tide level in a radius of about 12 feet around the base of the tree. Saras is found mostly near the inland margin of the swamp. It is probably suitable for bridge timber and other construction. However, because the saras trees occur as widely separated or isolated individuals in the mangrove forests, they are a relatively unimportant source of construction mate- rial. Unit 2. Strand vegetation: The strand vegetation, which grows on the coastal-lowland sandy soils and on the reef islands, is found in vari- ous combinations and densities. This unit consists chiefly of the fol- lowing plants: Cocos nucifera (coconut), Pisonia grandis, Artocarpus altilis (breadfruit), Mbrinda citrifolia, ThesPesia populnea, Hibiscus tiliaceus, Barringtonia asiatica, Pandanus tectorius, Scaevola sericea, Hernandia sonora, Remirea maritima (sedge , Pemphis acidula (shrub), Sporobolus virginicus (grass), Vigna marina, and lppmoea pes-caprae (goatsfoot morning-glory). Coconut trees are the most abundant and com- monly dominate all other vegetation in height (pl. 7 B); the mature trees (20 years old) average 50 feet tall. Locally the giant Pisonia grandis is taller. 0n Ollan, a barrier-reef island on the southwest side of the lagoon, the Pisonia grandis tree attains 60 feet in height and measures from 10 to 12 feet in trunk diameter at the base. Small patches of breadfruit on Pis on the north side of the barrier reef com- pete with the coconuts in height. The vegetation generally is not dense enough to form a closed can- opy except in small neglected areas where the coconuts are spaced as close as 10 or 12 feet and locally where the coconuts are growing with Pisonia grandis or with breadfruit. However, vertical concealment for foot troops is fair to good in most parts of the unit (pl. 9 A). Hori- zontal concealment from the sea is good in undisturbed marginal vege- tation such as found around the barrier-reef islands (pls. 17 A and 20 B); it is generally poor in the vicinity of seacoast villages. This unit contains some timber suitable for construction. Coconut trees are abundant and may be used as cribbing timber and as reinforce- ment in hasty fortifications. Coconut logs can be used in emergency cases as short piling. Breadfruit trees make suitable bridge timbers. Uhit 3. Fresh-water marshes: The fresh-water marsh unit is mapped on all of the volcanic islands except Eten, Eiol, Fala-beguets, Yanagi, and Faneu. The following plants are the chief constituents of the fresh-water marshes: Phragmites karka (tall reed grass), Cypgrus sp., (sedge), Jussiaea suffruticosa, Metroxylon amicarum (ivory nut), gy§tosperma chamissonis and Colocasia esculenta (cultivated swamp taro , Hibiscus tiliaceus, Scleria sp., and Pandanus tectorius. They are usually found in combinations, but occasionally Phragmites karka, gyrtosperma chamissonis, or Colocasia esculenta is found as a pure stand. Small areas, mostly along the margin of the marshes, are cleared and planted to swamp taro, Cyrtosperma chamissonis (pl. 30) and Colocasia esculenta. 125 Except for a few small patches of Hibiscus tiliaceus and the scat- tered shrubs of Pandanus tectorius, the marshes have no closed canopy. The Phragmites karka, which averages about 12 or lh feet tall, is close growing; in some areas individual reeds are as close together as h or 6 inches. These reeds would offer good horizontal concealment and prob- ably good to poor vertical concealment to foot troops. The fresh-water marsh unit is relatively unimportant as a source of materials used in construction. Phragmites karka is used to a limit- ed extent by the natives in weaving walls for temporary shelters. The ivory-nut (Metro§ylon) fronds are used extensively by the natives for thatching material. Plate ll B shows a native weaving an ivory-nut frond to be used in the shingle type of thatching. The value of ivory- nut trees as cribbing timbers or piling is not certain but is believed to be at least equal to that of the coconut tree. Both Hibiscus and Pandanus are too small to be used in construction, but may be used as firewood. NUmerous areas, measuring from 100 square feet to half an acre, are cleared and used for growing swamp taro, Cyrtosperma chamissonis and Colocasia esculenta. These plants are used mainly as an emergency food, mostly during the h months of the year the breadfruit trees do not bear mature fruit. Unit A. Fill vegetation: The vegetation apparently reflects the char- acteristics of the substratum as well as that of the fill or displaced surface material in which it is growing (pl. 2). The fill vegetation borders are obscure in many places. The fill vegetation is varied. In general, it consists of thinly spaced coconut groves, short grass, shrubs, and weed patches on the higher and dryer areas and tall slender close-growing marsh reeds or grass with scattered small patches of shrubs or small trees in the low— er or marshy areas. The following plants are found in the fill unit: Phragmites karka (pl. 31 B), Cocos nucifera, Vigna marina (pl. 31 A) Passiflora foetida, Cassia occidentalis, Scleria sp., Paspalum sp., Mbrinda citrifolia, Stachytarpheta indica, Hibiscus tiliaceus, and Muss sp. Of the above listed plants, Phragmites karka, Scleria sp., and Hibiscus tiliaceus are also found growing in the fresh-water marshes; Cocos nucifera, Passiflora foetida, Cassia occidentalis, Paspalum sp., Stachytarpheta indica, and Hibiscus tiliaceus are found in the grass- land unit; and Cocos nucifera, Vigna marina, Mbrinda citrifolia, and Hibiscus tiliaceus are also thriving in the strand vegetation unit. The coconuts and bananas have been transplanted to the fill areas; the other plants represent a phase in plant succession. Plate 2 shows a panoramic view, looking south, of the abandoned airstrip on Param. The coconuts visible in the left and center back- ground are from 5 to 8 years old. The low vegetation in the left cen- tral background is a relatively pure stand of Eigna marina (a closer view of Vigna marina growing on an area of fill on Dublon Island is ‘shown in pl. 32 A5. The shrubby vegetation in the right central back- ground is Hibiscus tiliaceus. Phragmites karka is shown in the fore- ground across the panorama. Part of the Phragmites karka is growing in fill but the strip nearest the camera is growing in marsh. In this fill area on Param concealment for foot troops is limited mostly to the 126 Plate 31 o A. Vigna marina on fill, Dublon Island. View across fill on southeast Dublon Island with Vigna in foreground and low hill covered with trees in background. December 3.951%. 7 . B. Phragmites karka on fill, Dublon Island. . Phragmites karka, a large reed 12 to 15 feet ' tell which thrives in muck and peat areas, is shown here on marshy fill on southeast Dublon Island. December 1951+. 9? A. Vigna marina and coconut trees, Dublon Island. A nearly pure stand on Vigna under young coconut trees on a fill area on southeast Dublon Island. December l95h. B. Vegetation on marshy fill, Dublon Island. View north across marshy fill; giant swamp taro in center, young banana and breadfruit trees in right foreground. l9h5-55. Plate 32 Plate 33 A. Closeup of Merremia peltata, Moen. The native name is fitau. In many places these vines form a dense growth difficult for foot troops to penetrate. February 1955- B. Grassland vegetation, Moen. Grasses in foreground are Gleichenia. Residual boulder overlying soil at right. l95h-55. Plate 3% ‘\\ A. Upland vegetation, Uman. Growth of grass and young trees at about 600 feet elevation on south central Uman. This veg- etation is moderately difficult to pene- trate and affords excellent concealment. December l95h. B. Grassland vegetation, Uman. Mostly Dimeria and ' Ischaemum muticum on the upland terrain on southern Uman. This area was recently cultivated in sweet pota- toes and has not yet become overgrown by the taller grasses. December 195%. Plate 35 Closeup of Scleria sp., Moen. This sedge has finely reflexed barbs on leaf edges. 1954-55. tall reed and Hibiscus growths. The fill area on Eten (pl. 1) is relatively dry and consequently contains only a few isolated patches of reeds. NUmerous young coconut trees are now growing on the south side and along the airstrip on the north side of the island. Ehragmites karka is the dominant plant in the fill area on south- east Dublon Island. In this area a narrow strip of Vigna marina usual- ly separates the Phragmites karka from the sea. Nearly all of the plants in this unit were less than 10 years old in 1955. Consequently, at that time there were no trees useable as lumber or for construction. In addition to the utilization of the fill areas for growing coconuts and bananas, as on Eten, Param, and Dublon Island, many of the bomb craters in the fill on northwest Mben and on southeast Dublon Island are planted to swamp taro. Unit 5. Grassland: The grassland unit is restricted to the deforested and the partially cleared upland portions of the volcanic islands. It may be considered as the primary stage of plant succession. The unit consists of a very irregularly shaped patchwork of dense tall coarse swordgrass; dense short procumbent fetinniap grass; shrubby Hibiscus and Lantana bushes; and scattered coconut, pabn, breadfruit, and mango trees. The following plants, chiefly in combinations but occasionally as pure stands, largely compose the grassland unit: Miscanthus floridulus (swordgrass), Ischaemum muticum (fetinniap grass), Paspalum conjugatum (hilo grass), Stachytarpheta indica, Passiflora foetida, Macaranga carolinensis, Iantana camara, Hibiscus tiliaceus, Sida rhombifolia, Merremia peltata, Cassia occidentalis (coffee weed), coconut, bread— fruit, and mango trees, Chloris inflata (grass), Wedelia biflora, Leucaena glauca, and Scleria sp. Most of the present grassland area was cleared during the latter years of the Japanese administration. These areas include some of the stony soils of the steep to precipitous slopes. When abandoned at the end of World War II, these areas were revegetated rapidly with Ischaemum (short grass), Gleichenia (fern) (pl. 33 B), and Merremia (vine) (pl. 33 A). Small parts of these areas have been partially reforested with coconuts and breadfruit plantings; plant succession in other localities has progressed naturally to patches of Hibiscus tiliaoeus. In other areas of the grassland, plant succession has been and probably will con- tinue to be very slow so long as these areas are burned annually by un- controlled fires set by the natives during the dry season to clean up small (usually about one-fourth acre) garden spots. In these areas the vegetation is either pure stands of either Miscanthus floridulus, which averages about 6 feet in height, or Ischaemum muticum, which averages about 15 inches in height, or a combination of the two. In areas burned several times the swordgrass appears to be encroaching on the Ischaemum, as shown in plate h B. The densely growing Ischaemum could be used satisfactorily as dun- nage. Swordgrass may also be used in cases of emergency for dunnage; however, the barbed cutting leaf-blade edges render it very unpleasant to handle. The only timber sources in this unit are the scattered co- conut, breadfruit, and mango trees. The special problems in this unit are numerous. Large patches of 127 swordgrass are difficult to cross even by foot troops. Added to the difficult penetration of this dense grass with its cutting leaf-blade edges, is the danger of falling into concealed trenches, tunnel air shafts, and gun emplacements. The possibility of falling into trenches and holes is especially great in the areas supporting a nearly pure stand of Ischaemum (pl. 3h B). The low-growing grass forms a dense sward that completely obscures the microrelief of the soil surface in many areas. The thorny shrub, lantana camara, which has become established in some small areas, is being spread by its seeds which retain their via- bility even after passing through the digestive tract of birds. This shrub, which attains a height of about 8 or 10 feet, forms fairly thick patches which can be penetrated by foot troops only with difficulty and discomfort. A sedge, Scleria sp., about 3 feet in height (pl. 35), which is usually found growing in association with Miscanthus or with Ischaemum, has leaf—blade edges that are bordered with tiny reflexed barbs. This plant will inflict severe scratches if drawn across unprotected skin. Some few small patches of the grassland are cleared and planted to such crops as sweet potatoes, watermelons, tobacco, yams, tapioca, and sugar cane. Unit 6. Coconut-breadfruit forest: This vegetative unit is the larg- est mapped on the lruk Islands. It is mapped on all the volcanic is- lands except the rock islets, Atkin and Tako. The cotonut-breadfruit forest is found on all the soils of the volcanic uplands and to a lun- ited extent on the beach sand of some of the barrier-reef islands. This unit is relatively stable, probably because the natives make some effort to encourage and maintain a fairly balanced growth of the coco- nut and breadfruit trees by replacing old nonproducing trees. The following plants are found in the coconut-breadfruit forest unit: Cocos nucifera (coconut), Artocarpus altilis (breadfruit), Mangifera indica (mango), Hibiscus tiliaceus, Pandanus tectorius, Merremia peltata, Eleusine indica (goosegrass), Sida rhombifolia, Passiflora foetida, Derris elliptica, ferns, and Flagellaria indica. The density of the coconut-breadfruit forest is various. In some areas the frequency of the coconut is greater than that of the bread- fruit; in other localities the reverse is true. Numerous areas mapped in the unit are mixtures of or transitions to the grassland unit. Where the canopy is mostly closed, as on Udot (pl. 36 B) and on northwest T01 (pls. 36 A and 57), its average height is about ho feet. In other areas, as on the steep slopes of west Mben and northeast Tol, where the unit is a mixture with grassland, the canopy height is broken; the grassland vegetation of these areas is mostly Merremia peltata (pl. 33 A - Vertical concealment for foot troops is generally good in the closed forests and fair to poor in the included grassland patches. Horizontal concealment for foot troops is good to fair in the grassland patches and is fair to poor in the forests. There is no plant material in this unit that is sufficiently ex- tensive to be used as dunnage. The breadfruit and possibly mango trees 128 \ Plate 36 A. Coconut—breadfruit forest, Tol. Foreground is northwest east Tol in background. January 1955. B. Coconut-breadfruit forest, Udot. Dense forest on the of central Udot. 195u-55. T01; north- north side Plate 37 Palm trees in Clinostigma carolinensis on Witipon mountain, Moen. A. about no feet high, are mature trees of this species. December 195%. ) background Banyan tree on Mount Uroras, Uman. B. December 1951+. , \ m can be used in construction. Coconut trees can be used satisfactorily in cribbing. Coconut logs are also excellent for use as foxhole covers and may be used in emergency as short piling. The other plants listed in the unit are practically useless for construction. Coconut fronds are used extensively by the natives for thatching their huts and copra sheds (pl. 12). Mbvement of foot troops through areas of closed forest is usually much less difficult than through the semiopen areas covered with fitau vines. The fitau vine (pl. 33 A) commonly attains a length of 20 feet or more and has a climbing growth habit similar to kudzu, Peuraria sp., in that it covers the surrounding shrubs and other vegetation. The natives are very dependent on the tree crops from this unit. The different varieties of breadfruit, the staple food of the natives, bear fruit about 8 months out of the year. During July and August the breadfruit is picked and stored in shallow holes dug in the ground and lined with banana leaves. After the holes have been filled with bread- fruit, the surface is sealed with banana leaves which are held in place with rocks. This "preserved" breadfruit smells and tastes similar to silage. Coconuts are used in the preparation of numerous native foods. Also, copra, or dried coconut meat, is the principal source of cash in- come to the natives. The coconut is a good source of water. unit 7. Ficus-Pandanus forest: The Ficus-Pandanus unit is relatively small in total area and is mapped only on the larger volcanic islands. In general it is located on the relatively inaccessible steep and pre- cipitous areas on the summits of some of the higher peaks (pl. 5 A) and to a lesser extent along the rock escarpments at intermediate levels. The vegetation of this unit has probably been altered or changed less by human influences than that of any other of the units except the man- grove. The following plants are found in various combinations and densi- ties in the Ficus-Pandanus unit: Ficus prolixa (banyan), Pandanus sp., MErremia pgltata, and occasional Clinostigma carolinensis (p1. 37 A), Flagellaria indica, Gleichenia, Eleocarpus, and Hibiscus. The height of the canopy in this unit is varied but averages about ho feet. The Ficus-Pandanus forests contain some small, fairly open areas which are covered mostly with fitau vines with interspersed iso- lated pahns. Other portions of the unit are generally dense forests of banyan and probably Eleocarpus and commonly have closed canopies. Ver- tical concealment for foot troops in this unit is probably excellent to good in the dense forests; horizontal concealment is good to fair. Cross-country movement by foot troops in this unit would be diffi- cult and slow. In addition to the difficulty experienced in crawling and wading through the semiopen areas of fitau vines, which grow along the ground and over shrubs 10 to 20 feet high, foot troops would also have to contend with the usually dense undergrowth of Flagellaria indica vines and the numerous aerial roots of the banyan tree, as shown in pl. 37 B- Very little material from this unit can be used for construction. The Eleocarpus tree should be comparable to Quercus alba (North American white oak; for construction material; however, it is not sufficiently 129 extensive to be significant. The palm logs would be suitable for the same construction as the coconut logs described in Units 2 and 6; how- ever, the palm is too rare to be of value as a construction material. There is no material in this unit suitable for dunnage. The fitau vine may possibly serve as cushioning material in emergencies. No important food plants occur in this unit. 130 TACTICAL ASPECTS OF TERRAIN Avenues of Approach by Richard L. Hay General statement The Truk Islands are 636 miles from Guam (Mariana Islands), 3,029 miles from Hawaii, and about 1,000 miles from Wake, KWajalein (Marshall Islands), and Peleliu (Palau Islands). The Truk barrier reef is about 125 miles long and ranges from a few hundred yards to nearly'a mile in width. The reef is breached by 18 passes between 15 and 25 fathoms deep. Depths within the lagoon are from 20 to ho fathoms but numerous coral reefs, wrecks, and islands are navigational hazards. While most islands have sand beaches, they are generally not suitable for landing sites because of wide fringing reefs impassable to ICMktype craft. 0n Moen, Eten, and Dublon Island made land extending into the lagoon pro- vides landing sites suitable for all types of landing craft. Only two piers are usable by ocean-going ships, one on Moen and one on Dublon Island, but there are numerous piers suitable for barges, large landing craft, and small boats. Exit from landing sites on the made land is generally good and vehicular traffic could move with little difficulty on the beaches and on the fill. The old Japanese-built roads need im- provement before use. Exit from the lowlands is severely restricted by steep slopes, dense trees, and rough land; roads are generally lacking in the uplands. Exit from barrier-reef-island beaches is hampered by steep beach gradients, scarps, and rubble ramparts. The Truk Islands are poorly suited for airborne operations because of rugged forested uplands and poorly drained lowlands. Mben Airfield is the only immediately usable assault-aircraft landing site; there a- bandoned airfields need minor repairs. Airfields and made land provide sites for small airdrops and helicopter landings but trees and small marshy areas are hazards. The narrow sandy beaches have scattered small sites for helicopter landings. Gently sloping grassy uplands provide some sites for airdrops and helicopter landings; exit from up- land areas is generally poor. Forested uplands and swamps and marshes of the lowlands are unsuitable for all airborne operations. The great- est elevation in the Truk Islands is l,h53-foot Mount Thmuital on Tbl and six islands have peak elevations over 750 feet. Some areas have restricted approaches. Amphibious operation conditions Approaches and anchorages: The coral islets on the barrier reef can be directly approached from the ocean, but ships must enter through one of the passes in the barrier reef in order to approach the lagoon islands. The following information concerning passes and anchorages is taken from pages 27h-283 of Sai Directions for the Pacific Islands (U. S. Navy Department, Hydrographic Office, 19 5 . The most important passes reading clockwise from the north are North, Northeast, Salat, Otta, and Piaanu. Northeast Pass is the recommended entrance to the lagoon. Tidal currents in the passes commonly reach velocities of 2 knots; it is reported that northeasterly winds send a heavy swell through Nbrth- east Pass and the current may reach 5 knots. Truk Lagoon is said to have the best anchorage in the Caroline Is- lands; it is suitable for battleships (20 to ho fathoms) except for l3l widely distributed shoals and reefs and, in the vicinity of Dublon Is- land, a number of sunken ships. The anchorage most used by the Japa- nese warships is located northwest of Dublon Island; the larger vessels berthed close to the island and smaller vessels westward between Fefan and Moen. Eten Anchorage, off the southeast side of Dublon Island, was used by the majority of Japanese merchant vessels. Other anchorages include the areas off the west and southwest coasts of Mean. Vessels may also find temporary anchorage Just inside the barrier reef near North Pass and Minami-suid5. Nearshore approach to all of the Truk Islands is endangered by fringing coral reefs. least depths over the fringing reefs average 2.5 feet at mean sea level, but coral blocks and niggerheads project above sea level in many places. The maximum tidal range is approximately 3 feet. Diurnal and semidiurnal tides are about equally common. Landing sites: The Truk Islands are characterized by few landing sites, using criteria based upon World War II landing craft. Sand beaches are found on most of the islands, but wide fringing reefs endanger approach to most of the beaches. Mangrove swamps bordering large areas of the larger islands further increase the difficulty of landings. The only sites suitable for all types of landing craft are areas of reclaimed land built out into the lagoon. A field reconnaissance of possible landing sites on Truk was made shortly after the surrender of the Japa- nese on 2 September l9h5. This data, given in Field Survey of Japanese Defenses on Truk (U. S. Navy Department, CINCPAC-CINCPOA, l9h6), is de- tailed and generally reliable. Possible landing sites were approached in a Japanese Daihatsu (large landing craft about the same size as an ICM) which has a draft of approximately 1 foot foreward and 2.5 feet aft. Normally the Daihatsu grounded on the fringing reefs. Fifteen of the best landing sites were studied in detail for the CINCPAC-CINCPOA report; the length, composition, and approach suitability from that re- port are listed here followed by any corrections and changes which have occurred since. The location of these beaches is shown on maps 23 through 29. Mean sea level is the datum in the discussions on landings sites, docks, and piers. Beach 1: northwest side of Dublon Island; 300 feet long; loose rock seawall fronting flat reclaimed land; can be used by all but pos- sibly the largest landing craft. Seaward 15 feet of reclaimed land behind seawall has been washed out, leaving this strip littered with blocks of basalt and andesite a foot in diameter. Reclaimed land is covered by a relatively dense growth of vines and small trees (pl. 38 A). Beach 2: south side of embayment on the east side of Dublon Is- land; 300 feet long; rock seawall fronting low earth fill; can be used by all types of landing craft. Some of earth fill has been washed; the remainder is wet and soft underfoot (pl. 38 B). Exit causeway is partly obstructed by coconut pabns. Beach 3: south side Dublon Island; hOO feet long; concrete and stone seawall fronts reclaimed land; 95-foot-wide boat ramp; all types of landing craft (pl. 39 A). Configuration of beach as shown in Air Photo 3, p. 130, CINCPAC- CINCPOA report is now considerably modified. Boat ramp is now partly obstructed by Japanese craft (pl. 39 B). 132 A. Beach 1, Dublon Island. Looking northeast from the southwest end of Beach 1. Seawall fronts filled land which is densely covered with grass, brush, and young trees. Near mean sea level. March 1955. B. Beach 2, Dublon Island. Looking west along the western 200 to 250 feet of Beach 2 on the south side of Nemonon bay. Seawall is locally breached and earth fill is washed out. Depths on seaward edge of seawall are generally about 5 feet. About mean sea level. Febru- ary 1955- Plate 38 Plate 39 A. Western part of Beach 3, Dublon Island. View looking west along the western 250 feet of Beach 3. Arm of crane at right is one of several obstacles to beach exit. Depths on seaward side of seawall average about A feet. About mean sea level. February 1955. B. Eastern part of Beach 3, Dublon Island. Looking northwest from coral jetty at the east end of Beach 3 to boat ramps forming the eastern 120 feet of the beach. Rusted Japanese craft obstructs one of the four boatways in this section. About mean sea level. February 1955. Plate 1+0 Beach 7, Moen. Looking north near the center of Beach 7. The beach consists largely of fine- to medium-grained calcareous sand having excellent trafficability. Near high tide. November 1951+. A. Beach 8, Moen. Looking east from the west end of Beach 8 on southwest Moen. Earth fill has been washed out in foreground and reclaimed land is locally flooded. Seawall in background is breached in two places. Near mean sea level. March 1955. B. Northeastern part of Beach 9, Moen. .Looking north- east from the southwest end of Beach 9. The beach con- sists largely of gravel and cobbles of volcanic rock. The foreshore gradient is about l:h5 a narrow berm is visible at right. High tide. March 1955. Plate #1 A. Southwestern part of Beach 9, Moen. looking south- west along the southwest 200 feet of Beach 9. Blocks of rock visible along the shoreline are exposed chiefly during low tide. (Compare this photo with plate #1 B taken at high tide.) Beach at left consists of round- ed to angular andesite and basalt detritus of pebble and cobbles size. Low tide. March 1955. B. Beach 10, Moen. Looking southeast along the south- east 250 feet of Beach 10. The beach consists of cobbles and blocks of rock from several inches to a half foot in diameter. The overall beach gradient is about 1:10; trafficability of the beach is good. Low tide. March 1955- Plate #2 Q Beach h: south side Dublon Island; 1,200 feet long; rock seawall fronting reclaimed land except for two lOO-foot-wide seaplane ramps leading inland to concrete-surfaced area; suitable for all types of landing craft. West end of seawall breached, and earth has been washed out behind seawall for 300 feet to east of breached area; this washed area is flooded. Beach 5: northwest side Eten; #00 feet long; rock seawall fronts reclaimed land of airstrip; all types of landing craft. No changes noted. Beach 6: northwest side of Eten along southwest section of air- strip; l,050 feet long; rock seawall fronts reclaimed land of airstrip; all types of landing craft. No changes but one discrepancy in data is noted: length listed, 1,050 feet long, does not agree with length of l,h50 feet shown on Air Photo 5, p. 131, CINCPAC-CINCPOA report. Beach 7: southwest corner of Mben, facing west; 500 feet long; sand beach fronts reclaimed land of airfield; suitable for small craft (pl. ho). No changes; however, a discrepancy in data is noted: length list- ed is 500 feet; length shown on Air Photo 6, p. 132, CINCPAC-CINCPOA report is 1,000 feet. Beach 8:. southwest corner of Moen, facing south; 650 feet long; rock seawall fronts reclaimed land except for seaplane ramp fronting concrete-surfaced area; suitable for all types of landing craft. Seaward margin of the reclaimed land has settled as much as a foot, and the seawall is breached at these low areas. Earth fill has been washed out behind the seawall where breached (pl. #1 A). Where in the intertidal zone the reclaimed land is soft underfoot. Beach 9: northwest side of Moen at southwest end of Moen Airfield; 600 feet long; rock and earth fill; part of beach can be used by all types of landing craft. Seaward portion of earth fill is washed out, and blocks of rock 1 to 2 feet in diameter litter the shoreline and extend as much as 50 feet offshore. Most blocks are exposed only at low tide (pls. #1 B and #2 A). Pebbles and cobbles of basalt or andesite form the beach at the east end of Beach 9 (pl. #1 B). Beach 10: southwest end of Moen Airfield, facing southwest; 500 feet long; beach of cobbles and angular blocks fronting earth fill of airfield; suitable to all types of landing craft (pl. #2 B). Some change in coastal configuration has occurred, bUt essential information is correct. Beach 10 adjoins Beach 9, and the two could be used as a single beach. Beach 11: north end of uman along its western face; 1,000 feet long; sand beach 20 feet wide fronts narrow sandy strip; can be used by small craft at high tide. Many beaches throughout the Truk Islands can be approached with care by small craft, as was recently demonstrated by a lightly loaded LCM, used for salvage operations, which could pass over the reef at high tide in many places; hence there seems to be little reason for em- phasizing this beach area in particular. 133 Beach 12: north side of Fala-beguets near western end; two 300- foot beaches separated by 200 feet of shoal mangrove swamp; sand beach fronting flat low grassy area; suitable for small craft only. No changes noted. Beach 13: northwest side of Ulalu; 300 feet long; sand beach fronting wooded terrain; suitable for small craft unloading personnel. Approach over coral reef endangered by coral heads, and craft will like- ly be grounded on shallow portion of reef. Comment to Beach 11 applicable here. Beach 1h: southwest corner of Ulalu facing northwest; 250 feet long; sand beach fronting wooded sandy terrain; suitable to all types of landing craft. The only section of beach suitable to larger landing craft is on the southwest extremity of the island facing southwest; usable beach is approximately 50 feet long, and is approached through a gap in the fringing reef. Beach 15: (unnumbered in CINCPAC-CINCPOA report) southwest tip of Polle peninsula, facing south; 1,800 feet long; sand beach 25 feet wide fronting sandy terrain; eastern part of beach suitable for an LST. No change noted. Field study was made on beaches throughout the Truk Islands, both on the lagoon and barrier-reef islands. Although fringing reefs render most of the beaches unsuitable for landing craft of the type used in World War II, beach data will be given here for other possible use. Beaches are found only locally on the volcanic islands in the la- goon. Most of these beaches consist of fine to coarse coral sand. The beaches generally range from less than 10 feet to about 30 feet in width at low tide; at high tide many of the beaches are obliterated. On most beaches, the foreshore gradient is about 1:10; a well—defined backshore is generaILy absent. Mbst of the sand beaches are relatively firm and can be traversed by a jeep with little difficulty. The sea- ward margin of the reclaimed land on which Mben Airfield is built has been worked by the waves to form a beach (Beaches 9 and 10) consisting of andesite and basalt pebbles and cobbles (pls. #1 B and #2). The beach is 15 to 25 feet wide at low tide and has a. foreshore gradient y of l:h to 1:10; a berm is locally present (pl. #1 B). The coral islands in the lagoon are almost everywhere fringed by sand beaches rather similar to those on the volcanic islands. Commonly, however, the beaches on the coral islands are somewhat wider than those on the volcanic islands. Mbst of the beaches on the coral islands in the lagoon could probably be traversed by a Jeep. Most of the coral islands on the barrier reef are encircled by beaches in which coarse debris is abundant. In general, beaches on the ocean side of the reef islands are largely coarse coral debris: gravel, cobbles, and coarser coral rubble (pl. 18). Blocks of coral as much as 5 feet in diameter lie scattered along many sections of beach. Sand is, however, commonly intermixed with the coarser debris, particularly on the foreshore, and there are local stretches of sand beach on the ocean side of some reef islands (pls. 16 B and 17 A). On some beaches a hard 17 In this chapter, gradient is expressed as ratio of vertical to horizontal. 13h pavement of cemented coral sand and coarser detritus floors local areas on the lower part of the foreshore (pl. 20). The ocean-facing beaches are generally 15 to 30 feet wide at low tide; at high tide most are 10 to 20 feet wide. Beaches of coarse debris generally have foreshore gradients of 1:3 to 1:5 and equally steep-faced backshore berms. The foreshore gradient of the sand beaches is estimated to be 1:10 to 1:15; backshore gradients are gentler. The coarser ocean-facing beaches gen- erally merge inland with ridges (also termed ramparts) of coral rubble having maximum elevations between h and 8 feet at high tide. locally, a scarp 3 to 5 feet high separates the ocean-facing cobble beaches from the island interior. Trafficability of most ocean—facing beaches is poor due to the steep gradient, large blocks of coral, and rubble ram- parts. On the lagoon side of the barrier-reef islands both sand and cob- ble beaches are common, but sand beaches generally predominate. The sand beaches are generally 10 to 30 feet wide at low tide; at high tide most beaches are 5 to 10 feet wide and many stretches of beach are un- der water. Foreshore gradients of the sand beaches are generally be- tween 1:6 and 1:10; where present the backshore is generally flatter. Most of the sand beaches could be traversed by Jeep. The cobbles on the lagoonal beaches are generalLy small, and gravel is locally common. The foreshore gradient of lagoonal cobble beaches is steep (1:3 to 1:8), and steep-faced berms are commonly present on the backshore. Traffic- ability of the lagoon-facing cobble beaches is generally poor. Both sand and cobble lagoonal beaches are commonly separated from the island interior by a scarp l to 2 feet high. living coral reef and reef limestone form a continuous fringe a- round the barrier-reef islands and are the major hazard to nearshore approach on both lagoonal and ocean-facing sides. Water over the reef is generally about 3 feet deep at high tide and numerous niggerheads and larger eroded remnants of reef limestone extend nearer the surface; some niggerheads project above sea level at high tide. At low tide the water over the reef is commonly several inches to a foot deep, and nu- merous projections of reef limestone are exposed above sea level. Width of the reef fringing the barrier-reef islands on the ocean side bears a rather close relationship to the prevailing winds from the northeast. The outer fringing reef is broader on the northeast side of the lagoon than elsewhere. 0n windward islands the shallow part of sea- ward fringing reefs is generally 100 to 300 yards wide; elsewhere the seaward reefs are 50 to 100 yards wide. Reef fringing the lagoonal faces is generally 50 to 100 yards wide. Beach exits: Exit from the most suitable landing sites on the larger volcanic islands is afforded by concrete ramps and reclaimed land, both of which adjoin main coastal roads. The concrete ramps would afford exit to all types of vehicles. Trafficability of the reclaimed land backing larger sections of the best landing sites varies according to the extent of saturation by sea Water. Where low, the seaward edge of the reclaimed land is wet and soft underfoot; trafficability is proba- bly fair to poor. Where a foot or more above high water, the reclaimed land is drier, and trafficability is commonly excellent to fair and movement conditions depend chiefly on the density of vegetation. Roads, some now overgrown with grass and other vegetation, lead inland and along the coast from the larger piers and areas of reclaimed land. Exit from the sand beaches on both the volcanic islands and the coral islands in the lagoon would be more difficult as prepared exits 135 are generally lacking. Many of the sand beaches merge inland with ele- vated beach deposits generally planted in coconut trees. Some sand beaches are separated from the elevated beach deposits by a scarp l to 2 feet high. Tracked vehicles and jeeps and trucks could probably move inland from most of the sand beaches without improvements other than the leveling of the sand scarp and clearing of coconut trees. Exit from the beaches on the barrier-reef islands is generally poor because of steep beach gradients, rubble ramparts, scarps, and rel- atively dense vegetation (pl. 9 A). Sand beaches and spits would af- ford the best exits. Roads exist on few of the barrier-reef islands and the dense vegetation, areas of coarse rubble, and swamps are gener- ally impassable to wheeled vehicles. Piers and docks: Although Truk was a major Japanese naval base through- out most of World War II, the naval shore installations were never ex- tensive, and there were no piers for use by either warships or merchant vessels. The Japanese built piers for barges and lighters which fer— ried men and supplies to ships anchored offshore. Reportedly ships as large as a cruiser were able to take oil from a fuel-oil pier on Dublon Island. A floating drydock capable of accommodating a destroyer is now off the west side of Dublon Island - sunken, rusted, and unusable. Detailed descriptions of the piers as they existed at the end of hos- tilities may be found in Field Survey of Japanese Defenses on Truk (U. S. Navy Department, CINCPAC-CINCPOA, l9#6) and this data will not be repeated. Current (1955) condition of piers is summarized. The pier currently used by merchant ships is located on the west side of Moen. It is 700 feet long and so to 60 feet wide except the seaward end which is approximately 175 feet wide. Vessels of class AKL can dock at the seaward end of the pier, but AK class and larger vessels anchor offshore several hundred yards. The pier is used by trucks and other vehicles (pl. #3). The fuel-oil pier on Dublon Island, 1,120 feet long and generally 20 to 25 feet wide, is still intact but overgrown with vegetation, and trees would have to be cut in order to permit use by vehicles (pl. ## A). The seaward end of the pier is partly obstructed by a sunken barge which was being raised for salvage in June 1955 (pls. ## B and #5 A). Most of the piers built for use by barges lie on the south coast of Dublon Island. These range from approximately 50 to 1,000 feet long and 15 to 150 feet wide. Several of the concrete piers are capable of bearing vehicles (pls. #5 B and #6 A). Other piers, both concrete and piled rock, have been partly washed out by waves, and would have to be repaired to allow use by vehicles (pl. #6 B). The crane located at the end of one concrete pier (pl. #6 A) is rusted and unusable, as is a 30- ton floating crane near the southwest corner of Mben. Several well- constructed piers built by the Japanese on Uman, Fefan, and Ulalu are still usable (pl. #7). ‘ A number of piers used by small Trukese boats are found on all of the larger volcanic islands; most of the smaller islands and several of the larger reef islands have one or more small piers. These boat piers are generally between 100 and 300 feet long and between 6 and 8 feet wide; a few are larger (pl. #8). Most of these piers consist of piled blocks of coral and compact lava - basalt and andesite - thinly surfaced with coral sand (pl. #9). Many piers are entirely unsurfaced. Most of these piers are not capable of bearing wheeled vehicles, due principally 136 O Plate #3 A. American pier, west Mben. Looking seaward along the outer 150 feet of the TOO-foot-long pier. Vessels of AKL class can dock at the seaward end. 1954-55. B. American pier, west Moen. Looking inland along the . pier. Width usable by vehicles is 25 to 30 feet. l95k-55. Plate #4 A. Fuel-oil pier, south Dublon Island. Looking inland midway along the pier. Pier would be trafficable if trees and brush were cut on inland part. December 195h. B. Fuel-oil pier, south Dublon Island. Looking seaward along the l,l20-foot-long pier. Pier is generally 20 to 25 feet wide except where narrowed by local breaches such as shown at left. About 100 feet from the outer end. December 1954. Plate #5 A. Fuel-oil pier, south Dublon Island. Looking north- east along the seaward edge of concrete platform at end of fuel-oil pier. Sunken barge in background is an ob- stacle to use of the pier, at which 7,000-ton tankers reportedly docked. December l95h. a B. Pier at former naval base, Dublon Island. looking southwest along the seaward edge of Japanese concrete pier having railway tracks. Pier in background is the only Japanese pier with a crane. December l95h. Plate 1+6 A. Pier, south Dublon Island. looking inland along ECO—foot concrete pier. Photo taken beneath crane mount- ed on seaward end (see plate 1+5 B). February 1955. B. Pier, south Dublon Island. Looking inland along l,OOO-foot pier. Formerly 25 feet wide, the pier is here washed to a width of about 6 feet. December 1951+. Plate #7 A. Pier, Ulalu. Looking seaward along 300-foot pier at southeast end on Ulalu. Pier is 15 feet wide and composed of coral and basalt blocks surfaced with li- monitic concretions. l95h-55. B. Pier, Ulalu. Looking inland at pier in photo above. 1954-55. Rhmelfl , . L' ‘ '1‘ . to 9 A‘ "K, v ' E’W ‘ a \ \ V ;' ',~~i, I‘ ‘\\“\ w NW own-vat w wwwx»m, pawn“- _ p a» ' A. Pier, east Uman. Looking seaward along the major pier on the east side on Uman. Pier is about 550 feet long and is usable only by small boats. December l95h. B. Seaward end of pier, east Uman. Looking east along seaward extremity of pier in above photo. The pier is constructed of piled blocks of coral and volcanic rocks. December 1954. Pier, west Param. Looking seaward from the foot of a small—boat pier 150 feet long on the west side of Param. Pier consists of piled coral blocks surfaced with calcareous sand and is typ- ical of the small Trukese piers. December l95h. Plate #9 Plate 50 A. Netutu channel, Tol. Looking northwest along channel separating northeast Tol from southeast Tol. At left is Japanese path, A to 6 feet wide, built above the level of the channel and adjacent marshland. Path is surfaced with peat. 1954-55. B. Netutu channel, Tol. Looking west along a part of the channel cut through fine—grained basalt. Canal is 18 to 20 feet wide here; bedrock walls are as much as 10 feet high. Depth of water is locally only 1 to 2 feet at low tide. 195u_55. to their loose construction and narrow width. Depth at the seaward end of the small piers is generally 3 to 6 feet at mean sea level. Canals: A single canal has been built in the Truk Islands. This canal lNetutu channel), about half a mile long, enables small boats to go from Tel Harbor to Lemotol Bay (pl. 50). A 350-foot section cut through bedrock is both the narrowest and shallowest part of the canal; the minimum width is 18 feet, and least depths at low tide are about a foot. Airborne operation conditions General terrain characteristics: Conditions for airborne operations are generally poor throughout the Truk Islands. The small size and steep hillsides of the volcanic islands, together with swamps and for- ests, render nearly all of the area unsuitable for large-scale airdrops. Three Japanese World War II airfields, now in disrepair, and Mben Air- field, a former Japanese airfield, are the only sites suitable for the landing of assault aircraft. Sites suitable for helicopter landings are, however, found on all of the larger and several of the smaller is- lands. Upland terrain on the largest islands is rugged (pls. h A, 5 A, and 51 A). Most of the island area has slopes steeper than 30 percent, many slopes are steeper than 60 percent, and vertical scarps are common. Peaks higher than 750 feet (229 meters) are found on six of the volcan- ic islands. Gentle slopes, those less than 30 percent as here consid- ered, and flat land form local areas on the upland portions of most of the volcanic islands (pls. 3, h B, 6 B, and 15). Many flat or gently sloping areas are more than a mile long but few average as much as a quarter of a mile wide (maps 23 through 29). On upland terrain World War II Japanese trenches, concealed by recent vegetation, are a hazard to airborne operations. Flat terrain forms a discontinuous coastal lowland fringing much of the upland area. Where present, the coastal lowland ranges from less than 100 feet to half a mile_in width; more generally, the fring- ing lowland is 300 to 1,500 feet wide. The largest area of coastal lowland forms the western margin of Moen; it is approximately h miles long and from #50 feet to half a mile wide. All other areas of coastal lowland are much smaller. The upland soil is largely clay in which rock debris is widely in- termixed. Blocks of volcanic rock several feet in diameter lie on and partly in the soil in many places (pl. 55 B), and boulder fields are locally developed (pl. 1h). The soil is well drained, and most of it is firm. Bedrock is locally exposed at the surface (pls. 6 A, 16 A, 51 B, and 55 A). Soils of the lowland areas are diverse. A belt of sandy terrain, from less than 100 feet to 600 or more feet wide, partly fringes all islands. Mangrove swamp is also common at the periphery of many of the volcanic islands. Many swamps uncover during low tide, but in others a foot of water may remain. Where protected from wave action, the man- grove swamp contains principally muck and peat; where exposed to surf, sand is intermixed with the muck and peat and locally predominates. Where consisting largely of muck and peat, the mangrove swamp is very soft underfoot, and a man would sink waist deep; where sandy, the man- 137 grove swamp is firmer. Fresh-water marshes are also widely distributed. The fresh-water-marsh deposits consist largely of muck and peat, in which a man would sink to depths of from several inches to several feet. Filled land, reclaimed by the Japanese, also forms areas of coastal low- land on Mben, Dublon Island, Eten, and Param. On Dublon Island, re- claimed land forms an almost continuous fringe ranging in width from 300 feet to 1,500 feet. On Moen, Param, and Eten the reclaimed land is between h,000 and 6,000 feet long and between 300 and 1,200 feet wide. The fill consists of earth and crushed rock excavated mostly from nearby hillsides. The surface of the reclaimed land is flat or very nearly so; elevation of filled areas is generally between 1 and 5 feet above mean sea level. The fill is firm underfoot except where local areas have subsided a foot or more and are flooded during high tide. The air- fields built by the Japanese on the fill on Mben, Eten, and Param were surfaced with concrete, except for Mben Airfield which was surfaced with crushed rock. A number of smaller areas on Moen and Dublon Island were surfaced with concrete to form boat ramps, seaplane taxiways, or installation areas (pl. 52 A). O Dense tropical vegetation covers nearly all of the land area. An estimated three-fourths to nine-tenths of the upland area is to some (flfix degree forested (pls. 5 A, 36 B, and 57). Density of the forest cover varies from sparse to dense. Where forest cover is moderate to dense, the undergrowth, largely vines, grass, and small trees, is commonly rather open. Where the forest cover is sparse or absent, a dense growth of grass predominates (pl. h B). The grass covering many upland areas is from 6 to 8 feet high (pl. 56 B). Commonly, however, the grass is a shorter variety forming a dense growth 2 to h feet high (pl. 35). Vegetation on the coastal lowland differs markedly from that on the upland terrain. Coconut trees, generally planted between 20 feet and 50 feet apart, cover most of the sandy lowland areas (pls. 7 B and 11 A). Mbderate to dense undergrowth on sandy terrain is chiefly re- stricted to the coral islands, both in the lagoon and on the barrier reef (pl. 9 A). Mangrove trees from 5 to 25 feet high form most of the vegetation of the mangrove swamps (pls. 7 A, 10 A, 28, and 29). The growth of mangrove trees is generally dense, but locally the mangrove cover is sparse or moderate. Many fresh-water marshes are planted in taro, a broad-leaved plant 5 or 8 feet high (pl. 30); elsewhere, the marsh vegetation is grass 8 or 10 feet high (pl. 53 B). Vegetation on the fill areas is varied. Grass, brush, vines, and coconut trees, either singly or in combination, cover most of the reclaimed land (pls. l 38 A and 52 B). The vegetation on the reclaimed land is rather dense ‘{ \ in some areas (pls. 31 B and 32 B), but more generally it is open enough to allow unrestricted walking, and several areas are open enough to permit cross-country vehicular movement (pls. 31 A, 32 A, and 53 A). The terrain of the larger islands is rugged, and air currents would affect airborne operations during windy periods. Particularly dangerous would be down-drafts on the lee sides of the larger islands. For further information about Truk weather see the chapter on climate. Parachute-drop operations: The primary terrain considerations for par- achute drops of men and materiel are a sufficiently large area of gently sloping or flat land on which vegetation does not interfere with the parachute landings or conceal dropped equipment, and soil conditions which will permit assembly and movement of ground troops and recovery of materiel. Another important factor is a clear approach at eleva- tions of 1,000 or 1,200 feet. 138 A. Uitonap mountain, Udot. Plate 51 Looking northwest at the highest hill on Udot, elevation 242 meters (794 feet). l95h-55. B. crest of the central hill of Udot. l95H-55. Exposed bedrock, Udot. Exposure of lava bedrock on the ridge— A. Concrete-surfaced seaplane taxiway, south Dublon Island. December 195%. B. Marshy fill, southeast Dublon Island. Cultiva- ted area of giant swamp taro in foreground; growth of Phragmites karka in right background. 195h—55. Plate 52 A. Former airfield, Param. View looking northeast showing short grass and young coconut trees. Upland terrain in background. December l95h. B. former airfield, Param. 1954-55. Dense Phragmites karka on marsh adjacent to Plate 53 r___r Using a minimum drop-zone area of #00 by 800 yards (approximately one-eighth of the area required for airdropping a battalion), few areas suitably flat or gently sloping exist in the Truk Islands. Of the suitably flat or gently sloping upland terrain, several sites approxi- mate the minimum area - on Tel (maps 23 and 2h), Ulalu (map 25), Fefan (map 29), and Fala-beguets (map 26). All of these sites are locally forested, and concealed World War II trenches are an additional hazard to personnel drops. The sites on Tel, Fefan, and Fala-beguets have scattered boulders and blocks of rock several feet in diameter at the surface. Prepared exits from the sites on T01, Fefan, and Fala-beguets are lacking, but a road, 8 or 10 feet wide, leads east to the coast from the upland surface on Ulalu (pl. 58 B). Mangrove swamps and most of the coastal lowlands are unsatisfacto- ry for parachute drops. Both fresh—water marshes and salt-water swamps are unsuitable as drop zones because of the soft, mucky bottom and gen- erally dense vegetation. 0n the larger islands the strips of sandy terrain, which are rarely wider than 200 yards, are too narrow for large-scale drops. Parachute drops on the sandy terrain would also be endangered by coconut trees and scattered houses (pl. ll A). The larger coral islands in the lagoon and on the barrier reef are densely forested with coconut trees (pl. 9 A). The most suitable site for a parachute drop on the reef islands is a proposed airfield area largely cleared of coconut trees on Mesegon, on the southern part of the barri- er reef. This cleared area is approximately 3,300 feet long and 300 feet wide. Scattered trees 15 feet high and coral blocks 2 feet in diameter would endanger airdrops and assembly of materiel. Much more suitable for parachute drops is reclaimed land, which is firm, flat, and sparsely vegetated over relatively large areas (pl. 1). Reclaimed land fringes much of Dublon Island; it is locally swampy and covered with dense grass and other vegetation (pls. 31 B, 32 B, and 52 B). More suitable for airdrops are Mben Airfield and the abandoned air- fields on Eten, Param, and southwest Moen, brief descriptions of which are given in the chapter on Roads and Airfields. Meen Airfield has a total length suitable for parachute drops of about 5,h00 feet and a width of from 550 to 1,000 feet. The reclaimed land forming the air- field on Eten is about h,500 feet long and 600 feet wide. Scattered coconut trees and houses are obstacles to parachute drops on Eten (pl. 1). The airfield area on Param is approximately 5,700 feet long and from 300 to #50 feet wide; scattered coconut trees, particularly at the ends of the airfield, would endanger parachute drops to some extent (pls. 2 and 63 A). The old airfield on the southwest corner of Mben has a length of approximately h,000 feet suitable for parachute drops, but the width is only 200 to 300 feet for half of this length. The main coastal roads on Mben, Dublon Island, and Param, pass through or adjoin the reclaimed land on these islands. The airfield on Eten con- stitutes most of the flat land of this island. Aircraft in formation normally drop troops from altitudes between 1,000 and 1,200 feet. As few peaks in the Truk Islands exceed a thou- sand feet in elevation, few drop-zone approaches are endangered by high ground. Assault aircraft operations: The airfield runways on Mben, Eten, and Param (described in the Roads and Airfields section) are the only areas which would be suitable, after a small amount of preparation, for the landing of assault aircraft. Much more preparation would be necessary to construct suitable landing sites on any other areas, either upland or lowland, lagoon, or barrier reef. The runway of Mben Airfield 139 (3,h00 feet long) is usable at the present time. The abandoned runways on southwest Moen (3,300 feet long), Param (1+,ooo feet long), and Eten (3,300 feet long), are surfaced with concrete, but the concrete has cracked, and minor repairs would be necessary before planes could land. (fi‘. local areas on the airfields of southwest Moen and Param have subsided / as much as a foot, and are flooded to depths of several inches at high tide. Few coconut trees would have to be cleared from the airfields on Eten (pl. 1) and southwest Moen, but a rather large number would have to be cleared from the airfield on Param before planes could land (pl. 2). Grass and brush widely cover these airfields on Moen, Eten, and Param. Construction of another airstrip was begun by the Japanese on Mesegon, on the southern part of the barrier reef; the coarse coral rubble was never leveled or surfaced, and some trees and brush were never cleared; hence, considerable preparation of this area would be necessary before assault aircraft could land. Helicopter operations: Much of the upland terrain of the Truk Islands has moderate to steep slopes (more than 30 percent) and is forested to some degree (maps 23 through 29). Most of the soil on the steeper up- land slopes is stony, and blocks of volcanic rock several feet in die- meter commonly lie on and partly in the soil, locally resulting in ‘—‘ boulder fields. Such terrain would be largely unsuited to helicopter landings. Uhforested areas on the moderate and steep slopes should lo- cally permit hovering, but air currents caused by the rugged topography would probably increase the difficulties of hovering. Particularly dangerous would be down-drafts on the lee sides of the larger islands. (See the Climate section for more on wind conditions in the Truk Is- lands.) There are a number of gently sloping (less than 30 percent) upland areas which would be suitable for helicopter landings. Most of these gentle upland surfaces are benches or terraces on the sides of the larger hills (pls. 6 B and 55 B), but some are small plateaus or mesas on the tops of hills (pls. h B and 15). Clumps of woods and scattered coconut trees are common (pl. 55 B), but most of the areas are covered with a dense growth of grass (pls. 35 and 56 B), and some plots are cultivated as gardens. The grass itself would probably not prohibit helicopter landings, but it would conceal obstacles to landings, such as trenches and boulders. Hovering would be possible over all but the forested portions of the gently sloping areas, and air currents would probably be less of a hazard on the gentle slopes and hilltops than on the steeper slopes. ( Most of the lowland terrain on the islands in the lagoon is either swampy or thickly covered with coconut trees, and helicopter landings generally would be dangerous. Hovering would be endangered by trees over most of the lowland terrain except for the fresh-water marshes and reclaimed land. The military value of hovering over marshes is probab- ly limited. Meet suitable for both landing and nonlanding operations are the airfields on Moen, Eten, and Param. Helicopters could probably land on these areas and on much of the reclaimed land fringing Dublon Island without preparation. Helicopter operations of any sort would be difficult on most of the coral islands on the barrier reef because of the dense growth of coconut trees (pl. 9 A). Sand spits would probably afford small hovering and landing sites on a number of the islands (pl. 17 B). On Mesegon, in the southern part of the barrier reef, coconut trees were cleared for a proposed airstrip 3,200 feet long and 300 feet wide. Small areas of this site would probably be suitable for both landing and hovering. ( lhO Netutu channel, T01. Mangrove bordering channel. Plate 51+ 195h-55. Discussion of units: All terrain of the volcanic islands is classified in maps 23 through 29 as to suitability for parachute-drop, assault air- craft, and helicopter operations. Primary factors considered were topo- graphy, vegetation, and soil. The size of areas was not considered in determining suitability for parachute-drop and helicopter operations, as the required area depends upon the scale of operation and type of aircraft. Unit A1 consists of airfield runways. The runway of Moen Airfield is surfaced with crushed coral and could be used for landing assault aircraft, for parachute drops, and for helicopter landings. Runways on Eten, Param, and southwest Moen are surfaced with concrete, but repairs would be necessary and coconut trees would have to be cleared before assault aircraft could land (pls. l, 2, 53 A, and 63 A). Parachute drops would be endangered by trees to some extent. Helicopters could land safely in many places. Unit A2 consists of filled land which is flat and generally firm and dry, an exception being local marshy areas on Dublon Island. Grass, vines, young coconut trees, and brush are widespread, both singly and in combination (pls. 31, 32 A, and 38 A). Taro grows in several marshy areas on Dublon Island (pls. 32 B and 52 B). Uhfilled bomb craters, many of which contain standing water, are locally common. This terrain is unsuitable for the landing of assault aircraft. Suitability for parachute drops and helicopter landings ranges from good to poor, de- pending largely upon the extent of brush and trees. Unit A3 consists of beaches and adjoining sandy terrain forming narrow areas along the coast. Most beaches are less than 20 feet wide and are too narrow for airborne operations of any sort (pl. ho). The sandy terrain adjoining the beaches is firm, flat, and well drained, but coconut trees cover most of this terrain and render it unsuitable for airborne operations (pl. ll A). Unit B1 consists of gently sloping (less than 30 percent), grass- covered upland terrain. Although grass is the dominant vegetation, brush is widespread and scattered trees are common (pls. h B, 3h B, and 55 B). The soil is generalLy firm, and bedrock is exposed in some places, but boulders commonly lie on the soil, and trenches are wide- spread (pls. 6 A, 16 A, and 55). Fixed-wing aircraft could not land on this terrain, but suitability for parachute drops and helicopter land- ings ranges from fair to poor. Unit B2 consists of gently sloping, forested upland terrain. Den- sity of the forest cover is varied but would be a serious impediment to most types of airborne operations. Brush and vines are widespread. Scattered boulders are locally common. Unit C comprises terrain entirely unsuited to airborne operations. Upland terrain of this unit has slopes greater than 30 percent; slopes steeper than 60 percent are common, and much of the terrain is rough. Meat of the terrain is covered with moderate to dense forest (pls. 5 A and 51 A), or less commonly, with a dense growth of vines (pl. 56 A). lowland terrain of Unit C consists of mangrove swamps (pls. 29 and 5%) and freshawater marshes (pl. 30). lhl o Cross-Country Movement by Richard L. Hay General statement The volcanic islands are largely uplands locally fringed by flat coastal lowland. Most of the upland terrain is forested and rugged and is largely'unsuited to movement of both foot troops and vehicles. Flat to gently sloping areas however, locally permit movement of men and vehicles on the uplands. Most of the coastal lowland are mangrove swamps and fresh-water marshes, both of which are impassable to most vehicles and are unsuited to the movement of foot troops. Elsewhere on the lowland, narrow areas of loamy sand fringing parts of the coast and local areas of fill are suited to movement of both foot troops and ve- hicles. Foot troops could traverse the coral islands with little dif- ficulty but cross-country movement of Jeeps and other wheeled vehicles would generally be hnpossible due largely to closely spaced coconut trees and areas of coarse coral rubble. vehicular movement Both upland and lowland terrains of the volcanic islands are largely unsuited to cross-country vehicular movement. Most of the up- land is rugged and forested and much of the soil is bouldery; World War II Japanese trenches and foxholes are widespread. In the uplands, the areas most suitable for cross-country movement (CCM) are the flat to gently sloping grass-covered areas. However, difficult access from the coast to most of these flattish grass-covered upland areas limits their value for vehicular CCM. Two-thirds of the coastal lowlands are swamps and marshes impassable to most vehicles; the remainder comprises loamy sand and fill, both of which are largely suitable for movement of most types of vehicles. Some clearing of coconut trees might be necessary. Closely spaced coconut trees, rubble ramparts, and marshes render the larger barrier-reef islands unsuited to the movement of most types of vehicles. Terrain of the volcanic islands is classified on maps 23 through 29 according to overall CCM conditions using the Jeep as a standard. Jeeps were driven on trafficable lowland terrain (Units A1, A2, and A3) but, due to lack of access roads, no tests were made on upland areas. Topography, vegetation, and soil were the principal factors considered in the terrain classification. Unit Al comprises four airfield runways built on fill. The airfield on northwest Moen, Moen Airfield, is now in operation and the runway has excellent trafficability. The concrete runways on south- west MOen, Eten, and Param have cracked, and grass, brush, and scatter- ed coconut trees are growing on them (pls. l, 2, 53 A, and 63 B). On the unused runways, conditions for Jeep movement range from good to fair. Unit A2 areas are fill (made land) on Mben, Dublon Island, Eten, Param, and T01. The fill is flat and ranges in elevation from sea level to 3 or b feet above high-tide level. Most of the fill is firm underfoot and has good traction. Some areas, particularly near the shoreline, have subsided as much as a foot and are soft and slippery. A number of small areas, particularly inland from boat ramps, are sur- 11+3 faced with concrete. Unfilled bomb craters, many with standing water, are common near the airfield runways. The vegetation is diversified; grass and young coconut trees are most common but brush and vines occur locally particularly on Dublon Island (pls. 31 and 32 A). CCM condi- tions of Unit A2 range from good to poor but are generally fair. Areas mapped as Unit A3 consist of raised-beach deposits and adja- cent beaches forming narrow strips along the coast. The narrow strips are flat and have elevations of l to 2 feet at high tide. Tne raised- beach deposits consist largely of sand which is nearly level, well drained, and firm underfoot. Coconut trees from 20 to 50 feet apart cover most of the raised-beach deposits, on which villages and scatter- ed houses are located (pl. 11 A). Undergrowth is sparse or absent. This terrain generally has good to fair CCM conditions, although coco- nut trees are a hindrance to movement, particularly of trucks and other large vehicles. Sand beaches generally fringe the raised-beach depos- its, from which they are separated by a scarp about a foot high cut into the raised-beach deposits. At low tide the beaches range from less than 10 feet to about 20 feet in width; at high tide all of the beaches are narrow and many are under water. Mbst of the beaches have a gradient of about 1:10 and are firm; trafficability of the beaches is generally good. Areas mapped as Unit Bl are flat to gently sloping (less than 30 percent) grass-covered upland terrain. Bedrock is locally exposed (pls. 6 A and 55 A), but more generally clay soil is at the surface. Boulders lying on the soil (pl. 55 B) and knobs and pinnacles of bed- rock (pls. 16 A and 51 B) are obstacles to vehicular movement in some places. Regardless of whether soil or bedrock is exposed at the sur- face, most of this terrain is uneven. Trenches are widely distributed and generally concealed by grass. In many places the grass forms a dense growth from 3 to 8 feet high (pls. 35 and 56 B), but locally the grass is l or 2 feet high (pl. 3% B). Brush is common in this unit. Traction on the dry soil is relatively good; the wet soil is slippery. In many places the grass is dense enough to stop a jeep but would prob- ably not seriously hinder tracked vehicles and heavier wheeled vehicles (pl. 56 B). CCM conditions are different in different parts of this CCM unit but are generally fair to poor. Areas mapped as Unit B2 consist of flat to gently sloping forested upland terrain, which commonly alternates with the grass-covered areas of Unit B1. Soil is similar to that of Unit Bl. Bedrock exposures and trenches are generally less common than in Unit 31' The vegetation ranges from sparsely forested grassland to dense forest with very lit- tle undergrowth. In the moderately forested areas, grass or a dense undergrowth of brush and vines is common. Although undergrowth is gen- erally sparse in the heavily forested areas, vehicular traffic is gen- erally impossible because of the close spacing of the trees. thh of this terrain is impassable to a Jeep, but CCM is locally fair or poor in the more open areas. Unit C comprises both upland and lowland terrains which are im- passable to Jeeps and most other types of vehicles. Upland terrain of this unit has slopes greater than 30 percent; slopes greater than 60 percent are common and scarps 5 to 50 feet high are numerous. Boulders are widely scattered throughout this terrain, and talus slopes and boulder fields are found on the larger volcanic islands. Mbst of this terrain is covered with moderate to dense forest (pl. 57). Less com- monly, the vegetation is a dense growth of vines (pl. 56 A). Lowland terrain of Unit C consists of mangrove swamps and fresh-water marshes, both of which are unsuited for vehicular movement because of soft mucky lhh Plate 55 A. Trachyte exposure, Witipon mountain, Moen. Looking west across bedrock exposure of trachyte forming the summit plateau of Witipon. 1954-55- B. Flattish upland on southeast Uman. Looking south— east across flattish upland at about 100 feet elevation. This benchland area is underlain by a single flow of olivine basalt. Recent burning has destroyed most of the grassland vegetation which normally covers this area. Boulders lying on and partly in the soil are visible at right. 1954-55. A. Dense grass and Vines near summit of Winifourer mountain, Moen. Foot troops would have difficulty penetrating this vegetation, which affords excellent concealment. l95fi-55. B. Grassland vegetationx south Uman. Soil is Truk clay. Tall grass in background is swordgrass (Miscanthus flor— idulus) and short grass in foreground includes Dimeria and Ischaemum. December l95h. Plate 56 Coconut-breadfruit forest on northwest Tol. Plate 57 January 1955. bottoms, generally dense vegetation (pls. 7 A, 10 A, and 30 B), and water as much as a foot deep in the fresh-water marshes and 3 feet deep in the mangrove swamps. M0vement of foot troops The features rendering most of the terrain on the volcanic islands impassable to vehicles also limit movement of foot troops; terrain hav- ing fair or good vehicular CCM is correspondingly suitable to the move- ment of foot troops. The areas of map Units A1, A2, and A3 (maps 23 through 29) are suitable for the movement of foot troops, the chief hindrance being local marshy areas covered with dense grass in Unit A2, particularly on Dublon Island (pl. 31 B). Suitability of Units B1 and B2, the gently sloping upland terrain, is good to poor for movement of foot troops. Mbvement of foot troops is generally best on the forested areas in which the undergrowth is commonky sparse. In many places a dense growth of tall grass (pls. 35 and 56 B) greatly impedes walking, and trenches and foxholes concealed by grass would be an added hazard to the movement of root troops. Unit C areas are largely poor to unsuited to movement of foot troops. The upland terrain of this unit is generally steep and rough, and the direction of movement is limited in many places by scarps. Vines in the forested areas commonly inhibit movement, and many un- forested areas densely covered with vines are almost impassable (pl. 56 A). mangrove swamps are difficult to traverse, as a man would sink waist-deep in the mucky bottom of most swamps, and the subaerial man- grove roots form a dense growth. The freshawater marshes are a rather similar obstacle to the movement of foot troops, although a man would probabxy sink no more than 6 inches or a foot in the marginal parts of the marshes, particularky the smaller ones. Grass and brush locally form a dense growth in the fresh-water marshes (pl. 53 B); where taro has been planted vegetation is generally less of an obstacle (pl. 30). The coral islands are suited to the movement of foot troops. The rubble ramparts are not a serious obstacle nor are the fresh-water marshes, in which a man would rarely sink more than a foot. The scat- tered undergrowth is generally not dense enough to obstruct foot troops. 1&5 ENGINEERING ASPECTS OF TERRAIN Engineering Materials by James E. Paseur and Harold G. May General statement Abundant supplies of rock and earth construction materials are generally available in the Truk Islands. Fairly accessible cliffs and rocklands on most of the high volcanic islands will supply large amounts of hard compact lava equal to the best continental trap rock. This rock is suitable for crushing for concrete and for surface and base course aggregates: Joint blocks are suitable for light and heavy riprap rock and for heavy masonry. Similar exposures of undifferenti- ated lavas and breccias will supply large quantities/of select hard rock suitable for crushing for base and surface courses. Accessible cliff and rockland exposures on Mben will supply large amounts of pit- run material suitable for fill and for subbase course. Fairly accessi- ble cliffs of well—bonded breccia and lava on Udot will supply large amounts of rock suitable for crushing for surface and base courses. Cliffs of fairly well bonded breccia on Moen and Dublon Island will supply pit-run aggregate suitable for fill. 0n the volcanic uplands undifferentiated volcanic bedrock every- where underlies earth overburden from 1 to 50 feet deep in most places. There are extensive areas on several volcanic islands where the soil overburden on good hard lava bedrock is only from 1 to 5 feet deep. When stripped, these localities will supply large amounts of rock suit- able for crushed aggregate, for concrete, and for base and wearing courses. Scattered deposits of coarse- to fine-grained calcareous beach sand occur on some beaches of the barrier-reef islands and on discon— tinuous stretches of the beaches around the volcanic islands. The lime sand also forms the low coral islands within the lagoon and the adja- cent sandy shoals. Pit-run sand is suitable for filler and the cleaned processed sand is suitable for mortar sand and fairly suitable for con- crete. Thin surficial deposits of coral boulders, cobbles, and gravel are the only terrestrial sources of coarse aggregate on the reef islands. The crushed rock is suitable for aggregate for base and subbase courses and for waterbound macadam. Awash coral limestone of adjacent reef flats will supply a large volume of similar material. The crushed reef limestone is fairly suitable for base course and waterbound macadam. All the hard lavas and the well-bonded breccia require drilling and blasting. Some blasting will expedite removal of the fairly well bonded breccia, the moderately hard lava, and the awash reef limestone. In shallow soil areas, the overburden can be easily removed with bull- dozers and scrapers. Granular material can be easily excavated with power equipment. In shallow parts of the lagoon, sand can be recovered with barge—mounted power equipment and lighters during the calm period from April to August, but the lagoon is probably too rough during the rest of the year. Near-shore reef limestones can be recovered with shore-based dragline equipment during lOW'tide. The soil overburden on the upland volcanics is divided into two major groups differentiated on the basis of depth. The first group in- cludes (l) deeply weathered, lean clay or clayey silt (10 to 50 feet 1&7 thick over volcanic bedrock), (2) deeply weathered, stony, lean clay or clayey silt (l to 30 feet thick over volcanic bedrock), and (3) minor local inclusions of boulder talus (1 to 50 feet thick over volcanic bedrock). The deeply weathered, lean clay or clayey silt, which is found on all of the major and most of the smaller volcanic islands, will suppky abundant amounts of easily excavated material that is suitable for binder clay and fill. The deeply weathered, stony, lean clay or clayey silt, which is found on all of the volcanic islands except two bare rock islets of Atkin and Tako, will supply unlimited quantities of earth suitable for fill. The bearing capacity is good to poor so heavy structures should be founded on the underlying bedrock. The boulder talus, which is found on all of the major volcanic islands, will supply large quantities of rock suitable for riprap rock and stone masonry. The bearing capacity of the talus is good if the boulders are stabi- lized. The second group includes (1) a soil complex (1 to 10 feet thick) composed of about 70 percent stony, lean clay or clay silt and 30 per- cent stony, fat clay or clayey silt and (2) the limonitic, gravelly, lean clay or clayey silt (l to 8 feet thick over volcanic bedrock). The thin or shallow, stony, lean and fat clays, or clayey silt complex, which is found in limited acreages on most of the volcanic is- lands, will furnish some material suitable for binder clay and fill. The limonitic gravelly clay or clayey silt, which was observed in small acreages on most of the major islands, has a good bearing capacity. In localities where this unit is sufficiently extensive, such as on Ulalu, the gravelly surface materials can be used as road metal. Another important soil, the muck and peat, is found in fresh-water marshes on the coastal lowlands around most of the volcanic islands. It ranges in thickness from h to 15 feet and is generally underlain by calcareous sand. The bearing capacity is negligible. Construction on this unit would have to be founded on the sandy substratum. Introduction The engineering materials section consists of a text, seven maps, and six tables which present information on occurrence, use, and in- place characteristics of the upper 100 feet of rock and earth materials. The text consists of descriptions of 18 map units of different en- gineering materials (maps 30 through 36). Rock Units 1 through 5 are exposed volcanic bedrock; Unit 6 is bare coral limestone. Unit 7 is calcareous beach sand. Deep earth Uhits 8 and 9 are residual volcanic clays or bouldery talus on volcanic bedrock, mostly basaltic lava. Units 10 through 1h are lava bedrock with a mantle of thin residual clay soils. Unit 15 is mangrove-swamp deposits and Unit 16 is marsh- 1and muck and peat. Units 17 and 18 are fill and coral rubble respec- tively. The descriptions in the text are to assist in field recogni- tion of the map units. The maps (maps 30 through 36) show the distribution of the differ- ent engineering units, locations of quarries, and the sites of engineer- ing test samples. The maps are a special-purpose compilation to show ghere different kinds of rock and earth are at or near the ground sur- ace. 1A8 Table 17. Engineering materials: field conditions affecting operations, 'n'uk Islands Excavation Conditions Stability of Excavation Slopes Stable Seem Slope Ratio Natural Slumping Depth to and Drainage Engineering Vaterials Unit Description landforms mickneee of unit Method Required (Eetmeted) Slope and Erosion Water Table Drainage Control Foundation Condition (see maps 30 through 36) . 0101150315“ : (Observed) 31151118 (average) Rates Required vertical) 1 Hard compact lavas Uniformly hard canpact basalts and ande- Cliff exposures and sumit flats Single mapped 1’1","3 35 to 160 ft. Drilling, bleetins, and We! 1/211 ‘0 1/ 16:]. UP 1‘0 “WEI-1 50‘ clamping Negligible Perched “It” Slow in .10de Enclosed pits re- Excellent bearing capacity except near edge of sites; Jointing is cannon. thick equipsent y g/ rock quire drainage Jointed cliffs where supporting rock may sllmp 2 Hard mixed lavas Heterogeneous hard basalts and andesites Mainly cliffs or steep slopes undivided flows 25 to 100 ft. Drilling, blasting and power l/2:l to l/u:l Up to nearly Sale duping 116511311719 Perched water Slow in Jointed Mcloeed pite re- Excellent bee-ring capecity except near edse of of various compositions and textures, thick; f1“ series 13 “P to equipnent vertical 1/ g/ rock quire drainage Jointed cliffs where supporting rock W slump some breccia and dikes; Jointing scallion several hundred feet in lavas 3 Moderately hard lavas Moderately hard and relatively weak Cliffs and sane rolling upland Series of flows up to 150 ft. Power equipnent; drilling and l/2:l to vertical Up to vertical Negligible Negligible Unknown Very slow Enclosed pits re- Excellent bearing capacity but not as high as tracnytic lava; fracture systems cannon terrain of Uitian mountain, Moen “ii-Ck 1’1“th would facilitate exca- quire drainage of Units 1 and 2 vation. Difficult with hand tools 1it Hard mixed breccia and Minly hard firmly bonded volcanic breccia Sea cliffs and escarpents UP ‘70 100 ft. thick Drilling, blasting, "1‘1 power 1/ 2:1 t° 1/h:l ”'1’ t0 vertical Sane 911139198 “631181519 Perched water 53917980 310118 Enclosed pits re- Excellent bearing capacity; drainage construc- lava with sane included lava and a dike series; equipnent y 810116 dike dikes quire drainage tion probably needed where footing is across some widely spaced Joints contacts g dikes 2/ 5 Mixed volcanic breccia and m consolidated volcanic breccia with cliffs and stream beds of pocket Breccia up to 300 ft. thick; Power equiment generally; drill- 3/ I4:1 Up to nearly 01 steep slopes Little to Perched water Generally ve Required in Excelle t be - conglanerate minor beds of consolidated conglomerate valleys conglomerate beds 5 to 25 ft. ing and blasting would facilitate vertical sane slumping in negligible along contact slow ry closed pits may require gmfiztztfighfi: $1255 thick . excavation conglalerates zones seepage along its masonry faces 1/ 6 Coral limestone Relatively weak, porous, moderately hard Scattered ledges in the tidal Unknown Power equilncnt senereJ-Lv; drill-ins Probebhr 1/2:1 About 10:1 Move Unlmovn 0 to 3 ft Moderately slow Coffer dams below Exc . elle t be coralline limestone zone along beaches and blasting “mild facilitate ex- basal water table always be mixe3fitzi’tzglefg/Otms will cavation. Difficult with hand tools 7 Calcareous beach sands Poorly graded, coarse to fine sand can- Beaches and low sandy flats along 1.111an M t°°15 “Out 1 1/ 2:1 About 1‘31 Excessive on overly W3 only 0 t0 3 ft. Very rapid None above water Probabhr very good bearing capacity where posed of angular to subsngular fragnents the beaches eteepened 5102993 W198 torren- confined and stabilized §/ of marine organims t1111 flooding 8 Deep stony clays Stony, lean, granular, film to very firm, Mountain sides and steep valley Stony lean clays 1 to 30 ft. Hand tools and power equipuent in 1 l/azl to 1:1 Up to 1:1 Large boulders may Sane raveling airface seeps Generally well Site drainage Bear ca it good t . . o r on sto lean slightly plastic clay with 15 to 50% em— slopes thick, bouldery talus O to 50 stony lean clays, power equipnent sllmp on cut slopes on 1:1 slope in places but drained in stony probably needed clayrvarfigleyon bouldelliozalus E73, bedded residual boulders; about 51 of unit ft. to bedrock in boulder talus estimated avg. clays; moderate- is boulder talus with 50 to 90$ volcanic depth more 1y rapid in blocks ‘4 in. to 10 ft. across embedded in than 20 ft. bouldery talus firm, granular, plastic clay 9 Deep residual clay Red residual lean cm; firm, slightly Mountain crests, hilltops, 10 to 50 ft- to bedrock Band tools Up to 1:1 Up to 1:1 Sane 51mins on over- Minor elekins Unknown Genera-llv well In closed pita Bear ca it good to r- s sinage plastic, and well drained; generally con- saddles, and footslopes LY steepening 51°F" and raveling drained y CWtigCti-gzcnegded in 105:: éegeB-I‘dzfifi _1_l/ tains some residual cobbles and boulders in wet season on (“It slopes . of volcanic rock below surface 10 ft. 10 'min clays on hard 70% lean, rim, granular clay and 30$ fat, Undulating uplands Earth 1 to 10 ft. to bedrock of Drilling, blasting, and power About 1:1 in About kzl in Sane slumping in Only in sur- Perched water Slow in both biolosed pits re- Beari ca it ood to - can“ 13"” very fim’ impervmus c1” ‘ beam“ 1“ unit 1 type so t° 160 ft' thick equipment 1“ bedr°°k5 hand t°°la em‘ “P t° em“ °W ficial clears locally soil and bedrock quire drainage excellgnt Efrain?“ Poor on cms' hard canpact lavas of Unit 1; sane local in the clay 1/“:1 in bedrock bedrock outcrops and scattered boulders 11 Thin clays on hard mixed Earth same as in Unit 10; bedrock same as Gently sloping uplands Earth 1 to 10 no deep; bed- Drill-ins, blastins, and power About 1:1 in About 4:1 in Some shaping in 0am in eur- Perched water Slow in both melosed pits re- pen-ins “wit . Y 800d to poor on clays lavas in Unit 2 rock series up to several equipment in bedrock; hand tools earth; up to earth earth ficial clws locally soil and bedrock quire ailing ’ hundred feet thick in the clay l/h:l in bedrock dr e excellent °n beam“ 12 'Ihin clays on moderately Earth same as in Unit 10; bedrock same as undulating uplands Soil 1 to 10 ft”; bedrock 1‘5 to Band tools in the clay; in the bed- 1/ 2:1 to vertical About ‘H1 in Neal—tsible 0an 1n eur- Unknown Very slow in Enclosed its re- Beari c it 0d t - hard lavas in Unit 3 150 ft. in thickness rock, power equipnent; drilling and in bedrock; earth ficial clays bedrock quire drainage excellgntagzcbegrgzk 0 poor on Clays, blasting will facilitate excavation 1 l/2:l in earth l3 'Ihin limonitic gravelly Surface 1 to 3 ft. of earth contains 30 Rolling uplands Soil 1 to 8 ft., avertise 2 1/ 2 In the bedrock, power equilment; 1/ 2:1 to l/hzl in Up to Ml in Sane slumping in Only in sur- locally perch- Slow in clayey ho- Required in closed Good to fair 0 . - clays on hard canpact to 70$ gravel-sized ferruginous concre- ft.; bedrock 50 to 160 ft. drilling and blasting “11—1 facili- bedrock; 1 1/ 2:1 earth earth ficial clays ed water table risen and bedrock; pit in both earth rock. Footingnsgg,i:xzfie;:o::bbl;d lavas tions: where earth more than 3 ft. thick, thick tate excavation; hand tools in the in earth usually rapid in and bedrock requires drainage protection y surface gravelly layer separated from clay - gravelly layer bedrock by a yellowish lean clay horizon; - bedrock same as in Unit 1 in Thin limonitic gravelly Earth same as in Unit 13; bedrock same as Rolling uplands Earth 1 to 8 1%.; bedrock up In the bed-rock, power equilnent; 1/2:1 to 1/“:l in UP to 1H1 in Some shunning in Only in earth locally perch- ‘ Slow in clayey ho- Required in closed Good to fair on 1- _ clays on hard mixed in Unit 2 to several hundred feet drilling and blasting will facili- bedrock; 1 1/ 2:1 earth earth ed water table rizon and bedrock; pit in both earth rock. Footing smart,izeixgfie$o::bl;d lavas tate excavation; hand tools in the in earth usually rapid in and bedrock requires drainage protection y clay gravelly layer 15 Move-swamp deposits Brackish- or salt-water-swamp_deposits, Submerged salt-water coastal W Hand t°°15 """ Level W P°551b1¥ Flooded ------------ Bearing capacity probably ranges from none on mostly loamy sand, locally overlain by flats eroded by tidal the “Ck and peat ‘50 800d on 36nd bottan 1f muck and peat; subuerged 0.5 to 2.0 ft. current Send Support is protected against current ero— at high tide; scattered to dense mangrove ° sion. ‘Piling support or displacement by rock vegetation fill required in muck and pest areas l_2/ 16 Marshland deposits Low coastal marsh deposits of various Marsth 1 to 15 ft- in explored “935 Hand tools """ level MM Unknown At 01' near ------------ Bearing capacity of this unit is none to very depths and ratios of muck and peat. 0n surface , poor because the water holding capacity is seaward side, bordered by either mangrove very high and specific gravity very low. Pil- swamps or lime sands and underlain by ins support or displacement 01’ muck by rock lime sands. Where unit borders calcare- fill is required for adequate foundation ous beach sands, they interfinger 10 to support l_2/ MO ft. ; on upland borders, muck and peat is underlain by plastic clay 17 Fill Mostly broken rock with clay binder; Flat areas on coastal plains """" PW“ equipment and hand t°°15 """""""""""" 0 to 3 ftn "ell drainea ------ Bea-ring capacity usually excellent to good locally included some coral sand and average 2 above water at surface y gravel; some areas paved with concrete to 3 ft. table 18 Coral boulders, cobbles, Unconsolidated coral-reef detritus l in. Boulder fields and surficial O to 7 ft. thick Hand tools and power equipnent About 1:1 Level to lml Negligible Unknown 0 to 7 ft. Very rapid None Excellent if enough filler is added' obably and gravels to 3 ft. in diameter gravel beds on the barrier- needs protection from high on-shore’sgzm reef coral islands waves y Loose Joint blocks of cliffs slump when disturbed §/ This unit apparently is fairly impervious because spring zones are comon 31°35 its upper “I’m“ y Heavy structures probably require footing on the bedrock with lava flows 2 Spring zones exist along smie basal contact zones 12 Ade te subsurface exploration should be made t all construction 113 J 1/ mtrapped water may cause disintegration of the bedrock matrix J qua a s s Fracture oints are tight and apparently impervious 1 Extreme hea manent structures bab shmlld be founded th ' y J _8/ Waterproof cellular foundation structures require enough weight per unit volume to prevent flotation _3/ 13’ W P9 pro 15’ on e bedrock 13/ Large slump blocks of breccia are cannon along the base of cliffs if water table rises above normal levels 2/ Canpaction by heavy equipment would probably increase the impervious condition which would necessitate drainage facilities _5/ Subterranean drainage commonly channeled along dike contacts Drainage construction may be required in enclosed pits in the stony lean clavs Ewe Pz-obably good to excellent bearing on bouldery talus when rock blocks are bridged or stabilized 1149 Table 18. Areal distribution of engineer- ing materials units, Truk Islands. (in square miles) Engineering 1 2 3 h 5 6 7 8 9 10 11 12 13 1h 15 16 17 18 ISIS-Dd Unit Hard' compact Hard mixed Moderately Hard mixed Mixed volcanic 00111 calcareous Deep stony Deep 5min clays Thin clays Thin clays on Thin limonitic min limonitic Manyove- Marshland Fill Coral boulders, Total lavas lavas hard lava breccia breccia and limestone beach sands clays residual on hard on hard moderately gravelly clays gravelly clays swamp, deposits cobbles, and area 811d lava conglomerate clays compact lavas mixed lavas hard lavas on hard on hard deposits gravel compact lavas mixed lavas Eastern group Moen 0.157 0.1311 0.01+7 - 0.030 < 0.001 0.197 2.998 1.506 0.137 0.162 0.057 0.0111 - 0.657 0.677 0.393 - 7.19 Falo - 0.001 - - - - 0.019 0.036 0.029 - 0.007 - - - - 0.007 - - 0.13 Dublon Island 0.033 0.061 - - - < 0.001 0.063 1.267 0.8111 0.039 0.056 - - 0.00h 0.196 0.068 0.739 . - 3.39 Eten - 0.002 - - - - - 0.030 o.ooh - - - - - - - 0.153 - 0.19 Fefan 0.063 0.1l+0 - - - < 0.001 0.205 2.630 0.1119 0.022 0.269 - - 0.0149 0.696 0.112 - - 11.68 Param - < 0.001 - - - - 0.039 0.1110 0.120 - - - - - - 0.0911 0.095 - 0.119 Tarik - - - - - - 0.021 0.078 0.021 - — - - - - 0.060 - - 0.18 Tsis - < 0-001 - - - - 0.036 0.096 0.067 - 0.012 - - - - 0.011 - - 0.22 Uman 0.0111 0.016 .. - - < 0.001 0.0911 1.082 0.015 - 0.053 - - 0.037 0.131 0.108 - - 1.55 Central group . Udot - 0.019 - 0.036 - < 0.001~ 0.115 0.851 0,381 - - - - - 0.101; 0.218 - - 1.76 Eot - - - 0.003 - - - 0.077 0.031. - - - - - 0.001; 0.017 - - 0.16 Eiol - - - - - - 0.0111 0.007 - .. .. - - - . - - - - 0.02 Western group NE T01 0.182 0.023 - - - < 0.001 0.015 1.318 0.719 - 0.033 - 0.127 0.099 1.171 0.096 - - 3.81 SE T01 - 0.215 - - — < 0.001 0.12h 2.537 0.210 .. 0.180 - - - 0.1133 0.179 0.019 - 3.93 w T01 (Pata) - 0.080 - - - < 0.001 0.067 0.1016 0.311 - — - - - 0.680 0.097 - - 1.68 sw T01 (Polle) - 0.09h - - - < 0.001 0.1112 1.155 0.628 - - - - - 0.952 0.202 - - 3.1+? Fala-beguets - 0.002 — - - 2 0.059 0.103 0.2117 - 0.052 - - 0.018 0.1h2 - - - 0.62 Ulalu - 0.002 - - - 2 0.056 0.051 0.020 - 0.035 - - 0.125 — 0.0h1 — — 0.33 Barrier reef I 22 islands - - - - ~ - 0.1 7 0.5 '2 - - - - - - - - - 7 0.7 ‘2 Total 0.1119 0.819 0.0117 0.039 0.030 0.1+? 1.9 2 15.201 5.575 0.198 0.859 0.057 0.168 0.377 5.166 2.017 1.399 0.72 Terrain Rockland areas of bare bedrock Coastal lowlands Deep clays Thin clays Thin gravelly clays Swamp Marsh Fill Coral islands Volcanic uplands and islands of the barrier reef Volcanic uplands Coastal lowlands of the barrier reef .151 Table 19. Engineering test data; Truk Islands . Mechanical Analysis unit weight, lb/cu ft Standard Compaction sample Engineering Materials unit laboratory Cumulative Percent Passing ’ Specific Gravity Absorption ibfiagign Air Dried Samples Asphalt A.A.S.H.O. T99-#9 Be 83:11ng:21: y Sample 3 8% .2 1% l 3/# 1/2 3/8 # # # # # # Apparent Bulk_i Bulk (S.§:D.) _ 500 rev- Rodded Loose Stfilmin Optimum Maximum No, l/ No. in IR 1n in in in in in # 10 20 #0 80 200 Coarse Fine Coarse Fine Coarse Fine Coarse Fine (%) PP g moisture Density CBR Swell Coarse Fine Coarse Fine (1.) (lbs/cu ft) (1,) (1:) R1 1 Hard compact lavas 3065 2/ — - 100 95 69 #7 30 23 12 7 5 3 3 2 2.78 2.73 2.62 2.55 2.68 2.61 2.2 2.7 18 96 106 88 ,95 None 10.9 98 19 0 R2 2 Hard mixed lavas 3066 2/ - - 100 100 87 59 36 2# 10 6 3 3 1 3.05 2.99 2.96 2.8# 2.99 2.89 1.0 1.8 16 10# 110 98 102 None 1.2 122 30 +0.0# _ 7 Calcareous beach sands 3/ 3067 93 91 89 .82 75 69 62 56 #8 #3 31 11 7 6 2.62 2.72 2.1# 2.52 2.33 2.59 8.5 3.1 #2 ## 9# 39 87 Slight 1#.3 97 16 0 _ 7 Calcareous beach sands 3/ 3068 - - - — 100 99 97 95 83 71 52 10 2 1 2.62 2.76 1.80 2.#9 2.11 2.59 17.3 3.9 3# 5/ 87 5/ 79 Slight 17.# 86 21 0 R5 1 Hard compact lavas 3069 2/ - - 100 99 77 #9 31 23 13 8 5 # 3 2 3.08 3.09 2.99 2.98 3.03 3.01 0.8 1.2 15 10# - 95 - None 1.9 120 37 0 R6 3 Moderately hard lava 3070 27 - - - 100 91 72 #8 37 23 16 13 11 10 10 2.62 2.78 2.37 2.## 2.#6 2.56 #.1 5.0 86 d 93 109 86 99 Slight 11.3 117 7# +0.08 R7 1 Hard compact lavas 3071 2/ - - 100 99 80 51 33 2# 13 8 5 # 3 2 2.93 2.95 2.82 2.70 2.86 2.79 1.# 3.1 1# 100 - 93 - Slight 3.2 116 28 0 Rs 1 Hard compact lavas 3#22 g/ — - 100 98 81 56 32 23 12 8 6 5 # 3 3.09 3.12 2.9# 2.80 2.98 2.91 1.5 3.7 21 108 119 99 105 None 7.# 118 33 0 39 1 Hard compact lavas 3#23 g/ - - 100 99 85 60 35 2# 12 7 # 3 2 l 3.13 2.9 3.08 2.72 3.10 2.76 0.6 1.6 15 110 11# 101 10# Bad 3.2 123 #2 0 R10 2 Hard.mixed lavas 3#2# 2/ - - 100 100 82 56 35 27 16 10 7 6 5 3 2.91 2.83 2.72 2.63 2.79 2.71 2.# .7 23 98 11# 90 105 None #.7 118 38 +0.01 R11 5 Mixed volcanic breccia 3#25 g/ - - 100 99 76 50 32 25 15 10 7 5 # 3 2.57 2.75 2.20 2.2# 2.3# 2.#3 6.5 8.3 36 87 95 78 86 Slight 6.7 106 33 +0.02 and conglomerate R12 5 gifisgozgigzgiztzr3;cia 3426 - - 100 100 86 61 38 28 15 9 5 # 3 2 2.86 2.89 2.#8 2.19 2.61 2.#3 5.# 11.1 #5 91 100 8# 92 None 9.2 105 19 0 313 # Hard.mixed breccia and lava 3#27 g/ - - 100 98 70 ## 28 21 12 7 5 3 2 2 2.75 2.83 2.68 2.65 2.70 2.71 0.1 2.5 16 98 107 90 95 Bad #.8 115 32 +0.01 s6 7 Calcareous beach sands 3/ 3581 - - 100 100 99 98 97 96 95 92 72 #8 18 9 2.#8 2.53 1.72 1.67 2.03 2.01 17.7 20.2 5/ lé/ 69 5/ 61 5/ 3#.0 7# 32 0 s7 13 a 1# limonitic gravelly clays #0#l - - - - 100 100 99 98 8# #2 l# 10 6 # - 3.15 - 2.32 — 2.59 - ll.# #7.5 - - - - - 13.9 115.7 52 +0.02 E2. hffitflfiflti For location of sample sites see Engineering Materials maps, maps 30 through 36. Sample crushed in the laboratory using a small chipmunk crusher. Sample graded as received by laboratory. Test specimens compacted at maximum density and optimum moisture, standard compaction AOAOSOHIO. 13681913131011: ‘199-1‘90 Insufficient sample for test . 153 Table 20 . Soils mechanics test data, Truk Islands . DISTURBED SAMPLES UNDISTURBED SAMPLES Standard Compaction California A.A.S.H.O. r19949 Bearing Ratio y Consolidation Mechanical Analysis (in percent) void ratio Shearing 5011 Classification Physical Tests Specific Moisture Maxirmm CBR Swell Moisture Density Initial w/tons/sq ft load Strength 5/ California Sample Soils Unit Earth part of laboratory Depth of Sample Percent passing Sand Fines 7° dry ”/3 dry void Bearing No. 1.] Engineering Sample #10-200 (#200 L°L- P-L- P-I- Gravity weight density (9‘) (‘5) weight in place Ratio Corps of Bureau of Materials Unit No. Disturbed Undisturbed # # # # # # # (2-.07h mm) (<.07h mm) 019131er for when 0-5 1 2 1+ Engineer Public Roads y 1+ 10 20 1+0 60 1110 20 compaction (lbs/cu ft) sampled (lbs/cu ft) ratio ¢e Ce (7,) (revised) 58 2 Truk stony clay 8 Deep stony clays h0h2 6-60 in 3/ 100 100 99 96 93 88 86 1h 86 52 1.1 11 2.62 hl.9 75.1 15 +0.12 - - - - - .. - - - - Mg A_7 l Truk clay 9 Deep residual s2 clays (1) 3&29 0-66 in 20-2h in 100 100 100 99 96 81 75 25 75 61 A9 12 2.82 no.2 7h.o 17 +0.06 12 65 1.93 1.91 1.88 1.85 1.78 27° 300 8 MH A—7 S3 (2) 3430 h-60 in 30-3l+ in 100 100 100 98 96 89 86 lit 86 81 53 28 2.71; hl.2 75.0 13 +4.10 51 61 1.67 1.6h 1.62 1.62 1.53 20° 150 7 MH 11-7 85 (3) 3182 0-11 ft 10 ft- 100 100 100 98 98 91* 92 8 92 72 58 it 2.83 50.9 70.0 9 +0.15 31+ 73 1.76 1.76 1.7h 1.72 1.61 13° #00 3 MH A-7 10 ft 1% in $1 3 Fefan soils 13 & 11+ Thin limonitic gravelly clays on hard compact and on hard mixed lavas 3&28 0-63 in 26-30 in 100 100 89 82 80 75 73 27 73 61 38 23 2.98 16.5 112.0 31 +0.33 36 79 1.32 1.29 1.26 1.21 1.1h 25° 200 11 MH A-7 sh 7 Fill 17 Fill 3h3l 0-52 in 3/ 100 100 97 93 90 81 78 22 78 51 38 13 2.78 23.5 99.0 17 +0.15 _ __ _ _ __ _ _ _ _ _ m—Ml. A_.( 3.] For sample site locations see Engineering Materials maps, maps 30 through 36. 2/ Mechanical analysis of minus 10 mesh material A.S.'I'.M. designation: Dh22-51. a] No undisturbed sample submitted for testing. J Specimens compacted at maximum density and optimum moisture, standard compaction A.A.S.H.O. designation: 19949. 5] Effective angle of internal friction and cohesion in lbs/sq ft for normal pressure, from 0 to 6,000 lbs/ sq ft (triaxial shear test, constant water content). 155 Table 21. Engineering materials suitability,‘ Truk Islands. (Suitability ratings, in order of decreasing suitability, are: excellent, good, fair, poor, and unsuitable . ) Untreated Bituminous Light riprap rock Engineering materials unit Undisturbed subgralde Subbase course Base course surfacing wearing surface Concrete aggregate Binder soil Fill Cut stone masonry and rubble masonry Heavy riprap rock 1 Hard canpact lavas Excellent Excellent y Excellent l] _2/ Excellent 2.] 3/ Excellent y 2/ Excellent 2.] Unsuitable Excellent _3_/ Excellent to Poor Excellent Excellent y 2 Hard mixed lavas Excellent Excellent y Excellent y Excellent y y Excellent to Good y Excellent to Good l/ Unsuitable Excellent g/ Excellent to Poor Excenent y Excellent 5/ 3 Moderately hard lava Excellent Good 1/ Poor _l_./ Poor y Unsuitable Poor 3.] Unsuitable Excellent _3/ Fair Fair 3/ Unsuitable h Hard mixed breccia and lava Excellent Excellent y Excellent y g/ Excellent 9] 3/ Good to Poor y g/ Good to Poor _l/ Unsuitable. Excellent y Poor Good to Fair 3/ Good to Fair 5/ 5 Mixed volcanic breccia. Excellent Good l/ y Poor y Good. y Unsuitable Unsuitable Unsuitable Excellent _3_/ Unsuitable Embedded boulders Unsuitable and conglomerate , Fair ‘6 Coral limestone Excellent Good _1/ Fair y Good y Poor l/ Unsuitable Unsuitable Excellent g/ Poor Good to Fair Poor 7 Calcareous beach sands Excellent to Good 5/ Good Unsuitable Fair 3] Fair Good to Fair é/ Unsuitable Good Unsuitable Unsuitable Unsuitable 8 Deep stony clays Good to Poor Poor 2/ Boulders Only Poor §/ Unsuitable Boulders only Poor 1/ y Good to Fair l_0_/ Boulders only Boulders only Boulders only Good to Poor Good to Poor Excellent y Excellent y Excellent y 9 Deep residual clays Good to Poor Poor _‘U Unsuitable Poor _8_/ Unsuitable Unsuitable Poor y 2/ Good to Fair 19/ Unsuitable Unsuitable Unsuitable 10 Thin clays on 1 Good to Poor - Poor 3/ Unsuitable Fair to Poor (3/ Unsuitable Unsuitable Poor 1/ y Good to Fair y Unsuitable Unsuitable Unsuitable 11 volcanic bedrock, 2 12 above units _1_l_/ 3 13 Thin limonitic gravelly 1 Good Good Good Good Unsuitable Unsuitable Poor 1/ _9/ Excellent Unsuitable Unsuitable Unsuitable 1h clays on volcanic bedrock, 2 v _ above units _l_'_l./ 15 Mangrove-swamp deposits Good to Unsuitable Sand only Unsuitable Sand only Sand only Sand only Unsuitable Sand only Unsuitable Unsuitable Unsuitable Good. Fair _3/ Fair Good to Fair 6J Fair y 16 Marshland deposits Poor to Unsuitable Unsuitable Unsuitable Unsuitable Unsuitable Unsuitable Unsuitable Unsuitable Unsuitable Unsuitable Unsuitable 17 Fill Good Good to Poor Fair to Unsuitable Good to Poor Unsuitable Unsuitable Poor y Excellent to Fair Unsuitable Embedded boulders Unsuitable Good to Unsuitable 18 Coral boulders, cobbles, Good Excellent _lj Good to Fair y Good l/ Fair l/ Fair y é] Unsuitable Excellent _3/ Poor Good to Fair Poor and gravel ‘ l/ When crushed and blended to proper size gradation. 2/ Asphalt film stripping test recommended for each source of supply. 13/ Binder lacking. J Only selected large blocks are suitable. 5/ Where confined and above water table. §/ Requires cleaning, processing, and blending to proper size gradation. 23/ High or probably high dust ratio. J Plastic to slightly plastic when wet. 2/ Requires addition of mortar sand to reduce plasticity. lg When properly compacted at optimum moisture. l_lj These suitability rating are for the earth portion of the units only; for characteristics of bedrock portion see appropriate unit. 157 (3 Table 17 is a tabulation of in—place characteristics of the differ- ent kinds of rock and earth described in the text. Table 18 shows the areal distribution of engineering map units by islands. Tables 19 and 20 give the results of the engineering tests run on rock and earth sam- ples by the U. S. navy Materials Tasting Laboratory at Guam. These tests measured certain physical characteristics of rock and earth such as density, porosity, shearing strength, coherence, and plasticity. Table 21 shows suitability of rock and earth materials for some engi- neering uses. Suitability terms used in this table and in the text, in order of decreasing suitability, are excellent, good, fair, poor, and unsuitable. The values are based on field evaluations and on interpre- tations of the engineering test data in tables l2 and 20. Table 22 gives the rock characteristics of existing quarries. Field data on rock and earth materials were derived from numerous observations at open pits, road cuts, and manmade tunnels and caves and from hand-auger samples. These observations supplied data on natural characteristics, including in-place properties, thickness of materials, boundary locations, and field relations of various kinds of rock and earth. Microscope study provided data on texture and mineral composi- tion of the volcanic bedrock. On the engineering materials maps (maps 30 through 36) no attempt was made to distinguish demonstrable from inferred boundaries. The maps are least reliable in areas of dense vegetation. The engineering units are either single geologic or soils units or combinations of them. The hard rock units are based on the composition, texture, and engineering characteristics of the rocks and on the lack of overburden. Soil units were largely derived from the engineering soil types of the Unified Soil Classification System. Units of rock and earth are combinations of bedrock units with different types of overburden. Common construction materials not found in the Truk Islands are stream gravels, hard recrystallized coral limestone, unconsolidated volcanic cinders, and ash. Unit 1. Hard compact lavas This unit area consists entirely of bare rock exposures of single thick lava flows composed uniformly of hard compact dark-gray basalts and andesites (maps 30 through 36). Both the basalt and andesite are commonly porphyritic; less commonly these rocks are uniformly fine grained. Steeply inclined to vertical columnar Jointing is common (pl. 13); the polygonal prismatic Joint blocks range from 3 inches to 5 feet in width and from about 1 to 8 feet in length. The principal exposures of the unit are cliffs; minor exposures are gently sloping rockland. Most of the unit is of basalt, but it includes some andesite. Flows range from 35 to 160 feet in thickness and are nearly level. Some lava flows of this unit are at the top of a volcanic series, but others are interbedded with other rocks of the series. landforms occurring in this unit are mainly precipitous cliffs 15 to 150 feet high and ranging from 50 feet to about a mile in length. Minor landforms are gently sloping, bare rock plateaus (pl. 16 A) and hilltops which are partly bounded on the downward sides by steep cliffs. 159 Extensive drilling and blasting are required in the massive bed- rock. Blasting will facilitate excavation of the jointed rock with power equipment. Loose joint blocks can be removed with hand tools. (’\ 0 Excavation faces of considerable height in massive bedrock are generally stable at l/2:l to l/h:l l/ (American Association of State Highway Officials, l9h9, p. 63). Faces in jointed bedrock are general- ly stable up to l/2:l, depending upon the attitude and tightness of the jointed mass. Steepest natural faces are vertical. Erosion is negli- gible except for slumping of loose joint blocks. Enclosed excavations require some drainage facilities because the massive rock is impervious and jointed bedrock at some localities is sealed by clay between joint faces. Seepage springs observed along flow contacts are indicative of some internal seepage or perched water. Bearing capacity of the rocks in Unit 1 is excellent. Heavy per- manent installations should be located at some distance from the top edge of jointed cliffs because slumping along the cliff face during (”K earth shocks of high intensity may weaken footing support adjacent to the cliff top. Unit 1 will supply uniformly good aggregate excellently suited for portland cement concrete (McConnell and others, 1950, p. 237-238), as- phalt concrete, and base and wearing course; aggregate recovery is uni- formly high. Large joint blocks suitable for cyclopean riprap rock are exposed in scarps at the northwest corner of Fefan and in the north face of the highest cliffs on the northern side of northeast Tol. For crushed aggregate, the joint blocks from one exposure require washing to remove a thin veneer of clay on the joint faces. Unit 2. Hard mixed lavas Engineering materials unit 2 consists of bare rock exposures of series of heterogeneous lava flows with some interbedded lenses of py- roclastic breccia and brecciated lava flows (maps 30 through 36). Hard dark-gray basalts and andesites of varying textures and densities com- prise about 80 percent of the unit; the remainder is breccias and amyg- daloidal or vesicular basalts. Rock blocks in the pyroclastic breccia are angular to subangular fragments of basalt and andesite, from 1 inch { to 6 feet across, which are embedded in indurated.matrix of fine vol- ‘ canic debris. Porphyritic basalt and andesite are more common than the uniformly fine-grained types. Commonly, both the basalts and andesites exhibit steeply inclined to vertical columnar jointing, with the joint blocks ranging from 3 inches to 5 feet in width. Variously inclined dikes of lava are common on Udot and vertical dikes are common on Tol. Breccias and amygdaloidal or vesicular basalts occur throughout T01. Individual lava flows are about level and range from 25 to 100 feet in thickness. The rock is several hundred feet thick on the crest of Mbunt Tumuital, Tol. Many unmapped ledges of hard compact lavas occur in Unit 2. landforms found in this unit include steep cliffs, or series of cliffs one above another, ranging from about 20 feet to several hundred 17 In this chapter, gradient is expressed as ratio of horizontal to vertical. \ 16o (i0 feet in height and from 50 yards to several hundred yards in length. Gently sloping rockland occurs on hillcrests, plateaus, and benches along the slopes. Extensive drilling and blasting are required to remove massive bed— rock and will facilitate excavation of breccia and Jointed rocx. Blocks of loosely Jointed lava can be removed with hand tools. Excavation faces in massive bedrock of lava are generally stable at 1/2:l to l/h:l. Faces in Jointed lava or breccia are probably sta- ble at about l/2zl. Steepest natural faces are vertical. Erosion is negligible except for some slumping of loose Joint blocks in the lava or loose rock blocks in the breccia. Excavation pits require some drainage facilities because most beds of the unit are impervious and will not absorb runoff and contact seepage. Excavations on steep slopes probably require upslope interception ditches to divert runoff. The bearing capacity of the rocks in this unit is excellent. Heavy permanent installations should be located at some distance from cliffs because slumping of Jointed rock in the cliff face may weaken footing support. Anchored footings based on contact zones of the unit require drainage safeguards. Large installations on steep rockland slopes require upslope interception ditches to divert runoff from foun— dations. Unit 2 will supply some selected lava aggregate suitable for con- crete aggregate, base course, and macadam; aggregate recovery is vari— able and considerably lower than for Unit 1. Pit-run material is suit- able for subbase course and common fill if filler or binder is added. Joint blocks of lava are suitable for riprap rock and rough stone ma- sonry. vesicular and amygdaloidal basalts are suitable for base and subbase courses and also for fill if binder is added. The breccias are suitable for subbase course and fill if binder is added. Unit 3. Mbderately hard lava The only area mapped as Unit 3 is the bare rock exposure of the thick trachyte flow exposed on the crest of Witipdn, Moen (see also geology maps 5 and 6). The lava is moderately hard, light gray in color, and probably impervious. It is generally fine grained with sparse scattered phenocrysts of feldspar. The bedrock is extensively fractured and has a platy parting which is about normal to the fracture Jointing. The fracture Joints are generally tight and apparently water cannot flow along them. The trachyte flow dips gently eastward and has a measured thickness of at least 150 feet. The moderately hard lava overlies bedrock which is like the rock in Unit 2. Unit 3 occurs as rockland of the summit plateau and upper cliffs of Witipdn, Moen. Bedrock can be excavated with power equipment but some blasting will facilitate removal. Excavation by hand tools is difficult. Exca- vation faces are probably stable at l/2:l to vertical. Steepest natu- ral faces are vertical. Erosion is negligible. The bearing capacity of the rocks of Unit 3 is excellent but is lower than that of the hard lavas. Footing supports along cliff tops may be weakened by some slumping of fractured rock in the cliff face. 161 Unit 3 will supply material suitable for fill if binder is added. Fracture blocks have fair suitability for rubble masonry because the rock can be split along its platy parting. Unit #. Hard mixed breccia and lava The bare bedrock exposures mapped as Unit h on Udot and Eot are hard, coherent, massive, dark-gray pyroclastic breccia with intermixed lava and related broken lava. The breccia is about 70 percent of Unit h, broken lava is 20 percent, and the rest is lava flows and dikes. Both the breccia and the lava are of basaltic composition. Angular to subangular rock blocks in the breccia, 1 inch to several feet across, are so firmly bonded with the hard, well-indurated matrix that the rock breaks across both the blocks and the matrix. The matrix is 10 to 60 percent of the breccia mass. Bikes, 1 to h feet across, out both the breccia and lavas. The lava flows and associated broken lava localky interfinger with the breccia and some of the pyroclastic rocks appar- ently are embedded in lava groundmass. Most of the breccia is of mas— sive structure. lenses with included rock fragments of other lava and igneous rock are interbedded with the ordinary breccia. Cliff exposures of breccia at different levels apparently are exposed portions of the same thick bed of heterogeneous breccia. Unit h areas are the bare bedrock exposures of all breccias of Udot and Eot shown on the geologic map (map 3). The terrain consists of short bare rocky slopes and of sea cliffs ranging from 10 to #5 feet in height along the south coast of Udot; broken or irregular cliffs from 25 to 100 feet high occur on the inland slopes of the island. Drilling and blasting are required. Loose blocks of dike rock can be removed with hand tools. Excavation faces are stable at l/2:l to l/hzl. Some slumping may occur on steepest faces where the breccia is cut by dikes. Erosion is negligible. The natural ground surface ranges from horizontal through all degrees of slope to vertical. Excavations generally require drainage facilities to dispose of runoff and seepage issuing from dike contacts because the breccia is nearly impervious. The bearing capacity of Unit h is excellent. Foot- ing support along the top of dike-cut rock cliffs will probably be weakened if some slumping of cliff rock does occur. Footings anchored on dike contacts require drainage safeguards. Unit H will supply material suitable fOr fill and for subbase course if binder is added. Selected massive breccia is suitable for base course. loose Joint blocks of the massive breccia are fairly suitable for cyclopean riprap rock (pl. 1h). Smaller blocks of breccia are fairly suitable for riprap rock if selected for shape. Unit 5. Mixed volcanic breccia and conglomerate The areas mapped as Unit 5 are bare bedrock exposures of indurated volcanic breccia and conglomerate. The breccia is neither so hard nor so firmly bonded as breccia of Unit h. About 90 percent of Unit 5 is breccia; the rest is conglomerate. The breccia is mainly angular to subangular blocks of basalt and andesite, from 1 inch to 6 feet across, which are embedded in an indurated matrix of finer grained volcanic 162 debris. The conglomerate is composed mostly of rounded to subrounded rock particles of basalt and andesite, measuring from 1 inch to 6 feet across, and are embedded in well to poorly indursted matrix of volcanic detritus. locally the breccias grade into conglomerate. On Meen, most of the breccia bedrock exposures are part of a volcanic bed up to 300 feet thick. The best breccia outcrops are in cliffs and along deep ravines. Bedrock exposures of conglomerate, in beds from 10 to 35 feet thick interbedded with lava flows, are exposed in cliffs. Breccias are commonly interbedded with rocks of Units 1 and 2. Bedrock of Unit 5 commonly breaks across the indurated matrix but around larger rock fragments. The areas mapped as Unit 5 are the bare bedrock exposures of all the volcanic breccias and conglomerates which are shown on the geologic maps 1 through 7, excepting the breccias of Udot and Eot which are in Unit h. Weathered exposures of breccia and conglomerate consist- ing of boulders and cobbles embedded in residual clay are included in engineering Unit 8. Landfonms in this unit are broken or irregular cliffs from 10 to 75 feet high and 50 to 350 yards long. Drilling and blasting are generally'required in the breccia. Blasting will expedite the removal of conglomerate with power equipnent. Loose boulders or blocks can be removed with hand tools. Excavation faces are stable at 1/2:1 in breccia and at about 3/421 to l/2:l in the conglomerate. Poorly bonded boulders in conglomerate of the steepest faces probably will slump. Terrain in the unit ranges from gently slop- ing to nearly vertical. Erosion is generally negligible. Excavation pits in Unit 5 require provisions to dispose of runoff because the bedrock is fairly impervious. Spring zones along the upper contacts are probably indicative of some perched water lenses. The bearing capacity of rocks of Unit 5 is excellent. Slumping of loosened boulders or rock blocks in cliff faces may weaken footing sup- port of foundations located too near the cliff tops. Material from Unit 5 has excellent suitability for common fill and good suitability for subbase course if binder is added. Crusher-run breccia aggregate is probably fairly suitable for road metal. Uhit 6. Coral limestone Unit 6 areas are emergent coral lime, which occurs in narrow ledges in the intertidal zone along some of the beaches of low coral islands within the lagoon and on the barrier reef. The limestone is relatively soft, weak, and porous. The limestone is either massive or bedded, white to light-buff colored, and is well to poorly lithified. It is generally composed of coral heads and coral fragments, from half an inch to h feet across, embedded with some shells and other calcare- ous reef organisms in a porous, cemented, lime-sand matrix of reef de- tritus. Bedded or stratified beach rock consists of cemented lime sands and gravels of biogenic origin. Awash ledges of stratified beach rock dip gently seaward. Mbst of Unit 6 occurs between sea level and 3 feet above sea level. Exposures of Unit 6 are too small to show on the maps, but some exposures are located by symbols on geology map 8. The characteristic landform is a low, narrow, irregular, limestone bench along the shore. 163 Drilling and blasting will expedite rock removal with power equip- ment. Removal with hand tools is difficult. Secondary blasting will often be required. Stability of excavation slopes is not a problem be- cause of the low elevation of the coral limestone, 3 feet above sea level. Drainage problems are not significant as the highest limestone is only 3 feet above sea level. The limestone has excellent bearing ca- pacity generally. Footings on windward beaches within the lagoon and all along the barrier reef require anchoring to bedrock and protection against high on-shore storm waves. Unit 6 will supply limited quantities of material fairly suited for subbase, base, and surface courses. Unit 7. Calcareous beach sands Calcareous beach sands are the poorly graded, loose, fine to coarse lime sands composed of subrounded to angular fragments of coral and other marine detritus that are found along the low coastal plains and on the reef islands. The unit occurs generally as long, narrow, relatively level areas of various depths of sands interfingering with coral gravel in some places on the seaward side and with muck and peat on the marshland borders. In some places on the seaward sides the lime sand borders the sea; in other places it borders mangrove swamps. On the inland side it usually borders marshland, but in some places it fringes one of the upland clayey units. The sands are excessively drained to the water table which is from about 16 inches to 2 feet be- low the surface. This unit is soils Unit 6, Shioya loamy sands, in the Soils section. The lime beach sands are the onxy sands that can be easily Obtain- ed on Truk. The sand of this unit is rated only fair for concrete be- cause many of the sand particles contain organic matter and.many of the sand particles are more angular and weaker than the more desirable sil- ica sands; however, it probably could be used satisfactorily in con- crete for semipermanent construction. The beach sands have a good bearing capacity. Its bearing capacity and qualities as subgrade are excellent when confined, but it is unsuitable for base course and good to fair for concrete aggregate. In addition to use for village sites, the unit has been used insofar as practical for coastal roads and trails. It is believed that the former Japanese airstrips on Moen, Dublon Island, Eten, and Param were con- structed on areas occupied in part by this unit, but this could not be determined with certainty because power angers and core-drilling ma- chines were not available. However, seaward fringing exposures of the sands were found on the west-southwest end of Moan Airfield, on the southwest part of the Eten airstrip, and on the east end of the air- strip on Param. Unit 8. Deep stony clays Stony clay and bouldery talus on volcanic bedrock are mapped as Uhit 8. Approximately 95 percent of the unit is stony lean clay or clayey silt; the remainder is bouldery talus. The stony lean clay, l to 30 feet thick on volcanic bedrock, is granular, firm, slightly 16h 0" ice (0 plastic to plastic, and about 15 to 50 percent by volume residual vol- canic cobbles and boulders (pl. 23). The percentage of boulders prdba- bly increases with depth in the soil profile. This unit is Truk stony clay, soils unit 2, hilly to precipitous slope phases, in the Soils section. The bouldery talus, l to 50 feet thick on volcanic bedrock, is 50 to 90 percent volcanic rock blocks which range in size from h-inch cob- bles to 10-foot boulders. The clay fraction is granular, firm, plastic, and moderately well drained. A large proportion of the bouldery talus is mapped with the rockland (soils Unit h). The clays cover steep to very steep mountain sides, young valleys or ravine walls, and colluvial debris scattered below cliff faces. The deep stony clay is well drained. The depth to the water table is unknown but it is believed to be near the contact of the soil and the bedrock, about 20 feet below ground. The bearing capacity of the stony lean clay or clayey silt is probably good to poor (U. S. War Department, 19M}, fig. 69). The bear- ing capacity of the bouldery talus would be excellent to good if the boulders were bridged or stabilized with adequate binder material. The best sites for construction on this unit are in areas of least slope. Foundations of permanent structures require drainage facilities to dispose of upslope seepage. Unit 8 will supply unlimited quantities of earth fairly suited for fill. Large boulders along the foot of cliffs are suitable for cyclo- pean riprap rock. Smaller boulders are excellentLy suited for riprap rock and rough stone masonry and as a potential source of good crushed aggregate. Earth, about 20 feet deep over bedrock, can easily be re- moved by hand tools and power equipment. Drilling and blasting are re- quired in the bedrock. Earth slopes are stable at l 1/2zl; vegetation cover will impede erosion. Slope benching at the interface of the soil and bedrock on the uplepe side will impede earth slides. Bedrock faces are stable at 1/2zl. Interception ditches are needed on upslope sides of excavations to divert runoff. Inclosed excavations require facilities to dispose of internal seepage from the interface-zone and the bedrock-contact springs. Heavy buildings should be based on the hard bedrock where the bearing capacity is excellent. Excavation sites need drainage facili- ties during construction. Footings on the buried bedrock probably re- quire drainage safeguards against the groundwater of the interface zone. Bedrock construction materials are generally the same as unit 2. Unit 9. Deep residual clays The unit is composed of brown, reddish-brown to red, and reddish- yellow lean clay or clayey silt which range from 10 to 50 feet in thick- ness over volcanic bedrock. The soil, which is granular in the surface 165 l to 6 feet, grades to a massive structure. The soil is friable, firm, slightly plastic, and well drained. In the borrow pits, road cuts, and other places where observation was possible, the surface 10 feet of the soil profile was relatively free of boulders; however, the lower hori- zons probably contain some residual volcanic boulders. This unit is described as soils Unit 1, Truk clay. The clay has weathered on undulating to hilly knolls, on saddles, and on undulating to steep footslopes. The internal drainage is rela- tively good. Because there are no known wells in the unit, the depth to the water table is uncertain, but it is believed to be very near the contact of the soil and bedrock; the estimated depth to the water table is about 25 feet. The slopes of this unit are stable. The natural undulating to steep slopes are uniform. Even though the major part of the unit has been deforested and is now grassland, severe sheet erosion and deep gulleying are not common. Nearly vertical unprotected 10- to l2-foot-high slopes in road cuts and borrow pits excavated 10 years ago show very little evidence of slumping and raveling. On this basis, stabilization of 1:1 cut slopes less than 15 feet high is unnecessary. The bearing capacity of the unit is good to poor. Buildings and other heavy construction probably require footings on the underlying bedrock. Unit 9 will supply large amounts of easily excavated earth materi- al poorly suited for clay binder and fairly suited for fill. Excavation and foundation problems and construction materials in the bedrock underlying Unit 9 are about the same as for Unit 8 but the overlying earth is a little deeper and contains fewer boulders. Unit 10. Thin clays on hard compact lavas The surface materials in this unit, ranging from 1 to 10 feet in thickness and averaging about 3 feet, are composed of about 70 percent reddish-brown to yellowish-red, lean clay or clayey silt and 30 percent dark-brown to dark-gray fat, plastic clay. In an area near the summit of Witip6n on Mben, the soil profile has a h-inch horizon about 3 inch- es below the surface, which contains about 30 percent bauxitic irregu- larly shaped gravel-sized concretions in clay. The fat clay is granular, very firm, plastic, and somewhat poorly drained; it contains some small, seepy and marshy areas of one-fourth to one-half of an acre in size. The earth portion of this unit is de- scribed as soils Unit 2, Truk stony clay, undulating to hilly phase. The thin clay unit is developed mostly on gently leping to roll- ing plateau summits, saddles, and foothills. The unit includes a few rock outcrops and residual boulders. Where present above the bedrock, the water table, averaging about 3 feet below the surface, is at the contact of the soil and bedrock. The bearing capacity of the earth material is good to poor. Foun- dations would probably require some drainage protection. The earth of 166 this unit can be excavated by hand tools in all except a few isolated one-fourth to 2-acre areas of boulder fields which could be handled more advantageously by power equipment. The characteristics of the bedrock are the same as for Unit 1, hard compact lavas, and, except that l to 10 feet of earth must be re- moved, excavation problems are also generally the same. Drilling and blasting are required to remove the massive bedrock. Footing of heavy installations should be based on the bedrock. Bedrock construction materials are the same as Unit 1. Sizable re- serves of the hard compact lavas are in Unit 10. Unit 11. Thin clays on hard mixed lavas This engineering materials unit, thin clays on hard mixed lavas, consists of 1 to 10 feet of thin clays (the same clay soil of Unit 10) on hard mixed lavas which are the bedrock of unit 2. Unit 11 is mapped on gently sloping to rolling plateaus, saddles, and foothills. The earth portion of this unit, like that of Unit 10, can generally be excavated with hand tools. Excavation of the bedrock requires drilling and blasting in the massive bedrock. In the Jointed rock and in the breccia, blasting will facilitate rock removal. Shal- low foundations would probably require drainage facilities as the clay is somewhat poorly drained. Footings based on contact zones in the bedrock also require drainage safeguards. The earth is poorly suited for clay binder. Extensive reserves of hard.mixed lavas are in Unit 11. Unit 12. Thin clays on moderately hard lavas The areas mapped as unit 12 have 1 to 10 feet of the same clays as the clay soils of Unit 10 on moderately hard lava which is the trachyte bedrock of unit 3. landforms in Unit 12 include foothills, saddles, and gently slop- ing to rolling plateau summits. Earth excavation problems are similar to those of unit 10: hand tools are adequate except in local boulder fields. Bedrock can be ex— cavated with power equipment but some blasting would help. Foundations probably would require drainage facilities. The earth is poorly suited for clay binder. unit 12 areas contain extensive re- serves of moderately hard lavas. Unit 13. Thin limonitic gravelly clay on hard compact lavas The earth, ranging from 1 to 8 feet in depth, averages about 2.5 feet to bedrock which is the same rock as Unit 1. The surface 1 to 3 feet is 30 to 70 percent gravel-sized ferruginous concretions, the re- mainder being clayey silt. Where the thickness of the earth material is more than 3 feet, the gravelly surface horizon (pl. 25 B) is gener- ally separated from the underlying bedrock by a stratum of gravel-free, yellowish, friable, firm, slightly plastic, lean clayey silt, which is divided into from 2- to 5-inch blocks by an intricate network of seams or veins of semi-indurated limonitic material one-eighth to three- eighths of an inch wide. The earth material is soils Unit 3, Fefan soils. 167 The unit is found mostly on undulating to sloping terracelike benches and summit plateaus. It is found also on one gently sloping low coastal footslope on Moen. The depth to the water table probably varies with the thickness of the soils. locally, the water table is near the contact of the soil and the bedrock. Internal drainage seems to be moderately rapid in the gravelly zone and moderately slow in the clayey horizon. The limonitic gravel horizon of this unit is good for road metal, poorly suited for binder, and its bearing capacity good. The bedrock of Unit 13 is the same as in Unit 1, hard compact lavas. Excavation problems in the bedrock are generally the same as in Unit 1 except for l to 8 feet of earth to be removed. Rock construc- tion materials are also the same. Foundation problems in the bedrock are similar to Unit 1. Heavy installations in this unit should be based on the hard bedrock where bearing capacity is excellent. (K Unit 11L. Thin limonitic gravelly clay on hard mixed lavas The areas mapped as Unit 1h consist of l to 8 feet of limonitic soils (the same as the soils part of Unit 13) on hard mixed lavas which are the rocks of Unit 2, hard mixed lavas. landforms in this unit are generally undulating to sloping terrace- like benches and plateau summits. Except that the l to 8 feet of earth must be removed, excavation problems are the same as for Unit 2: drilling and blasting are requir- ed in the massive bedrock and will assist removal in the breccia and in the Jointed rock. Foundations, especially those based on contact zones in the bedrock, will probably require drainage facilities. Unit 15. Mangrove-swamp deposits Mangrove swamps are the shallow brackish- or salt-water swamps 7‘ ._ supporting sparse to dense mangrove vegetation. The swamp soils are r various; they range from loamy coarse and fine sands in the open sea- ward fringes to about 1|- feet of muck and peat over lime sand in the protected embayments. The swamp soils are submerged from 1 to 3 feet at high tide. lli'his unit is the same as soils Unit 8. Mangrove swamps, from small isolated shrubs to 300-acre forests, fringe parts of most of the volcanic islands; swamps of less than 5 acres grow adjacent to some of the lagoonal reefs and to a few of the barrier-reef islands. Installations on this unit require support of bearing piling or rock fill based upon the sand layer. Bearing capacity is good to un- suitable. Foundations of installations on the windward side of islands require protection against stem waves. Lime sand can be dredged by dragline from sandy parts of the k swamps. 168 «4) Unit 16. Marshland deposits The earths of the low coastal fresh-water marshes, Unit 16, are composed of various thicknesses and proportions of muck and peat. They are soils unit 5, muck and peat. 0n the seaward side, the marshland borders either calcareous beach sand (engineering Unit 7) or mangrove swamp (engineering Uhit 15), and is underlain by lime sands. On the inland side where the marshland borders the upland units, the muck and peat is underlain by a plastic clay. The bearing capacity of the muck and peat is poor to unsuitable, its water-holding capacity is extremely high, and its specific gravity is very low. Installations in this unit require support of bearing piles driven into stable materials beneath the marsh; depth to stable materials is generally unknown, but where known ranges from h to 15 feet below ground surface. Extensive fill on the unit, where the muck and peat has been dis- placed by rock and earth fill, appears to be fairly stable after a lapse of 10 years. Uhit 17. Fill Extensive areas of the coastal lowlands of Dublon Island, Moen, Eten, and Param consist of rock and earth fill. The fill surface is l to 10 feet above high-tide level. Rock fragments range from 1 inch to 2 feet across and are embedded in clay binder. locally, the fill is mostly of calcareous beach sand. The observed water table in.the fill areas is at or near sea level. Airstrips and seaplane bases located on the fill are surfaced with concrete pavement and crushed rock. Seaward margins of the fill are commonly faced with seawalls of loose stone masonry. Ellie fill can be excavated with hand tools and power equipnent. Bearing capacity is good on the earth fill and is excellent on the sound concrete. Surficial drainage of the fill ranges from generally well drained on the higher areas to marshy on some low areas. Rock and earth material of the fill is suitable for fill. Loose rock blocks in the seawalls are suitable for riprap rock and rubble masonry and are readily available. Uhit l8. Coral boulders, cobbles, and gravel Islands of the barrier reef are formed of loose calcareous depos- its of coral boulders, cobbles, gravel, and sand (map 8). The deposits range from sea level to 6 feet in elevation. Broad low ridges of coral boulder and cobble zones occur on the seaward margins of the islands; the gravel and sand are mostly in the interior and on the lagoonward sides. The coral is dark gray on the weathered surface and white on the fresh fractures. Exposed surfaces and fracture faces exhibit well- preserved cellular structures. Coral rock is porous and relatively weak and soft compared with older coral limestone. The water table of the coral islands is at or near sea level. Pools and inland fresh- water marshes are common on most reef islets. Internal drainage of the loose coral is rapid. These coarse unconsolidated coral deposits are shown on map 8. 'L’ne coral detritus can be excavated with hand tools and power equipment. Bearing capacity is good on the undisturbed material and is excellent Where the coral is stabilized. 'me boulders and cobbles are suitable for rubble masonry. Crushed coral and gravel are both good for macadam and base course and are fairly suitable for concrete aggregate if washed. 170 Pits and Quarries by Harold G. May In the Truk Islands, only four sizable quarries were found where extensive amounts of bedrock have been excavated. These are described in table 22 and located on the engineering materials maps (maps 30 through 36). Three of the quarries are on Moen and one is on Eten. Only quarries 1 and 3 on Moen are in current use (1955). All four quarries were formerly used by the Japanese. On Dublon Island, uman, and Param, the Japanese collected field boulders for crushing into ag- gregate. Stockpiles of the boulders are still present at abandoned crusher plants on these islands. There are several abandoned Japanese borrow pits at the base of coastal slopes on the west and south sides of Dublon Island. The Dublon pits are cut level with the coastal flats into the slope and range from 150 to 250 feet across and are up to 50 feet deep on the up- slope sides. Three similar borrow pits are cut into the south slopes of Param and a long bench is cut in soft rock and earth along the mar- gin of the airfield. At Eten, the Japanese benched the whole north slepe of the island ridge, where rock and earth were excavated to fill in the airfield site. Exposures of engineering materials Units 1 and 2, shown on the maps (maps 30 through 36) are all potential quarry sites of hard lava. The best sources of hard compact lava are in Units l, 10, and 13. Exposures of Unit 1 are areas of bare bedrock, but there is shallow overburden on the bedrock of Units 10 and 13. There are extensive earth exposures in Units 8 and 9 on most of the major volcanic islands which will supply ample amounts of earth suitable for fill. Borrow pits within Unit 9 as developed on Dublon Island, Eten, Moen, and Param are located on the gently sloping areas of the islands. 171 Quarry No. Engineering Materials Unit Description of in-place Material Jointing and Fracturing Texture and Uniformity Weathering Overburden Fragmentation and Crushing Characteristics TErrain and Drainage Conditions 1 Hard compact lava 1 Hard compact lava 1 Hard compact lava 2 Hard mixed lavas Vertical to inclined polygonal jointing; platy fracture about normal to length of joint blocks. Joint blocks 0.5 to 2.5 feet across joint and l to h feet long. Biggest joints at bottom of face. Vertical jointing; polygonal joint blocks 0.5 to 2.5 feet across and.up to 8 feet long. Horizontally inclined or variable dipping polygonal joint blocks 0.5 to 0.8 feet across and 1.5 to 2.5 feet long. Vertical polygonal jointing: joint blocks 0.7 to 2.0 feet across. Generally very fine grained. Porphyritic; fine-grained groundmass. Generally very fine grained. Porphyritic; fine- grained ground- mass. Amygdaloidal zone at top of lava flow about 50 feet above floor of quarry cut. Negligible except at soil contact. Thin coating of lflmonitic clay on joint faces. Negligible except at soil contact. Thin coating of limonitic clay on joint faces. Negligible. Joint faces thinly coated with limonitic clay. Negligible except at soil contact. l to 10 feet of residual clay soil. 1 to 6 feet of residual clay soil. None at cliff face. Thin soil upslope. Thin at face; probably deepens to 20 or 30 feet deep within 150 feet to east. Rock breaks loose from face as joint blocks 1 to h feet long. Crushed rock generally is long wedgelike chips with some fines of rock dust and clay. Blasting would facilitate excavation. General high recovery rate. Rock breaks loose from face as joint blocks. Blasting would expedite excavation. Rock breaks into angular blocks. Rock is hard and strong. General high recovery rate. Rock breaks loose from face as joint blocks. Blasting would expedite excavation. Rock is hard and strong. General high recovery rate. Rock breaks loose as joint blocks 2 to 4 feet long. Blasting would expedite excavation. Rock breaks into angular fragments. The rock is hard and strong. Limited recovery rate. Cliff face at foot of north coastal slope of Mben. Cliff about 50 feet high and several hundred feet long. Spring Zone at base of lava. Quarry drains seaward along pit floor. Steep rocky bluff along south coastal slope of Mben about 100 feet high and several hundred feet long. Drains across floor and down slope. Steep rocky bluff on north footslope of Mount Teroken (Chukumong). Cliff at quarry site is 50 to 75 feet high, fades out about 500 feet eastward. Small intermittent stream cascades over cliff about hOO feet eastward. Pit drains across floor and down slope. Western nose of an isolated elongate hill projecting into coastal flats (fill). Quarry rock overlies gently south-dipping conglomerate: contact is at floor of quarry cut. Water table is about 0 to 10 feet below quarry floor at sea level or at contact with conglomerate. lace Material Weathering Overburden Fragmentation and Crushing Characteristics Terrain and Drainage Conditions Quarry Size and Development Access Estimated Reserves ry fine *ry fine fine- mnd- :daloidal > of lava 50 feet ' of Negligible except at soil contact. Thin coating of limonitic clay on joint faces. Negligible except at soil contact. Thin coating of limonitic clay on joint faces. Negligible. Joint faces thinly coated with limonitic clay. Negligible except at soil contact. l to 10 feet of residual clay soil. 1 to 6 feet of residual clay soil. None at cliff face. Thin soil upslope. Thin at face; probably deepens to 20 or 30 feet deep within 150 feet to east. Rock breaks loose from face as joint blocks 1 to h feet long. Crushed rock generally is long wedgelike chips with some fines of rock dust and clay. Blasting would facilitate excavation. General high recovery rate. Rock breaks loose from face as joint blocks. Blasting would expedite excavation. Rock breaks into angular blocks. Rock is hard and strong. General high recovery rate. Rock breaks loose from face as joint blocks. Blasting would expedite excavation. Rock is hard and strong. General high recovery rate. Rock breaks loose as joint blocks 2 to 4 feet long. Blasting would expedite excavation. Rock breaks into angular fragments. The rock is hard and strong. Limited recovery rate. Cliff face at foot of north coastal lepe of Mben. Cliff about 50 feet high and several hundred feet long. Spring Zone at base of lava. Quarry drains seaward along pit floor. Steep rocky bluff along south coastal slope of Moen about 100 feet high and several hundred feet long. Drains across floor and down slope. Steep rocky bluff on north footslope of Mbunt Teroken (Chukumong). Cliff at quarry site is 50 to 75 feet high, fades out about 500 feet eastward. Small intermittent stream cascades over cliff about #00 feet eastward. Pit drains across floor and down slope. Western nose of an isolated elongate hill projecting into coastal flats (fill). Quarry rock overlies gently south-dipping conglomerate: contact is at floor of quarry cut. Water table is about 0 to 10 feet below quarry floor at sea level or at contact with conglomerate. Quarry cut back level about 50 to 75 feet and about 300 feet wide into face of cliff. Face is no to 55 feet high. Small operative crusher at quarry. Two adjacent quarry cuts into top 30 feet of bluff. Cuts each about 150 feet long and cut level into bluff about ho to 50 feet northward. Floors of cuts about 50 feet above adjacent coastal flat surface (fill). Quarry cut about 150 feet long, cut level about 50 feet into bluff. Face is 20 to 60 feet high. Abandoned Japanese quarry recently (1955) reactivated by Trust Territory Public Works Dept. Quarry cut level with coastal flats and 150 feet wide across full width of nose. Face at maximum height is about 50 feet. level pit floor 150 feet to two-lane gravel highway. Paved runway of aban- doned airfield along foot of bluff about 100 to 150 feet south. Footpath from runway to quarry cuts. About 75 feet across floor of pit to single-lane gravel road. Rough single-lane rock and earth trail along SW edge of quarry cut. About l/h million yards, southward 300 feet behind present face; more along cliff to east of quarry. About l/lO million yards beneath present quarry cuts to level,of coastal flat. Large reserves in adjacent rocky bluff across valley to eastward: > 1 million yards. Reserves in slope and westward along face are probably more than l/h million yards. Probably< 1/10 million yards at the level of present cut; to the east only. Concrete base cou road met Abandoned probably aggregat course m Probable concrete Abandoned probably aggregat course m Table 22. Quarries, Truk Islands. Terrain and Drainage Conditions Quarry Size and Developnent Access Estimated Reserves Use Remarks very Cliff face at foot of north coastal slope of Moen. Cliff about 50 feet high and several hundred feet long. Spring Zone at base of lava. Quarry drains seaward along pit floor. Steep rocky bluff along south coastal slope of Mben about 100 feet high and several hundred feet long. Drains across floor and down slope. Steep rocky bluff on north footslope of Mount Teroken (Chukumong). Cliff at quarry site is 50 to 75 feet high, fades out about 500 feet eastward. Small intermittent stream cascades over cliff about hOO feet eastward. Pit drains across floor and down slope. Western nose of an isolated elongate hill projecting into coastal flats (fill). Quarry rock overlies gently south-dipping conglomerate: contact is at floor of quarry cut. Water table is about 0 to 10 feet below quarry floor at sea level or at contact with conglomerate. Quarry cut back level about 50 to 75 feet and about 300 feet wide into face of cliff. Face is ho to 55 feet high. Small operative crusher at quarry. Two adjacent quarry cuts into top 30 feet of bluff. Cuts each about 150 feet long and cut level into bluff about 40 to 50 feet northward. Floors of cuts about 50 feet above adjacent coastal flat surface (fill). Quarry out about 150 feet long, cut level about 50 feet into bluff. Face is 20 to 60 feet high. Abandoned Japanese quarry recently (1955) reactivated by Trust Territory Public Works Dept. Quarry cut level with coastal flats and 150 feet wide across full width of nose. Face at maximum height is about 50 feet. level pit floor 150 feet to two-lane gravel highway. Paved runway of aban- doned airfield along foot of bluff about 100 to 150 feet south. Footpath from runway to quarry cuts. About 75 feet across floor of pit to single-lane gravel road. Rough single-lane rock and earth trail along SW edge of quarry cut. About 1/1; million yards, southward 300 feet behind present face; more along cliff to east of quarry. About l/lO million yards beneath present quarry cuts to level,of coastal flat. Large reserves in adjacent rocky bluff across valley to eastward; :> 1 million yards. Reserves in slope and westward along face are probably more than l/h million yards. Probably< l/lo million yards at the level of present cut; to the east only. Concrete aggregate, base course, and road metal. Abandoned. Japanese probably used aggregate for base course mostly. Probable use: concrete aggregate. Abandoned. Japanese probably used aggregate for base course mostly. Boulder conglomerate underlies lava of face; contact at spring zone about 10 feet above sea level. Aggregate probably more suitable for base course than concrete because of is long wedgelike shapes. Joint blocks are suitable for rough stone masonry. Quarry location: along coastal road on northwest Moen; near Moen Airfield. These quarry cuts will supply aggregate suita— ble for concrete, base course, and wearing course. Quarry location: southwest Moen. Proposed construction at this site may preclude further development of quarry within the near future. Quarry location: central west Moen. This quarry will supply a limited amount of selected aggregate suitable for concrete aggregate and wearing course. Pit-run material is suitable, if crushed, for base course. Quarry location: west end of ridge at Eten. 173 C Roads and Airfields by Harold G. May General statement Road obnstruction is generally difficult in the upland parts of the volcanic islands; cut and fill, clearing of moderate to dense for- ests, drainage facilities, bridging, and, in some places, blasting and tunneling are required. Slopes are hilly to steep and precipitous rock cliffs are common. On the coastal lowlands, areas of fill and sandy flats are suitable for road construction. Clearing of scattered coco- nut trees on the sand and of grass and brush on the fill is necessary. The mangrove swamps and freshawater marshes are poorly suited for road construction; rock fill and raised roadbeds through these areas are re- quired. Clearing in the mangrove swamps is also required. Scattered, small, sparsely tree-covered and grassy upland areas are fairly suita- ble for road construction. They occur on Summit plateaus and gently sloping hillsides. The Japanese built roads on the coastal lowlands around the high volcanic islands and a few roads on the larger reef islands. There were branching roads across some of the islands and into the interior highlands. Except for stretches of double-lane paved roads on Dublon Island, the roads were narrow and are now overgrown with jungle and washed out in many places (1955). The islanders have kept many of the roads open, but generally only as footpaths between villages. Coastal roads on some of the islands can be easily repaired; upland roads, for the most part, have sharp curves and excessive grades. Probably it would be easier to build new roads than to rebuild the old ones. There are no areas well suited for airbase construction in the Truk Islands. Coastal areas of sandy flats and fill are suitable in terms of gradients and subgrade conditions but are too small. Upland areas are generally steep and forested. An area on northwest Moen is large enough for a l0,000-foot airfield. By using the fill, marsh, and adjacent footslopes an airbase could be built; it would require exten- sive drainage and cut and fill. Four airfields, two on Mben and one each on Eten and Param, were built by the Japanese. The north field on Moen, Moen Airfield, is now in use. It is in good condition and can be extended a short distance at both ends. C-h7's, B-29's, and C-5h's have landed on this strip. The other three airfields, which are abandoned, can be easily repaired but cannot be extended far beyond their present lengths. Ample hard rock reserves are available near each airfield except on Param. Fill areas, the sandy flats, and the grassy upland flats are suit- able for heliport construction. Some clearing of scattered trees and drainage may be required. The rest of the terrain would require clear- ing and leveling and has poor access. Construction materials are generally available. Quartz sand for portland cement concrete does not occur in the Truk Islands but suita- ble substitutes are available. 175 Japanese roads Roads once extended along the coastal margins of the large volcan— ic islands and on some of the reef islands. Branch roads extended into the interior and across the islands (pl. 58). The roads are mostly single-lane highways, cart tracks, and footpaths. Curves are moderate to very sharp, tangents are of various lengths, and gradients are level in the lowlands and are moderate to very steep in the uplands. Coastal roads were constructed on sandy flats, fill, along footslopes, and a- cross the mangrove swamps on low causeways of rubble masonry and fill. Roads on the slopes had side drains and cross drains. Single-lane roads were 9 to 10 feet wide and commonly were surfaced with rock and earth. Most upland roads are so steep and curves are so sharp that it is more practical to build new roads than to improve old roads. Mbst of the Japanese roads are partially overgrown, locally washed out, and in many places impassable to motor vehicles (1955). Natives keep most coastal roads cleared for footpaths (pls. 59 A, 60 B, and 61 B). Some of the roads are traversable by jeep for short distances. The best Japanese roads are on Dublon Island where there are narrow paved roads (pl. 59 B) and double-lane roads surfaced with crushed rock or earth (pls. 10 B, 60 A, and 61 A). Mbst roads on Dublon Island can be easily repaired. Elsewhere in the islands extensive new road con- struction would be required wherever military development were planned. Short stretches of double-lane gravel highways connect the Trust Terri- tories administration areas on Moen (pl. 62). Airfields The Japanese built four airfields in the Truk Islands: two on Mben, one on Eten, and one on Param. All the airfields except Moen Airfield on the northwest part of Mben are abandoned, overgrown, and in poor condition (1955). Runways are generally oriented east-west and approach is over the lagoon. The runway at Mben Airfield is about 3,400 feet long, 200 feet wide, and is h to 5 feet above low-tide level. The runway is surfaced with crushed coral and it is smooth and in good condition. The landing strip is drained by open ditches along the shoulders, but much of the adjacent terrain is marshy. Former taxiways and hardstandings are a- bandoned and overgrown and are not connected with the present airstrip. Both ends of the runway can be extended a short distance onto adjacent shallow fringing reefs. C-h7’s, B-29's, and C-5h's have landed on this airfield. Access is by a double-lane gravel highway. The airfield on southwest Mben is abandoned. The runway is about 3,300 feet long, 130 feet wide, and is 3 to h feet above low-tide level. It is paved with concrete which is now badly cracked and broken. Paved taxiways at the west end of the airfield are in the same condition as the runway. In the eastern part, the runway has sagged 3 to 6 inches below the water table, and pools of standing water are common in the central part. Mbst of the airstrip and taxiways are overgrown with grass, weeds, and scattered stands of brush. Extensive repairs are needed before this field can be used. Abandoned concrete seaplane ramps at the west end of the airstrip are in fair condition. The west end of the runway can be extended 100 to 200 yards onto the adjacent shallow fringing reef, and at the eastern end it can be extended 600 to 700 yards into the mangrove swamp. Access is by a winding jeep trail. 176 (O A. Former Japanese path, Ulalu. Looking west along westward continuation of road in photo below. 1954-55. a. v., I WK?» 9 ’v _ 2 * up: 6%“? Mr ‘ :4 ‘3. “"r B. Former Japanese road, east Ulalu. Looking west . along road cut through nepheline basalt. The road is 8 to 10 feet wide and surfaced with crushed rock and clay binder . 1951+-55 . Plate 58 Plate 59 A. Former Japanese coastal road, west Tsis. The roadbed is 12 feet wide and surfaced with crushed rock. Road is now used exclusively as a trail. December 1954. B. Former Japanese road, southeast Dublon Island. The road is about 18 feet wide and paved with bitumen con- crete. 195u-55. A. Former Japanese road on northeastern Dublon Island. Now overgrown with grass, the roadbed is 25 to 30 feet wide and paved with crushed rock. 195h—55. B. Footbridge in coastal road, southeast Dublon Island. looking east along road at crossing of ditch which drains fill on the north side of the southeastern peninsula. 1954-55- Plate 60 Q A. Former main Japanese coastal road, south Dublon Island. The roadbed is 15 feet wide and surfaced with crushed rock; present width is 6 to 8 feet. View west. December l95h. B. Coastal road, east Uman. The road consists of coral sand over coral blocks and crushed rock. Despite small washouts, such as shown here, the road is travers- able by jeep. December l95h. Plate 61 American coastal road, west Moen. The road is about 25 feet wide and surfaced with calcareous beach sand on a base of crushed rock. l95h-55. Plate 62 A. Young coconut trees on the northeast end of abandoned airfield, Param. 1954-55. B. Former Japanese airstrip, Param. Concrete pavement is visible in native footpath at right; elsewhere the concrete surface of the runway is overgrown with vegetation. l95h-55. Plate 63 [I A. Breached seawall, northeast end of former air- field, Param. View southeast. Fill has been washed out in foreground. 1954-55. jw B. Unfinished extension of former airfield, Param. View north. 195u—55. Plate 64 The airfield at Eten is abandoned (pl. 1). The runway is about 3,300 feet long, 130 feet wide, and is 5 to 10 feet above low-tide level. The runway is paved with concrete which is now badly cracked and broken. Paved hardstandings and warm-up aprons are in the same general condition as the runway. The runway itself is dry, but adja- cent level areas south of it are marshy. Much of the runway and hard- standings are overgrown with grass and weeds and scattered stands of young coconut trees. The runway cannot be extended very far because the fringing reefs at either end shelve into deep water. Access is by pier for small craft. Extensive repairs are needed before this field can be used. The airfield at Param is abandoned (pl. 2). The runway is about a mile long, 300 feet wide, and is 3 to 5 feet above low-tide level. A stretch of runway h,OOO feet long and 130 feet wide is paved with con- crete which is now cracked and broken; the rest of the runway is sur- faced with crushed rock and earth. Portions of the paved taxiways south of the airstrip have sagged a few inches below the water table as have small areas of the eastern part of the runway. Both ends of the runway can be extended 100 to 200 yards onto shallow fringing reefs. Much of the runway and the taxiways are overgrown with grass and vines and have brush and scattered stands of bearing coconut trees large e- nough to be a clearing problem. Sizable groves of bearing coconuts are planted on both ends of the runway (pl. 63). Extensive filling, re- pairs, and drainage are required before this airfield can be used (pl. 6%). Access is by trail and by piers for small craft. Ample reserves of rock and earth materials suitable for fill are adjacent to each airfield. Bedrock suitable for crushed aggregate is available near both airfields on Moen and the one at Eten, but good ledge rock in place has not been found anywhere on Param. Unit 1. Dry lowlands Areas mapped as Unit 1 are dry level coastal lowlands (maps 37 through #3). About one-half of the unit is irregular sandy flats along the coasts, the rest is rock and earth fill and small coral islands of the barrier reef and lagoon. Runways, warm-up aprons, and some taxi— ways of existing airfields on the fill are paved with concrete. Eleva- tions of the unit are from 1 to 10 feet above sea level. The beach sand is well to poorly graded lime sand; the fill is a mixture of bro- ken rock and earth. Surface drainage is rapid on the sand but runoff ponds temporarily in low areas of the fill. The vegetation on sand is principally stands of coconut pahns. Vegetation on the fill, including much of the paved areas, is mostly grass, weeds, and some scattered stands of coconuts and brush. The subgrade of the barrier-reef islands (in Unit 1) is loose coral boulders, cobbles, gravel, and lime sand; subgrade of the coral islands of the lagoon is mostly calcareous sand. Elevations of the is- lands are from 3 to 9 feet above low-tide level. Vegetation consists of coconut groves (pl. 9 A), some breadfruit, scrub growth, natural jungle, and some grass and vines. Marshes or small mangrove swamps or both are present in the interior of most of the larger reef islands. Drainage is rapid. The reef islands are shown on map 8. Road construction: The subgrade and terrain of Unit 1 are suitable in most places for military road construction. The best road locations 177 are across the fill and along the sandy flats. New roads can have easy curves and tangents of diverse lengths and be level. Only the roads across the fill require drainage facilities. Bearing capacity on the subgrade is good to fair. Some fill is required in low places. Clear- ing and grubbing of vegetation is necessary on the sandy areas. Small streams and marsh outlets require bridging. Rock and earth materials of the fill and the sand are suitable for fill. On the high islands, bedrock in footslopes of adjacent mountains is generally suitable for aggregate. Coral boulders and cobbles are a source of aggregate on the barrier-reef islands. Airbase construction: No area of the unit is large enough for a major airbase. Runways of the four existent airfields in this unit are too short for fast heavy military planes. There is no room adjacent to present airfields for constructing adequate diSpersal and service areas. A major airbase could be constructed on Moen by using both wet and dry lowlands and adjacent footslopes of the uplands. Extensive cut and fill would be required and considerable drainage would be needed. Ex— posed bedrock in adjacent bluffs is suitable for aggregate, riprap rock, and masonry. Heliport construction: Clear paved areas of the unit provide existing heliport sites. Most other areas of the unit are suitable for heliport construction but require some clearing and grubbing of vegetation. Unit 2. Upland flats Areas mapped as Unit 2 are level to gently sloping upland terrain on the slopes, plateaus, and crests of the highlands. The subgrade is mostly deep clay and some rockland. The land ranges from level to 5:1 slopes l/. Scattered stands of coconut and breadfruit, scrub growth, and sizable areas of grassland are common. Drainage is channeled in small gullies and ravines. The unit occurs as many small scattered areas and a few sizable areas on plateaus of Moen, Fefan, T01, and Ulalu. Road construction: Both the subgrade and terrain conditions of the unit are suitable for road.construction. Bearing capacity of the sub— grade is excellent to fair. The best road locations are along the foot— slopes and across the plateaus and divides. New roads will have easy to sharp curves, tangents of various lengths, and gentle gradients. Cut and fill requirements are moderate. Some clearing, blasting, and bridging is required. Side drains and culverts of large capacity are needed in most places to prevent flooding the roadbed. Earth of the unit is suitable for fill. Most bedrock in rocky lands is suitable for aggregate. Good hard bedrock is rare or absent on Param.and Fala— beguets. Airbase construction: No area is large enough for a major airbase. Heliport construction: Grassy level areas on plateaus and crests are the best heliport sites in the unit. Broad flats with trees or scrub growth on plateaus, footslopes, and crests are suitable sites after the 17 In this chapter, gradient is expressed as ratio of horizontal to vertical. 178 vegetation has been cleared. Unit 3. Moderate to steep uplands Broad extensive slopes ranging from about 5:1 to l l/2:l in gradi- ent are mapped as Unit 3. The slopes are broken by isolated escarp- ments, gullies, and ravines. Drainage is channeled mostly in deep ra— vines. The subgrade of the unit is mostly deep clay and some boulder talus. The vegetation consists of scattered stands of natural forest, coconuts, and breadfruit; scrub growth; and extensive areas of sword- grass, short grasses, and vines. Road construction: The terrain is moderately suitable for road con- struction; the subgrade is suitable. Bearing capacity on the clay sub- grade is fair. The best road locations are diagonally upslope, and across the divides. New roads will have moderate to sharp curves, tan- gents of various lengths, and generally excessive gradients. Extensive sidehill cuts and fill will be required. Cut and fill requirements are about equal. Roads located across long steep slopes will require large side drains, upslope diversion ditches, and cross drains with large openings to prevent flooding and erosion of the roadbed during heavy rainstorms. Earth of the unit is suitable for fill and most bedrock of the scarps is suitable for base course, macadam, and concrete aggregate. Good bedrock is scarce on Param and Fala-beguets. Airbase construction: Unsuitable. Heliport construction: Unsuitable. Unit A. Steep to precipitous uplands Areas mapped as Unit A are mostly broken or long sinuous rocky escarpments with individual cliffs ranging from 25 to 150 feet in height. Steep slopes and bluffs developed on earth are common. Slopes range from 1 l/2zl to vertical. Drainage is mostly surface runoff. The subgrade of the escarpments is bedrock and boulder talus, elsewhere the subgrade is deep clay. Vegetation is largely natural forest with trees ranging from 25 to 65 feet in height and measuring 1/2 to 2 feet across the trunk. Scrub growth and underbrush are common. Road construction: The uplands are poorly suited for road construction. Bearing capacity on the bedrock is excellent and generally fair on the clay subgrade. The best road locations are along the foot of escarp- ments and along crests. New roads will have sharp curves and switch- backs, tangents of short lengths, and excessive gradients. Extensive cut and fill, clearing, and blasting will be required and tunnels will probably be necessary. Roadbeds will require extensive drainage to prevent flooding and erosion. Most bedrock in the escarpments is suit- able for base course, riprap rock, and aggregate. Earth in the steep slopes and bluffs is suitable for fill and binder. Airbase construction: Unsuitable. Heliport construction: Unsuitable. 179 Unit 5. wet lowlands The wet lowlands are the marshes and mangrove swamps of the coast- al lowlands around the high islands. Mangrove-swamp deposits are sub- merged l to 3 feet in sea water. Small shallow ponds of fresh water are common in the marshes. The submerged subgrade of the mangrove swamps is mostly calcareous sand with scattered patches of muck. The saturated subgrade of the marshes is mostly muck and peat. Locally, where the muck and subsoil interface ranges from h to 15 feet below the water table, the muck is on subsoil.of clay or calcareous sand. The water-table level in the marshes is from at sea level to 2 feet above sea level. Vegetation of the mangrove swamps is dense to scattered thickets of mangrove, and in the marshes there are dense stands of tall reed grass and scattered clumps of scrub growth. Road construction: The subgrade of the swamps and marshes is generally unsuitable for road construction. New roads will require raised road- beds of rock fill across the mangrove swamps, and, in the marshes, the muck must be displaced with rock fill for lasting stability of the road- bed. The best road locations in the unit apparently are along stretch- es of shallow sandy bottom in the mangrove swamps. Extensive subsur- face exploration should be made before new road locations are estab- lished. New roads will have easy to sharp curves and medium to long tangents and be level. Raised roadbeds, exposed to waves, will require riprap protection on the seaward face. New roads will require piling support where the bottom is too deep for fill. Japanese-built cause- ways across the swamps are localLy in fair condition but in other places are breached and partly dismantled (pl. 10 A). Rock and earth for fill is commonly available in adjacent bluffs. Airbase construction: Unsuitable. Heliport construction: Unsuitable. 180 e. underground Installations by Elmer D. Patterson General statement In the Truk Islands, most of the volcanic islands have conditions well suited for the construction of either tunnel-type or bunker-type underground installations. On the high volcanic islands tunnel-type excavations with adequate cover, roof support, water supply, drainage, and camouflage can be constructed. Access to sites is somewhat limited by the need for road building or repair, overwater transportation, and clearing of tough vegetation. Fresh water, rock, and coral sand for constructing bunker-type and lining tunnel-type installations are gen- erally available. Timber is available in large quantity but is poor quality, being mostly breadfruit and coconut trees. No tunnel-type installations and only the shallowest of bunker-type excavations would be feasible on the low coral islands of the lagoon and reef. Classification The suitability of the terrain for underground excavations is based primarily on slope and on characteristics of the soil and bedrock, upon which depend adequacy of cover, type of entry, workability, and support required (table 23). Localities most favorable for tunnel-type excavation are designated on the maps by circled numbers and specific data about these sites are also on maps AA through 50. At these sites, 100 feet of cover can be obtained by horizontal entries from 100 to 300 feet long, and rooms with 60,000 square feet or more of floor space are possible. A prime consideration in bunker-type construction is the depth and character of the soil overburden. No deep drillings were made to de- termine actual depths of the soil and estimates are based on observa- tions at cliffs, gullies, and existing caves. Indicated depths to 50 feet are probably accurate and locally depths up to 80 feet are known to occur. Many sites are available for the construction of small bunk— er-type installation but for those requiring floor spaces as great as 20,000 square feet or depths as much as 80 feet sites should be chosen only after exploratory drilling. Problems of drainage vary widely in all areas where either tunnel- type or bunker-type construction is feasible. In the areas considered unfeasible for either type of construction, the major reason is poor drainage. The depth to the water table varies widely. At many cave sites there are only a few feet of soil cover over bedrock and there is commonly no seepage of ground water through the cave roof. The auto- breccias are commonly easy rock to excavate and, where located under layers of hard massive rock, are well suited for adits. However, in several places they are water bearers and special provision for drain- age would be required. Drainage problems, particularly in bunker-type installations at low elevation, may vary seasonally for there is a gen- eral rise in the water-table level during the period of greater precip- itation, April through December. The maps show seven units of suitability for the construction of 181 BQT Table 23. Suitability for underground installations units, Truk Islands Unit 1 2 3 1+ 5 6 7 Suitability for Excellent Good Fair Poor Pbor Poor unsuitable tunnel types Suitability for Unsuitable Poor Poor Poor Good Excellent Unsuitable bunker types Slopes Over 65%; includes most Less than 65%; includes level land except tidal flats Tidal flats and cliffs. and coastal lowlands. coastal lowlands. Soils From 0 to 30 feet thick; From 0 to 10 feet thick;, From 10 to 80 feet thick; Beaches, swamps, bare rock on cliff faces; stony clay, gravelly stony clays and bouldery marshes, and deep soil at foot of cliffs. concretions of limonite, talus. lowland alluvial and bare rock. soils. Rock Conditions Good to Fair * Fair to Poor ** Good to Fair Fair to Poor Good to Fair Fair to Peor n.a. * Good to Fair: ** Fair to Poor: Includes both mappable rock units and units of the undivided series where conditions are known Excavations in this rock can probably proceed with a minimum of roof supports and concrete lining. to be favorable. Includes rock which is known to be fractured, weathered, or wet; and rocks of the undivided series about which little is known. roof supports, concrete linings, and other safety devices. Excavations in this unit will probably be difficult and will require :1 / underground installations. Conditions in six of them are variously suitable for either tunnel type or bunker type. One unit represents areas where conditions are such that no major underground installation of either type is possible. Table 23 indicates the slope, soil, and rock conditions upon which the units are determined. Most areas where the slope is over 65 percent are represented on the soils maps (maps 9 through 15) as Unit 2F and those with slopes less than 65 percent are included in other soils units. In this section three groups of soils are distinguished, (l) stony clays, from l to 30 feet thick, generally shallowest on steep slopes and deepest at bases of cliffs, (2) stony clays and gravelly concre- tions of limonite, from 1 to 10 feet deep, and (3) stony clays and bouldery talus, 10 to 50 feet thick. Bedrock is divided into two categories on the basis of excavation suitability: (1) Good to Fair. Good includes massive rock formations which present no particular problems of workability, will stand well without extensive shoring and bracing, and are generally well drained. They can be excavated with a minimum danger of rock fall and are rela- tively unweathered. They may be poLygonally jointed but are a homoge- neous mass. Fair rock may be considerably weathered but not enough to require extensive bracing. Drainage may be a problem, particularly in the wet season. (2) Fair to Poor. Fair rock is here the same as in the first category. Poor rock includes all formations which for any reason would present unusual problems of workability, drainage, col- lapse in excavating, or shoring and bracing. Poor rock is generally deeply weathered fractured rock or discontinuous lava flows less than 5 feet thick which may contain numerous seeps or springs. Underground installations units Uhit 1: Areas mapped as Unit 1 are excellently suited for the con— struction of tunnel-type installations but are generally unsuited for bunker types. Short entries at the base of massive rock cliffs would reach 100 feet or more of cover. Tunneling could be accomplished with a minimum danger of collapse and little need for extensive shoring and bracing. Drainage is easily accomplished. Because many of the areas are at high elevation, access may be difficult and new roads required. Bunker-type installations are not feasible in this unit area because of steep slopes and generally shallow overburden. This unit, mostly the individual lava flows and beds of pyroclastic rocks shown on the geol- ogy maps, is confined generally to cliffs more than 50 feet high. Unit 2: In areas mapped as Unit 2, suitability is good for the con- struction of tunnel—type installations but poor for bunker type. Ade- quate cover can be reached with short horizontal entries. Rocks may be weathered and fractured and may require shoring and bracing; drainage would be a problem in some of the rocks known to be water bearers. Slopes are greater than 65 percent and soils are generally no more than 10 feet deep so that bunker—type installations would be difficult to construct. Locally, however, accumulations of soil and rock detritus up to 30 feet thick are deep enough for small bunker-type installations. Drainage near the surface is generally good but water seepages commonly occur at the contact between the bedrock and the overburden. Access to most areas of Unit 2 is poor and new roads or extensive repair of old roads would be necessary. 183 The individual rock thicknesses are various. The unit coincides gener- ally with the undivided lavas and pyroclastic rocks shown on the geo- logic maps. Unit 3: Areas mapped as Unit 3 have fair suitability for the construc- tion of tunnel-type installations but poor for bunker type. Slopes are less than 65 percent which results in the need for long horizontal en- tries or vertical shafts. Rock conditions however, are well suited to tunneling operations. Access ranges from good in low areas near exist- ing roads to very poor atop lava flows at high elevations. Slopes are less than 65 percent but soils, only 1 to 10 feet thick, are too shal- low for most bunker-type installations. Unit h: In areas mapped as Unit A suitability for construction of both tunnel-type and bunker-type installations is generally poor. Rock con- ditions are fair to poor and tunneling requires considerable shering, bracing, and protection against rock falls. Long horizontal entries or vertical shafts would be required to reach adequate cover. Slopes are less than 65 percent but soils, only 1 to 10 feet thick, are too shal- low for most bunker—type installations. Detailed checking would be re- quired before suitable sites for either tunnel type or bunker type could be chosen. Unit 5: Areas mapped as Unit 5 are poorly suited for construction of tunnel-type installations but well suited for bunker type. Although rock conditions are good to fair for tunneling, a thick soil overburden and slopes of less than 65 percent would.make initial tunneling diffi- cult. Soil depths and slopes are suited for bunker-type installations. Special problems of drainage may exist although drainage is generalLy good. Access is good to fair. Unit 6: Areas mapped as Unit 6 are poorly suited for tunnel-type exca— vations but generally excellently suited for bunker type. Gentle slopes, thick overburden, and only fair to poor rock conditions make tunneling operations difficult. Many excellent sites for bunker-type installation can be easily located and locally those requiring 80 feet of soil depth could be con- structed. Drainage is good in upland areas but locally poor on lower slopes. This is the largest unit and access ranges from very good to very poor. Unit 7: All areas mapped as Unit 7 are considered unsuited for either tunnel-type or bunker-type installations. The primary factor is poor drainage as all these areas are at low elevation where the water table is at or near the surface. Mangrove swamps are tidally flooded; many soils are mucky and unstable. Very shallow hasty fortifications could be dug in the drier beach deposits, fill, and farmlands. Bunker-type installations A.majority of the upland areas of the Truk Islands are well suited for the construction of small bunker-type installations, although there are only a few localities suitable for bunker types requiring soils deeper than 50 feet. ' The areas in the Truk Islands most suitable for bunker—type con- struction are mapped as Units 5 and 6. The soil overburden, generally 18h from 10 to 50 feet thick and locally as much as 80 feet thick, is stony clay and clay. Although areas mapped as unit 2 are generally poor for bunker types because of steep slopes and thin soils, some of the low- level slopes have as much as 30 feet of stony clay soil, and boulder talus occurs at the foot of the steeper slopes and cliffs. Areas mapped as Units 3 and,h are poorly suited for bunker-type construction because of shallow soils; however very shallow excavations, such as foxholes and partially underground bunker-type installations, may be possible where the soils are from 5 to 10 feet thick. The rock cliffs of Unit 1 and the low poorly drained coastal areas of Unit 7 are un- suitable for bunker-type construction with the possible exception of hasty fortifications on some beaches. From an examination of numerous Japanese excavations cut into deep soil and an examination of natural slopes, it is believed that in most cases the earth will stand in #5 degree slopes. Some vertical walls up to 15 feet high occur. No running, squeezing, or swelling ground has been observed in Japanese tunnels, but ground water may be encountered at the contact of earth and hard rock or issuing from the bedrock. Tunnel-type installations Existing caves: Japanese caves dug during WOrld War II provide most of the information about tunneling characteristics. Nearly all caves cut in hard rock are in good condition; many caves cut in somewhat weather- ed bedrock are also in good condition; and many caves cut in soil are partly collapsed or completely caved (1955). Caves excavated in ba— salts and andesites with columnar jointing are particularly well pre- served; there are only a few places where blocks have fallen. Caves in the brecciated bottoms and tops of lava flows and in conglomerates and breccias are commonly wet, especially those at low elevations, but some are dry. Some caves have standing water but this may be due to accumu- lated rainwater which does not drain. Problems of tunneling operations: Earth and soft rock can be excavated with hand tools, and in some cases the joint columns of the hard rock can be removed by prying with crowbars, but most Japanese excavation was done with power drills and explosives (U. S. Navy Department, CINCPAC —CINCPOA, 19%). Faulting is negligible. Except for small slippages in earth and pyroclastic breccias, only two faults were large enough to map. These occur on north Moen and south uman. The lavas and pyroclastic rocks have only gentle dips. Slight distortions in some of the pyroclastic beds suggest mud flows or contemporaneous movement during their forma— tion. No structures were observed that will seriously impede tunneling operations. There are no natural solution caverns in the Truk Islands but old Japanese caves are undoubtedly buried and.may be encountered in exca- vation. One such cave is said to underlie the hotel in the Trust Ter- ritories administration area on Moen. This cave is reported to have been a torpedo storage which was sealed by an Allied bomb blast. The effect of tunneling on ground water is unknown. In caves at high elevations, ground water was not seen but the lower caves were wet and a few had standing water. Few streams are large enough to create problems to underground construction. The largest stream in the Truk 185 Islands, the Wichen River on Moen, is only a few feet wide throughout most of its length. As the islanders obtain fresh water from small streams, springs, and shallow wells, storage caves for poisonous liquids should be so placed that water-sources are not contaminated by seepage. Also subject to contamination are the shallow breadfruit pits in which breadfruit, wrapped in leaves and covered with stones, is stored. The bedrock of the eastern and central island is cut by many fine- grained dikes which range from a few inches to 8 feet in thickness. Seepage commonly follows the dike contacts, and during excavation blocks of the dike may be loose enough to fall. The blasting and shat- tering characteristics of the bedrock and dike rock probably will be different, with greater danger of rock fall from the dike rock. The period from January to March is a season of decreased precipi- tation. During this dry season supplementary water sources may be needed for projects which require large amounts of fresh water. The period of increased precipitation begins in April and ends in December. The rainfall is often intense and is blown horizontally, or at an ob- lique angle, across the area. Openings facing the northeast require protection against these rainstorms. Special problems Access: During the Japanese occupation narrow roads were built on the larger islands. Most of these roads are now abandoned and overgrown with vegetation (1955). The only roads maintained by the Trukese are those skirting the islands and those connecting important villages. Mbst of these are now footpaths, or at best jeep trails. Access to the sites noted as suited for tunnel-type installation is shown on maps hh through 50. In most cases, roads would have to be built. Concealment: The large number of coconut and breadfruit trees plus the heavy growth of tall grasses, reeds, and hanging vines provide conceal- ment of sites in most cases. Although cliffs are easily recognized, few of the Japanese caves dug in the cliffs can be seen on aerial pho— tographs. Unit areal relationships Eastern islands: The lava flows of the eastern islands are relatively thick, averaging 50 feet, and commonly show columnar Jointing. They form prominent cliffs which provide excellent sites for tunnel—type installations. Pyroclastic rocks are most widespread on MDen, Dublon Island, Yanagi, and Eten. During the Japanese occupation, numerous caves were excavated in the autobreccias and conglomerates underlying thick flows and in the brecciated parts of the flows. Most of the bed- rock of these islands, however, consists of undivided volcanic rocks (geologic maps 1 through 7). Mben: Tanaachau mountain, on the northern part of the island, is capped by the remnant of a basalt flow approximately 100 feet thick. The lower western slope of this mountain contains undivided lava flows (map #8, Unit 2) and weathered pyroclastic rocks. The northern lower slope is a columnar-jointed lava flow approximately 160 feet thick and 1,500 feet long in outcrop (map #8, site 1 and pl. 13). The lava is fractured into polygonal prisms, and a quarry exists along the face. 186 Plate 65 2' ~ 1‘ M’_ 1.2% Japanese gun , covered, Tanaachau mountain, Moen. Cave cut in conglom- erate. 1954-55. A. Japanese gun, covered, Tanaachau mountain, Mben. Tunnel cut into basal part of jointed and- esite flow overlying conglomerate. November 1954. B. Japanese gun, Witipon mountain, Moen. Cave out in trachyte flow which caps the mountain. 1954—55. Plate 66 The flow is approximately horizontal, with a very gentle dip to the northeast. It is underlain by conglomerate; a similar lava over con- glomerate exists several hundred feet upslope (map 5). A small spring issues from the contact of the flow and conglomerate. This cliff would be an excellent site for a large cave and would need little or no roof support except for the first 10 feet at the entrance where the Joint prisms are weathered, or where they are inclined into the face, or where cross fractures exist. There are two Japanese-built caves in this rock; one in the cliff facing north and one on the western edge. Both caves are about 5 1/2 feet high and are well drained. The rest of the Tenaa- chau area is generally covered by a deep soil mantle (Unit 6), into which the Japanese dug many trenches and holes most of which are well preserved. The northeastern spur of the mountain contains a series of connected caves cut into conglomerate and the underlying thick lava flow (Unit 1). The rock material is fairly soft and was apparently easy to work. Two naval guns, several storage rooms, and observation posts are in the unit area (pls. 65 and 66 A). The caves were dry and in excel- lent condition in 1955. Site 2, in north central Moen, is in a flow of andesite approxi- mately 75 feet thick overlain by 30 feet of basalt (Unit 3). The re— gional attitude is nearly horizontal and the rock is Jointed into polyg- onal columns. The soil cover is thin. No caves were found near this site. Installations in this area would be exposed to northeast winds and rains. On the east side of Wichen River valley are several localities fa- vorable for tunnel-type installations. One locality, at approximately 150 feet (#5 meters) elevation, is a basalt lava flow approximately 60 feet thick, with a gentle dip to the northeast (site h). an the west side of the valley (site 5), a hill #89 feet (1A9 meters) high is com- posed of an andesite flow underlain by conglomerate. The flow is ap- proximately 100 feet thick and consists of columnar—Jointed andesite. Several caves were constructed in the underlying conglomerate and are still in good condition. Witipdn mountain is capped by a flow of gray trachyte from 150 to 200 feet thick (pl. 3 and map #8, site 6). Vegetation cover is sparse and the soil is thin; concealment would a problem. Several old gun caves, at the east end of the flow, contain standing water blown in dur- ing rains (pl. 66 B). This flow dips 2 l/2° NE. The steep south side of Witipdn has one distinct andesite flow which is underlain by a bed of autobreccia. The andesite flow is almost 6,000 feet long in outcrop (map #9, site 7). In places the flow is 50 feet thick. Undivided flows of andesite and basalt are found on the southwest and northwest sides of the mountain. At the extreme eastern end of the island there is a small hill with an abandoned lighthouse at the summit. The lower part of this hill is formed of basalt (Units 3 and 5) which is not thick enough for tunnel- type caves, but it would be suitable for shallow shaft-type caves, such as gasoline storage pits. The upper part of this hill is formed of thick soils and undivided lava flows (Unit 6), most of which lie hori- zontally. Japanese installations consist mostly of bunker-type caves. The airfield on the southern part of the island is bordered on the east by a cliff composed of lava flows (Uhit l). The cliff is 150 feet high and has several excellent dry and well-preserved caves in its base. One cave (described in U. S. Navy Department, CINCPAC-CINCPOA, l9h6) is 187 large enough to have sheltered a seaplane. Another is about 18,000 cu- bic feet in volume. There are no supports of any kind in these caves. This is the area of site 8 (map #9). Docking facilities for small boats and an old seaplane ramp are nearby. A small hill, immediately north of the southern airfield, is form- ed on basalt flows and is the site of several Japanese caves. It prob- ably is too deeply weathered to be a good site for large caves. Winifourer mountain, in west central Moen, has a large triangular area on top and is made up of undivided porphyritic lava flows. Cliffs are on the south and northwest sides and are favorable sites for tunnel- ing (sites 9 and 10). Mount Teroken (Chukumong), to the west of Winifourer, has a steep western slope into which tunnels could easily be driven (site 12). Between Winifourer and the Trust Territories administration area is a quarry in andesite (site 11). There is a breccia-filled channel well enough indurated to support caverns without caving (Units 1 and 5). Several Japanese tunnels and caves were dug in both the andesite and breccia. Few of the caves have collapsed, but some contain pools of water. During the rainy season there is a waterfall near site 11. East of site 11 is a cliff of breccia 300 feet thick suitable for tun— neling (Unit 1, site 13). On the north central coast of Moen is the small island of Upwein, connected to the mainland by a causeway which is above water only during very low tides. Upwein is formed of andesite overlying conglomerate and breccia. The overlying andesite is mantled by deep soil. One small Japanese pillbox and supply room is cut into the conglomerate on the west side. No good tunnel sites were seen, but the area would be useful for the storage of materials requiring isolation. Fresh water is available near most of the construction sites, but this water comes largely from springs and very small intermittent streams. The largest stream is the Wichen River, with a discharge of approximately one-quarter of a million gallons a day during the season of least precipitation. Most of the ground water on Truk is potable with very little or no purification. Water may be scarce or entirely lacking at high elevations. Falo: Most of Falo consists of undivided lava flows (map #8, Unit 6) and is generally unsuited for tunnel-type constructions but excel- lently suited for bunker types. A cliff of basalt on the north side, approximately 60 feet high (Unit #), contains a Japanese cave in the lower portion. The flat sandy southern part of Falo is suitable only for hasty fortification (Unit 7). Surface runoff and wells provide the only fresh water. Yanagi: Yanagi is composed of breccia (map #9, Unit #). The is- land is about #5 feet high, 500 feet long, and 250 feet wide. Machine gun caves on the north and south sides are connected by a narrow tunnel. The rooms, about 15 by 15 by 6 feet, are dry and uncollapsed. The is- land is of value only as a military defense point or for the storage of very dangerous material requiring isolation. Surface runoff is the only supply of fresh water. Dublon Island: The rocks of Dublon Island consist mostly of un- divided lava flows. Mount Tolomen (1,125 feet elevation) is capped by 188 basalt and andesite flows. Breccia, mapped as unit 5, crops out on the south central part of the island (map #9). Conglomerate is exposed near the top of Fbukenau mountain. The northeast peninsula of Dublon Island is composed of basalt (Units 3 and 5). Dublon Island was the Japanese headquarters during their occupa- tion, and many caves were dug to house various military installations. Most of these caves were excavated in soft rock and in soil on the low- er slopes. Many of the caves are partly collapsed and contain standing pools of water (1955). A large cave at the southern end of the cause- way connecting the two peninsulas was lined with concrete 2 feet thick, but the lining is partly collapsed in the deeper part of the cave. Many small caves were dug in the soil, which is thick over most of the island. On the south side of Mount Tolomen several caves were dug in the autobreccia at the base of cliffs (area of site 1). Remains of double-track tramway are on the lower one-third of the mountain leading to a small perched valley (area of site 2), but no large caves which might have been serviced by this tramway were found. The tracks may have led to bunker-type huts. Suitable areas for underground construc- tion exist on both sides of Mount Tolomen, mostly in Units 2 and 6. Other suitable areas are a small hill at the south end of causeway (site 5); several cliffs on Foukenau mountain (site 3); and the north side of Mount Urikobosu (site h). NUmerous small streams, springs, and small wells on the island could probably provide adequate water. Eten: The hill forming Eten is composed of basalt lava flows overlain by pyroclastic breccia and conglomerate. The eastern half of the island is capped by basalt. Lenticular flows and stringers of ba- salt are intimately mixed with pyroclastic breccia on the lower eastern slopes. NUmerous caves were dug into a 20-foot-thick flow at the base of the hill and a short tunnel was excavated into the conglomerate at the southwest end of Eten. The caves are unlined except for an ammuni- tion depot. Several caves in fractured rock have roof supports. Mbst of the caves are dry and uncollapsed. All of the island is in Unit 2 except the capping basalt flow which is in Unit 3 (map 50). The best sites for caves are on the northeast and south sides of Eten in the 20- foot-thick basalt flow at the base of the hill (sites 1 and 2). There may be some drainage problems at both these sites. Eten has several fresh-water springs along the contact of the low- er flow and overlying pyroclastic breccia and from joints in the basalt. Fefan: Prominent cliffs in basalt flows extend north-south on the east side of Fefan and are favorable for tunnel-type excavations (map 50, sites 2 and 3). The base of the northernmost cliff is approximate- ly 420 feet in elevation and is 20 to 50 feet in height. The cliff is continuous for 3,500 feet (site 2). To the south on the east central part of the island a cliff extends for 1 mile (site 3). The cliff is formed by a 50-foot-thick basalt flow and apparently extends through the island, as a similar cliff on the western side of Fefan lies in the same general position (site h). Much of the southern end of the island is covered with a fairly thick soil mantle and is generally unfavorable for tunneling. Several steep slopes on the extreme southern end are, however, suitable for tunnel-type installations. A prominent 90-foot-high cliff on the west side of Chukuchap is formed in a series of basalt flows (site 5). On the north and north- 189 west slopes of Mbunt Iron several cliffs from 60 to 90 feet high formed on basalt (Unit.l) provide good locations for underground excavations (sites 1 and 6). Other favorable sites for tunneling are in areas of undivided volcanic rocks. Much of the island is suitable for bunker- type installations. Fefan has about 17 small streams, most of which are centered about the middle of the island. There are a few shallow wells. Param: The bedrock of Param is deeply weathered and.most expo— sures are covered by a deep soil mantle (map 50). Several Japanese- built caves in the hill at the west end of the island were reinforced with steel supports for protection against roof fall, but the caves have partially collapsed (U. S. Navy Department, CINCPAC-CINCPOA, 19’46). Phram is well suited for bunker-type excavations but tunnel types and shaft types would require extensive buttressing and lining. Param's water supply depends on surface runoff and fresh-water ponds. There are a few dug wells and the supply is adequate for the present population. Tarik: Most of the island has a deep soil overburden or gentle slopes or both and is unsuitable for tunnel- and shaft-type excavations. Some areas, Unit 6, are excellently suited for bunker-type construc- tions (map 50). There are no streams and the water supply is from small wells and springs. Tsis: Most of Tsis is mantled by deep soil and is unsuited for tunnel-type installations but is excellently suited for bunker-type construction. The island is largely mapped as Unit 6 with small areas of Unit 4 on the north and southeast (map 50). There are no streams and fresh water is supplied by shallow wells and surface runoff. Uman: Good sites for underground excavations exist in the steep slope which extends across the northern end of Uman (Unit 2). The base of the slope ranges from 300 to #50 feet in elevation. Bedrock is 10- cally exposed but more commonly there is a soil mantle from 10 to 30 feet in thickness. The peak of Mbunt uroras is surrounded by a steep lepe similar in character to the north slope (Unit 2). A 50- to 65-foot cliff formed on basalt on the eastern side of Uman is #30 feet (131 meters) above sea level at its base (site 2). The cliff is underlain by autobreccia in the base of the flow (pl. 5 B). Several small well-preserved Japanese caves are in the breccia at the south end of the exposure. A thin soil mantles the top of the cliff. At the southeast end of uman a basalt cliff rises from sea level to ap- proximately 60 feet (site 3). A tunnel-type installation in this cliff would not have 100 feet of cover but, because of other factors, the cliff is suitable for tunnel-type installations. On the southwest side a cliff rises from sea level to about 190 feet (site 1). The lower MO feet is)composed of basalt (Unit 1) overlain by undivided volcanic rock Unit 2 . A main boat pier is 1,000 feet south of site 1 and there is an ex— cellent small—boat pier 2,000 feet south of site 2. Fresh water is obtained from small streams, springs, and wells. Faneu: The bedrock on Faneu is basalt (Unit 5) rising 75 feet 190 above sea level. A small one-man torpedo-boat cave was started here by the Japanese. The water supply is extremely limited. Central islands: The principal bedrock of the central islands is well- indurated breccia and thin lava flows. Udot: Uitonap mountain, in western Udot, and the northern spur of the central hill are composed of undivided lava flows with some inter- bedded pyroclastic breccias (pl. 1h). The eastern half of Udot is pre- dominantly of well—indurated pyroclastic breccia. At the southeast end of the eastern hill (map #6, Unit 3) Japanese caves were excavated into the breccia at sea level. These were used as storage and sortie sites for torpedo boats (U. S. Navy Department, CINCPAC-CINCPOA, l9h6). Judging from these, any caves in the breccia will need very little sup- port and buttressing provided arched roofs are maintained during the excavation. Favorable localities for tunneling are along the northwest side of Uitonap (map #6, site 1), along the southwest coast of the central hill (site 5), in the eastern scarp of the east central hill (sites h and 6), on the north flank of the central hill (sites 2 and 3), and the 20-foot cliff on the southwest side of Fouwar mountain (site 7). Sites 2, 3, and h face northeast and may need protection from driven rain. Site 2 is near the main boat pier on northern Udot. NUmerous small streams, shallow wells, and springs provide an adequate supply of fresh water for the present population. Eot: This small island is composed of pyroclastic breccia cut by many dikes, similar to the Udot breccias, and is well suited for bunker— type construction. The island is mapped as Unit 5 except for an area with thin soil cover along the northeast shore which is Unit 3 (map #6). Site 1, on the southeast end of the island, is in Unit 2. This site is near the main pier on Eot. The water supply is from springs and shal- low wells. Eiol: The hill on Eiol is composed of pyroclastic breccia over- lain by 20 feet of andesite flow (map #7, Unit 6). The breccia is deep— ly weathered and tunnel-type excavations would need reinforcement. The water supply is from shallow wells. Western islands: The flows in the western islands are generally thin- ner than in the eastern islands. The main fracture directions are be- tween N. 50° E. and N. 70° E. and the bedrock is commonly cut by dikes. There are, however, three thick flows which are unfractured and not cut by dikes. There are very few breccia beds, but much autobreccia. Tgl: The island of Tol consists of four high upland blocks of volcanic rock, largely undivided lava flows, separated by long embay— ments. There are small amounts of pyroclastic breccia and many dikes of andesite and basalt. All the upland area on Pata peninsula (northwest T01) is covered with thick soil (maps 1m and 45, Unit 6) except the steepest slopes (Unit 2). Several dry uncollapsed caves on this peninsula are cut into deeply weathered rock. A natural tunnel exists on the northern spur. The central high part of the peninsula is favorable for tunnel-type ex- cavations (sites 1 and 2). Because of the numerous dikes and the un- certain nature of the bedrock, roof supports and other buttressing should be available for bracing. The lava flows in general are more 191 vesicular and probably more permeable than the usual basalts and andes- ites of the Truk Islands. Much of the area is well suited for bunker- type construction. Pata has two small streams on the northeast side and five on the south side. There are many small springs at the western and northern tips of the area. Polle peninsula (southwest T01) is composed of gently dipping un- divided lavas (Units 2 and 6), cut by many dikes and a prominent set of vertical fractures striking generally N. 60° E. The peninsula is well suited for bunker-type excavations. Fourteen small streams, several springs, and shallow wells supply fresh water for the area. The northern two-thirds of northeast Tol consists of undivided lava flows, out by many dikes and fractures parallel to the pattern of Polle peninsula. The southern one—third is composed of two thick flows, uncut by dikes, and unfractured except for columnar jointing. Steep slopes occur along the north (site 3) and the northeast (sites A and 5) and along the southeast edge of the southern flows. Excavations in the northern two-thirds may encounter seepage difficulties due to the prom- inent fracturing. A plateaulike surface in the southern one-third is developed on melilite-nepheline basalt (Unit 3). Bordering cliffs (Units 1 and 2) with talus at their base (Units 2 and 6) are favorable for tunneling (site 8, pl. 15 B). Still farther north a flattish up- land surface about 520 feet in elevation is capped by a nepheline basalt flow 100 feet thick (Unit 3). Bordering cliffs on three sides are favorable for tunneling (sites 6 and 7, pl. 15 A). Most of northeast T01 is suitable for bunker-type excavations. A few small streams and shallow wells provide an adequate supply of fresh water for the present population. Southeast Tbl is dominated by Mount Tumuital, the highest peak in the Truk Islands (l,h53 feet or hh3 meters). It is composed of undi- vided lava flows with only small amounts of pyroclastic breccia. Steep slopes lie on all sides of Mount Thmuital (sites 9 and ll). Many ex- cellent locations for tunnel-type excavations occur around the steeper slopes of Mount TUmuital, such as site 10. The area of the middle and lower slopes is generally in Unit 6, except for small patches of Unit h on the southeast and southern coasts. Areas of Unit 6 are excellently suited for bunker—type constructions. There are several small streams on the east side of Mount Tumuital. Fala-beguets: Uplands of the island are composed of undivided lava flows out by dikes. Deep soil mantles most of the surface. Ex- cept for mangrove (Unit 7) and two areas of Unit h, the island is all in Unit 6 and is well suited to small bunker—type of excavations (map #7). Two small streams, springs, and shallow wells supply fresh water for the island. Ulalu: The island is composed of a nepheline basalt flow mantled by thin soils and is mapped mostly as Unit 3 (map 46). The northeast, north, and northwest coasts are in Unit 5. Only one location suitable for a tunnel-type installation was noted; site 1 on the east end of Ulalu. Fresh water is obtained from springs and shallow wells. Reef islands: Small islands on the barrier reef and within the lagoon are composed largely of calcareous sands and are less than 10 feet 192 above sea level. constructed. Only very shallow bunker-type installations could be 193 GLOSSARY OF TERMS words are here defined as used in Military Geology of Truk Islands, Caroline Islands. acid soil - A soil giving an acid reaction throughout most or all of the portion occupied by roots. (see soil reaction) alluvial soils - An azonal group of soils developed from alluvium characterized by weak modification, or none, of the original material by soil-forming processes. amygdaloidal - A term describing the texture of a vesicular rock in which part or all of the vesicles have been filled by infiltra- tion. andesine - A mineral of the plagioclase group composed of silicate of sodium and calcium. andesite - A dark-colored, fine-grained, volcanic rock composed essen- tially of plagioclase together with one or more of the magnesium- iron minerals. Distinguished from basalt chiefly in having more sodic plagioclase and a smaller percent of dark minerals in the fine groundmass. antigorite - A brownish-green variety of chlorite. augite - A common rock-forming pyroxene; dark colored and containing considerable alumina and iron. autobreccia - Flow rock that has become fractured during or shortly after extrusion. Such breccias occur commonly at the top and bottom of flows. basalt - Dark-colored, fine-grained, igneous flow or dike rock composed essentially of calcic plagioclase, pyroxene, and with more or less olivine. In texture they may be even grained, porphyritic, vesic- ular, or amygdaloidal. bauxite - The term applied commercially to aluminous lateritic rocks in which aluminum hydroxides, amorphous or crystalline, predominate over other lateritic constituents; the most common aluminum ore. berm - The nearly horizontal surface of the beach which extends inland beyond the normal limit of wave uprush, constituting a small im- permanent terrace formed by deposition during calm.weather and by erosion during storms. biogenic - Of organic origin. breccia - A fragmental rock with angular components as distinguished from conglomerate with rounded water-worn components. calcareous soil - Mildly to strongly alkaline soil containing suffi- cient calcium carbonate to effervesce visibly to the naked eye when treated with hydrochloric acid. (see soil reaction) chlorite - A general name for the platy, green, hydrated silicates 195 which contain aluminum and iron, and which are especially derived from augite, hornblende, and biotite. clay - (soils) A textural term for particles less than 0.002 mdllimeter in diameter; a fine-textured soil composed chiefly of clay-size particles. (engineering soils) Inorganic fines (less than 0.07h millimeter diameter) plotting above the A line on plasticity chart. colluvial - An adjective denoting the heterogeneous aggregates of rock detritus. color index - In petrology, the sum of the dark minerals in a rock ex- pressed in percent. It is especially applied in the classifica- tion of igneous rocks. In Kuno's classification, bulk chemical analyses are made; groundmass composition is then determined by subtracting the known composition of phenocrysts present in the rock and recalculating the remainders to 100 percent. A hypo- thetical mineral composition (norm) of the groundmass is calcu- lated; from this norm the color index is determined by the propor- tion of hypothetical dark.mineral (wollastonite, enstatite, oli- vine, calcium orthosilicate, magnetite, ilmenite, hematite) to the total mineral content. There is a rough approximation between this and older classifications based on composition of the feld- spars or the presence of olivine. concretions - local concentrations of certain chemical compounds, such as calcium carbonate or compounds of iron, that form hard grains or nodules of mixed composition and of various sizes, shapes, and colors. conglomerate - A rock made up of water—worn and rounded pebbles of other rocks cemented together. cumulus - A.massy cloud form, usually occurring in the middle cloud re- gion (at elevations between 5,000 and 15,000 feet), having a flat base and rounded outlines, often piled up like a mountain. detritus - Matter worn from rocks by mechanical means. dike - A.wall-like intrusion of igneous rock, which cuts across the bedding or other layered structure of the country rock. The thickness is narrow in proportion to the other two dimensions. dip - The angle at which beds or strata are inclined from the horizon- tall feldspars - A group of rock-forming minerals, essentially silicates of aluminum, potassium, sodium, and calcium. ferruginous - Iron bearing; usually refers to material of comparatively high iron oxide content. firm - A soil consistence term describing soil material which, when moist, crushes under moderate pressure between thumb and fore- finger but is noticeably resistant. (see soil consistence) friable - A soil consistence term describing the ability of soil mate- rial, when moist, to be easily crushed under gentle to moderate pressure between thumb and forefinger and to cohere when pressed 195 together. (see soil consistence) gabbro - A dark-colored, coarse-grained igneous rock, with essentially the composition of basalt. groundmass - The relatively fine crystalline or glassy portion of a porphyritic rock as contrasted with its larger crystals. hornfelsic - A rock texture term referring to an equigrannlar, fine- grained, compact, contact-metamorphosed rock. hydrophytic plants - Plants which thrive in water or in saturated soil as in marshes or swamps. insolation - Received solar radiation, as by the earth; rate of deliv- ery of all direct solar energy per unit of horizontal surface. lapilli - Volcanic ejecta consisting of fragments of lava of rounded or irregular shape from h-millimeters to 32 millimeters in diameter. laterite soils - The zonal group of soils having very thin organic and organiCemineral layers over a reddish leached soil that rests upon highly weathered material relatively rich in hydrous alumina or iron oxide or both and poor in silica; usually deep red in color. laterization - The soil process which tends toward the production of Iaterites and lateritic soils. Essentially it is the process of silica removal with consequent increase in the alumina and iron oxide content and decrease in base-exchange capacity of the soil. Latosol - Brownish-red, yellowish-red, and red, highly weathered, ses- quioxide-rich, clayey materials whose thickness may exceed 50 feet. Mbst Latosols are acid in reaction and contain ferruginous concretions. limonite - A hydrous oxide of iron. lithification - The consolidation of liquid or loose materials into solid rock. The term thus includes the solidification of molten lava and the compaction or cementation of loose sediments into rock. Iithosol - An azonal group of soils having no clearly expressed soil morphology and consisting of a freshly and imperfectly weathered mass of rock fragments; largely confined to steeply sloping land. magnetite - The magnetic iron oxide. massive structure - (geology) (l) A homogeneous structure without stratification, foliation, schistosity, or the like; (2) occurring in thick beds free of minor joints and lamination. (see also soil structure) matrix - The fine material of rocks in which larger fragments are em- bedded. melilite - An orthosilicate of sodium, calcium, aluminum, and other metals. 197 mesa - A flat-topped tablelike mountain with steep cliffs on at least three sides. metavolcanic - Partly metamorphosed volcanic rock. muck - Fairly well decomposed organic soil material, relatively high in mineral content, dark in color, and accumulated under condi- tions of imperfect drainage. nepheline - One of the feldspathoid group of minerals, which occur in silica-deficient rocks. nepheline basalt - An undersaturated basaltic rock essentially contain- ing nepheline, pyroxene, and olivine, with little or no feldspar. neutral soil - A soil that is not significantly acid nor alkaline; strictly one having a pH of 7.0, practically one having a pH between 6.6 and 7.3. (see soil reaction) olivine - The common species is a silicate of magnesia, often of green glassy character; occurs in the darker igneous rocks such as ba- salt, diabase, and gabbro. olivine basalt - Basalt which contains olivine as an essential consti- tuent and differs from the normal rock only in the texture as modified by the presence of that mineral. organic soil - A general term used in reference to any soil the solid part of which is predominantly organic matter. parent material - The unconsolidated mass from which the soil profile develops. (see soil profile) peat — Unconsolidated soil material consisting largely of undecomposed or slightly decomposed organic matter accumulated under conditions of excessive moisture. pegmatitic - A rock texture term used to describe coarse-grained igne— ous dikes and veins and segregations in a massive even-grained rock. pH - A symbol denoting the negative logarithm of the concentration of the hydrogen ion in gran atoms per liter, used in expressing both acidity and alkalinity. A pH of 7.0 indicates neutrality, higher values indicate alkalinity, and lower values, acidity. phaneritic - Rock texture term meaning all but a small proportion of the grains in the rock can be seen by the unaided eye. phenocryst - A relatively large and conspicuous crystal in a porphyrit— ic igneous rock. plagioclase - A collective name for the sodium-calcium feldspars, com- posed of aluminum silicates of soda and lime, such as albite, oligoclase, labradorite, and anorthite. plastic - A soil consistence term describing the ability of soil materi— al, when wet, to change shape continuously under an applied stress and retain the impressed shape on removal of the stress. (see soil consistence) 198 porphyritic - Texture of igneous rocks where larger crystals are en— closed in a finer groundmass. pyrite - An iron sulphide mineral, generally occurring as hard, shiny yellow, cubic crystals. pyroclastic - Produced by explosive ejection of material from a volcan- ic vent; also a textural term used for rocks formed in this manner. pyroclastic breccia - A fragmental rock formed by explosive volcanic action. The fragments are generally angular and range in size from dust to blocks several feet in diameter. pyroxene - A normal metasilicate mineral, chiefly of calcium and.magne- sium and also iron. reticulate mottling - A network of coarse streaks of different colors in soils or parent material; applied especially to lateritic ma- terials and Laterite. Sometimes called vermiculate mottling. sand - (soils) Small rock or mineral fragments having diameters ranging from 1 to 0.05 millimeter; coarse sand, 1 to 0.5 millimeter; medium sand, 0.5 to 0.25 millimeter; fine sand 0.25 to 0.1 milli- meter; and very fine sand, 0.1 to 0.05 millimeter. The term sand is also applied to soils containing 90 percent or more or all grades of sand combined. Although usually made up chiefly of quartz, sands may be composed of any materials or mixtures of min- eral or rock fragments. (engineering soils) Rock or mineral grains from h.76 millimeter to 0.074 millimeter in diameter. saponite - A hydrous silicate of magnesium and aluminum. scoriaceous - A term applied to pyroclastic ejecta, usually of basic composition, characterized by marked vesicularity, dark color, heaviness, and a texture that is partly glassy and partly crystal— line. serpentine - A hydrous magnesium silicate mineral aggregate; a metamor— phic rock composed chiefly or wholly of serpentine. set of a tide - The direction of flow; for flood tide it is the direc- tion to which the current advances, for ebb tide it is the direc— tion to which the current retreats. silt - (soils) Size term indicating particles or stable soil aggregates ranging in diameter from 0.002 millimeter to 0.05 millimeter. (engineering soils) Inorganic fines (less than 0.07h millimeter) generally of relatively low plasticity and plotting below the A line on the plasticity chart. solum - The upper part of the soil profile, above the parent material, in which the processes of soil formation are taking place. In mature soils this includes the A.and B horizons, and the character of the material may be, and usually is, greatly unlike the parent material beneath. Living roots and life processes are largely confined to the solum. 199 soil soil soil soil soil soil soil soil complex - A mapping unit which consists of two or more taxonomic units so intimately associated geographically that they cannot be mapped separately. consistence - The attributes of soil material that are expressed by the degree and kind of cohesion and adhesion or by the resist- ance to deformation or rupture. The terminology includes separate terms for description at three standard moisture conditions: dry, moist, and wet. If moisture conditions are not stated in using any consistence term, the moisture condition is that under which the particular term is defined. Consistence terms used for de- scribing the wet condition are sticky and plastic; the moist con- dition, friable and firm; and the dry condition, soft and hard. genesis - Mode of origin of the soil, referring particularly to the processes responsible for the development of the solum from the unconsolidated parent material. horizon - A layer of soil approximately parallel to the land sur- face with more or less well-defined characteristics. phase - That part of a soil unit or soil type having minor varia- tions from the characteristics normal for the type. Although minor, the variations may be of great practical importance. They are chiefly in such external characteristics as relief, stoniness, or accelerated erosion. profile - A vertical section of the soil through all its horizons and extending into the parent material. reaction - The degree of acidity or alkalinity'of the soil mass, expressed in pH values or in words, as follows: Extremely acid below h.5 Very strongly acid h.5 to 5.0 Strongly acid 5.1 to 5.5 Medium acid 5.6 to 6.0 Slightly acid 6.l to 6.5 Neutral 6.6 to 7.3 Mildly'alkaline 7.h to 8.0 Strongly alkaline 8.1 to 9.0 Very strongly alkaline 9.1 and igher structure - The aggregation of primary soil particles into com- pound particles or aggregates. TErms for grade of structure, or aggregate strength, are: weak - when disturbed, the soil material breaks into a few intact peds, many broken peds, and much unaggregated material. moderate - peds distinct in undisturbed soil; disturbed soil breaks down into many intact peds, some broken peds, and little unaggregated material. strong - peds distinct and adhere weakly in undisturbed soil; disturbed soil material chiefly composed of entire peds with a few broken peds and very little unaggre- gated material. Tbrms for class of structure, or aggregate size, are very fine, fine, medium, coarse, and very coarse. In referring to shape and arrangement of aggregates, or type of structure, the following terms are used: granular - hard or soft but firm small aggregates, angular or rounded. single grain - each grain by itself, as in dune sand (structureless). massive - large uniform masses of cohesive soil, sometimes with irregular cleavage, as in the C horizons of many heavy clay soils (structureless). In describing soils structure, it is customary to combine the three terms denoting grade, class, and type. For example, a soil that is moderate coarse granular has moderate aggregate strength, coarse aggregate size, and granular aggregate shape. soil texture - The relative proportion of the various size groups of individual soil grains. Soil separates - the individual size groups of soil particles, such as sand, silt, and clay. Soil class - classes of soil based on the relative proportion of soil separates. The principal classes, in decreasing order of the content of the finer separates, are: sand, loamy mm,wMyhm,bm,flhlmmchymm,wddw. These may be modified according to the relative size of the coarser particles to fine sand, loamy fine sand, fine sandy loam, very fine sandy loam, and so on. talus — An accumulated heap of rock fragments derived from and lying at the base of a cliff or very steep slope. trachyte — Light-colored, fine-grained, igneous flow or dike rocks differing from andesites chiefly in having more alkalic feldspar and less dark minerals in the fine groundmass. trondhjemite - Light-colored, acidic, deep-seated igneous rocks, whose essential light-colored components are plagioclase and quartz. tsunami - Destructive ocean waves produced by submarine earth movement or volcanic eruption; commonly, though erroneously, called tidal wave. tuff - Indurated pyroclastic rock of grains generally finer than h millimeters, the indurated equivalent of volcanic ash or dust. unconformity - An erosional break in the continuity of rock deposition. Where one formation rests on the eroded surface of a lower one, the two are said to be unconformable and the erosional gap is said to be an unconformity. vesicle - A small cavity in an aphanitic or glassy igneous rock, formed by the expansion of a bubble of gas or steam during the solidifi- cation of the rock. water table - The upper surface of the part of the soil, or underlying material, wholly saturated with water. 201 BIBLIOGRAPHY ‘ American Association of State Highway Officials, 1919, Manual of high- way construction practices and methods. Asano, Kiyoshi, 1939, Limestone of the South Sea Islands under Japanese mandate, i_n_ Jubilee Publication in the Commemoration of Prof. H. Yabe, M.I.A., Sixtieth Birthday, Sendai, Japan, v. 1, p. 551-560. [translation by Engr, Intell. Div. , Office of the Engineer, HQ, U.S. Amy Forces, Far East on file in Military Geology Branch, U.S. Geological Survey, washington, D.C;7 , 1912, Coral reefs of the South Sea Islands: Japanese Re- port of Geology and Paleontology, Tohoku Imperial University, no. 39, p. 1-19. [translation by Engr. Intell. Div., Office of the Engineer, HQ, U.S. Army Forces, Far East on file in Military Ge- ology Branch, U.S. Geological Survey, Washington, D.CJ ‘ Bridge, Josiah, 19118, On the occurrence of bauxite on _'l‘ruk: Pacific Science, v. 2, p. 223-224. Gladwin, Thomas, and Seymour Sarason, 1953, Truk: man in paradise, in Viking Fund Publications in Anthropology no. 20, Wenner-Gren Foun- dation for Anthropological Research, Inc. , New York, N.Y. Kuno, Hisashi, 1950, Petrology of Hakone volcano and adjacent areas, Japan: Geol. Soc. America Bull., v. 61, p. 957-1020. MacDonald, G.A., l9h9, Petrography of the island of Hawaii: U.S. Geol. Survey Prof. Paper 21h-D. , 1953, Chrono-volcanological data for the Hawaiian Islands: Extrait du Bulletin Volcanologique Organe de l'Association de Vol- canologie de l'Union géodésique et géophysique internationale, Serie II, Tome XIII. McConnell, D., R.C. Mielenz, W.Y. Holland, and K.'1'. Greens, 1950, Pe- trology of concrete affected by cement-aggregate reaction, in Application of Geology to Engineering Practice, Geol. Soc. America .._ Berkey Volume, p. 225-250. Okabe, Masayoshi, 19142, An enumeration of the plants collected in Truk, east Caroline Islands: Jour., Japanese Forestry Soc., v. 2:, p. 287-307. Eranslation by Engr. Intell. Div. , Office of the Engi- neer, HQ, U.S. Army Forces, Far East on file in Military Geology Branch, U.S. Geological Survey, Washington, D.C_.] Stark, J .'1‘., and A.L. Howland, l9hl, Geology of Borabora, Society Is- lands: Bernice P. Bishop Mus. Bull. 169. Stearns, Harold '13., 19146, Geology of the Hawaiian Islands: Territory of Hawaii, Division of Hydrography Bull. 8. Stearns, Harold T. , and K.N. Vaksvik, 1935, Geology and groundwater re- sources of the island of Oahu, Hawaii: Territory of Hawaii, Divi- sion of Hydrography Bull. l. 203 Tayama, Risaburo, 1939, Correlation of the strata of the South Sea Is- lands: Geol. Soc. Japan Jour., v. #6, no. 5A9. [translation by Engr. Intell. Div., Office of the Engineer, HQ, U.S. Army Forces, Far East on file in Military Geology Branch, U.S. Geological Sur- vey, Washington, D.CL7 , l9h0-19h1, Geomorphology, geology, and coral reefs of Truk Islands, in Jubilee Publication in the Commemoration of Prof. H. Yabe, M.ITK., Sixtieth Birthday, Sendai, Japan, v. 2, p. 709-723. [in Japanese, English abstract7 [translation by Engr. Intell. Div., Office of the Engineer, U.S. Army Forces, Far East on file in E%litary Geology Branch, U.S. Geological Survey, washington, D.C. , l9h2, Character and distribution of coral reefs in the South Seas: Ph. D. thesis (part), Tohoku Imperial Uhiv. (published in revised version as Coral Reefs in the South Seas, 1952) , 1952, Coral reefs in the South Seas: Hydrogr. Office, Takyé, Japan, Bull. v. 11, 1). 1-181 (Japanese), 1). l8h-292 f‘ (English). [translation by Engr. Intell. Div., Office of the ' Engineer, U.S. Army Forces, Far East on file in Military Geology Branch, U.S. Geological Survey, Washington, D.CL7 U.S. Department of Agriculture, 1938, Soils and men, yearbook of agri- culture 1938, Washington, D.C. , 1951, Soil survey manual: U.S. Dept. of Agric. Handbook no. 18, rev. ed., Washington, D.C. U.S. Department of Commerce, Coast and Geodetic Survey, 1955, Tide tables, central and western Pacific and Indian Oceans. U.S. Department of Commerce, Weather Bureau, l953—195h, Local climato- logical data with comparative data. U.S. Department of Interior, Geological Survey, l9hh, Strategic engi— neering study no. 106, Truk Islands (Carolines), terrain intelli- gence: rev. ed., prepared under direction of Chief of Engineers, U.S. Army. U.S. Navy Department, CINCPAC-CINCPOA, l9h6, Field survey of Japanese ‘ defenses of Truk: Bulletin no. 3-h6. U.S. Navy Department, Hydrographic Office, 19hha, Approaches to Truk Island. (Caroline Is.): [mp7 scale l:963,307, H.O. Chart 5201. , l9hhb, Truk Islands. (Caroline Is.): [map scale l:l26,350, H.O. Chart 60%. , lghhc, Truk Islands, northern part. (Caroline Is.): [£3.27 scale" 1:55.600, 11.0. Chart 601w. , 19hhd, Truk Islands, southeastern part. (Caroline Is.): Zmap? scale l:55,600, H.0. Chart 60h8. , l9hhe, Truk Islands, western part. (Caroline Is.): [map7 scale 155,180, 11.0. Chart 60kg. 204 U. S. Navy Department, Hydrographic Office, l9hhf, Plans in the Truk Islands. (Caroline Is. ): f _7 scale 1: 15,000, H. 0. Chart 6051. , l9h5, Sailing directions for the Pacific Islands: H.O. Pub. no. 165. U.S. War Department, l9hh, Aviation engineers: War Dept. Tech. Manual, I’M 5-255. Wentworth, C.K., and Horace Winchell, l9h7, Kbolau basalt series, Oahu, Hawaii: Geol. Soc. America Bull. v. 58, p. h9-78. Winchell, Horace, l9h7, Honolulu series, Oahu, Hawaii: Geol. Soc. America Bull. v. 58, p. l- h8. unpublished References Bridge, Josiah, l9h6a, Mineral resources of the eastern Caroline Is- lands, in Economic Survey of Micronesia, v. 3, part 1, U. S. Com- mercial“ Company, Honolulu, T. H. [microfilm on file in Library of Congress, Washington, D. CL] , l9h6b, Field notes in connection with the economic survey of Micronesia, U.S. Commercial Company, Honolulu T.H. [microfilm on file in Library of Congress, washington, D.C. Bryan, E. H., Jr. ., 1946, A geographic summary of Micronesia and notes on the climate of Micronesia, in Economic Survey of Micronesia, v.2, parts 1 and 2, U. S. Commercial Company, Honolulu, T. H. [microfilm on file in Library of Congress, Washington, D. C57 Endo, Ruiji, l9h9, A lexicon of geologic names of the Caroline Islands, Palau Islands, Yap Islands, Fais Islands, Truk, anape, and Khsaie Islands (preliminary): compiled by Engr. Intell. Div. ., Office of the Engineer, HQ, U. S. Army Forces, Far East on file in Military Geology Branch, U.S. Geological Survey, washington, D.C. Omukai, Rydshichi, l9h2, Geomorphology, geology, and geochemical studies of coral reef limestone of the Truk Islands and Khop Is- lands: unpublished thesis, Inst. Geol. and Paleont., Tbhoku Uhiv. [translation by Engr. Intell. Div., Office of the Engineer, HQ, U.S. Army Forces, Far East on file in Military Geology Branch, U.S. Geological Survey, Washington, D.CL7 Piper, A. M., l9h6-l9h7, Water resources of Guam and the ex-Japanese mandated islands in the western Pacific, in Economic Survey of Micronesia, v. h, part 3, U. S. Commercial— Company, Honolulu T. H. [microfilm on file in Library of Congress, Washington, D. C. 205 For Fe IOI seeunop of Dublon Island below ——-—TS'S F, fUd ”4 I 9 U re I 6 Photo index map 507 1“.04 Truk Islands Um l05 3w '08 50 WHO? Contour In’rervol 50 meters Conversion from the authors' original field photo numbers shown on the map to the photo plate numbers used in this report. Photo negatives are filed by field photo number. Mo = Moen, Fe. = Falo, Du = Dublon Island, Et = Eten, Fe = Fefan, Pa = Param, Ts = Tsis, Um = Uman, Ud = Udot, To = T01, U1 = Ulalu, OR = outer-reef islands. plate field photo plate field photo plate field photo number number number number number number 1 Et 20A 8-3 23 A Mo A1A A5 B Du 100 2 Pa 10A a-c 23 B Mo A15 A6 A Du 211 3 M0 218 2A Mo A12 A6 B Du 111 A A 011 118 25 A Mo A06 A7 A U1 100 a A B Mo 1A3 b 25 B Ul 205 A7 B Ul 100 b 5 A To 102 b 26 U1 A09 A8 A Um 107 5 B Um 113 27 Mo A16 A8 B Um 108 w 205 g A Um 117 a. 28 Mo :32 A9 Pa 201 B Fe 101 29 Mo 50 A To 107 U294 Ul 409 20 STOTUTe 7 A To 110 30 A Ud 118 50 B To 108 d U|4l7 \o (—058 5 IO I5 Miles 7B F2102 30B Ud 11o 51A Ud 108 °~> ”"0' ;. .,-,.L.A,J,A x ‘1 3% 82:: ii: 33%: 2:2 33:33 UI I07 5 IO I5 20 25 30 Kilometers 9 A on 117 32 A Du 113 52 B Du 126 0’7 Ul IOOb 9 B Du 117 32 B Du 13A 53 A Pa. 106 10 A Fe 102 33 A Mo A05 53 B Pa 207 UIIOOO EXPLANATION 10B Du12Ab 33B M0106 5A T0106 ULALU 11 A Ul 107 3A A Um 103 55 A Mo 1A5 . . - 11 B U1 A17 3A B Um 101 55 B Um 118 °"’ Direction Of phOfO V|€W 12 A To A00 35 M0 108 56 A M0 109 12 B To A01 36 A To A10 56 B Um 102 - - - - 13 M0 121 r 36 B Ud 11A 57 To A02 < Dlrec’non Of pOn0rOm|C VleW 1A Ud106b 37A Mo A11 58A U110A 15 A To 112 37 B Um 10A 58 B U1 101 15 B To 101 b 38 A Du 1A0 59 A Ts 10A 12 A To 111 b 38 B Du 138 29 B Du 132 1 B on 107 39 A Du 128 o A Du 139 To 400 17 A on 121 b 39 B Du 127 60 B Du 135 X‘ITO 40' 17 B 011 108 8. A0 M0 100 61 A Du 103 O 18 A OR 203 A1 A Mo 1A0 61 B Um 105 e0 05‘) p0 205 18 B OR 20A A1 B M0 131 62 M0 125 POZOI 19 A OR 120 A2 A M0 136 a 63 A Pa 203 P0 207 / Pa 204 19 B OR 116 8. A2 B M0 139 63 B Pa 206 P0 '04 P0 203 FALO 20 A on 106 A3 A M0 126 a 6A A Pa 20A _ —— 20 B 0R 12A A3 B M0 126 b 6A B Pa 205 O C P 21 A M0 228 AA A Du 116 b 65 M0 222 OIOB 21 B E1: 203 AA B Du 115 66 A Mo 20A / 22 A Mo :07 A5 A Du 11A 66 B Mo 1AA a 0/7 0/ 22 B Mo 13 P0 206 F0 '02 PARAM (Aerial phoTo) M0 4 I5 A JMO'ZS DUBLON ISLAND ToI M0 I260 \LY'0 406 Mo I26b éZIOZb ................. --.oRII6d LOITIOII ‘ORIOBO fRiIH-m RUOC -. _ Toro ' ' - _ :1} ;-:__._0Rn7 Borruer reef Islets "'%'N°"he°g it MOEN I W ”1;”ur- 000T DUBLON KS \OMO 4 I 6 : ,. 0 0L 9 ‘1". <5) Onomgngo £5 0 FEFAN FALA-BEGUETS pmm M O E N \IMO '00 .... E. 233?..ORIO7 Tgs DUMAN ‘Eo '0 -.. e I V "1%8506 :0} om) '40 OH --'.:":::::‘-"::-‘.'.x I:::«::x -1'-1!-‘.:::. 5i; 0" on "in, Fonon%0R203 ‘0 E T E N .1111 5 losmtute Miles U1 1e ——" l'"‘ ' v‘ ' 3 "' '1 v ‘1 v" 1L v ‘I J lefiJ 8.‘ 5 IO I5Kilome’rers 207 . «mic . TRUK ISLANDS CAROLINE ISLANDS 125,000 UDOT SW 30 .LLLI i I lrLLi 40 5° 6° 7° Military Geology of Truk Islands MAP 1 Geology and Water Resources 15132100! 339 32/30” 340 341 342 343 35/00! 344 345 346 348 37/30” 349 351 151°39'30” 7°27'00’ I I \ w, I, 2} 3 I 30 . 7°27’00” / /:’5\ l ,9 .29.. \a a ,1 x, 2 [,1 29 33 30 J/ 25 coral PA C I L2 (/3 25 (map 29 x"\/ / 0\\ If 1 \ coral 22 / / / 1 ‘r I 3 \ 26 3 / I \\ 30 l 64 l / l 3 r 8 i l LLL I ’ cor‘al / r I l coral I , ~ \ ..L : 15 823 823 / \ \o/ ,I x ,I 1 x‘ K ._I / / 293W [,76L\\ \LLLL/\L3_5‘ r\ 52 4_£Z /\~\ "‘x\ // \i ,1 ‘\ \\ >1 1/ II \1 m r @r 32 .31. a x i 1" i 55 //\/\ coral (II \ ‘17—: I \3—: /I 12 \\\ >’,\1¥. L_I sngci 27 I 2;; “”1 , «x 27 g/ 23 ’0 \1 fl. 31 L\ 29 , 8 K / “3V1 :1; 32 \ ’/ 2 j“ ,2, \24/ [/7 \\ 2/2 \1 l/ / ’O‘E/ ,’/—;\\\IQ Ifl, coIaILL// 33 Ii, ,LL \ 29 r' 7 \\\\ / ,z "x l\ 8 K5?" ,;7 a; ,1 ,fl ‘3 m 26 29 322 822 \ l/[L/lrr Coral ””7“" \ \‘\~/\ég 28 ----------------------------------- Q9 29 WATER RESOURCES TRUK ISLANDS I 4 777777777777 coral ———————————————————————————— , 2 I \‘x K/ W indicates swept depth area in feet 285 6 L H 2 43 44 45 8 , 46 47 EXPLANATION 51 coral 1 35 27 41 ”T3 24 50231 21 (if) 5 25 25 6 A 15 “"a' 31 C) /L SYMBOLS DESCRIPTION SYMBOLS DESCRIPTION /’ 1 coral 33 [//L T/ "5’1 19 3/1:\ 6 I Q 26 35 / T/ ) Spring / Water tunnel I ZGI ’ 4 747 / C078 21 1 19 lo \T) 22 T R U K I S l- A N D S g, I" Spring flow in gallons per minute ® Rain gage - {AL/ // .W __ 821 42 A ,L/E'SZ LL 4”“ / W /‘ l WL‘ 6 15 14\ ' 26 l 32 r WL/T" ma 0 Well or waterhole © Stream gage 23 19 2 1 Lr" coral 16 . coral coral 23 22 _L—’ ’7 ® GEOLOGY TRUK ISLANDS w 28 32 «~- 1, 2. cora x" 9 3f 41 21 24 \16 34> coral ’r/VXL’E' / Ali/LI 4 X, 28 EXPLANATION \/ \4/ /,L/ ”’ (1:531 ‘\’ Stream discharges, Tol, January 1955 16 ,LL/ " 1‘ x Q. . 27 5:) 28 L—r””/ 25 KM” 27 stream number million gallons per day gallons per mlnute L/V" 28 ' r w m' 30 1 ii 0.13 90 25/ 00' UNIT DESCRIPTION 44/er? "4 ’17— 2 * 0.22 150 22 25,00” — —— 29 L—/”’ — 8 320 14"“ I 20 ”LL/"E T 3 * 0.16 112 £21 20 vol Undivided volcanic rocks. chiefly basaltic and andesitic lava flows. ,x’" i\ ,z”‘\\ ”Ly/"V 1+ «11- triCkle _ / ,ICD) 18 3o 26 xxx/23"” 5 * trickle _ Andesite lava and autobreccia. 31 \f/ ,(Z’l‘r r 29 6 * 0-13 9O 21 12 532 7 * 0.13 90 21 Trachyte lava and autobreccia. 24 5 29 [La/”V I 8 * 0.16 112 24 19 21 C5) TRUST TERRITORY or THE PACIFIC ISLANDS Q3 9 no data _ 3 ,3 Basalt lava and autobreccia, most of which is olivine basalt (that is, contains more (U.S.A. 1 a 0 15mm We Geology by John T- Stark, Richard L- Hay, Harold G. May, and Elmer us, ARMY MAP SERVICE, FAR EAST - 57-041 - n15 , 11/58 . 3.4c . . A , } r A D. Patterson, 1954-1955. Water resources by Max H. Carson, 1955. Prepared under the direction of the Engineer, Hq AFFE/BA, by the US“. Army Map Service, Far East. 1000 500 ° 1000 2000 Meters Compiled in 1957 by photogrammetric (multiplex) methods. Coastal hydrography compiled from USHO I I OI I 500 I i 0 006 00 Chart 6049, 19441 Horizontal and vertical control established by Corps of Engineers, 1951. Names trans~ IOIO H H H H H 1 . :' OYards literated in accordance with rules of the US. Board on Geographic Names. Major roads are classified by % ’ _ reconnaissance by the 64th Engineer Battalion (Base Topographic), 1952; other roads are classified from 1 J O lNam'caI M'Ie source maps and aerial photography and are not verified by reconnaissance. Coastal vegetation are clas- ' ’ COVERAGE DIAGRAM INDEX TO ADJOINING SHEETS sified by reconnaissance by Military Geology Branch, intelligence Division, Office of the Engineer, Hq AFFE/BA, with personnel of the US. Geological Survey, 1955. Map not field checked. CONTOUR INTERVAL IO METERS VERTICAL DATUM- MEAN SEA LEVEL 4544 ll NW Geologic and water resources data based on on field investigations 1954-1955 by Military Geology MAP 5 Branch, Intelligence Division, Office of the Engineer, Hq, U. S. Army Japan with personnel of the TRANSVERSE MERCATOR PROJECTION U. 3. Geological Survey. HORIZONTAL DATUM lS BASED ON THE ASTRONOMIC STATION NO. 2 (I95I )' \\ 151°53’34 3” EAST OF GREENWICH. 7°21’37.7” NORTH 4544 III SW 4544 111 SE 4544 11 SW LEGEND HYDROGRAPHIC DATUM: APPROXIMATE LEVEL OF LOWEST Low WATER 3‘“ 5‘ MAP 1 MAP 3 MAP 6 V 10108 ' \\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\§\b\§\\ \\ BLACK NUMBERED LINES INDICATE THE 1000 METER UNIVERSAL TRANSVERSE \x‘§\ W\‘\“\‘\\Z‘R\\\§\\§ All weather MERCATOR GRID. ZONE 56. INTERNATIONAL SPHEROID §\\\:\\ Q\N§\\\\\\‘\\\ 4543 IV NW 4543 IV NE 4543 I NW . 5\. ’ » hard surface, two or more lanes wide None Built-up area WLWLLLLWLLLLWL. _, .L LLLLLL LLLL THE LAST THREE DIGITS OF THE GRID NUMBERS ARE OMITTED §&:‘&\\‘&&x\&§§§$§fi“ ‘Q‘ MAP 2 MAP 4 MAP 7 GN ‘ ' \‘ ‘ - loose or light surface, two or more lanes wrde None Church; School; Cemetery .LL,.WLWW_ VLLLiL WmmN hard surface, one lane wide 7 None LIITIII ol danger line. Submerged reel _ __ L_ COMPILATION METHODS loose or light surface. one lane wide Li. W. L None Wreck. Sunken; Exposed . LL - I 4°45’ Photo-stereo Photo-planimelric Map 7777“" r _ 0 II on 111210 ZONE DESIGNATION: TO GIVE A STANDARD «EEERENCE 0N V ' ‘ . |:| Fair or dry weather. loose surface, two or more lanes wide WWWLWLWL Sunken Ioclis, Foreshore llals ,LL,L on 34 MM THIS SHEET TO [NEAREST 100 Mnms \\\\\\\V\\\\\ Fair or dry weather, loose surface, one lane wrde L . L L L Rocks bare or awash; Reef WWL . L a MiLs Iooooo M. SQUARE IDENTIFICATION SAMPLE POINT: TRAIL JUNCTION A. USHO Chart 6049, 1944 (reliability good>- Berg GLOSSARY mountain peak Cart IIBCIi; lrail L .L LLLL. WLLL .. ______ Depth Curves and Soundings In Fathoms L LRead letters menmm‘ 100,000 meter AerIaI photography: I'Feb" July 1946; Z‘Ian' 1949‘ Nom 8" bay Standard gauge railroad. Single track “himwfii —l—l—r— _ square In which the 170ml IIeSC P Oror en _W __L L_.__ L anchorage Reservoir, Darn, Ditch .LLLLL 2. Locate lirsi VERTICAL and line lolEFT oi Unun en ca e oint 5‘3"““1 E3“!!! 'a'lwadr double lTaCk m. Liwe. LP polnt and read LARGE figures Iabelmithe —— —- A» D r P ’ ” S It 1 LWLLLLLLLLLLWWW II Ih r b Narrow gauge railroad. single track WLLLL 2 ‘ a mum 0'5 APPROXIMATE "UN DECUNWON ”55 02::elljg‘tsgifiloo or «mom martin, or 43 2’6” ma crurzn or SHEET Estimate tenths from and line to paint: 9 Narrow gauge railroad, double or multiple track L .. LL Rice Paddy; Marsh LWLL ANNUAL MAGNETIC CHANGE I’ EASTERLV 3. LocatefirsIHORiloNTAL lrldllne BELOW . . . point and read LARGE figures labeling the Power transmissmn line LL. LWL LWLLLWLWLLL _L_._LLL. . .. u” diagram only 9., obtain numerical values. line either in the left or right mirlln. or Spot elevation in meters. Checked; Unchecked L W. LL 1 146 5,“ Nina; ° ' "" I° d"°""‘"° “"9”": "mm IIM' conned ”I. 16:01:: 1:2 SMrrIILER lixi'ues'uidany :nmilm lune"; dl 152 4 ‘ u K" "“1" er: 950 are or In In: slml slant 5 Tom r no to M: WaII; Levee; Cliff L W, V W % P"'°' PW” 'P °" "to south edge °I ”lo map the full coordinates, Use ONLY the I II I pm wy h | I '1] L led b' t ,3 1;“, Woods; Scrub ” "’7 """ “ with the value of the angle hem 6‘10 LARGER figures ol the and number; SAMPLE REFERENCE: ”1439152 aerw ee 0 ml ; 063 0 ice LW LLLLL. W. 0 NORTH and MAGNETIC Nogrfi a, plotted on "mp”: 815000 ll reporting beyond 18" in any direction I l ' l Principal MVIKAITOVI “EN 01 lighthouse: Anchorage WLL * 3/ Tropical grass; Coconut grove W. . LL.LL I:II:I the degree scale or me nor”! edge of the map. —- prefix Gnd Zone Desrrnahofl. as: ,56NLP439152 U DOT SW, CAROLI N E ISLAN DS 1958 IL TRUK ISLANDS ii 0 L N 1111 Military Geology of Truk Islands MAP 2 Geology and (x _ o o o o o o o CAROLINE IoLANDS 125,000 0 2 3 4 5 6 7 Water Reswces . Cb . 151°32’00"l 339 32/30” 340 ”41 342 343 35Ioo” 344 ON' 345 345 347 348 37'30” 349 350 151 39/3?” / ,, 7°22’001’" 1' 171 /°/1'% " ‘-‘ pMd , ‘ - 7 22 00 I 52 ' COMI 5 Coral reel . I .2 .. 1.2355 «13C . l 21 .. - 15 l 23 I 5/§ ‘ :'_:' 19 I '3, /3r» I f: . 60411; m I as“ 2 i '=1. a 15 1,;- I .1 314 .4 . m 1 - 11:1 1 WATER RESOURCES TRUK ISLANDS 18 1 ° , 1 > 22 21 -.' Coral . i z ‘ Coral ‘1 I1 ‘ i3 21 EXPLANATION ‘ 23 ‘ coral “'8' m....ci.i.'.—' 1 2 . _ 23 12 \, Spring flow in gallons per minute ® Rain gage \ ~~~~~ * 813 513 “— 0 Well or waterhole © Stream gage .3 J @/ Stream (number refers to table below) Stream discharges, T01, January i955 I stream number million gallons per day gallons per minute /—L\ l 0.16 112 <;;> l 2 0.003 2 , ’1 3 0.16 112 8 li 0.16 112 1 a}? 12 7 5 trickle .. 6 0.011:— 10 7 0 .003 2 8 0.001 1 9 0.006 Li 10 0.16 112 X 11 trickle _ ‘1 12 trickle _ (’1 13 0.16 112 14 0.0111 10 g 18 15 0.32 2211 ,. ,. 7 7 1 all 811 1 16 trickle _ R0; 1%". 1 »» l ENVAILSSHQN 20/00,, 17 * _l_/ 1.20 833 8 \ 16 #1, .1 , —~ 20,00. 16 * 2.22 1,510 4 x . 19 * 5.50 3,820 20 * 0.52 361 21 * 1.66 l,150 22 * 0.05 1150 23 * 0.001 1 2'4 * 0.10 70 25 * 0.117 326 . , . 26 * 2/ 1.96 1,360 54: $7,?” ., ‘ _ ., s4 1 310 810 __ 27 * 1.80 1,250 ‘ 111} ”W; 3/_,0\ 2; ‘2 28 0.02 13 I 1%): .51ng; K I f /"/\ 29 0.06 :15 ’ IEN WISENIF 1 30 0.10 67 / ‘ ® * recorded after heavy rain,- all others during dry weather l I; 7 22 I 3 . 6 4 AUWVI L48 122 l/ stream gage 1nstalled 1 March 1955 / 41 coral 2/ stream gage installed 15 March 1955 27 g I / I 23 . 3 - 1 2 \ i I 13 Q i / I < 22 \\ i ' 1 U \ 0 I 3 coral t, , 5 \ nun en . 1 ~\ 23 _ 2 1 1 , ((15 ml 14 j , ii ,,,,, 09,, , ,g _ , _ ; ,,,,, -. 809 309 - l ‘ Q9 K, (,x‘ l ‘ 1 7 o g/w i 3 1 ‘x, " 1 3 1 i1 18 22 I25 \‘x T R U K I I I ‘29 Icoial ‘7 ore Esand 23 \‘x\ I I 1 I l ‘ 2° GEOLOGY TRUK ISLANDS ;‘ ‘ x \ r i I x \\ 5 I coral 28 \\ I 1 11., ~ . . EXPLANATION » 1 \ \ x, 1 \ \x .33... I \\ ‘~ \ as 28 29 21‘\ , _____________________ 25 I 23 19 19 ‘1 K g \ 29 DESCRIPTION UNIT DESCRIPTION 1 ‘1 23 ‘x\ T \ ‘rm 808 1| 08 coral r [(313355 1 \ 3“ 08 ,1 , 1.3 I ‘ ‘ ., \‘\\\ _‘ur,_.‘_ an. 7 > I \J" W ‘T \ Undivlded volcanic rocks, chiefly basaltic and andesitic lava flows. 1.,1 M“ Fresh-water marsh deposits, unconsolidated muck and peat. i \x 1... 4.2;».- i . i 19 .18“ ’- 51:},‘5‘ _ I coral Andesite lava and autobreccia. $43: 13.3.91; Mangrovevswamp depOSIts, salt-water deposits chiefly unconsolidated muck and peat; : “‘ “ " ‘ calcareous sand predominates Iocall . y 25 Trachyte lava and autobreccia. I I Earth fill, largely clay and crushed volcanic rock. Basalt lava and autobreccia, most of which is olivine basalt (that is. COntains more than 5% olivine). 35 SYMBOLS / 307 .. .1 07.. Nepheline basalt lava (nba) and melilite-nepheline basalt lava Imba). "T" 807 30 Stnke and dip of bedding Tuff, largely lapilli tuff, although thin beds of fine~grained tuff occur in a few places. _ E A k d d f b dd I pparent sol e an in 0 e ing \ Volcanic‘conglomerate of variable proportions of pebbles, cobbles, and boulders of "V3_o Strike and dip of dike volcanic rock, chiefly basalt and andeSIte. 27 + Strike of vertical dike $3.. br Volcanic breccia, angular blocks of volcanic rock in a finer grained matrix of tuff ., ,- i, and angular volcanic_ debris. Basalt and andesite blocks predominate except on . , , , __. 17.30,, 17 30 \ Udot. where trachyte blocks are abundant and basalt blocks are relatively uncommon. + Strike OI vertical lomt Through rounding of the blocks. volcanic breccia grades into volcanic conglomerate. \\\\ Contact, dashed where approximately located -_.._ 8 805mm.” 06 ----- ~ 05 Gabbro~rich breccia, occurs only on Udot. ________ | d f' 't t t _____ I§_ ~~-, n einie con ac coral _____________ _ PA CIFI C 0 CEA N 355 Beach deposits, unconsolidated beach sand and loamy calcareous sand bordering the ——‘7 _______ Doubtful or probable fault, dotted where concealed beaches 47; , . . A Geologic cross section 3 711700” I \ I \ t ‘ I I I / \I I 7°17/oo” 151°3200“ 339000m.E 3230” 340 341 342 343 35’00” 344 345 346 p 348 3W30" 349 350 351 351“39GO” 347 W855 '* Scale 1:25.000 _ Edmon 2.AMS (AWE) 1 1 0 15mm“ We Geology by John T. Stark, Richard L. Hay. HafOld G- Mall. and Elmer us. ARMY MAP SERVICE, FAR EAST . 57.041 - R15 . 11,158 - 3.40 E r , , } , I ; D. Patterson, 1954-1955. Water resources by Max H. Carson, 1955. Prepared under the direction of the Engineer, Hq AFFE/SA. by the U S. Army Map Service, Far 1000 500 0 1000 2000 Meters . . . . . r l>--—{ 1—i i—«i i—i i—i r—-——————-——————i East. Compiled in 1957 by photogrammetric (multiplex) methods. Coastal hydrography compiled 1000 500 0 1000 2000 Yards from USHO Chart 6049, 1944. Horizontal and vertical control established by Corps of Engineers, I H H H H ,,_, . fl 1951. Names transliterated in accordance with rules Of the Us. Board on Geographic Names. 1 g 0 ”hum“ Mile Maior roads are classmed by reconnaissance by the 64th Engineer Battalion(BaseTOpograpnic), . Ir . _ 1 COVERAGE DIAGRAM INDEX TO ADJOlNlNG SHEETS 1952. otner roads are CIaSSlIled from source maps and aerial photography and are not verified by reconnaissance. Coastal vegetation are classified by recorinaissance by Military Geology . \ , Branch, Intelligence Division, Office Of the Engineer. Ho AFFEIBA, with personnel of the US. CONTOUR INTERVAL ‘0 METERS \ \\ \\ \ §\ \ \ \ \\ \ Geological Survey, 1955. Map not field checked. VERTICAL DATUM' MEAN 5“ LEVEL \\ \\ \\ \ \\\\;\‘\ 4544 ” NW . \ ‘ \\‘?\ \ MAP 5 Geologic and water resources data based on on field investigations 1954-1955 by Military Geology TRANSVERSE M ERCATOR PROJ ECTION \\ \ \\\\\\\\\\§§\\‘\ Branch, Intelligence Division. Office of the Engineer. Hq. U. 8. Army Japan with personnel of the HORIZON“ DATUM ,5 BASED ON THE ASTRONOMIC sum)“ NO. 2 (195, ), \ \\ \ \\ . . Geol ‘ IS e . ' I J ‘1 I , ' . . \‘F"‘\\\ v. U S 08ica UI’V y ' ISI 53 34.“ EAST OF GREENWICH, 7 7i 37 7 NORTH \Wigw‘§\\\ 4544 III SW 4544 III SE 4544 II SW ' J “N\ ' \ \ LEGEND HYDROGRAPHIC OATUM. APPROXiMATE LEVEL OF LOWEST Low WATER Mk \iQ‘kwx \\\\ MAP 1 MAP 3 MAP 6 R0405 BLACK NUMBERED LiNEs INDICATE THE 1.000 METER UNIVERSAL TRANSVERSE \ A], mm, uERcAToR GRio. ZONE 56, INTERNATIONAL SPHEROID A THE LAST THREE DIGITS 0F TRE GRID NUMBERS ARE ouiTrEu \\ 4543 IV NW 4543 IV NE 4543 l NW hard suriace, two or more lanes wide ,1 , ,, None Built-up area on \ ' MAP 2 MAP 4 MAP 7 loose or light surlace. two 01 more lanes wide None Church: School. Cemetery ,1 ,, 1., , hard surface, one lane rude , , None liniil ol danger line, Submerged reel COMPILATION METHODS loose or light surface, one lane wide None Wreck Sun-lea. froosed _ r “‘5, Photo-stereo PhotoApIanimetric Map oii ‘ 0R , -, fair or dry ueathei. loose surface, two or more lanes wide 1:117:27 : Sunken rocks; Foreshore Ilats ,, ,, 0R ._ 3‘ “L5 GRID IONE DISIGNHION' Le]EI::EAUSTT;N::::E:TE2:135: m fi I I' . I I B GLOSSARY ‘ _ k a . . erg ,Wlil,,,,1,1_,11,,____moun ain. pea Fair 0! drv weather, loose surface, one lane VIKIE 1 . Rocks have or awash: Reel 3 “”5 100,000 M. SQUARE IDENTIFICATIUN ‘ SAMPLE POM? TRAIL JUNCTION l A. USHO Chart 6049, 1944 (reliability good), Nom an n bay Carl trarx. trail , ,1 , ., ,,, ,, _.__._1_ .11 Depth Curves and Soundings in faihcms ,1, , , ,1, _ ,4 Rear: We” “may,” 100,000 mm, 1' I Aerial photography; I'FED-I JUIV 1945i Z'Feb- 1947' 8:331“ #—_—-__-Wri—.~_k»fic:3: (:35: . i 1 in whl 11111 1 ll , LP .__1..-.__.111,V11._ 11.1. , Slandad gauge railroad, Single track ,, —-t—0—0— Reserve"; Dam; Ditch ,_,, _ ,, .. ,1 2,12::IeelirslVERTIgApLo;idIIISnelo LEFT or I Standard gauge railroad, double tracli 11.11.... , , LP W'“ and ”3“ LARGE “EU'ES “WW“! I 3"" Sill “399mm; 1, 71111W1_i line either in the loo or bottom margin, or Narrow gauge railroad, single iracli ,,, ,,,,, , , _,_i__,_ __ APPROXIMATE um DECLINATION 1955 on the line Ilse": 48 . z’o“ . FOR CENTER or SHEET Estimate tenths from and line to point: 9 Narrow gauge railroad, double or multiple lracli fir-—-“—1v— R,“ Paddy; Marsh 11.... 1.1,ii “ “ «it i ANNUAL IAGNEYIC CHANGE l’ EASYERLY —— 3. Locate first HORIZONTAL R'ldIlne BELOW . [l ‘ point and read LARGE figures labeling the Porter transmissron line .. . , _ ,, ._ , .1 L .21.. c _. ./ (j 0" U3; diagram only to obtain numerical rail“. line either in the left or right margin, or ‘ 4 fig . . . IGNORE II SMALLER r. r i : Spot elevation in meters: Checked; Unchecked ‘I46 .I“ N'pa' Mangrove "“"""’"*””” "W'i To determine Tow" north 'm' (M ”I. and nunIbzr; these areKIrItslindaiII: EngziengnreeIIt‘riesnfrom grid line to point: 111 Wall levee Clill % DE P"°' 90"" "5' °" "*1 ”0'“ “9" °'”" MP in. lull coordinates. Use ONLY the , , ,1... _...- a: ‘1 Woods; Saab 171,, W/ViAfli ”m. ,“ m," o, ,5. angle “A"... can) URGERriruiesulme iivid number; SAMPLE RirERENCE: LP489111 ' "3"”"9" °' m“- “”3“?" ”bit“ ,1 0 “w NORTH and MAGNETIC Norm-i, a: plotted on "“9": 806000 ii reporting beyond ia° in any mimic... , Principal navigation light ol lighlhouse; Anchorage ,1 * \I/ Irooiul grass; Coconut grove ____ 17* [:II: ”redeem Irate of the M 0‘’9" 0’ "h WP- — We” Gm 1°” Dewnmon' as; SGNLPMSQHI TOL NW; CAROLI N E ISLAN DS 1 958 TRUK ISLANDS CAROLINE ISLANDS 125,000 Military Geology of Truk Islands MAP 3 Geology and ()7 43 5° 6C 7° Water Resources r I LLIJ L.I.;I.I_i.r.I..LiI,I..I_LLII . 153739-30” 352 40001353 354 355 356 357 42/30! ”'60 361 362 45Iool 363 364 365 151°47rooi 7°27’Cl0’" i i 30 E 29 ‘ E l 7'27’00” E. I 1, coral I I E I 23 I E 34 I I I coral E 24 coral i I I l 30 ; x’5x 26 E I E coral E , E 32 7/ 5 \‘E E coral 34 E I E . 27 E coral E, P; E E 1 l I 29 I, /I ‘3 I E E : 21 . \-_./’ I I E I coral E 27 23 I E 1 . E 7 aa _.L,. La _ ,. VW.-- . . ,_--.---#,- W32 . . - - .c - M ”L--- 23 — __v.,._..,,2.,.,-.,,s.,fl. mm .2 -- . , . ~- - - 873 523 ISLE E "723‘ T ’7’ 7777 T T T coral \ 23 « L I E 5 fl. I 29 ’ .I I coral I I . . 30 , I 3° 3‘ ‘ T R U I K L A G O 0 N I I 31 i i , 25 i E E 30 I g, ; cggal I ‘ 28 E : 17//\, E I 31 t E E 29 E/ / [I E’ 27 coral 24 E 27 7/ 7/ (/7 \\ coral I i I 28 ,I » I/ I coral I H, 7 W. "7,",ififigkmfl. ..__.,-..., I . I..,_..,,,,. ,,.,._ W.-. 8’) $22 22 » _. ~ ~ * * * 22247" * I 7 , I I 22 I *1 ‘2 E I , . 19 I \\ L—L/ I I , I I I L—_l indicates swept depth area in feet I E 1 I -~. »I AI 21 I I.“ . I oz 03 54 63 E31. , 3 E , . 21 I I I 4,,» E 23 \e-‘ , I I t . ::f.':-C°”"”' ‘, coral TRUST TERRITORY OF THE PACIFIC ISLANDS 23 . E E I “\~\_/ (U.S.A. ADMINISTRATING AUTHORITY) ‘I “’“l 28 E / 16 , I . E , 1’ x I “ GEOLOGY TRUK ISLANDS s 2321 _ . . 215,-, E _, , W , . _ , 21 . \ 1 coral 7 a ,..,,._, 21 l \ I E 3_3. 12 16 2; 22 21x I 25 i / x I 7/7”“. coral 24 I 23 1 IO E ./E a; EXPLANATION I coral 20 18 b 13 \t I ‘ coral E r \ I t2_5.r / I g 11 ”fit-Tire San ,Tslef Ever , I I 55" 17 Agog, E x E UNIT DESCRIPTION E6 ‘5,~\\ j l I VOI Undivided volcanic rocks, chiefly basaltic and andesitic lava flows. \ A \\ E . 17 I 12 24 / ’\ \‘escffhmk I°—/ I I I ‘ / / \ ‘x \ 31 I I “'3' 15 I [,Q/ \ \\\ ‘~ \ 8 12 (13» 17 14 E I Andesite lava and autobreccia, ,5),ch I M l ___. 826 I 20 2.. u --------- «mi ,' " 25/00” . :\ E21 21 Trachyte lava and autobreccia. / 23 E //////;/Z% Basalt lava and autobreccia, most of which is olivine basalt (that is, 'contains more ,4 4e , " is“ 4% at :32: 4 “1,0 / gTRU K I SLAN coral than 5% olivine). i i I l I I I Nepheline basalt lava (nba) and melilite-nepheline basalt lava (mba). E E 16 I4 Tuff, largely Iapilli tuff, although thin beds of fine-grained tuff occur in a few places. E .7""- Coral reel ,_ 23 coral E Uhun en Ch'dsia o . . . 3 819 I 7' _ w » Volcanic conglomerate of variable proportions of pebbles, cobbles, and boulders of ,2. “a 19 E " E volcanic rock, chiefly basalt and andesite. / /5\\ \E/o Volcanic breccia, angular blocks of volcanic rock in a finer grained matrix of tuff E, 4 \ 7’7 21 and angular volcanic debris. Basalt and andesite blocks predominate except on E 2 cggE Ii / EE Udot, where trachyte blocks are abundant and basalt blocks are relatively uncommon. l E \L‘i/ E/ Through rounding of the blocks, volcanic breccia grades into volcanic conglomerate. I r; I 17 .2 - 15 i . . 18 16 . 13 16 i 18 Gabbro-rich breccra, occurs only on Udot. cm, i I =._ _.-' IE E E I ; 13 Beach deposits, unconsolidated beach sand and loamy calcareous sand bordering the I I I : I 15 I, E I I E £5 11 E 15 Fresh-water marsh deposits, unconsolidated muck and peat. WATER RESOURCES, TRUK ISLANDS I a / Mangrove-swamp deposits, salt-water deposits chiefly unconsolidated muck and peat; E 21 44 2E2 15 calcareous sand predominates locally. I I 62) III EXPLANATION sand and shells sand and shells 13 \la lElé Earth fill, largely clay and crushed volcanic rock. EI SYMBOLS DESCRIPTION SYMBOL DESCRIPTION I I 1' Spring Water tunnel 1; 12 8 E; r—~—I . 817 17 -‘—“““‘"""’ ”E ”'“W” @9913! Spring flow in gallons per minute \ Rain gage “5 I /\ Strike and dip of bedding El 0 Well or waterhole I.» Stream gage E E Apparent strike and dip of bedding E I Stream (number refers to table below; I I , E I I . . . E 3 Strike and di of dike 21 18 E 56 1‘ cigal p l a ,y I I. Stream dlscharges, Udot, February 19 11 Strike of vertical dike I, stream number million gallons per day gallons per minute \E l 0.001l :3 Strike of vertical joint I \E 2 0.0.01 ; , 316 816 ’“"E“”“_—“—WVT““ 3 J 013/ :9 “ EJ ‘ ‘ W‘ Contact, dashed where approximately located __ ' I \ I . I A... I T I . p _______ \E if I‘J'OUl J7 OROTlE FASAFA_._ E 332013833 ““““““ Indefinite contact 18 \ 7 L) .0014 3 sand , _:I:’ ,0 ‘\ 6 it QT [I ,\ I I ,J. *l 1U Doubtful or probable fault, dotted where concealed 17 'i’ O . one 4 12 E ,3, Ev... r‘Kle cm 17 Geologic cross section ,/’ / [0‘ 22/30' — /o_\ ~ “A“ - , COLE—— 22'30' 9 0.009 6 \ , a //»_4,,_..._«» 1 E x 12 kj / (is; ,,,,,,,,,,,,,, ‘13 L0 0.03 2c) (173-..- \EEiEE ll seep _ \\ X l” \E\, 16 8 815000m.N .V d seep __ E 15 - . . . \o 12 ail (luring dry weather 3 0% 1 , . I I; 1 ’ I x. E E i0 11 /3 13 ,E 2E (/_ 7\/ \o E E l 17 7 \ I, 15 12 ‘ E \ E E 61\I 21 61 O 13 E 18 I coral 15 E E 8 CW3 :E 2/, M 13 I 13 1k \ E E 12 Coral . shells 15 3 t5 I Coral 7'22’00! + I \ I II 3 I I M 7°22'oo” 151°39’30” 352000m.EE 4000' 353 354 355 356 362 45’00” 363 364 365 151 '47’00” W8555 Scale 125,000 Ed't'°” “MS IAFFE’ 1 2 0 IStatute Mile Geology by John T. Stark, Richard L. Hay, Harold G. May, and Elmer US. ARMY MAP SERVICE, FAR EAST- 57-041 -R«15- 11/58 - 3,40 ‘ * I D. Patterson 1954-1955. Water re ur b Ma . . Prepared under the direction of the Engineer, Hq AFFE/SA, by the U.S. Army Map Service, Far 1000 500 0 100° 209° Men“ I SO ces y X H Carson. 1955 East. Compiled In 1957 by photogrammetric {multiplex} methods. Coastal hydrography compiled I 1000 500 0 1000 2000 Y d from USHO Chart 6049. 1944. Horizontal and vertical control established by Corps of Engineers, r r—r E_, E_, E__, E_, : ar 5 1951. Names transliterated in accordance with rules of the US. Board on Geographic Names. _ _ Maror roads are classrfied by reconnaissance by the 64th Engineer Battalion(BaseTopographic), 1 0 INauticaI me 1952; other roads are classified from source maps and aerial photography and are not verified T I l A T T ' COVERAGE DIAGRAM INDEX TO ADJOINING SHEETS by reconnaissance, Coastal vegetation are classified by reconnaissance by Military Geology Branch, Intelligence Division, Office of the Engineer, Hq AFFE/8A, with personnel of the u.s. CONTOUR INTERVAL IO METERS WITH SUPPLEMENTARY CONTOURS AT 5 METER INTERVALS Geological Survey, 1955. Map not field checked. VERTICAL DATUM: MEAN SEA LEVEL 4544 ll NW , MAP 5 Geologic and water resources data based on on field investigations 1954—1955 by Military Geology TRANSVERSE MERCATOR PROJECTION Branch, Intelligence Division, Office of the Engineer, Hq, U. 8. Army Japan with personnel Of the HORIZONTAL “TU" '5 BASED ON THE ASTRONOM'C STATION N0, 2 (”’5' )' W U. 8. Geological Survey. Isr'53’34.3' EAST or GREENWICH. 7'21’37.7' NORTH “Qty-g‘xezg'» vs §0®§2§ 4544 III SW 4544 III SE 4544 II SW LEGEND HYDRoGRAPi-nc DATUM : APPROXIMATE LEVEL OF LOWEST Low WATER ‘5‘:sz ~.\\“\\\\‘\§‘\ S®m§§§k \ E \ MAP 1 MAP 3 MAP 6 . ' \‘$\\.' ‘ ROADS BLACK NUMBERED LINES INDICATE THE rooo METER UNIVERSAL TRANSVERSE \§®{§W\% \\ A” mm, MERCATOR GRID. ZONE 56. INTERNATIONAL SPHEROID §§§§$¥$R NW E hard surface two or more lanes wrde None Bum-up area None THE LAST THREE DIGITS OF THE GRID NUMBERS A" oumED ":\‘\:‘{§s TR“ “QT \ 4543 IV 4543 W N 4543 I NW , 77* L we , , . cu \\\\\\\\\\ MAP 2 MAP 4 MAP 7 loose or light surface, two or more lanes wide i, None Church; School; Cemetery ___.i.i7) . i 5 Ice”. ‘{\\\\\\\\\\\\\\\\\\\ E . . . . _ hard surface, one ane Wide 7,, A . 7, None Limit of danger line, Submerged reel .,,.,,,,,. + 4.45, COMPILATION METHODS loose or light surlace, one lane wide _, LLLL None Wreck: Sunlien', Exposed A L," as, 4* Ar: 0_Eo, on Photo-stereo Photo-planimetric Map F ' a m ,l r ,t l 'd 2 , + . s a u iiiiLs GRID ZONE DESIGNATION: To GIVE A STANDARD REFERENCE ON V . air or ry wea or 0059 surace we or more anes WI 9 Sunken rocks, Foreshore flats _._. A _A_.. *+ in on THIS SHEET To NEAREST 100 METERS mm , _ __ 4 , GLOSSARY Fair or dry weather, loose surlace, one lane vride .,., :::::::: Rocks bare or awash; Reel W..., L— \ * 3 “II-5 100.000 M. SQUARE IDENTIFICATION SAMPLE POINT: I SCHOOL A USHO Chart 6049 1944 (reliability good). 3:3:ng CZZZMS§E , . A. . J ]1 ' ’ - Cart track, trail , ,,.7,.. ______ Depth Curves and In Fathoms 15" 2 mm Em": ”mm,“ 100.000 mm, Aerial photography: Feb., July 1946 St d d l d, l l k “w . 7,, —O—t-—-+-— , . squarein which thepomt lies: LP a" a' gauge ””03 5m“ I“ Reservorr; Dam; Ditch inwv CT,“ 2. Locate first VERTICAL gird line to LEFT of Standard gauge railroad, double tracli _._g 2 point and read LARGE figures labelingthe 2’s” Salt , ‘ m LP line either In the top or bottom margin, or Narrow gauge railroad, single track __ “L E T E APPROXIMATE HEAN DECLINATION 1355 on the hire itself: 589 . I. I A T " FOR CENTER OF SHEET Estimate tenths from grid line to point: "3"“ gauge ”WWI “WW 0' "IUIl'P'e "39k 7 Rice Paddy; Marsh u A .- ANNUAL MAGNETIC CHANGE l’ EASTERLV 3, Lacatellrst HORIZONTAL grid llne snow . . E,’ paint and read LARGE figures labeling the Power transmrssron line _. L, c__.-___ . .. u... dogma. only 1° obtain numerical values. . line :Illlel In the left or rlzht margin, oi Spot elevation in meters: Checked; Unchecked * I66 ‘rcs "WI ° To deremii'ne magnetic north line, connect the IGNORE n" SMALLER I'm” ‘7' '."y °" "'"me'mm 16 . . ., ,. illd "UMN'I these are TM Tlfldlfll Estimate tenths from grid line to paint: 4 Wall; Levee; Cliff ¥i_._...._.___._ _W%‘§ DE P'VO' PO'M P on ”W ”0'“ 049° °' ”'° '"°P the ruil coordinates. Use ONLY the WI h l I 'll L td b ’3 Toner WW5; SCrub —_* with Me value a! the angle beMBofl GRID LARGER figures of the grid number; SAMPLE REFERENCE: LP589164 aerw ee 0 mi; ocae o Eect 777,7, ., 0 example: , ,. . , . NORTH and MAGNETIC NORTH, as plotted on 815 000 ll reporting beyond Is in any direction, Principal navigation light of lighthouse; Anchorage _ * 3.; Tropical grass; Coconut grove —__, I:I:I “6.9,“ ”ml; or me nor-oh edge of rho map. ‘— ”m” 6"" 1°" D”"""’°"' '5: 56MLP589164 U DOT SE, CAROLI N E ISLAN DS 1958 Military Geology of Truk Islands MAP 4 Geology and Water Resources ”I“ *0 III \ I?) 0. 2° 3., .0 l TRUK ISLANDS CAROLINE ISLANDS 125,000 I I LLALLAI LL14. LL 15139801352 40/00” 353 354 355 356 357 42/30” 358 359 360 361 151”47’00” . r. I 72200” 7 22 00" i 1 . i 3 I 3 K , 7 12 Coral I ‘ 7 I 18 I 16 17 SJ I 22 ’a/ V I l 11 11 o 12 11 x"\ l I \ 3 \i 15 i 4I I I 1‘ ‘ \\V 16 I 2 I \\ 3 13 I 5 ,1 1‘ 14 / \ c 814 l3~7~ \‘22 I\ 14 _ W , .. H C: \7’ ” \ _ ,3.” I 7 I \I I 17 11 c0,... 15 ' ' him 'I xm \\ 17 l I ‘ ' ' ‘I I coral 3 1 12 7 \\ \\ —\, I r \\ 1 \\ \\ W 21 0/ \ 12 I \ i 2 \coral I \\ 5 .74 16 I , , 0 \\ (:l 21 \\\ I 10 L,’ \ \ I l I @o \2/ 12 16 I ‘I 13 92!“ L 3 ‘ ‘ 13 coral I \‘I «9 3 12 ca: 23 ‘0/ 241) , Em 813 7 7 7 7 . . _ , , I , 1 (0/ - , ‘ - l \ \ ' ' . . . , . . . , 23 I i 17 / / / OROR EN 41 . . . . C I / 3.) I .32.. a k 8 IV}. 1. ‘ , ." I ‘1‘ k, \5/ I calirgal 17 I I I \ I {I / II . , i ‘ \\ I 20 ‘ O ’. ,‘5 ' ,. I \\ ‘ 22 I 9 2 ' ' i5 56 \17 57 58 mi 59 6O 6 \\ / 7 ,7—~\\ \‘\ 22 colrgl ‘lo //@I fig \\ I I I 'i s / \ 2 I 24 \\\-// \\ 3/ 2 colrzai I7 \ rorai 812 I 777 77 777 ., 7 77 , I 77 , \ I I I I , \ I 6 I I 20 I a/ I I S L A N D S 5 I , I is I I I 2 ‘I I I_.. indicates swept depth areaIin feet I 17 \I I I I \‘ 15 I I \‘ 1 i 3 ' \\ coral l 24 I 14 1.2.5 ‘I ,v coral I /7—\ I ; 16 \‘f 4 \‘ \‘i l l GEOLOGY TRUK ISLANDS 1\ [I 9 81 _ _ \\_:: __ colral LE... _ A, *1 23 2, EXPLANATION 20100.” I I i 22 5 I l 3 21 5 15 | I 33 UNIT DESCRIPTION I L_. i I T R ’U G 0 0 N VOI Undivided volcanic rocks, chiefly basaltic and andesitic lava flows. I 23 I : I 27 - , I I ’ 1 ”'3' Andesite lava and autobreccia. 21 I " 2 29 I I I 23 ‘ 8 g 1 O I I 1 ’ Trachyte lava and autobreccia. 10 10 o I z \ II 30 >§\ I\\ V I 22 I \ / , . . . . . . . , H i I \ /W Basalt lava and autobreccra, most of which is oliv1ne basalt (that 15, contains more 22 //@\ 23 , I \ ' TRUST TERRITORY OF THE PACIFIC ISLANDS than 5% olivmt 4 ‘I\ 5 K , I \ 18 (U.S.A. ADMINISTRATING AUTHORITY) , . , \ ,, L , \V/ 22 I I \ > F50 ‘ mbo Nepheline basalt lava (nba) and meIilite-nepheline basalt lava (mba). 55 ‘--—‘ , l ‘ , g I 18 i ‘ l I \‘I ‘ 17 27 . 19 ‘ II \ Tuff, largely lapilli tuff, although thin beds of fine‘grained tuff occur in a few places. , I II 18 X ‘ I I, \ I 7 /‘1~\ , II \\ I ; Volcanic conglomerate of variable proportions of pebbles, cobbles, and boulders of 1 I {I 1‘ II I I \\ I 23 fl . 7 ,, volcanic rock, chiefly basalt and andesite. . W." E... 809 809 , , .. .i \ I, 09 I I I .. ~ , a” ,,,,k ' . 24 ‘7“7’ I I \\ 19 I I I' \I’ I Dr Volcanic breccia, angular blocks of volcanic rock in a finer grained matrix of tuff L/x’l 23 I\\\ I ‘I I .__I indicates swept depth area ir feet and angular volcanic debris. Basalt and andesite blocks predominate except on 28 22 j [N ____________ ’ I \ I \ 24 29 Udot, where trachyte blocks are abundant and basalt blocks are relatively uncommon 24/ l \\ I 19 I \\ I Through rounding of the blocks, volcanic breccia grades into volcanic conglomerate. ’ \ I I \ 1 r I , \ l AB. 2‘ I / , 1 ‘ I G; /l , X I ‘I I 21 Gabbro-rich breccia, occurs only on Udot. _______________________ r! X 21 I a“ ‘ TTTTT ’l i \\ I I I ,_2_9, \“*\\E\ II ‘ 21 \ 3 l 23 Beach deposits, unconsolidated beach sand and loamy calcareous sand bordering the 23 74 \\ ”3’ beaches. 19 x , I g ”,.-7’-""' ggggg 2 TAI O8 , U... i ._. \ \\ I . L .,.,. .. ..... - .,_ . MN. 808 ‘08 1:: —'—’>""’ " " ‘ "'7" T i \ \23 19 I 29 Fresh-water marsh deposits, unconsolidated muck and peat. I 22 \\‘I\ 7 , , 20 ‘ coral \\\\ , I I 33 I 21 \\ ‘ I I -—i Mangrove-swamp deposits, salt-water deposits chiefly unconsolidated muck and peat; \\ I ‘ l calcareous sand predominates locally. 21 x I . 52 532 5?; 19 55 23\ 56 57 58 f Earth fill, largely clay and crushed volcanic rock. 27 4 , \ ‘ ‘ w 22 i ,, 1 WATER RESOURCES, TRUK ISLANDS ”W I I \ i I 11 I l X 'I 4/ I i ‘ \ SYMBOLS ' . / I; , é; ; EXPLANATION i ‘ E ‘x , I _I_. EEAAEAW __, 8 807 ,. L, .. I . \ x 7T 30 Strike and dip of bedding ' 07 5 _ I 19\ ; 17 SYMBOLS DESCRIPTION SYMBOLS DESCRIPTION I 16 (IS and) “'37.; Apparent strike and dip of bedding 21 ® , 19 f Spring g2 Water tunnel I0 I 21 W3— . . . ‘ 19 coral EELS] Spring flow in gallons per minute C) Rain gage 0 Strike and ‘1'” 0f d'ke l_J indicates swept depth area in feet j ,__ . . . I 0 Well or waterhole LS) Stream gage .9— Strike of vertical dike 30 23 I . coral 24 Cal“ , 18 l @n/ Stream (number refers to table below) —I— Strike of vertical joint 17130" ~ —-I—~ i , i - “x- — 1700" I I j \\\ \\\ Contact, dashed where approximately located ‘ l . > 8 8050mm.” 1 25 O6 . \ 21 Stream dlscharges, Fala-beguets, February 1955 __ 06 21 \\ b . . x 1 """"""" _\ Indefinite contact 23 sand 29 27 \\ stream num er mllllon gallons per day galLons per minute 29 \\\ ‘1; l 0'00)“ l -_‘,?‘---._ Doubtful or probable fault, dotted where concealed , 1 13 \ 2 0.009 6 & I I 23 41 " 22 ! ‘\~\ both durin dry weather A————A’ Geologic cross section 25 ‘ I 4 I \c g I I i 1 “3'3“ 1 com I 16 cf” I/’ , K , 25 \“\\ I 23 ,r' I I 24 , I am. I 28 2I 3 \\‘~~c\ I II I 30 i coral 27 7°17IOO” AER 15 I "5 Y‘ 17 I f \ 24 “‘4. 22 Gr}: I II I I 7117/00” 151’39’30” 352000m.E_ 4000” 353 354 355 356 357 42/30” 358 359 360 3g1 362 45’00” 363 364 365 151 47’00” W855 '5 Scale 125,000 Edition 2AMs (AFFE; 1 E 0 lstatute Mile Geolo b John T. Stark, Richard L. Ha , Harold G. May, and Elmer U.s. ARMY MAP SERVICE, FAR EAST - 57-041 - R-lS - 11/58 - 3.4c 83’ y ‘ ‘ i i ‘ " ‘ i ’ i i 0 o 2 00M I D. Patterson, 1954-1955. Water resources by Max H. Carson, 1955. Prepared under the direction of the Engineer, Ha AFFE/BA, by the US. Army Map Service, Far 10‘00 500 O 1 0 0 e erg East. Compiled in 1957 by photogrammetric (multiplex) methods and from 1:55,180, USHO 1000 500 O 1000 2000Yards Chart 6049, 1944. Coastal hydrography compiled from USHO Chart 6049, 1944. Horizontal and I 1—1 1—1 1—1 1_I 1—1 , , vertical control established by Corps of Engineers, 1951. Names transliterated in accordance 1 I. 0 lNautical Mile with rules of the Us. Board on Geographic Names, Coastal vegetation are classified by reconnaiS- . _ . 1 . .r I I I . . sance by Military Geology Branch, Intelligence Division, Office of the Engineer,Hq AFFE/BA,with personnel fth U. . I ‘ ' AM INDEX TO ADJOINING SHEETS ° 6 S ““9““ Sway! 1955- Map mi “6” chm“ CONTOUR INTERVAL IO METERS WITH SUPPLEMENTARY CONTOURS AT 5 METER INTERVALS COVERAGE D'AGR VERTICAL DATUM: MEAN SEA L"VEL \ W . t \ \\\\ \ 4544 ll NW Geologic and water resources data based on on field investigations 1954-1955 by Military Geology Branch, Intelligence Division, Office of the Engineer, Hq, U. S. Army Japan with personnel of the TRANSVERSE MERCATOR PROJECTION \ \ \ MAP 5 U. 3. Geological Survey. HORIZONTAL DATUM IS BASED ON THE ASTRONOMIC STATION NO. 2 <195l ): \ isr’sa’ua” EAST OF GREENWICH. 7"21’37,7/’ NORTH \ \ \ 4544 III SW 4544 III SE 4544 ll SW HYDROGRAPHIC DATUM : APPROXIMATE LEVEL OF LOWEST Low WATER LEGEND \\. A MAP 1 MAP 3 MAP 6 ROADS BLACK NUMBERED LINES INDICATE THE 1.000 METER UNIVERSAL TRANSVERSE \ \ AII weather MERCATOR GRID, ZONE 56, lNTERNATiONAL SPHEROID hard Surlace two or more lanes wrde None Burlt up area L_E,AA‘E.______.,V __ GN THE LAST THREE DIGITS OF THE GRID NUMBERS ARE OMITTED \ \, 4543 IV NW 4543 IV NE 4543 I NW IIIQSP or lIgnl surtace, two or more lanes Wide None Church, School, Cemetery We; MAP 2 MAP 4 MAP 7 hard sur‘zce one lane mil? _E.__.___i NONE Limit ol danger Iiiie, Submerged reel _____ w o \\\ \ loos» 0r Irght surlace, one lane wide E». . None Wreck Sunken; Exposed _4,___ o I “‘5’ COMPILATION METHODS ° '0 0" GRIO zorIE DESIGNATION: i , fan or dry weather, loose Suilace, two or more lanes wide Sunken rocks; Foreshore llats ______ OR 54 MILs 56N IT'SIg”SI:EAETSTDN::ARR[)E:TEFIEI12EME§E?I: Photo-stereo _#¥Map ____ Farr or dry weather. loose sorlare, one lane Wide W- Rocks bare 0r awash, Reel __A,_E 3 ”ll-5 100,000 M SQUARE IDENTIFICATION SAMPLE pomr» x 112 §\\\\\\\\\§ I J GLOSSARY I» t - . ’ ._i,..,._.. Oror en anchorage ”a” ’3“ ”a” ___m_...w.__L ~_____ Dem“ CW“ 3"” ”‘ ”moms 1.11m letters Idenmymr 100,000 meter LP A, 155,180, usno Chart 5049, 1944 (reliability good), Unun en cape point , . . . —i——I~——+— rI rim tl : w,_._w___ , WM We “0“ We "a“ #M Reservon, Dani, Ditch __...____ I3:3:IESIJERTIEADf':,,d’ffm,0LEW, I Aerial photography: July 1946. _ Standard gauge rarlmad‘ double track __‘____ —++—0+-—«-— LP point and read LARGE ligures labeling the I 2/6” Salt line either in the top or bottom margin, or ‘ Narrow gauge railroad, Singie track __i___,v --r-—‘-—r— APPROXIMATE MEAN DECLINATioN 1955 onthelmeitseil. 53 21’s” FOR CENTER OF SHEET Estimate tenths Irom grid line to point: 5 Narrow gauge railroad. double or multiple track v—w ‘W—“fir‘ RIce Paddy; Marsh ___._. ANNUAL MAGNETIC CHANGE 1’ EASTERLY 3. Locatelirst HORIZONTAL grid line BELOW P I l ’ . _ . paint and read LARGE ligures labeling the I ower iansmiSSIon Ine _,__- M ________ Use diagram only to obtain numerical values. line either In the left 01 rIght rrrargrn, or I Spot elevation In meters‘ Checked, Unchecked .L-- " ms "ras Nipa; ”“wa 7° delem’ine "loam“ "0"” ""9, ”Med "'0 :IZOSEWIBSmisLeEZrZK‘ILfSIxJK :"IWI'": :32”; m I t I 134 r 1 ll rr 1 S Il'l'lfl e E 5 rom ll me 0 Girl I Wall LEI/Be Clill - §E§ 9"“ porn! P °” the ”0’“ “’9‘ °f the map the full coordinates. Use ONLY the E p I , , ._ .-_-____._..-. —» mt: my Woods; Scrub VI", ".6 ”I“, or m. Mgr. Mm carp LARGER iirures 1:! the and number: SAMPLE REFERENCE: LP535134 Waterwheel 01 ”Mi LDC‘MEd Obie“ “#m " NORTH and MAGNETIC NORTH, ax ploflod on example: 806000 ll reporting beyond18°ih any direction, KL Tropical grass; Coconut grove __—_._ “v L__I the degree scale at the north edge of the mp. _. ””7” GM 1°" ”WWW“ as: 56NLP535134 TO L N E, CA R0 LI N E IS LAN DS 1958 Printipal navrgation lIght oi lIghthause. Anchorage __ * TRUK ISLANDS MOEN NW Military Geology of Truk Islands MAP 5 Geology and . o o o o CAROLINE ISLANDS 1.25,000 0° 2° 3° 4 5 6 7 Water Resources | L bulLlLLlLLLLLLIJJ [51’47’OO” 366 47/30r 357 368 369 3:70 371 50’00” 372 373 374 375 52/30! 376 377 378 379 151c54'30” o r r 7~32!OO” 0/ ..'.'. LTD. 27 \‘k // \ \ I6 35 7 32 00 9 Fanamar .' 2% ‘\ "T \ \ coral coral o~\<§§la ~ \ ‘ro * \ 19/ ””‘x // \ \ \ / \ M 21 13 \b 0 I, Cy“ {I 13 \l Uncovers 1 foot *K \ 3 \ Sm 33a mus (/ 2 ,\ \ r \\ coral /I I r/ 24 \ l 1 \\\\ \ / \ s--./ \\ l \\ T” 23 ‘43- 17 x x 34 ,\ 22 \ l coral \\ lg 40 \\ \\ Cora} reef II \\ \ / is 24 24 x\ 7 éi \ 4 / \_~\\ 17 \\\ \\\ m // ‘ 25 /’ I\ 5 /I coral\\ // 39 37 8 \‘~ 4 2/ 00”” \\~-_-/’ sand coral 2 ‘ \‘>_ / 30 A ._ 8 27 coral 27 g; M sand 30 GEOLOGY TRUK ISLANDS WATER RESOURCES TRUK ISLANDS as 9 9 sand 28 EXPLANATION corn EXPLANATION 35 36 YMB DESCRIPTION SYMBOLS DESCRIPTION 8 UNIT DESCRIPTION _ mm 3 0L3 31 831 31 } Spring / Water tunnel 35 Undivided volcanic rocks, chiefly basaltic and andesitic lava flows. . . . Spring flow in gallons per minute ® Rain gage ,__, Indicates swept depth area In feet saga Andesite lava and autobreccia. 0 Well or waterhole © Stream gage 02%| 66 . 7O 71 @u/ Stream (number refers to table below) 7.5 76 79 Trachytelava and autobreccm. Basalt lava and autobreccia, most of which is olivine basalt (that is, contains more Stream discharges Moen FEbI‘uary 1955 coral than 5% olivine). ; , 8 3,2,” stream number million gallons per day gallons per minute 30 35 830 30 Nepheline basalt lava (nba) and melilite-nepheline basalt lava (mba). l 0'022 lI'I l 2 0.0% 30 Tuff, largely lapilli tuff, although thin beds of fine-grained tuft occur in a few places. 3 0'060 II'O coral sand gait shells Li seep _ M Volcanic conglomerate of variable proportions of pebbles, cobbles, and boulders of 5 i/ 0'290 207 coral volcanic rock, chiefly basalt and andesite. 5 g 0.150 32]— ’ l a seep - said I ' 23 Volcanic breccia, angular blocks of volcanic rock in a finer grained matrix of tuff 35 7 seep _ 34 (/— 30,00, 30 CL)” b 3 and angular .volcanic debris. Basalt and andesite blocks predominate except on 29 8 seep _ (l ' Udot, where trachyte blocks are abundant and basalt blocks are relatively uncommon. _ ’ I\ 27 @20 Through rounding of the blocks, volcanic breccia grades into volcanic conglomerate. all durlng dry Veather 29- C 829 L .._.V_.,-,,_ .. ._, .7.V..—- ,L d 1 recorded February 1955 15} 30 . . 34 ’,,/ \c\ 31 55 Gabbro~rich brecma, occurs only on Udot. 2 recorded 1 Februar ' l 5; stream a 8 installed 1 March 1955 ,x’ ‘x ”'3' L—* b 8 5 ,» 15 \\ m x/ @l ‘s\ coral Beach deposits, unconsolidated beach sand and loamy calcareous sand bordering the . 30 g,” / 12 \\\\ 29 beaches. 28 22 I shah z"” o \\‘s\ I I // 533d 23 C3 17 31 L x” 10 \x " Fresh-water marsh deposits, unconsolidated muck and peat. , x,” 3 Wm 21\\ ,,/’ + ‘\\ I 33 x ””0 12 13 13 “xx Mangrove-swamp deposits, salt-water deposits chiefly unconsolidated muck and peat; I 53"“ / L ) 30 lo 11 \ s \ 33 calcareous sand predominates locally, ‘ 1 >/ coral 23 ‘ 328 828 _. ”—7 7— a I M 28m v , ------ x -- 3, Earth fill, largely clay and crushed volcanic rock. I 'I 29 ,/ Cy?“ \\\\ sand \\\ ,,.c\ I I coml /// 28 \‘\\\\ \ .. no I I I ,/ I; 24 x - 0‘ \{T’ 8 I ,l I I 29 // coral \x 2 /A\y SYMBOLS I ; 18 “T“ I 31 sirlri 16 \ 27 so Strike and dip of bedding :‘ 24 : T R U K I S L A N D S / '\3 l sneiis I /,/ I", I '30 Apparent ster and dip of bedding 5 //’ ‘ ' coml 13 I I /// I 4: / Osokura C30 Strike and dip of dike I I x/ I 3k/ 827 827 e ~' >7 _ I 27 l , _______ a - x 17 I TT<>TT Stnke of verfical dike l I ///’ /,/f \\\\\ I 12 ‘2 l x , ‘\\\ 29‘: ~1— Strike of vertical joint ; I] 1 . l l I \‘~\\ Contact, dashed where approximately located I I 29 I ______ : coral I ‘TTe-s_“ Indefinne contact I 29 i I 29 _—‘7 ~~~~~~~ Doubtful or probable fault, dotted where concealed 8 326 A“‘— A’ Geologic cross section , , T‘ 18 26 H 15 c ral I 19 I I 30 3» /cl/«\ Lfl‘ I oTal / T \ i / \ fl // 66 \‘ 67 68 69 7O ,0 coral I I : l I I 28 6; I 30 I 29 I I ’5 / 18 25 , 29 It 1 / sand /’ \ 4 / // 23 \\c ral // . 12 / / 825 825 \ x 25 , /17 , and l 19 \ 16 19 / , ‘\ / I \ sand / l \\\ // 27:30” — ~va 3 II 13 1% 27i30r | , . , ‘ 3 via/f \/\0 Core I ‘ 3 I 28 18/ . fie,“ . / 2‘ J I I 27 21 ,’ Coral reel \ ' ’I 50 i w" r [I Coral reef f I T , ' l I 0 er POUIDGV) L I d . I 8 824°00'11“. 24 Z? /l ~——~—~ 24 7°27Ioor ’ A L [I I I L I I o \ ' 7'27Iocr - r r! ;. ~ . \ ‘0 " I I 151 47 00 366 000mg 47 30’ 367 3b8 369 370 374 4° 355 52/307376 377 378 €40 379 151 b4 30/ W856 5 Scale 1:25 000 H ‘ ' . U.S. ARMY MAP SERVI"E, FAR EAST - 574041 - R-15 - 11:58 - 3.4c Edition 2-AMS (AFFEI 1 % 0 [Statute We Geology by John T. Stark, Richard L. Hay, Harold G. May, and Elmer U . , r , r , - 1 . D. Patterson, 1954-1955. Water resources by Max H. Carson, 1955. Prepared under the direction of the Engineer. Hq AFFE 8A, by the U.S. Army Map Service, Far East. 1000 500 O 1000 2000 Meters Compiled in 1957 by photogrammetric (multiplex) methods. Coastal hydrograpby compiled from USHO I i——i T——-T t——i i—i i—t fl Ihart 6048, 1944. Hotizontal and vertical control established by Corps of Engineers, 1951. Names trans~ 10:30 H 500 0 1000 2000 Yards literated in accordance with rules of be US. Board on Geographic Names. Major roads are classified by g I I 1 1 ‘ ‘ reconnaissance by the 64th Engineer Battalion (Base Topographic}, 1952; other roads are classified from 1 0 lNautical Mile source maps and aerial photography and are not verified by reconnaissance. Coastal vegetation are clas- ‘ ’ ' ‘ ‘ ‘ ‘ ' COVERAGE DIAGRAM INDEX TO ADJOINING SHEETS sified by reconnaissance by Military Geology Branch, intelligence Division, Office of the Engineer, Hq AFFE/SA, with personnel of the U.S. Geologicai Survey, 1955. Map not field checked. CONTOUR INTERVAL IO METERS VERTICAL DATUM: MEAN SEA LEVEL 4544 II NW Geologic and water resources data based on on field investigations 1954-1955 by Military Geology MAP 5 Branch, Intelligence Division. Office of the Engineer, Hq, U. 8. Army Japan with personnel of the TRANSVERSE MERCATOR PROJECTION U. S. Geological Survey. HORIZONTAL DATUM is BASED ON THE ASTRONOMIC STATION No. 2 (195I) l5I'53’34.3' EAST OF GREENWICH, ' ’ , " 7 2‘ 37 7 NORTH 4544 III sw 4544 III SE 4544 ll sw LEGEND HYDROGRAPHlC DATUM : APPROXIMATE LEVEL OF LOWEST LOW WATER MAP 1 MAP 3 MAP 6 BLACK NUMBERED LINES INDICATE THE 1000 METER UNIVERSAL TRANSVERSE aiammw MERCATOR GRID ZONE 56 INTERNATIONAL SPHEROID r-Id tum" .WO 0, MD, We; we None Bum.up 3,“ THE LAST THREE oicirs or THE GRID NUMBERS ARE OMITTED \ \\ '\~».,, \ \ . 4543 IV NW 4543 N NE 4543 I NW .. . . ,. . _._ m §§§\\\\§s \\\\\\§Q\ MAP 2 MAP 4 MAP 7 loo-:9 I light Surface two or more lanes wide None Ciiurcn, School Cemelery f §§1§\\\Q§§§§\\\®g\\\t§§ hard surface. one ‘ane wrce None leII til danger m9 Submerged reel T , . I COMPHAUON METHODS I‘J‘J e or light suiiace, one lane wide None Wreck Sunken Lxccsed o I ~ _ ‘0? Photo-stereo Photo-planimatric » ' - » » O 05 GRID ZONE DESIGNAYION: To GIVE A STANDARD REFERENCE OH x - ~. . f m mnl Amh,t ml smw st k.f m JH M sAMu ‘ GLOSSARY ,3” OI GI “at: low ‘3‘: 3*: III: 94:” M Funk?" we 5 MIDI; :3 3 (TARILS / s 0 THIS SHEET To NEAREST 100 METERS KW Oror en anchorage .r - I 5.2 e esrwgrn.I.,R ‘ 3 7 . _ . _ _, a: Dr yin a i, as u d a l of mm or awas 29 I 100.000 M SQUAREI ENTIFICHION SAMPLE POINT. + SUNKEN ROC‘K A, USHO Chart 6048, I944 (reliability good). Unun en cape, pomt Carl Hark: tiavl ., —.—_fl “ Deoih Curves and Saundra,“ T- faint-ms _ mm mm; ,denmm‘ 100,000 mm,‘ Aerial photography: Feb., July 1946, , ., .__,___, ___,_ l a TI hchth 9 rules LP SIanda'd gauge Ia'I‘m' “we "a“ "959%": Dam. WC“ 1 2. Lotti:InsTvIERTIEAngrIaIIIneto LEFT of Standard gauge railroad, double iracli , , 7 —¢l—u—I¢— LP 3 point and read LARGE figures labelingtne 2’s“ Salt evaporators . , ., , L. L. I hit: eiihei In thetap or bottom margin, or Renew gauge railroad single lracli —r—"—T— APPROXIMATE MEAN DECLlNATION i955 ‘ on the line Itseil: 75 _ 2’6” FOR CENTER or SNEET l Estimaie tenths irom grid linelo paint: .1 "3"” 83‘139 ”“I’Dad- 5‘3““? 0’ "‘U'I'P‘e WC“ fl Rice Paddy; Marsh , ANNUAL MAGNETIC CHANGE iI EASTERLY ______-_ “WU—VJ 3, Local: first HORIZONTAL 3nd line BELOW p § . ’ paint and read LARGE figures labelinglhe .cwei .ransmissmn line ,, ,, , 7. .. 7 , Una diagram only Io obtain num' I values. line either in the left or “K,“ margin, or Soot elevation in meteis Checked. firth-called “/45 )(11.6 Nina, ”any“? ~ To determine magnetic north lino, conned the '23.:0:55:25Tfigfzv'e'gxf‘fldjgz 22‘:;:("'":e:::s"'imm and lineto WM. 283 Wall' LE‘r’PP‘ “liti “mg/21E PM” “’5’" ”P" °"' the M '49. °' ”h "'°P the full coordinates, Use ONLY the I , , o . 7 v 1 Woods, SCbe with the value of the ungln bah ”n GRID LARGER figures of the End number; SAMPLE REFERENCE: LP764233 Walerwheel OI mi'l, tCCEIt‘d Obie“ " awe! NORTH and MAGNETIC NORTH, as ploflod on “EMF”: 824 000 If reportinz beyond 18" in any direction, I Princrpal nangation light cl lighthouse, F‘zt‘iCI‘CHgP , * «E» Tropical grass. Coconut grove the degm my. a! the noun edge of the map. _‘ prefix Grid lane Destination, as: 56NLP764283 M OEN NW, CAROL' N E ISLAN DS 1958 15 7°27’00 323 820 25’00” 819 818 817 816 22/30” 8150mm.” 7°22’00” TRUK ISLANDS MOEN S \W Military Geology of Truk Islands MAP 6 Geology and CAROLINE ISLANDS 1.25,000 0° 2° 3° 4° 5° 6° 7° Water Resources I, LLLLllIlllILLI l l ./ “7,00” 366 47/30" 367 368 369 370 371 50/00” 372 52/30” 376 0° 379 151“54/30r / ,, .. 7“2 '00” ///// 22 28 y/é/r 7% /%’/ r w .//// //’////l;///// M/ , 17 ////////// , fl 8 23 23 25 ’ r . \5 Um," gn/ ’/ 1;, fir I Z / NTIIwisei t“ final; / 34 \V, ’ . 29 . , | "- 3 _, 19 , / 30 21 : ,7 ‘6 ,1 . ”/1 25 28 UOLA ROAD .\ ég 3 JV—“ggmc--- /,~»~\\11 ll (OROR EN I"!5 PUNc.) g -am- _- 15 21 , “fizz”, I/@\“ 47 i; ‘ I l> coral , ”,1” X 31 > ,o/ (”x 7 ._ ”I: . ~ \/ //, \l,/~ // \ 1 .' " /// / as 27 fl 34. 6 Elise-4:?“ ° ”"7“ 2 s;°\ 19 - 822 8 TRU ISL s ” 22 , DS WATER RESOUR K AND , _ , Q2: .1 16 GEOLOGY, TRUK ISLAN Wm . . 1w / EXPLANATION l C 7 SYMBOLS DESCRIPTION SYMBOLS DESCRIPTION 4} \q, shells UNIT DESCRIPTION Spring ¢ Water tunnel X Bose/of porphyritic basalt flow / 60"“ l , . . I . . . Spring flow in gallons per minute ® Rain gage \ 2 . , I r l UndIVIded volcanic rocks, chiefly basaltic and andesrtic lava flows. 77, I } R 23 // I‘ / 8 821 _ Well or waterhole © Stream gage I I“, ”,m \ cm, // 21 Andesite lava and autobreccia. @ I ngégg-é A; 33,3 // /"' I 1 3 f // .. Stream (number refers to table be ow) ‘K h M “M // Trachyte lava and autobreccia. \\ \ /,/ / 30 // 31 Stream discharges, Moen, February 1955 / ,/ sand Basalt lava and autobreccia, most of which is olivine basalt (that is, contains more . , / than 5% olivine). stream number million gallons per clay gallons per mlnute 1 0.006 11 Nepheline basalt lava (nba) and melilite-nepheline basalt lava (mba). 2 O'OOI'I' 3 C2’7' I /// 3 0 . 00 3 2 m, o a T ff | | I 'II' t ff althou h thin beds of fine rained tuff occur in a few places 1+ 0.003 2 1’ 13 820 u , argey apii u , g g . 5 0.001l 3 [I] 1 ‘1“; 25,00” 6 trickle — 13 IE Coral Volcanic conglomerate of variable proportions of pebbles, cobbles, and boulders of 7 trickle __ 0 and \\ 3 volcanic rock, chiefly basalt and andesite. 8 0.003 2 J M éiu \K 9 0.004 3 - \l r \\\\‘ Volcanic breccia, angular blocks of volcanic rock in a finer grained matrix of tuff all during dry weather / “Eli and angular volcanic debris. Basalt and andesite blocks predominate except on \/ Udot, where trachyte blocks are abundant and basalt blocks are relatively uncommon. stream discharges, Fefan, February 1955 I; 5. Through rounding of the blocks, volcanic breccia grades into volcanic conglomerate. l O 003 2 ,/l\ 2 0-017 12 A. 353.. 23 Gabbro-rich breccia, occurs only on Udot. both during dry weather \ un’len/NSaiJwb' , Stream discharges, Dublon Island, February 1955 / 319 Beach deposits, unconsolidated beach sand and loamy calcareous sand bordering the 33 beaches. 1 O ' 006 II, coral 2 0.002 1 A“. m. 4‘“ Twit“ Fresh-water marsh deposits, unconsolidated muck and peat. 3 0.007 \5 A“ ‘“ 1i 0.15 104 \ / . , l 0.15 lOI-l» “ ” \ /\ i\ 29 Mangrove-swamp deposits, saltwater deposits chiefly unconsolidated muck and peat, E J 0 014 10 \ 9/ /7l,/:/\ \\ 9 \3//\ 52 32 calcareous sand predominates locally. 0 - {fol/””4 \ \\ L“! 7 0.04 30 , - \\ \ 12 8 0 .002 l ’ \\ \\ 23 25 f , Earth fill, largely clay and crushed volcanic rock. 9 0.009 6 r \\ \\ 10 0 ° OOI,‘ 3 \\\\ 20 1 8 34 22 818 ‘ ll 0 . OOb Ll- \\ \\ g1 28 sand \ SYMBOLS all during dry weather 15 \\ 22 25 ‘ \ 28 _r, s k d d. fb dd. l/ stream gage installed 12 March 1955 16 18 \\\ 31 20 30 tri e an Ip o e Ing \\ \\ sand 21 is T R U K I S L A N D S ,,,,,,,,,,,,,,,,,,,, ”66 Apparent Stilke and dip of bedding 19 \\\\ A __________________________________________________________________________________ \\ TRUST TEFRITORY OF THE PACIFIC IS ANDS 02.7.. x 23 n 49 23 22 22 —V—‘ Lfil 30 Strike and dip 0f dike (U.S A. ADMINISTRATING AUTHORITY)l I 17 l —6— Strike of vertical dike I —— + Strike of vertical joint _, ‘ 1 7 I 18 l \\ Contact, dashed where approximately located A I \ 17 at 18 21 /’ l I ‘, I “““““““““““ Indefinite contact I 8 K it I - , \\\ ,L/ AZ. . —“?--_. Doubtful or probable fault, dotted where concealed 7O 97) 17 72 7‘3 . ‘0 I A A' Geologic cross section 13 15 I L_,iindlcates swept depth area in feet I 17 Icoral I 12/ 2230” Cara \\ ”é \ l \ \— 7' 15 \ of , 17 l 0 N01 l i——‘ 8 1, 1 20 (,7 \ corm 5 .. \ I M gfigffli “ML" 1 kg) m 815 0 .~ '~. \, x, ,. ._ 5 53 "If ll 19 colt”$2 2?: $590M % ‘olil ‘\ ......... . ° \,,,_ ,, . .. , ...... W 13 sand\\\ 13L / . . r ,Iiba, Ionian 16/503. , \\ sand Cora a l ' i ;’0l an s ;' ’ cora .2.) \ Unun on Neawachang I \\»c—0:al ‘ crirlai 00 V0 ,, , 1. WCoral, ETEN ANCHORAGE / of II, 1; . . I -, I 16 2 £21 £3: . Corgi/"x 038, // L51 4“ % Coral 7-.) '0 S k...“ chral \ ‘./9 531d 17 _°\\ 53) [,1 4 7 a . > A\\ ' . .44 a " —"" ‘ on.“ . fix I , x/ / 7°22100rl b 151°47’00” 366000m4E. 47/30” 0/ 367 368 369 \G' 371 50’00” 373 374 p 5230/1 376 377 379 151'54’30” 375 W856 8 Edition 2-AMS (AFFE) Prepared under the direction of the Engineer, Hq AFFE/8A, by the US. Army Map Service, Far East. Compiled in 1957 by photogrammetric (multiplex) methods. Charts 6048, 6050. 1944. Horizontal and vertical control established by Corps of Engineers, 1951. transliterated in accordance with rules of the U.S. Board on Geographic Names. Coastal hydrography compiled from USHO Names Major roads are classi— fied by reconnaissance by the 64th Engineer Battalion (Base Topographic), 1952 and reclassified from aerial photography dated 1955; other roads are classified from source maps and aerial photography and are not verified by reconnaissance. Coastal vegetation are classified by reconnaissance by Military Geology Hq AFFE/8A, with personnel of the U.S. Geological Branch, Intelligence Division, Survey, 1955. Map not field checked. Office of the Engineer, Geologic and water resources data based on on field investigations 1954-1955 by Military Geology Branch, Intelligence Division, Office of the Engineer, Hq, U. S. Army Japan with personnel of the U. S. Geological Survey. LEGEND ROADS All weather hard surface, two or more lanes wide _____ 5 ”~55 Burlteup area ,,,l___._~,..._ 3 LANES loose or light surface, two or more lanes wide __ hard surface, one lane wide —_i_ loose or light surface, one lane wide i Fair or dry weather, loose surface, two or more lanes wide 7 fair or dry weather. loose surface, one lane wide , ::===::: Carl track; trail _ Standard gauge railroad, single tracli ., —-i—t—t— Standard gauge railroad, double track v, 2,.” Narrow gauge railroad, single track L a,“ Narrow gauge railroad, double or multiple track w, —n—“—n— Power transmission line ____,,,,L -__.____./ Spot elevation in meters: Checked; Unchecked _ cl, " us “/56 Wall; levee; Cliff ___,_ _W§L\§ Waierwheel of mill; Located object “Nil ’3 OTower Principal navigation light of lighthouse; Anchorage __ * LL Church; School; Cemetery Limit of danger line; Submerged reel ____i,l Wreck: Sunken; Exposed i Sunken roclrs; Foreshore llats Rocks bare or awash; Reef _ Depth Curves and Soundings In Fathom: ,, Reservoir; Dam; Ditch ____ _____ Salt evaporators Rice Paddy; Marsh Nipa, “ Woods; Scrub Tropical grass; Coconut grove ' i - l if D D lll CID Scale 1:25,000 2000 Meters l 1 2 0 1000 500 o' 1000 I I—«I I—I I—t I—I I—I 1000 500 0 1000 2000 Yards I I-——-I I——I I-—I I—I I—-I *. 1 0 GN ' I 0.09! 4 45 OR OR 84 MILS 3 MILS APPROXIMATE MEAN DECLINATION 1955 FOR CENTER OF SHEET ANNUAL MAGNETIC CHANGE I, EASTERLV Use diagram only fo obtain numerical values. To determine magnefic north line, conned fhe pivof point “P" on fhe south edge of the map wifh the value of fhe angle between GRID NORTH and MAGNETIC NORTH, as plotted on the degree scale of fhe norfh edge of the map. CONTOUR INTERVAL IO METERS VERTICAL DATUM: MEAN SEA LEVEL TRANSVERSE M ERCATOR PROJECTION HORIZONTAL DATUM IS BASED ON THE ASTRONOMIC STATION N0. 2 (l95l): l51'53’34.3’ EAST OF GREENWICH. 7'21’37.7’ NORTH HYDROGRAPHIC DATUM: APPROXIMATE LEVEL OF LOWEST LOW WATER BLACK NUMBERED LINES INDICATE THE 1.000 METER UNIVERSAL TRANSVERSE MERCATOR GRID, ZONE 56, INTERNATIONAL SPHEROID THE LAST THREE DIGITS or THE GRID NUMBERS ARE OMITTED GRID ZONE DESIGNATION: TO GIVE A STANDARD REFERENCE ON THIS SHEET TO NEAREST 100 METERS 100.0(1) M. SQUARE lDENTIFICATION LP SAMPLE POINT: I SCHOOL IGNORE the SMALLER figures of any grid number; these are for finding the lull coordinates. Use ONLY the LARGER figures of the and number; example: 315000 1. Read letters identifying 100,000 meter square in which the point has: LP 2. Locate first VERTICAL and line to LEFT of paint and read LARGE figures labeling the line either in the top or bottom margin. or on the line Itself: Estimate tenths from grid line to point: 1 . Locate first HORIZONTAL grid line BELOW point and read LARGE figures labeling the line either In the left or right margin, or u on the line Itself: 78 16 [shouts tenths from grid line to point: 8 SAMPLE REFERENCE: LP781168 lf reporting beyond 18“ in any direction, prefix Grid Zono Damnation, as: 56MLP781168 1958 1 Statute Mile 1 Nautical Mile Geology by John T. Stark, Richard L. Hay, Harold G. May, and Elmer D. Patterson, 1954-1955. Water resources by Max H. Carson, 1955. COVERAGE DIAGRAM {f5 1% /// ’7’ ”xx A92. I 1%fo // x? //, 2/ I." 'I ”3"; éi’ A , r ///'f . m . My \ «*3 x ‘ \Wng‘; A. USHO Chart 6048, 1944 (reliability good). B. USHO Chart 6050, 1944 (reliability good). Aerial photography: Feb., July 1946. U.S. ARMY MAP SERVICE, FAR EAST - 57-041 - R-15 - 11/58 - 3.40 INDEX TO ADJOINING SHEETS 4544 ll NW MAP 5 4544 lll SW 4544 III SE 4544 II SW MAP 1 MAP 3 MAP 6 4543 IV NW 4543 IV NE 4543 l NW MAP 2 MAP 4 MAP 7 GLOSSARY Mom on bay Oror an anchorage Unun en cape, point MOEN SW, CAROLINE ISLANDS Military Geology of Truk Islands MAP 7 Geology and Water Resources 3;: -‘ in; l 4 0/ 33 g ‘ l / , Cora \ l 4W \ lj j . fl 10 , 17 Lio/ 123/ 23 1 " f ' \ ’/ 17‘ A" OROR EN UNU o J - l . r“ i 3/ , . ’- m- ‘ ,__E_1_‘EN ANCHORAGE ,4 k3“ , - . - - ’ 22 “““ 0‘ ——~«4. A2 / l 19 *U covers, foot ‘ I 117. ”99!... l t l I ' ‘ 2 Q \ / u‘ N FANIPfii rrarea' , ., .‘l ‘i 1 I 29 . J coral 4 \ 3 \ Coral reef ‘ coral l \ ‘ x @3 l 5 8 ral ncollers Pivot“ j, :‘ nun .L ou \ t \‘V/ Z l 18 sand .1 s \ “““ , /, ,/ \ //:\ , / x WATER RESOURCES, TRUK ISLANDS SYMBOLS DESCRIPTION SYMBOLS DESCRIPTION >'.‘-"l 16 f Spring / Water tunnel ‘ ”3". . I7 is 7€§£bnun en ochamu spring flow in gallons 'per minute ® Rain gage . m0 , . Un‘ vers 2 feet orig}s EN NENGEON , e 0 Well or waterhole © Stream gage \ ‘ 10d \ 18 \ 16 ~ 1 an . /2%§§fl/ 10 12 r @/ Stream (number refers to table below) / l ‘ . l GEOLOGY, TRUK ISLANDS , Stream discharges, [Imam March 1955 ‘ stream number million gallons per day gallons per minute , 6 EXPLANATION 22 1 0.006 m 7 com 2 trickle _ _‘ , 3 0.009 6 coral l ll. 0 006 1+ _ (Til/LIEU B . u \\ 0 UNIT DESCRIPTION l 5 trickle - - l 6 0.002 1 24 7""TT‘ VOl Undivided volcanic rocks, chiefly basaltic and andesitic lava flows. r all during dry weather ‘ Stream discharges, Fefan, February 1955 Andesite lava and autobreccia. 13 15 l 0 l 0.004 3 l L _ Unun en Fanmono l 6 2 0,011+ lO Trachyte lava and autobreccra. i 18 , I. ,l 1 coral ‘ ll 5 0-007 5 pm . _ c...v.2_.-.~...__e-.._..MM-..’5 0.-.... -l-.- we, E ‘ ~ w - _ mm.-.“ . r ‘2," r i, 0.003 2 u, Basalt lava and autobreccia, most of which is olivine basalt (that is, contains more 23 10 ‘ OROR EN KUKUWU l / I 5 0.003 2 h o/ r ' . d I l ’ r . 1: an 5/0 0 lVlne) sen aria snels o E 12 17 E 17 ‘1 / (1/ 0 0.003 2 21 Unun on Unuf l [I ,l 7 0.007 5 Nepheline basalt lava (nba) and melilitesnepheline basalt lava (mba). ' 15 i // /( 8 0.006 1I» 5 i5 r” ‘/ 9 0.0014 3 5 and and sheflsr / Tuff, largely lapilli tuff, although thin beds of fine-grained tuff occur in a few places. ‘—‘ / ____ \\ [I l 10 * 0.022 15 ,/’ f‘fx-‘ _ ll * 0.017 12 13 11’ / 12 0.014 Volcanic conglomerate of variable proportions of pebbles, cobbles, and boulders of /’ ‘\ ’/ / L 1.0 volcanic rock, chiefly basalt and andesite. 12 / ‘ i’ «I 17 13 0'029 20 U [/l A l r] ,M lll 0-006 4 nun en ran a he i . . . . 12 / . 9 .‘2 . , 52 15 0.003 2 Dr Volcanic breccia, angular blocks of volcanic rock in a finer grained matrix of tuff . and angular volcanic debris. Basalt and andesite blocks predominate except on » - ' " recorded after heavy” rain; all others during dry weather Udot, where trachyte blocks are abundant and basalt blocks are relatively uncommon. 2 ”E ‘ Through rounding of the blocks, volcanic breccia grades into volcanic conglomerate. / 12 i '_ l Unun en Chukusirip l< " 28 l I l l / l 30 Gabbro-rich breccia, occurs only on Udot. /,’ 12 l \ i /’ , A l j / 12 // 1" l l / r - Beach deposits, unconsolidated beach sand and loamy calcareous sand bordering the x l 24 i / l. Xi beaches. \\ l ’l 0 l l 36 1 " / m J A \3, 3:022” Onfrena l oftohyew A 28 i i, . *mW—m Fresh-water marsh deposits, unconsolidated muck and peat. \ '\ :23 ‘i‘ ‘ E ‘l dual VIE , , , E . d; E . 1 r \ , W was n‘fi‘ ~34? Mangrove-swamp deposits, salt-water deposits chiefly unconsolidated muck and peat; 15 r \\\ l ‘ ' calcareous sand predominates locally. ' 377 53/30” 378 379 151°54’30“ \\ l 31 H H m n M 24 7°17’00“ A“ 701700 0 \\\ l 3; , if“ ‘ ‘ ‘ Earth fill, largely clay and crushed volcanic rock. i \0 W, 73*" Island 83g l I 11 \\ , [i 51 / a wad O Atkin Island \\ 18 . / 2 \ 0 ”TA Nukanap\ I [I / \ l 305 HT —* 805 \coral i 96 z . 1 \\ 23 , 1 / Q} 62 \\ SYMBOLS 2,3 K 32 13 U M en 9 0R EN NUKANAP ‘ ,/ Ne imokul| 7% all - 33 / l\ l , l _an' Strike and dip of bedding 29 : // 24 "°’ ' - l? ‘f‘ 27 l , l r 24 8 Qség . g. , ,. 8.5}; i; , , _ _ ll .[1 ,. . \ . l30 Apparent strike and dip of bedding 1 ,’ l [I fiT\ l U 28 ’ Z 23’ —v—30 Strike and dip of dike ,i’ 17 00ml 12 l’ i" / 3 l l/ l r ‘ + Strike of vertical dike 1/ 0 12\‘\ ,r l W \\ i’ 804 804 SAPOTI U 7 3 \ ——I— Strike of vertical joint 1: TSIS p 7 e l, 30.’ coral J) ' \II 1.8 ' l Sopohu / \\ Contact, dashed where approxrmately located I ’ , . . l77fi’i” _ \\ r/ J // 1:!50’ ' ‘ l coral / E r 19 Indefinite contact / \o/ 3; I 17 . , i all?) 9 f" 9m V - ~ > r ‘ r " / -QSOJC i‘t. , ,‘i/fl 4i) // Eula“: l 3 . Doubtful or probable fault, dotted where concealed l war 5 / r r _ 3% a@ \\ \ \ \\ _\//L/”/ 1600/ Feneu Island 16/00" I \a E \)2\ I _ _ 35 ‘“”’ /, 11 19// l \ ‘ CW“ \ A A Gemoglc cross section shells 37 9‘ 11 a \ gravel and shells l 1 shells 0 EN SAPO 2 i l / i l H 3030mm. N, 803 '1 /4 I,” 3, i, 33 5; 4 ,I 22 i . i / / l I E ,_ rig ‘ 7“ 1 mo” 368 369 370 371 50’00" 377000m- E. 5330” 378 379 3215105460,, 7'79 15i“54’3{)” Scale 3:;{irt‘iiif‘s _ Geology by John T. Stark, Richard L. Hay, Harold G. May, and Elmer ll ’1 M? Lti'w sl ’ ‘w‘ii . .s .1’1‘8 3 as; D. Patterson, 1954-1955. Water resources by Max H. Carson, 1955. H0 Ar‘l‘t: R/L by the US. Army Map Service, Far East. ’ astal hydrogiaphy compiled from USHO Jl estao load by Corps of Engineers, 1951. Names r! on Geoniaphir. Names. Major roads are classi» _ . (156‘ Topographic, 1952 and reclassified from ‘ V‘Nl"”‘”‘ M”? . .7 . . . A _ _ A . Gar, if ,V .. a from source maps and aerial photography and T {‘(su‘l‘sv’z’h‘l‘l'r E';g"‘<‘l“flr"l lNDEX TU ADJOlNlNC‘ SHKETS "of ed by l'ivtLLllll‘laIbSallCB by Military Geology Y _ «.— A . v r... W _ . . . . ,. . __ ... _ . . .. with liozrsonriel or the U6. (Seolitrglcal CON 1 OUR lNTERVAL lo M ETELHID Will H 'DUQ‘. .5: ‘l‘l "AU” lULl RS A l :3 Mi; [LR ”‘4 i EHVALB ““5 ‘s'l‘fky" VERTICAL DATLJH new 4544 ” NW _ , l e .. ,. . -, , MAP 5 TRANSVERSE MERLA TOR PRl.)Jt.CTlOl-i Geologic and water resources data based on on field investigations 1954-1955 by Military Geology HORIZONTAL DATUM is BASED ON THE ASI‘R ' NOHlC si/xriosr no 2 (1951} Branch, Intelligence Division, Office of the Engineer, Hq, U. S. Army Japan with personnel of the i5i"53’34 3” EAST OF GREEmw! i, spar/fly? NORTH 4544 III SW 4544 III SE 4544 ll SW U. S. Geological Survey. LEFEND \J' HYDROGRAPHIC DATUM APPROXIMATE LEVEL :ir LOWEST 11.1w WATER MAP 1 MAP 3 MAP 6 hi: i-. Mt, BLACK NUMBERED LINES INDICATE THE r000 Mere; UNIVERimL TRfiNSVERSE m "l . MERCATOR GRID, zone 56, INTERNAHEsNAI. srmareoio 4543 IV NW 4543 IV NE 4543 i NW liar-3, mime {on 1;. min late: mile : hurlliip area ,, , ,, ,., rHE LASY l‘HREE DIGITS CF lliF ulr'i‘; NilMEsF‘rZS ar'i- rmil’l'lii‘i ON 7 one :‘i "gm Sl-Tlaffi, tar or more lines We : . {‘33,}, ClllllCll, School, Cemetery V * MAP 2 MAP 4 MAIP—I / hadaflk .n.lw cw Linmi; lm‘? mierrfl r at a wr l' ~1iri2r>r r, we ngl e E (I .0 I COMFlLATION METHOD. ., on» his wine Wreck Sunken Exposed 0.“, I 7/ a 45 _ Photo-Stereo Pmm’l’lallllllelm: Map FLOQ‘SARY ,, , , , ‘,.,, Q, r, ._ ‘ , / 0“ (still) [out UESiGNAriON: ii I} ‘ ‘ " '" ’ ' ' " 'i _ , m V ’ ii la L m, Ll n. . “town mike .mshore liar; CR l 4. I M "In fSN ii ~\ . Curr ell, anchorage ., E . / ~ .) ‘ l ,, E "' ' "" W“ . ‘ Gl‘i’ ”lit-Pl WW z'i'lslfl’r "l‘7 W" lint.“ bare iii mat-ii ”mil J ML 1 l ,i/ ,/ IOUflTd’hTVS-{l'l‘lhrflffil{Ifhi‘rrl A ll‘i‘ll’) {-er M. an: - w .r . "fun on ‘ ... l. - .. , ~~ was £3043, “mm “‘3 . heath Curve: rlllil Silllnfllllgi- lr'l faliiorrs l i / E 21 DC m a . . , B USHU Ulléill (wilfill. 151?: It‘ll / .7.» _‘7 if, 7,-“ f i“ ‘ l . i“ s i r r - . V . . . , . . . Standard girsss railroad, willie trarli “awn—«~— Reservoir, llam, DIM i/f/ l LF’l l l Aenal photography Feb” 1”” “”6 ilariilail Huge railroad nimble *rart "'W’"W‘** y/ l l 2%” mnemmem l LP i . , l han‘w mugrianmad_smgw ham su~r~--v- «PVRUKlMRTE HFKN nrrtiunrrrN l955 l l , l?! l . E , 23" ron EENYFR 0i snitl i l i ‘ 3‘ i “3”“ ENE ‘a"'l‘a\”~ MW“ at mm?” ”'1‘“ ”w” “ Rite Paddy. Marsh ANNUAL monrrit LHANGF i’ Easrrrzir L , l, L L , ,l l i 9‘3“: “WW 51'3“” he Una ding/om only to obtain numerical volum. Wl._.-_.._.____.__.._ h 7/ ml gm... 5,9,9, r, we left (i, “W ”W; .1 .3, i 5 Spal elelalic-ii 2n meters Checked. Unchecked " m5 xlbs NM" Mangrove , '7 To determine magnetic north line. conned the ”so“ "E1“ Swllw "it"“fld’l‘y l MW Me ”A?” , ,, ,_ in mm in: as: are or in in; i s 2. i lnlll rr izdln ii iris Wall. levee. Clii‘i _.l-_m% ‘ PM" PM" P °" "’° W” “’9“ ”Hf” "”9 rm» iirii r-c-oramaies Use arm the l S m” E 5 am i I e ”)0 W E 121 'ower Woods; 8WD "' ’ ' ’ vi”! the value a! the angle between GRID ”(your figures of in» grin number; ET ' aterwneel 0 mill, Located obiecl o‘ , . exampla. o ~,r '\ Wm " ji‘ NORTH and MAGNETIC NORTH, as prom on I uOfitJu l . r mm event! 18 rm, wire", 1 i - l s2 Dss:v::::1_ss-., ...,le§i3i£z_iaiaa UMAN NW, CAROLI N F lSLAN DS v Printipal navigation light of lighthouse Anchorage ,. , * Cu Tropical grass, Coconut grove the degree scale at the north edge of the map. 1958 Military Geology of Truk Islands Geology, Engineering MAP 8 Materials, and Water TRUK ISLANDS ‘ Resources CAROLINE ISLANDS i5i°sooo’ i5i°52’oo" 52’30” 56130” 5700” 15I°se’oo” I I I I I I 6°” I ,, , MAP 8 <2 36’30— —36’3o” a GEOLOGY ENGINEERING MATERIALS AND , . .. , . "o“ v 9 7°4osd m 7°4oso Co 0. WATER RESOURCES MAP OF ° ‘0 CORAL ISLANDS TRUK ISLANDS *3. o , , 3I’30” ~3i'3o" , D 7 3930—- 7°59’3<5‘-. @ I958 ‘0 03°36’00” 7°36’oo” I |5l°50’OU’ 1 Scale 125,000 1 5 0 1 Mile 0 I l/ / u I H J . . I J .1 . l5| 4530 4600 4630 I II E 1' r I r I. r . . . - |5l°52IOd 5230 1000 H 500—{ H H? 1000 2000 Mae's I I I 7°3l'00” —7°3I'OO” 1000 500 0 1000 2000 Yards r i—i }-—-I I——{ i———I I——t r—————-—-————i 56'30” 5700” 4 i’od’— — 4 "00" I I Isi°5e’od’ 58’30’ GEOLOGY ENGINEERING MATERIALS I52°oo’oo” 00’30” // I . '4'30 F i4’30” Coral limestone, consolidated de- CORAL LIMESTONE Exposures of relatively 7040/36, 7040/30” trital calcareous beds, includes soft, weak, porous, white to light buff, beach rock and cemented coral massive coral limestone 0 to 3 feet in consolidated reef rubble elevation. Exposed in narrow irregular deposits probably Q ‘I’ 1 benches in intertidal zone along beaches grown in place ‘5' 3° 0°, I52°00’00” of lagoonal and barrier-reef islands. Suitable for road metal, base and sub- '.. s;;~;;_--..'..”U_shi base courses and for rock fill if filler is I l I pig II"-~..I_;:_';. 7°I4’Oo"— 7°i4’oo” added. Unit 6 i5i°45’3o” 46’00” 46’30” Lamoil-;'_:_.--" Ruoc'II'I'“ Tore." ... Unconsolidated calcareous sand; CALCAREOUS BEACH SANDS Loose, POOF- T RUK ISLANDS ‘33.. "'I"_-~.,I\I|‘;I'ILI;§057 - ranges from fine to coarse ly graded, fine to coarse, angular to [Slam/00,, 4,130,, ' , S l subrounded grains of coral-reef detritus. I r I o 5 IO Miles I5I°59'oo" ISZOOOIOOSI/s’so” Exposed up to 2 feet above high-tide I—‘g‘g—J—bw—I ._.,:.;'.1' l l level along sand beaches and adjacent 39’30"-- O; sandy flats. Only subaerial source of —7°30’ More} sand in Truk Islands. Unit 7 'I" ‘ 7°30’— I H MOEN '2 3° . ,, . [23 Mangrove-swamp deposrts M MANGROVE-SWAMP DEPOSITS Loose, O coarse to fine, calcareous sand with small . scattered areas of mucky earth on sandy I . ...... ._-'.'I-I-II"II ,5 subsoil; submerged at high tide 0.5 to 2 . DUBLONI'QI"; feet. Occurs as irregular fringe along 7°39I0C5I— TOL [g0]- CZISLAND coasts. Unit 15 + + * Onorriue + ’~ % FEFAN I 2.00., Fresh-water marsh deposits siL MARSHLAND DEPOSlTS Muck and peat of lz’od’ JL ‘31 various depths on sandy or plastic clay + + ©UMAN subsoils; 6 to 16 feet deep. Water table 5 I J Ed.a’r at or near ground surface. Occurs mainly |5|°4|I0dI 4|I3C5I on coastal plains. Unit 16 b ------ . Coarse calcareous debris, includes 33:: CORAL BOULDERS, COBBLES, AND GRAVEL OIIIlIon °aa H gravel, cobbles, boulders, and 09:00“: Boulders and cobble zones on seaward I5I°3I’oo” 3,130" ”’30 . U angular blocks side and beaches of coral barrier-reef l l “30 islands; gravel zones in interior and “d ..... beaches of islands: Boulder fields up to [5,030,001, Mé‘s'ééon o , U 6 feet above high-tide level. Water table 1 I52, 0000 at or near sea level. Crushed boulders and cobbles suitable for base course and road metal; processed gravel suitable for , , base course and concrete a re ate 7°I7’Sd’— —7°I7I30” 7°IIOd . n _ 99 g ‘ AREAS IN SQUARE MILES —7°H00 Unit 18 Ruac . . . . . . . . . . 0.021 Udidan . , , 0 036 15.059’odl 59/30” l52°OdoOII TOI‘a o a a o o a n o o a O - O21, UijeC . ' . . . . ' I - O . 106 l5|°56’o0I 56’30” 57/00” 57/30” Dip and strike of consolidated bed 3/ 5 013'. u I 6’ Northeast Islands Mesegon . . . . . . OI256 I I I UIIgaIr ' ' °° 3'3 North Island. . . . . 0.028 011% . . . . . . . I I I OI089 ”as Engineering sample site 03 South Island . . . . . 0.052 Edat . . . . . . . . . OIOO5 IO’30”—— 61,030” Salat . . . . . . . . . 0.100 Onamue . . . . . . . . . . 0.017 Mor-----o----O-029 1amoi1..........0.007 WATER RESOURCES °3’3o” Poms ' ' ' ' ' ' ' ‘ ' 0'062 Pig ' - - - . - - - - - 0 126 l5l I 1 . ' ‘ " I Banan . . . . . . . . . 0.148 UShl . . . . . . . . . . . 0.016 0 Well or waterhole; numbers indicate water sample site, see table 15. le’oo” ® Rain gage —I0’OOI’ i5i°s4’oo” 54’30” 55’00” 55’30” l I l l LEGEND 7°]7’3d —7°l7’30” . os’30”- , , I 1 7°09 30’ Submerged reef n+fl+_ Spot elevation x2 |5|°3|’3o” in meters Sunken rocks + + I N I H l l l '5 I?“ 0° 33130 391100" i5i°56’so” 5700” 5 7’50” Rocks bare or awash x Trail ............... Reef €38 Track ——————— III _. + ~7°09’o o” 7°i3’3o’ — Geology by John T. Stark, Richard L. Hay, Harold G. May, and Elmer D. Patterson, 1955. Engineering aspects by Harold G. May and James L . . ' _ E5 it E. Paseur, 1955. Water resources by Max H. Carson, 1955. l l 1 MMesegOn I 1 l l Base from AMS map “”95 W856 I5I°38’00”’ 38’30” 39’00” i5i°54’oo” 54’30” 5500” 55/30” se’oo” us. ARMY MAP SERVICE, FAR EAST - 57 041 — R-15 - 11/58 - 3.40 Military Geology of Truk |slonds,Coro|ine Islands MAPS 9 THROUGH 15 SOILS Military Geology of Truk Islands U 10 O T“ S W - CAROLINE ISLANDS 125,000 " 0° 2° {1° 4° 5° 6° 7° MAP 9 Soils L LELELELiLJEELEIuJEIuJ 151°32/oor 339 3230!! 340 341 342 343 35/00! 344 345 346 347 348 37/30" 349 350 351 151'39I30r 7o27r00’l I I ‘ \ 0\ [/4 \ ”V/ 27\ 3 /l 30 (K 7-2-1700” ‘ 29 30 <fl cggi‘ X25 ,CID‘ A3 77». l 2 I 29 {I 1 \\/ lot \\ 1‘ /i’ ,I 30 PA C I F I C O C EAN [/7?‘ 32 :rf/ 25 //;1\ \ cg?“ . ,1 7 i ii ‘, 26 823 23 l. W ‘ .331 l a ” 823 \E itsajEe // £3.51 32 cgrlal \\\\l’//// ” 12 L5; 27 \ 155 sand 27 8;; /& 31 27 , ”V” 55 K v\ / ’/ 2 i ‘_J ’i FALE 32 / [I / ’ mofll/ Floodkknog/ [52/ 22 // 24 822 822 54 24 285 15 E 41 42 43 44 45 , 4 48,7/ 49 50 27 51 ‘ coral l E7 ’ coral 41 | l i 29 52 E74 27 SOILS MAP TRUK ISLANDS 21 "”43 Q 25 31 ,7/' 28 , /,E7 ’/ coral /7 ,74 26 /_\ .26” T R U K I S L A N D 33x, ,8 21 821 821 W. EXPLANATION , . . ‘ / _ 7 \\‘> / 24 47/77" 755;“ DESCRIPTION 32 fl 7 ’ 23 fig; 1; TRUK CLAY, less than 25“.; slopes Latosol on gently undulating to hilly slopes; reddish-brown and red clay; surface few 23 / 2; 7,77", E7/”"/ com _ CW' : j feet usually granular, grading downward to massive structure; porous and well drained; friable, firm, slightly plastic and coral 28 (xx/x 32 14.74”!“ . 3‘ 16 sticky; slightly acid to strongly acid in reaction; depth to volcanic bedrock 10 to 50 feet, surface 10 feet generally free /E.7—"/ ,e7/// 25 a ’ of unweathered boulders. 47/7/74” 7/ ,7E\ 28 ///E7/ LLEE'yJ '7E7e’JTA/ 1/, 31 /i //’/,E7"’249 J} 14 21 TRUK CLAY, 25 to 65% slopes Latosol on hilly to steep slopes, similar to 1D except the gradient is higher and the {Ex/’4 33 LCcofal / I I coral soil contains some boulders and rock outcrops. V coral \\ )\ fl: 7/” /7 x 25 ‘~7_/’ 27 E7/”‘ 23 ET / 3" i ”'3’ 30 E7/ / TRUK STONY CLAY, less than 25% slopes Stony Latosol with local areas of Lithosol on gently undulating to hilly (<2; 1 /,E7/” slopes, 1 to 10 feet thick over volcanic bedrock; 70% is reddishbrown to yellowish-red clays; granular; porous and i _ ,’ 7/7"” 25 25, , . . . i E 25 22 25/004 00 7 20 well drained; friable, firm, and slightly plastic; slightly to medium acid in is very dark-grey to dark- 29 \E,,/ 7/74 4 —— 20 °°"" * 8 820 20— brown clay; strongly granular; very firm, plastic; slightly acid to medium acid in reaction; somewhat poorly drained; 'i 20 h 25 /,E7/‘ 25 20 average depth to bedrock sbout 4 feet; estimated boulder content about 15%. \ /“‘~\ \ 7 7/77’”/ mm ;’ 3 ‘i, 18 k x23 24 TRUK STONY CLAY, 25 to 65% slopes Stony Latosol with local areas of Lithosol On hilly to steep slopes, 1 to 30 feet ‘\ ,r’ 30 25 IE — (x sand and Sheri; 2E thick over volcanic bedrock; reddish-brown to red and reddish-yellow clay; granular; porous and well drained; friable, firm, \y” 1 ,~ /31 slightly plastic to plastic; slightly medium acid in reaction; volcanic boulders common on the surface and compose about 21 E f,/” O 205‘,“J of the profile. IE7” 21 1‘ //’ o 22 ” 21 2F TRUK STONY CLAY, over 65% slopes Stony Latosol and Lithosol on steep to very steep or precipitous slopes, similar TRUST TERRITORY, ”OH THE PACIFIC ISLANDS G) 23 to 2E but contains more boulders in soil profile. (U.S.A.’ADMINISTRATING AUTHORITY) 12 I} xxx/"I; FEFAN SOILS Soil found mostly on gently undulating slopes, 1 to 8 feet thick usually over either olivine basalt or A 7/‘// 18 77 /E7~’/ nepheline basalt; the surface 1 to 3 feet contains 30 to 70% limonitic gravels. Areas where depth of soil is more than 3 , 819 819 7/ 4‘“ 19— feet, the surface concretionary horizon is separated from bedrock by friable, nonplastic, yellowish clay. 19 r 22 19 1,7/ 21 44/7" 23 /E="/ 23 ROCKLAND Volcanic bedrock on gently dipping lava flows, steeply inclined breccias, cliff faces, steep to precipitous bouldery talus. Rock composes 50 to 90‘,” of surface area. 3 17 19 O 21 Kfi l1 4 27 MUCK AND PEAT Fresh-water marshes on coastal lowlands composed of various percentages of very dark-brown to black 17 25 1‘3_ELL:‘ organic silt (muck) and brown to reddish-brown fibrous residues of partially decomposed vegetation (peat); muck and peat lo Tzul‘E-‘TiZE horizon 4 to 15 feet thick; organic layer usually underlain by lime sands; water table at or a few inches above the sur- Coral I} face; reaction neutral to mildly alkaline. 41 17 Indicates swept depth area ”1 feet SHIOYA LOAMY SANDS Light-grey, light-yellow, and white calcareous loamy fine to coarse sands with dark organic 15 staining in the surface 8 to 15 inches; loose; excessively drained above the water table which averages about 15 to 20 inches below the surface; sand fraction composed of fragments of coral and other reef marine detritus; pH 8.0 8 18— to 8.5; occupies mostly long, narrow, discontinuous areas along low coastal terraces and parts of most reef islands; 818 18 27 1/7 ’” average elevation about 2 feet above high-tide level. if, ‘ Coral reef ”Ex/”(r FILL Areas along the low coastal terraces filled, stabilized, and paved with volcanic riprap rock, crushed volcanic rock, I 19 17 / 74”“ ,,, coral, and clay. Some areas, such as docks, seaplane ramps, and parts of some airfields, paved with portland cement 13 E 4,7 ill“ concrete; other areas paved with bitumen concrete; elevation from 1 to 10 feet and averages about 5 feet above I 7/ 7/ i‘ i h' h . — Cora§w b ig -tide level. I 25 15 < 42) COIE MANGROVE SWAMPS Shallow salt and brackish swamps along coasts and in embayments; vegetation mostly trees and 19 shrubs having branching aerial prop roots which usually form tangled, practically impenetrable barriers to foot troops 51 and to most vehicles; soils consist of loamy sand in the coastal areas and muck and peat, usually underlain by sand, in the 17 44 protected embayments. 28 513 17 3 11 Corzal 817 817 2, 17— SYMBOLS “Coral 1 16 «111’an Cliff 4553?? 19 30 2 M? .1 / -\,y Intermittent stream 15 co'aijffd7 _ ' ”U" 9” \ K‘ coeial 39 057 Soil sample site Pofiw [13 50 15 51 18 22 4:1” 1" t I) 23 18 18 21 19 2 29 I} (31) 2 11 4 17 g 315 1 ,6 16 lo 2‘ L9 E3 (9 2‘ 2‘ 19 17 17 11 22r30r __ _E}> 23 — 22’30’ '0 11 (63> 21 3 29 7 /\6@ 15 18 33 21 Coral \ \ 1 2 11 15 4 20 27 15 7’Y 815 815000m.N 3 15 17 16 21 21 ‘1 K A 2 19 Doral reef 33 19 ‘/'~,f-. 12 Coral reefg A 22 O 17 11 11 E Coral\reell\’ ; 1; 29 3 14 20 . .. . "7’ o w 13 10 7,2200, l Iraq-afi- LEMO 0L BAY , \ mCoral ( 7.22/00, 151'32’00” 339 OOOm.E_ 32/30” 340 341 342 343 35’00’ 344 % 346 348 37’30’I 351 151’39’30” 5 W855 Scale 1,25,000 . . 1 . Edition 2~AMS (AFFE) 1 E o 1$tatute Mile Sorls by James E. Paseur, 1954-1955. U.S. ARMY MAP SERVICE, FAR EAST - 577041 - R-15 - 12l58 - 3.40 Prepared under the direction of the Engineer, Hq AFFE/BA, by the U.S. Army Map Service, Far East. 1000 500 0 1000 2000 MEWS Compiled in 1957 by photogrammetric (multiplex) methods. Coastal hydrography compiled from USHO ' I i I i l i k 1 1r Chart 6049, 1944. Horizontal and vertical control established by Corps of Engineers, 1951. Names trans- 10‘00 1—1 l___[ 5234 H J 1000 2000 Yards [iterated in accordance with rules of the U.S. Board on Geographic Names. Major roads are classified by reconnaissance by the 64th Engineer Battalion (Base Topographic), 1952; other roads are classified from 1 O lNauticaI Mile source maps and aerial photography and are not verified by reconnaissance. Coastal vegetation are clas- ' ' r ' ‘ ' ‘ J COVERAGE D‘AGRAM 'NDEX T0 ADJO'N'NG SHEETS sified by reconnaissance by Military Geology Branch, Intelligence Division, Office of the Engineer, Hq AFFE/SA, with personnel of the U.S. Geological Survey, 1955. Map not field checked. CONTOUR INTERVAL lo METERS . . ‘ . VERTICAL DATUM- MEAN SEA LEVEL Soils data based on field Investigations and laboratory tests 1954-1955, compiled and prepared 4544 H NW by Military Geology Branch, Intelligence Division, Office of the Engineer, Hq, U. 8. Army Japan with personnel of the U. 5. Geological Survey. TRANSVERSE MERCATOR PROJECTION MAP 13 HORIZONTAL DATUM IS BASED ON THE ASTRONOMIC STATION NO. 2 (l95l ): m 7W ‘ I II ° I II 151 53 34 3 EAST OF GREENWlCH, 7 21 37,7 NORTH \ 4544 III SW 4544111 SE 4544 ll SW LEGEND HYDROGRAPHIC DATUM‘ APPROXIMATE LEVEL or LOWE ‘ - ST Low WATER . .‘ E V MAP 9 MAP 11 MAP 14 ms \\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\§\\§\\ \\ - BLACK NUMBERED LINES lNDICATE THE 1000 METER UNIVERSAL TRANSVERSE \\\QW§‘\V\W\&\\§ All wealher MERcATOR GRID. ZONE 56, INTERNATIONAL SPHEROID Q\W& K‘;¢g\\\\\\;\§ 4543 IV NW 4543 N NE 4543 I NW . . \. . hard surlace, two or more lanes wide NONE Builtup area WWWWWWE EEE,EE,EEEEWEW None THE LAST THREE ”lens OF THE GR”) NUMBERS ARE 0"”“9 §m§m§§§®§VR ‘:\“\$ [ ’ m _ 1 1 ..\ . \\‘\_\\\. loose or light surlace, two or more lanes wide EE EE None Church; School; Cemetery E, E .E 7E 3 I 1091": Wmm\‘\\\>\ MAP ‘0 MAP 12 MAlP—l15 \\:\‘\'\\ ._\ x \u hard surlace, one lane wide EEE EEEEEEEEEEE EE None Limit or danger line; Submerged reel EE Ag: 0 COMPILATION METHODS ‘ loose or light surface, one lane wide ,,,WE EEEE None wreck, Sunken, Exposed W, W WW WW, 4. M _ I 4 45’ Photo-planimetric Map Fair or dry weather, loose surface, two or more lanes wide E: Sunken rociis; foreshore llats . ”iiiiii + . 3mg 0 l l 0“ GRID IONE DESIGNATION: m QWE A STANDARD REFERENCE 0N . .- . . * OK on MiLs SBN THIS SHEET To NEAREST 100 METERS v Fair or dry weather, loose surface, one lane wide EE E E e . . -E E: Rocks have or awash; Reef E EEE , \,* 3 MILs 100,000 M. SQUARE IDENTIFICATION SAMPLE POINT: TRAIL JUNCTION A USHO Chart 5049 1944 (reliability good) Berg GLOSSARY t . k Carl track; trail WWWWWWW , _______ no) I1 ' , . ' ‘ ' moun ain, pea Depth Curves and Soundings m Fathoms W 7 ,9 2 mm Mm “mm“ 100,000 mm Aerial photography. l-Feb., July 1946, Z-Jan. 1949. Nom en bay Standard reuse railroad, smile track 7 —*—+—i— “we”; Dam, W, w" W Oth— 2.13)::3:33;15:33:15”;mLEW LP Oror en 7 anchorage Standard gauge railroad, double track WWE E E -li-—+i—-l+— point and read LARGE figures Iabelrngthe Unun en caper point p . 2’6” Salt evaporators E. E . ,, EE EEEEEWW V‘n“ LP line enter in thetop or bottom margin or Narrow gauge railroad, Single traclr EEEEEEE E EEE —i--T—- 11 APPROXIMATE nun DECLINATION 1955 on‘iheiineiiselr: , 43 , 3 ‘ ‘ FOR CENTER OF SHEET Estimate tenths from [Mine la 00 ril: 9 "3”“ “”39 railroad, “WW 0' "‘"It'p'e "a“ 77m ’ " / Rice Paddy; Marsh EEE , EEEEEEEEWEWEEE ANNUAL MAGNETIC CHANGE 1’ EASTERLV 3. LouierirsmonizoNTAt [‘lldline eztow . 2/ t d d LARGEt l b l h Power transmrssron line E E ,, EEEEEEW EEEEEEE ....... I. ’ mg Una diagram only to obtain numerical vain”. 52L" grilled: the 1:91 01px;; arrlzlllnlfhtof Spot elevation in meters, Checked; Unchecked I‘d ”'6 Nipa, Mangrove ivnifi’ ”Wife W To defer-mine magmlii: north lino, conned tho mum: "ll" SMALLER ”3""9’ dd”). 0" "‘9 “”3 "59”1 15 _ _ u H [II num er; tiles! If! of fin ml E t i t [n I d| [ 1: Wall; Levee; Cliff v 777” #777 W Waflfi EC] P'VO’ 90"" P °" '5' “WM “‘99 9' '5‘ MP the run coordinates. Use ONLY the “m” an 5 mm in m ”pm" 2 Waterwheel 0' mm Loc t d b l V Tower W00“: Scrub 7777777777 77777777777 with the veins of the angle between GRID LARGER-limes oi the and number; SAMPLE Rzrznznct; LP439152 . a 9 0 l“ ——~rw 0 Elm NORTH and MAGNETIC NORTH, as plofiod on "WW 315000 ii reporting beyond 18° in any uiieciian.1 PrinCIpal navigation light of lighthouse; Anchorage EEE * \f/ Tropicai grass; Coconut grove WWWW WW , , 0h- d-gm seal. a! the north odge of the map. - 9”," GM 1°" D""""'°"‘ “3 56NLP439152 U DOT SW, CAROL' N E ISLAN DS 1958 TRUK ISLANDS CAROLINE ISLANDS 125,000 1‘ o L N 11“ Military Geology of Truk Islands MAPIO Soils 151 ”3980” 7°22’00” d 1 814 . Bra» ,1] 3 ,Ainachang 813 812 811 20/00” (/ EN WISENIF b 2 3 22 coral oO 151°32'00” 339 32/30” 340 3111 342 343 wow 344 345 7322,00” I 17 /IO/5;.$ Coral ‘157 I. I. I V I - 0 I T W Coral reel 22 23 Carlal@\im/ C, _' 3 19 _, ajcora .' “ 19 - ' -: /ra / i ‘ 814 ‘4 hag-15:11 «<21-4 " 27 19 3' Coral 1 W 1‘ Q 22, 21 3 12 13 1‘ Coral ICTJraI 32121 ,, LEMOTOL BAY :E'i Coral reef 11- 17 Coral : I: I7 ,z-n‘I Coral reeI‘ZYI'E: 1 12 \f 5 13 29 23 813 a I 4 \3/ 11 23 22 3 27 18 12 11 22 1‘. , e ‘ 23 £0) 18 21 I; 17 . 15 39 4O 19 21 28 812 12 18 31 1 21 33 12 18 ‘ W‘ D». 24 . , , 11111 . .x idfiv 11 \\\ 11 1 a: ggf‘g‘?‘ _, is: \\\ __ (13"- ‘ 20/00” \\ 8 18‘\ / ,r”§\‘ coral \\\ \ 28 16 . @I \\‘\\ coral nun en Unikopi 12 “’ “x.\\ 14 24 23 \‘x [LICK HARBOR 29 23 \x \‘17\. 810 1O coral ‘\ 24 25 ii \ 3.6. 25 29\ sand and shells‘\\ 23 \ ‘ ~ 23 \‘s x’ s 17 \\\ «(1703‘ coral 809 -\ Q9 1@ ;, .\\ TRUK \i‘ \.\ 29 ' \\ \T\ 22 \ coral 1‘ \\ \ \.\ 25 23 19 19 \ I, 23“\ 808 08 “'3' F W ‘ 7 Q 16 I ( 11 ‘a I I coral coral \x i 1 o 28 \ / I“ a 3.60:“! Coral sand ‘1, ® \ 18 I coral 1 1 Coral 1 23 27 \ ‘1 sand I 5330 3 9 40 I, 4 I' ._a 21 19 sand -\ UNIT 12. - DESCRIPTION TRUK CLAY, less than 25% slopes Latosol on gently undulating to hilly slopes; reddish-brown and red clay; surface few feet usually granular, grading downward to massive structure; porous and well drained; friable, sticky; slightly acid to strongly acid in reaction; depth to volcanic bedrock 10 to 50 feet, surface 10 feet generally free of unweathered boulders. TRUK CLAY, 25 to 65% slopes Latosol on hilly to steep slopes, similar to 10 except the gradient is higher and the soil contains some boulders and rock outcrops. _________________ I ................. , »»»»»»»»»»»»»»»»»»»» SOILS MAP, TRUK ISLANDS .13., \ /09 810 1 24 a >>>>>>>>>>>>>>>>>>>>>> ———————————— *""““““" 25 EXPLANATION UNIT DESCRIPTION firm, Slightly plastic and “:L‘Mifgjm: face; reaction neutral to mildly alkaline. SHIOYA LOAMY SAN DS MUCK AND PEAT 1‘ Freshwater marshes on coastal lowlands composed of various percentages of very dark-brown to black —_ organic silt (muck) and brown to reddish-brown fibrous residues of partially decomposed vegetation (peat); muck and peat _ .1... horizon 4 to 15 feet thick; organic layer usually underlain by lime sands; water table at or a few inches above the sur— 809 808 Light-grey, light-yellow, and white calcareous loamy fine to coarse sands with dark organic staining in the surface 8 to 15 inches; loose; excessively drained above the water table which averages about 15 to \s 20 inches below the surface; sand fraction composed of fragments of coral and other reef marine detritus; pH 8.0 . / . . . - - - » d r t r ‘ Ia d ; Uliperu 1” 11 // 21 \‘s \ TRUK STONY CLAY, less than 25% slopes Stony Latosol with local areas of Lithosol on gently undulating to hilly to f-Sle 05:32:?” [2:33 gnfge'etnilgye 5151;120:1025; areas along low coastal terraces an parts 0 mos ree '5 n 5 sland) 13 '1 /' Coral Coral \ \ slopes, 1 to 10 feet thick over volcanic bedrock; 70% is reddish-brown to yellowish‘red clays; granular; porous and ave ag g ' \If /17 19 \x 20 well drained; friable, firm, and slightly plastic; slightly to medium acid in reaction. 30% is very dark-grey to dark- . . . . _ 8 807 V4; , a brown clay; strongly granular; very firm, plastic; slightly acid to medium acid in reaction; somewhat poorly drained; FILL Areas along the low coastal terraces filled, stabilized, and paved wrth volcanic riprap rock, crushed volcanic rock, 07 ‘ 4 1’, 31/ l SOBU REEFQ average depth to bedrock sbout 4 feet; estimated boulder content about 15%. coral, and clay. Some areas, such as docks, seaplane ramps, and parts of some airfields, paved wrth portland cement 51 I7\5~/L’\ /I 2 1 “he I , Coral concrete; other areas paved with bitumen concrete; elevation from 1 to 10 feet and averages about 5 feet above 7 / ‘1: ma ree . . W“ / I 2 % I 21 TRUK STONY CLAY, 25 to 65% slopes Stony Latosol with local areas of Lithosol on hilly to steep slopes, 1 to 30 feet h'gh't'de “we'- 7 1 Coral 2 E thick over volcanic bedrock; reddish-brown to red and reddish-yellow clay; granular; porous and well drained; friable, firm, . _ r slightly plastic to plastic; slightly medium acid in reaction; volcanic boulders common on the surface and compose about ‘ ‘_ MANGROVE SWAMPS Shallow salt and brackish swamps along coasts and In embayments; vegetation mostly trees and 20% Of the profile. Tfii‘gq ”Tit—4 shrubs having branching aerial prop roots which usually form tangled, practically impenetrable barriers to foot troops £10,113 9393 and to most vehicles; soils consist of loamy sand in the coastal areas and muck and peat, usually underlain by sand, in the TRUK STONY CLAY, over 65% slopes Stony Latosol and Lithosol on steep to very steep or precipitous slopes, similar protected embayments. 234 to 2E but contains more boulders in soil profile. ”’30” * SYMBOLS — W30” FEFAN SOILS Soil found mostly on gently undulating Slopes, 1 to 8 feet thick usually over either olivine basalt or _ 25 nepheline basalt; the surface 1 to 3 feet contains 30 to 70% limonitic gravels. Areas where depth of soil is more than 3 mwm Cliff 29 8 8060mm“ feet, the surface concretionary horizon is separated from bedrock by friable, nonplastic, yellowish clay. coral 06 ‘ /~/' Intermittent stream 4 ROCKLAND Volcanic bedrock on gently dipping lava flows, steeply inclined breccias, cliff faces, steep to precipitous . coral 23 bouldery talus. Rock composes 50 to 90% of surface area. 057 Soil sample Site I \ x l 4 8 VL \\ \\\ I\\ 27 “3 ‘i 13 19 3L6 x 111 \ 17 1. 15 I X I \ I , ° I \ ‘1 1 in 7°17’00’ I / . I “m I i \ I F ‘ 7°17Ioorr 151“32’OO” 339000m‘E. 32’30” 340 341 342 35’00” 344 345 346 P 348 37’30” 349 350 351 151°39’30” 347 ws55 5 Edition 2-AMS (AFFE) Prepared under the direction of the Engineer, Hq AFFE/BA, by the Us. Army Map Service, Far East. Compiled in 1957 by photogrammetric (multiplex) methods. Coastal hydrography compiled from USHO Chart 6049, 1944. Horizontal and vertical control established by Corps of Engineers, 1951. Names transliterated in accordance with rules of the US. Board on Geographic Names. Major roads are classified by reconnaissance by the 64th Engineer Battalion(BaseTopographic), 1952; other roads are classified from source maps and aerial photography and are not verified by reconnaissance. Coastal vegetation are classified by reconnaissance by Military Geology Branch, Intelligence Division, Office of the Engineer, Hq AFFEISA, with personnel of the US. Geological Survey, 1955. Map not field checked. Soils data based on field investigations and laboratory tests 1954-1955, compiled and prepared by Military Geology Branch, Intelligence Division, Office of the Engineer, Hq, U. S. Army Japan with personnel of the U. 3. Geological Survey. LEGEND ROADS All weather hard surlace, two or more lanes wide . . . None Bum-up area . loose or light surface, two or more lanes wide . . None Church, School; Cemetery hard surface, one lane wide None Limii ol danger line, Submerged reel loose or light sullace, one lane wide .. None Wreck Sunken; Exposed Fail or dry weather, loose surlace, two or more lanes wide ..,,:,..,,..,. Sunken rocks, Foreshore Ilals .... . Farr or dry weather, loose surface, one lane wide 7. ; Rocks here or awash, Reel . , , Carl track; trail . . .. .L. . _.__-L-_ Depth Curves and Soundings In Fathom: ... .. .. —+—+——+— Standard gauge railroad, Single hack 7,. L . Reserve”, Dam; Ditch 77777 Standard gauge railroad, double track ... . -h—f9—tt— a’s” Salt Narrow gauge railroad, single track ”LL, {‘11 Narrow gauge railroad, double or multiple track . Rice Paddy; Marsh .-. 7 W. Power transmission line Spot elevation in meters. Checked; Unchecked .. “‘6 "IAG Wall; Levee; Ciiii _. -, L.. L... .... m§fi§ Woods; Scrub ... Walerwheel of mill, Located obiect .., £1 010‘“ Principal navigation light 0i lighthouse; Anchorage L“ * 3/ Tropical grass; Coconut grove ,7, .. ... -.LW [:Il:l Nina; Mangrove Scale 1:25.000 1 1 5 0 1 Statute Mlle 1000 500 0 1000 2000 Meters I [—1 1—1 L—T Ib-—-I 1—1 1 J 1000 500 0 1000 2000 Yards [ I-—~l I—T T—l l—-{ I——-\\\\\\ \ \\\\\\'\V \\\\\ \ \\ \\\\\§§§K\ SSS 0§§§§ $§\ COMPILATION METHODS Photo-stereo Photo-planimetric k \1 I .1 Map A. USHO Chart 6049, 1944 (reliability good). Aerial photography; ll-Febq July 1946; Z‘Feb. 1947. INDEX TO ADJOINING SHEETS U.S. ARMY MAP SERVICE, FAR EAST - 577041 - R-15 - 12/58 - 3.40 4544 || NW MAP 13 4544 III SW 4544 III SE 4544 ll SW MAP 9 MAP 11 MAP 14 4543 IV NW 4543 IV NE 4543 l NW MAP 10 MAP 12 MAP 15 m GLOSSARY Bergwfi._ ..... ‘__. mountain, peak Nom en bay Oror en anchorage Unun en_____fi_._fl‘acape, point TOL NW, CAROLINE ISLANDS TRUK ISLANDS U ID 10 “11‘ S E Military Geology of Truk Islands o o o , CAROLINE ISLANDS 1225,000 0° 2° 3° 4 5 6° 7 MAP ii Sells 1 11111 I 1 1 .1 i 3 3 . 151°39'30” 352 40/00r353 354 355 356 357 42/30! 358 359 360 361 362 45100: 63 364 55 151 4710011 e 1 ,1 1 1 7'27’00" 7 27 00 30 J 29 ! , T I ‘ I 1 coral E 29 t 34 1 1 s , I cgrsal ‘ T 24 coral l 1 1 war);] 32 {/25\\ I cgrsai l 27 coral ‘1’ 5 \F I 34 29 1 /1&1 I 21 I coral I 27 23 l 1 323 7 7 33 32 7 7 -... 7 7 1,7,. - 7 823 TEES-'5 2 3 7 A E coral 23 . E 7 1 1 . SOILS MAP TRUK ISLANDS 1 l 29 1 ’ coral l ‘ 3° 31 l T R U K L A G 0 0 N EXPLANATION , 31 I 24 25 UNIT DESCRIPTION I g l cor I 30 1 a TRUK CLAY, less than 25% slopes Latosol on gently undulating to hilly slopes; reddish-brown and red clay; surface few 17/x\\ 1 feet usually granular, grading downward to massive structure; porous and well drained; friable, firm, slightly plastic and 29 1/ / 11 1 sticky; slightly acid to strongly acid in reaction; depth to volcanic bedrock 10 to 50 feet, surface 10 feet generally free 27 ,‘(29 [4’ I of unweathered boulders. ,’ car [I 28 ’ ,1 I 7 7 822 822 22 m... 47 - ~ 7 » 2,22!1 l1 , TRUK CLAY, 25 to 65% slopes Latosol on hilly to steep slopes, similar to 1D except the gradient is higher and the ”’3‘ I\ ,l ‘ 19 soil contains some boulders and rock outcrops. I \\_l, 1 29 I = 1 21 , . . . ; cm] ' I) TRUK STONY CLAY, less than 25% slopes Stony Latosol With local areas Of Lithosol on gently undulating to hllly "‘""”' '"’""“'”""‘"""‘"“"’"""’::::: """ “ "7' """""""" "mm ““““““““““““““““““““““““““““ 4‘ """""""""""""""""""""""""""""""""" a, slopes, 1 to 10 feet thick over volcanic bedrock; 70% is reddish‘brown to yellowish-red clays; granular; porous and 28 27 4/,//’ , Io ‘. 20 well drained; friable, firm, and slightly plastic; slightly to medium acid in reaction. 30% is very dark-grey to dark- 71 //7x 7 58 59 8 6O ‘1' 61 brown clay; strongly granular; very firm, plastic; slightly acid to medium acid in reaction; somewhat poorly drained; //,,r”/ 53 I ‘ coral 11 average depth to bedrock shoot 4 feet; estimated boulder content about 15%. ,,,e 1 l 28 2‘ 18 l 1 ‘1‘ 14 // / Coral ree 1 1 TRUK STONY CLAY, 25 to 6500 slopes Stony Latosol with local areas of Lithosol on hilly to steep slopes, 1 to 30 feet " ,4.:_Coral reef TRUST TERRITORY OF THE PACIFIC ISLANDS ‘ K\ g thick over volcanic bedrock; reddish-brown to red and reddish~yellow clay; granular; porous and well drained; friable, firm, 1 1, 1 2. 2E _ . 28 (U.S.A. ADMINISTRATING AUTHORITY) ‘ 16 \\ cora slightly plastic to plastic; slightly medium acid in reaction; volcanic boulders common on the surface and compose about coral Item reef i 1 17 \ 20% of the profile. 821 821 21.7 TRUK STONY CLAY, over 65% slopes Stony Latosol and Lithosol on steep to very steep or precipitous slopes, similar 26 to 2E but contains more boulders in soil profile. Coral Z4 FEFAN SOILS Soil found mostly on gently undulating slopes, 1 to 8 feet thick usually over either olivine basalt or nepheline basalt; the surface 1 to 3 feet contains 30 to 7000 limonitic gravels. Areas where depth Of soil is more than 3 feet, the surface concretionary horizon is separated from bedrock by friable, nonplastic, yellowish clay. ROCKLAND Volcanic bedrock on gently dipping lava flows, steeply inclined breccias, cliff faces, steep to precipitous 16 bouldery talus. Rock composes 50 to 90% of surface area. 17 12 24 coral 15 MUCK AND PEAT Fresh-water marshes on coastal lowlands composed of various percentages of very dark»brown to black 8 25,00, ’ organic silt (muck) and brown to reddish-brown fibrous residues of partially decomposed vegetation (peat); muck and peat 20 8 E” horizon 4 to 15 feet thick; organic layer usually underlain by lime sands; water table at or a few inches above the sur- 25,00, 20 face; reaction neutral to mildly alkaline. 13 SHIOYA LOAMY SANDS Lightgrey, light-yellow, and white calcareous loamy fine to coarse sands with dark organic staining in the surface 8 to 15 inches; loose; excessively drained above the water table which averages about 15 to 20 inches below the surface; sand fraction composed of fragments of coral and other reef marine detritus; pH 8.0 / to 8.5; occupies mostly long, narrow, discontinuous areas along low coastal terraces and parts of most reef islands; \\ .E. 1\ average elevation about 2 feet above high4tide levels 7 \ 1 n n\Nukunao \ 15 4‘ ‘1 11141 ‘ FILL Areas along the low coastal terraces filled. stabilized, and paved with volcanic riprap rock, crushed volcanic rock, \ \ l4 INTI ,1. WW coral, and clay. Some areas, such as docks, seaplane ramps, and parts of some airfields, paved with portland cement \1 13 \1 16 coral 31‘3le II IIIII, concrete; other areas paved with bitumen concrete; elevation from 1 to 10 feet and averages about 5 feet above ,‘. Coral reef 1 coral 1 23 11 . . -": , . 1 high-tide level. Unun en Chbna 1 ‘~ 819 819 . u...,..1... N...” 7 » Coral reef; Egg , MANGROVE SWAMPS Shallow salt and brackish swamps along coasts and in embayments; vegetation mostly trees and \flj/ 17 shrubs having branching aerial prop roots which usually form tangled, practically impenetrable barriers to foot troops 21 5 641 ’5 , 70 and to most vehicles; soils consist of loamy sand in the coastal areas and muck and peat, usually underlain by sand, in the 5 /, / ’ 4‘\\ 1) 7 21 protected embayments. 1 // 16 1 ' / 22 coral ‘1 I——l 7' I ’ 7/ SYMBOLS 17 15 Cliff 18 W§ 13 , 16 ' 18 8 “m""m coral W 11 1' :2 1l /- .7» Intermittent stream 17 14 ,' 13 ; , I ~ I 1 ’/ ‘1 n 8 818 " : Wang? H 16 I 057 Soil sample site ‘1 x 1’ ' 1 w 18 1' ‘ 111 '1 » i 49 3 1 1 1 \\ \17 1 I " 15 I 1‘41?- 1 1 1 1, ‘5. . , 1 san i I I I ‘\ h 21 4 \ ‘ Q 17 E 15 \\ \\ j 1" (77 I sand and shells \\ \\ 17 . / x 1 1 18 ’0, [I I Sand 1' @ \‘1 I \\ ‘1‘ 1 1 l 1 7 E 1‘ I ‘ \¥ 1/ \ \ I, I 7, I 11 \\ \1 1 1 l 1 2 12 ‘, c1311 18 I I ‘ \ \ 8 817 1 I7 1 12 g m 1, 1‘ 17 l ‘1 22 I .3_3. i \‘1 \ l i ,' ‘1 \‘ ‘1 l I 1 \\ 1 I I I \ \1 , 1 1, : 1‘ \ 1 , , , l9 1 \ l T j I 3 \\ \\ l l \ 1 . 17 1 13 1 \ 21 181 53 19 54 55 I 56 ‘ 3 ‘1‘ 64 15 65 13 1‘ ‘ 1_1 indicatesfswept depth area in feet I, 11 1\ ,\ 1 , I 1‘ 1 1 , , 1 I \1 II I \\ \1 . \ 1 l \\ 1 ‘1 17 l I "490‘“ \‘ 1 , 1 ”.1 = 16 1" ”"7 W" i“ ‘ 816 ,7 01 7.. I l 816 i ‘1 16 E T T WM I u ‘ K w '\fl// \ ‘1, 18 l 1 i‘ x z : DOT ROA \ l ‘ (anchorage) 13 1\ 22 1 ° 55 \\ l |_r \ 13 I 17 \ 7 sand I1 12 // 29 \\\ /,/22 \\ 15' E coral , 15 xi“ IQ l ra / 22'30' — 1/10 1 / C" 13—31 1 rrrrr ”Md/67,8144 22/30” \77/ 1 _(>>_k7_ 77 \ l 4, l 17 21 i l 815 815000m.N_ \ 1517 I 12 \\ 1 11 \ l , \ \X E 17 \°/—\7\// 4 \ 8 c l /Coral reef \0\ . \‘1 lo 13 18 i 8 ’07 ("a 62 ' /16 i 6“ I (12 9 9 ‘0 Cora 13 ' [5 4 16 . Coral 7°22'00' E“ I \ I I I M 7°22ioo” 1: I / ' J 151 3W30”352000m.E. 4000'353 354 355 356 357 4230’ 358 359 360 36245’00” 363 364 365 151 4W00’ W855$ Scale 125,000 . . 1 , Edition 2-AMS (AFFE) 1 a o IStatute Mile Soils by James E. Paseur, 1954-1955. U.S. ARMY MAP SERVICE, FAR EAST - 57-041 - R~15 - 12/58 - 3.4C Prepared under the direction of the Engineer, Hq AFFE/SA, by the US. Army Map Service, Far 100° 50° 0 10$ 2000 Mews East. Compiled in 1957 by photogrammetric (multiplex) methods. Coastal hydrography compiled [ 1000 500 O 1000 2000 Yards from USHO Chart 6049, 1944. Horizontal and vertical control established by Corps of Engineers, 1 H 1—1 H F r ,_, fl 1951. Names transliterated in accordance with rules of the US. Board on Geographic Names. % 0 . . Maior roads are Classified by reconnaissance by the 64th Engineer Battalion(BaseTopographic), 1 ,1Nauncalwe 1952; other roads are classified from source maps and aerial photography and are not verified COVERAGE DIAGRAM INDEX TO ADJOINING SHEETS by reconnaissance. Coastal vegetation are classified by reconnaissance by Military Geology Branch, Intelligence Division, Office of the Engineer, Hq AFFE/BA, with personnel of the U.S. CONTOUR INTERVAL IO METERS WITH SUPPLEMENTARY CONTOURS AT 5 METER INTERVALS ET 7 “HT Geological Survey, 1955. Map not field checked. VERTICAL DATUN: MEAN SEA LEVEL 4544 || NW :Oilingiita base? on I:ield irll'ivlestigations and'laborattfafry tests 1954-1955, co-lmpibedsarli‘d prerared TRANSVERSE MERCATOR PROJECTION § MAP 13 thh larigynneeloo‘fgtxhe La"; ,Gegltcelliig:ln;:ravrsion, 0 me Of the Engineer, q' ‘ ‘ rmy apan HORIZONTAL oATUN is BASED ON THE ASTRONOMIC sTATloN No. 2 (1951): mm \ p ' ' g y' 151‘53'34.3' EAST OF GREENWICH. 7'21’37,7/' NORTH k“~:€‘4$$\"&4\\;\\}‘¥3\"§ §xw§§§ 4544 III SW 4544 III SE 4544 ll SW LEGEND HYDROGRAPHIC DATUM 1 APPROXIMATE LEVEL OF LOWEST Low WATER §4§\\\§.\4§4\°\§§\{§\ ems. sxsss.nsi\ \4 “ \w \ \ MAP 9 MAP 11 MAP 14 . \ ‘.'\ i ‘ ROADS BLACK NUMBERED LiNEs INDICATE THE 1000 METER UNIVERSAL TRANSVERSE \\§@‘§‘§§§§§§ \\ 77. ,._. 7.- t a A GRID, ZONE 56, INTERNATIONAL P \i‘ ‘ .‘ “‘ "‘" All wea her ERC TOR s HEROID ‘m‘mgfi‘g 4543 IV NW 4543 N NE 4543 1 NW hard surface, two or more lanes wide 7, None Burltrup area 77 7777 None GM THE ”ST THREE DIG”: OF THE GRID NUMBERS ARE own“ \\\\\\\\\\\\ r 7 , 4 \ s , . - - 7777 i r item; \ 4% \ MAP 10 MAP 12 MAP 15 loose or light surface, two or more lanes wide ,7 , None Church, School, Cemetery . & \\\\\\\\\\\\‘\\\\\\\ V ’7‘} hard surface, one lane Wlde 777777 ,, None Limit of danger line; Submerged reel 7 4.45, COMPILATION METHODS loose or light surface, one lane wide 77, 7 None Wreck: Sunken; Exposed 7 o‘io’ on Photo-stereo Photo-planimetric Map . A , a4 ulLs GRID IONE DESIGNArloN: To GIVE A STANDARD REFERENCE 0N ‘ E fair or dry weather, loose surface, two or more lanes Wide 77 Sunken rocks, Foreshore flats on 55” "“5 SHEET To NEAREST 100 Mums W . . ‘ 0 GLOSSARY h Fair or dry weather, loose surface, one lane wide 7 Rocks bare or awash; Reef , 3 IILS 100,000 M. SQUARE IDENTIFICATION SAMPLE rorNT: ; SCHOOL A. USHO Chart 6049, 1944 (reliability good), Uzolrnezn egg: 03:: 1 » . . ,1 . Cart track, trail 777.77 _._---_ Depth Curves and Soundings in Fathoms 7 ,,,,,,,,,,,, 7 ,3) 2 1.11m We“ identifyinz 100,000 mm, Aerial photography: Feb., JUIY 1946 SI d d 'I d, I t k ,7 ,—+—f—t— . square-n whichthe pointlies: LP an ar gauge mi 108 smge rac ‘ E RESEWOIIZ Darn; DIICh 77777 a- z, Locflg'irfiVERTICAL and line :0 LEFT of Standard lauge rallroadhdouble track 77777 2"” Salt evaporators 7 _g:: LP 3:23;:[318213334]ngie:rnhr::'r':iin.t 2: "allow 83ng ialIIO-‘id. SIHEIC track 7 q—tTI— APPRoxmATE MEAN DECL1NATION 1955 on the line itself: 589 . , 3 ' FOR CENTER or SHEET Estimate tenths from grid line to point: Narrow gauge railroad, double or multiple track Rice Paddy; Marsh 77 ANNUAL “AGNETIC CHANGE 1/ “sun“ 3. Locate lirstHORlZONTAL 1nd line aELow . . . l/ _ point and read LARGE figures labeling the Power transmissmn line 7 7 . __.__7. . Ugo diagram only to obtain numerical values. line either in the left or right margin, or Spot elevation in meters‘ Checked Unchecked r 72.15 x, 5 Nlpa; Mangrove To dimming magnetic north fine conned rho "W0“ "I“ SMALLER "W“ 0' '"Y 0M“! II"! itself: 15 - 1 4 ' ‘ .1 .1 ' (rid Numb"; "I!“ I" for “Ni"! Estimate tenths from grid line to point: 4 Wall; Levee; cliff 7, 77 _mai1E P"°' P°'"' P °" "" '°"”' “9" °‘ ”‘° "'°P the full coordinates. Use 0qu the Wt h I I II l d b ¢ 10'" woo“; Scrub wifh Me value of "lo angle bow GRID LARGER figures of tho grid number; SAMPLE REFERENCE: LP589164 aervr ee 0 mi; ocate o ject 7 0 example: . .. , NORTH and MAGNETIC NORTH, as plofiod on 815 000 If reporting beyond 18 in any direction, Principal navigation light of lighthouse; Anchorage 7 * \T/ Tropical grass; Coconut grove , "Iodngreo scale antic norrh edge of fin rnop. —‘ ”M” 6“" 1"“ D’si‘m'” ”‘ 56NLP589164 U DOT SE, CA R0 Ll N E ISLAN DS 1958 TRUK ISLANDS ’1 ’0 1 ‘1 T1 ‘ Military Geology of Truk Islands 0 1 CAROLINE ISLANDS 125,000 0° 2° 3° 4° 5 6° 7° MAPIZ 80115 t ‘ l I-- 121.114.111.11 JINLlJLLlIJiJJm‘L-rl - 3r 3r 3: 3 3 3 r 151'47100' 151'39/301/352 401001 353 354 355 356 .17 42/3011 :18 .19 60 61 62 45 0011 7.22100! 7°22’00” \ 11 Kara - 11 7 21 K / IO .7 12 01"“ C coral ._ 12 17 _ 2 1 a "'"ral Q °\ 11 / IO \ Coral 16 95 814 ~ - - - - 7 * .1- \ 63 \on °"" as _5 ¥5A 15 _- ,,,,,,,,,,,,,,,,,, , ,,,,,,,,,,,,,,,, 1 12 ’7 1 °—/ 22 61 3, 16 2 10 )0 I 16 1 /“ J I 54 .0 21 I I) T” 8 ,- l - 23- 7- 1° 24 - ~ 17 13 813 I / \o / Q I 19 3 I coral 17 21 coral 60 G) 6 3 coral 7 /O 23 24 coral 21 2 coral 812 Coral 7W _ , ,. 7“ “Wiwfifi _.-.-.,,,-.- - 7 . __ - 7 12 - . _ .- 812 ,0 l I S L A N D S 6 1 2° I coral /“ 19 . ‘ j) I r__i indicates swept depth area in feet I r I 6 I 16 3 I 3 .19.. 1 Q9 ,1 24 a I coral 3W 8 I 11 I , 21 5 I 18 p; 2010011 20’00" 22 (ff? 5 l SOILS MAP, TRUK ISLANDS G O 0 2, N EXPLANATION 1 29 UNIT DESCRIPTION 2 I TRUK CLAY, less than 25% slopes Latosol on gently undulating to hilly slopes; reddish-brown and red clay; surface few 810 810 ’ feet usually granular, grading downward to massive structure; porous and well drained; friable, firm, slightly plastic and ‘ 3O sticky; slightly acid to strongly acid in reaction; depth to volcanic bedrock 10 to 50 feet, surface 10 feet generally free of unweathered boulders. TRUST TERRITORY OF THE PACIFIC ISLANDS TRUK CLAY, 25 to 65% slopes Latosol on hilly to steep slopes, similar to ID except the gradient is higher and the (U.S.A. ADMINISTRATING AUTHORITY) soil contains some boulders and rock outcrops. I TRUK STONY CLAY, less than 25% slopes Stony Latosol with local areas of Lithosol on gently undulating to hilly f slopes, 1 to 10 feet thick over volcanic bedrock; 70% is reddish-brown to yellowish—red clays; granular; porous and 27 1 well drained; friable, firm, and slightly plastic; slightly to medium acid in reaction. 30% is very dark-grey to dark- I brown clay; strongly granular; very firm, plastic; slightly acid to medium acid in reaction; somewhat poorly drained; average depth to bedrock sbout 4 feet; estimated boulder content about 15%. 23 . . . . E, 809 809 r e - - - - - - - - r - » TRUK STONY CLAY, 25 to 65% slopes Stony Latosol With local areas of Lithosol on hilly to steep slopes, 1 to 30 feet thick over volcanic bedrock; reddish-brown to red and reddish-yellow clay; granular; porous and well drained; friable, firm, I slightly plastic to plastic; slightly medium acid in reaction; volcanic boulders common on the surface and compose about ' , I . . I 20% of the profile. ,x" 23 \ i__i indicates swept depth area ir feet , 2 l " ____________ 2/ I \\ 24 V 24/ 19 II \\ ‘ I TRUK STONY CLAY, over 65% slopes Stony Latosol and Lithosol on steep to very steep or precipitous slopes, similar / i l X I to 2E but contains more boulders in soil profile. . 1 , Ag 21 I. , \ ' / 1 \ I I z I \\ - 21 I FEFAN SOILS Soil found mostly on gently undulating slopes, 1 to 8 feet thick usually over either olivine basalt or 21 1 \ I‘: I nepheline basalt; the surface 1 to 3 feet contains 30 to 70% limonitic gravels. Areas where depth of soil is more than 3 r \\ I feet, the surface concretionary horizon is separated from bedrock by friable, nonplastic, yellowish clay. \\ . \ I \\ - - -- ,1 ROCKLAND Volcanic bedrock on gently dipping lava flows, steeply inclined breccias, cliff faces, steep to precipitous 808 ' ’ "’ “19‘” W A“ “ "7' 7 A 08 \I I bouldery talus. Rock composes 50 to 90% of surface area. i 1 x, 29 : é ‘ 2 . 1 I 33 \\ O m... MUCK AND PEAT Fresh-water marshes on coastal lowlands composed of various percentages of very dark-brown to black 1 I1 I’ ‘4 \\ :‘L’ 12$“: organic silt (muck) and brown to reddish-brown fibrous residues of partially decomposed vegetation (peat); muck and peat f I 1 \ I I... _j..‘1“_.:i.37_‘ horizon 4 to 15 feet thick; organic layer usually underlain by lime sands; water table at or a few inches above the sur- 21 I I \\ face; reaction neutral to mildly alkaline. 52 53 54 57 58 59 6O 61 . . , :24 I21 , 22 i ,\ SHIOYA LOAMY SANDS Light-grey, light-yellow, and white calcareous loamy fine to coarse sands with dark organic 17 Isand I § 17 \\ 20 staining in the surface 8 to 15 inches; loose; excessively drained above the water table which averages about 15 to j i I \I 1 20 inches below the surface; sand fraction composed of fragments of coral and other reef marine detritus; pH 8.0 Is 1 1I I I 1 \\ ' I 21 to 8.5; occupies mostly long, narrow, discontinuous areas along low coastal terraces and parts of most reef islands; 4 I1 I i I \\ average elevation about 2 feet above high-tide level. A, . g I 22 I 1' ‘ £1 c l9 x . .. . . . . fl 807 807 -- . _- _---‘... A, ,__ , , E , ”AM“ - W -- _ \ A 1 1~—~- » r - U7 , . - 4 -- , s; - ‘ ' * ---- - ' ‘ ‘ , FILL Areas along the low coastal terraces filled, stabilized, and paved With volcanic rlprap rock, crushed volcanic rock, I I 19“ ‘s-\ 20 coral, and clay. Some areas, such as docks, seaplane ramps, and parts of some airfields, paved with portland cement I, I(island) 1 ‘\\ 17 ‘s-\ I; concrete; other areas paved with bitumen concrete; elevation from 1 to 10 feet and averages about 5 feet above I 15 ' 1 “x- high-tide level. 21 i 19 2 ~ .-\ 10 , 1 1 , \s- I 3 i 1 \‘\-\ . lo I I I 21 I 18 ~\\ MANGROVE SWAMPS Shallow salt and brackish swamps along coasts and in embayments; vegetation mostly trees and 19 I . I coral I ‘*~-\ shrubs having branching aerial prop roots which usually form tangled, practically impenetrable barriers to foot troops I I i_i indicates swept depth area in] feet ‘\\-\ and to most vehicles; soils consist of loamy sand in the coastal areas and muck and peat, usually underlain by sand, in the I I I 7 ‘\ protected embayments. 1 1. Io ‘\ 23 ; 1 \ \- 1 2‘ coral i 18 7 ‘r- SYMBOLS 17‘30/1 l— I l 3 I I ,1 \\ — 17’30” I ' (1) 1 :1 1° ,’ \ WWW"? Cliff . 1 z I 1 ,’ 8 25 l 1 W , -- -- WW -- - - .29, -- -.-.-- .- -- . - W-- .-.---.-. -- .--.-.1.W--.- _ 06 806000m.NI . 06 I I1 \\ I: 21 06 I/ / -\» Intermittent stream I 21 I 3 \ 0 r 23 r “"11 29 217 \x ”I r’ . l I I: \\ .13. 23 I,’ 037 Sorl sample site 1 I 29 ’ \\\ . ,’ ; I 13 ‘1\\ I/ fl I I i ,’ \\ , l 2‘ 23 I 41 l 22 I \\\ II, I 23 , Coral 1‘16 , . e l . 25 “rs-E : 23 ,1 l Icoral §% 1 , . / 7 28 251 /3\ 24 “K 1 I 22 ’l I II 3° 3°?” 27 711710011 ‘ ‘5 I n ‘“ 1 1 1 “~‘ ’ 1 7'171001/ 151’39’30” 352000rn.EI 40/00" 353 354 355 356 357 42’30” 358 359 360 P 36245100” 363 364 365 151'47’00” 361 W856 5 Scale 125,000 Ed‘t'on 2—AM (AFFE‘ l - , . _ _ . _ _ _ I I S / IL I 3 I I I 1 ~_ _I Statute Mlle SOIIS by James E. Paseur, 1954-1955. U.S. ARMY MAP SERVICE, FAR EAST 57 041 R 15 12/58 3,4C Prepared under the direction of the Engineer, Hq AF'FE,’8A, by the US. Army Map Service, Far 10:10, 533* I“ 1000 __________ ”M200 Mae's East. Compiled in 1957 by photogrammetric (multiplexi methods and from 1:55,180, USHO 1000 500 0 1000 2000 Yards Chart 6049, 1944. Coastal hydrography compiled from USHO Chart 6049, 1944. Horizontal and I H 1...; 1...; ,_4 H W..- _:_____-_--._ vertical control established by Corps of Engineers. 1951. Names transliterated in accordance 1 1 O lNautIcal Mile with rules of the U.S. Board on Geographic Names. Coastal vegetation are ClaSSIfied by reconnais- r 1 I AI I ; I . M ._ , I I sance by Military Geology Branch, Intelligence Division, Office of the Engineer,Hq AFFE/8A,with personnel 1 ‘ ' ' COVERAGE DIAGRAM INDEX TO ADJOINING SHEETS ;‘ IhedL‘S' Sew?“ T?” 1955’ Map “‘“d'f': “:de I 1954 1955 I d d d CONTOUR INTERVAL lo METERS WITH SUPPLEMENTARY CONTOURS AT 5 METER INTERVALS oi s ata ase on iel investigations an a ora ory es s - , compi e an prepare , , . VERTICAL DATIJM MEAN SEA L«VEL by Military Geology Branch, Intelligence Division, Office of the Engineer, Hq, U. S. Army Japan ‘ L 4544 ll NW with ersonn l of the U. S. Ge lo ical Surve . ., . ° ° ° 5 y TRANSVERSE MERCATOR PROJECTION MAP 13 HORIZONTAL DATUM IS BASED ON THE ASTRONOMIC STATION NO. 2 (1951): 151.53’343' EAST OF GREENWICH. WEI/37.7, NORTH 4544]“ SW 4544i“ SE 4544IISW LEGEND HYDROGRAPHIC DATUM : APPROXIMATE LEVEL or LOWEST Low WATER MAP 9 MAP 11 MAP 14 ROADS BLACK NUMBERED LINES morons TiiE 1,000 METER UNIVERSAL TRANSVERSE All weather IERCATOR GRiD. ZONE 56. INTERNATIONAL SPHEROID I THE LAST YHREF DISITS OF THE GRID NUMBERS ARE OMITTED 4543 Iv NW 4543 IV NE 4543 I NW hard surface, two or more lanes M118 W __,- None Burltup area -..--2_-_W.____._.. I“ loose or llghl surface, two or more lanes wide We None Church; 3611001. CENIE'Y —«——e————v—-~———-—a ‘ MAP 10 MAP 12 MAP 15 hard surface, one lane write ,__...___..._ None Limit of danger line, Submerged reel _m-W2W-. loose or light suilace, one lane wrde . None Wreck Sunken: {11103911 *«s-w———— . I “‘5, COMPILATION METHODS f 1 k k‘ F n ll l o '0 0R GRID IONE DESlGNATlONI TO GIVE A summer) REFERENCE 0N air or dry weaiher, loose surface, two or more lanes W168 , - Sun en roc s, ores ore a s .- on 34 MlLS 56N THIS “m to NEAREST mo METERS Photo-stereo Map Fail or dry weather, loose surface, one lane write - r. - Rocks bare or awash, Reel 3 "11-5 100,000 M. SQUARE lDENrIFlCATlON 3.1an: pomr; x 112 WW r“ GLOSSARY . HP “*1" Oror en anchora e “a" ”a“ ““II -- W..W_,_.--- “~' --_ Dem“ “”95 3”” “mm” '" ”mm - — I--____W,_ 1. Read letters idenhlying 100,000 motor I A, 1;55,130, usrio Chart 5049, 1944 (reliability good). ”mm "I cape poi?“ . _+__..__.¢_ i ii liln tl : LP , . Stand“ gauge railroad. 5mm ”3”" -1 Reservoir; 0am, Ditcll 2. :22:,3;Jénnéffg,dfiem LE” 0, Aerial photography: July 1946. Standard gauge railroad, double track —+——~#—-—-‘H— LP point and read LARGE figures labeling the 2’5” Salt evaporalms line e-ltlel in the top or bottom marlin, or Narrow gauge railroad, single track W- APPRoxmAT: MEAN DECLINAHON 1955 onlhelmertself: 53 2‘.” FOR CENYER or SHEET I (stimatelenthstrom 1nd line to point; I 5 Narrow gauge railroad, double or multiple track Rice Paddy; Marsh ANNUAL uAchrrc CHANGE 11 EASTENLY M“’”"’“"— 3. Locale first HOR120NIAL (rid line BELOW I _ I . _ _ pom! and read LARGE figures labeling the I PW“ transmissmn “"3 - / Use diagram only to obtain numerical values. _~W____‘ I,“ an,“ ,,, "H, MD, “1M mm,“ 0, Spot elevation in meters Checked, Unchecked "Mé “11.6 Nina; Mangrove "“ ___ __ 7° d"°""1”° ”"9”“ ”0"“ “h" ‘W m“ :fi:°::,,f::,.sm::‘:,2‘flf‘5’15? 1 MW mum"; , ‘34 fi I PIVO’ POifl' ”P” on the south edge of». map til i ll 6 t U ONLY "It Est/mate tenths Iorrr aridllne to oornt. Wall, Levee, Clllf _,_‘_ _. ._.._.., 1Q . , 5 “ “’0’ ""51 39 9 I ¢ Tower Woods, Scrub W _ will the value of the angle between GRID LARGEIR figures of the zrldonumbe.’; 5AM”; "gram“ ”3535134 Waterwheel of mill, Located abroad 13 4 ’ ' Noam and MAGNETIC NORTH, a, planed.” mm“: 80600 11 reporting beyond 15° in any arrociwnI * 3r Tropical grass, Coconut grove._______________ [:1 D the degnn scaled the north edge of the "up. _ ””1" GM 2°” D'SIFMM’L '5: SGNLP535134 TOL N E, CAROLI N E ISl—AN DS Prmcrpal navtgatlon light 0l lighthouse Anchorage _.._ 1958 TRUK ISLANDS CAROLINE ISLANDS 125,000 369 151'47'oor 366 47/30' 367 368 Military Geology of Truk Islands MAP 13 Soils MOEN NW 37'2 00 20 30 40 5o 60 7o INLLLLILLJLILLLJ 5mm 376 -74 377 378 379 151°54’30’ \1 U1 370 371 373 374 3 50'00" 7'32ioo' o . I H /—/o V. ,/21 22 17 coral iii 24 28 27 xx 29 .——\ 24 \ \ \ Uncovers 1 IOOLLX‘ \ ’0 56 \\ \ -» am 23 sand and shells “F“ \ 34 Coral 30 \ “>232 w.-. .. I 6 | coral 4,- 19’ / ./ 3 / (2 l I -. \ \ \ 4 \ , \ coral ra reel K \\ . , \ \ \ \\ 1 \‘\ 35 coral \ i / / 37 coral 30 coral 832 32 coral 27 27 28 coral 35 33 sand 36 coral 33 33 sand 35 36 I 831 31 ,9 , . 23 x EXPLANATION DESCRIPTION UNIT TRUK CLAY, less than 25% slopes 830 of unweathered boulders. TRUK CLAY, 25 to 65% slopes soil contains some boulders and rock outcrops. \ TRUK STONY CLAY, less than 25% slopes slopes, 1 to 10 feet thick over volcanic bedrock; 70% well drained; friable, firm, and slightly plastic; slightly to medium acid 30’00” TRUK STONY CLAY, 25 to 65% slopes 829 20% of the profile. TRUK STONY CLAY, over 65% slopes to 2E but contains more boulders in soil profile. FEFAN SOILS ROCKLAND bouldery talus. Rock composes 50 to 90% of surface area. 828 MUCK AN D PEAT face; reaction neutral to mildly alkaline. SHIOYA LOAMY SAN DS average elevation about 2 feet above high-tide level. FILL 827 high-tide level. MANGROVE SWAMPS protected embayments. SYMBOLS «minim Cliff 826 /-~\/v Intermittent stream 057 Soil sample site A 1 I I I I \ l . 66 67 68 I I l 30 / 29 \ 5. // 29 in reaction. SOILS MAP, TRUK ISLANDS Latosol on gently undulating to hilly slopes; reddish‘brown and red clay; surface few feet usually granular, grading downward to massive structure; porous and well drained; friable, firm, slightly plastic and sticky; slightly acid to strongly acid in reaction; depth to volcanic bedrock 10 to 50 feet, surface 10 feet generally free Latosol on hilly to steep slopes, similar to 1D except the gradient is higher and the Stony Latosol with local areas of Lithosol on gently undulating to hilly is reddish-brown to yellowish-red clays; granular; 30% is very dark-grey to dark- brown clay; strongly granular; very firm, plastic; slightly acid to medium acid in reaction; somewhat poorly drained; average depth to bedrock sbout 4 feet; estimated boulder content about 15%. Stony Latosol with local areas of Lithosol on hilly to steep slopes, 1 to 30 feet thick over volcanic bedrock; reddish-brown to red and reddish-yellow clay; granular; porous and well drained; friable, firm, slightly plastic to plastic; slightly medium acid in reaction; volcanic boulders common on the surface and compose about Stony Latosol and Lithosol on steep to very steep or precipitous slopes, similar i Soil found mostly on gently undulating slopes, 1 to 8 feet thick usually over either nepheline basalt; the surface 1 to 3 feet contains 30 to 70% limonitic graveis. Areas where depth of soil is more than 3 feet, the surface concretionary horizon is separated from bedrock by friable, nonplastic, yellowish clay. Volcanic bedrock on gently dipping lava flows, steeply inclined breccias, cliff faces, steep to precipitous 16 Fresh-water marshes on coastal lowlands composed of various percentages of very dark-brown to black organic silt (muck) and brown to reddish-brown fibrous residues of partially decomposed vegetation (peat); muck and peat horizon 4 to 15 feet thick; organic layer usually underlain by lime sands; water table at or a few inches above the sur- Light-grey, light-yellow, and white calcareous loamy fine to coarse sands with dark organic staining in the surface 8 to 15 inches; loose; excessively drained above the water table which averages about 15 to 20 inches below the surface; sand fraction composed of fragments of coral and other reef marine detritus; pH 8.0 to 8.5; occupies mostly long, narrow, discontinuous areas along low coastal terraces and parts of most reef islands; Areas along the low coastal terraces filled, stabilized, and paved with volcanic riprap rock, crushed volcanic rock, coral, and clay. Some areas, such as docks, seaplane ramps, and parts of some airfields, paved with portland cement concrete; other areas paved with bitumen concrete; elevation from 1 to 10 feet and averages about 5 feet above Shallow salt and brackish swamps along coasts and in embayments; vegetation mostly trees and shrubs having branching aerial prop roots which usually form tangled, practically impenetrable barriers to foot troops and in most vehicles; soils consist of loamy sand in the coastal areas and muck and peat, usually underlain by sand, in the 29 coral 38 I coral 35 coral 35 76 L_, indicates swept depth area in feet 77 34 coral 30 35 \I (D sgfia porous and 35 30 34 coral 30 , ; 34 LAGOON coral 34 sngd 23 sand and shells olivine basalt or L3 i o x/“\ 9 \l\ 10 ‘I‘ Q 33 , 35 30 l 22 shells 5 / 8 l \\ coral // 16 / 34 . VLLLAL WALLZBHH ,._ ..._..,_....___., / ' I 29 / ‘1 2: C 7s (.0 r~ > Z O \ (n coral I 12 i I ll coral! 7'0 28 28 30 825 ~ '25 19 coral 31 coral <1. 29 I17 log, 3 ”2 L233 ( I 0 (a a slcéd 7’32'00’ 832 831 830 30 00’ 829 828 825 27’30’ 27130r — 2 23 I 27 21 8240mm“. “WM“, 24 23 _ -- - , , . , _ 5 ‘ , ‘ . .2 , . 824 . __.. - . — ,x _, "r k . , . , . 7,2700, i . -‘ , , ilig/Zfi) w .. : . M Afi‘k 737100” 151.4700, 366 000m}; 4730, 367 368 369 370 \0 p 52'3er :75 277 378 379 151’54’30" W8565 Edition 2»AMS {AFFE} Prepared under the direction Of the Engineer, Hq AFFE 8A, by the U.S. Army Map Service, Far East. Compiled in 1957 by photogrammetri: (multiplex) methods. Horizontal and vertical control established by Corps of Engineers, 1951. Chart 6048, 1944. literated in accordance with rules of the US Board on Geographic Names. reconnaissance by the 64th Engineer Battalion {Base Topographic), 1952; other roads are classified from source maps and aerial photography and are not verified by reconnaissance. Coastal hydrography compiled from USHO Names trans- Maior roads are classified by Coastal vegetation are clas- sified by reconnaissance by Military Geology Branch, Intelligence Division, Office of the Engineer, Hq AFFE/BA, with personnel of the US. Geological Survey, 1955, Map not field checked. Soils data based on field investigations and laboratory tests 1954-1955, compiled and prepared by Military Geology Branch, lntelligence Division, Office of the Engineer, Hq, U. 8. Army Japan with personnel of the U. 8. Geological Survey. ROADS All weather hard surlace, two or more lanes wide loose or light surface, two or more lanes with hard surface, one lane wide loose or light surlace. one lane wide fair or dry weather, loose surlace, two or more lanes wide , 7:, r. , ~ Farr or dry weather, loose surface, one lane wide Carl tracli; trail . , . L... Standard gauge railroad, srngle track , , ,, ,, , Standard gauge railroad, double track ,, ,, , Narrow gauge railroad, Single lracli Narrow gauge railroad, double or multiple tracii Power transmissron line . Spot elevation in melers: Checked; Unchecked ,, , Wall; Levee; Cliff ,, L , Waterwheel of mill; Located obiecl Principal navrgation light ol lighthouse; Anchorage , .. LEGEND None 8th up area None Church, School. Cemetery None Limit ol danger line, Submerged reei None Wreck Sunken, Exposed . e ”77 Sunken rocks; foreshore llats . . Rociis bare or awash, Reel ___..____- Depth Curves and Soundings ll'l Fathoms -—i-—i—i——- "' " Reseriarr; Dam; Ditch Wt— 2’s” Salt evaporators "a —"""""—“‘ Rice Paddy. Marsh x M6 x,“ Nipa, Mangrove , _. _W§/A§ Woods, Scrub 1:1 Ufower ‘2 * KM Tropical grass, Coconut grove , 375 ISlatute Mile US. ARMY MAP SERVICE, FAR EAST - 57-041 — 9-15 » 12/58 - 3,48 Soils by James E. Paseur, 1954-1955. 1000 500 0 1000 2000 Meters l l——t l——t L—-—I i———«I I—i Irv————-—-————-—————-——-—~i 1000 500 0 1000 2000 Yards I F—-f i——-‘\ \ \W $3 MAP 10 MAP 12 MAP 15 \\\\\\Q§\‘\\\\\ , I 1 COMPILATION METHODS Photo-stereo Photo-planimetric Map GRID ZONE DESIGNATION: To GIVE A STANDARD REFERENCE ON I \\ " ,- THIS srim ro Nsiiritsrioo this & § I ‘ ' ,I I I Oror en GLOSSARY anchorage 100.000 MSQUARE WENHFICATION SAMPLE POINT: + SUNKEN ROCK A. USHO Chart 5043, 1944 (reliability good), Unun en___,#*,#____..., ..____cape, point LRead letters identifying 100,000 meter AerIaI DthOEFaphyl FELL. JUIY 1945- snuare in which the pornt lies: LP .Locate lrrst VERTICAL and line to LEFT ol point and read LARGE irguies labeling the N LP line either in the top or bottom margin, or APPROXIMATE MEAN DECLINATION 1955 on the lineitseli: 75 FOR CENTER OF SHEET Estimate tenths from grid line to point: 4 5‘" ANNUAL MAGNETIC CHANGE 1' EASTERLY Locate first HORIZONTAL grid line BELOW point and read LARGE figures labeling the Una diagram only to obtain numerical vulva. IIl'IE either In the left or right margin, or IGNORE the SMALLER figures of any To darermine Inagnnfic north lino, conned the d b on IheIrnerlseil: 23 . . ,, ,, s" mm H: these are tor finding Estlmale tenths iroi-n gridlrnetopont: 3 pIVO' point P on the town edge of ”In mop thP lull coordinates. Use ONIY the I with me value of the angle between GIID LARGER liizures of the ind number; SAMPLE REFERENCE: LP764283 NORTH and MAGNETIC NORTH, a: pIoNnd an example: 824 000 'l vaportinz beyond 15’ in any direciwfli the dear” scale of the north edge of the wrap, — We” GI'd 1°“ Designation, 33' 55NLP764283 M 0 EN N w, CARO LIN E ISLAN DS 1958 TRUK ISLANDS CAROLINE ISLANDS 125,000 M Q E N 8 RV Military Geology of Truk Islands 00 20 3o 40 5o 60 70 MAP I4 SOIIS L LLLLLLLLLLLLLLLILLIJ 151"47roor 355 47/30" 367 368 369 37O 371 5000” 372 7°27Ioor 4 52/30” 376 i _ . . ‘ , I” - . I” ‘wi v‘gr 22 z . . , f ,. ~ I , crew 10 - 2 . ‘ . ‘ the fits,“ . I9 ' I . - » -—-»* , . , : F i , E >(, I, . < 999'» . " 7r , 1 _. , -~‘ 4 o - 1 L121 E OROR Ely Noam CHO I : I I 379 151-54120! 2-27Ioor .23 SOILS MAP, TRUK ISLANDS ” / I, EXPLANATION r’ 1’13 _ I , UNIT DESCRIPTION TRUK CLAY, less than 25%, slopes Latosol on gently undulating to hilly slopes; reddish-brown and red clay; surface few feet usually granular, grading downward to massive structure; porous and well drained; friable, firm, slightly plastic and sticky; slightly acid to strongly acid in reaction; depth to volcanic bedrock 10 to 50 feet, surface 10 feet generally free of unweathered boulders. A; \ __= . r7 823 ‘ / O sand \ 23 ‘ A ‘ 3 UCLA ROAD 11 roRore EN NEPUN '5 I I r , Il .5 4 I I TRUK CLAY, 25 to 65% slopes Latosol on hilly to steep slopes, Similar to 10 except the gradient is higher and the soil contains some boulders and rock outcrops. 61? [7/ 1?. ” .- 822 iv i to? r? TRUK STONY CLAY, less than 25“U slopes Stony Latosol with local areas of Lithosol on gently undulating to hilly , slopes, 1 to 10 feet thick over volcanic bedrock; 70% is reddish-brown to yellowish-red clays; granular; porous and ‘ 20 I well drained; friable, firm, and slightly plastic; slightly to medium acid in reaction. 30% is very dark-grey to dark I, /’ l__9J “+3 brown clay; strongly granular; very firm, plastic; slightly acid to medium acid in reaction; somewhat poorly drained; ‘ I ,/ coral / 822 5. ‘ , i=5. . o coral / M ’ 55120}? EN EP UP W a y 7Q) W ‘A 9 average depth to bedrock sbout 4 feet; estimated boulder content about 155%). \‘\\coral 0/3 , t \ n O a n: ._. H .— m \ x \ \ \ \ \ \ \ \ TRUK STONY CLAY, 25 to 65% slopes Stony Latosol with local areas of Lithosol on hilly to steep slopes, 1 to 30 feet \ 2 E thick over volcanic bedrock; reddish-brown to red and reddish-yellow clay; granular; porous and well drained; friable, firm, ‘ . ._ . . i" »- ., . " ~ 5 78 ” 79 ‘ . . f, \ gr, .1 “A. ‘6‘“ f . .7 -. . _ :» : 2 slightly plastic to plastic; slightly medium acid in reaction; volcanic boulders common on the surface and compose about ‘ \ ' 20% of the profile. 2F TRUK STONY CLAY, over 65% slopes Stony Latosol and Lithosol on steep to very steep or precipitous slopes, similar .L_I_5___ , 821 __ . » to 2E but contains more boulders in soil profile. “ I‘A ““““ 4,.bfible 1 4.2.5“ , W _. . I / , 821 _ , , ~ 5 ,. ,r (”1% ,> \1: t ' . - Sorl found mostly on gently undulating slopes, l to 8 feet thick usually over either ' 4. Wm FEFAN SOILS olivine basalt or I r nepheline basalt; the surface 1 to 3 feet contains 30 to 70%, limonitic gravels. Areas where depth of soil is more than 3 I feet, the surface concretionary horizon is separated from bedrock by friable, nonplastic, yellowish clay. ‘i ROCKLAND Volcanic bedrock on gently dipping lava flows, steeply inclined breccias, cliff faces, steep to precipitous bouldery talus. Rock composes 50 to 90% of surface area. 31 30 sand r M .... .1. MUCK AND PEAT Fresh-water marshes on coastal lowlands composed of various percentages of very dark-brown to black 1\ '— _ - organic silt (muck) and brown to reddish-brown fibrous residues of partially decomposed vegetation (peat); muck and peat , M_ .1. __..... _ horizon 4 to 15 feet thick; organic layer usually underlain by lime sands; water table at or a few inches above the sur- 820 face; reaction neutral to mildly alkaline. , 25/00r '— SHIOYA LOAMY SANDS Light-grey, light-yellow, and white calcareous loamy fine to coarse sands with dark organic staining in the surface 8 to 15 inches; loose; excessively drained above the water table which averages about 15 to - 20 inches below the surface; sand fraction composed of fragments of coral and other reef marine detritus; pH 8.0 to 8.5; occupies mostly long, narrow, discontinuous areas along low coastal terraces and parts of most reef islands; average elevation about 2 feet above high-tide level, 31 27 ” coral / oral « 13 N 820 r , (@115; 25'001/ FILL Areas along the low coastal terraces filled, stabilized, and paved with volcanic riprap rock, crushed volcanic rock, ,. 7‘ I . coral, and clay. Some areas, such as docks, seaplane ramps, and parts of some airfields, paved with portland cement ‘ . concrete; other areas paved with bitumen concrete; high-tide level, elevation from 1 to 10 feet and averages about 5 feet above 4’ ' V \ 24 \ ’ ' 'l 'r sand I‘I1165heI v" V \ \\ A 47 (’I ‘ .. .. l U” ‘3 .n MANGROVE SWAMPS Shallow salt and brackish swamps along coasts and in embayments; vegetation mostly trees and a" 7 W" 9",.N9‘WW0 819 —— ”kg _ shrubs having branching aerial prop roots which usually form tangled, practically impenetrable barriers to foot troops r351??? ail and to most vehicles; soils consist of loamy sand in the coastal areas and muck and peat, usually underlain by sand, in the I I / KM L’MSI. protected embayments. - 8 ~ \ , 19 \\ I_J 0 \ / I \ I t ’ “an 33 coral SYMBOLS 1"" "T" “m Cliff ' , 29 32 /"'~) Intermittent stream 21 16 057 Soil sample site , 15 818 18 19 22 sand 818 \ X 22 i. TRUK ISLANDs‘fitx TRUST TERRITORY OF THE PACIFIC ISLANDS g: 23 22 I6 (U.S.A. ADMINISTRATING AUTHORITY) I7 817 uindicates swept depth area in feet 17 coral 10 816 816 22’30’I 22’30” 3% Le x x 1 \\ ,3] 815 000m“. r - ., m N-un ,/l\/ o 3 I M 'bfl \’l '5’ '. 815 18 Rand // I Q) : Clara-all - ETEN ANCHORAGE // ' ram" ciIrZal (JCT/yfiuw . Gong/(213 €32” // IE 7.22.00” r ““5 , w . ,V 5“~3\24 g L “ 17 ~. / 151°47’00” 366000m.E. 47'30" 96‘ 367 371 50’00" 372 0, \f/i , , ’ 7°22loo” 374 P 5230” 376 379 151'54'30” 375 W856 8 Scale 1:25,000 Edition 2-AMS (AFFE) 1 . . 1 2 o 1$tatute Mlle Soils by James E. Paseur, 1954-1955. U.S. ARMY MAP SERVICE, FAR EAST - 57-041 - R-15 - 12/58 - 3.4c Prepared under the direction of the Engineer, Hq AFFE/BA, by the U.S. Army Map Service, Far East. 100° 50° 0 1000 2000 Meters Compiled in 1957 by photogrammetric (multiplex) methods. Coastal hydrography compiled from USHO L1ooo 500 0 1000 Charts 6048, 6050. 1944. Horizontal and vertical control established by Corps of Engineers. 1951. Names , ,_, ,_, ,__, ,___, ,__, 200° Yams transliterated in accordance with rules of the Us Board on Geographic Names. Major roads are classi- _ , ‘fied by reconnaissance by the 64th Engineer Battalion (Base Topographic), 1952 and reclassified from 1 0 lNautrcaI M'Ie aerial photography dated 1955; other roads are classified from source maps and aerial photography and 1 l I L COVERAGE DIAGRAM INDEX TO ADJOINING SHEETS are not verified by reconnaissance. Coastal vegetation are classified by reconnaissance by Military Geology Branch, Intelligence Division, Office of the Engineer, Hq AFFE/8A, with personnel of the U.S. Geological CONTOUR INTERVAL IO METERS \\:\‘ \Vw“§\§ 7 Survey, 1955. Map not field checked. VERTICAL DATUM: MEAN SEA LEVEL \§‘\\‘\‘~‘ 3' I 4544 ll NW .N \Q‘: .\ \ . Soils data based on field Investigations and laboratory tests 1954-1955, compiled and prepared TRANSVERSE MERCATOR PROJECTION \ . ' MAP 13 by Military Geology Branch, Intelligence Division, Office of the Engineer, Hq, U. 5. Army Japan HORIZONTAL DATUM IS BASED ON THE ASTRONOMIC STATION No. 2 (1951): ‘ ~.\ ‘ ' ~~ - , wrth personnel of the U. 5. Geological Survey. 151‘53/34.3' EAST OF GREENWICH. 7'2l’37.7' NORTH ‘ 4544 “I sw 4544 “I SE 4544 H 5w LEGEND HYDROGRAPHIC DATUM: APPROXIMATE LEVEL OF LOWEST LOW WATER ROADS MAP 9 MAP 11 MAP 14 All th BLACK NUMBERED LINES INDICATE THE 1.000 METER UNIVERSAL TRANSVERSE wea er MERCATOR GRID, ZONE 56. INTERNATIONAL SPHEROID ‘ hard sum“! two N more lanes wide 3 LANE: Buillrup ma %% THE LAST THREE DIGITS or Tn: GRID NUMBERS ARE ourrrzo 4543 IV NW 4543 N NE “ 4543 I NW loose or light surface, two or more lanes ride __ 38:22.: ChULClI; School; Cemetery _..—_——_ 3: I093] 6N MAP ‘0 MAP 12 I MAFEJS hard surface, one lane wide —— Limit oi danger line; Submerged reel _ I "I' I loose or light surface, one lane wide —=—=—: Wreck: Sunken; Exposed , , 4'45 Fair or dry weather, loose surface, two or more lanes wide __ Sunken locks; Foreshore llals 0.09, OR GRID ZONE DESIGNATION: To cm A STANDARD REFERENCE 0" . . 0“ 56N Tins SHEET To NEAREST 100 METERS GLOSSARY Farr or dry weather, loose surface, one lane wide ======== Rocks have or awash; Reel 3 urns 3‘ "'LS looooo M SQUARE IDENTIFICATION SAMPLE POINT' ; SCHOOL ”0'“ on b" Cart "a“ "a" Depth Curves and p in “moms ' ‘ ‘ A. USHO Chart 6048. 1944 (reliability good). Oror on anchorage . . _—' LRud letters identifying 100,000 meter 8' USHO Chart 6050' 1944 (reIIBbIIIty-goom' Unun all _ . _ . .___—CID€, WI"! Standard gauge railroad, single track —I-—I—r— Reservoir Dam‘ Ditch @— saumrn which the pornl IIeSZ LP Aerial photography: Feb.. July 1946. . . . _ 2. Locate first VERTICAL grid line to LEFT of Standard gauge railroad, double track -¢I-—IIT-H— point and read LARGE figures labeling the Narrow a e ‘l d ‘ | 1 k a . Salt "worm“ — I—P line either in thetop or bottom margin, or K ”K ”"03 . 3m“ '39 —————— T— 11 APPROXIMATE MEAN DECLINATION I955 nnthelmeitsoll: 78 . . . > FOR CENTER OF SHEET Estimate tenths from grid line Io paint: 1 Narrow gauge railroad, double 0' multiple track I RI“ PaddYV Marsh ——_ A ANNUAL MAGNETIC cums: l' EASTERLV a, Locatellrst HORIZONTAL grid line BELOW Power transmission line WW ’7‘ h" , _ , ‘ point and read LARGE figures labeling the — _ . .. M Use diagram only to obialn numerical vaIues. line either in the left or right margin, or Spot elevation in meters: Checked; Unchecked . no ms "'93' ° ‘ " To determine mognelr'c norrh line, connect rho IG'JORE fl: SVLLER lizl'lres orally on thellne itself: . . . 16 Wall: Levee: cull __.__ ._mar3§ Woods. 8mm ED pivoI point --r~ an The my». 9an or The map f; £51038.“sz 1;; am: tsumrrerermsrrom znd lneroromu 8 Waterwheel 0' mill; Located object 9 on)“, . —————-— wrlh rha value of Ike angle between GRID wistful» 0H"! ind number; SAMPLE REFERENCE: Lp731158 ‘ * D [3 NORTH and MAGNETIC NORTH, as pIoffed on - 315000 ii reporting beyond 13° in any direction, Principal navigation light ol lighthouse; Anchorage _ 3/ Tropical grass; Coconut grove _ Ihe degree scale a, rho "or", edge or Ihe map, — We“ W110“ DOMINION '51 56NLP781168 MOEN SW, CAROLINE ISLANDS Military Geology of Truk Islands - M N N‘W CAROLINE ISLANDS 1:25,000 ‘ 0° 2° 3° 4° 5° 6° 7° MAPIS Soils 151'47/00! 366 47/30!I 369 370 371 50/00” 8 379 151°54'30” 7'22’00” - 772100” a?” is 10 17 LI/ 231/ 23 / All ,7—7/ ,_g_r_r§N ANCHORAGE ,1 ” 22 “““““ ‘\ A9. / 19 oral 17 coral 814 814 I (I: ‘P i / Te 5 0R0]? [{N FANIP3 """" (fa lé“a‘r駒 ._ —————— 52* "a ._ . 1 ~ 29 4 : 2 coral 813 18 _sand‘ {I +' \ -- nobvers 8 Q if ‘:'+,;Liiroi coral \l 8 coreigqefi/ l ‘Coral i 79 / x' ,/ ‘ \ 20 fl 7 Un 0350001er 3.31 /7I, /:// , 15.51 \‘ \\ x9; coral 13 \\ //, "x, i sand I - 24 SOILS MAP, TRUK ISLANDS I , I, I L... 12 i I 812 EXPLANATION OROR E F ’N I‘ I' 16 i i 23' cgrzal DESCRIPTION com I‘ I , °°" .33. l l TRUK CLAY, less than 25% slopes Latosol on gently undulating to hilly slopes; reddish-brown and red clay; surface few I' 'l ’ :3 feet usually granular, grading downward to massive structure; porous and well drained; friable, firm, slightly plastic and Un'coyers, ncovers 3 feet sticky; slightly acid to strongly acid in reaction; depth to volcanic bedrock 10 to 50 feet, surface 10 feet generally free ’I Ilclofa‘i of unweathered boulders. [,1 II 29 I’ I! \\‘\ send TRUK CLAY, 25 to 65% slopes Latosol on hilly to steep slopes, similar to 1D except the gradient is higher and the (I / 1T\\\\\\ soil contains some boulders and rock outcrops. II [I \\\:\\\\ I I In ‘\\ \c\\- TRUK STONY CLAY, less than 25% slopes Stony Latosol with local areas of Lithosol on gently undulating to hilly I, I; CO .I 10 \QI‘\5"3\\ 18 Coral slopes, 1 to 10 feet thick over volcanic bedrock; 70% is reddish-brown to yellowish-red clays; granular; porous and 11 I i sign ~\ \\\ \ coral ;’ 811 well drained; friable, firm, and slightly plastic; slightly to medium acid in reaction. 30% is very dark-grey to dark- moral W 22 I; If \\\\\\ Uncover: 1,117: brown clay; strongly granular; very firm, plastic; slightly acid to medium acid in reaction; somewhat poorly drained; T ' . coral [w/I \\\ L\\\ 3 average depth to bedrock sbout 4 feet; estimated boulder content about 15%. Unun en Winrkof [13, \\\ \\\ zoroorr __ cam 15 1 7 -' 6 y"? \\ ‘\\:~" 20’00” ., 12 \I \\ \. TRUK STONY CLAY, 25 to 65% slopes Stony Latosol with local areas of Lithosol on hilly to steep slopes, 1 to 30 feet 1/167/ ’9 29 \\\ thick over volcanic bedrock; reddish-brown to red and reddish-yellow clay; granular; porous and well drained; friable, firm, [/2 [/9 9 I slightly plastic to plastic; slightly medium acid in reaction; volcanic boulders common on the surface and compose about [I ‘\1\/ I, [I 18 9°” 20% of the profile. [,1 [II I/ cum I 7 I I TRUK STONY CLAY, over 65% slopes Stony Latosol and Lithosol on steep to very steep or precipitous slopes, similar 13 i .2), l 15 [I (1’ TRUST TERRITORY OF THE PACIFIC fSLANDS to 2E but contains more boulders in soil profile. F I: o (I, / (U.S.A. ADMINISTRATING AUTHORITY) 31 an en anmono I I / FEFAN SOILS Soil found mostly on gently undulating slopes, 1 to 8 feet thick usually over either olivine basalt or i <5) 18 III I, 30 nepheline basalt; the surface 1 ,to 3 feet contains 30 to 70% limonitic gravels. Areas where depth of soil is more than 3 i coral ,1/0 810 810 feet, the surface concretionary horizon is separated from bedrock by friable, nonplastic, yellowish clay. 1O .. .. .. 'l (I; r 31 OROR EN KUKUWU i [I I,’ V sand and shells ROCKLAND Volcanic bedrock on gently dipping lava flows, steeply inclined breccias, cliff faces, steep to precipitous ; / I N bouldery talus. Rock composes 50 to 90% of surface area. 12 an Unufu i T R U K // (II I S L A D S I /I [I ’ 33 MUCK AND PEAT Fresh-water marshes on coastal lowlands composed of various percentages of very. dark-brown to black ’ 15 (,1 l/ 17 organic silt (muck) and brown to reddish-brown fibrous residues of partially decomposed vegetation (peat); muck and peat 16 I, III horizon 4 to 15 feet thick; organic layer usually underlain by lime sands; water table at or a few inches above the sur- é; sand arid shell/s! / T R I I Ff L A G O 0 N I face; reaction neutral to mildly alkaline. /,/’ \\7‘T»\ 6 I ~ // l I( \‘\\‘a\ ‘, Q], i SHIOYA LOAMY SANDS Light-grey, light-yellow, and white calcareous loamy fine to coarse sands with dark organic 13 ,/ 11/ [I ~\\\\ -33 ‘, 51 I' staining in the surface 8 to 15 inches; loose; excessively drained above the water table which averages about 15 to 2/ \ / I’ 17 \\\ é; / l '\ 4 X, 20 inches below the surface; sand fraction composed of fragments of coral and other reef marine detrrtus; pH 8.0 12 r IE. (} \——" to 8.5; occupies mostly long, narrow, discontinuous areas along low coastal terraces and parts of most reef islands; 15 809 809 I, 8/’ average elevation about 2 feet above hightide level. \cor l/I \_’ FILL Areas along the low coastal terraces filled, stabilized, and paved with volcanic riprap rock, crushed volcanic rock, 29 ‘ 7‘ coral, and clay. Some areas, such as docks, seaplane ramps, and parts of some airfields, paved with portland cement Q, concrete; other areas paved with bitumen concrete; elevation from 1 to 10 feet and averages about 5 feet above 28 \ ,_-\ high-tide level. / I \\ 30 (69‘ . MANGROVE SWAMPS Shallow salt and brackish swamps along coasts and in embayments; vegetation mostly trees and 18 \\ \iajfy’l £9 _ i + shrubs having branching aerial prop roots which usually form tangled, practically impenetrable barriers to foot troops um", en Nepwba'u ‘2 § " and to most vehicles; soils consist of loamy sand in the coastal areas and muck and peat, usually underlain by sand, \\ 3 18 / in the protected embayments. \Ir‘ 1:“ 4| \ // 35 r 3 r \ core // 42 x x , I, 64 ,’ \ / 5—1 28 SYMBOLS I —I x . - I 22 ) \ m f \ / o x/o\ \ 308 I WW“ / /\ ‘ 08 It I i 3. 12 , /‘ I 8 . 19 \ 808 , \_/ 1 \ ’ l 2’ \ mnnmmr cm 29 /,/ 2) \\ 16 I“ <3: 5; k/ 21 \J, ,9 cm, \ ’ \ / \\ /"\) Intermittent stream SM”: 11/ 15 18 \\ \ 29 ’ \ 23 a I a , \ I 3 7 151 53 30” 3 379 151 54 30” , \ 1 037 Soil sample site 33 / 24 \\ 7°17’00” \ or 7 ~ 78 7017100” 0 11 \\\ , _____ l shells [I l . \o / \\ Taigfiéfiarrd R I \ \\ / “ \ \ . X 66 11/ 2i \‘I 67 33 68 69 l/ 52 s / \\ P' D‘% AW" mind Unun a Nukanapxegnl ‘, coral / I / \ 1 \ 805 305 . \\ 23 \\ ,x’ ’ * 2 \ l \\ \~‘__,’—’ / I \ ' \62 \\ .21 C39 13 U U" 9" > EN NUKANAP I, 31 [I’ 4‘ Ne imokuf ' 19 a: / 27 , 29 ’l @\I so] 1 24 . 807 O7 , O7 33 ,’ /I 28 ,1, 12 _ 15 33 I' .0 coral II I’ 7 25 I‘ 804 804 30 TSIS A \n 30 I' . ”7/ 17’30” —— I’ ' / 17'30” ’ / I I I l / l 19 I c/ 32 27 6' 806 a 000m. 06 . O 21 t 06 N. 28 r/ 1 [I m”: a 3 I‘ core / 7°16’OO’/—— _ 7°16’OO” \\ \\ .A/J /’ / Faneu Island Uf/ \ 3‘ 35 "’7 1 ’ fi / \ 9 i ”'3' shells 37 33 I 28 ‘1 /5 22 z/ / , 11 \Q gravel and shells mus I / 11 7s: // I /T / ROR EN SAPOU 23 l 1 / / /\‘// 2/ 4 I 55 i 1x 2‘ 3 25/ I 803000m. u, .1 303 /I/ ’ I i 4 III a “4 I i” ‘ 44 /’ 45 / V990, ‘, B ‘I 1 1 [I 33 \ I ‘—‘ I _ 9 c 52 4 1,, , 22 31 I a x I 30 R i I ‘oral / , / 7'17Ioor ’ ' o a , - ’ 221% 7°17Ioo” 151.47'00” 366000m-E 473°" 367 368 369 370 371 50/00” 377000m. E. 151 53’ 30” 378 379 151 54 30” 52/30” 376 379 151°54Igor/ 1:856 5 Scale 1:25.000 dltlon 2-AMS (AFFE) 1 . 1 2 . , 0 15mm Mile SOIIS by James E- Paseur, 1954-1955- U.s. ARMY MAP SERVICE, FAR EAST - 57-041 - R-15 . 12/58 ~ 3.40 Prepared under the direction of the Engineer, Hq AFFE/8A, by the U.S. Army Map Service, Far East. 1°00 50° 0 1000 2000 Meters . Compiled in 1957 by photogrammetric (multiplex) methods. Coastal hydrography compiled from USHO L 10—0: H $0 H Ho Charts 6048, 6050, 1944. Horizontal and vertical control established by Corps of Engineers, 1951. Names [ 1—4 H H H H 1000 2000 Yards transliterated in accordance with rules of the US Board on Geographic Names.{ Major roads are classi- % ‘ . , fied by reconnaissance by the 64th Engineer Battalion (Base Topographic), 1952 and reclassified from 1 0 lNautIcal Mile aerial photography dated 1955; other roads are classified from source maps and aerial photography and a ‘ COVERAGE DIAGRAM iNDEX T0 ADJOINING SHEETS are not verified by reconnaissance. Coastal vegetation are classified by reconnaissance by Military Geology \ \\ “v Branch, Intelligence Division, Office of the Engineer, Hq AFF'E/8A, with personnel of the Us. Geological CONTOUR INTERVAL ‘0 METERS WITH SUPPLEMENTARY CONTOURS AT 5 METER INTERVALS ‘3‘“ W Survey, 1955. Map not field checked. VERTICAL DATUM: MEAN SEA LEVEL “‘\ 4544 ” NW Soils data based on field investigations and laboratory tests 1954.1955, compiled and prepared TRANSVERSE MERCATOR PROJECTION MAP 13 by Military Geology Branch, Intelligence Division, Office of the Engineer, Hq, U. 3. Army Japan HORIZONTAL DATUM IS BASED ON THE ASTRONOMIC STATION NO. 2 095” with personnel of the US Geological SurveY- 151'53’34.3” EAST or GREENWICH. 7'2I’37.7” NORTH 4544 ll! sw 4544 III SE 4544 II sw LEGEND HYDROGRAPHIC DATUMi APPROXIMATE LEVEL OF LOWEST LOW WATER MAP 9 MAP 1] MAP 14 ROADS All th BLACK NUMBERED LINES INDICATE THE l.000 METER UNIVERSAL TRANSVERSE m a @% MERCATOR GRID. ZONE 56, INTERNATIONAL SPHEROID 4543 IV NW 4543 Iv NE 4543 I Nw hard surlace, two or more lanes wide . ' ”N" Built-up area I. w G" . THE LAsT THREE DlGlTS or THE GRID NUMBERS ARE OMITTED \ loose or light surface, two or more lanes wide 3 ”N" Church; School; Cemetery ‘..‘ 9'7"] \ \\ MAP 10 MAP 12 MAP 15 , , k H hard surface, one lane wide _i —— Limit oi danger line; Submerged reef _-- COMPILATION METHODS . , n r We“ Sunken, Exooscd ___ 0.", 40:5 Photo-stereo Photo-planimetric Map GLOSSARY GRID ZONE DESIGNATION: To GIVE A STANDARD REFERENCE on Q -. . _. L 3 $415 I“ '4'” 55M nus SHEET TO NEAREST 100 METERS \\\\\\\\\\\\\\ .. .. ,. . . . 3W" °L e8! mono M.souARE IDENTIFICATION SAMPLE POINT: t CHURCH A. USHO Chart 6048, 1944 (reliability good). nun en capo. WM B. USHO Chart 6050, 1944 (reliability good). Aerial photography: Feb., July 1946. loose or light surface, one lane wide Sunlien rocks; Foreshore flats Fair or dry weather, loose surface, two or more lanes wide _ lioclis bare or awash; Reel ___7L.A_-E in Falhoms Fair or dry weather, loose surface, one lane wide Depth Curves and Cart track; trail Standard gauge railroad, srngle track Reservorr; Darn; Ditch Standard gauge railroad. double traclr 40—H— . _ 2/.” Salt evaporator: _ Narrow gauge railroad, srngle track . 2' .1.” Narrow gauge railroad, double or multiple Iracli Rice Pgddy; ”my, Power transmission line ......... / Spot elevation in meters: Checked; Unchecked * I46 x)“; "if”; .. Wall; Levee; Cliff , _ a g M R Woods; Scrub n oToner Waterwheel of mill; Located object Principal navigation light of lighthouse; Anchorage _ * xi; Tropical grass; Coconut grove APPROXIMATE IEAN DECLINATION l955 FOR CENTER OF SHEET ANNUAL MAGNETIC CHANGE l‘ EASTENLV Uaa diagram only to obtain numerical values. To deformine magnetic norfh fine, corned fho pit/of poinf "P" on the aouffi edge of the fringe wiffi If). valve of If). angle baht-on GRID NORTH and MAGNETIC NORTH, oa plotted on fhadegnaacofeofffhnorffiedya of "It Map, I. Read letters identifying 100,000 mater square In which the point lies: 2. Locate first VERTICAL up! line to LEFT of point and read LARGE figures labeling the line either in the top or bottom margin, or on the line itself: 71 Estimato tenths from grid line to paint: 3 3. Locate first HORIZONTAL grid line BELOW point and read LARGE figures labeling the line either in the left or right margin, or on the line itself: 12 Estimate tenths from grid line to point: 2 LP LP lGNORE the SMALLER figures of any grid number; those are for finding the full coordinates. Use ONLY the LARGER figures of the grid number; example: 806 000 SAMPLE REFERENCE: LP713122 lf reporting beyond 18' in any direction, prefix Grid Zone Designation, as: SSNLP713122 1958 UMAN NW, CAROLINE ISLANDS Military Geology of Truk Islands, Caroline Islands MAPS l6 THROUGH 22 VEGETATION 15 7°27’00” 823 293" 00' _ 820 319 816 22’30” 815000m.N_ 7°22’OO” 151' TRUK ISLANDS CAROLINE ISLANDS 125,000 1°32Ioor 339 32/30” 3[Ii] K3 a: 2" Military Geology of Truk Islands MAPIG Vegetation EXPLANATION UNIT DESCRIPTION c . “51‘ M’vF’riwa5- 21 short pilings. lacking. 27 foot troops fair to none; construction materials unavailable. good to fair; construction materials rare. I 23 I i 15 I I 30 I I II VESETATION MAP, TRUK ISLANDS I‘VE'TI‘I‘EEISIAII MANGROVE SWAMP Shallow salt and brackish swamps along the coast and in embayments; vegetation chiefly Rliiznplzora " mucrormla and Bruguiera conjugaiu, both having branching aerial prop roots which form tangled barriers impenetrable to foot troops and to many amphibious vehicles. Cierodendrum inerrnc, Excoocuria agaiiocha. [.umniizera [iiiurcu, Xylocarpus granaium, and Sonnemiia caseoiaris found mostly in the landward margin. Construction materials limited. STRAND VEGETATION Vegetation of coastal-lowland and reef-island sandy soils, consisting of Cocos nucifera (abundant), I - Pisonia grandis (reef islands), Artocarpus aitilis (mostly reef islands), Morimia cilrifoiia, Thespesia pupulnca, Hibiscus tiliuccus, Barringmniu asiatica, Pandanus iecton’us, Scueuola sericca, [{emandia sonom. I‘cmphis ucidula, Sporobolus Liinqinicus, Viynu I marina, lpomoea pas-caprao, and Remirea mariiima. Vertical concealment good to fair, horizontal concealment poor to fair for foot troops; crossAcountry movement of foot troops good; coconut logs suitable for cribbing, hasty fortifications, and ‘ I FRESH~WATER MARSH Muck and peat bog; vegetation chiefly Phragmites liar/ta; minor plants Hibiscus iiliacvus, Punt/anus teciorius, Cyperus sp., Scleria sp., Jussiaea suf/ruticosa, Meiroxy/on amicarum (ivory nut), and small cultivated patches of / FILL VEGETATION Vegetation composed of wide variety of plants, influenced by nature of both substratum and fill material; Phragmiius karka, young Cocos nucifera, Vignu marina, Fossil/om fuel/(Ia, Cassia occidentalz's, Scleriu sp., I’aspalum sp., ,/" Siacliyiarpheia indica, Hibiscus iiliaceus, Musu sp., and Morinu’a ciirifoliu found in varying combinations. Concealment for , COCONUT-BREADFRUIT FOREST Areas of mostly semiopen forests and semiclosed forests. 6 ‘ Cocos nucifera and Ariocarpus aiiilis, with scattered Mangifem indim and Hibiscus iiiiuceus: understory and grassland plants inCIude Derris eilipiica, Flageliariu indica, Passi/Iora faetidu, Sida rhombifalia, Elcusiric indica, Mismnihus floridulus, and Mcrrcmia peliata. Vertical concealment good to fair for foot troops in dense forests, fair to poor in included grassland 21 I ,»- patches; horizontal concealment fair to poor in forests, good to fair in grass patches. Breadfruit trees suitable for bridge i 25 25 timbers and construction lumber; coconut logs suitable for cribbing and short pilings. “FICUSPANDANUS” FOREST Primary natural forests in relatively inaccessible areas. mostly on summits and adjacent slopes, some found along rock escarpments at intermediate levels; composed of Ficus prolixa, Pandanus tociorius, Hibiscus til/(rams, scattered palms, Eleocurpus, and Flugellaria indica. Minor grassland inclusions composed of Miscanilius floriduius, Dimeria, Glcichenia, and Merremia pollute. Cross-country movement of foot troops difficult; concealment for foot troops {bowl 25 40 a.» we 31 21 g; 24 ,5 29 Cyriosperma chamissonis and Colacasia csculenia. Vertical concealment generally good for foot troops; construction materials . x» \" 27 1.22.“.4 Accsgofig .. ‘30 GRASSLAND Open and shrubby upland volcanic areas vegetated with Miscanihus floridulus (swordgrass), Ischaemum muiicum, . I 5 Puspalum ronjugatum, Siachyiarplzeia iridica, Pussi/Iora foeiidu, Sida rhombifoiia,Mcrremia pclim‘a, Chloris inflaiu, chelia I bifiora, Cassia occidimlalis, scattered patches of Hibiscus iiiiaceus, Lari/11ml camara, Scieria sp., and Macaranga curolincnsis, I scattered coconut, breadfruit, and mango trees, and a fern, Gleichenia. Horizontal concealment good to fair in swordgrass, I poor in Ischaemum; construction materials restricted to scattered coconut, breadfruit, and mango trees. 21 Vegetation consists primarily of I W i II . I ) , i 2 17 HI ,. I'I , LAMOSEU BAY I /3\ ‘0» [r s ‘i 7» II(3) II 18 (\‘4/ IX 2" /I 30 21 15 if ral f3? . 1 1 - In; yo \3; (m 7 OROR EN 5158i; fax/.1 IZISLANDS (5) I TRUST TERRITORX or; THE/PACIFIC ISLANDS I (U.S.A. ’ADIVIINISTRATING AUTHORITY) Cape Ole," e LEM’OLB YI‘ TRUK LAGOON 1 Nautical Mile HORIZONTAL DATUM IS HYDROGRAPHIC DATIJM. BLACK NUMBERED LINES INI" MLRCATOR f Hit List lHREEI cu II [ /44“45’ o°ii’ /’ on on I 84 MILS 3 MILS / AI'RRQXIMATL MEAN UFL'LINAIION i955 FOR CEVTER Oi SHEET ANNUAL MAGNETIC CHANGE II FASTERL‘I Use diagram only to obtain numerical values. To determine magnetic north iine, connect the plvol point ”P" on the south edge of the map will: the value of lhe angle between GRID NORTH and MAGNETiC NORTH, cu plotted on the degree scale at the north edge of the map. APPROVIUA i i" riir' . 1958 RIZONTAL '(‘ad LARGE MEWL‘AIOR PRC II Gil-71W t sen ori TIIIT ASI‘ROi-IOMIC srA‘r 15l°53’M 3” EAST or I:reFI{I‘~‘V\’:CH - Mo 72:03? 7” WWW fie Its/iii“ rim: Vegetation by James E. Paseur, 1954-1955. ’.”‘OVEP AGE LII-AG I'M NI 13} 17 ICorEIQ‘SC}? 54’ I 15 (co I I I I I I I I 51 I i 19 I I 11 I I I, ,, I 11 Coral reef 11 I! * .. Coral sip 22 19 17 12 Coral rests 2 13 I0 Smearali 151°39’30” .lirilvAY MAP SERVICE, FAR EAST - 5.7041 . R-IS . 12/58 - 3.4C INDEX TO ADJOINING SHEETS 4544 Ii NW MAP 20 4544 III SW 4544 III SE 4544 II SW MAP 16 MAP 18 MAP 21 4543 IV NW 4543 IV NE 4543 I NW MAP 17 MAP 19 MAP 22 GLOSSARY {in}: , , , ,, mountain, peak Nom en , .. , , . ,. , ,,,,. bay Oror en ,, , ,,, anchorage Unun en , , , , , cape. point IJDOT SW, CARDLINE iSti’iNDS 9? ,__. TRUK ISLANDS CAROLINE ISLANDS 125,000 151 °32’00” 7 “22’00” 339 32/30” 340 341 I 22 814 23 14 TOL NW 27 313 \ Coral reef’fi" 1 12 \2 .1 Coral motif? 2 CW 17 21 Coral "Coral reef 28 812 21 19 18 21 33 35 811 “ - 31 24 11 20’00‘” 23 810 \ 24 nun en Unikopi 23 [LICK HARBOR 12 Coral Coral 33 29 sand and shefis‘\\ 809 “ 25 23 17 coral ’R tax 11 coral \ i8 2,l cora 22 coral 25 23 808 a, 08 \ 19 19 , coral / f» 28 21 coral 29 19 11 coral ‘ -. coral II-I sand 807 23 27 sand 21 is. 0 WW}: Coral 19 C 25 oral 19 3I coral \ 35 TRUST TERRITORY or THE (U.S.A. ADMINISTRATING AUTHORITY) PACIFIC ISLANDS UNIT 9) 4 “(so 17'30” 806000m.N_ SOBU REEF .-.~ Coral reel @ Coral Coral .1"? «J 07 29 31 17 coral ‘\ 30 11 coral 7”17’00i" ” 151°32’00” 339 000m.E_ 32/30” PACIFIC 48 340 341 356 418 342 16 23 I I Military Geology of Truk Islands MAP 17 Vegetation 151°39’30” 7°22’OO” (’00 15 x ' 814 , 8’13 ‘ coral 812 8ll 20’00” MANGROVE SWAMP Shallow salt and brackish swamps along the coast and in embayments; vegetation chiefly Rhizophora mucronata and Bruguiera conjugata, both having branching aerial prop roots which form tangled barriers impenetrable to foot troops and to many amphibious vehicles. granatum. and Sonneratia caseolaris found mostly in the landward margin. STRAND VEGETATION Vegetation of coastal-lowland and reef-island sandy soils, consisting of Cocos nucifera (abundant), EXPLANATION DESCRIPTION 22 810 W 809 Clerodendrum inerme, Excoecaria agallocha, Lumnitzem Iittorea, Xylocarpus Construction materials limited. Pisonia grandis (reef islands), Arlocarpus altilis (mostly reef islands), Morinda citrifolia, Thespesia populnea, Hibiscus tiliaceus, Barringlonia asiatica, Pandanus tectorius, Scaeuola sericea, Hemandia Sonora, Pemphi‘s acidula, Sporobolus uirginicus, Vigna marina, Ipomoea pes-caprae, and Remirea maritima. Vertical concealment good to fair, horizontal concealment poor to fair for foot troops; cross-country movement of foot troops good; coconut logs suitable for cribbing, hasty fortifications, and —— short pilings. FRESH-WATER MARSH Muck and peat bog; vegetation chiefly Phragmites karka; minor plants Hibiscus tiliaceus, Pandanus fectori‘us, Cyperus sp., Scleria sp., Jussiaea suffruticosa, Melroxylon amicarum (ivory nut), and small cultivated patches of Cyrlosperma chamissonis and Colocasr'a esculenla. Vertical concealment generally good for foot troops; construction materials lacking. Stachytarpheta indica, Hibiscus tiliaceus, Musa sp., and Morimia citri/olia found in varying combinations. foot troops fair to none; construction materials unavailable. L'l r- ,Merremia r " ‘ poor in Ischaemum; construction materials restricted to scattered coconut, breadfruit, and mango trees. plants include Derris elliptica. COCONUT-BREADFRUIT FOREST Areas of mostly semiopen forests and semiclosed forests. Vegetation consists primarily of Cocos nucifera and Artocarpus alti’lis, with scattered Mangifera indica and Hibiscus liIiaceus; understory and grassland FIageIIaria indica, Passiflora foetida, Sida rhambifolia, EIeusine indica, Miscanihus floridulus, FILL VEGETATION Vegetation composed of wide variety of plants, influenced by nature of both substratum and fill material; Phragmites karlra, young Cocos nucifera, Vigna marina, Passiflora foeli’a'a, Cassia occidentalis, Scleria sp., Paspalum sp., Concealment for GRASSLAND Open and shrubby upland volcanic areas vegetated with Miscanthus floridulus (swordgrass), Ischaemum muticum, Paspalum conjugatum, Stachytarpheta indica, Passiflora ’ "" , Side 1‘ bifIam. Cassia occidentalis, scattered patches of Hibiscus tiliaceus, Lanlana camera, Scleria sp., and Macaranga carolinensis, scattered coconut, breadfruit, and mango trees, and a fern, Gleichenia. Chloris inflate, Wedelia Horizontal concealment good to fair in swordgrass, and Merremia peltata. Vertical concealment good to fair for foot troops in dense forests, fair to poor in included grassland patches; horizontal concealment fair to poor in forests, good to fair in grass patches. Breadfruit trees suitable for bridge timbers and construction lumber; coconut logs suitable for cribbing and short pilings. “FICUS‘PANDANUS” FOREST Primary natural forests in relatively inaccessible areas, mostly on summits and adjacent slopes, some found along rock escarpments at intermediate levels; composed of Ficus prolixa, Pandanus teclorius, Hibiscus tiliaceus, scattered palms , Eleocarpus, and Flagellaria indica. Dimeria, Gleicheni'a, and Merremia peltata. good to fair; construction materials rare. I Minor grassland inclusions composed of Miscanthus floridulus, Cross-country movement of foot troops difficult; concealment for foot troops 808 W 807 17’ 30” W 806 W856 5 Edition 2-AMS (AFFE) Prepared under the direction of the Engineer, Hq AFFE/BA, by the US. Army Map Service, Far East. Compiled in 1957 by photogrammetric (multiplex) methods. Coastal hydrography compiled from USHO Chart 6049, 1944. Horizontal and vertical control established by Corps of Engineers, 1951. Names transliterated in accordance with rules of the US. Board on Geographic Names. Maior roads are classified by reconnaissance by the 64th Engineer Battalion(BaseToDOSraDhic), 1952; other roads are classified from source maps and aerial photography and are not verified by reconnaissance, Coastal vegetation are classified by reconnaissance by Military Geology Branch, Intelligence Division, Office of the Engineer, Ho AFFE/8A, with personnel of the US. Geological Survey, 1955. Map not field checked. Vegetation data based on field investigations 1954-1955 by Military Geology Branch, Intelligence Division, Office of the Engineer, Hq, U.S. Army Japan with personnel of the us. Geological Su rvey. LEGEND ROADS All weather hard surface, two or more lanes wide None Builtup area . W W W . . None loose or light surface, two or more lanes wide WW W None Church; School; Cemetery W .. WW, WWW J. I 11:91“; hard surlace, one lane wide W WW None Limit of danger line; Submerged reel W loose or light surface. one lane wide None Wreck; sunken, Exposed W WWWWW fair or dry weather, loose surlace, two or more lane: wide ::::-:: Sunken rocks; foreshore Ilats W, W _ Fair or dry weather, loose surlace, one lane wrde W, , :WW : :: : Rocks bare or awash; Reel W ,0 _ Cart track; trail WW , W WWWWWW WWW _____W_ Depth Curves and Soundings lI1 Fathoms W. , W . Standard gauge railroad, single track WWWW WWW —+--+—t— Reservoir; Dam; Ditch ”AAA“ w Standard gauge railroad. double track was-ism Narrow gauge railroad, Single track _WWW WWWW 2"” Salt evaporators ”NET WATA»¥‘_“_7*M 2’s” 1. Narrow gauge railroad, double or multiple track W Rice Paddy; Marsh ##W “mimii WWkW Power transmission line W W A WWWWWWW WWW WW__ / I [—7- Spot elevation in meters, Checked; Unchecked W ms e,“ "we; .. ° ' ‘ Wail: Levee; Cim W , __ Warns Woods; Scrub "77777777 M 1:11: Waterwheel ol mill; Located ODIECI W W ,W , WW W 0 OTower Principal navigation light 01 lighthouse; Anchorage W * 3/ Tropical grass; Coconut grove WWWWWWW, WWW 1:1: GN 4’45’ on 54 uiLs o'ii’ on 3 uiLs APPROXIMATE MEAN DECLlNATION less FOR CENTER OF SHEET ANNUAL MAGNETIC CHANGE 1' EASTERLV Use diagram only to obtain numriml values, To determine magnetic nortti lino, connect tho pivot point “P" on the south edge otttu map with the value of the angIe bone-on GRID NORTH and MAGNETIC NORTH, as plotted on the dogma scale at the north edge at the map, Scale 1:25.000 346 p 347 1 l E 0 1 Statute Mile 1000 500 O 1000 2000 Meters L iW—i l-—1 H I——-I i-———i i>—————-——-———-—-—‘i 1000 500 0 1000 2000 Yards I 1—{ i—T r—T T—{ H . r 1 0 CONTOUR INTERVAL IO METERS VERTICAL DATUM: MEAN SEA LEVEL HYDROGRAPHIC DATUM: APPROXIMATE LEVEL OF LOWEST LOW WATER TRANSVERSE MERCATOR PROJECTION HORIZONTAL DATUM IS BASED ON THE ASTRONOMIC STATION Not 2 (1951 )' 151'53’34.3' EAST OF GREENWICH. 7'21’37,7' NORTH BLACK NUMBERED LINES INDICATE THE 1,000 METER UNIVERSAL TRANSVERSE MERCATOR GRID, ZONE 56. INTERNATIONAL SPHEROID THE LAST THREE DIGITS OF THE GRID NUMBERS ARE OMITTED GRID IONE DESIGNATION: TO GIVE A STANDARD REFERENCE ON THIS SHEET TO NEAREST 100 METERS 100,000 M, SQUARE IDENTIFICATION SAMPLE POINT: TRAIL JUNCTION N 1 Locate tirsl VERTIC LP line either in the to on the line itself: to paint and read LAR IGNORE the SMALLER figures of any and number; these are for llndltll the full coordinates. Use ONLY the LARGER figures of the grid number; example: on the line itself: 1. Read letters identifying 100,000 meter square in which the point lies: AL grid line to LEFT of point and read LARGE figures labeling the p or bottom margin, or Estimate tenths from (rid line to paint: 1 Locate first HORIZONTAL and line BELOW GE figures labeling the line either III the left or right margin, or Estimate tenths tron-i grid II"! to point: LP 48 11 1 SAMPLE REFERENCE: LP489111 , II reporting beyond 8-0—6 000 prelix Grid Zone Designation, as: 18" in any direction. 56NLP489111 1958 1 Nautical Mile 348 37/30” 349 Vegetation by James E. Paseur, 1954-1955. COVERAGE DIAGRAM \\ ‘2‘ \\. COMPILATION METHODS Photo-planimetric Photo-stereo W A. USHO Chart 6049, 1944 (reliability good). Aerial photography; 1-Feb., July 1946; 2-Feb. 1947. \\ \ WS“ / 350 I 351 7°17'00” 151°39’30” U.S. ARMY MAP SERVICE, FAR EAST ~ 57-041 - R 15 - 12/58 - 3,40 INDEX TO ADJOINING SHEETS ‘\\\\\§\\‘\\\\\\V 4 i NW \\ \‘\\ l W 4 l \\\\\\ no: This 4543 IV NW 4543 IV NE 4543 l NW MAP 17 MAP 19 MAP 22 T_I Map Berg GLOSSARY mountain peak 3:2": :i “.4013: Unun en cane, point TOL NW, CAROLINE ISLANDS TRUK ISLANDS CAROLINE ISLANDS 125,000 151 33/30“ 352 7‘27/00II‘ 40/00! 353 355 356 357 I U ID D T 358 42’30' S E 2° 3° 4° 5° 6° 7° L111 I I ILLLII III 360 363 362 45100! 364 Military Geology of Truk MAP 18 Vegetation Islands 365 151'47’00” 823 , , 822 821 25’00’ 820 ,s, ,, 2ft“: coffiifl, 31 28 —~ ‘Cnral 24 .s_-_-‘_ ,« 1:; 29 coral 30 coral 23 I I 29 21 coral 28 29 30 dz 24 I (U.S.A. ADMINISTRATINGI AUTHORITY) I 12 Uncovers 2 feet TRUST TERRITORY OF THE IPACIFIC ISLANDS 29 coral I 24 coral 18 17 ” 2i 22 coral \ kn Ioh'"Népdr' " ‘ I 21 II I I I VEGETATION MAP, 34 coral TRUK ISLANDS EXPLANATION DES MANGROVE SWAMP Shallow salt and brackish swamps along the coast and in embayments; vegetation chiefly Rhizophora mucronala and Bruguiera conjugate, both having branching aerial prop roots which form tangled barriers impenetrable to foot troops and to many amphibious vehicles. granaium, and Sonnemtia caseolaris found mostly in the I STRAND VEGETATION Vegetation of coastal-lowland and reef-island sandy soils, consisting of Cocos nucifera (abundant), Pisonia grandis (reef islands), Artocarpus aIrI'Iis (mostly reef islands), Morinda citrifolia, T hespesia papulnea, Hibiscus liliaceus, Harringtonia asiaiica, Pandanus feciorius, Scueuola sericea, Hemandia sonora, Pemphi's acidula. Sporobolus uirginicus, marina, Ipomoea pes-caprae, and Remirea maritima. short pilings. FRESH-WATER MARSH Muck and peat bog; vegetation chiefly Phragmiles karka; minor plants Hibiscus tiliaceus, Pandanus tecforius, Cyperus sp., Scleria sp., Jussiaea suffrulicosa, Metroxylon amicarum (ivory nut), and small cultivated patches of Vertical concealment generally good for foot troops; construction materials Cyrtosperma chamissom‘s and Colocasia esculenta. lacking. FILL VEGETATION Vegetation composed of wide variety of plants, influenced by nature of both substratum and fill material; Phragmites karka, young Cocos nucifera, Vigna marina, Passiflora foefida, Cassia occidentolis, Scleria sp., Paspalum sp., Stachytamhela indica, Hibiscus filiaceus, Musa sp., and Morinda citrifolia found in varying combinations. CRIPTION Clerodendrum inerme, Excoecoria agallocha, Lumm’lzera littorea, Xylocarpus Construction materials limited. andward margin. Vertical concealment good to fair, horizontal concealment poor to fair for foot troops; cross-country movement of foot troops good; coconut logs suitable for cribbing, hasty fortifications, and foot troops fair to none; construction materials unavailable. GRASSLAND Open and shrubby upland volcanic areas vegetated with Miscanthus floridulus (swordgrass), Ischaemum mulicum, Paspalum conjugalum, Stachylarphefa indica, Passiflara foetida, Sida rhombilolia, Merremia peItata, Chloris inflate, Wedelia bi/(ora, Cassia occidentalis, scattered patches of Hibiscus filiaceus, Lantana camera, Scleria sp., and Macaranga carolirrensis, scattered coconut, breadfruit, and mango trees, and a fern, COCONUT-BREADFRUIT FOREST Areas of mostly semlopen forests and semiclosed forests. Cocos nucifera and Artocarpus alfiIis, with scattered Mangifera indica and Hibiscus riliaceus; understory and grassland Flagellaria indica, Passiflora foetida, Sida rhombifolia, Eleusine indica, Misconfhus floridulus, Vertical concealment good to fair for foot troops in dense forests, fair to poor in included grassland patches; horizontal concealment fair to poor in forests, good to fair in grass patches. Breadfruit trees suitable for bridge plants include Derris elliptica , and Merremia peltata. timbers and construction lumber; coconut logs suitable for "FICUS-PANDANUS” FOREST Primary natural forests in relatively inaccessible areas, mostly on summits and adjacent slopes, some found along rock escarpments at intermediate levels; composed of Ficus prolixa, Pandanus tectorius, Hibiscus tiliaceus, Minor grassland inclusions composed of Miscanthus lloridulus, Cross-country movement of foot troops difficult; concealment for foot troops scattered palms, Eleocarpus, and Flagellaria indica. Dimeria, GIeichenia, and Merremr’a peltata. good to fair; construction materials rare. Gleichenia. cribbing and short pilings. Horizontal concealment good to fair in swordgrass, poor in Ischaemum; construction materials restricted to scattered coconut, breadfruit, and mango trees. Vegetation consists primarily of 7‘27'00’ 823 822 Vigna 821 Concealment for 820 25’00’ 319 1 til/I 17 I :53! 22 18 I {j I 1 I I 0V / 2L , I I , I I ”I 5 aaaa I .53.. I 15 22 ASA] I 3 1 ‘ x’ I I I 17 I /, ’ I I“ I I , ” ’ a \ 8 818 W _. ”18% s (by, 20 18 I 16 ‘// 18 I \\ / /’ 49 [I’I17 I II :I ‘\__—x|——-J ” x/ I I E \\ 15 .34.. // I I I \ 12 sand 3 / I I I \\ ( 21 4‘ 2/; I I I :15 12 ,\ \I\ I 61 [I] I 11”.“ I sand Iand shells sand and 5M": \\ I\\ 17 I 02 1a ‘ 1e ‘ f 5 I ‘I I I II I 18 /, sand . 1‘ 5073 I E I \\ \\ . I \ I I’ x a I I I II \‘T’ I I 3 \\ \I I I I I I I 1; \ III 15 I II I I ‘ I I 12 \ ‘I ”'3' 18 817 I‘ I _____ > i ‘ V. 817 "If ,E, , ' Tc 4;" “‘ "’I’ ' "' I 7 T' I 12 j i I 15 \‘I :I 22 I as. I I I I I I I I ‘ I \ ‘ I I I I l \ ‘I I I I ‘ I I I I I I I : : i I I I I: I 3 19 ‘I\ \ I I 53 54 55 17 I 56 I: 16 I 63 .\ 54 65 21 I 18 ‘ 19 ‘ 1 : 1 coral II I\ \\ 16 13 I I. I_1 indicates swept depth area in feet 1 I 11 I $3.. I' ‘1 II, ‘ , I 1 I \ I I, I I I I 8 II III II‘ I I1 I I I I I I II __ \\ II, I \I\ I I I I ICoral I «’X’ \\s\ ‘1 I II I I 13 I I116 II 10 [/93 \l\\ ‘ $16 815 I I, - l6-- , , I coral’T’I ~ 2-, W W W ~ ~~~ H4 W ' q-I , .I LIo/l I, I . I : I s I \ is \ I 18 \ I . “~—' \ \ I \\ I I DOT ROAD I' 13 ‘I \ I \ ‘ I I (anchorage) 13 Is“ -s ‘ \\\ I 18 \\ 22 I i coral m‘fl“‘— _ ‘xlfi \\"\\ 13 I I,\ I 13 I (,3: ,\ sana_\\\\ I\ \\ .55, I \ I “‘~\ \ \ / ‘I 17 \\ I ”K. sand I: 12 12 corn '0\ \“33 \\ , / I 29 H / 23 \I 15 I coral 17 , \S'\ , /,/ I0‘ 2230! —,‘ 0‘ ‘I\ I 4 , coral 3—; I l /\\ \ 15 I], 7 _ 22/30y / J \\ \ /I ‘ : 42 ’ll’G \\ _______ .I —————————— Coral I \ ‘—» I I ‘ / ———————————————— I I I I. . ..... n I 21 I 17 I 10 IX III I \\ I i CLPnI \ \16 815 815°00m-N. 7;. 1517 , , , , , , + I- , 7- I ~ , ~ . W ‘ o 12 I I I I 13 "R I‘é‘x 11 . t I I \ \ v I I \\ I I O 3 13 \\'5\ O/\/ I 3 \, I :1 I 17 I7 11 III 15 12 ‘ 7 I 4 o I x f fig“ reel1:\ + 61 ‘ 21 6} o I 13 18 I coral 15 0\ I I. 8 Corn 5‘ 2 2 ‘ ‘ \ I I 13 /' ’\ I I 12 7.22.00, misc“ tsICOIaI I ‘ I I3 I l W's 1 k/ 8 ‘6 I ' I mom" 7°22Ioo” 1510391301 352°00m‘E. 40/00'353 354 355 356 357 42/30” 358 359 360 p 352 45/00II 353 354 365 151'47/00" 361 W356s Scale 1:25,ooo Edltlon 2-AMS (AFFE) 1 t o IStatute Mile Vegetation by James E. Paseur, 1954-1955. U.S. ARMY MAP SERVICE, FAR EAST - 57-041 - R-15 - 12/58 - 3. 4c Prepared under the direction of the Engineer, Hq AFFE/SA, by the U.S. Army Map Service, Far 109° 5% J 100° 2°00 Mews East. Compiled In 1957 by photogrammetric (multiplex) methods. Coastal hydrography compiled 1000 500 O 1000 2000 Yards from USHO Chart 6049, 1944. Horizontal and vertical control established by Corps of Engineers, 1 H 1—1 a H 1—1 a 1951. Names transliterated in accordance with rules of the U.S. Board on Geographic Names. O IN t' IM'l Major roads are classified by reconnaissance by the 64th Engineer Battalion(BaseTorJOsraphic), 1 a , a“ I“ re 1952; other roads are classified from source maps and aerial photography and are not verified COVERAGE DIAGRAM INDEX TO ADJOINING SHEETS by reconnaissance. Coastal vegetation are classified by reconnaissance by Military Geology Branch, Intelligence Division, Office of the Engineer. Hq AFFE/BA, with personnel of the U.S. CONTOUR INTERVAL TO METERS WITH SUPPLEMENTARY CONTOURS AT 5 METER INTERVALS Geological Survey, 1955. Map not field checked. VERTICAL DATurA: "EA" 5“ LEVEL 4544 II NW Vegetation data based on field investigations 1954-1955 by Military Geology Branch, Intelligence TRANSVERSE MERCATOR PROJECTION V MAP 20 Division, Office of the Engineer, Hq. U.S. Army Japan with personnel of the U. 8. Geological HORIZONTAL DATUM IS aAsEu on THE ASTRONONIC STATION NO. 2 (I95! ): m \\\\ survey. 151°53’34.3' EAST OF GREENWICH. 7'2l’37,7' NORTH E \h‘i\\‘\;\~‘,“\‘\\§\\\§ 4544 III SW 4544 III SE 4544 II SW : &\‘\t\:‘o‘§§‘\\‘\ » .\ \V w LEGEND HYDROGRAPHIC DATUII : APPROXIMATE LEVEL OF LOWEST Low WATER :\\\\\\{§$§\\:§§\g§§§\\ MAP 16 MAP 18 MAP 21 ._\ .z:. .. .\\ : ~ .-. ,t-“Q ‘ "\V V, V ROADS BLACK NUMBERED LINES INDICATE THE 1.000 METER UNIVERSAL TRANSVERSE \ \\&;§§§§i§®v§§1 ‘\\\ II“ mm" IERCATOR GRID. zone 56. INTERNATIONAL SPHEROID $\~§‘\\\§s§\t\\ @gg‘ \ 4543 w NW 4543 N NE 4543 I NW 1 we." ...\\,“\. :1\ hard- surlace, two or more lanes wide None Built-up area 6" THE LAST "I“: “GI" or "I: "In “onus A“ mun" \ “w“ \\ MAP 17 MAP 19 MAP 22. loose or light surface, two or more lanes wide None Church, School, Cemetery ____—w x \\\\‘\\\\\\\\“\\\\\i\ hard surface, one lane wide None Limit of danger line; Submerged reef -, -' 4'45’ COMPILATION METHODS loose or light surface, one lane wide None Wreck: Sunken; Exposed °_I°, on Photo-stereo Photo-planimotrlc Map Fair or dry weather, loose surface, two or more lanes wide — Sunken rocks; foreshore flats on u “L5 GRID ZONESDGETVIGMTIO": fSigIziEIE‘ETsT3":EA:I?E:‘:II$E:ETE%: W I. :1 GLOSSARY Fair or dry weather, loose surface, one lane wide 212:3: Rocks bare or awasll; Reel 3 ms mono nsoum Iommcmou SAMPLE romr: ; SCHOOL ,1 usuo ohm 5049 1944 (reliability good). 3:31:16; :"cmmF‘t . . .. ,. , ' . c pa, pom Cart track, "all ._._____ Depth Curves and In fathoms LR.“ mm, mums" 100,000 mm, LP Aerial photography: Feb., July 1946 - 4 ‘ ~ square in which tho point lies: Standard zauxe IaIlwad. smile tuck W -+—l-—f— Mm"; Darn; WI, 2. Locate rim VERTICAL ma line to ten of Standard gauge Humid, double track point and road LARGE figures Iahelmgtho ' 3 LP a .n a“ "ammo” line either in the top or bottom margin, or Narrow gauge railroad, single track —-—:Tr— 11 ,_ M APPROXIMATE nun ozcururiou 1955 on the line its-ll: 589 . . a u .. row cznrsn or SHEET Estimate tenths from gridlinelo point: "W0" 83““ “I'm“. “WW 0' "'“I‘IPIe I'm “""'“_"— Rice Paddy; Marsh _—_ 4‘!- a ANNUAL MAGNETIC cums: 1' EASTERLV 3. Locate first HORIZONTAL arialine BELOW , , _ ,’ ., point and road LARGE figures labeling the Power transmissron line _ _________ / f u. diogmm only to obtain numerical values. lino either in the loft or right margin, or 16 « - I , ,, ,, Nipa; “ a o . . - lGNORE tho SMALLER figures of any on the I'm mg"; 590' ”Wino" "I MEWS. CAN-1‘96. Unchecked “5 I“ To defer-rum: "rm M Iron, W "I. lfid "Mb"; "'80 I" '0' "Mill! Estirnltzlonths from grid line to point: 4 Wall; Levee; Cliff *Wafig DD PM” P°""' PI °" "h “‘I' “9'? °’ "" ""P the full coordinates. Use ONLY the . ~ I Woods; Scrub with his value or the angle banana GRID LARGER lilum of mo grid numb-r: 5mm REFERENCE: LP589164 Wltemheel of null; Located obiecl ‘3‘ o °"°' DD Nom and mosaic Noam, a. ploflod on "“9": 815000 u reporting beyond 13' in my direction, Principal navigation light of lighthouse; Anchorage _ * 3/ Tropical grass; Coconut grove _ "in dogma scale or the north edge of "'0 m _ prof-x GM 1°". Dwmtmn' “I SGNLP58916‘ 1958 UDOT SE, CAROLINE ISLANDS Military Geology of Truk Islands MAP 19 Vegetation TRUK ISLANDS VH‘ () 7 .\ 4 \\ o o CAROLINE ISLANDS 1225,000 L E 1 11: 0; 2° 3° 4 5 6° 7° 3 3 0 I I 151 3913011352 4000* 353 354 355 355 357 42’30” 358 359 360 61 62 45,00, 151 47 g'ozzioo' 7'22'00' ’ I 7 7 21 K 0/ I ‘ 7 12 Coral <\ colrlal 17 coral 2 l C y 11 T \ 10 , °\ 3 12 11 \I 16 I Cofnl \\\/ 16 9 11 11 6 14 .. . - 814 14 \3. (3; 14 c a 63 \7/011 8 2 o, 0‘ 75> Yam "\ .5 6 ‘\—5- 17 11 cozral 15 v \’° —~ ————————————————— l7’ 3 F s“, ,,,,,,,,,,,,,,,, COTE 7 / 16 1 ”o, 10 \o 2 2 V 2 \ 6 I 3/ 16 3 3 2 /' [l 2 5 Qty) 13 L 8 3 10 17 5 \_ ,IO 1 1 ’0 \ \ 12 16 51 1 999 L 3 c1131 12 21 0/ 2 1) JAB 813 14 11 1 3 car 23 \ 4 3 10 13 \ coral A I I“ < /\o g 20 \17 21 ® 44 14 .- 13 \ coral ,5 \ 19 3 61 J \\ coral 17 2 \\ G) 20 4 cgrlal \ 22 \\ 17 7 58 toga! 59 60 3 6 1 Bl \\ IO 7 \ \ 22 19 Ho \\ coral \ '5 \ 2 13 24 92,33, \ / 4 21 \ 3 coral 2 I coral 812 \ C013 I — 12 812 *7 A) [I 8 \\ l 1 l \ *9 ’o/ I S L A N D S 6 £93. ,— 1 [/1 \\ 19 D ’/ ‘1 1.1 indicates swept depth area in feet 17 \ ASL \ 15 7 \\ 19 23 . ' . ‘2] \ coral cor‘al 14 .. [’1 . \\ /“ . . 1 11 _. , -,Coral : coral \ 19 24 (2‘ - W ‘\ / \ “”3‘ 3- 5,: en. 57.) ofon \\_// 1 I \‘\ __ _ 1 1 mral ‘ ' 811 811 23 \\ 3 cgral / 3 28 21 5 212 16 9—~‘”‘/ 20/00” \ __ 1 _. 20,00” — \ 5‘ \‘I ,,,, "”1 ‘x, ‘ 17 z 8 3'9 \ ,a—J/ \ 5 \ ’’’’’ ' 21 \ 15 f. —- \\ 3 /” (E. || 1;; \\ 3 1 / \ \ - g / In 61 \| \\ 2;? // s8 ;\37 Q», ,-// E 13.1 \\ S4 21 19 l [I \\ / 0,. e—— _____ ‘ \ \\ ,0 \\fl/ 1 i ,1“ A - : T R U K L A G 0 0 N 2. 3 {-1.1 18 ', ‘\ 23 coral 20 22 —* ,/ ll \\ 1 “21;! coral car 2; ////”/~\\ 'I \\ 2 ., 18 coral l/l’ ‘, 21 l \ 5 2 29 . /, 1 s 1 ' 23 \ 3 \ \ i 810 I t '5 r 810 , 10 I . IO 10 _ 0.x i\ .\ 30 13 K ) 4 \ | \ \ , coral , /"1 Ir /, — L \ 22 '1' \\ \\ \ / \ / All ”GD 23 l * 22 W TERR'TW OF THE PAC'F'C ”LANDS VEGETATION MAP TRUK ISLANDS ‘1 5‘ [I \ 18 (U.S.A. ADMINISTRATING AUTHORITY) , ‘\—,/\ I \\ X g, . II \\ .® Coral 18 i 7 ‘\ 19 I] l \\ L5) 27 ,1 \ EXPLANATION 25 ll 18 \ 19 ,L I \\ ‘ I r 1 , \ ‘ 8 . , . (13., , \ 1 DESCRIPTION 09 809 . ’ . 209 I t 09 24 \_/’ 1' \\ 19 \\ MANGROVE SWAMP Shallow salt and brackish swamps along the coast and in embayments; vegetation chiefly Rhizophora 11' \ ‘i‘ 18 mucronata and Bruguiera conjugate, both having branching aerial prop roots which form tangled barriers impenetrable to 2 /-/" 23 \ \\ L4 Indicates swept depth area "1 feet foot troops and to many amphibious vehicles. Clerodendrum inerme, Excoecaria agallocha, Lumnilzera littorea, Xylocarpus p _____________ \ f 24 / \\ 19 ‘ 2‘ granatum, and Sonneralia caseolaris found mostly in the landward margin. Construction materials limited. / \ / \ / A3 21 [I \\ L STRAND VEGETATION Vegetation of coastal-lowland and reef-island sandy soils, consisting of Cocos nucifera (abundant), I L 1/ \\ 1 Pisom'a grandis (reef islands), Artocarpus altiiis (mosti y reef islands), Mw'inda cilrifolia, Thespesia populnea, Hibiscus Iiliaceus, " “““““““““““““““““““““ / \\ 21 /’,1_\\ 21 Barringtonia asiaiica, Pandanus teclorius, Scaevola sericea, Hemandia sonom, Pemphis acidula, Sporoboius uirginicus, Vigna —» 29 ‘ ‘~\\ ,I .21 \ £32. ,I’ X\ marina, Ipomoea pes-caprae, and Remirea maritima. Vertical concealment good to fair, horizontal concealment poor to fair \\\ |——l ‘~4 \ l ‘ 23 19 \\ K 0k 2%,, \\ for foot troops; cross-country movement of foot troops good; coconut logs suitable for cribbing, hasty fortifications, and 1 ________________________________________________________________________ t \\ ‘\ ,' short pilings. /' 808 ,,,,,,,, 21 ‘\ \ x \ 1 N I 808 ,_ _--— —’ 08 \ \ 3 19 2, 29 ,« 5 23 ‘\\2\ LA“- _...._ FRESH-WATER MARSH Muck and peat bog; vegetation chiefly Phragmiles karka; minor plants Hibiscus tiliaceus, Pandanus .x \\ " s . . 1 . coral \\\\ 33 .II.__3_:‘L“~ teclorrus, Cyperus sp., Sclen‘a sp., Jussiaea suffrutrcosa. Melroxylon amIcarum (Ivory nut), and small cultivated patches of \ L_4 .JA... __ r 21 \\ Cyrtasperma chamissonis and Colocasia escuienla. Vertical concealment generally good for foot troops; construction materials 21 \\ lacking. 52 53 54 19 55 23\\ 56 57 58 61 FILL VEGETATION Vegetation composed of wide variety of plants, influenced by nature of both substratum and fill material; 17 53:11 21 \ 22 17 Phragmites karka, young Cocos nucifera, Vigna marina, Passiflora foelida, Cassia occidentalis, Scleria sp., Paspalum sp., \ \ Siachytamheta indica, Hibiscus liliaceus, Musa sp., and Morinda citrifolia found in varying combinations. Concealment for 1‘ \\ foot troops fair to none; construction materials unavailable. 5 \\ \\ 1134 O7 19 \\ GRASSLAND Open and shrubby upland volcanic areas vegetated with Miscanthus floridulus (swordgrass), Ischaemum muticum, — 307 807 \\ \‘s 5 Paspalum conjugatum, Stachytarpheta indica, Passifiora foelida, Side rhombifolia,Merremia peltata, Chloris inflate, Wedelia island) 19\ 17 \x\ 20 biflora, Cassia occidentalis, scattered patches of Hibiscus tiiiaceus, Lanlrma camera, Scleria sp., and Macaranga carolinensis. 21 16 19 \‘\~\ scattered coconut, breadfruit, and mango trees, and a fern, Gleichenia. Horizontal concealment good to fair in swordgrass, 10 i \‘x poor in Ischaemum; construction materials restricted to scattered coconut, breadfruit, and mango trees. Io 21 1 13 coral ; . . . . . . L—J indicates swept depth area in feet COCONUT-BREADFRUIT FOREST Areas of mostly semropen forests and sem1closedforests'.‘ Vegetation conSIsts prImarIly of 7 Cocos nucifera and Arlocarpus altilis, wrth scattered Martyr/era Indian and Hibiscus tziraceus; understory and grassland 23 ‘ Io plants include Derris eiliptr‘ca y Flageliaria indica, Passiflora foeiida, Sida rhombifolia, Eleusirre indica, Miscanthus floriu'uius, 24 62°", 18 i and Merremia peitaia. Vertical concealment good to fair for foot troops in dense forests, fair to poor in included grassland 17'30” — + 1 patches; horizontal concealment fair to poor in forests, good to fair in grass patches. Breadfruit trees suitable for bridge M 17’30” 6 i timbers and construction lumber; coconut logs suitable for cribbing and short pilings. 8 806000m.N 25 06 \ 2 06 29 7 . . . . . . 06 ' 21 \ 1 < “FlCUS-PANDANUS" FOREST Primary natural forests In relatively InaccesSIbIe areas, mostly on summIts and adlacent slopes, sand 29 \\ Pl some found along rock escarpments at intermediate levels; composed of Ficus pralixa, Pandanus iectorius, Hibiscus tiliaceus, \\ 1.3.3. 23 scattered palms, Eleocarpus, and Flagellaria indica. Minor grassland inclusions composed of Miscanthus floridulus, 29 ‘ \ Dimeria, Gleichenia, and Merremr'a peltata. Cross-country movement of foot troops difficult; concealment for foot troops 13 ‘x\ good to fair; construction materials rare. 23 4 j 22 \\ 29 \\\ , $13.1 cm“ 15 ‘/5 25 \s\ 23 1 1 24 , - 28 23 3 \“~‘\ ' l 30 coral 27 7'17Ioor I Xéfi ‘5 a 0‘ 17 K \ 2‘ “~ 1 l 7'17'00'I 151‘39/30’I 352000m.E. 40/00” 353 354 355 356 357 42’30' 358 359 360 362 45'00” 363 364 365 151 47'00' W856 8 Scale 125,000 . . 1 . . ‘ElelOn 2—AMS (AFFE) 1 E 0 IStatute Mlle Vegetation by James E, Paseur, 1954.1955. U.S. ARMY MAP SERVICE, FAR EAST ~ 57-041 . R15 - 12158 - 3.4C Prepared under the direction of the Engineer, Hq AFFE/8A, by the U.S. Army Map Service, Far 1080 500 , 1 0, 10100 ZOJOO Mae's East. Compiled in 1957 by photogrammetric (multiplex) methods and from 1:55,180, USHO 1000 500 0 1000 2000 Yards Chart 6049, 1944. Coastal hydrography compiled from USHO Chart 6049, 1944. Horizontal and l H H 1.....1 1-—-—1 1..., , vertical control established by Corps of Engineers. 1951. Names transliterated in accordance 1 0 1Nautical Mile with rules of the U.S. Board on Geographic Names. Coastal vegetation are CIaSSified by reconnais- . , . . . 1 . . . . . sance by Military Geology Branch, Intelligence Division, Office of the Engineer,Hq AFFE/8A,with personnel VERAGE DIAGRAM INDEX TO ADJOINING SHEETS ~ - CO ' 0f the UAS~ GQO'OS'C‘“ Sum”. 1955- Map "0t “9'“ Cheeked- CONTOUR INTERVAL 10 METERS WITH SUPPLEMENTARY CONTOURS AT 5 METER INTERVALS VERTICAL DATUM~ MEAN SEA LEVEL Vegetation data based on field investigations 1954-1955 by Military Geology Branch, Intelligence Division, Office of the Engineer, Hq, U.S. Army Japan with personnel of the U. S. Geological TRANSVERSE MERCATOR PROJECTION 4544 ” NW Survey. HORIZONTAL DATUM IS BASED ON THE ASTRONOMIC STATION NO. 2 (1951 )2 MAP 20 151'53’34.3' EAST or GREENWICH, 7‘21’37.7' NORTH LEGEND HYDROGRAPHIC DATUII : APPROXIMATE LEVEL or LOWEST Low WATER 4544 111 SW 4544 111 SE 4544 11 SW ROADS BLACK NUMBERED LINES INDICATE THE 1.000 METER UNIVERSAL TRANSVERSE MAP ‘6 MAP ‘8 MAP 21 All "other IERCATOR GRID. ZONE 56. INTERNATIONAL SPHEROID _ THE LAST was: DIGlT‘S or m: can: NUMBERS ARE ouIrrEo hard surface, two or more lanes wide None BOIli-UD area N0"? , G" 4543 IV NW 4543 N NE 4543 1 NW loose or lIght surface, two or more lanes wide None Church; School: CEMENT! ‘ I {09111; MAP 17 MAP 19 MAP 22 hard surface one lane wide None LIITI11 ol danger line; Submerged reel , , f ‘ ' 3“ 4‘45’ loose or light surface, one lane wide None Wreck. Sunken, Exposed J“ , Mud 0,10, on an”; um: ogsmmnow m cw: A “AND“ E COMPILATION METHODS Fair or dry weather, loose surlace, two or more lanes wide w-mw» ~ Sunken rocks; Foreshore tlats t ' Sind on 3. 1111.5 ' nus SHEET m NtArfngzgzagcgg Photo-stereo Map Fair or dry weather, loose suriace, one lane wide 2: . :~_ cc: Rocks bare or awash; Reel * * 3 ’“LS 100,000 M. SQUARE IDENTIFICATION SAMPLE POINT: x 112 W [:1 GLOSSARY . . A .. r m _ .. Oror en anchorage cm "a“ "3" ———-~- ”91"" CW“ 3"“ "l ‘ °"“ 1. Tina letters identifying 100,000 meter A. 1:55,180, USHO Chart 6049. 1944 (reliabIlIty good). . d d ' d . l ‘ k squarem which the point lies: LP . . Unun en cape, 90"" Stan u gauge mma ' tinge ”c Reservoir; Dam; 011611 2. Locate firstVERTICAL 3nd line to LEFT of AerIal photography. 1"” 1946' Standard gauge mm)“v double track _”_...__4._ LP point and read LARGE liaures llbelmg the 2’0” Salt evaporators line Emil! in the top or bottom margin, or Narrow gauge railroad, single track APPROXIMATE MEAN DECLINATION 1955 onrhehnaitsell: 53 > a’a” FOR CENTER OF SHEET Estimate tenths from [rid line to point: 5 Narrow gauge ranlroad, double or multiple tract 11.“ pagdy; Marsh ANNUAL uAcNEtIc CHANGE 1’ EAernLv 3. Localehrst HORIZONTAL and lme BELOW , / , point Ind rend LARGE figures labeling the Power transrmssuon line A. _. ...... ’ , Us. diagram only To obfain numerical rakes. 1m mom .n rho left or "gm margin, or . . _ X ,, Nina; Man rave - - - - - IGNORE the SMALLER figures or any 111 I 1911; 13 Spot elevation In meters. Checked, Unchecked us 0.6 g r? “"7”": Tom" "W I'm’ 'm "'e um number; than u. Ior Imam: zgtimealontzhths from 1nd lmetn point: 4 Wall' Levee C1111 _..—m% [31: PH". pom! P on ”Q Inn “9‘ of”. map the lull communes. Use ONLV the . . a TA Woods; Scrub um. 10.9 var... or me angle barman GRID LARGER Iinuvesol m znd number; SAMPLE REFERENCE: LP535134 0 over NORTH and MAGNETIC NORTH, as plotted on anmplc: 806 000 If reporting beyond 18°1n any directlon, 1:3 D the degree scale at the north edge of the m. — 1min Grid Zone Dulflflfllofl, as: 56NLP535134 TOL N E, CA ROLI N E ISLAN DS 1958 Walervrlieel of mill; Located obwct Princmal navigation light of lighthouse: Anchorage _ * \1/ Tropical grass; Coconut grove CAROLINETRIUgLJZLIQINSSS 125,000 M ((1) E N NM7 0° 2° 3° 4° 0 o 0 Military Geology of Truk Islands MAP 20 Vegetation 1511700! 366 47/30! 367 368 ' 369 370 371 soioor 372 373 374 375 52/301 376 377 378 379 151°54I30! . 7 '3 2’00’ 7 32,00, ‘ 27 15 l 35 \\ coral coral \\ 22 29 30 “ l 7 2 3 // coral . coral \ sand and shells ,’ \ a, ‘ \ ‘ I \ s _ , ‘ \ x 34 ‘i\ \\ \ \ l as, 2‘ 4° i5: 7 l7 \\ ‘\ coral /,’ 5 \I \ I // .. .. o ~~~~~ VEGETATION MAP, TRUK ISLANDS 832 35 33 EXPLANATION as sand 30 28 c353.. DESCRIPTION coral 35 MANGROVE SWAMP Shallow salt and brackish swamps along the coast and in embayments; vegetation chiefly Rhizophara 33 35 mucranata and Bruguiera conjugata. both having branching aerial prop roots which form tangled barriers impenetrable to 27 3 831 831 —— foot troops and to many amphibious vehicles. Clerodendrum inerme, Excoecaria agailocha, Lumnitzera Iittorea, Xylocamus 31 I granaium, and Sonneratia caseoluris found mostly in the landward margin. Construction materials limited. 35 ._, indicates swept depth area in feet 36 a Pisonia grandis (reef islands), Artocarpus aIiiIis (mostly reef islands), Morinda cilrifolia, Thespesia populnea, Hibiscus liliaceus, 23%| 5." - STRAND VEGETATION Vegetation of coastal-lowland and reef-island sandy soils, consisting of Cocos nucifera (abundant), Harringtonia asiatica, Pandanus teclorius, Scaeuola sericeu, Hemandia sonora, Pemphis acidula, Sporobolus virgim’cus, Vz’gna 74 77 78 7 9 marina, Ipomoea pes-caprae, and Remirea maritima. Vertical concealment good to fair, horizontal concealment poor to fair 71 72 73 75 76 for foot troops; cross-country movement of foot troops good; coconut logs suitable for cribbing, hasty fortifications, and short pilings. 34 COIII — A}. FRESH-WATER MARSH Muck and peat bog; vegetation chiefly Phragmites karka; minor plants Hibiscus iiliaceus, Pandanus 35 '2‘“ :23“; teclorius, Cyperus sp., Scleria sp., Jussiaea suffruticosa, Melroxylon amicarum (ivory nut), and small cultivated patches of at?“ 3 0 mm 30 35 830 830 Cyrtosperma chamissanis and Colocasia esculenta. Vertical concealment generally good for foot troops; construction materials lacking. 34 36 coral coral 23 FILL VEGETATION Vegetation composed of wide variety of plants, influenced by nature of both substratum and fill material; “"4 IM shells Phragmites karka, young Cocos nucifera, Vigna marina, Passiflora foetia'a, Cassia occidentalis, Scleria sp., Paspalum sp., 31 Siachyi‘arpheta indica, Hibiscus tiliaceus, Musa sp., and Morinda citrifoiia found in varying combinations. Concealment for foot troops fair to none: construction materials unavailable. 32d 34 l 31 and / GRASSLAND Open and shrubby upland volcanic areas vegetated with Miscanthus floridulus (swordgrass), Ischaemum mulicum, 35 ‘l I R l 7 K , L A G 0 0 N 34 7’ 30/00! — f 5 _ _ Paspalum conjugatum, Slachylarpheta indica, Passiflom foetida, Sida rhombifolia,Merremia peIfata, Chloris inflala, Wedelr'a 29 ’— 30/00" biflora, Cassia occidentali‘s, scattered patches of Hibiscus tiliaceus, Lanlana camera, Sclen‘a sp., and Macaranga carolinensis, \ 27 8 scattered coconut, breadfruit, and mango trees, and a fern, Gleichenia. Horizontal concealment good to fair in swordgrass. 29 29 \ 829 29 poor in Ischaemum; construction materials restricted to scattered coconut, breadfrult. and mango trees. 19 30 3‘ Ira/l, \‘\\ cggal ‘53 35 ‘5 £2} cit. COCONUT'BREADFRUIT FOREST Areas of mostly semiopen forests and semiclosed forests. Vegetation consists primarily of ' X’,/’ ' 12 ‘\\\ 29 Cocos nucifera and Artocarpus altilis, with scattered Mangifera indica and Hibiscus tiliaceus; understory and grassland 22 “33“ -r"/ o \\\ plants include Derris elliptica, Flagellaria indica, Passiflom foetidn, Sida rhombi'folia, Eleusr‘ne indica, Miscanfhus floridulus, x”/ 31 23 17 “x and Merremia peItata. Vertical concealment good to fair for foot troops in dense forests, fair to poor in included grassland x”/ “"5 Cor/I) \\\ 3‘1 patches; horizontal concealment fair to poor in forests, good to fair in grass patches. Breadfruit trees suitable for bridge 0 .r”/ 21 \‘x\ timbers and construction lumber; coconut logs suitable for cribbing and short pilings. ‘5—91\,.-\\ (9) 33 xx/r’ro \c\ l 0 i coral sand ,’ 11 ‘x 16 I 8 l x r: 2 30 \\ 33 “FlCUS-PANDANUS" FOREST Primary natural ‘forests in relatively inaccessible areas, mostly on summits and adjacent slopes. \QWQ,’ 16 l > “7"" 23 828 328 x / co I I some found along rock escarpments at intermediate levels; composed of Ficus prolixa, Pandanus teclori'us, Hibiscus iiIiaceus, "I 28 , scattered palms, Eleocarpus, and Flagellaria indica. Minor grassland inclusions composed of Miscanthus floridulus, 17 \ sand ,’ coral ‘\ \\ Dimeria, Gleichenia, and Merremia peItata. Cross-country movement of foot troops difficult; concealment for foot troops t3?" /’ 28 \\\ \x ,x” good to fair; construction materials rare. / 41 ‘~.\ to \I 8 7 1‘ 29 ,’/ corzal “~\ 2 ,l’l“‘w39.lz’/ 23 // 16 \\\\ 27 ‘3 lax. 24 TRUK ISLANDS 1’ 17 shells /’ o -f—T 21 ,/ will 31 (3\ 25 coral // 24 3 13 6 coin //’ 28 11/ Osakura slond 827 827 27 . 27 19 __g\ ,7 29 29 v 29 L_, indicates swept depti area in feet 29 29 " 826 826 26 30 -——. iii ,v’T/ \\ /’ \ // 66 ‘l‘ 67 68 69 70 I l I I 28 ‘. 30 ,i’ 29 \ ‘r {,5 ,x’ 29 l ‘ , 825 \ ’ 25 19 27'30’ i— + 27130: 28 27 21 Coral rce , .' u Pouriiay) .' ~ 8 824 000m“. 2 4 23 24 7'27’00’ I ’b ' 7'27’00” i 151'47’00’ 366 000m.E_ 47’30’ 367 368 369 370 374 P 52/30” 376 377 378 37g 151'54’30” 375 W355 3 Scale 1:25.000 Edition 2-AMS (AFFE) .I. _ . l 2 o lstatute Mile » Vegetation b James E. Paseur 1954- 955 U-S. ARMY MAP SERVICE. FAR EAST ‘ 57-041 . R45 - 12/53 - 3-45 r r 1 1 L x t l I Prepared under the direction of the Engineer, Hq AFFE,8A, by the U.S. Army Map Service. Far East. 1000 500 0 lO‘OO 2000 Meters Compiled in 1957 by photogrammetric (multiplex) methods. Coastal hydrography compiled from USHO i 1i--——--l l——i H500 )——-r l——-lo 1000 fi. Chart 6048, 1944. Horizontal and vertical control established by Corps of Engineers, 1951. Names trans- 030 H H 1—«1 H H 2300 Yards iiterated in accordance with rules of the U.S. Board on Geographic Names. Major roads are classified by % . ‘ reconnaissance by the 64th Engineer Battalion (Base Topographic), 1952; other roads are classified from 1 0 lNautlcal Mlle source maps and aerial photography and are not verified by reconnaissance. Coastal vegetation are clas- ' ‘ ‘ ‘ ‘ ‘ ‘ T' COVERAGE DlAGRAM INDEX TO ADJOINING SHEETS sified by reconnaissance by Military Geology Branch, Intelligence Division, Office of the Engineer, Hq AFFE/8A, with personnel of the US. Geological Survey, 1955. Map not field checked, CONTOUR INTERVAL IO METERS Vegetation data based on field investigations 1954-1955 by Military Geology Branch, Intelligence VERTICAL DATUM» MEAN SEA LEVEL 4544 ll NW Division, Office of the Engineer, Hq, U.S. Army Japan with personnel of the U. S. Geological MAP 20 Survey. TRANSVERSE MERCATOR PROJECTION ‘ HORIZONTAL DATUM IS BASED ON THE ASTRONOMIC STATION NO. 2 (I95I) \\ \ . , , . 151 53 34.3 EAST OF GREENWICH. 7 2i’37.7” NORTH \ wV‘w \_ 4544 III SW 4544 III SE 4544 II SW » LEGEND HYDROGRAPHIC DATUM : APPROXIMATE LEVEL or LOWEST LOW WATER § ‘\\$§\\\ MAP 16 MAP 18 MAP 21 \ ,\ v ROADS §\ “3 BLACK NUMBERED LINES INDICATE THE 1,000 METER UNIVERSAL TRANSVERSE § All weather MERCATOR GRID. ZONE 56, INTERNATIONAL SPHEROID § 4543 IV NW 4543 IV NE 4543 I NW hard surface, two or more lanes wide 7,-.. , None BUIII‘UD area ¥.¥.- . THE LAST ”REE DIGITS OF THE GRID NUMBERS ARE own“ § . \' MAP 17 MAP 19 MAP 22 ' 3.} \\‘ loose or light surface, two or more lanes wide ,. . . None Church; School; Cemetery 7.... §§$\\\\t§?§&§\\§“§ \\t\\\ I . \ l \.".:.\\ v. . ~\ hard suilace, one lane wide WW..- ..- None Limit oi danger line; Submerged reel COMPILAIION METHODS loose or light suilace, one lane wide . ... NON Wreck. Sunken, Exposed Photorstereo Photo_p|3nimgt[ic fair or dry weather, loose surface, two or more lanes wide ::::; Sunken locks; Foreshore flats . GRID ZONE DESIGNATION: To 5'" ‘ ST‘I‘D‘RD REFERENCE 0" V ' " ' " GLOSSARY 56N riils sum to NEAncsr loo mtrtiis K Oror an L ago Fail or dry weather, loose suilace, one lane wide -i- :: :::::: Rocks bare or awash; Reel 100,000 M. SQUARE IDENTIFICATION SAMPLE POINT: + SUNKEN ROCK A. USHO Chart 6048. 1944 (reliability good). Unun en cape, point Cari "BC"? trail ,.-....-.._....m, —— ——————- Depth Curl/95 and Soundings I" Falhoms . LR", Mm Manny.” 100,000 mm, Aerial photography: Feb, July 1946. - square in which the paint has: LP Standard gauge railroad, SII‘IEIe [lack .,.,..s... 7 w _‘l—‘—'+_ Reserve"; Dam; Ditch .. 2. Locate firslVERTlCAL grid Iinelo LEFT of Standard gauge railroad, double track WW-.. . ‘ LP 90"" and ind LARGEiIKures labelinzibe 2’.” Salt evaporator: . ,.-,--,-- -,. 777..-... line either in the top or bottom margin, or Narrow gauge railroad. single track -.,7i.-.., APPROXIMATE IlEAN oecuunron 1955 ontheiinalisall: 75 , , 1%" rorr cznren or snsrr Estimate tenths iiom grid lineto point: 4 "all" time ”Midi double 0' "WIN"! "m .-.- —"—“—"_ Rice Paddy: Marsh ANNUAL MAGNETIC came: I’ EASTERLV ‘ 3. Lacatelirsl HORIZONTAL grid line snow . . . / pornt and read LARGE figures labeling the Power transrmssmn lllle ..-__...,V.77,. 7.... ......... / Una diagram only to obtain numerical vulva. lino either in the left or right margin, or . . , , , Nipa; Man rave ..... - - - IGNORE the SMALLER figures or any a m l t ll: Spot elevation in meters. Checked, Unchecked 7. ..-, I.“ "ms 3 To deterrmne‘ league»: north lino, cm" ’5' mi number; these are ror lindrnl [:i.m:i;nleeliisll:iwm pm [me to point: 28 Wall Levee Cllll % PIVO' POW" P 00 "’0 M “90 0’ '5‘ "WP the lull coordinates. Use ONLY the ' ' T” "TWWWTT" " I? i“ Woods; Scrub with the value of the angle between GRID Wt“: "lures 0' the 2nd number; SAMPLE REFERENCE; LP764283 "WM?" 0' "II“; ”we“ 05”“ -.. . . ~ . 0 "9' NORTH and MAGNETIC Noam, a: prom; on “m“: 82 000 Ii reporting beyond 13° In any aimllon, 1 Principal navigation light 01 lighthouse; Anchorage -. 7 * \l/ tropical grass; Coconut grove . . the door-o scale of the nor”! dye of the map. ml" GM 1"” D“"""‘°"' ‘5: 55NLP764233 M OEN NW, CAROLI N E ISLAN DS 1958 TRUK ISLANDS ‘ , I 7“ W\ f V\ T 7 CAROLINE ISLANDS 125,000 MG If}... N ~~‘ W 151°47’00” 366 4730’! 367 358 Military Geology of Truk Islands ts...) v 00 2° 3° 4° 5° 6° 70 MAP 21 Vegetation I... LLLLJILL ’l I .iri 1.1.}, 369 370 371 50/00” 372 373 ‘ 375 52/30” 376 151"54/30r 7°27i00” l I , _ r ‘ , _ 7°27v00” ' 22 I 28 I I I L5é . ' .3 “if“ utilise. , .. \ .. Mi/ 25 wire W / ‘ J Effigy , VEGETATION MAP, TRUK ISLANDS a. or ,x 25 EXPLANATION - I'ili‘r iii/Iii Err // iii?” fiEs‘J Tito/L / % a. ,. IT ivbl UOLA R 1 , (OROR 822 ,,,,,M,.W7, 34 DESCRIPTION MANGROVE SWAMP Shallow salt and brackish swamps along the coast and in embayments; vegetation chiefly Rhizophora mucronato and Brugur‘era conjugata, both having branching aerial prop roots which form tangled barriers impenetrable to foot troops and to many amphibious vehicles. Clerodendrum inerme, Excoecaria agallochu, Lumnilzora littoreo, Xylocurpus granatum, and Sonneratia caseolaris found mostly in the landward margin. 822 I (”K \ .-':._;.,=h .. ’ l . . . . a. ‘4‘“, ‘ 55ng £131}: EP UP Construction materials IImIted. HG I _- 6; 7 ‘ Co al ‘\\\ oral 0/: l / 3 5 STRAND VEGETATION Vegetation of coastal-lowland and reef-island sandy soils, consisting of Cocos nucifera (abundant), I \‘ ’/ \ 7’ 4 19 66 - Pisom'a grandis (reef islands), Artocarpus altilis (mostly reef islands), Morinda citrifolia, Thespesio populnea, Hibiscus tiliaceus, “I ‘15} 15‘ Barringtorria asiatica, Pandanus tecrorius, Scaeuola sericea, Hernandia sonora, Pemphis acidula, Sporobolus virginicus, Vigno I //;:l marina, Ipamoea pes-caprae, and Remirea maritime. Vertical concealment good to fair, horizontal concealment poor to fair I I/ 8 for foot troops; cross-country movement of foot troops good; coconut logs suitable for cribbing, hasty fortifications, and I \X 39%) \fi 4 .: a . _ / / f short pilings. ~ 15 I \\,,./ {i ' %m% k ., . ‘ . ' , /” 821 _ _ . . . . . . .. ~»“‘::::‘:;~,,,E b ~~~~~~ , . 1 ,E‘véi‘e Niki. -- . ' . ' .- v - ' . 23 821 ‘ML _Ih-__— FRESH-WATER MARSH Muck and peat bog; vegetation chiefly Phragmzles karka; minor plants Hibiscus triraceus, Pandarrus I, atria L l“ @wfi§§%\t& \ (If . . .: . 8 ’ f» _ ____...Z_ tectorius, Cyperus sp., Scleria sp., Jussiaea su/fruticosa, Meiroxyion omicarum (ivory nut), and small cultivated patches of IV » gm ., NW . 3' . m Cyrlosperma chamissonis and Colocasia esculenia. Vertical concealment generally good for foot troops; construction materials I i " ‘ Era} if ' ' ‘ V I lacking. I & " ' ’I W i 31 30 .. ,. . , FILL VEGETATION Vegetation composed of wide variety of plants, influenced by nature of both substratum and fill material; ‘i‘ 17 sand ‘4 ‘ Phragmites korka, young Cocos nucifera, Vigno marina, Passiflora foetia'a, Cassia occidenlalis, Scleria sp., Pospalum sp., I I ‘ Stochytarpheta indica, Hibiscus tiliaceus, Musa sp., and Morinda cilrifolia found in varying combinations. Concealment for I foot troops fair to none; construction materials unavailable. I, . 27 .2”) i I , early coral ///, i ‘ GRASSLAND Open and shrubby upland volcanic areas vegetated with Miscanthus floridulus (swordgrass), Ischaemum muticum, ‘,\ I r, , / 8 are k" ‘‘‘‘‘‘‘‘‘‘ i.” '5 " Paspulum conjugaium, Stachytarpheta indica, Pussiflora foetia'a, Sida rhombifolio,Merremia peltata, Chloris infloia, Wedelia \ .. . . ‘ I I, 13 9E1? 29 1/ 25’0“" ‘ biflom, Cassia occidentaiis, scattered patches of Hibiscus tiliaceus, Lam‘ana camaro, Scleria sp., and Macaranga carolinensis, \16 A I g , ‘ i, _ “ “b i 1: Ff; 25 00 scattered coconut, breadfruit, and mango trees, and a fern, Gleichenia. Horizontal concealment good to fair in swordgrass, \ \ {/9 ‘i I ‘ OROR EN E‘MOSET ‘ 1.33m: \\ x} Coral I poor in lschaemum; construction materials restricted to scattered coconut, breadfruit, and mango trees. \ i“ 8 I I 6; { 421 m’TV/Lt/ ‘ £154 \\ \7o\ 1 \\\\T\/ WIT/OJ (Eb/s / C11 12 \\\\- ‘ COCONUTBREADFRUIT FOREST Areas of mostly semiopen forests and semiclosed forests. Vegetation consists primarily of [39“ l\5\\\ I //'l§\13_/liI/V‘/\ (@gg, cm, ‘ 6 Cocos nucifera and Artocarpus altilis, with scattered Mangifera indica and Hibiscus liliaceus; understory and grassland \\\\\,\ IL >>>>> / 12—1/ ,V/ \I’ x: I plants include Derris elliptica , Fiagellaria indica, Passiflom foetida, Sida rhombifolia, Eleusine indica, Miscanthus floridulus, / L" \\ “y I 1i 9:111 T xi"? I and Merremia peltal‘a. Vertical concealment good to fair for foot troops in dense forests, fair to poor in, included grassland ll 17 I I I /,)\7<:"/ 3 I I patches; horizontal concealment fair to poor in forests, good to fair in grass patches. Breadfruit trees suitable for bridge I""".\ 62 ,i """"" 1I7 I‘ /” //\\\;r’f '\ . ‘. y - , 20%| 23 I timbers and construction lumber; coconut logs suitable for cribbing and short pilings. sand “I'd she”: 39/ (”LIX/f 34 9%? ‘i\ , gun/fen Neoiiwb' I \ ‘ .' . 81 77m...“ I I/ (a z x P ‘X , ' 2 z’ii/ / i, , ,, \ 819 19 __ h “FlCUS-PANDANUS" FOREST Primary natural forests in relatively inaccessible areas, mostly on summits and adjacent slopes, \\ ‘.\ ”"11 \ J /i‘ z ,7 \ > , l I ”V some found along rock escarpments at intermediate levels; composed of Ficus prolixa, Pandanus tectorius, Hibiscus tiliaceus, L52: 2337:; ‘3‘, 12 ~vbji,\v\__ "4/ ”L“ 4 $3M scattered palms, Eleocarpus, and Flagellarr‘a indica. Minor grassland inclusions composed of Miscanthus floridulus, // \§;6>\\\\ , \ ' Dimeria, Gieichenr'a, and Merremia peltata. Cross-country movement of foot troops difficult; concealment for foot troops \\ // \§:$\\\ /,’ good to fair; construction materials rare. / / {é}\:\\ II I J \ \ \ I X— I \\\\\ I 29 32 i \ ‘\ i 21 16 \x/fcqf’i; i’f“ vi”? 25 . / r 15 / / i/ /521 ‘O/\‘\ 20 34 22 818 818 .E.. 18 I‘ WN 18 i _.. , 31 18 sand 19 E54 a???" 15 22 \ , 16 IS \\\\ . \ \ ._ / , .. TRUK ISLAINDS l 19 ‘ x \\ I TRUST TERRITORY OF THE PACIFIC ISIANDS CAL, ‘ “r\j\\ 23 l 22 16 (U.S.A. ADMINISTRATING AUTHORITY); I7 \ \ . l l 817 .. 17 ,b x i7 I §§. ’ 8 I 18 I ' l\\‘.‘ \9///\L5_2J I _ 17 +++ 13 21 I //“\\ I 66 ‘L Eh} 817 .vKufuo:_Roinf L_Iindicates swept depth area in feet 816 is m coral I 22’30” 816 12% K3539"??? ‘ lil’l" is Ill 17 815 OUOnIN' , . ' p . ‘ f 2230’ r “c0973, b~ fit}; c02i91,/"; \Kg/fl 5/ 5’ k,‘ r. _ ' . . . g . - . .'”‘~_| K": D \s,/ d 12 l , R 5} I32 053%.: 19 cow 2§j§§2d§ $34534 " I E333 chad, /14 ' i 7‘22“)” Egg} 4‘ fiCoral \ \ ~10 \\ ‘ Ii 0 . \ sand x; logy 15 x”\l _ . ‘ - -. \ \__/—\ ~ g at ‘ - ‘1 ' ' \ ’ — . 7 T 12 3 $233) ’6 EN UN " ' - " ' T— “ ' \ 2‘3 Cora —QBOR . ~ ’ 8 , b‘ sand 15 . is. a x .7» 5 23 / ,2/10 coral coral 16 ETEN ANCI‘IORAGE Coral/"x c022, / ii i e ,2 T ' *- 3 — 17 - x , i it; 333% r W ‘3 DI V’) ’/ 7°22'oo” 151’47’00” 366000rn£i 372 373 374 P 52’30” 376 379 151'54’30” 375 W855 5 Scale 1:25.000 Edition Z-AMS (AFFB . 1 E 0 lStatute Mile Vegetation by James E. Paseur, 1954-1955. “-3- ARMY MAP SERV'CEr FAR EAST ' 57‘041 ‘ R'15 ‘ 12/58 ' 3-“ Prepared under the direction of the Engineer, Hq AFFE,V8A, by the U.S. Army Map Service, Far East. 1030 500 0 1000 20,00 Meters Compiled in 1957 by photogrammetric (multiplex) methods. Coastal hydrography compiled from USHO 1000 500 0 1000 2000 Yards Charts 6048, 6050, 1944. Horizontal and vertical control established by Corps of Engineers, 1951. Names 1 H I._, H H ,_, ‘ transliterated in accordance with rules of the U.S. Board on Geographic Names. Major roads are classi- 1 % 0 IN t‘ IM'I fied by reconnaissance by the 64th Engineer Battalion (Base Topographic), 1952 and reclassified from . . . 3“ ma 'e aerial photography dated 1955; other roads are classified from source maps and aerial photography and COVERAGE DIAGRAM INDEX TO ADJOINING SHEETS are not verified by reconnaissance. Coastal vegetation are classified by reconnaissance by Military Geology Branch, Intelligence Division, Office of the Engineer, Hq AFFE/8A, with personnel of the U.S. Geological CONTOUR INTERVAL 10 METERS w \\\\§s‘\§§{§§ ‘ ‘4 Survey. 1955. Map not field checked. VERTICAL MUM: MEAN SEA LEVEL NERVE 4544 0 NW Vegetation data based on field investigations 1954-1955 by Military Geology Branch, Intelligence {“31“ ‘3‘ MAP 20 Division, Office of the Engineer, Ho, U.S. Army Japan with personnel of the U.S. Geological TRANSVERSE MERCATOR PROJECTION \ \«x \ ~ survey' K HORIZONTAL DATUM Is BASED ON THE ASTRONOMIC STATION No. 2 (rear): i \\ \ ‘ ' - I I ' I Ir \ LEGEND ISI 53 34.3 EAST OF GREENWICH. 7 21 37,7 NORTH \\ 4544 III SW 4544 III SE 4544 II 5W HYDROGRAFHIC DATUM: APPROXIMATE LEVEL OF LOWEST Low WATER MAP 16 MAP 18 MAP 21 ROADS . BLACK NUMBERED LINES INDICATE THE 1.000 METER UNIVERSAL TRANSVERSE ‘ \ All weather MERCATOR GRID. ZONE 56, INTERNATIONAL SPHEROID ‘4‘??? N . a LANES THE LAST THREE oisrTs or THE GRID NUMBERS ARE OMITTED \, 4‘53: 4543 IV NW 4543 IV NE 4543 I NW hard surface, two or more lanes wide _ BUIlt-up area V\:€S\.\‘”\ J .1... 6,, \wesgss MAP 17 MAP 19 MAP 22 loose or light surface, two or more lanes wide _. —:—:—: Church, School; Cemetery §>’\\‘:"'\ ‘ ,.‘\\\\\\\ . :-.«,~?1‘\\\\.s hard surface, one lane wide _ “LEA —— Limit of danger line; Submerged reel .7 ., COMPILATION METHODS loose or light surface, one lane wide , . *7 m Wreck: Sunken; Exposed . 7,7 . , . I 4 45 Fair or dry weather, loose surface, two or more lanes wide Sunken rocks; foreshore flats ___ o 09 GR'D 10“ DESIGNATION: 7° GIVE A STANDARD ““5““: 0" F d h l f I d 0" “0::“5 56N THIS SHEET To NEAREST 100 METERS GLOSSARY air or ry weat er, oose sur ace, one ane wI e :::===== Rocks bare or awash; Reel .fi, ' N m ba C ‘ I k t I] 3 Hits 100,000 M, SQUARE IDENTIFICATION SAMPLE POINT. .t SCHOOL A. USHO Chart 6048, 19“ (reliability good). 0:" 9°: chorag: . c 1 . . .. 3! rec, in L _._-__- Depth Curves and in Fathom: 1. Read letters Identifying 100,000 meter 8' USHO Chart 6050' 19“ (”I'ab’l'ty good). Unun 8" —_——_Capei point Standard gauge railroad, Single track 77 _._+__..._ R __ D _ D't' squarein which the point has: LP Aerial photography: FOIL, July 1946. eservoir, am: rcn _.___ 7 2. Locate first VERTICAL grid line (0 LEFT of ‘ Standard gauge railroad, double track __,,_ , point and read LARGE figures labeling the . 2’s” Salt evaporator: LP Ilne either in the top or bottom margin, or Narrow gauge railroad, Single track ,.__ H L APPROXIMATE MEAN DECLINATION i955 on the line itself: 78 2’6 > FOR CENTER OF SHEET . Estimate tenths from grid line to paint: 1 "3"“ gauge railroad, dOUble 0' multiple "39k vv fl Rice Paddy; Marsh u h ANNUAL MAGNETIC guns: I, EASTERLV 3, Locate first HORIZONTAL grid line BELOW I, . ‘ point and read LARGE figures label vi the Power IlanSmlSSlOll line 7, _ ,,,._.,,, .7, fl... . I: m use diagram only i0 obtain numerical values. line either in the left or right magi: or 800! elevation in meters. Checked, Unchecked 7 W “ 11.5 ‘vos N'Da; Mangrove Mi ‘ ‘ To determine magnetic north line, conned the 'GNORE‘I" SMALLER "W“ 9'?" 0" "1° “"9 "5‘”: 16 - , I. n K'ld number: "I!“ are '0' Miami Estimate tenths from grid line to point: 8 Wall; Levee; Clilf fin“ 7Ag~#,,ifi #m% ‘:1 . PM” P°’"' P 0” ”'9 50“” Edge °f ”'9 "WP the full momma"; Use on” the W f . _ a lower Woods; Scrub with fhe value of the angle between GRID LARGER figures of the grid number; SAMPLE REFERENCE: LP781158 “Whey ° ”1"" Low“ We“ ,,,_.__.,_ bb—vi 0 DE NORTH and MAGNETIC NORTH, as plotted on "mp“: 815000 Ir repairing beyond 13° in any direction, Principal navigation light of lighthouse; Anchorage # * 3/ Tropical grass; Coconut grove #—_7 the degree scale or the norfh edge of the map, — meme“ 1°” D""""‘°“' '5‘ 5(‘3NLP78‘168 1958 MOEN SW, CAROLINE ISLANDS TRUK ISLANDS CAROLINE ISLAN 138 1125,000 3% .1,_L,1,.i, .1 0 30 Military Geology of Truk lsla nds Coral 11 ( #9117" j L1 6ononI ’le 14 99;” ”N” ”110 16‘ r Mncoversfl foot 2 at _, " nu b n \ 15 2 fl 8 r \ Uncovers. 2 feet ,, 15 * 1 1 4 23 4 13 14 0R0 Un n ,,gn Unukop 12 EN I Fl/SIN I I I i_.1 indicates swept depth area in feet 21 16 o fwd / ‘“ 11 " ‘ “,1 - 1 C29 Q4») , ®\\ \10/ / 1: \ 22 12 o‘ 4 1\(,, //a\ 1 22 (2? \ \ f C? C” 25 \Qflmacora U // ‘ 5 ~ 1 <3 C ,/ ,5; I ‘1 m ”V ,1 23 3 VEIGETATIONTMAP, TRUK ISLANDS a10 EXPLANATION DESCRIPTION foot troops and to many amphibious vehicles. 1119 marina, Ipomoea pes-caprae, and Remirea maritima. MANGROVE SWAMP Shallow salt and brackish swamps along the coast and in embayments; vegetation chiefly HIu‘zop/zora mucronata and Bruguiera conjugata, both having branching aerial prop roots which form tangled barriers impenetrable to Clerodena'rum inermc, Excoecaria agallocha, Lumm'tzenz littorea, Xylacarpus granatum, and Sonneralia caseolaris found mostly in the landward margin. Construction materials limited. STRAND VEGETATION Vegetation of coastal-lowland and reef-island sandy soils, consisting of Cocos nucifum (abundant), Pisonia grandis (reef islands), Artocarpus altilis (mostly reef islands). Morinda cilrifolia, Thespesia pnpulnea, Hibiscus (Mucous, Barringfonia asiatica, Pandanus feclorius, Scaeuola sericea, Hernandia sonom, Pemphis aciduia, Sporobolus uirginicus, Vi'gna Vertical concealment good to fair, horizontal concealment poor to fair for foot troops; cross-country movement of foot troops good; coconut logs suitable for cribbing, hasty fortifications, and 23 sand and shells «we cm... ! L;.,...._m.,c.._...u,._ OROR EN KI'J‘KUWU 18 I 12 I en Unum 12 22 1‘5 Uncov s ’ 8 n0 0 . 4° 5 15° 7 MAP 22 Vegetation 1 I I l I 1 I .,1_1,,I,1.,LJ,111. LL14, L. -, 3 52130” 76 379 151°54'30” , 1 1‘221001 1 / 5 if; 0 17 K4/ 23/ 23 1/ AL / 511113111 ANCHORAGE / , ,r “““““ x g, / 19 1, I ”fa “\\ _, / 17 coral 81 item $12,137::ng I ’155 ‘4 t' . - ’1 1.4 ncoveis >00 WEE, I; 12—;7‘ 1’19 / l/cural ,/ // / 10 or 29 ’ coral \ 17 coral ; coral I $31; ,1 1 3/5) ///// l 1—1 _,,4’ / / AWN I I ’jfifiiltn 1 / ,’ coral 813 I (a, 0 al 'v/‘\ ’ soar 20 coral l i I 1 “MI 1 l 1 1 1 1 24 sand 812 Li I TUnuié>Winikof s 12 / a , " I/// T I 55 17 1 er's 1 foot , 1 , , 1 16 , ,I coral i I l 1 1 l 1 , Un’coyers/ ‘ 1 ,I13i\ I [moral 1 1 1 / I , , ,,, ,,p _..,, ,,, 22 1 1 coral ,’ 1 1112/ #91 ,m 01 125,1 ‘ l 10,1 18 1 , I coral I TRUST iTERRlTORY 01 THE PACIFIC (SD coral ISLANDS 31 811 2 0’00” 1 // r ,I 053th ARANG‘ 17 13 I TI 15 ,, en “mono ,' o 1 (U.S.A. ADMINISTRATING AUTHORlTY) . , , I <1) Egg, 1’ I 1 so A 8 I 1 3, 10 T R U K sand and shells 15 1/ 33 16 1’ ,1' 15_54 sand and shells/1, (I T R U K L A G O 0 N 1 / \‘\,\\\ I \T\\ s 12 17 \ 25 1.; V 12 35 809 I , ‘ ' ' 28 l ' "1 12 1'6\ 1 c 1‘1 2%4‘ ‘ 12 / 1 3 4 ’5/ / I \s\ 21 1. I I 4 36 28 808 I I short pilings. FRESH-WATER MARSH Muck and peat bog; vegetation chiefly Phragmires karlra; minor plants Hibiscus Iiliaceus, Pandanus @/ tectorius, Cyperus sp., Scleria sp., Jussiuea suffruficosrz, Metroxylon amicarum (ivory nut), and small cultivated patches of y 1 Cyriosperma chamissonl's and Colocasia esculenfa. Vertical concealment generally good for foot troops; construction materials , \, 41 11:3 _ To lacking. 1 I123 \1 8 2 g \l ‘1 I \1/ i: \ 1 1 1 \ I III 11 FILL VEGETATION Vegetation composed of wide variety of plants, influenced by nature of both substratum and fill material; I \\ 1 ' _ ' ' ' ' ' ’ . " ' ’ ‘ . ' 1. P .1 1 \\ II “WI Phragmites karka, young Cocos nucrfem, Vigna manna, Passr/luro foclzda Cassia UlfCldLnlaIlS. Selena sp aspalum sp 377 5330,, 378 379 15105430” \\ SfaChylarphefa indica, Hibiscus tiliaceus, Musa sp., and Morinda cimfolia found In varying combinations. Concealment for 7°17’OO” H K; 7017,00,, ,0 X . 4 1. \ foot troops fair to none; construction materials unavailable. geTa‘Lrgé/lsland _‘ 11 \ fa Atkin 1311-11111 N k \ 13 GRASSLAND Open and shrubby upland volcanic areas vegetated with Miscanfhus floridulus (swordgrass), Ischaemum muficum, 305 “ 805 u °"°P\c\or.i 23 Paspalum conjugatum, Siachytarphela indica, Passiflora foetida, Sida rhombi/olia,Merremia pcltata, Chloris inflata, Wodelia ‘1 j 6] \\ . \ biflora, Cassia occidentali‘s, scattered patches of Hibiscus tiliaceus, Lanlana camera, Scleria sp., and Macoranga carolinensis, 45’ IEI>N2UKANAP \\ l scattered coconut, breadfruit, and mango trees, and a fern, Gleicheriia. Horizontal concealment good to fair in swordgrass, ,c 1% 3: / 1‘ 8 poor in Ischaemum; construction materials restricted to scattered coconut, breadfruit, and mango trees. a 77%;? 5 27 1“ 117 ,,,, ' 11 ‘ 8117 COCONUT-BREADFRUIT FOREST Areas of mostly semiopen forests and semiclosed forests. Vegetation consists primarily of Cocos nucifera and Artocarpus altiIis, with scattered Mangir‘em indica and Hibiscus riliaceus; understory and grassland 17 plants include Derris elliptica, Flagellaria indica, Passiflonz foetida. Sida rhombifoli’a, Eleusine indica, Miscant/ius floridulus, ”x and Merrcmia peliata. Vertical concealment good to fair for foot troops in dense forests, fair to poor in included grassland [1” ~ patches; horizontal concealment fair to poor in forests, good to fair in grass patches. Breadfruit trees suitable for bridge 1\8 15_01 timbers and construction lumber; coconut logs suitable for cribbing and short pilings. 804 \ _/ 804 x 1 ”FlCUS-PANDANUS" FOREST Primary natural forests in relatively inaccessible areas, mostly on summits and adjacent slopes, \} 18 1713011 _ some found along rock escarpments at intermediate levels; composed of Ficus prolixa, Pandanus teclorius, Hibiscus tiliaceus, ; E/Sopofiu scattered palms, Eleocarpus, and Flagellaria indica. Minor grassland inclusions composed of Miscanfhus floridulus, l ’ 17,30” 8 000m ‘__<_ Dimeria, Gleiclzcnia, and Merremia peltata. Cross-country movement of foot troops difficult; concealment for foot troops ,1, 06 N good to fair; construction materials rare. 21 ‘1' ' 806 1 I I 1600" _ . can? y _ 5100" Shells K3 I 1 34 35 Faneu Island I \o‘ , 1 \ I I cm' shells 37 59‘ \ 11 191/ \ l l shells I / 11 ° \ ' gravel and shells I 1 I 21 Q{ DR EN SAPOU 22 ,1 ‘ 1 1 2 1 / I éi I u I4 U 3 1’ 1’ 803000111. N. 5&1 or? 1, as x I 31 33 I 4‘ 1’ $1 I 55 WW “03 1 o 1 1 1 4 1’ I / 1 1 L; l 5 1 717100” I I ‘ o I I «30 ‘t 1 II C'maliItos 2 4 / ' 22 I ' . . / 151“4710011 366000m£ 47,301, 367 363 369 370 371 5010011 377011011. ' ' " ' 7°1710011 , 1E. 5330” 378 379 151°54'30" 52’30” 376 377 378 379 151°54’30” W856 5 Edition 2-AMS (AFFE) Scale 1:25.000 1 l E o . . . - 1 1 1 . P 1 1 1 2 15mm Mile Vegetation by James E. Paseur, 1954-1955. u.s. ARMY MAP SERVICE, FAR EAST - 57-041 - R~15 - 12/58 - 3.4a Prepared under the. direction of the Engineer, Hq AFFE,’8A, by the U.S. Army Map Service, Far East. 1000 500 0 1000 2000 Meters Complled m 1957 by photogrammemc (multiplex) methods. Coastal hydrography compiled from USHO 1 1———1 1——1 1-—1 1-—-t H FM: Charts 6048, 6050. 1944. Horizontal and vertical control established by Corps of Engineers, 1951. Names 1°00 50° 0 1000 2000 Yards transliterated in accordance with rules of the Us, Board on Geographic Names, Mayo, roads are class,_ 1 11—4 1»——~1 i—i 1-——1 1——1 , fl fled by reconnaissance by the 64th Engineer Battalion (Base Topographic), 1952 and reclassified from 1 O 1Nautical Mile aerial photography dated 1955; other roads are classified from source maps and aerial photography and ‘ ‘ ’T—T-T ‘ ‘ PH ‘ i . are ”0t VerlfIEd by reconnaissance. Coastal vegetation are classified by reconnaissance by Military Geology COVERAGE DIAGRAM INDEX TO ADJO'NING SHEETS B anch,‘1t.l|' :. ' c1; 1 1 ' ' - . {Hwy '19:;g821:p012v;12:1d Cam: 0; the Engineer, Hq AFFE/SA, With personnel of the US Geological CONTOUR INTERVAL 1O METERS WITH SUPPLEMENTARY CONTOURS AT 5 METER INTERVALS ‘~\\\\\\\§§Q\\\\\‘\‘ V c . , . . : ‘ C. 8C {'3 . \ \ Vegetation data based on field investigations 1954-1955 by Military Geology Branch, Intelligence VERTICAL DMD“: MEAN 55“ LEVEL ' \\‘®\ 4544 ll NW Division, Office of the Engineer, Hq, U.S. Army Japan with personnel of the U.S. Geological \ Sum, TRANSVERSE MERCATOR PROJECTION MAP 2° HORIZONTAL DATUM IS BASED ON THE ASTRONOMIC STATION NO. 2 (1951) lsr‘sa’aaa” EAST OF GREENWICH, 7"21/37.7I’ NORTH LEGEND - 4544 III SW 4544 111 s: 4544 ll sw ROADS HYDROGRAPHIC DATUM: APPROXlMA‘I’E LEVEL OF LOWEST LOW WATER MAP 16 MAP 18 MAP 21 All weather BLACK NUMBERED LINES INDICATE THE 1.000 METER UNIVERSAL TRANSVERSE . ”mm MERCATOR GRID ZONE 55 lNTERNATlONAL SPHEROID 1 “'89 ~ , J LANE: _ 71 ,, . , ha-d sum . Mn 01 mm lanes mde Builtup area _.,L,,,i,,,,,,4_ .. , ‘ ,w ‘ 911 ms usr maze News 0,, 71112 512111 111111135125 A“ omrrso 4543 IV NW 4543 IV NE 4543 l NW 10059 or light surface, two or 111016 lanes wide , 3;-;-LAN‘S Church, School; Cemetery ,,imd , ,7 77,, t 1’ {Gem MAP 17 MAP 19 MA|._..|P 22 hard surface, one lane wide , , , , , —— Limit of danger line, Submerged reel ##A,” , . + loose or light surlace, one lane wide _.. __ Wreck, Sunken; Eyposed ,,,, "_ ”7777777" ,,,, ,,, Au 4°45/ COMPILATION METHODS . M11 0009/ _ , , F3” 0' dlY weathm, IOOSE SUlIaC€1IW0 0l more brie: Wlde rm: *1 , , Sunken rocks, foreshore flats ,,,,,,,,,,,,,,,, ,7 I 1 San 0R 840:”5 amp zone DESIGNATION; To GIVE A STANDARD REFERENCE 0N PM” stereo“ PHII‘OIU‘VDIan'm‘eI‘VIIC Map GLOSSARY Faii (11 dry weather, loose surface, one lane wade , :7 ;, 7 , Rocks bare or awash; Reel * as 3 MlLS 56” THIS SHE“ To NEAREST 100 METERS & \ 'I I 4I 0"" en L age \_ 1110.000 M. SQUARE IDENTIFICATION SAMPLE POINT: * CHURCH Unun an ' C3” “3“ 11211 ~ ,, — ______ Depth Curves and Soundings In Falhoms ,,,,,,,,,,,,, 20f: 1% ‘ A. USHD Chart 6048, 1944 (reliability good), cape, pomt _ . , SHO Chart 6050 1944 (reliab'l't d 31 d . _m.__,______ 1 ma letters 1411111111111; 100,000 meter 3 U , 11y goo ). an m gauge railroad, single “a” ' " ”IT Reservoir; Darn; Ditch ,,,, 7 ,,,,L a I 2 :quaretm which the paint I195: LP Aerial photography; Feb, July 1946. Standard 3” e ralroad, 11 Ill ‘ k 7 7 , . ocate irsl VERTICAL RfldIil‘le to LEFT of g g | ou e rac , 2/5” Salt evaporators {gag point and read LARGE figures labeling the Harrow gauge railroad, Single track ,,,,, —-p-» ’TTT'TWWT"’777 LP line either in the top or bottom margin, or 2’6" L , APPROXIMATE MEAN DECLINATION l955 on the 'me itself: 71 Narrow gauge railroad, double or multiple track —-w—-—“'—w— Rice Paddy' Marsh . - FOR CENTER OF SHEET Estimate tenths from grid line to poml: 3 Pmr he“ 11 W m x ' "”"V ""‘" “‘“U‘L "AGNET'C WAN“ " “575“” H 3. LocatefirstHORlZONTAL 311111111; snow 151 13 1 1 / . , , ******* .._ - * ~ ,, . , D. u» 111w «111° 01.... awn-«11 1m 122;“..‘1211'72‘Iltlf15é‘flfzir'fiii'lfi‘lf WI" 111911111011 ”I "‘9‘“? ”“19“? ”Wheat!“ ,,,, " M ‘166 ”13' “mm ,,,,,,, "i i ‘ to 491.111.1119 magnetic "or”. 11",, conned 11.. canon: m SMALLER irgum ofany ,,,,m 111111115211: ' 12 - , »' ~ . ,. ,, grid number; these are for 1111111111: E 1' t t "1:! dl 1 ' 1; 11111, Levee, 1111 , , .___W§Z\‘§ Woods, 3111111 , ,,,, W I: 111101 pow r on the 900"! edge orunmop me ,,,, 100111111193. 11“ 011111111. “m” 111 "'1“ 1111 '19 Wow 2 Waierwheel UI ml“; Located 0mm 13 010“” ,,,,,,,.. ' "_— wrfh the valve of Oh: angle bow GRID LARGER figures of the grid number; SAMPLE REFERENCE: ”9713122 11‘ :- “opal mass C c t g o e NORTH and MAGNETIC NORTH, a: plotted on "amp“: 805003 If reporting beyond 18" in any direction, u: l ; 0 cm: i v ,_ , ,,, ,,,,,,,,,, the degree scale at my north edge of the map. .. We?“ (311d 1°“ Designation. “1 56NLP713122 U MAN N CARO LIN E ISLA W. NDS 1958 Principal nav1gat:or1 light ol lighihcuse, Anchorage , 7 V 7 _ ‘. 4 v}? ,. . a. , .. 1.141...‘ . £5! ,. $1Mi535§v a? , 3.5: . ‘. _. v. t 1 Military Geology of Truk Islands TRUK ISLANDS T VI Vt \ V CAROL! N E ISLAN DS 1-25 000 ' i l ‘ 0. 2e 3e .e 5e 6., e. rims Aenue of Approach and - i / A , i Cross-count Movement I77 L1.l 4.1, 1 l1..l_oi.LLi7LLLLJ-1.l ry 3 :71 — 3. am 3 . , ,, 15103200, 339 32,30” .40 342 343 35,00, 344 345 346 47 48 37/511 49 do 51 151 3973927100” 727100” I , I s\ / I I l i 0K/ \N" 2703 i l e; i 3° 1e .39.. \‘a , ! ,e/ \\ I 29 T g I T/ 1\\ /5i‘x\ . AVENUES OF APPROACH AND SUITABILITY FOR 33 so I I 24) A " I - .o“\ I K 4 I CROSS-COUNTRY MOVEMENT MAP TRUK ISLANDS —- " 9D“ I 25 “i"; 29 PA C I F I C 0 C E A N . 75; 7 , r, e .11 ~ T e I ‘ i’ 61 I - .ré T e ‘ I25 x A coiai l 77-\7 77777777 7777777 77 7777: 7 7 ;7 7 777 7 77 937 .73177T77777777777__._.7..777 . 777T 7157 .. .77...-77.7777.7_7‘ 823 32? 7 23 / Suitability terms, in order of decreasing suitability, are: excellent, good, fair, poor. and unsuitable. CCM \ / T! T \ 3 1.. coral \ 1—1 I ‘ / evaluation based on the jeep. Airborne operations evaluations based primarily on capabilities of 0-119 \‘ ~ ”\éfia I 52 «2—7: ‘ /‘r‘<\ \7 »/ / T l 7 \\ /, and H-19. / E. 155 g Suitability for Suitability for summary of Conditions 27 I I. Landing beaches Assault _ . Ulilt Vehicular Foot»troop Terrain description . I g aircraft Airdrop Helicopters movement movement Assault aircraft Airdrop Helicopters Vehicular movement Foot-troop movement T .. I (See Amphibious Airfield runways on fill. Only Moen airfield is in opera- Moen Airfield presently in use. Generally good; trees a hazard Moen Airfield excellent; aban- Concrete runways at abandoned airfields I % Operations tion (1955); crushed coral surface. Concrete runways Abandoned fields need minor on abandoned fields. Surrounde doned fields good to fair. broken and, in places, under a few inches E ,00/—’ “W" "I‘WIST ,0 chapter for GOOD TO GOOD TO EXCELLENT EXCELLENT EXCELLENT of abandoned fields (Moen, Eten, and Param) are repairs and some clearing. ing areas marshy. Coconut trees a local hazard. of water. Surrounding areas marshy. I '7 data on FAIR FAIR TO FAIR broken and in places have sagged below water table; beaches) coconut groves grow on some runways. 7 W H 29 822 822 Fill, O to 4 feet high~tide elevation, generally level and Rough ground and scattered Numerous sites; coconut trees, bomb craters, and local Generally good traction; local wet areas; 28 firm. Local marshy areas and unfilled bomb craters. trees prohibit assault aircraft marshes are hazards. Assembly and exit generally fair. unfilled bomb craters especially near airfields. Generally unrestricted move- UNSU TABLE GOOD TO GOOD TO GOOD TO EXCELLENT Grass, brush, and account trees, singly and in combina» landings. Filling bomb craters Coconut trees probably no restriction to jeep ment. Locally marshy areas with ____________________________ l POOR POOR POOR T0 FAIR tion. and local wet places and clear- movement. tall swordgrass. ing trees would probably provide some site. Beach suitable Sand beaches, mostly less than 20 feet wide, and The small size of beaches and the numerous coconut Some small sites; beaches Beaches narrow at high tide; good traf— 27 for all types adjacent sandy areas separated from beaches by 1-f00t‘ trees generally prohibit airdrops and assault aircraft narrow and coconut trees ficability; gradient about 1:10. Coconut trees of landing GOOD TO high SCZ’DS- Well drained. Sandy areas covered by landings. Clearing of trees might enable small—scale common. probably no restriction to jeep movement but ’ craft. UNSUITABLE UNSUITABLE UNSUITABLE GOOD EXCELLENT coconut trees 20 to 25 feet apart. airdrops, would hinder larger vehicles. (/7-/" 26 7 / /47/e/ ’eoral . Predominantly grassland with scattered brush and Steep slopes, scattered trees, Scattered sites; trenches and Scattered sites; trees, boulders, Boulders, bedrock pinnacles, and trenches Tall grass impedes movement '77 7 ' * * “ 77.7.7-7...77_ 821 821 trees; grass on uplands 3 to 8 feet high; slopes less and rough ground prohibit boulders may make assembly and trenches are hazards. local hindrance. Clay soil has good traction and conceals trenches and fox- UNSUlTABLE FAIR TO FAIR TO FAIR TO GOOD TO than 30%. Some bare bedrock; boulders and WW ll assault aircraft landings. difficult; generally poor exit; Generally partly restricted when dry, slippery when wet. Dense grass holes. POOR POOR POOR POOR trenches common. somewhat restricted approaches. conceals hazards and may impede some approaches. wheeled vehicles. Beach suitable Forest, mostly coconutebreadfruit, of various densities, Dense forest prohibits most airborne operations. Possibly a few small helicopter Moderately dense forest has heavy under- Moderately forested areas have for sha|[ow.draft in places a 40-foot—high closed canopy. Slopes less sites and hovering operations are locally feasible. growth; although dense forest has little under- dense undergrowth; dense forest - POOR TO GOOD TO than 30‘”. th I l d t d t ’t h s 5 ar nder rowth landing craft. 7o grow , cosey space rees o no permi a p se u g . coral 12 UNSUITABLE UNSUITABLE UNSUITABLE UNSUITABLE POOR vehicular movement. Clay soil slippery when wet. f3 23 { 3 4 21 Areas of mangrove swamp, fresh-water marsh, and Steep slopes, dense forest, or low wet swamps and marshes prohibit airborne Stee slopes and rock cliffs sto movement On uplands direction restricted _ \ p P 22 2 ’00” 25100: 7 J densely forested steep (over 30% slope) terrain. Operations. on UplandS; mucky bottoms and dense man- by escarpments and thick tangl- 77 _________—. 8230 19 POOR TO ‘ d - d vine t t 8 C grove stop movement in swamps an mar e 5 may 5 op movemen . 20 20 UNSUITABLE UNSUITABLE UNSUITABLE UNSUITABLE UNSUITABLE shes. Men sink waist deep into swamp bottoms, about a foot into marshes. 24 23 28 sand an shells 7 0 ”/77- .77\\ // (/7) /I \ X], 77 sssss 7 /// Coral 21 ”7.47”” 24 29 477/" 21 710 27 . % 22 5 TRUST TERRITORT or THE PACIFIC ISLANDS , Q) 24 page...) 22 2‘ 29 (U.S.A. ADMINISTRATING AUTHORITY) 12 fl; ‘ A eza/ I .‘T’/ 18 31 177/ 27 7 19 3 19 47 19 19 819 19 21 28 7/ 57 23 4,7./‘/ 23 20 747/" 18 ® 2 "a 17 28 77--/' 27 21 / \ l—J /”// 21 Coral ® I ‘04 H"\“) 27 /774L’/ 30 $311 17 ” Coral \4 17/74/7" l7 ‘ \_77/O\ m 3\ 29 24 7/7,//‘/7 coral 23 \(‘3 {/Ei‘~@orai E“ G} 7//’/7//7 \x// 77/ 77-// 17 11 . indicates swept depth area in feet ,7.//"/7 23 T' 15 7,-—/’35 18 I ” 21 16 \A . /7-// 4 I W3 77 7.7777..- 818 818 . 18/7- 7/ 18 7 (iTErTTTCoral lb I 27 r ”if 11 II 6 i 74/” \§ . . l 1g T 7 / .T 17 I15 7%» 7 7 n, - I //7./" T 21 T Cape Ole] 7 W 1 / . 13. $93; 77 “a i (Q 25 /'3 I 15 coral /' 13 . l v ,/2i\ 15 3 I 17 9 j? ‘2 13 9% 16 19 Keir") 133‘ 1‘ 27 e. 17 / 1 “5 oval T Coral ‘ . fl‘Coral reef l 17 gm «big/3 15 i I I' 7’ ‘N I gagsczral I I 23 16 fl ' . - ‘ E . ». - ‘ dies < 17 a; j 12 15 11 of 4.71%” r " . . ‘ [1 . ‘ 7 7 77 7 7 ‘7 777 . 7 7. 77 7777 ,7 7070141 7. 77 77 777......7.. 77777777 817 817 ‘ l7"' 777 a A LAMOSEU BAY ,T - 4T”: - ) 7 . 21 23 mama 1 f 523% @Coral .' . , . - 19 16 .7 _. 11 ' 7. . 7 30 Masai); ' 2‘60"": (E? 11 Y - 7 7 4 " ' , - I ' Q I 33 21 15 CW“ "a" . nun en Sapofa . - ' ,7 -. ‘ d, _ \ . . . -' ‘ ' '. com 25 a ' 7 “' . - Y - A x" I F I SI 18 1 ._, . 39 4O (2.} 412; .--. 22 .. coral - . .. 7 c T _ .. 816 ”I . ll ‘ ém‘ _ " I “ 7 — - . 7 7 I .. " -J ,. ' ‘ 7 \3 ’. g 7 _ 7 Mg? 7. 7777 77 777777 ,7 77777777 516 _ I xxx 1. . . (a er? TO . . 4 . . 24 f 8 T . 1 7 7 7 , -' ’ . . I ‘ Q 20 24 21 19 / l7 17 H , . . T , . _ -. 22130” —— —T}— 23 ' . I . . . . . T .. T’ 17 ———— 22’30” ‘0 I “ 7 I i I ‘ ‘ ' ' ' ‘ ‘ \' ' 7 11 T/5\Tr 21 29 7 , . , ,T 7 . 7 . . \ . 13 /33\\,/ I /21\\ " / 7 . " C . A I. 7 I ' A ‘ ’ f “If? T I. ”I \ ' 11 15 1 i I 2\ . , . _ . . .. 7 T. 7 . . —‘.- x, 14”] I KJ20 27 15 A . ’ 7 ~ . ‘ ‘ ' , 7 Mk 7. i ' ' . . M . . 815 81500°m~N —— ‘ I5 . "w" M '- 7 _ .,~ 7 ' _ \zfii“, 1,53 -~ - e: o 17 ' I 3 3 1 » i . ~ 7 ' - «7 ‘ "a; r, ’ mm a Tehionsl \ 11 16 I z A Z 2 , v I] ‘ . ‘ . ,y'; 2 b Coral reel T A f , . . A. . n M: . . iT -7 ~ . Cral Ti}. // /5 19; T . / . , . ° iT . ~.'» 12 Coral I T 33 \ 19 l _ ‘ ' _ 2 . _ T 7 ' ‘1 1661’ T' -. 10 15 11 \|/' 7. l Ly 17 - ll . ' 7» , . 7 ' - . , a. 7 7 (A: . reL. 22 I A J0 . -. . . : . . - . . b 10 7 /\ 1 y I] 29 313 20 ’ 0L B Y x 7 . ‘ ‘ ' ‘ I L/ w ' “on H ”I > E \E) Coral r'°T 7°22’OC” I l T ~ " ’ ‘ . ' . ‘ ‘ .16: - . .- 7\//¢@§\ 7°22700I 151°32’00" 339 0001111.: 32/30” 340 341 346 p 348 37/30” 350 351 151°39’30” 347 W856 S T Scale 125,000 Ediiivn 2'AMS (AFFEJ 1 i o lStaiute Mile Interpretations for airborne operations and cross-country movement by 11.3 ARMY MAP SERVICE. FAR EAsT , 57 041 - R15 ~ 1/59 - 3 40 i i I i I i I I I I I " Richard L. Hay, 1954-1955. Prepared under the direction of the Engineer. Hq AFFE,’8A, by the US. Army Map Service, Far East. 1000 500 0 1000 2000 Meters Compiled In 1957 by photogrammetric (multiplex) methods. Coastal hydrography compiled from USHO I 1000 500 0 1000 7000 Yards Chart 6049, 1944. Horizontal and vertical control established by Corps of Engineers, 1951. Names trans- T H 1 T T__T 1—1 1-—1 1 : literated in accordance with rules of the U.S. Board on Geographic Names. Major roads are classified by 1 V 77, reconnaissance by the 64th Engineer Battalion (Base Topographic), 1952; other roads are classified from 1 7 O Imam“ Mlle 7 . 7 . 7. 1‘ ’1 l . . . 1 . . . ' COVLRRCIT; DIAGRAM INDEX TO ADJOINING SHEETS source maps and aerial photography and are not verified by reconnaissance. Coastal vegetation are clas- sified by reconnaissance by Military Geology Branch, Intelligence Division, Office of the Engineer, Hq AFFE/BA, . . 7 77 .77.- 7777. 7. ..7. 7 7 with personnel of the U.S. Geological Survey. 1955. Map not field Checked. CONTOUR INTERVAL IO METERS : i ‘ i ‘ VERTICA ATUM' MEAN ” A E l’ “3 >5 LVL 4544|lNW Airborne operation and cross-country movement compilation based on field observations 1954- MAP 27 1955 by Military Geology Branch, Intelligence Division, Office of the Engineer, Hq, U.S. Army TRANSVERSE MERCATOR PROJECTION Japan with personnel of the U.S. Geological Survey. HORIZONTAL DATUM IS BASED ON THE ASTRONOMIC STATinN no. 3 (13.511 151°53’34 3” EAST OF GREENWICH, 711/377” NORTH 4544 III SW 4544 III SE 4544 II SW LEGEND HYDROGRAPHIC DATUMI APPROXIMATE LEVEL or LOWEST Low WATER MAP 23 MAP 25 MAP 28 ROADS BLACK NUMBERED LINES INDICATE THE I 000 METER UNIVERSAL TRANSVERSE All weather HERCATOR GRID, ZONE 56, INTERNATIONAL SPHEROID 4543 IV NW 4 4 E 4543 I W 5 3 IV N N m SUTTmT two 0, mm Tam We 77 7 7 None 8,0”po ma 77777 THE LAST rungs DIGITS or THE GRID NUMBERS ARE oMirrEo \ \\\‘ ‘iwi‘e 1' NM surface 'W’ or more lare de None Church School Cemeler M I k\\\\\\\\\ § MAP 24 MAP 26 MAP 29 Leo . g. Tlu . . .15m 7 , , y. . ..7 & .mx‘ux“ 7 fluid suilace. one lane Wlde 7 77 77 None Limil ol danger line, Submerged reel 7777777777 COMPILATION METHODS loose or light suliace one lane wide 77 None Wierii Sunken, Exposed 77 / 7/ 4°45, ”0101;5me Photo-planimelric Map o°ii’ i‘ ’ . ,1 777.77 T Fail or dry weather, loose suiiace, iwo or more lanes MM :77; 7 7777 Sunken rocks; Foreshore llais 7 l I if OR GRID [ONE DESIGNATION I To GIVE A STANDARD REFERENCE ON :\\\ § [I ' ' ' l I I on TT/ T71 a: mu; 56N T Tiils SHEET TO NEAREST loo METERS \ ‘ ' I 4 GLOSSARY Fair or dry weather, loose surface. one lane wide 7 7 : 7 Racks bare oi awash. Reel 3 Mil-SI / T/ 100.000 M. SQUARE lDENTlFlCATlON I SAMPLE POINT: TRAIL JUNCTION A USHO Chart 6049 1944 (reliability good) Berg mountain peak T T} T I T T " 1 7 ’ i - i H.77777777 ...._ 7.47,, .77 .. . .14 *7 i7, 7 m, 7 T Lari track, llflll . .. .7 7 __ sssss Depth Curves and Soundings in Fathom; i /‘/ I 1.R:ad letters Tammy“ 1011000 ”MI I Aenal photography. 1»Feb., “My 1946' Z'Jan‘ 1949‘ Non! en ......7 .L7. 77777777777 Day Standard gauge railroad, smgle track fl _ i/,. T I squaleinwhich the WWII lies I LP I Oror en 7. 7 anchorage Reservoir, Dam, DilCii 77777777777 77 I 2 Locate iiisi VERTICAL glid line to LEFT oi I Unun en cape paint Slandivd gauge railroad, double track 7777 -—+l—-¢+—i+— V I paint and lead LARGE Figures labeling the I I "REV “WV” ' 215i, Salt evaporaims 7 77 777 7777777 7777 LP T I line either in the top or boiiom margin. or I l T Narrow gauge railroad, Single track 777 —r—-‘——-r-— APPROXIMATE «rim DEi7‘7.NA' are I955 i T on’the Imeiisell I T43 , . T T T . 2’6” roe CENTER or swim I Estimatelenthtliol’il grid linelo must I i 91 Narrow gauze railroad. wuble 01 multiple lrack -r—-“-~r— che paddyT Mann 7 ”mm “1.3.." C “.17..“ IA {1.7mm 777—777..._ 71 I 3. Locate IirslHORIZONTAL gnaw. oiiow I I i _ T .' poini and read LARGE were; late ‘13 War I PUWEI LailSl‘iilSSan line .. .. Use diagram only In Obtain numerical value: ____ 77__ . line ertller in the left or right inarg :1 or T I Spot elevation ll‘ meters Checked Unchecked ‘ my ”/45 "ID“? Maw“? 7777 7777 7 To deiermine magneeic Henri line, canned 91» WW" the SMALLER figures M W T on the line itself 1 I .. TT . . Ef‘d ”WWW. lhese are '0' WWW: l Estimate tenths Irorn gird Inc to mini I I Will, Levee, Cllli 7 ____I 373$ 9"“ 90”" P 0" ""3 ’W’I‘ edge ‘7' 9’9 ”up the lull coordinates Use ONLY the I I T Woods, Scrub 7 777 7 7 7 7 7 77 777777 Mm the Value 3‘ the angle berween GRID LARGER figures of the and number. I swag 93:115th vialeiwiieei ol mill, Located turn. 7 I3 ,, 0'1 ' NORTH and MACNrrIc NORTH, as plotted on “’amP‘e- 815000 I; ii loporilng beyond 15w » U DOT SW CAROLI N E ISLAN DS Principal nawgation lignl oi ligninousr Anchorage 7 )l‘ ~17 Tropical glass, Coconut glove 7 7 7 the degn- cute Ail the north edge 0f the more. _ — ll “”1" Gl'd I‘m" new): 7 1958 TRUK ISLANDS l7 7 Military Geology of Truk Islands CAROLINE ISLANDS 1:25,000 IF O L N“ MAP 24 Avenues of Approach and Cross-country Movement 3 o 151°32'00" 339 32/30ll 340 342 343 35’00” , 345 51 » 151393041200” 7°22’00” '0/ "fl . " .1, J; J u: \ ..; ' _ 4:. 1. 3: (511251;: ‘32)“ .> I 23 Coralgij‘b/ 5% Cor‘ 24 1 k Ira I Q3212») 3 l »' , ’ , .. _ ms. Ro ENMIS I N , 1 1 _ 201001! —‘ A ‘\\ —“— 8 """ 3 /_ ‘ I= . . .3. ’I , i‘fil 8 g 16 4 (Vii/l \gé/l/ 20,00” l8\\\ 9/ g - : ' ~_, {1‘ "ya I . ‘1 (/TA‘\ coral \\\ 28 15 / 15 . 16 . ‘. ' ’ITW: \\ Z 1‘ \\ ' ' \1 4i \‘\ com an en Unikopi 12 ““” \‘x. 14 \\ 24 23 29 23 \\\ [LICK HARBOR O 810 1 O H .- ' ' ' \UIW I . 9 o \x - - 1 .. 1,, , 1 . 1m /°\ 11111 Efiral x 2-; "en’V-Una 8 13 1 . p " W—qo\ 1 {J /\\I \ 3 I 24 41 4 52 l 2: 23 4 / 15 1,1 I I " cora 25 2 F1? 17 .l 9' ’ 2- H EN WISENIF I; 3 e G) @ 'v \ \‘s \ .1 2 . . 2;‘\\ ‘ k I , 1111' en Ono' lI 25 22 22 3 a 1i hllsx _, . san an se \\\ ll . 5% 2 III 23 211 i AVENUES OF APPROACH AND SUITABILITY FOR 1109 \Q9 “(73; .23.. CROSS-COUNTRY MOVEMENT MAP, TRUK ISLANDS coral 3 2 2‘ 22 3 coral coral \ an?" 1» ;3 / 11 2} / ll 4 coral 09 7 \— \ 12 O 11 \\\ H” 15 Z 18 (:3) 22d 3 \\\ 1 I; I I K L A G O 0 N Suitability terms, in order of decreasing suitability, are: excellent, good, fair, poor, and unsuitable. cora sa 2 \x 29 809 29 11 COM 2 3 corn 19 evaluation based on the jeep. Airborne operations evaluations based primarily on capabilities of C-119 ( ‘ ; \‘~\\ and HA19. ( 17 ‘~.\\ 2) \\ coral I \\ Suitability for I Suitability for . Summary of Conditions ‘\.\ 25 . \‘x Landrng beaches Assault Vehicular Foot-troop Terrain description 1 \ . . \ \‘~\ 28 aircraft A'rdmp Helicopters movement movement Assault aircraft Airdrop Helicopters Vehicular movement Foot-troop movement 22 \ ~.\ coral \\ ‘ ~\ ' so (See Amphibious Airfield runways on till. Only Moen airfield is in opera- Moen Airfield presently in use. Generally good; trees a hazard Moen Airfield excellent; aban- Concrete runways at abandoned airfields 25 23 19 19 ‘1‘ \2§~\ Operations tion (1955); crushed coral surface. Concrete runways Abandoned fields need minor on abandoned fields. Surround- doned fields good to fair. broken and, in places, under a few inches 8 IIIII can, /—\ fl 1\ \\\ chapter for GOODRTO GOOD TO EXCELLENT EXCELLENT EXCELLENT of abandoned fields (Moen, Eten, and Param) are repairs and some clearing. ing areas marshy. Coconut trees a local hazard. of water. Surrounding areas marshy. T. 808 08 :‘ 1 ': O8 \ W 18 ‘1 ‘~. data on FAI FAIR TO FAIR broken and In places have sagged below water table; __L. ' caiar ‘2’ Cora “"d \‘1 \‘x beaches) coconut groves grow on some runways. é} ., I, 18 a; 1 coral C I ‘1‘ - Fill, 0 to 4 feet high-tide elevation, generally level and Rough ground and scattered Numerous sites; coconut trees, bomb craters, and local Generally good traction; local wet areas: ora 1‘ firm. Local marshy areas and unfilled bomb craters, trees prohibit assault aircraft marshes are hazards. Assembly and exit generally fair. unfilled bomb craters especially near airfields. Generally unrestricted move- 23 27 '1 GOOD TO GOOD TO GOOD TO EXCELLENT Grass, brush, and cocount trees, singly and in combina- landings. Filling bomb craters Coconut trees probably no restriction to jeep . 25 1 ,- UNSUlTABLE . ment. Locally marshy areas With 23 sand '1 x’/ POOR POOR POOR TO FAIR tron. and local wet places and clear» movement, tall sword rass sand 39 40 i 41 /’ ing trees would probably provide g ' I 21 some site. A I Beach suitable Sand beaches, mostly less than 20 feet wide, and The small size of beaches and the numerous coconut Some small sites; beaches Beaches narrow at high tide; good traf— for all types adjacent sandy areas separated from beaches by l-foot- trees generally prohibit airdrops and assault aircraft narrow and coconut trees ficability; gradient about 1:10. Coconut trees Coral of landing GOOD TO high scarps. Well drained. Sandy areas covered by landings. Clearing of trees might enable small-scale common. probably no restriction to jeep movement but craft. UNSUITABLE UNSUITABLE UNSUITABLE GOOD EXCELLENT coconut trees 20 to 25 feet apart. airdrops. would hinder larger vehicles. x/ 3 807 W“ 07 / . Predominantly grassland with scattered brush and Steep slopes, scattered trees, Scattered sites; trenches and Scattered sites; trees, boulders, Boulders, bedrock prnnacles, and trenches Tall grass impedes movement trees; grass on uplands 3 to 8 feet high; slopes less and rough ground prohibit boulders may make assembly and trenches are hazards. local hindrance. Clay soil has good traction and conceals trenches and fox- \5, UNSUlTABLE FAIR TO FAIR T0 FAIR TO GOOD TO than 30%. Some bare bedrock; boulders and WW ll assault aircraft landings. difficult; generally poor exit; Generally partly restricted when dry, slippery when wet. Dense grass holes. 31 POOR POOR POOR POOR trenches common. somewhat restricted approaches. conceals hazards and may impede some 2é approaches. wheeled vehicles. Beach suitable Forest, mostly coconut-breadfruit, of various densities, Dense forest prohibits most airborne operations. Possibly a few small helicopter Moderately dense forest has heavy under- Moderately forested areas have £33. \ k for shallowdrafi POOR TO GOOD To in places a 40—foot-high closed canopy. Slopes less sites and hovering operations are locally feasible. growth; although dense forest hgs little under- dense undergrowth; dense forest landing craft than 30%. growth, closely spaced trees 0 not permit has sparse undergrowth. __ , ,, 17’30” UNSUITABLE UNSUITABLE UNSUITABLE UNSUITABLE POOR vehicular movement. Clay soil slippery when 17 30 f wet. 806 806000m.N' Areas of mangrove swamp, fresh-water marsh, and Steep slopes, dense forest, or low wet swamps and marshes prohibit airborne Steep slopes and rock cliffs stop movement On uplands direction restricted densely forested steep (over 30% slope) terrain. operations. on uplands; mucky bottoms and dense man- by escarpments and thick tangl- POOR TO ' d — . d ' , PA CIFIC 356 UNSUlTABLE UNSUITABLE UNSUITABLE UNSUlTABLE UNSUITABLE if: 5”” m°vemem '” swamps 3" m‘" Berg: fiéfsgzpmz‘flzflp 0 C E A N bottoms, about a foot into .— marshes. 438 . _ 418 \ 1’ / (12 fl 3.11 "1 | 17 241 x 3A 1 g 15 19 x ‘1 1 , a, I \ 124 I / ° coral \ ‘1 ‘1 I I ? d4 . 7°17’00” ’ 0; 7 17’00” 151°32’00” 339 000m.E 32’30” 340 341 342 343 35’00” 344 345 346 p 348 37/30” 349 350 351 151°39’30” 347 W856 8 Scale 1225,000 - - 1 . . . Ed‘t'O" Z'AMS (AFFE) 1 E 0 lstatute Mile interpretations for airborne operations and cross-country movement by US, ARMY MAP SERVICE, FAR EAST . 57.041 . R15 . 1,59 . 3.40 Richard L. Hay 1954-1955. Prepared under the direction of the Engineer, Ho AFFE/8A, by the U.S. Army Map Service, Far 100° 50° 0 100° 2(100 Men’s ' East. Compiled in 1957 by photogrammetric (multiplex) methods. Coastal hydrography compiled I 10100! I ' solo I 0 1000 2000 Y;rds from USHO Chart 6049, 1944. Horizontal and vertical control established by Corps of Engineers. I H I F f 1—1 ,_, . 1 1951. Names transliterated in accordance with rules of the US. Board on Geographic Names. 1 I 0 IN _ lM‘l Major roads are classified by reconnaissance by the 64th Engineer Battalion(BaseTopOSI’aDhic), . 1 1 . . autrca re 1952; other roads are classified from source maps and aerial photography and are not verified by reconnaissance. Coastal vegetation are classified by reconnaissance by Military Geology COVERAGE DIAGRAM Branch, Intelligence Division, Office of the Engineer, Ho AFFEI'BA, with personnel of the U.S. CONTOUR INTERVAL IO METERS Geological Survey, 1955. Map not field checked. VERTICAL DATUM: MEAN SEA LEVEL INDEX TO ADJOINING SHEETS 4544 ll NW Airborne operation and cross-country movement compilation based on field observations 1954- TRANSVERSE MERCATOR PROJECTION MAP 27 1955 by Military Geology Branch, Intelligence Division, Office of the Engineer, Hq. U.S. Army HORIZONTAL DATUM IS BASED ON THE ASTRONOMIC STATION no, 2 (l95l ); Japan with personnel of the U.S. Geological Survey. ,‘ 151'53/34e" EAST or GREENWlCH. 7'21’37.7'I NORTH 4544 III SW 4544 III SE 4544 || SW LEGEND HYDROGRAPHIC DATUM: APPROXIMATE LEvEL or LOWEST Low WATER MAP 23 MAP 25 MAP 23 ROADS BLACK NUMBERED LINES lNDlCATE THE 1.000 METER UNIVERSAL TRANSVERSE All weather HERCATOR GRID, ZONE 56, INTERNATIONAL SPHEROID _ THE LAST THREE DIGITS or THE GRID NUMBERS ARE 00111111: 4543 IV NW 4543 N NE 4543 l NW hard surlace, two or more lanes wide, , L, None Burliup area L”, , , .m, .. , None icon 6" MAP 24 MAP 26 MAP 29 loose or light surface, lwo or more lanes wide 77., None Church; School; Cemetery 74.-. _ W”, ‘. I . ‘I hard surlace, one lane wrde . W", ,, . None Limil ol danger line; Submerged reef L. 7.. . . + COMPILATION METHODS loose or light surface, one lane wide _ ._ W None Wreck: Sunken; Exposed Lisisi .U «r ‘33" . I “‘5’ Photo-stereo Photo-planimetric Map 11 0 ll on - Fair or dry weather, loose surface, two or more lanes wide 77 —¥ri Sunken rocks; Foreshore llals _. ._ A , ,_ _ . . + + 51" on GRID IONE DESIGNMION' l0 6'" A Simon") REFERENCE 0" m GLOSSARY * H “II-5 56N THIS SHEET TO NEAREST 100 METERS ‘ Benz ‘ ‘ , peak Fair or dry weather, loose surlace, one lane wide . s..;::::: Rocks bare or awash; Reel LL. . \ * 3 "“5 100,000 M. souARt IDENTIrIcArIon SAMPLE romr: TRAIL JUNCTION A. usno Chart 5049, 1944 (reliability good)_ Nom 8" bay , F , , \.i-’\ ,1 . _ . Oror en anchorage Carl track, "an. .. . .. .. . .. _________ Depth Curves and In Fathom: / 1 2 1. Rm Mm immm‘ 100.000 mm, Aerial photography, l-Feb., July 1946, 2-Feb. 1947. Um"I en cape, point Standad a e ra'load, s | t k H 7 ”W N _.._,_+__ _- _ sou-rein whichlha porntlres: LP r 3 ug It In; E lac Resenu", 03m, Ditch A__ _ H _. “viii ,7 @— 2. locale first VERllCAL Ind line to LEFT 0! Standard gauge railroad, double lracli .. , _ H—F nan-m pornund read LARGE 'IKUVES Iabelmgthe 2’.” Salt evaporator: ,7,,4,_,_______ LP line Hill!" In the top or bottom margin, or Narrow gauge railroad, Single track , . —r—-—1— APPROXIMATE uEAN DECLINATION 1955 on the line null: 43 2"” FOR CENTER OF SHEET Estimate tenths from grid lrne to point: 9 "1"")w Eauie la||r03d1 UDUDIG 0i "WWW WEI .. e "tr—‘5‘"— Rice Paddy; Marsh wwflfiiALAH 7v “ “ ANNUAL MAGNETIC CNANGE l’ EAsTERLv 3. Loom Irrst HORlIDNTAL p10 line BELOW C . ’1' . ' ~ . point and read LARGE lrgures labeling the Power lransmrssron lrne ”Wfi , ,, ., LL, , .. . .. , _ ~.. . . .. *k'fii Un diagram only to obhm Mimi VU‘Vfl- lino erlher In the left or right margin, or Snot elevalIon in meiersz Checked; Unchecked .. W6 m6 "ma; ° “' 7° d'"""""‘ ”W'I‘ "M" "n" cm M. $0354:er'IIIELsLeE'Ir'I‘III‘IirIdIIZ E"1'"°1""1°"1‘11°"i 'dl 1 ’ l “1 _ , 1. ,, 1 sum” on 3 mm In me «pom: Wall, Levee; CIIII .L, fl 323$ III: PW", 9°“, P °" "h your”! “9° °I M. "W the lull coordinates. Use ONLY the .. . a TM, WW“; 5"“ W , A wa*# .1911 11.. value or .1... angle bow GRID uranium 111 111. 1.111 1.1111111, sum, “mm“. 1 ngm waIthe“ M m'”' Lucamj Obie“ ' O E E NORTH and MAGNETIC NORTH, as plotted an example. 806000 ll reporting beyond I8‘ In any drrocllun, Principal navrgalron lrghl ol lrghtllouse; Anchorage LL, * \f/ lroprcal grass; Coconut grove “LLJMLL. .7 the doom scale at the nor”! edge of the Imp. — ml" 6"“ 1"" D”'“""'°"~ “3 56NLP489111 TOL NW, CAROLINE ISLANDS Military Geology of Truk Islands TRUK 1.3L. . 151 “x ' .w 1’ . . MAP 25 Avenues of Approach and CAROLINE 131.1%. 3,419,000 - c ,ross-country Movement 354 355 »: A IA ‘ 30 I 1 29 , . 1 1 1 coral 1 29 , 3 t i 1 ‘ 1 4 . 1 1 111811 AVENUES OF APPROACH AND SUITABILITY FOR 1 21 1 \ 26 1 32 1:771 5 \\\‘,. 1 coral l CROSS-COUNTRY MOVEMENT MAP TRUK ISLANDS 2’ ‘1 5 /*~ . 34 l _ r 29 at. l . . . 21 K 1 l . , coral Z7 23 Q", ‘ . , , Suitability terms, in order of decreasing suitability, are: excellent, good, fair, poor, and unsuitable. CCM 1’13 ' 55 ’ 2‘ ()3 ‘ ’ T ’ 7 ’ evaluation based on the jeep. Airborne operations evaluations based primarily on capabilities of 0-119 ;._.1 and H-19. : Suitability for Suitability for Summary of Conditions . 30 31 1 : Landing beaches Assault . . Unit Vehicular Foot-troop Terrain description 31 i 1 aircraft A'rdmp Helicopters movement movement Assault aircraft Airdrop Helicopters Vehicular movement Foot-troop movement 1 (See Amphibious Airfield runways on fill. Only Moen airfield is in opera- Moen Airfield presently in use. Generally good: trees a hazard Moen Airfield excellent; aban- Concrete runways at abandoned airfields Operations tion (1955); crushed coral surface. Concrete runways Abandoned fields need minor on abandoned fields. Surround- doned fields good to fair. broken and, in places, under a few inches chapter for GOOD TO GOOD TO EXCELLENT of abandoned fields (Moen, Eten, and Param) are repairs and some clearing. ing areas marshy. Coconut trees a local hazard. of water. Surrounding areas marshy. EXCELLENT EXCELLENT , data on FAIR FAIR TO FAIR broken and in places have sagged below water table; . E beaches) coconut groves grow on some runways. . . . Fill, 0 to 4 feet high-tide elevation, generally level and Rough ground and scattered Numerous sites; coconut trees, bomb craters, and local Generally good traction; local wet areas; } 1 . 1 firm. Local marshy areas and unfilled bomb craters. trees prohibit assault aircraft marshes are hazards. Assembly and exit generally fair. unfilled bomb craters especially near airfields. Generally unrestricted move- 1 1 1 UNSUITABLE GOOD TO GOOD TO GOOD TO EXCELLENT Grass, brush, and cocount trees, singly and in combina- landings. Filling bomb craters Coconut trees probably no restriction to jeep merit. Locally marshy areas with Wt. ,,,,,, C 52' ______________________________________ : POOR POOR POOR TO FAIR tion. and local wet places and clear- movement. tall swordgrass. 3 /,r , j , ing trees would probably provide 1 23 27 /// ~ 1 some site. 1—1 7,./ Sand beaches, mostly less than 20 feet wide, and The small size of beaches and the numerous coconut Some small sites; beaches Beaches narrow at high tide; good traf- ; ///’/ Beach suitable adjacent sandy areas separated from beaches by 1-foot- trees generally prohibit airdrops and assault aircraft narrow and coconut trees ficability; gradient about 1:10. Coconut trees 3 x/,/’ l for all types UNSUITABLE UNSUITABLE GOOD TO .:- GOOD EXCELLENT high scarps. Well drained. Sandy areas covered by landings. Clearing of trees might enable small-scale common. probably no restriction t'oieep movement but 2/“ of landing UNSUITABLE ' coconut trees 20 to 25 feet apart. airdrops. would hinder larger vehicles. :ZTICoral reef craft. .. c§§al .. :3:»_.Coralreel 11 ‘, Predominantly grassland with scattered brush and Steep slopes, scattered trees, Scattered sites; trenches and Scattered sites; trees, boulders, Boulders, bedrock pinnacles, and trenches Tall grass impedes movement 1’17 . . ’ 411.1 7 '11 ’ T “‘ ‘ ’ ‘1 ’ trees; grass on uplands 3 to 8 feet high; slopes less and rough ground prohibit boulders may make assembly and trenches are hazards. local hindrance. Clay soil has good traction and conceals trenches and fox- , 1 £1 UNSUITABLE FAIR T0 FAIR TO FAIR TO GOOD TO than 30%. Some bare bedrock; boulders and WW II assault aircraft landings. difficult; generally poor exit; Generally partly restricted when dry, slippery when wet. Dense grass holes. 26 1 l, POOR POOR POOR POOR trenches common. somewhat restricted approaches. conceals hazards and may impede some ”’3‘ 24 .1 28 approaches. wheeled vehicles. II II I ‘1 5° . Vb Beach suitable for shallow-draft Forest, mostly coconut-breadfruit, of various densities, Dense forest prohibits most airborne operations. Possibly a few small helicopter Moderately dense forest has heavy under- Moderately forested areas have landing craft. in places a 40-foot—high closed canopy. Slopes less sites and hovering operations are locally feasible. growth;although dense forest has little under- dense undergrowth; dense forest 17 UNSUITABLE UNSUITABLE UNSUITABLE POOR TO GOOD TO than 30%. growth, closely spaced trees do not permit has sparse undergrowth. mar 15 UNSUITABLE POOR vehicular movement. Clay soil slippery when 3 25113-1! —— _ “'61- W W. Gilh - _ .. j.) . \ ‘s . . . . L * \ ’ 1 1“ Areas of mangrove swamp, fresh-water marsh. and Steep slopes. dense forest, or low wet swamps and marshes prohibit airborne Steep slopes and rock cliffs stop movement 0n uplands direction restricted \ densely forested steep (over 30% slope) terrain. operations. on uplands; mucky bottoms and dense man- by escarpments and thick tangl- 13 ‘1 POOR T0 grove stop movement in swamps and mar- ed vines may stop movement. UNSUITABLE UNSUITABLE UNSUITABLE . Unun en Salon 11 C UNSU1TAB1’E UNSUITABLE . shes. Men sink waist deep into swamp '1 .1 bottoms, about a foot into 15\‘\"’ marshes. 18 . it; . 1\ 1 1 15. \ /\ ‘ l . \ . 4 12 I 13 1 i I . . - ‘ 14 16 co‘ral 1 1 1 {fiCoral reef ' ,- . . ., ; ' ’ ' . \\ 23 1 . ,, . Unun en Chosialg 1. f A i 1. l . . 19 22 1. 18 /—\\ 1 o coral i l ’1/@1‘. .17 21 i , 15 ,1 /’ . sand 1 y 22 coral \ :Q./« 71 . n. .5 I I 18 . Pf . 13 I, 16 coral 16 22 . /,/E§ral (i) ll , 18 1 1 ’ ‘1 17 1 . ,1 13 14 ‘ 141;: . .. . , _. , ,,,,, , _. a... - W... ,W. . - W . .1 . . 16 20 115 , 16 1 // 11‘" . ,‘ Coral ’11 i 18 ‘ , 1 / 17 I ' / 1 1 .’ -.4_;-. / l 1 15 / . . 1, 1,,1 sand ’3 1 I I L1 21 {ED 52 1 1 ‘ 15 12 I 51 1 1 lZ/s\\ 1 sand and shells sand and “9'15 I 2 1 16 . l/ 5 \\ 1 . 17 18 0 1,18 1 send .1 “"31 1. j. j 1 I1 K 2—8. //1 1. 1 1 .l ‘\,, I 3 \ i 1 ID .l .5 .f i 12 \\ \\ coral . 18 i ' . ’ , 12‘ ' ” ’ l ' 18 ' ‘1 1 1 22 13—34 1 1 1“ 1\\ 1 .l ‘ l \\ \\ : l 14 19 \ I, I l i 1. i : 1 57-2 F? k 17 1 15 ‘. 11 2: 21 18 1i 19 1“ ~11 1‘1 V 1i coral ‘\ 1i. 16 13 1i. . L4 indicate/s Swept depth area in feet 1 11 11. 1* I . l \ 1\ \ 1 l 1‘ ‘1 I. l 1i \ . 1‘ 1 17 . 1 r”; ‘1 11 1 , {N 13 1 , 60> 6@ 1.414 . W l A - \ s , ““w s , , 1 , s ‘ T W ’ coral i ' O l ._ , , \ 1 \, 1'1 1 21 1 1x .13 // 1 ‘ 18 1 1 1 see: \ \\ . ‘, l OROR E FASAFA \\ ,‘ . . 1 Ts e ‘1 1\ 1 l3 1 1 sagif‘s»-\ & . i / 1 I” ,r/ 15 l coral / \ ”:2/0, coral 9—; t 17 K / \ K 15 /,;/7 W i \H’ 4 U7 1 W. ’ / Kforal. ‘1 1 o ' ""' 1‘31, 1' i 11 ,as. l 17 21 l : a I - .1 , / 1 1 ”1° ,5' 1‘ o 7 3 1 17 @ 15 (13 /1 /1 8 Cm, g . l 4 core i’ . 13 18 1, . 3 \ v/ ,. I“... 1 ' ' . 13 , ~~ . ~ 1 13 ; 1 1 shells 12 1 {flown 1 35:3 355 31.3.1“; W856S Scale 1:25.000 Ed? ' . l . . . . "'0" 2 AMS (AH—E) 1 2 0 lstatute Mile Interpretations for airborne operations and cross-country movement by U.S. ARMY MAP SERVICE, FAR EAST - 57-041 - R-15 - 1/59 - 3.4c Prepared under the direction of the Engineer, Hq AFFE/8A, by the US. Army Map Service, Far 100° 50° 0 1000 2000 Meters RIChard L1 Hay, 1954-19551 East. Compiled in 1957 by photogrammetric (multiplex) methods. Coastal hydrography compiled 1 [W 1—1 1—530 0 1000 ZOOOY d from USHO Chart 6049, 1944. Horizontal and vertical control established by Corps of Engineers, l r—-r r—i r-—i a r-—r 4 ar 5 1951. Names transliterated in accordance with rules of the U.S. Board on Geographic Names. . . Major roads are classified by reconnaissance by the 64th Engineer Battalion(Base Topographic), 1 0 ,1Nam1ca1 Mile 1952; other roads are classified from source maps and aerial photography and are not verified 1 1 1 1 COVERAGE DIAGRAM 1NDEX TO ADJO1N1NG SHEETS by reconnaissance. Coastal vegetation are classified by reconnaissance by Military Geology Branch, Intelligence Division, Office of the Engineer, Hq AFFE/SA, with personnel of the us. CONTOUR INTERVAL ‘0 METERS W1TH SUPPLEMENTARY CONTOURS AT 5 METER 1NTERVALS Geological Survey, 1955. Map not field checked. VERTICAL DATUN: MEAN SEA LEVEL 4544 ll NW MAP 27 Airborne operation and cross-country movement compilation based on field observations 1954- TRANSVERSE MERCATOR PROJECTION \ 1955 by Military Geology Branch, Intelligence Division, Office of the Engineer. Hq. U.S. Army HORIZONTAL DATUIM lsl’BASED ON THE ASTRONooMicI STAIION No. 2 (195l )‘ NW Japan with personnel of the U.S. Geological Survey. ‘5"53 3‘3 EAST OF GREENW'CH' 7 21 37'7 NORTH ‘I‘355"§*3‘3s\\‘°~"§\‘195 §W§X§ 4544 III SW 4544 III SE 4544 ll SW LEGEND HYDROGRAPHIC DATUM ; APPROXIMATE LEVEL OF LOWEST Low w 3-3.3“ ».\ ‘\ ma PMKM\ MAP 23 MAP 25 MAP 28 ROADS BLACK NUMBERED LINES INDICATE THE 1.000 METER UNIVERSAL TRANSVERSE \§§£‘W§§E \\§ in mm, IERCATOR GRID. ZONE 56. INTERNATIONAL SPHEROID 1$“:§§,\ . “\b§"1{\ THE LAST THREE DIGI R N IBE S R (“$13M ‘kfigk 4543 IV NW 4543 IV NE 4543 I NW hard surface, two or more lanes wide A W None Burltup area , ,, W None on 111: or r“ G 1” u R A E OMITTED \\\\\\\\‘\\ MAP 24 MAP 26 MAP .77 , ‘ ~ loose or light surface, two or more lanes wide WW None Church; School; Cemetery WW-.. i I 1951113 x \\\\\\\\ \ \\ 29 4 s \\\\\ \\\\.\\\\\ hard surlace, one lane wide None Limit of danger line; Submerged reel WW 4.”, COMPILATION METHODS loose or light surlace, one lane wide None Wreck: Sunken; Exposed W o'io’ on Photo-stereo Photo—planimetric Map F d .h . I f .l I 'd # > . a4 MILS criio zone DESIGNATION: To GIVE A STANDARD REFERENCE 0N ‘ " ' Fair or dry weamer Inose sur'ace we or mored anes WI 8 Sunken rocks, foreshore Ilats WWWWW W M 56” “"5 SHEET To NEAREST 100 METERS §\\\\\\\\\\\\\ . . Oror en GLOSSARY anchorage air or Ty wea er. oose sul ace, one ane m e W. Rocks bare or awash, Reel WWW 3 IILS 100,000 M. SQUARE iDENTIFICATION SAMPLE POINT: ; SCHOOL A. USHO Chart 6049, 1944 (reliability good). Unun en cape point Cart track; trail . W _ .W ___-_L Depth Curves and ° " in Falhoms 1 LRud loner: identifying 100,000 inner Aerial photography Feb.. July 1946 Standard au e railroad, sm le track , MWWWWW —+—t-—-i- . @\_ ”we” ""1”“ "‘9 ”"1““? LP 2 K g Reserve"; Dam; Ditch ___-..____‘ 2. Locate first vnmcn grid has to LEFT of Standard gauge railroad, double track _W, pomtand md LARGE insures labelinrthe . _ :1.” Salt W__ LP lirie either in the top or bottom margin, or Narrow gauge railroad, Single track _ . W APPROXIMATE MEAN oEcLiNATiow 1955 on the line itself: 58 3"” FOR CENTER OF SHEET Estimate tenths from grid line to point: 9 Harrow 23ng railroad. double 0' "Nimble MCI , *PH" Rice Paddy; Marsh WWW ANNUAL MAGNETIC CHANGE l’ EASTERLV 3. Locate Iilst HORIZONTAL grid Ill'le snow point and read LARGE figures labeling the Power transmission line WW ,,,,,,,,,,,,,,,,,,,,,,, / :l m Spot elevation in meters: Checked, Unchecked W ‘ ms * "1931 "any” —-——T*—TT— " U“ diagram °"’Y '0 °b""1" numerical values. lino either in the left or right margin, or MS To determine WWW north lino, conned m. IGNORE the SMALLER figures olany on .91, 1.". itself: , . 16 , . .. ., 1"“ "Wm”; "'95! I" '0' 'mdlflfl Estimate tenths from and lineto point: 4 Wall; Levee; Clill WWWLWW,WWW, _ma}3§ SCI P'Vo' P°"" P 0" ”‘9 M “9° °f "n map the full coordinates. Use ONLY the w h I l ‘l- ¢ TOW WW5: Scrub 7 ----------- win. m. value of rho angle between GRID lARGElenm ollhe arid numb-r; SAMPLE REFERENCE: LP589164 alerw ee 0 11111111 LOCated 0111601 77* "7" O I: [:1 NORTH and MAGNETIC NORTH, as plotted on “my“: 815 000 II reporting beyond 18' in any direction, _ N D Principal navigation light ol lighthouse; Anchorage W * 3/ Tropical grass; Coconut grove W or. degree ”ale or me nor». odqo of the map. “‘ ""1" 6"“ 1°” D“"""'°"1 “1 56NLP589164 U DOT S E, CARO LI N E '8 LA 8 1958 Military Geology of Truk Islands MAP 26 Avenues of Approach and TRUK ISLANDS VITV (D 1‘7 4 . : \ o o CAROLINE ISLANDS 125,000 1 V I , I ; o. 2. 3., 4 5 6. 7., C 1 1. t . . . . r _ T I ‘ LLLLLELLLLJ OSS coun ry ovemen 151139130” 352 40'00r 353 354 355 356 357 42/30'I 358 359 360 3(151 36.2115/000‘ 364 365 151 ”47m” 7°22,00, _ 1 I 7"22'OO” I T 7 \ 21 \ O/T/ I 7 12 Coral co1'1a| 12 X: I l ‘1 18 I 16 17 ‘ 2 1 ) \‘ 15 ’/ 4 \\' \‘1 17 / f 1 3 1 i I /O—/ 23 \ ‘1 l 1 k\\ \‘t‘ / K \\ CQ/ CJ" cozrlal ’5 1 _, 1 J \\ La—Z‘ \\ \5/ cdral 1‘ \\ 21 I \1 22 > 323 1 Icoral 3 11,: it 55 15 56 \\17 57 5‘8 co?al 59 60 31 12 WA“ .0... 65 l/ \ / 7 15 I .‘ ’ 5%1" ”a x 22 19 V9 3 /’ / \ \ coral O / ® ® 1‘— fl \\ 23 16 \ [I I8 1 5 (i \\ 2 1.2 24 coral 21 V ’ \\_A// \ 3/ coral 23 coral ’0 lo 1] 16 12 17 \\ coral 12 9 “UK 812 cora ’7 812 < a I, 12 . \ / ‘ 6 20 19 /° TRUK ISLANDS 3 \\ 19 2 \ 16 i_i indicates swept depth area in feet 17 ‘1‘ \ 15 3 Te \ 23 \ . 19 23 a) —\ 1“ > coral cor‘al 14 \‘K/ ‘1 \I . 4 \ ll egreai '. \ ‘1 ‘1 19 24 (21 ‘\ I, \\ coral “L— 5: \‘s/ 19 ‘1 oral 8 811 mral \ 1 1 1 1 AAAAA _ c 6 11 23 ‘1 3\ coral I\ 28 21 2 1 \/a_’—/—/— 20/001 x1 + 17 22 CS) —— 18 mi. 16 —— 20/00" I \ E ' 21 1 5 1 L9. I a 17 , ‘5 I \ \ - / [7/ 61 \l \\ 23 // T\8 >\27 QM ’// 'K £3.31 \\ 34 21 19 I‘ A (i \\\ ‘ / I0 T‘—— —__—/T I \ VA ‘ T R U K L A G 0 0 N . .fi 5 ‘1 23 20 3 18 I \ coral 20 2 4 : cgr7al coral com 2; I 18 coral 21 1 ,, AVENUES OF APPROACH AND SUITABILITY FOR 2 29 | I 's 810 810 ,o 10 I CROSS-COUNTRY MOVEMENT MAP TRUK ISLANDS ‘0 -. _\T 1\ a 30 18 4 4 / ‘1 l \ l ’ ., , 22 i \ °" ’ . 3.2. x/ 22 [7’ 41 ‘1‘ 23 [I \\ Suitability terms, in order of decreasing suitability, are: excellent, good, fair, poor, and unsuitable. CCM TRUST TERRITORY OF THE PACIFIC |SLANDS 8 // A i 1 evaluation based on the lee . Airborne o erations evaluations based rimaril on ca abilities of -11 18 /’ 22 x y.\ I and 11.19 p p p y p c 9 (U.S.A. ADMINISTRATING AUTHORITY) \\—I/ / \ . a; I x a; I 18 II \ Suitability for Suitability for Summary Of Conditions I 19 ,1 \\ Landing beaches Assault . . Unit Vehicular Foot-troop Terrain description 1’ 18 \ aircraft Airdrop Helicopters movement movement Assault aircraft Airdrop Helicopters Vehicular movement Foot~troop movement I \ 17 (/11‘\\ I \\ (See Amphibious Airfield runways on fill. Only Moen airfield is in opera- Moen Airfield presently in use. Generally good; trees a hazard Moen Airfield excellent; aban- Concrete runways at abandoned airfields 809 1' 4 ‘1 09 / 1 Operations tion (1955); crushed coral surface. Concrete runways Abandoned fields need minor on abandoned fields. Surround~ doned fields good to fair. broken and, in places, under a few inches ,, ~ . 809 “xx—x} ’1 \ chapter for GOOD TO GOOD TO EXCELLENT EXCELLENT EXCELLENT of abandoned fields (Moen, Eten, and Param) are repairs and some clearing. ing areas marshy. Coconut trees a local hazard. of water. Surrounding areas marshy. / \\ data on FAIR FAIR TO FAIR broken and in places have sagged below water table; ’11 \ beaches) coconut groves grow on some runways. 22 P ,,—”’/’ 23 \\ 28 24/ _________ \ Fill, 0 to 4 feet high-tide elevation, generally level and Rough ground and scattered Numerous sites; coconut trees, bomb craters, and local Generally good traction; local wet areas; 7/ \ firm. Local marshy areas and unfilled bomb craters. trees prohibit assault aircraft marshes are hazards. Assembly and exit generally fair. unfilled bomb craters especially near airfields. Generally unrestricted move- Q 21 (I \ UNSUITABLE GOOD TO GOOD TO GOOD TO EXCELLENT Grass, brush, and cocount trees, singly and in combina- landings. Filling bomb craters Coconut trees probably no restriction to jeep ment. Locally marshy areas with (I \ POOR POOR POOR T0 FAIR tior. and local wet places and clear- movement. tall swordgrass. ,_-_ ___________ 1’ ‘1‘ ing trees would probably provide ................. / some site. .23 \“xEJ A Beach suitable Sand beaches, mostly less than 20 feet wide, and The small size of beaches and the numerous coconut Some small sites; beaches Beaches narrow at high tide; good traf- 23 19 for all types adjacent sandy areas separated from beaches by 1-foot- trees generally prohibit airdrops and assault aircraft narrow and coconut trees ficability; gradient about 1:10. Coconut trees ———————————————————————————————————————————————————————————————————————— a of landing GOOD TO high scarps. Well drained. Sandy areas covered by landings. Clearing of trees might enable small-scale common. probably no restriction to jeep movement but E—~~—— UNSUITABLE UN . NT . 8 308 > -r»——*” 21 08 craft. SUITABLE UNSUITABLE .21 ' GOOD EXCELLE coconut trees 20 to 25 feet apart. airdrops. would hinder larger vehicles. 08 __— ’T— / . L Predominantly grassland With scatteYEd erSh and Steep slopes, scattered trees, Scattered sites; trenches and Scattered sites; trees, boulders, Boulders, bedrock pinnacles, and trenches Tall grass impedes movement 21 trees: grass on Uplands 3 t0 8 feet high; Slopes 1655 and rough ground prohibit boulders may make assembly and trenches are hazards. local hindrance. Clay soil has good traction and conceals trenches and fox- 21 UNSUITABLE FAIR T0 FAIR TO FAIR TO GOOD TO than 30%. Some bare bedrock; boulders and WW II assault aircraft landings. difficult; generally poor exit; Generally partly restricted when dry, slippery when wet. Dense grass holes. POOR POOR POOR POOR trenches common. somewhat restricted approaches. conceals hazards and may impede some 52 53 54 19 5 5 approaches. wheeled vehicles. 17 24d 21 27 5a" Beach suitable Forest, mostly COCOHUt'bfeadfoitI Of various densities. Dense forest prohibits most airborne operations. Possibly a few small helicopter Moderately dense forest has heavy under- Moderately forested areas have I” for shallow-draft in Places a 40-foot-high CIOSEd CGHOPY- Slopes less sites and hovering operations are locally feasible. growth;although dense forest has little under— dense undergrowth; dense forest landing craft. POOR TO GOOD TO than 30V. growth closel spaced trees do not permit has 5 arse under r wth 4 UNSUITABLE UNSUITABLE UNSUITABLE 1 ° ' y . . p 3 ° ' A ‘ UNSUITABLE POOR vehicular movement. Clay soil slippery when wet. .___.__,,,..L. 807 807 5 _ Areas of mangrove swamp, freshwater marsh. and Steep slopes, dense forest, or low wet swamps and marshes prohibit airborne, Steep slopes and rock cliffs stop movement 0n uplands direction restricted 16 (Island) densely forested steep (over 30% slope) terrain. operations. on uplands; mucky bottoms and dense man- by escarpments and thick tangl- 19 . . . 21 68 UNSUITABLE UNSUITABLE UNSUITABLE UNSUITABLE POOR T0 grove stop movement in swamps and mar ed Vin-es may stop movement. 70 UNSUITABLE shes. Men Sink waist deep into swamp bottoms, about a foot into L._—I indicates swept depth area in feet marshes. \\ | 23 \lo/ I \‘\\ 25 : 0%?“ 24 cgirlal 11 \\r 1 17/30” — 18 7 .\~.\ I —— 26 — 17/30" 1 , ,’ ‘\\ ‘ coral 1 Q i ‘\ I = “2 29 1’ ' 2-3 806 25 . “1 , t _ 806000m.N_ 06 21 O6 7 .’ : O6 ‘ 21d \ 1’ I ‘1 23 san \ *' ’ 29 27 \ [I T i‘ .33. 23 / 24 1 by; I 29 / . l I 13 ‘ \ / Q I / l \\\ II ' 25 23 4‘ 22 “‘~\ I I 231' Coral 16 '/ 25 \‘\\\ 23 /,, I 24 cora ’ 3T ‘\ g , i I r. 28 2 3 ‘\~\‘ I I 30 coral 27 7,17l00, I X% 15 ,, a 17 f \ 24 \g 22 I I 7,17,00” 151‘39’30” 352000m.E 40/00” 353 354 355 356 357 42/30” 358 359 360 P 362 45'00” 363 364 365 151”47’OO” 361 W855 8 Scale 1:25.000 Edition 2»AMS (AFFE l . . . ) 1 , , 2 9 35‘3”” We Interpretations for airborne operations and cross-country movement by U.S. ARMY MAP SERVICE, FAR EAST- 57-041 - R-15 . 1/59 , 3.40 ' I K L I 1 Richard L. Ha 1954-1955. Prepared under the direction of the Engineer, Hq AFFE/8A, by the U.S. Army Map Service, Far 1000 H 500 I J 1000 20,00 Mae's y, East. Compiled in 1957 by photogrammetric (multiplex) methods and from 1:55,180. USHO 1000 500 O 1000 2000 Yards Chart 6049, 1944. Coastal hydrography compiled from USHO Chart 6049. 1944. Horizontal and l 1»—-1 ,_, H ,__i ,__.1 4 fl vertical control established by Corps of Engineers, 1951. Names transliterated in accordance 1 g. 0 lNautical Mile with rules of the U.S. Board on Geographic Names. Coastal Vegetation are classified by reconnais- . . . . . ,___f r } sance by Military Geology Branch, Intelligence Division, Office of the Engineer,Hq AFFE/BA,with personnel f th U.S. l ' . ‘ . T o e Geo ogical Survey, 1955 Map not field checked CONTOUR INTERVAL IO METERS WITH SUPPLEMENTARY CONTOURS AT 5 METER INTERVALS COVERAGE DIAGRAM INDEX TO ADJOINING SHEE S Airborne operation and cross-country movement compilation based on field observations 1954- VERTICAL DATUM: MEAN SEA LEVEL 1955 by Military Geology Branch, Intelligence Division, Office of the Engineer, Hq, U.S. Army Japan with personnel of the U. S. Geological Survey. TRANSVERSE MERCATOR PROJECTION 4544 ” NW HORIZONTAL DATUM IS BASED ON THE ASTRONOMIC STATION N0. 2 (1951): MAP 27 isr'sa’ua' EAST or GREENWICH. 7'21/37,7' NORTH LEGEND HYDROGRAPHIC DATuu : APPROXIMATE LEVEL or LOWEST Low WATER 4544i" SW 4544lllSE 4544IISW ROADS BLACK NUMBERED LINES INDICATE THE 1.000 METER UNIVERSAL TRANSVERSE MAP 23 MAP 25 MAP 28 Ail weather MERCATOR GRID. ZONE 56. INTERNATIONAL SPHEROID hard Surface, two or more lanes wide None Built-up area W, None THE LAST THREE News of THE GRID NUMBERS ARE ONITTED I I n I l I d N no Church School Cemetery 1 I 1079517 5" 4543 IV Nw 4543 N NE 4543 1 NW OSE 0 l 5 race, W0 OI more 61165 W! e O i I . . . u 1 1g u MAP 24 MAP 26 MAP 29 hard surface, one lane wide NONE Limit of danger line; Submerged reel m I In! r. I 11 None Wk:Sk,E d 4°45’ Dose 0' lg mm one ans m e m u" an mm 0'10’ OR GRID ZONE DESIGNATION To GIVE A STANDARD REFERENCE 0N COMPILATION METHODS Fair or dry weather, loose surface, two or more lanes WIdE Sunken rocks, Foreshore flats 0R 5‘ “”5 THIS SHEET To NEAREST 100 METERS Photo-stereo Map Fan 01 dry weather, loose surface, one lane wide 1 1 a: :: Rocks bare or awash; Reel 3 MILS 100va M. SQUARE IDENTIFICATION SAMPLE palm; x 112 W GLOSSARY . - — Oror en anchorage Cari track, irail __.__-- Depth Curves and In Falhoms 1. Read "my; .denn'yin‘ 100,000 men, LP A. 1255,180, USHO Chart 6049. 1944 (reliability good). Unun en cape point _ square in w ich the o M has: , r 5‘3”“ “We “’"md' “we "m +'_'_ Reservon: Darn; Ditch 2. Locale firstVERTlCApL'grid line to LEFT or Aer'a' photography: MY 1945' Standard gauge railroad, double track point and read LARGE figures labeling the L . 2’6” Salt evaporator: line either in the top or bottom margin, or Narrow gauge railroad, Single iraclr —r—"-‘Tv— APPROXIMATE MEAN DECLINATION 1955 aniheimeiiseil: 53 . . 2’s ’ FOR CENTER OF SHEET Estimate tenths from grid line to pornt: 5 Narrow gauge railroad, double or multiple traCIi —H'-—“'—‘n— Rice Paddy; Marsh ANNUAL NAGNETIC CHANGE l’ EASTERLr 3. Locaielirst HORIZONTAL and line BELOW P I , I /r/ . . ‘ point and read LARGE figures labeling the ower ransmissmn 1112 W, ...... .. Ute diagram only lo oblarn ancaI values. line either In the Ielt or “KM margin. or Spot elevation in meters. Checked Unchecked " M6 X77.5 Nipa; ° 7° “WWW mafle'lc "0"“ "Ma conned "'9 ”we“ "‘9 SMALLER "W” 9”" ““m" l'“ “““1 13 V . I . , “P" sou”! ed [file and number; these are I!" finding Estimate tenths from grid line to pornt: 4 Wall; Levee' CIIII [A P'V° porn °" ”'9 99 0 map the full coordinates. Use ONLY the V V “we, Woods; Scrub with lhe valve of lbe angle hem-on GRID LARGER IIKMES of the grid number; SAMPLE REFERENCE: ”3535134 0 NORTH and MAGNETIC NORTH, '13 pIo'led on example: 8 000 ll reporting beyond 18° in any direction, (L6 prelix (End Zone Desrgnation, as: 56NLP535134 TO L N E, CARO LIN E lSLAN DS Waterwheel ol mill; Located obiect Prinupal navrgaiion light oi lighthouse; Anchorage __ * \1/ iropical grass; Coconut grove the degree scale 01 fine norlh edge of "n mop. 1958 TRUK ISLANDS Military Geology of Truk islands 47’30’ 368 369 CAROLINE ISLANDS 125 000 A . \ ,, 0° 20 30 4° 5° 6° 70 MAP 27 Avenues of Approach and ' l i l l I ‘ - I I..1,r.i,-111..-Ltl-.111 ELJ Cross country Movement 151-4700" 366 4730' 367 368 369 370 371 50mm "73 374 37F) 52/30i 376 377 378 379 1.515431% 7-321001 . . \7 77 1; l I I 7132/00" l n, 27 l Ix, I is. I i--- I I ’ I ‘r 22 29 /"\ l \O\ i I I ”I 3 I 30 I V I, ,’ 3 \I, I Uncovers l footie ' I I // Z \l I ”’3' I 9 I AVENUES OF APPROACH AND SUITABILITY FOR I .32. I I ‘ I I I I I I - / I, // I I l I , 1 “\ I ~— I 17 . r 34 , l \ l 22 \ I i R SS-C UNTRY MOVEMENT MAP TRUK lSLAN I e \ ‘ I I ‘ ‘ ‘ I I .\ X . \ / i I 24 -- 7 I. x . i 1 1M x . , I \ 5 \\ i I I 5 j 77// I ; Suitability terms, in order of decreasing suitability, are: excellent, good, fair, poor, and unsuitable. CCM «\ i' I I 36 I “"3” 5 x' 39 I 31 28 evaluation based on the jeep. Airborne operations evaluations based primarily on capabilities of 0-119 I , \‘x A77 // I I cm" I I “r“ ‘3“ I con" 3 8 . 832 and H-19. - ' . . 32 ..... .. 5+ _- - 3 I .. 32 l i Suitability for Suitability for Summary of Conditions {2; I ‘ 1 Landing beaches Assault . 7 Unit Vehicular Foot—troop Terrain description : ; aircraft Arrdrop Helicopters movement movement Assault aircraft Airdrop Helicopters Vehicular movement FOOt’tl’OOP movement I ‘ 30 (See Amphibious Airfield runways on fill. Only Moen airfield is in opera- Moen Airfield presently in use. Generally good; trees a hazard Moen Airfield excellent; aban- Concrete runways at abandoned airfields I I Operations tion (1955); crushed coral surface. Concrete runways Abandoned fields need minor on abandoned fields. Surround- doned fields good to fair. broken and, in places, under a few inches ,I I 1 chapter for GOOD TO GOOD TO EXCELLENT EXCELLENT EXCELLENT of abandoned fields (Moen. Eten, and Param) are repairs and some clearing. ing areas marshy. Coconut trees a local hazard. of water. Surrounding areas marshy. I data on FAIR FAIR T0 FAIR broken and in places have sagged below water table: , 35 i ‘ beaches) coconut groves grow on some runways. I , I 36 I l Fill, 0 to 4 feet high-tide elevation. generally level and Rough ground and scattered Numerous sites; coconut trees. bomb craters, and local Generally good traction; local wet areas; A I 7 7 77 I7 7 7 g m} 831 m———~— ‘ firm. Local marshy areas and unfilled bomb craters. trees prohibit assault aircraft marshes are hazards. Assembly and exit generally fair. unfilled bomb craters especially near airfields. G II t . t d DI ' ’ ’ ' " ‘ I” " ' ‘ an UNSUITABLE GOOD TO GOOD TO GOOD TO EXCELLENT Grass, brush, and cocount trees, singly and in combina- landings. Filling bomb craters Coconut trees probably no restriction to jeep enetraLy ulnres "Che ”with : POOR POOR POOR TO FAIR tion. and ,local wet places and clear- movement. Tell” ‘ or: y mars y areas wr ., I i ing trees would probably provide a swor grass. __, indicates swept depth area in feet I some site. : I : 52%: Beach suitable Sand beaches. mostly less than 20 feet wide, and The small size of beaches and the numerous coconut Some small sites; beaches Beaches narrow at high tide; good traf- I I for all types adjacent sandy areas separated from beaches by 1-foot- trees generally prohibit airdrops and assault aircraft narrow and coconut trees ficability; gradient about 1:10. Coconut trees 7—7 78 7‘9 66 of landing UNSUlTABLE UNSUlTABLE GOOD T0 :' GOOD EXCELLENT high SCBI’PS- Well drained. Sandy areas covered by landings. Clearing of trees might enable small-scale common. probably no restriction to jeep movement but I; ' , .. ‘~ craft. UNSU'TABLE COCOHUI trees 20 to 25 feet apart. airdrops. would hinder larger vehicles. I 34 I l Predominantly grassland with scattered brush and Steep slopes, scattered trees, Scattered sites; trenches and Scattered sites; trees, boulders, Boulders, bedrock pinnacles, and trenches Tall grass impedes movement ”'3' trees; grass on uplands 3 to 8 feet high; slopes less and rough ground prohibit boulders may make assembly and trenches are hazards. local hindrance. Clay soil has good traction and conceals trenches and fox- 1 i 35 UNSUITABLE FAIR TO FAIR TO FAIR TO GOOD TO than 30%. Some bare bedrock; boulders and WW II assault aircraft landings. difficult; generally poor exit; Generally partly restricted when dry, slippery when wet. Dense grass holes. _30 i .. 11:50 830 POOR POOR POOR POOR trenches common. somewhat restricted approaches. conceals hazards and may impede some I approaches. wheeled vehicles. I Beach suitable Forest, mostly coconut-breadfruit, of various densities, Dense forest prohibits most airborne operations. Possibly a few small helicopter Moderately dense forest has heavy under- Moderately forested areas have sand 32,, shens I for shallow-draft in places a 40-foot-high closed canopy. Slopes less sites and hovering operations are locally feasible. growth;although dense forest has little under- dense undergrowth; dense forest I I landing craft. POOR T0 GOOD TO than 30%- growth, closely spaced trees do not permit has sparse undergrowth. I I 31 UNSUITABLE UNSUITABLE UNSUITABLE UNSU'TABLE POOR vehicular movement. Clay soil slippery when coral wet. I / . 31 , . ,i ‘ Areas of mangrove swamp, fresh-water marsh, and Steep slopes, dense forest, or low wet swamps and marshes prohibit airborne Steep slopes and rock cliffs stop movement 0n uplands direction restricted ”"d . I I I 30:00,; 28 densely forested steep (over 30% Slope) terrain. Operations. on uplands; mucky bottoms and dense man- by escarpments and thick tangl- /i__ — POOR TO ‘ - ‘ UNSUlTABLE UNSUITABLE UNSUlTABLE UNSUlTABLE UNSU TA grove stop movement in swamps and mar ed vrn'es may stop movement. {I I BLE shes. Men srnk waist deep Into swamp , \ 27 7 829 bottoms, about a foot into . 29 . . , .. > . ' \‘g‘ ‘23 marshes. 19 30 \ ,7—5‘-‘ TRUST TERRITORY OF THE PACIFIC ISLANDS 0338, g; 22 (<1) I, U.S.A. ADMINISTRATING AUTHOR TY) 3 , i315 \ 7X I \._, ’ 28 l l 29 T 28 I 22 shagls i d1 1 I 3 -. -. no 828 2. 28 . < . -..-- ~ 3,: .. I/ 10 ‘1‘ 29 sand, \\\ ,-\ L4§ I: cogal I \\7\\7 I \\ l/ rvo \\/ \\7777 7 ‘\\L 6 II 8 I I \& 29 I 3) x .2/ 28 , r 27 18 I 2. TRUK ‘ISLANDSr shells // I 25 --_ -3"--- -.-., .. - 23f)“ 827 27 . - 7 , I 29 29' 29 LA indicates swept depti area in feet 29 29 '27,) , 826 26 - ..__- .6 30 77_\ 1%: /“K /’ \I as 67 68 69 70 I I 23 I 30 29 I 5 I I, 1 // 29 23 \\ co‘ral 7// 8")" 825 \ V K 25 m L?) 19 28 27 21 ' 2 824000m.N7 24 23 -. T' w y 7' . . . - _ l 4 l 5 VA , ,0 v , sigh . - eewm /@ l 3 W . ' W “my. . , I e r W , , MW‘ . , 7=27Iool ' 1’ cm '. l rig {161 I £2317" “ 1.. SI? ’30 3;}2 151°47’00” 366 000mg 367 W856 5 Edition 2-AMS (AFFE) Prepared under the direction of the Engineer, Hq AFFE 8A, by the US, Army Map Service, Far East. Compiled in 1957 by photogrammetric (multiplex) methods. Chart 6048, 1944. Horizontal and vertical control established by Corps of Engineers, 1951. literated in accordance with rules of the U.S. Board on Geographic Names. Coastal hydrogra phy compiled from USHO Names trans- Major roads are classified by reconnaissance by the 64th Engineer Battalion (Base Topographic), 1952; other roads are classified from source maps and aerial photography and are not verified by reconnaissance. Coastal vegetation are clas- sified by reconnaissance by Military Geology Branch, intelligence Division, Office of the Engineer. Hq AFFE/SA, with personnel of the U.S. Geological Survey, 1955. Map not field checked. Airborne Operation and cross-country movement compilation based on field observations 1954- 1955 by Military Geology Branch, intelligence Division, Office of the Engineer, Hq, U.S. Army Japan with personnel of the us. Geological Survey. LEGEND ROAM All weather hard surlace, two or more lanes wide None Burlt up area None loose or light surlace. two or more lanes wrde . None Church, School, Cemetery . I 109'“ 1 hard surface, one lane wide None Limit of danger line, Submerged reel . loose or light. suilace, one lane Wide None Wreck Sunken, Exposed H ‘ijd u fair or dry weather, loose surface, two or more lanes wide :.e....«-:::. .7 Sunken rocks, Foreshore llals * SW ,4 fair or dry weather, loose surlace, one lane wide : : : r: . . Rocks baie 0i awash: Reel ’ " I“; . _ .2 | Cart track. trail . . . . .. . .-..-.. .. ____-_ Depth Curves and Soundings In Fathom: /d’ I? -—O—t——t—- , Standard gauge railroad, Single track -.... . , meo”; Darn, Ditch CJV Standard gauge railroad, double traclr . fit‘fit—dt— ’ a’e” Salt evaporator: Naiiow gauge railroad, single track -.- -. —T—‘—v—- ~ . a'a” ' -'I Narrow gauge railroad, double or multrple track —w——“—w— Rice Paddy. Marsh 77 " 7 Power transmissron line . .......... / I _ Spot elevation to meters, Checked, Unchecked . , . ‘Jro "IbG N'paI Mangrove ' ‘5‘ b; Wall; Levee; CIIll ...-. .. __m —I 7. A Woods, Scrub -J .......-.1 Waterwheel of mill; located 0breci . . 1? OIOWI f‘AM'I i...“ a! t. , Pnncioal navrgation light ol lighthouse, Anchorage -. )I‘ \Z/ Tropical grass, Coconut grove . I_.-_-I L34 lNautical Mile 370 371 3173 14 ”ale 125‘HIO 1, 777 ii: 7 C tStatute Mile 1000 500 o T 7 - 1 H 73-4 F1 :--1I L—‘I , ____ ’ T T :“ L‘~———‘.::':7::::T:T::___._T::fl 1000 500 CI 1 ‘0 WIC'O Yards i_,:———«1 P—«i i——-—4 i— 1—-—} " ...- _ j. - _ ' 1 1' o CONTOUR INTERVAL IO METERS VERTICAL LIATIIM MEAN SEA LEVEL 0°09’ on 3 MlLS 84 MILS GN ~.. 7 4'45’ on I , t APPROXIMATE MEAN UECLINATlON 1355 FOR CENTER OF SHEET ANNUAL MAGNETIC CHANGE l' [ASTERLY Una diagram only to obtain numerical valves. Yo determine magnetic north lino. connect the pivol point ”P" on the wulb edge of the map WT"! "to value of the angle between GRID NORTH and MAGNETIC NORTH, on plofiod on the dean. scale 0! the nor”: edge of the map. TRANSVERSE MERCATOR PROJECTION HORIZONTAL DATUM IS BASED ON THE ASTRONOMIC STATION NO 2 IIlQSl) 15:“53’14 :1' EAST OF GREENWECH. 7“21/37,7” NORTH HYDROGRAPH 'iC DATUM APPROXIMATE LEVEL OF LOWEST LOW WATER BLACK NUMBERED LINES ENDICATE THE 1000 METER UNIVERSAL TRANSVERSE MERCATOR GRlD, ZONE 56. INTERNATIONAL SPHEROID THE LAST THREE DIGITS OF THE GRID NUMBERS ARE OMITTED GRID ZONE DESIGNAHON' II 10 GIVE A STANDARD REFERENCE ON 6N " THIS sent TO NEAREST 100 METER: 100.000 M. SQUARE Ioturiricusnn II swrrt Pom s SllNKEN ROCK I, ! II 1. Read letters Identifying l00.00(l meter I —. l l 1 square iii which tn: point he: Lt’ I I I I 2 Locateflisl VERTICAL and line to 1m of . I LP I I pnrni and read LARGE figures labeling the 1 I I 7 1 I line miner in the top or bottom margin, or I ,' I I j on the ims Ilsell. I 76 , r , i ishmate tenths lrorrr gird line to porn: I 4I 1-... -3- __ . - .I I .1 local? iirsi hORIZONTAl gm line arrow I I, I‘ point and read IARGE IlRUlPS labeling lhe I _____._.__-.W-,_..fiIi lire Cilllll in the left or righl margin, of f IGNORE The SMALLER ligures of any , I on the line rtseIl. I 28 grid number. these are far Mama I Estimatetenlhsliom gridlnetc no nl‘ I 3 me roi: coordinates Use oNLr the I I LARGER lrguies of the grid number; I_ SAMPLE REFERENCE [P763 ”mm” 824 000 E II reporting beyond 15“ m, m dlfefiirun, I — 1 will Grid lone Desrination as I58NLI’7643831I 1958 52/30” 376 Interpretations for airborne operations and cross-country movement by Richard L. Hay, 1954-1955. US. ARMY MAP SERVICE, FAR EAST COVERAGE DIAGRAM INDEX TO ADJOINING SHEETS 4544 ll NW MAP 27 4544 III SW 4544 lll SE 4544 ll SW MAP 23 MAP 25 MAP 28 77 4543 IV NW 4543 N NE 4543 l NW his. so MAP 24 MAP 26 MAP 29 COMPILATION METHODS Photo-stereo Photo-planimatric Map V ' , . r’ s\\\\\\\\\\\ {:3 1-7”“1.-- etossm . A. USHO Chart 6048, 1944 (reliability good). ngrne2'1'7:”""vhi'TWT'TTTT“ """T’TTT:‘GDG. poignt Aerial photography: Feb, Juiy 1946. MOEN NW, CAROLINE ISLANDS he. on n E? “.51 Military Geology of Truk Islands 20 30 4o 50 6° 70 MAP 28 Avenues of Approach and . Lu l , I l l LI 1 I Cross-country Movement ._J_ “JAIL; 1. ,1. 1. .ML .11 ,. 52/30” 376 , , ,. . , 3 or.) 47 w 369 370 371 50/00” 372 373 374 Z7 M . . .. union" 5 I f l I I 22 l 28 l l l/ I l AVENUES OF APPROACH AND SUITABILITY FOR 1“ CROSS-COUNTRY MOVEMENT MAP, TRUK ISLANDS , ~~~~~~~~~~~~~~ v NEWACHO 1’3”, “.7, Suitability terms, in order of decreasing suitability, are: excellent, good, fair, poor, and unsuitable. CCM _. H . I \4 3 , evaluation based on the jeep. Airborne operations evaluations based primarily on capabilities of 0-119 17 6 l \Jfluq 9,1/1' and H-19. sanZa/I/ Nukuisei /\/ I /./ ‘ / 34 Suitability for Suitability for , ’ Landing beaches Assault . . Unit Vehicular Foot-troop Terrain description ’ 3 ’ aircraft Airdrop Helicopters movement movement I 2‘ J; , I 3 UOLA ROAD (#— ..... -- .-_ (See Amphibious Airfield runways on fill. Only Moen airfield is in opera- ll (OROR EN NEPUNG) ”J” I Operations tion (1955); crushed coral surface. Concrete runways “’1; I cha ter for GOOD TO GOOD TO EXCELLENT of abandoned fields (Moen, Eten, and Param) are I dat: on FAIR FAIR T0 FAIR EXCELLENT EXCELLENT broken and in places have sagged below water table: I /, beaches) coconut groves grow on some runways. 31 I / 822 -. ., , .. . .. .- fl . . f7 _ ”2Z7 co 3 I ,/ Fill, O to 4 feet high-tide elevation, generally level and ”or firm. Local marshy areas and unfilled bomb craters. / x I UNSU GOOD TO GOOD TO GOOD TO EXCELLENT Grass, brush, and cocount trees, singly and in combina- // l ”ABLE POOR POOR POOR TO FAIR mm 5330 . 8 x// 79 é; Beach suitable Sand beaches, mostly less than 20 feet Wide, and // . for all types , , adjacent sandy areas separated from beaches by 1-foot- // of landing GOOD TO high scarps. Well drained. Sandy areas covered by // craft. UNSU'TABLE UNSUITABLE UNSUITABLE : GOOD EXCELLENT coconut trees 20 to 25 feet apart. // Cg?“ . who, Predominantly grassland with scattered brush and -. .I . . :2; Li: 7 E trees; grass on uplands 3 to 8 feet high; slopes less I UNSUITABLE FAIR T0 FAIR T0 FAIR T0 GOOD TO than 30%. Some bare bedrock; boulders and WW II POOR POOR POOR POOR trenches common. 3 31 I 30 Beach suitable Forest, mostly coconut-breadfruit, of various densities, Wm . for shallow-draft in places a 40-foot-high closed canopy. Slopes less I landin craft. POOR TO GOOD TO than 30%_ I g UNSUITABLE UNSUITABLE UNSUITABLE UNSUITABLE POOR l I f. . 7 ‘ -/ 2.1.. ”.3 l Areas of mangrove swamp, fresh-water marsh, and l densely forested steep (over 30% slope) terrain. I / 13 83,73 UNSUITABLE UNSUITABLE UNSUITABLE ‘ UNSUITABLE POOR To i ’ s ‘93 '1;)r:‘)i)/r UNSUITABLE l I ll C Ole - ~ 23 \ ora .f {and \ v3 L52 5 \ N. TRUK L'AGOON l \ I 15 Ti I coral Summary of Conditions I Unit \ § Assault aircraft Al'dFOP Helicopters Vehicular movement Foot-troop movement 'I 24 l to . ‘ Moen Airfield presently in use. Generally good; trees a hazard Moen Airfield excellent; aban- Concrete runways at abandoned airfields I I . // "'3' 23 I Abandoned fields need minor on abandoned fields. Surround- doned fields good to fair. broken and, in places, under a few inches ‘ nun’en/Neailwo‘ i ‘ repairs and some clearing. ing areas marshy. Coconut trees a local hazard. of water. Surrounding areas marshy. ZQIIJ * . I . .s 819 23c . ”p N. - . I l (>2; ,1,” l 33 ‘Ez/ 13 /,/EE I coral fZ/flz ROUEh ground and scattered Numerous sites; coconut trees, bomb craters, and local Generally good traction; local wet areas; 1 .2 r trees prohibit assault aircraft marshes are hazards. Assembl and exit generally fair. unfilled bomb craters especially near airfields. Generally unrestricted move- l 21% . . . v . . . , 9/ ”4 landings. F'll'ng bomb craters Coconut trees probably no restriction to Jeep ment. Locally marshy areas with I /Z//; and local wet places and clear- movement. tall swordgrass. 29 I /////// ing trees would probably provide 32 ' ol// - / some Site. ' The small size of beaches and the numerous coconut Some small sites; beaches Beaches narrow at high tide; good traf- trees generally prohibit airdrops and assault aircraft narrow and coconut trees ficability; gradient about 1:10. Coconut trees A ' landings. Clearing of trees might enable small-scale common. probably no restriction to jeep movement but ' 3' airdrops. would hinder larger vehicles. 322 R" ‘ “* .- " \ ” ‘s’an‘ei" “‘ ”‘ ”l8 :8 . \ x $33. Steep slopes, scattered trees, Scattered sites; trenches and Scattered sites; trees, boulders, Boulders, bedrock pinnacles, and trenches Tall grass impedes movement I 15 \\ \\ 22 s and rough ground prohibit boulders may make assembly and trenches are hazards. local hindrance. Clay soil has good traction and conceals trenches and fox- l 16 I 18 \\ \\ ’ assault aircraft landings. difficult; generally poor exit; Generally partly restricted when dry, slippery when wet. Dense grass holes. I \\\\\ somewhat restricted approaches. conceals hazards and may impede some T R U K I I S L A I N D S \ \\ approaches. wheeled vehicles. & X \ \ ____________________________________ x \ ______________________ 17 X \ 23 Dense forest prohibits most airborne operations. Possibly a few small helicopter Moderately dense forest has heavy under~ Moderately forested areas have TRUST TE I RITORY OF THE PACIFIC lSl'ANDS “'3' \\ \\ sites and hovering operations are locally feasible. growth; although dense forest has little under~ dense undergrowth; dense forest (U.SIA. ADMINISTRATING AUTHORITY). \\ \\ growth, closely spaced trees do not permit has sparse undergrowth. I l7 l \\ \\ vehicular movement. Clay soil slippery when I I Q/\ wet. I . 4:: \\ 18 to x . . . . 7M- .-._.--..... .i.- - . .17... \ \ \ , x“ . . _.__‘ mug; ' ' 817 Steep slopes, dense forest. or low wet swamps and marshes prohibit airborne Steep slopes and FUCK Cllffs stop movement 0n uplands direction restricted 1 l8 \ ‘z 18 \ WW AA—s . operations. on uplands; mucky bottoms and dense man- by escarpments and thick tangl- 1 . . , ., , . grove stop movement in swamps and mar- ed vines may stop movement. K AUG P9!" shes. Men sink waist deep into swamp 21 ,‘ /EEE\\ 55 COral' . bottoms, about a foot into I / ‘r * J ' , i 8 ' 3+“ marshes. \ r~\ “ i \\ l // LE - i7 x—a 6b 6 7 68 69 7O 7 72 7 E I I 13 15 indicates swept depth area in feet I \. .. 81(‘ w ‘ r" —« .l. 1 “lo I 2" 3 gin/(54 , %¢O cor/a] //»Coral ’ 22".},1!” ,ggJ 21’30” ‘C‘~\ /// ~ (i /—\TEE\\ E‘c097‘3I z. 1' I .’- I} . r E 815 8 (WOULN J I o +I+I .- ‘3 . . . . 7’ 15 . 6. . 3 . - _. i IQJ 5 ‘ , , .. \M o t, ‘c g, ’ \ \l 13.- ~~~~~~ .l I E - \ co a ,. V \\ \—/\ 11 ‘~ I ETEN ANCHORAGE/ . , - \J \ N 20 l l 6;? E . ' » \ ‘ 1 ° _ , ,. Coral/r \ I , L551 . Coral reel 23/ aQISOR EN UNUAVG I \\\\ fl \ ""11" E ry? 17 _’/\:®) 00'3 l/l 7...,00, . .. \J’ $5 ’lh F‘fi ': “We; \ i 7 [5. J “as? /%M 33 °r / 7.22.00, ' l . , . r . , Ca - l51 47 00’ 366000m'E. 47 3%” 3.07 368 369 370 371 50’00” 372 373 374 P 5230" 376 37’] 379 151 54/30” 375 W856 5 Scale 1:25.000 . . l u n - Edmon Z'AMS (AL-FE) 1 5 0 IStatute Mile Interpretations for airborne operations and cross-country movement by U.S. ARMY MAP SERVICE, FAR EAST - 57-041 - R-ls - 1/59 - 3. 4c l—l - Richard L. Hay, 1954-1955. Prepared under the direction of the Engineer, Hq AFFE,"8A, by the U.S. Army Map Service, Far East. 1090 500 l_? 103° 200 MEWS Compiled in 1957 by photogrammetric (multiplex) methods. Coastal hydrography compiled from USHO 1000 I 5010 l i 0 1000 2000 Yards Charts 6048, 6050. 1944. Horizontal and vertical control established by Corps of Engineers, 1951. Names H H H H H transliterated in accordance with rules of the U.S. Board on Geographic Names. Major roads are classi- 1 0 lNautical Mile fied by reconnaissance by the 64th Engineer Battalion (Base Topographic), 1952 and reclassified from aerial photography dated 1955; other roads are classified from source maps and aerial photography and are not verified by reconnaissance. Coastal vegetation are classified by reconnaissance by Military Geology Branch, Intelligence Division, Office of the Engineer, Hq AFFE/BA, with personnel of the U.S. Geological Survey, 1955. Map not field checked. Airborne operation and cross-country movement compilation based on field observations 1954- 1955 by Military Geology Branch, Intelligence Division, Office of the Engineer, Hq, U.S. Army Japan with personnel of the U.S. Geological Survey. LEGEND ROADS All weather : LANES , ”m— hard surlace, two or more lanes wide BurIt-up area ___.___i7._ TI? loose or light surface, two or more lanes wide E LAN“ Church; School; Cemetery {CPD} 4 I hard surlace, one lane wide # Limit ol danger line; Submerged reel loose or light surface, one lane wide ___._w__. Wreck: Sunken; Exposed i Fair or dry weather, loose suilace, two or more lanes wide : Sunken rocks; foreshore flats Fair or dry weather, loose surface, one lane wide Rocks bare or awash; Reel -_,_,._.__ Cari track; trail _._-_____— ______ —i—i——i— Depth Curves and Soundings in Fathoms , Standard gauge railroad, single track Reservoir Dam‘ Ditch Standard gauge railroad, double track 2/5" Sali evaporalors Narrow gauge railroad. single track ,1.” Narrow gauge railroad, double or multiple track Rice Paddy; Marsh Power transmission line “A . ._...-c./ Spot elevation in meters: Checked; Unchecked AH. x res ”/55 Nipa; Mangrove w' Wall; Levee; Cliff w _m§,‘§ fl Woods; Scrub Waierwheel of mill; Located object _ ¢ oTOW Principal navigation light of lighthouse; Anchorage _ * 3/ Tropical grass; Coconut grove __ COVERAGE DIAGRAM INDEX TO ADJOINING SHEETS CONTOUR INTERVAL IO METERS \\\Q\‘ \\\\\§§s\\;§w - u VERTICAL DATUM: MEAN SEA LEVEL \ \§§Q‘Q\§E L 4544 ll NW {‘le MAP 27 TRANSVERSE MERCATOR PROJECTION \ {\{x §‘~\ . - HORIZONTAL DATUM IS BASED ON THE ASTRONOMIC STATION N0. 2 (l951): E \ \ \\ l51'53’34.3' EAST OF GREENWICH. 7'Zl’37.7’ NORTH . I 4544 III SW 4544 III SE 4544 ll SW HYDROGRAPHIC DATUM: APPROXIMATE LEVEL OF LOWEST LOW WATER MAP 23 MAP 25 MAP 28 BLACK NUMBERED LINES INDICATE THE 1.000 METER UNIVERSAL TRANSVERSE MERCATOR GRID, ZONE 56. INTERNATIONAL SPHEROID the LAST THREE DIGITS or THE anio uuuaens ARE cum-so 4543 IV NW 4543 N NE 4543 l NW 5N MAP 24 MAP 26 MAP 29 0.09, 4'45! Photo-stereo Photo-planimetric Map GRID lONE DESIGNATION: TO GIVE A STANDARD REFERENCE 0N L 0* 0" THIS sum to NEAREST 100 METERS \\\\\\\\\\\\ . .. . GLOSSARY 3 “L5 54 MlLS 100.000 M. SQUARE IDENTIFICATION SAMPLE POINT: ; SCHOOL A. USHO Chart 5048 19“ (reliability 800d) Sam on L If: ' . . . ‘ ror en - LRend imus identifying 100,000 mm 3- USHO Chart 5050' 19“ (reliability good). Unun en cape, point squlrl in which the paint has: LP Aerial photography: Feb, July 1946. 2. Locate first VERTICAL grid line to LEFT of point and rend LARGE figures labeling the LP line either in the top or bottom margin, or APPROXIMATE MEAN DECLINATION i955 onihelineiisoii: 78 FOR CENTER OF SHEET Estimate lonlhs from [rid line to point: 1 ANNUAL MAGNETIC CHANGE i' EASTERLV 3. LouiefirstliORlZONTAL gridline BELOW . . . point and rud LARGE iilures labeling the Use diagram only lo obfarn numerical values. lino either In the left or right "mil". or To determine mognafic north line, conned the "mo“ the SMALLER figures I" any 0" "'9 ll". "5'": 16 pivol pain! "P" on the south edge of the map {gzd'::'::::alg::: 'J:"‘3N€c‘I:: Estimate tenths from [rid lineto point: 8 with the value of lhe angle between GRID LARGER figures of the grid numb"; SAMPLE REFERENCE: LP781168 NORTH and MAGNETIC NORTH, as ploh‘ed on ""“P'” g 000 ii "pom... beyond 13- in any dirociion,J the degree scale a! the north edge of the map. J._5 ”Em 6M 1°". Dnignltion, u: SGNLP781168 M 0 EN SW, CARO LI N E '8 LAN DS 1958 TRUK ISLANDS U M A N N AA 20 3o 40 50 60 70 I l I IMJLLLI’JLJJJ Military Geology of Truk Islands MAP 29 Avenues of Approach and Cross~country Movement ‘ f" . LAROLIN: ISLANDS 125,000 131°47'00” 365 47/30” 367 369 370 52/301’376 379 151°54’30" 7'22LO” ~»- . » , 7‘2200” ‘Q ,. . . - L4_6‘ 10 17 L0 23 1/ 23 11318 / Coral ' . L / J 1 R0 ENU UNO ’I/ 31 7 / 4 4 “gym ANCHORAGE” ,’ , 4 as 31 - ,x’ ’ “““““ K 49 / 19 "7 : C k l b0 “\H // 17 coral 3, '. ; A ; * *UncoverLl foot 2 figs, ‘\ l 814 53L! "'5 K , (11 a H, ‘4 : ,/ ‘ > 1 I (,\ \ * C Q‘Q I [flavors 1 foot A/ E; J» 54A A12 "A . Unu. A ~ / . "_/ NFANIP l 2.. I 12 .m [\ F' A \ ‘ l \\ K 1’ \ coral corn 4} \K . \4 8 \ z o/ - \28 Coral "cc ‘ O\ \ 12 -- nun\ I?“ . m J 1‘ 7 W ' ,5 A / fl ‘ A , , P 19 313 813 J / ' I 1 Aft-"Whoevers 3 fEeL ,' \\ Uncovers [1—, 00'“ ~ \5/ AVENUES OF APPROACH AND SUITABILITY FOR 64 15 1 AA. A A _ A: 10919.3 . 18 I / . coral 5'“ R2,} mg l ““““ I] of ‘C‘~i’j L_\ Vsand,\ 3 33¢; ‘ 15 “q 3 \X r ‘ ’ ‘T A lr- \ 9 44 . CROSS-COUNTRY MOVEMENT MAP TRUK ISLANDS WA... . AAW / 9 x 3 t “n )3 I I v— If+®éf§fif051 \ l _ Em \ 5 I comiCPfili’ p (r, 19 ° 10 Suitability terms, in order of decreasing suitability, are: excellent, good, fair, poor, and unsuitable. CCM corll 75 . 79 66 °’ evaluation based on the jeep. Airborne operations evaluations based primarily on capabilities of C-119 15 5: t/ . ‘ I and H-19. sand few" 19 20 I Suitability for Suitability for Summary of Conditions Landing beaches Assault , . Unit vehicular Foot-troop Terrain description -—‘* 812 812 aircraft Airdrop Helicopters movement movement Assault aircraft Airdrop Helicopters Vehicular movement Foot-troop movement (See Amphibious Airfield runways on fill. Only Moen airfield is in opera- Moen Airfield presently in use. Generally good; trees a hazard Moen Airfield excellent; aban- Concrete runways at abandoned airfields Operations tion (1955): 0115th coral Surface- Concrete runways Abandoned fields need minor on abandoned fields. Surround doned fields good to fair. broken and, in places, under a few inches chapter for GOOD TO GOOD TO EXCELLENT EXCELLENT EXCELLENT of abandoned fields (Moen, Eten, and Param) are repairs and some clearing. ing areas marshy. Coconut trees a local hazard. of water. Surrounding areas marshy. data on FAIR FAIR TO FAIR broken and in places have sagged below water table; Vt” beaches) coconut groves grow on some runways. Fill, 0 to 4 feet high-tide elevation, generally level and Rough ground and scattered Numerous sites; coconut trees, bomb craters, and local Generally good traction; local wet areas; firm. Local marshy areas and unfilled bomb craters. trees prohibit assault aircraft marshes are hazards. Assembly and exit generally fair. unfilled bomb craters especially near airfields. Generally unrestricted move- GOOD TO GOOD TO EXCELLENT Grass, brush, and cocount trees, singly and in combina- landings. Filling bomb craters Coconut trees probably no restriction to jeep t L H h areas with UNSUITABLE POOR POOR To FAIR . men. oca ymars y tron. and local wet places and clear- movement. , . tall swordgrass. I I Ing trees would probably provrde 6 / some site. / g: 811 811 s, s Beach suitable Sand beaches, mostly less than 20 feet wide, and The small size of beaches and the numerous coconut Some small sites; beaches Beaches narrow at high tide; good traf. .\ / for all types adjacent sandy areas separated from beaches by 1-foot- trees generally prohibit airdrops and assault aircraft narrow and coconut trees ficability; gradient about 1:10. Coconut trees \" 3 of landing GOOD TO 1- high scarps. Well drained. Sandy areas covered by landings. Clearing of trees might enable small-scale common. probably no restriction to jeep movement but ZOIOOV long 15 ( craft. UNSUITABLE UNSUITABLE UNSUITABLE .' GOOD EXCELLENT coconut trees 20 to 25 feet apart. airdrops. would hinder larger vehicles. t: 20'00” ”24, AAAA Predominantly grassland with scattered brush and Steep slopes, scattered trees, Scattered sites; trenches and Scattered sites; trees, boulders, Boulders, bedrock pinnacles, and trenches Tall grass impedes movement ,,/*"[ trees; grass on uplands 3 to 8 feet high; slopes less and rough ground prohibit boulders may make assembly and trenches are hazards. local hindrance. Clay soil has good traction and conceals trenches and fox- “ coral” UNSUITABLE FAIR TO FAIR TO FAIR TO GOOD TO than 30%. Some bare bedrock; boulders and WW II assault aircraft landings. difficult: generally poor exit; Generally partly restricted when dry, slippery when wet. Dense grass holes. I POOR POOR POOR POOR trenches common. somewhat restricted approaches. conceals hazards and may impede some approaches. wheeled vehicles. 1.5.51 (/70 [IQ Beach suitable Forest, mostly coconut-breadfruit, of various densities, 12 Dense forest prohibits most airborne operations. Possibly a few small helicopter Moderately dense forest has heavy under- Moderately forested areas have 810 25 (r for shallow-draft in places a 40-foot-high closed canopy. slopes less 1 0 sites and hovering operations are locally feasible. growth;although dense forest has little under- dense undergrowth; dense forest —- 810 I landing craft. POOR T0 GOOD TO than 30%, .. .. .. growth, closely spaced trees do not permit has sparse undergrowth. I UNSUITABLE UNSUITABLE UNSUITABLE UNSUlTABLE POOR OROR EN KUKUWU vehicular movement. Clay soil slipper when 8 y [I 12 wet. I Areas of mangrove swamp, fresh-water marsh, and Steep slopes, dense forest, or low wet swamps and marshes prohibit airborne Steep slopes and rock cliffs stop movement On uplands direction restricted K 7 , densely forested steep (over 30% slope) terrain. operations. on uplands; mucky bottoms and dense man- by escarpments and thick tangl- “——”' ' POOR TO grove stop movement in swamps and mar- ed vines may stop movement. UNSUITABLE UNSUITABLE UNSUITABLE UNSUITABLE UNSUITABLE shes. Men sink waist deep into swamp 19 bottoms, about a foot into 30 1 13 marshes. 23 12 / A 30 , / A * l ' l// \l /L—-‘ // a / //,A~\z\ \\ 2—81 \ \\ 24 1 14 // I gig “I / _____ \ ’ // ‘/ 5} ‘I \\ ,’”1'\\\ 13 Uriun an Aranga, 35 309 809 I [r O 1 x r k a / \ coral / 29 \ ’ b2 3,} A 2 ‘A-cogaI/rl ‘ 52 ~,I \ “\o / \‘~——/’ 29 ‘l 24 1‘ co" " II 18 11 \e/ ‘\w// \\coral // 23 / 55 , v / \\ 111! ' I 29 A I. _ A ,2 s; x 23 fl _____ (12‘ \\ 25 28 /" ““412 22 £1 /23 \\ 30 "“ /.;4§. 28 / \\ 18 \x ’/,/l \ /,’ I \\ uim on Nepw'asu 12 I‘ 8 ’l / 21 1 \ 3 \z-// 22 I shells \ 24 13—3: \ /-—-z \ 4 36 29 A / —\‘ x x “'3' 29 ’/ 1 Unun on threng 63 o’I com 42 1 \\ Ag / r / ._, r 14 \ 31 [/5 \\/ [/1 34 , \, I\ cart. /, I, 13 28 I coral r ((1%) / I: As‘K/ \‘ \ 8 808 8 ’/ I 3:3: / / / d \ 08 I, 19 A 08 ’ \ 16 \ coral \ 30 29 / \ X I I Shall: shells // 15 \\ I \\ I 29 ,Il \\ 23 377 53’ 30” 378 379 151° 54’ 30” 31 33 I 24 \ 7"17’00" gab 7'17’00” 11 I /__‘¥‘\ shells [rI 1 \Q , \\ ‘53 \ \\\ 6'6 11,“ 2} 67 33 68 69 l 52 g / ‘A, Atkinl'slggd Unun o Nukanaix 18, ‘\ coral // l, / \: l ‘\ 805 ‘ _ ,.. L 305 core \‘~\__,_,/’/ , / l \\ 5‘3\6; \\ 21 L 3; 13 u an en,- ‘ NNUKANAP 1, 31 [I o Ne imokul 19 ‘, 32 / I, 29 l 24 /5 27 I -7 [I 24 807 807 a -- , .1 33 ,1 23 I @ ll 17 coralI 12 33 ;’ coral ,I l I l 804 804 I} '1‘ [SA 0 RACE 30 30, coral I I _ / 1 Ir 17r3or/ I cum /\J 17 30 I , 1 30/ 19 06 r d ~12 , 17 21 806 805000011“. 23 MT 4;) / mus \ a I, can: 5 // ' _ \ E \ ‘r\ \//I /~ / 16 00” — Faneu Island 16,00” \3‘ 34 35 ‘ I / \ \ 90”“ shells 37 11 ° \ shells / A‘ / VORIOR/EN SAPOUzi /// //l 8030mm. N. 803 / ,‘v I ' 4 ’ ’ I ° ‘ 5‘ ‘ 22 3‘ ' /’ o 9 I Coral 2 ‘ l I we / . 7'17Ioo” \ 1 7 17100” 151°47'00l' 355000m.E 47/30” 357 368 359 377mm. E. 53130” 378 379 151°54'30” 52/30” 375 379 151°54’30” “’855 5 Scale 125,000 Edition 2-AMS (AFFE) l . . . . 1 2 L o IStatute Mlle lnterpretatrons for airborne operations and cross-country movement by u.s. ARMY MAP SERVICE, FAR EAST - 57-041 - R—lS . 1/59 . 3.4c ‘ ‘ ‘ Richard L. Ha 1954-1955. Prepared under the direction of the Engineer, Hq AFFE,’8A, by the US. Army Map Service, Far East. 1000 500 0 1080 2000 Meters y’ Compiled in 1957 by photogrammetric (multrplex) methods. Coastal hydrography compiled from USHO I 1000 500 0 1006 Charts 6048, 6050, 1944. Horizontal and Vertical control established by Corps of Engineers, 1951. Names , H H r———-4 r-—-r H . 250500 Yards transliterated in accordance with rules of the u.s. Board on Geographic Names. Major roads are classi- 4 . fied by reconnaissance by the 64th Engineer Battalion (Base Topographic), 1952 and reclassified from 1 0 lNautrcal M'Ie aerial photography dated 1955; other roads are classified from source maps and aerial photography and k 1 ‘ I I r COVERAGE DIAGRAM INDEX TO ADJOIN'NG SHEETS are not verified by reconnaissance. Coastal vegetation are classified by reconnaissance by Military Geology u \\\\\\v ‘ . Branch, Intelligence Division, Office of the Engineer, Hq AFFE/SA, with personnel of the U.S. Geological CONTOUR INTERVAL IO METERS WITH SUPPLEMENTARY CONTOURS AT 5 METER INTERVALS “I W§ survey! 1955' Map "0‘ field Checked- VERTICAL DATUM: MEAN SEA LEVEL "‘\\ \ 4544 ll NW Airborne Operation and cross-country movement compilation based on field observations 1954. TRANSVERSE MERCATOR PROJECTION \ MAP 27 955 b " ch ntelli n ' ' ' , ‘ japan xltr'gzignfizflgfythgrzns 'GIsologiizl cseurBQcSIon Office Of the Engineer, Ho, ”'3‘ Army HORIZONTAL DATUM rs BASED ON THE ASTRONOMIC STATION No. 2 (l95l) ' I I 151'53/343” EAST or GREENWICH, 7'21/37.7” NORTH ‘ 4544 III SW 4544 III SE 4544 ll 5W LEGEND HYDROGRAPHlC DATUN: APPROXIMATE LEVEL or LOWEST Low WATER MAP 23 MAP 25 MAP 28 ROADS AI lh BLACK NUMBERED LINES INDICATE THE 1.000 METER UNIVERSAL TRANSVERSE I we: or > 3 ”~25 ‘ yam MERCATOR GRID. ZONE 56. INTERNATIONAL SPHEROID 4543 IV NW 4543 IV NE 4543 I NW mm mm, m or more lanes we W I _. L __ Burlluo area _h_._._m- _.w_ .; 1w" 6,, T“ “5' ”R“ ”'5‘” °‘ ““5 “Rm "”3““ "‘5 "m" MAP 24 MAP 26 MAP as loose or light surlace, two or more lanes wrde WW, 3 “"5 Church; School; Cemetery A,,,L_. ,,,#4, l ,: 1C9”. hard surface, one lane wrde ,,,, m ,,,,__ Limrl or danger line: Submerged reel LAW. 0 COMPILATION METHODS loose or light surlace, one lane Wlde ,, ,,,,,__,. . Wreck: Sunken: Exposed ,_,___.__..L..V.WA 0.09, 40:5, Phom'sm’eo Photo-planlmetric Map GLOSSARY A ~— - GRID ZONE DESIGNATION: ro GIVE A SYANDARD REFERENCE 0N W - ~ ,_ - -- E k fair or dry weather. loose surlace, two or more lanes wrde L. Sunken rocks, Foreshore liars ,A,,,,,,,,,,,,L-. 3 on u Mus 55N “"5 “in m "um! 100 METERS .. . . .. . . 3m! on go Fail 0' dry weather, 10°59 surlace. 0'19 lane Wide 2,, Rocks Dave or awash: Reel ,. ._ AAAAAA "”5 Ioo,ooo M. soum roznrrrrcmon SAMPLE POINT: t CHURCH A. USHO Chart 6048, 1944 (reliability good). “u" '“ cane. 90"“ Cart "a"; In” L_, -VL, ,, "W*" ——-———— 099"" Curves and r I" mmm‘ LRnd rmm identifying 100,000 mm. gerliJasal?m(t:222pigéorleiglsjufyreiigzgity good). I d 1 - > square in which the pornl lies: LP ‘ " ‘ Sander gauge rarroad. Single track he .2 Reserve”; Dam; 0m, .LL.L,..._L,,,77W #7__ 2_ Locate rim VERTICAL grid line to LEFT or Standard gauge railroad, double track “7‘_ / I S It I LP point and read LARGE limes libellnglho ’ a e a o a o s ”A __k___,__, l‘ tn th t b tt , Narrow gauge railroad, single track “mifiiv, , a . v p I I appnoxmnz MEAN DECLlNATlON I955 4:131:33”; up w 0 on margin 0’ 71 > 1"” row CENTER OF SHEEY Estimatotonlhslrorn grrd Iineto point: 3 "3”" 33"!“ WW“: “WI“? 0' "WW" "I" AAAAAAAA "V—‘hw— Rice Paddy; Marsh ___.,L_..._,is#_m_ “ A ANNUAL urcnsrrc CHANGE r’ “mom a, Locale lirstHORllONTAL gird line snow . . . x r d d Um“ I b I. "I Power transmrssron Irne ,2 _L., .._.,_..._._.,,.._.s L W n. “a, , . .. Us. diagram only to obtain numerical vulva. . 52'." taut: m loft olritrrgelillrrrjrg‘rfr, 0: Spot elevation in meters: Checked; Unchecked ,,,,, " I46 "tos "‘93: - “ To determine magnolia north lino, cor-nod the ”:0“ ‘2' ST:LLER"°'"";:"I’;;"; :"g"; dl ‘ ' 122 - - u u I“ "W“ 9'; '5' I l I" on s rorrr gri inc 0 pain : v1.11; Lem; Clill _i‘_ m .,_L,,,,,,, *mgjfifi P"°' 90"" P °" '5' ”0'“ “9" °“'" "W the run coordrrutos. Us. ONLV in. W! h I I II L d Q 10", Woods; Scrub "W wi'h Ibo value of Mr. angle between GRID LARGER hgurn ofthe and number; “up”; REFERENCE: LP713122 Be"! 9! 0 mi ; ocale object ,,,,.._.W,...s..,fi 0 NORTH and MAGNEWC NORYH as plan-don ollleO: 306000 ll reporting beyond 18' in my diroctiun —' 1mm 6nd 100- Design-lion. u: 56NLP713122 U MAN NW, CAROLI N E ISLAN DS Principal navigation light of lighthouse; Anchorage V, * \f/ Tropical grass; Coconut grove ”WW”, isw#ss CID thodogm scale a! "finer”! edg- ol "It Map. 1958 Militory Geology of Truk Islands, Caroline Islands MAPS 30 THROUGH 36 ENGINEERING MATERIALS TRUK ISLANDS CAROLINE ISLANDS 1225,000 151°32Ioor 339 32130! 340 341 342 U1) OT SW 345 346 348 37’ 30' 349 Mi litary Geology of Truk Islands MAP 30 Engineering Materials 351 7'27'00' I PACIFIC OCEAN 27 29 35 coral 33 27‘\\7 823 23 . ’ ._. or Ul FALE A Flood k knots 68/ a O K ———«<-—\ .— a N a ‘/0 up or I A v‘“ II I I / / / N :- 27 I I coral _-/ 2'2 , 26 27 29 CDT“ 322 ENGINEERING MATERIALS MAP, TRUK ISLANDS EXPLANATION 41 DESCRIPTION UNIT HARD COMPACT LAVAS lava flows from 35 to 160 feet thick; columnar jointing common. Bare bedrock of uniformly hard, compact, dark-grey basalt and andesite 82]. Exposed in cliffs. HARD MIXED LAVAS Bare bedrock of series of hard, darksgrey, heterogeneous basalt and andesite lava flows. of various hardness and composition, with scattered, interbedded, indurated, pyroclastic breccia lenses. Columnar jointing general and dikes locally common. Exposed in cliffs and on rockland hillcrests. MODERATELY HARD LAVA Bare bedrock of a moderately hard, light-grey, massive, fractured trachyte lava flow at least 150 feet thick. Cross fracturing and a rough platey cleavage about normal to fracture faces are common. Exposed on rockland summit and cliffs of Witipbn, Moen. HARD MIXED BRECCIA AND LAVA Bare bedrock of dark-grey, very firmly bonded, pyroclastic breccia; basalt rock blocks 1 inch to 6 feet across common; some interbedded basaltic lava; dikes cut breccia and lava. Exposed on rocky slopes and sea cliffs of Udot and Eot. 25’00' 820 MIXED VOLCANIC BRECCIA AND CONGLOMERATE Exposed or partially concealed beds of pyro- clastic breccia up to 300 feet thick and conglomerate beds 10 to 35 feet thick; angular blocks and rounded boulders and cobbles of basalt and andesite embedded in indurated matrix of volcanic detritus. Main exposures in cliffs. CALCAREOUS BEACH SANDS Loose, poorly graded, fine to coarse, angular to subrounded grains of coral-reef detritus. Exposed up to 2 feet above high-tide level along sand beaches and adjacent sandy flats. Only subaerial source of sand in Truk Islands. SHALLOW TO VERY DEEP STONY CLAYS 85% stony, lean, residual clay 1 to 30 feet deep over 8 volcanic bedrock and 15% bouldery talus 1 to 50 feet deep on volcanic bedrock. Clay is granular, firm, slightly plastic to plastic, and moderately to well drained. 50% of clay and 50 to 90% of talus are volcanic boulders and cobbles. Main exposures are the broad steeper slopes of volcanic islands. 819 fl“— DEEP TO VERY DEEP RESIDUAL CLAYS Residual, lean, brownish clay 10 to 50 feet deep on volcanic bedrock. average depth 25 feet. Upper 10 feet is granular grading downward to massive structure; clay is friable to firm, plastic to slightly plastic, and well drained. Main exposures are hilltops, divides, and gently sloping uplands and footslopes. SHALLOW TO DEEP CLAYS 0N HARD COMPACT LAVAS Earth,1 to 10 feet deep is 70% lean, granular, friable to firm, slightly plastic, brownish clay and 30% fat, granular, very firm, plastic, poorly drained, brownish clay. Bedrock is the same rock of Unit 1. Scattered exposures on hill- tops, saddles, and footslopes. SHALLOW TO DEEP CLAYS ON HARD MIXED LAVAS Earth, 1 to 10 feet deep of brownish, fat and lean clays, is same as earth portion of Unit 10; bedrock is the rock of Unit 2. Scattered exposures on gently sloping upland areas. 818 SHALLOW To DEEP CLAYS 0N MODERATELY HARD LAVAS Earth, 1 to 10 feet deep of brownish, , fat and lean clays, is same as earth portion of Unit 10; bedrock is the rock of Unit 3. The one -x" exposure is the gently sloping upland of Witipon, Moen. SHALLOW T0 DEEP LIMONITIC GRAVELLY CLAYS 0N HARD COMPACT LAVAS 1 to 8 feet of clay earth with top 1 to 3 feet containing 30 to 70% limonitic gravel; lean, brownish bottom clays are friable to firm, slightly plastic, and poorly drained. Bedrock is same as rock of Unit 1. Exposed in scattered gently sloping upland area. SHALLOW TO DEEP LIMONITIC GRAVELLY CLAYS ON HARD MIXED LAVAS Earth,1 to 8 feet deep is same as earth portion of Unit 13; bedrock is rock of Unit 2. 817 MANGROVE-SWAMP DEPOSITS Loose, coarse to fine, calcareous sand with smallscattered areas of mucky earth on sandy subsoil; submerged at high tide 0.5 to 2 feet. Occurs as irregular. fringe along coasts. 21 MARSHLAND DEPOSITS Muck and peat of various depths on sandy or plastic clay subsoils; 6 to 16 feet deep. Water table at or near ground surface. Occurs mainly on coastal plains. FILL Earth and rock fill on broad to elongate coastal flats on Moen. Param, Eten, and Dublon Island. Seaward margins protected by good to damaged seawalls of loose rock masonry or cement walls. Water table at or near sea level; fill elevations from sea level to 8 to 10 feet. Bearing capacity generally excellent to good except in local muddy areas. Extensive areas surfaced with good to broken concrete pavement. 22 NOTE: Unit 6, CORAL LIMESTONE, and Unit 18, CORAL BOULDERS, COBBLES, AND GRAVEL, occur only on the barrier-reef and lagoonal islands. See map 8. 816 24 SYMBOLS R7 0 Rock sample site — 057 Soil sample site 6 6C0 3 R6 13 58C ,@ 22’30' Quarry Rock sample site at quarry 815ooom.N_ 22 29 l. 14 20 24 CDTaI 11 A <6 IO/ 27 coral coral 21 25 ._. SD 24 coral coral 26 25 2 0 00731 25 22 31 24 31 \ , 30 26 ,/ \ / ‘g. \ x (/V ’1 21 u/ ,.r’//’ \,\v2/ TRUST TERRITORY DP THE/PACIFIC ISLANDS (U.S.A. 'AD’MINISTRATING AUTHORITY) 27 24 24 21 18 COTSI /IO\ VT? Coral Cora ' I‘srcizwfi's'l'hnd) 23 18 ‘T 27 3O 21 19 23 16 21 1 Coral 1‘ 11 17 Coral »\,,,I0\ \V 23 N L. 9” ._ a. N a. 22 19 (in 21 15 11 “a... I f r LAMOSEU BAY @Coral 7'22’00' 151°32'00r 33g 000mg 32/30” 340 W856 3 Edition 2-AMS (AFFE) Prepared under the direction of the Engineer, Hq AFFE/BA, by the U.S. Army Map Service, Far East. Compiled in 1957 by photogrammetric (multiplex) methods. Coastal hydrography compiled from USHO Chart 6049. 1944. Horizontal and vertical control established by Corps of Engineers, 1951. Names trans- Iiterated in accordance with rules of the US. Board on Geographic Names. Major roads are classified by reconnaissance by the 64th Engineer Battalion (Base Topographic), 1952; other roads are classified from source maps and aerial photography and are not verified by reconnaissance. Coastal vegetation are clas- sified by reconnaissance by Military Geology Branch, Intelligence Division, Office of the Engineer, Hq AFFE/8A, with personnel of the US. Geological Survey, 1955. Map not field checked. Engineering materials data based on field investigations and laboratory test 1954-1955, compiled and prepared by Military Geology Branch. Intelligence Division, Office of the Engineer, Hq, U.S. Army Japan with personnel of the U. S. Geological Survey. LEGEND ROADS All weather hard surface. two or more lanes wide None EuIlt-up area ,,,,,, 7, ,i,, , , None loose or lighl surface, two or more lanes wide ,, None Church; School: Cemetery ,,,i 6 I C91,“) hard surface, one lane wide ,, , , ,, ,,, None mm of danger IIne. Submerged reel _._, loose or light surface, one lane wide ", ,,,,,, None Wreck; Sunken; Exposed figiwfi, MM", Farr or dry weather, loose surface, two or more lanes wide :ETZEL, Sunken rocks; Foreshore flats 7,, ,,,,,i_,4, fair or dry weather, loose surface, one lane wide ,,,., ;::: ,_ , , . , Rocks bare or awash; Reef V,” , i,,,,,,,, * Cart tracir; frail ,, ,,i,,A,,,,,,, , ,, ,, _______ Depth Curves and Soundrngs In Falhoms 7",, ,1, ;_ ~. Standard gauge railroad, Single tract , , ,,,,, ,,,, -+—t—+-— Reservon, Dam, DIIch _ A ,7 a» Standard gauge railroad, double traclr ,,, ,, , ,, +4—h- damn Narrow gauge railroad, single track #7,, ,, 2"” 33" evaporators ‘ i i ”W" My TV“? El- ,1 ., .s ",7 77A LL 1‘ Narrow gauge railroad, double or multiple track ,,,,,,, Rice Paddy; Marsh i 7" Power transmission line _. , ,,,,,,,,,,,,,, 7 fl ,,, _ 7 , _, V V V ,1“ [:1 Nina; Mangrove , , ,, , ,,,,,,,A , , .1 Spot elevation in meters: Checked; Unchecked ,,,,,, , 1 I45 "ras -.,.._,,.,..,._ Wall; Levee; Cliff ,,, #7 E , . __.__ W§75§ [jg Woods; Scrub ,wmm, ,,, ,,, ,, ,, iv, ,,., Walerwheel of mill; Located object ,_,,,,,, ,,,,,,, O 010‘"er Prinupal navrgation light of lighthouse; Anchorage _. , * \1/ Tropical grass; Coconut grove EA, ,,, ,,,,,, ,7, DD APPROXIMATE IEAN DECLINATION I955 roa CENTER or SHEET ANNUAL MAGNETIC CHANGE I’ EASTERLV Use diagram only to obtain numerical values. To determine manna”: not”! lino, conned ”he pivot point “P" on the south edge of the map with the value of the angle between GRID NORTH and MAGNETIC NORTH, as plomd on the degm ocul- ar the nonh edg- ol the map. If 11 Mfg "‘°°"" \ 11 12 15 CM'UYFEL‘ - nun en Sapofa “fi . m , Flo \C a\ .3 ,\' - A, 0 \“L 42’“ 1‘ 4. :3 _".v/- »‘ NV?" 1 ‘1 gee/4‘s; Ila Stu, ”dim? n%”{{ow,.[é//é / y_ SWV fig; EETWI [5 I can, lb 11 Egg ,Coral reef 17 5 1 (30 coral 17 13 V .. are»? 19 3 coral 51 18 45. )7. I a. ,3. ”WI 745%“ l I .- ".k" Scale 1:25.000 N..— P 347 E. Paseur, 1954-1956. 1 Nautical Mile 1 0 l Statute Mile 1000 500 O 1000 2000 Meters 1 I>—-—-I 1—~"' v Coral reef 22 23 c°'a'€;>\_.lo/ C 4 21 Coral 8 /(‘ . 3 / 19 Coral reef ‘ COTaI 4 15/,0 /3”j ( g 19 I , . \ 2 / ‘ .— . 814 14 04% . “K i ,2 ,, 4 - ;.e 27 1 Coral? 15%,.F 18 W 14 Coral G 22‘ 21 Coral Z1 12 18 Coral 1552' ~§§ Coral reef 21 H Coral reel 7 fi i on: 17 .corag} i Coral reef'f'vi-l' @ 24 ‘7 l 813 /\ (—13 /\ 13 \e/ 11 4 12 3 11 18 21 39 1940 21 28 812 12 18 31 21 33 18 35 -— \ 24 “T'ngeTIcf \ 011 ~~ ll ‘ 315. \‘x 20'00” — _— 18\. coral \\ 28 16 \\\ coral \‘\\ 14 29 23 \\\. . - \‘ :: I 810 IO 00 \8/ 18 24 2 K3 \ 315‘ 25 \\ 1 \ -\ 17 29 ‘ \\ 15\ . sand and sheTIs‘\\ \\\ s. 28 17 coral 809 a43 37’30” ENGINEERING MATERIALS MAP, TRUK ISLANDS i Militarv Geology of Truk Islands MAP 31 Engineering Materials 151°39’30” 7°22'OO” ~ 814 ‘ 813 \& I I II I’L\ \I 0 II/ 77‘th 312 \l 27 18 l /’ I{ 1 W 811 k Irc‘ \I 0520i \ 0 R0 ' l 0 fly, were to 4 00000 o 0-, t--. 810 , @@ 22 coral COI’ZI 809 - 23 17 EXPLANATION \\\\ cgrlal \\\\\\ coral \.\ 21 ”\\ x‘ 25 “'3' 23 UNIT DESCRIPTION UNIT DESCRIPTION ___ HARD COMPACT LAVAS Bare bedrock Of uniformly hard, compact, dark-grey basalt and andesite W W SHALLOW T0 DEEP CLAYS ON MODERATELY HARD LAVAs Earth, 1 to 10 feet deep of brownish, 22 lava flows from 35 to 160 feet thick; columnar jointing common. Exposed in cliffs. /°2/:f/%§ fat and lean clays, is same as earth portion of Unit 10; bedrock is the rock of Unit 3. The one coral . . . . exposure 15 the gently sloping upland of Wltlpon, Moen. 25 23 13 19 HARD MIXED LAVAS Bare bedrock of series of hard, dark-grey, heterogeneous basalt and andesite . a coral / lava flows, of various hardness and composition, with scattered, interbedded, indurated, pyroclastic "W SHALLOW TO DEEP LIMONITIC GRAVELLY CLAYS ON HARD COMPACT LAVAS 1 to 8 feet of 808 08 1 " KL/ breccia lenses. Columnar jointing general and dikes locally common. Exposed in cliffs and on $941.1 RE. clay earth with top 1 to 3 feet containing 30 to 70% limonitic gravel; lean, brownish bottom clays »»—( ————— @ "cnr’al: Coral rockland hillcrests. are friable to firm, slightly plastic, and poorly drained. Bedrock is same as rock of Unit 1. Exposed in scattered gently sloping upland area. ’ MODERATELY HARD LAVA Bare bedrock of a moderately hard, light-grey, massive, fractured w cm' trachyte lava flow at least 150 feet thick. Cross fracturing and a rough platey cleavage about \Véts, % SHALLOW TO DEEP LIMONITIc GRAVELLY CLAYS ON HARD MIXED LAVAs Earth,1 tosfeet deep 23 27 normal to fracture faces are common. Exposed on rockland summit and cliffs of Witipt'm, Moen. §\ RX is same as earth portion of Unit 13; bedrock rs rock of Unit 2. 25 sand . “ . . sand 39 40 HARD MIXED BRECCIA AND LAVA Bare bedrock of dark-grey, very firmly bonded, pyroclastic %. MANGROVE-SWAMP DEPOSITS Loose, coarse to fine, calcareous sand with smallscattered areas 21 breccia; basalt rock blocks 1 inch to 6 feet across common; some interbedded basaltic lava; dikes ,.:. , of mucky earth on sandy subsoil; submerged at high tide 0.5 to 2 feet. Occurs as irregular fringe 14 19 cut breccia and lava. Exposed on rocky slopes and sea cliffs of Udot and Eot. along coasts. A sand * l7 ““9"" MIXED VOLCANIC BRECCIA AND CONGLOMERATE Exposed or partially concealed beds of per- Air's MARSHLAND DEPOSITS MUCk and peat 0f various depths on sandy or plastic clay SubSOIIS; 22 1 's and) elastic breccia up to 300 feet thick and conglomerate beds 10 to 35 feet thick; angular blocks “Li“ 5 to 15 feet deep. Water table at 0" near ground surface. Occurs mainly 0” coastal plains. and rounded boulders and cobbles of basalt and andesite embedded in indurated matrix of volcanic 807 807 detritus. Main exposures in cliffs. FILLd Earth and rock fill on broad :3 elongate coastal slats on Moen, Param, Eten, and Dublon ‘ s an . Seaward margins protected y goo to damage seawalls of loose rock masonry or cement CALCAREOUS BEACH SANDS Loose, poorly graded, fine to coarse. angular to subrounded grains walls. Water table at or near sea level; fill elevations from sea level to 8 to 10 feet. Bearing of coral-reef detritus. Exposed up to 2 feet above high-tide level along sand beaches and adjacent capacity generally excellent to good except in local muddy areas. Extensive areas surfaced with sandy flats. Only subaerial source of sand in Truk Islands. good to broken concrete pavement. 22 7 9/ \’ SHALLOW TO VERY DEEP STONY CLAYS 85% stony, lean, residual clay I to 30 feet deep over I . . . volcanic bedrock and 15% bouldery talus 1 to 50 feet deep on volcanic bedrock. Clay is granular, NOTE' Unit 6' CORAL LIMESTONE and‘Unlt 18' CORAL BOULDERS' COBBLES' AND GRAVEL' occur only 58 11 firm, slightly plastic to plastic, and moderately to well drained. 50% of clay and 50 to 90% of on the barrier-reef and Iagoonal Islands. See map 8' 27 talus are volcanic boulders and cobbles. Main exposures are the broad steeper slopes of volcanic coral /2_34\\\_—/ islands. SYMBOLS 17’30” —‘ —— DEEP TO VERY DEEP RESIDUAL CLAYS Residual, lean, brownish clay 10 to 50 feet deep on 0R7 Rock sample site _ 17/30” volcanic bedrock, average depth 25 feet. Upper 10 feet is granular grading downward to massive 57 structure; clay is friable to firm, plastic to slightly plastic, and well drained. Main exposures are 0 Soil sample site 8 8 000m N 279 hilltops, divides, and gently sloping uplands and footslopes. 06 06 ' l X06 Quarry SHALLOW TO DEEP CLAYS 0N HARD COMPACT LAVAS Earth,1 to 10 feet deep is 70% lean, R6 granular, friable to firm, slightly plastic, brownish clay and 30% fat, granular, very firm, plastic, fist ROCK sample site at quarry PA C I F] C poorly drained, brownish clay. Bedrock is the same rock of Unit 1. Scattered exposures on hill- tops, saddles, and footslopes. SHALLOW T0 DEEP CLAYS ON HARD MIXED LAVAS Earth, 1 to 10 feet deep of brownish, fat and lean clays, is same as earth portion of Unit 10; bedrock is the rock of Unit 2. Scattered ’ exposures on gently sloping upland areas. I f 3 7°17Ioor ‘ ' o 4 7'17'00” 151°32’00” 339 000m.E_ 32’30” 345 346 3:7 348 37/30” 349 350 351 151°39’30” W856 5 Edition 2-AMS (AFFE) Prepared under the direction of the Engineer, Hq AFFE/8A, by the US. Army Map Service, Far East. Compiled in 1957 by photogrammetric (multiplex) methods. Coastal hydrography compiled from USHO Chart 6049, 1944. Horizontal and vertical control established by Corps of Engineers, 1951. Names transiiterated in accordance with rules of the U.S. Board on Geographic Names. Major roads are classified by reconnaissance by the 64th Engineer Battalion(BaseTopograpnic), 1952; other roads are classified from source maps and aerial photography and are not verified by reconnaissance. Coastal vegetation are classified by reconnaissance by Military Geology Branch, Intelligence Division, Office of the Engineer, Hcr AFFE/BA, with personnel of the U.S. Geological Survey, 1955. Map not field checked. Engineering materials data based on field investigations and laboratory test 1954-1955, compiled and prepared by Military Geology Branch. Intelligence Division, Office of the Engineer, Hq, U.S. Army Japan with personnel of the US. Geological Survey. LEGEND ROADS All weather hard surlace, two or more lanes wide ma , None Builliup area ,...- .. .. ....-... loose or light surlace, two or more lanes wide _.._.. None Church; School; Cemetery ___77.-A_ .......v. hard surlace, one lane wide ,fi,a_,.--i. A. None loose or light surlace, one lane wide 777., None Fair or dry weather, loose surlace, tvro or more lanes wide :LL__“, Fair or dry weather, loose surlace, one lane wide s..__,.. :2 2 2 :: 2 - Carl track; lrail ___“- ___. ..__A ___--- Standard gauge railroad, sirule track _,-_ ”Li, —l—-+—t— Slandnrd pug: railroad, double track __Li 1 N Narrow gauze railroad, single track - ..,_..._. ._ :’:" Narrow gauge railroad, double or multiple luck Va- —vr—“—-vv-- Power transmission line ,_.h_____~ _-....__./’/ Spot elevation in meters: Checked; Unchecked -..._.._. "us ‘166 Wall; Levee; Cliff ____i__-.._. __ ”375$ Walervrheel of mill; Located object ”WW... ___,NL... Cl 010'" Principal navigation light of lizhlhouse; Anchorage __ * \1/ Limil of danger line; Submerged reel 7.,, Wreck: Sunken; Exposed -.. Sunken rocks; Foreshore Ilats LV_ifi + Rocks hare or avrasll; Reel ., ELLE“-.. .. -.... 1. Depth Curves and “ in Falhoms None 1 : 108m. Reservoir; Dam; Ditch ,7 Salt cvaporalors L. Rice Paddy; Marsh #VA__M._._ Nipa; Woods; Scrub WW. Mi Tropical grass; Coconut grove ,L—_____, I:I I:I GN 4'45’ OR 144 wins APPROXIMATE MEAN DECLINATION I955 FDR CENTER OF SHEET ANNUAL MAGNETIC CHANGE II EASTERLV Us. diagram only to chain mum-I'm! who. To determine magnetic north lino, conned "to rpivof point "P" on Ibo south edge of tho map with "t- valuo o! ”to angle bow GRID NORTH and MAGNETIC NORTH, as ploflud on ihdogmxakaflhenorfhodgo of Ibo map. Scale 1:25.000 1 '1” 0 1 Statute Mile 1000 500 0 1000 2000 Meters I 1—1 I-—-r 1——r I—r 1—{ fl 1000 500 0 1000 2000 Yards I k—‘l P—‘I E—i P—T 1—1 1 0 1 Nautical Mile . i r i r . a CONTOUR INTERVAL IO METERS VERTICAL DATUM: MEAN SEA LEVEL TRANSVERSE MERCATOR PROJECTION HORIZONTAL DATUM ls BASED ON THE ASTRONOMIC STATION NO. 2 (1951 ): 151'53’34.3' EAST OF GREENWICH. 7'21/37.7' NORTH HYDROGRAPHIC DATUM: APPROXIMATE LEVEL OF LOWEST LOW WATER BLACK NUMBERED LINES INDICATE THE [.000 METER UNIVERSAL TRANSVERSE MERCATOR GRID, ZONE 56. INTERNATIONAL SPHEROID THE LAST THREE DIGITS OF THE GRID NUMBERS ARE OMITTED GRID ZONE DESIGNATION: TO GIVE A STANDARD REFERENCE ON THIS SHEET TO NEAREST 100 METERS 100,000 M. SQUARE IDENTIFICATION SAMPLE POlNT: TRAIL JUNCTION 1. Read letters identifying 100,000 meter $011!!! In which the paint has: .Locate llrsl VERTICAL grid line to LEFT 0! point and rend LARGE Ilgures labeling the line erlhar In the top or bottom margin, or on the line 1159": 48 Estimate tenths lrom grid line to point: 9 . Locate 'lffl HORIZONTAL grid line BELOW point and read LARGE figures labeling the line either In the left or right margin, or LP N u IGNORE the SMALLER fllures of any grid number; these are for lindinu the lull coordinates. Use ONLY the LARGER Iizures of the and number; example: 806 000 on the line itself; 11 Estimate tenths from grid line to point: 1 SAMPLE REFERENCE: LP489111 II reporting beyond 18" in any direction, prefix Grid Zorro Damnation, as: 56N LP489111 1958 Interpretations of engineering materials by Harold G. May and James E. Paseur, 1954-1956. COVERAGE DIAGRAM U.S. ARMY MAP SERVICE, FAR EAST - 57-041 - R~15 - [/59 -. 3.40 INDEX TO ADJOINING SHEETS W§w§ 4544 ll NW §~W§§§§§§§§§ MAP 34 R V“ ‘1‘" “it; “3‘ Vi \ 4544 III sw 45 III SE 45 ll sw $§W§W \ MAP 30 MAP 32 MAIP 35 §\\ COMPILATION METHODS “3°,I°"",".‘.'I",9F,”° sen: GLOSSARY mountain, peak A. usuo Chart 6049, 1944 (reliability good). Nom en bay Aerial photography; 1-Feb., July 1946, 2-Feb. 1947. am"; can; ”:5: TOL NW, CAROLINE ISLANDS TRUK ISLANDS .1 -1, Li D I) “I,“ Military Geology of Truk Islands . o o O o o . . . CAROLINE ISLANDS 1.25 000 0° 2 3 4 5 6° 7 MAP 32 Engineering Materials 1 l I , 1 1L, I_1_L,1LL_L.J_;L1 I I ILLIAIJLLLI .. - 3 . 1511313130135? 40/00r353 354 355 356 357 42/30! 358 1‘59 “60 361 362 45'00' 363 354 65 151 47100" 1 ' ' 7‘27’00" - 1 1 1 1 1 7 27'00 1 | 1 30 1 1 29 I I ' ‘ 1 I ‘ coral 29 I 1 I 3 1 2 f 1 1 4 I 11 mg, 1‘ 1 1 24 coral I I ‘ I I /”‘\ 26 I 1. CDT? I 32 I I/ 5 \\\ coral , 1 I 27 1 coral ‘1 1’ 5 k 1 34 1 1 I 291 I ‘1 I1 [/1331 1 1 ‘ 1 1 E 1 ‘~es.~’ 1 1 l 21 1 1 1 11 coral I :‘ 27 23 ‘ I ‘ n ,. 1 ‘ 7 7 23 1 7 7 823 ($23 .7 I7 .7 , ”777777 7 . 7- 77 7 7 723 77 7 7777;77 7-77 7777 77 1. 7 7 77 33 77 7 7 77 7 732 -. 7 77 77 7777‘s; 7 i 7 7 77 77 7 77 7 7 7 1 I é; coral 1 1 1 1 1 ‘ ‘ L53 1 29 3 < 1 1 1 , coral 1 1 I 1 1 ‘ 1 1 1 30 I, TRUK LIAGOON 3 31 I I 3 251 1 ‘ 24 1 I iii coral 1 28 1 , 30 1 1 ; I 1 1 1 1?” ‘1 1 ‘ 31 1 ’ 29 1 / 3 ,’ 1 27 coral 24 1 1 ' 1 / / I r‘ x i 1 1 1 1 1 1 27 1' (JD/1 1, 1 1 1 , 1 1 1 ’, 1 I 1‘ 5 ‘1 ’ I J 8 1 coral 1 l 1 24 / ‘1 ‘1 8 r’ I _ 1‘ 1 ‘\\_/ 1 19 11 \\.‘—‘/’ I 3 I I I 1 l ‘ I ‘ {I ‘ ‘ 2‘ ‘ ENGINEERING MATERIALS MAP TRUK ISLANDS 1 1 1 - I 1 ‘Emi‘ 1 ““““““““““““““““““““““““““““““““““ 1 ““““““““““““ 1 3 9 1 I / O I 6‘1 t; 58 59 '1 -7 1 3 8.. 1 EXPLANATION 1 24 1 18 I 18 ‘ 1 1 1 1 3 21 3 1TRUST TERRITORY OF THE IPACIFIC ISLANDS 3 UNIT DESCRIPTION I 23 1 1 (U.S.A. ADMINISTRATqu AUTHORITY) 1 16 gm I “"3' 210°”, :‘LW ‘ ,, ,, _, .. ,,L,. ., __.,.._,.__ _ 2‘1 "ELLE”... , 1 ., . .17. L .. , A _. 7-- 7 HARD COMPACT LAVAS Bare bedrock of uniformly hard, compact, dark-grey basalt and andesite ea“ 821 ‘til 1 ' ' i 1 I ,1 21 lava flows from 35 to 160 feet thick; columnar jointing common. Exposed in cliffs. 11 , 12 I 2 22 I HARD MIXED LAVAS Bare bedrock of series of hard, darkegrey, heterogeneous basalt and andesite I 2d 18 l 13 lava flows, of various hardness and composition, with scattered, interbedded, indurated, pyroclastic I * breccia lenses. Columnar jointing general and dikes locally common. Exposed in cliffs and on 1 1 rockland hillcrests. , 1 l 1‘ 1 I Uncovers 2feet MODERATELY HARD LAVA Bare bedrock of a moderately hard, light-grey, massive, fractured I I trachyte lava flow at least 150 feet thick. Cross fracturing and a rough platey cleavage about I normal to fracture faces are common. Exposed on rockland summit and cliffs of Witipén. Moen. I , 3I HARD MIXED BRECCIA AND LAVA Bare bedrock of dark-grey, very firmly bonded, pyroclastlc ’3;!’)OI I 3I 14 breccia; basalt rock blocks 1 inch to 6 feet across common; some interbedded basaltic lava; dikes 820 “1“ ”‘7 41 20 1 . cut breccla and lava. Exposed on rocky slopes and sea cliffs of Udot and Eot. 25’00’ 520 1 1 corn 1 ,1 121 , ' I '1 i 21 I 1 MIXED VOLCANIC BRECCIA AND CONGLOMERATE Exposed or partially concealed beds Of pyro- : I 1 clastic breccia up to 300 feet thick and conglomerate beds 10 to 35 feet thick; angular blocks I 1 1 1/ and rounded boulders and cobbles of basalt and andesite embedded in indurated matrix of volcanic 1 1 1 1 23 detritus. Main exposures in cliffs. 1 1 1 coral : I, CALCAREOUS BEACH SANDS Loose, poorly graded, fine to coarse, angular to subrounded grains I 1 E of coral-reef detritus. Exposed up to 2 feet above high-tide level along sand beaches and adjacent 151 1’ 1 sandy flats. Only subaerial source of sand in Truk Islands. 1 .1 1 I I 119 SHALLOW TO VERY DEEP STONY CLAYS 85% stony, lean, residual clay I to 30 feet deep over 11 1'1"-Coral 1M 7»__ u“ 11 ‘1 volcanic bedrock and 15% bouldery talus 1 to 50 feet deep on volcanic bedrock. Clay is granular, U'mm e" Ch'dsia 1 ———————— Q’Elsfiérf: ~~~~~ 1 firm, slightly plastic to plastic, and moderately to well drained. 50% of clay and 50 to 90% of ___N_ 319 819 Luvs”, 3%“— 19 ' “ 1‘ r talus are volcanic boulders and cobbles. Main exposures are the broad steeper slopes of volcanic 1 Coral reel 171 1 islands. 15 22 I I \:‘ DEEP TO VERY DEEP RESIDUAL CLAYS Residual, lean, brownish clay 10 to 50 feet deep on 21 1 I 22 \ volcanic bedrock, average depth 25 feet. Upper 10 feet is granular grading downward to massive 1 1 structure; clay is friable to firm, plastic to slightly plastic, and well drained. Main exposures are 71 1 1 hilltops, diVIdes, and gently sloping uplands and footslopes. 1 a . .‘_ ’ 1 E SHALLOW TO DEEP CLAYS ON HARD COMPACT LAVAS Earth,1 to 10 feet deep is 70% lean, @ 1 1, 1 1 1 £51 granular, friable to firm, slightly plastic. brownish clay and 30% fat, granular, very firm, plastic, 17 1 ”(/4 1. 1 1 1 1 1 poorly drained, brownish clay. Bedrock is the same rock of Unit 1. Scattered exposures on hill- _ 15 22 1 ’21/ 1 8 1 13 ,1 16 1 19 1 I “5 tops, saddles, and footslopes. I ‘ Ila/coral 1 / u 11 1 1 1 1 1 ,7 1 1 1 1 o 1 I I ,e” I I 1 1 \ :06,“ I I SHALLOW T0 DEEP CLAYS ON HARD MIXED LAVAS Earth, 1 to 10 feet deep of brownish, fat 11 //’ 1 1' I 1 14 1 I and lean clays, is same as earth portion of Unit 10; bedrock is the rock of Unit 2. Scattered .___. 818 818 W’ 16 I / / 18 I T T I ' o I 1 exposures on gently sloping upland areas. 1/ 1 1 I = 1 ——————— 15'" r 18 1 I [/17 1 8 1 com %§:’Wf SHALLOW T0 DEEP CLAYS 0N MODERATELY HARD LAVAS Earth, 1 to 10 feet deep of brownish, 1 // ‘ , 1 15 15 12 10 1 Wig/,2: fat and lean clays, is same as earth portion of Unit 10; bedrock is the rock of Unit 3. The one // I I I I 9 1 ' exposure is the gently sloping upland of Witipon, Moen. ' / 1 ' I coral / | 1 1 ‘ 21 42 2/2 1 1 115 12 \16 g SHALLOW TO DEEP LIMONITIC GRAVELLY CLAYS 0N HARD COMPACT LAVAS 1 to 8 feet of 61 1’ 1 I77. I sandianu shells sand and shells clay earth with top 1 to 3 feet containing 30 to 70% limonitic gravel; lean, brownish bottom clays 2 1' 1 16 1 / 5 \1 I 1' are friable to firm, slightly plastic, and poorly drained. Bedrock is same as rock of Unit 1. Exposed 18 o 1’ “M i I 61mm I I I \ in scattered gently sloping upland area. 1; 1 : A/ 1 11 L" 1 31 SHALLOW T0 DEEP LIMONITIC GRAVELLY CLAYS 0N HARD MIXED LAVAS Earth,1 to 8 feet deep 11 1 12 12 is same as earth portion of Unit 13; bedrock is rock of Unit 2. 1 : 1 LA. 817 ’3 ‘ ~ - ---- ‘1 1 1 1] 1, I7 1 12 1 1 18 MANGROVE-SWAMP DEPOSITS Loose, coarse to fine, calcareous sand with smallscattered areas 1 11 22 .1 _3_31 1 1 of mucky earth on sandy subsoil; submerged at high tide 0.5 to 2 feet. Occurs as irregular fringe I I I 1 1 along coasts. 1 I 1 1 1 1 1 1 1 1 “at—[511“: MARSHLAND DEPOSITS Muck and peat of various depths on sandy or plastic clay subsoils; 1 1 1 1 1 3 f7 _ ._ 6 to 16 feet deep. Water table at or near ground surface. Occurs mainly on coastal plains. 211 ‘1 53 54 55 17 I 55 12 1 13 11 19 1 . 1 1 , 1 FILL Earth and rock fill on broad to elongate coastal flats on Moen, Param, Eten, and Dublon 1 1 cu Indicates swept depth area In feet 1 11 Island. Seaward margins protected by good to damaged seawalls of loose rock masonry or cement 1 ‘1 1 walls. Water table at or near sea level; fill elevations from sea level to 8 to 10 feet. Bearing ‘11 1 1 capacity generally excellent to good except in local muddy areas. Extensive areas surfaced with ‘ 1 1 1 I I .\ good to broken concrete pavement. \1 1 1 17 _ 1 eégggisax 12 a ‘1 1 16 1 e 1 13 1 ' 24 - 7—7— 816 16 11 1 ’TT“ 1 1 “ml : 21 j NOTE: Unh & CORALIJMESTONE.and Unfl 18.CORAL BOULDERS,COBBLES.AND GRAVEL,occuronw 1 1 1 : on the barrier-reef and la oonal islands. See ma 8. 1 1 1 /6 DOT ROAD g p 11 1 1 I \, (anchorage) 13 22 1 1 1 \1) 8 — SYMBOLS l \ I ' d l \ 1 1 \ 1 1 ' 7 l7 \\ ,-.- 5:31, '1 I I 12 ‘ 1 b‘ 51 W on Rock sample site ’,/ 29 \ r’ 23 \1 I 15 I coral l7 , 32 57 f// (0* 2230' — /0\ 11 I1 4 11 1 coral 1 1g; : \ 0 Soil sample site 7 _ 22r30/r _ \ \ [l ‘ 1 1 coral 3‘1 \_T 1 I 41 .- . 3. 1 1 1 1 - 2 1' V“ W" ' M \ 1 l 17 2 \X I 21 I I 8 Rock sample site at quarry 815000m N 1 / 15 I I I 815 T V I 2/ W ”T 7 WT WIT \n » I... 17 I e I ‘2 l7 ans-floral reef \ 1 I 3 13 \1%:\ 11 /\/"‘ I 6 3 , I i 17 ';’ 1 8 s 11 ‘19‘1 15 313 ‘° 7 ' c | I o 4 ° \ ‘ ' I 1 C )9? re016\ + 61> 21 61 o 13 1 18 1 coral 11 8 14 15 1 1 8 ma 11 61 z 1 4 \ 1 I 13 12 _ 4 17 12 9 l ’ /1/10\ I I 7:»221001 mm" 2 + Coral I \ 13I I shells I\ o 15 4 9 54 11 K a} 3\ 8 I I 12 l mew 7°22/001/ 151“39®O”352000m.E‘ 4000'353 354 355 356 35] 4260” 358 359 360 P 36245’00" 363 354 365 151'4W00” 361 W355 5 Scale 1:25.000 Edition 2-AMS AFFE 1 7 . . . . ( > 1 7 ° 15‘3”“ we Interpretations of engineering materials by Harold G. May and James U-S- ARMY MAP SERVICE. FAR EAST - 57-041 - R-15 - 1/59 - 3.4c Prepared under the direction or the Engineer, Hq AFFE/BA, by the us. Army Map Service, Far 100” 50° 1_? 1°00 200° "Me's E' Paseur' 1954'1956' East. Compiled in 1957 by photogrammetric (multiplex) methods. Coastal hydrography compiled 215$ 1—5730 0 1000 2000 Yards from USHO Chart 6049, 1944. Horizontal and vertical control established by Corps of Engineers, r i—i i—i a I——-«I 1-—1 1951. Names transliterated in accordance with rules of the US. Board on Geographic Names. 1 % 0 ”but“, M'le Maior roads are classified by reconnaissance by the 64th Engineer Battalion(Basei‘opographic), ' ' 1952; other roads are classified from source maps and aerial photography and are not verified COVERAGE DIAGRAM INDEX TO ADJOIN'NG SHEETS by reconnaissance. Coastal vegetation are classified by reconnaissance by Military Geology Branch, Intelligence Division, Office of the Engineer, Hq AFFE/BA, with personnel of the U.S. CONTOUR INTERVAL TO METERS WITH SUPPLEMENTARY CONTOURS AT 5 METER INTERVALS Geological Survey, 1955, Map not field checked. VERT'CAL DAV-”‘1 "EA" 5“ LEVEL 4544 || NW Engineering materials data based on field Investigations and laboratory test 1954-1955, compiled 1 MAP 34 and prepared by Military Geology Branch. Intelligence Division, Office of the Engineer, Hq, U.s. TRANSVERSE MERCATOR PROJECTION W § Army Japan with personnel Of the U.S. Geological Survey. HORIZONTAL DATUN IS BASED ON THE ASTRONONIC STATION N0. 2 (I95l ): § 151°53’34.3" EAST OF GREENWICH. 7 21/247,7’ NORTH \‘s‘\\ {Q‘E‘ifiQfi‘Q‘ ~‘\: . , \.\ ‘1 LEGEND HYDROGRAPHIC oATuu - APPROXIMATE LEVEL OF LOWEST Low WATER N§§T§§§¥ 4544 III SW 4544 III SE 4544 H SW ' ‘W‘W\\N\\§ MAP 30 MAP 32 MAP 35 - .~ \z. xx \\\v \ V ROADS BLACK NUMBERED LINES iNDICATE THE 1.000 METER UNIVERSAL TRANSVERSE \§%‘§$\\$§®Q?§ \ All weather IERCATOR GRID. ZONE 56. INTERNATIONAL SPHEROID “ \\‘{“\{§\t~t‘c‘v'\\\§ 7\ \%;s\\-~‘\.~\\‘\§\‘\~\’t\ 4543 Iv Nw 4543 IV NE 4543 I NW hard surface, m or more lanes wide None Bum“, am 6“ THE LAsT runs: plans or THE GRID Williams AR! oriITTEo “x MAP 31 MAP 33 MAP 36 loose or light surface, two or more lanes wide None Church; School; Cemetery k\\\\ ‘§E\\\\\\\\\\\ \\\\\\\ 1 hard surlace, one lane wide None Limit ol danger line; Submerged reel 4.“, COMPILATION METHODS loose or light surlace, one lane wide None Wreck: Sunken; Exposed 0.10, on Photo-stereo Photo-plonlmotric Map . . , a Gino ZONE DESIGNATION: To GIVE A STANDARD REFERENCE N ‘ Fair or dry weather, loose surlace, two or more lanes wide Sunken rocks, Foreshore flats on ‘ "'Ls 56N Tle SNEET To NEAREST we METEgS W I: 0 GLOSSARY h Fair or dry weather, loose surface, one lane wide Roclis bare or awash; Reel 3 IIILS 100,000 M. SQUARE IDENTIFICATION SAMPLE POINT: ; SCHOOL A. USHO Chart 5049' 1944 (reliability good). ”Line; (:22: 03:; Cart track; trail ____..____ Depth Curves and .. in Falhoms '1 RM 1mm immym 1001000 mm P Aerial photography Felt. July 1946 . . 1‘1 1 1 square in which the point lies: L Standard satire railroad. smiile lm ‘T—t—t— Mm"; Dam; mm. 2. locate rim VERTICAL grid m to LEFT of Standard gauge railroad, double tracli LP point and mil LARGE llamas labeling the 1 ‘ 2’!” Salt evaporator: line either in the top or bottom margin, or "WW KNEE railroad, 5mm "80* APPROXIMATE IEAN DECLINATION l955 on thelinailsoll: 589 , . 3"” ron CENTER or SHEET Estimate lentils from grid line to point: "WOW Raul! ”"1034. “WW 0' "WWII" "'5" Rice Paddy: Marsh ANNUAL MAGNETIC CHANGE I’ EASTERLV 3. Locate lirsi NORIIONTAL [rid line BELOW . . . l/ . point and road lARGE figures labeling the Power transmission line ___# ......... 1 . Us. diagram only lo obtain ml values. _ lino either in the left or right rmrgin, or Spot elevation in meters: Checked; Unchecked “ us was "'9'; = To dolomim magnetic north lino, carried the "31"": "" SM‘LLER "9"” 9' ‘_"V 0" 1"” “M “3°": 1 _ _ 16 . . .. .. Iml "0M0"; "I!“ I" '0' ""00"! Estimate tenths from [I'ld line to point: 4 Wall; Levee; Cliff __.___.. L1 PM” PW" P on "'0 M 9"9‘ 0' "'° MP the run coordinates. us. our the WI h | 1 ." L “1 b' 1 v Tower woo“; Scrub with the value of the angle between GRID LARGER figures of the grid number; “My“ REFERENCE: LP589164 aervr ee 0 MI ; 00a 9 0 let 0 onmpll: . .. - - NORTH and MAGNETIC NORTH, a: plotted on 815 000 If reporting beyond 118 in any direction, Principal navigation light of lighthouse; Anchorage W * 3/ Tropical grass; Coconut grove rho degree scale or "to north edge of rho imp. — PM“ 6"“ 1"“ D”"""'""' “‘ SGNLPSSQIM U DOT SE, CARO LI N E ISLAN DS 1958 TRUK ISLANDS VIV ,(> T[ ‘x\" E Military Geology of Truk Islands CAROLINE ISLANDS 125,000 5" ‘ ' 1’ e/ f i 1 0° 2° 3° 4° 5° 6° 7° MAP 33 Engineering Materials L LJWL’LLLLIJLLLLLLL/ 42/30! 358 359 360 361 362 45’00’ 151 "47’00’ 7'22’00’ 15139430" 352 40'00” 353 354 355 356 7°22‘00' Lia'- W’ ‘ 11 I 3t J 3 7 2 I K K ’° ‘7 ‘2 “’3' colrlal l: 12 19 13 i 15 5 2 I / ¢ : g i 11 11 ° 3 mi 11 x b I 13-34 I/ 1\\ (\ 11 \\ L 16 . I 16 \l 5659‘: \ 3a ,3 \/ . 11 I ‘ I \ . l I x 14 l 814 - 15 - lT~-/\ ‘x. ’ ,,,,, 14 W .....W Lu- _. m- -.L. .. z 15 814 \ I I i I 3-24 I C: *0“ ° 7 \ t 2 c \ 19 \\ coral . 15 v 3 coral rT’AI \\ coir; 3 j 12 F 1 a ‘\ ‘\\\ \ \ ’ 7 3 \\ 1 \\ \\ 2 1 O_/ r. . 16 (12 I I . 2 1‘3 coral \coral i \\ 5 I 3 16 3 3 15;? \\. \\ \i l 1 0 co‘rai I. » fig ‘ ‘I 1 1° W I ENGINEERING MATERIALS MAP 12 . Is l/o \ 9 core ‘I 51 :4 VI}, x, I “T 3 A : III 2: ./< 21) a 813 II 7 1%}. L 13 .- .. I . ... 23 ‘ I Egg, .....,_,.W.. 813 c t j W ' , EXPLANATION I I \o/ I \ 4 I ‘ \\ 3 OROR N g cm, Q/ 'is' 13 15 \\ 8 .- .» . i 19 3 J . ' DESCRIPTION I ”'5' ,7 a»: I ' l 21 / 3 3‘ ’o I 2 ‘ 20 1‘ coral I’ 54 ‘I 23 HARD COMPACT LAVAS Bare bedrock of uniformly hard, compact, dark-grey basalt and andesite to?“ 59 60 6 w a. /‘y\ I ,: lava flows from 35 to 160 feet thick; columnar jointing common. Exposed in cliffs. m _‘ 3 7 B; “m" \\_/| I . ‘ L 31“ 'I HARD MIXED LAVAS Bare bedrock Of series of hard. dark-grey, heterogeneous basalt and andesite ‘ "0 ,. II lava flows, of various hardness and composition, with scattered, interbedded, indurated, pyroclastic i 24 23 2“ ‘1 ' breccia lenses. Columnar jointing general and dikes locally common. Exposed in cliffs and on ‘ cprai 21 II ~—— 31“. - . 23 coral 4 ’I H, rockland hIlIcrests. I cm, 8 812 W3, / I .12 I WWW _- .. 12 W. 12 ‘7“ 16 I MODERATELY HARD LAVA Bare bedrock of a moderately hard, light-grey, massive. fractured I I0 I, I trachyte lava flow at least 150 feet thick. Cross fracturing and a rough platey cleavage about 6 \l‘ I13. II normal to fracture faces are common. Exposed on rockland summit and cliffs of Witipdn, Moen. T R U K I S L A N D S 19 cm' W; I I’ 1 ‘I ,x/ Q HARD MIXED BRECCIA AND LAVA Bare bedrock of dark-grey, very firmly bonded, pyroclastic 15 I__J Indicates swept depth area in feet . ‘2) 49 ‘I / breccia; basalt rock blocks 1 inch to 6 feet across common; some interbedded basaltic lava; dikes \ a \ // , cut breccia and lava. Exposed on rocky slopes and sea cliffs of Udot and Eot. 16 3 10 19 23 III ,A MIXED VOLCANIC BRECCIA AND CONGLOMERATE Exposed or partially concealed beds of per- ”’3' 30,43, 14 62“ ,l * > clastic breccia up to 300 feet thick and conglomerate beds 10 to 35 feet thick; angular blocks ‘I\*—/ and rounded boulders and cobbles of basalt and andesite embedded in indurated matrix of volcanic 2 \\ 1; detritus. Main exposures in cliffs. 63:13! 3 4 \ L, 8 811 \\ ..-.... CALCAREOUS BEACH SANDS Loose, poorly graded, fine to coarse, angular to subrounded grains - , . . > . .. a . a v T 1 1 11 \\ of coral-reef detritus. Exposed up to 2 feet above high-tide level along sand beaches and adjacent 28 I {K 20,00” __ \\\ sandy flats. Only subaerial source of sand in Truk Islands. 17 21 22 <5 __ 18 Carl“ _ 20,00” \\ SHALLOW TO VERY DEEP STONY CLAYS 85% stony, lean, residual clay I to 30 feet deep over 5 >¥ \ firm, slightly plastic to plastic, and moderately to well drained. 50% of clay and 50 to 90% of 21 19 talus are volcanic boulders and cobbles. Main exposures are the broad steeper slopes of volcanic islands. volcanic bedrock and 15% bouldery talus 1 to 50 feet deep on volcanic bedrock. Clay is granular, @ 15 4 5 23 20 DEEP TO VERY DEEP RESIDUAL CLAYS Residual, lean, brownish clay 10 to 50 feet deep on ‘ 27 com volcanic bedrock, average depth 25 feet. Upper 10 feet is granular grading downward to massive ‘ 1 coral structure; clay is friable to firm, plastic to slightly plastic, and well drained. Main exposures are 26 i 2 29 hilltops, divides, and gently sloping uplands and footslopes. I 3 N a. cgral corn 2 g 21 13 coral 810 810 5 r// 22 II ' granular, friable to firm, slightly plastic, brownish clay and 30% fat, granular, very firm, plastic, ,.L I g I' \ poorly drained, brownish clay. Bedrock is the same rock of Unit 1. Scattered exposures on hill- ’ l I tows. saddles, and footslopes- I TRUST TERRITORY OF THE PACIFIC ISLANDS 8 ' (U.S.A. ADMINISTRATING AUTHORITY) x \ / SHALLOW To DEEP CLAYS 0N HARD COMPACT LAVAS Earth,1 to 10 feet deep is 70% lean, f 30 13 C“ G l C / 5 / \ a. SHALLOW TO DEEP CLAYS 0N HARD MIXED LAVAS Earth, 1 to 10 feet deep of brownish, fat and lean clays, is same as earth portion of Unit 10: bedrock is the rock of Unit 2. Scattered exposures on gently sloping upland areas. fl 27 SHALLOW T0 DEEP CLAYS ON MODERATELY HARD LAVAS Earth, 1 to 10 feet deep of brownish, ‘ fat and lean clays, is same as earth portion of Unit 10; bedrock is the rock of Unit 3. The one 19 ——T’ exposure is the gently sloping upland of Witipon, Moen. ’ 25 coral 22 09— — 809 23 SHALLOW TO DEEP LIMONITIC GRAVELLY CLAYS ON HARD COMPACT LAVAS 1 to 8 feet of \..... ........ 09 . .. .W,.... L . .L .. . . . . .. e .. -....... WNW. m... clay earth with top 1 to 3 feet containing 30 to 70% limonitic gravel; lean, brownish bottom clays \ are friable to firm, slightly plastic, and poorly drained. Bedrock is same as rock of Unit 1. Exposed \ in scattered gently sloping upland area. \ 809 ,5_5, \ 1W indicates swept depth area ir feet 28 24 29 I l I A I coral I I SHALLOW TO DEEP LIMONlTlC GRAVELLY CLAYS 0N HARD MIXED LAVAS Earth,1 to 8 feet deep is same as earth portion of Unit 13: bedrock Is rock of Unit 2. MANGROVE-SWAMP DEPOSITS Loose, coarse to fine, calcareous sand with small scattered areas of mucky earth on sandy subsoil; submerged at high tide 0.5 to 2 feet. Occurs as irregular fringe along coasts. 21 28 MARSHLAND DEPOSITS Muck and peat of various depths on sandy or plastic clay subsoils; 6 to 16 feet deep. Water table at or near ground surface. Occurs mainly on coastal plains. I N o c\\ \ n \ o .— ‘Nb—l ‘1 \ I \ 1/ Z 20 08 ‘ ,x— I ., 308 808 FILL Earth and rock fill on broad to elongate coastal flats on Moen. Param, Eten, and Dublon Island. Seaward margins protected by good to damaged seawalls of loose rock masonry or cement walls. Water table at or near sea level; fill elevations from sea level to 8 to 10 feet. Bearing 33 capacity generally excellent to good except in local muddy areas. Extensive areas surfaced with T4 good to broken concrete pavement. 20 23 I 60 61 I 62 633' 6:4 25 65 21 52 53 54 NOTE: Unit 6, CORAL LIMESTONE, and Unit 18, CORAL BOULDERS, COBBLES, AND GRAVEL, occur only 17 24d :21 on the barrier-reef and lagoonal islands. See map 8. ‘56“ l I SYMBOLS i 1 f ' ‘ 21 LL . .W... WWW. e ......WW, _.._A._.L I I 24 0 Rock sample site 8O7 . . L, .. .._WWW......_.__._.L........... . 57 m. 7 .. . .. e .W we... .. \\ 23 07 /C;\ j _ 807 F a” \15. 0 Soil sample site \ . ‘x\ 20 ‘ :1 f Wrmof Kisland) 06 \\\ : \\\ l ‘ 16 I i uarr 1 \‘~\ I 21 CD E 3‘ I X Q y 3 \ IO I I 1 24 .’ L. \ : fl 5 19 I fit Rock sample site at quarry 23 coral I L3 \ W 21 "O6 29 WW <70) I. x. 06 / "j 805 23 21 ‘ I 1 24 ‘ coral 1 17/30” — .. 3 I I 3050mm.” __ _ 25 -06 30 I coral coral I “T 17/30” 21 sand I 29 . I . . a; 23 ,I 24 , ' 29 I \ / i I I I I I I I I I / I—J 1‘ I I I t I I l I E 1 g ' s- 23 I 44 ; , 22 . ‘ ‘ I i I I I ‘ ‘\\ I I l I 23 Coral i 16 . ‘ ’ I 25 \\‘~\‘\ 23 coral I /‘ g 23, 3 ~\\\\\ I £23 15 . I, 1., 17 l 23 I f \ 24 ‘\ 7°17’OO' - I i I I I ‘xc 22 $1 151‘39’30” 352000m.E' 40/00” 353 354 355 356 357 42’30’ 358 359 360 I 30 czoeal 2 7 l 7'17’00' 36245'00” 363 3“ 365 151‘47’00" DJ p 6 p... W856 S ‘ . ‘ \ l Edmo“ Z‘AMP “”5 9 115W“ We Interpretations of engineering materials by Harold G. May and James U.S. ARMY MAP SERVICE, FAR EAST - 57.041 . R115 - 1/59 - 3.4c Prepared under the direction or the Engineer, Ho AFFE/BA, by the U.S. Army Map Service, Far ”[00 H H 52‘; H 1—40 ”00 2000 Mm“ E' Paseur, 1954'1956' East. Compiled in 1957 by photogrammetric (multiplex) methods and from 1:55.180. USHO 1000 500 O 1000 2000“!“ Chart 6049, 1944. Coastal hydrography compiled from USHO Chart 6049. 1944. Horizontal and I W... H I..__.I I._, H 1 _.q vertical control established by Corps of Engineers. 1951. Names transliterated in accordance ,L O 1N t IMI WIth rules of the US. Board on Geographic Names. Coastal vegetation are classified by reconnais— L-v— { 3” m le sance by Military Geology Branch, Intelligence Division, Office of the Engineer,Hq AFFE/BA,with personnel of the U.S. Geological Survey, 1955. Map not field checked. 1 I 1 x r I 1 L...“ _. .. W .-. , CONTOUR INTERVAL IO METERS WITH SUPPLEMENTARY CONTOURS AT 5 METER INTERVALS ”VERA“ ”"6”“ ””05““ ADJO'N'NG SHEETS Engineering materials data based on field investigations and laboratory test 1954-1955, compiled “mm“ mm" MEAN SEA LEVEL r V and prepared by Military Geology Branch. Intelligence Division, Office of the Engineer, Hq, U.S. \\ \\ Army Japan with personnel of the U. 8. Geological Survey. TRANSVERSE MERCATOR PROJECTION \\\ \ \ 4544 ll NW A HORIZONTAL DATIIM IS BASED ON THE ASTRONOMIC STATION NO. 2 (ISIS!) \ MAP 34 ' 151'53’34 3" EAST OF GREENWICH, 7'21’37.7’ NORTH ”N HYDROGRAPHIC DATUM : APPROXIMATE LEVEL OF LOWEST Low WATER LEGEND \ 4544 III SW 4544 III SE 4544 ll SW ROADS BLACK NUMBERED LINES INDICATE THE nooo METER UNIVERSAL TRANSVERSE MAP 30 MAP 32 MAP 35 A” mm“ IERCATOR GRID. ZONE 56, INTERNATIONAL SPHEROID B it THE LAST THREE DIGIYS OF THE GRID NUMBERS ARE OMITTED hard suriace two or met? lane. wIde ..W_-.WW None UII UD ar.,a ___-_...W....L.._...."WWW“... . on . x 4543 IV NW 4543 IV NE 4543 | NW louse or hghl Surlace, two cr more lanes wide ____, None Church, Schooi. Cemetery W.__.____W,W _____ ' l \ MAP 31 MAP 33 MAP §6 hard surlace. nne lane wide WWW None LImII oi danger line, Submerged reef WWWWW ..... a r loose or IIghI surlace, one lane rude W None Wreck Sunken. Exposed W WWWWW ‘ ‘5 °.'°' 0“ GRID Ion: DESIGNATION II , ~ COMPILATION ”ETHODS fan or dIy weather, louse surface, two I)! more lanes wide . . Sunken Iocls, Fmeshore Ilats W- on .‘ I!” SEN ' I IS.S2:&:;g"::::£:fFlingiagiizz Photo-stone Map m or dry nearby, louse guru-ca, one lane wide W Rucks bar: 01 awash, Reel W 3 Hits 100.000 M SQUARE IDENTIFICATION T SAMPLE POINT: 1 112 ' ‘ \\\\\\\\\‘\\V GLOSSARY I I Ck ial W____WW______ .__. _____ II n s l the VAW_ . .. Oror 3“ anchorage Car Ia , II _ Depth Curves and Son dI g In 3 ms R 1.11:"! letters Identiiyrnl 100,000 mm LP A- 1355.180. USHO Chart 5049: 19‘“ (reliablhty 3005” ”mm on can; point , 1 __+__+_4__ square In which the pornt lies, ‘ WW__W_W_.W__W.W , Standard gauge almad, smgie track ._ WW- Mm” 0am. 0m '_ _____ a» 2’ mm“mwmmuwdmm m”, Aerial photography: July 1946. Standard gauge raIIroad, double track _____A 4% LP Dam! and read LARGE figures IIDEIII‘ll the 3'." Salt evaporator: , M: author In the top or bottom numb, or I Narrow gauge IaIIIoad, smile track WWW W APPROXIMATE IEAN DELLINAIION l955 cnrhelmnseil 53 1"” FOR CENTER OF SHEET Estmnte tenl'ns ilcm (rid lme to paint: 5 "3”“ 23019 railroad, AWN? 9‘ "WWW track v~~m~ """" ' ' "‘ Rice Paddy, Marsh W_WWWW. ' ANNUAL MAImETII: CHANGE I' EASTEnLr 3. loczielrrsi HOHIIONIAL (ridline aflow . y/ "1|": pom! and read LARGE frames labeling the POWCI IIdnSmIssmn line . _._____..___.L_ . . 1 $53 Un diagram only to obtain erical values. IIrIe eIIirer m the left or ugh! warm, or ; Spot elevallcn In meters Checked, Unchecked W " M5 ‘1“ NW’ Mangrove ( “1g“; r° (“'"m‘" "gm'i‘ "m ”n" ‘W m“ Ic:0:[£:;$t::gt§teil:vtemi:;u'ortdm: Emil": l'Ishwl I1I I i 134 LL 7.1!..-“Vj ‘ H n l u . I i l t" S lml ! en 3 tom [II I!!! O DOM? Wall' levee Ch" “*7 fi [ I‘ I 9"“ P°'”' P °" N ”V." “9° °' W "W the lull coordinates Use ONLY the , , . _L ,___._._W __.~-------- I Woods. Scrub ___ _______ J LA__] with ”n valve of the angle bow GRID lARGER films: at the and number, SAMPLE REFERENCE LP535134 . , “wei L. W. W . Waterwhrel oi mill. Located otheci ¢ . b i H 71 NORTH Md MAGNETIC NORTH, a, plottedon eumol» 806000 N "can,” beyond 18' In my mmmn'l PrInpraI navIgatIan but of llghlhnuse. Anchorage WW 13‘ ~13 Iromtal grass; Coconut grove W_— LL... it i the doom scale at the north edge of th- an). L _ mm 5"” 2°" D""~'""‘°"' "1 ,56NLP535134 TOL N E, CA R0 LI N E ISLAN DS 1958 \M 7'32’00’ 832 831 830 30/00” 829 828 827 826 825 27’30’ 824mm."- 7'27’00’ TRUK ISLANDS CAROLINE ISLANDS 125,000 r? MDEN NW 0° 2° 3° 4° 5° 6° 7° LLLLLIDLLJLLLLLLJ Military Geology of Truk Islands MAP 34 Engineering Materials 1511700! 365 4730' 357 368 369 370 371 soioor 372 373 374 375 5260! 376 377 378 379 151°54’30' 7°32’OO' do? Faxnorina .‘ \l 27 \\“"/ \\ ’ , \\ CL?“ I /7_\ cgrsal $1.07 “4’51 ‘ M \‘r 22 29 ,"‘\ \°\. \ ,1'9’ \\\ 30l ’ ‘\ V \ \ \ I \ can ’ 2 13 \\ 8 \I CA2“ l, 1i \I Uncovers 1 foot *K \ /l \ sand 33:: shells ,/ \\ \\ \ // I\ coral [I \x l/ ’ 24 \\ l‘ l \\\ \‘T" 23 \32" ‘C 34 ‘I 22 \‘ coral \ a \\ \ Cora reef \I £1 24 \\ —/0 \ (LS. \\ 4 (I x \ \ / 2" “~« Q 17 ‘1 Yr“ t \ t , r‘ 5 / \\\ 5 [I 36 cgral\\ 5 /,/ 39 37 23 \L‘ 4 // Coral \\\__—,’ sand coral . 32 30 “‘T 3 2 32 832 27 coral 27 5—5, 35 33 sand 30 27 522d 36 coral 28 coral 35 ' 33 36 ENGINEERING MATERIALS MAP TRUK ISLANDS 8 ———— ’ 2’ 31 31 31 35 EXPLANATION g4 indicates swept depth area in feet 36 38 sand coral 66 UNIT DESCRIPTION 70 71 72 73 74 75 76 77 78 79 BO HARD COMPACT LAVAS Bare bedrock of uniformly hard, compact, dark.grey basalt and andesite lava flows from 35 to 160 feet thick; columnar jointing common. Exposed in cliffs. 34 coral HARD MIXED LAVAS Bare bedrock of series of hard, dark-grey, heterogeneous basalt and andesite 35 lava flows, of various hardness and composition, with scattered, interbedded, indurated, pyroclastic egg. coral 30 35 830 breccia lenses. Columnar jointing general and dikes locally common. Exposed in cliffs and on 30 rockland hillcrests. MODERATELY HARD LAVA Bare bedrock of a moderately hard, light-grey, massive, fractured cgflal £93] 23 trachyte lava flow at least 150 feet thick. Cross fracturing and a rough platey cleavage about 53"" and 5”"5 normal to fracture faces are.common. Exposed on rockland summit and cliffs of Witipon, Moen. 31 coral HARD MIXED BRECCIA AND LAVA Bare bedrock of dark-grey, very firmly bonded, pyroclastic 30 34 breccia; basalt rock blocks 1 inch to 6 feet across common; some interbedded basaltic lava; dikes sand I/ cut breccia and lava. Exposed on rocky slopes and sea cliffs of Udot and Eat. sfld [I 35 TRUK LAGOON 1’ — MIXED VOLCANIC BRECCIA AND CONGLOMERATE Exposed or partially concealed beds of per- 29 I'_ 30 00‘ clastic breccia up to 300 feet thick and conglomerate beds 10 to 35 feet thick; angular blocks I and rounded boulders and cobbles of basalt and andesite embedded in indurated matrix of volcanic \ 21 829 detritus. Main exposures in cliffs. -29 X . 30 TRUST TERRITORY OF THE PACIFIC ISLANDS 34 Carl“ .5; (U.S.A. ADMINISTRATING AUTHOR TY) 35 Q] \\\ ogre“ ' I CALCAREOUS BEACH SANDS Loose, poorly graded, fine to coarse, angular to subrounded grains 12 \ \\ 29 of coral-reef detritus. Exposed up to 2 feet above high-tide level along sand beaches and adjacent 22 533.5 I, \\\ sandy flats. Only subaerial source of sand in Truk Islands. ,x’ 31 23 ’0 \\ 1,,” sand 10 17 \\\ 31 8 SHALLOW To VERY DEEP STONY CLAYS 85% stony, lean. residual clay 1 to 30 feet deep over 0 °°"' 21 volcanic bedrock and 15% bouldery talus 1 to 50 feet deep on volcanic bedrock. Clay is granular, ,_4_9, -_- I /0 firm, slightly plastic to plastic, and moderately to well drained. 50% of clay and 50 to 90% of , I o \\ 509,8, sand / / talus are volcanic boulders and cobbles. Main exposures are the broad steeper slopes of volcanic 16 l 8 I K3 30 islands \\ coral // 15 ,’ l coral 23 8 \ / coral 28 / , 28 DEEP TO VERY DEEP RESIDUAL CLAYS Residual, lean, brownish clay 10 to 50 feet deep on X/ \\‘\ sa3n‘d \ volcanic bedrock, average depth 25 feet. Upper 10 feet is granular grading downward to massive 29 // “m" \‘x \\ ,__\\ structure; clay is friable to firm, plastic to slightly plastic, and well drained. Main exposures are Coral /’ 25 \\\ * /’ "a ‘ hilltops, divides, and gently sloping uplands and footslopes. / “ i’ i); .- 99‘?" 29 // 3),"\ ml / %) fl SHALLOW TO DEEP CLAYS ON HARD COMPACT LAVAS Earth, 1 to 10 feet deep is 70% lean, / ' "’ ‘ granular, friable to firm, slightly plastic, brownish clay and 30% fat, granular, very firm, plastic, /’ 27 poorly drained, brownish clay. Bedrock is the same rock of Unit 1. Scattered exposures on hill- /’/ tops, saddles, and footslopes. T R U K I S L A N D S /, 7 / [/K/ 4’4 j SHALLOW T0 DEEP CLAYS ON HARD MIXED LAVAS Earth, 1 to 10 feet deep of brownish. fat ,3}... ’/ ‘ and lean clays, is same as earth portion of Unit 10; bedrock is the rock of Unit 2. Scattered / exposures on gently sloping upland areas. 827 SHALLOW T0 DEEP CLAYS ON MODERATELY HARD LAVAS Earth, 1 to 10 feet deep of brownish, fat and lean clays, is same as earth portion of Unit 10; bedrock is the rock of Unit 3. The one I exposure is the gently sloping upland of Witipon, Moen. 12 29 SHALLOW T0 DEEP LIMONITIC GRAVELLY CLAYS 0N HARD COMPACT LAVAS 1 to 8 feet of clay earth with top 1 to 3 feet containing 30 to 70% limonitic gravel; lean, brownish bottom clays are friable to firm, slightly plastic, and poorly drained. Bedrock is same as rock of Unit 1. Exposed in scattered gently sloping upland area. Q‘T‘? SHALLOW To DEEP LIMONITIC GRAVELLY CLAYS ON HARD MIXED LAVAS Earth,1 to 8 feet deep ES «k is same as earth portion of Unit 13; bedrock is rock of Unit 2. 1313'! 51,33}? MANGROVE-SWAMP DEPOSITS Loose, coarse to fine, calcareous sand with smallscattered areas Egfiigi a of mucky earth on sandy subsoil; submerged at high tide 0.5 to 2 feet. Occurs as irregular fringe 826 along coasts. mwm' . . . . @695“: MARSHLAND DEPOSITS Muck and peat of varIous depths on sandy or plastIc clay subsoils, at: “IL—“‘5 6 to 16 feet deep. Water table at or near ground surface. Occurs mainly on coastal plains. /- r’” , FILL Earth and rock fill on broad to elongate coastal flats on Moen. Param, Eten, and Dublon [7’ 66 Island. Seaward margins protected by good to damaged seawalls of loose rock masonry or cement 7O / walls. Water table at or near sea level; fill elevations from sea level to 8 to 10 feet. Bearing I capacity generally excellent to good except in local muddy areas. Extensive areas surfaced with ‘, 30 good to broken concrete pavement. \ \\ 23‘\ 65 NOTE: Unit 6, CORAL LIMESTONE, and Unit 18, CORAL BOULDERS, COBBLES, AND GRAVEL, occur only \c ral , on the barrier-reef and lagoonal islands. See map 8. 325 SYMBOLS 19 OR? Rock sample site I . _ P n 057 Soil sample site °' 2790: l 06 - I, I 1 Quarr 13/ ,' 2 X y / 13 , /, fiRG Rock sample site at quarry ,II ,I/ ,‘I I, I, IO I 5‘5"" III III 61 WI IO 11 Cora; reel I .' ‘ 8 I i I 10 “.1911" 824 24 73 ,I I l “4 I 16 ', 17 I' ll 0 I I / 10 l i / com ; | 1.2 » ~ . r i «, / / ‘9 ) / & ‘ ' - 7°27roo' 151‘47’00” 366 000m.E_ 47'30’ 367 368 369 370 371 5000” 372 P 52’30’ 376 / 377 / 378 5‘ 379 151 ’54'30" 375 W855 8 Scale 125,000 Edition 2-AMS (AFFE) . , 1 % 0 15‘3“” M" Interpretations of engineering materials by Harold G. May and James U-S- ARMY MAP SERVICE. FAR EAST . 57-041 - R-15- 1/59 - 34C Prepared under the direction of the Engineer, Hq AFFE,’8A, by the U.S. Army Map service, Far East. 1000 500 o 1000 2000 Meters E- Paseur, 1954-1955- Compiled in 1957 by photogrammetric (multiplex) methods. Coastal hydrography compiled from USHO CHE-i I———-i l—-—l Ho fl Chart 6048, 1944. Horizontal and vertical control established by Corps of Engineers. 1951. Names trans- 1080 H H 5?; H H 1000 2000 Yards Iiterated in accordance with rules of the U.S. Board on Geographic Names. Major roads are classified by . . . reconnaissance by the 64th Engineer Battalion (Base Topographic), 1952; other roads are classified from 1 _ 0 lNaurIcal Mile source maps and aerial photography ahd are not verified by reconnaissance. Coastal vegetation are clas- ‘ ‘ ‘ ‘ ‘ ‘ COVERAGE DIAGRAM INDEX TO ADJOINING SHEETS sified by reconnaissance by Military Geology Branch, Intelligence Division, Office of the Engineer, Hq AFFE/8A, with personnel of the U.S. Geological Survey, 1955. Map not field checked. CONTOUR INTERVAL TO METERS . VERTICAL DATUM: MEAN SEA LEVEL 4544 ll NW Engineering materials data based on field investigations and laboratory test 1954-1955, compiled and prepared by Military Geology Branch. Intelligence Division, Office of the Engineer, Hq, U.S. TRANSVERSE MERCATOR PROJECTION MAP 34 Arm Japan with personnel of the U. S. Geological Survey. y HORIZONTAL DATUM IS BASED ON THE ASTRONOMIC STATION NO. 2 (I95l) I51’53’34.3' EAST OF GREENWICH. 7°21’37.7' NORTH 4544 III SW 4544 III SE 4544 ll SW LEGEND HYDROGRAPHIC DATUM : APPROXIMATE LEVEL or LOWEST Low WATER MAP 30 MAP 32 MAP 35 ROADS BLACK NUMBERED LINES INDICATE THE Loco METER UNIVERSAL TRANSVERSE All weather MERCATOR GRID. ZONE 56, INTERNATIONAL SPHEROID Md sum“ two N mm lanes me . Non. Bulllrup area .. - > 7 -.. None G" THE LAST maze DIGITS or THE GRID NUMBERS ARE oulrrzo ,. \ 4543 IV NW 4;;3PIV NE :21! g: loose or light surface, two or more lanes Wide None Church; School; Cemetery -.... . . , ..... _ A I lcfm‘ §\\\§\§‘\:\\\‘\\§K\:§‘\\\ MAP 3‘ 33 I I: ' . hard Surface. one ane m e NON! LImII 0i danger line, Submerged reel 0 . , COMPILATION METHODS loose or light surlace, one lane aide None Wreck: Sunken; Exposed ‘" in 0.09, 0:5 Photo-stereo Photo-planimotric Farr or dry weather, loose surlace, two or more lanes wide :7 Sunken rocks, foreshore llals ...... . . ‘ t 3W on u MILs ”'0 1°“ DESIGNATION: Tar:IzfiEAEISTgn:£A::E:FIEo:E:€T:22 W . . .. GLOSSARY 1 ,4; . law or dry weather, loose snrlace, one lane wide .. .. : r. .. :. :.:. Rocks bare or awash: Reel _ v * FT 3 “Ls 100.000 M. SQUARE IDENTIFICATION SAMPLE POINT: + SUNKEN ROCK A USHO Chart 6048 1944 (reliability good) are! on c:::"°;:‘0t , .. t, ‘ ' ' mm on . I Carl M“: If!" .- - -- -_.. ————~- Deplh Curves and Saundlnii "1 fathom: . .. .- £5 \ [Z LRead mm, Menuhin: 100.000 mm, Aerial photography: Feb., July 1946. . , hi h i . ~ Standard gauge railroad, s'me "m ' .. " .... '"T’ .. _._.—._ Reserve"; Darn, [him a‘ 2‘ fizzzlflxgyéfingffl ism“ LEFT of LP Standard gauge railroad, double track .. . .. .. LP 90ml Ind relfl URGElllures labehurlhe . 2’s” Salt evaporator: line either In the top or bottom mlflm, or Narrow gauge railroad, Singve track .,..,.-... -... APPROXIMATE IEAN DECLINAIION I955 onrhelIneItsell: 75 2"” FOR CENTER OF SNEET Estimate tenths from grid Me to point: 4 NW“ “We ”I‘m“: double 0' "WWW track Rice Paddy; Marsh ANNUAL uAGNErIc CHANGE 1' [Anna 3. Locale first HORIZONTAL grid line BELOW . fl .. I a dLARGEl lhiI Power transmissmn line “hkwwfic .-.- . / | I A'IJ Una diagram only Io obrain mlmcn'cul vulva. m" errant: the left 0:13:31! Tn:l‘lnl:,l:: S I elevation in meters Checked Unchecked ’wa x N'Dav' "WW" -- .. . .-. sxslér. To determine mogmri: nor”! lino connect rh- '°"°"E"" SMALLERMW" °""Y 9" "1° ““9 "5'”: 28 DO . . ~ . . I“ rWfi [__ _ ‘ u .. ' and number; these arr: for finding Estimate tenths from grid IInIIo point: 3 will Lever Clill *mfi I i} PM” 90"" P on th- aw”) ode- nf the man the full coordinates. Use ONLY the - . . . . --_ o ”.2 Woods; 50“,, 7 .- m», m. "I". o, ,5. War. We... cup LARGERIniuvesolmznrnumh-r: SAMPLE REFERENCE: LP764233 “define“ 0' "mi localed Obit“ 0 w ' P— I__ NORTH and MAGNETIC NORTH, a: plofhd on "amp“: 8 000 ll reporting beyond I!“ In any dIrectIon, Principal navigation light 0! lighthouse; Anchorage -.. ’5‘ xi! Tropical grass; Coconut grove . . {jg the doom Male or in. north odgl of the mp. 24 ""“G‘m 1°" °“"""‘°“"’: 56NLP754233 M OEN NW, CAROL' N E ISLAN DS 1958 TRUK ISLANDS CAROLINE ISLANDS 1125,000 MO 1E3 N S ‘W 30 40 5° 6° Lotti @111 11.11111] 7O Military Geology of Truk Islands MAP 35 Engineering Materials 151'47'00r 366 4730" 367 368 369 370 371 50/00” 372 2'30” 376 Q) 37% 1513430: - , . ‘Vr , - — s < 7‘27’00” i new . «vegan ,. ,. . ., 22 3 «‘IIIerd‘H% ~ , V is; 2 i /a%?*:*‘3 , r4 ‘( sewage 3 w , 44 13 6 17 133. OROR E N 8 823 23 ' 25 , VS?” i 23 sewn. 9v XI / Nufyisei 4: , 34 t- , 29 /’ 3 / 25 ENGINEERING MATERIALS MAP TRUK ISLANDS @ , 3 UCLA ROAD ’__- ....... —— ’ 11 (OROR EN NEPUN 21 Meg—“T” o x- I EXPLANATION ‘2 " ’ \ ‘ / 19 1’ 31 822 I: g 1 / ‘ ' 5537'" 822 UNIT DESCRIPTION '3, 00"" 16 /, UP // oral ,// ' HARD COMPACT LAVAS Bare bedrock of uniformly hard, compact, darkAgrey basalt and andesite ll / /” lava flows from 35 to 160 feet thick; columnar jointing common. Exposed in cliffs. \i , al / 23 /’ \\\ oral 0/" 5 / sand I” HARD MIXED LAVAS Bare bedrock of series of hard, dark-grey, heterogeneous basalt and andesite w 78 ” 79 ‘5; 66 lava flows, of various hardness and composition, with scattered, interbedded, indurated, pyroclastic /, breccia lenses. Columnar jointing general and dikes locally common. *Exposed in cliffs and on J/ rockland hillcrests. // x” 33 / ’ coral MODERATELY HARD LAVA Bare bedrock of a moderately hard, light‘grey, massive, fractured /, trachyte lava flow at least 150 feet thick. Cross fracturing and a rough platey cleavage about 321 17 normal to fracture faces are common. Exposed on rockland summit and cliffs of WitipOn, Moen. w 821 HARD MIXED BRECCIA AND LAVA Bare bedrock of dark-grey, very firmly bonded, pyroclastic breccia; basalt rock blocks 1 inch to 6 feet across common; some interbedded basaltic lava; dikes , cut breccia and lava. Exposed on rocky slopes and sea cliffs of Udot and Eat. I " 30 MlXED VOLCANIC BRECClA AND CONGLOMERATE Exposed or partially concealed beds of per- sngd clastic breccia up to 300 feet thick and conglomerate beds 10 to 35 feet thick; angular blocks and rounded boulders and cobbles of basalt and andesite embedded in indurated matrix of volcanic detritus. Main exposures in cliffs. 24 , 1,,— CALCAREOUS BEACH SANDS Loose, poorly graded, fine to coarse, angular to subrounded grains ‘, 63%| ,x" of coral-reef detritus. Exposed up to 2 feet above high-tide level along sand beaches and adjacent \, “m" // sandy flats. Only subaerial source of sand in Truk Islands. \ / 8 820 I. ’1 13 E— 229 r' 25'00” 8 SHALLOW TO VERY DEEP STONY CLAYS 85% stony, lean, residual clay 1 to 30 feet deep over i i: " ' 5 00 volcanic bedrock and 15% bouldery talus 1 to 50 feet deep on volcanic bedrock. Clay is granular, 3 \ 3 Coral firm, slightly plastic to plastic, and moderately to well drained. 50% of clay and 50 to 90% of Q; sand \\ talus are volcanic boulders and cobbles. Main exposures are the broad steeper slopes of volcanic i \\0\ islands. \\ l5 DEEP TO VERY DEEP RESIDUAL CLAYS Residual, lean, brownish clay 10 to 50 feet deep on ”'3' volcanic bedrock, average depth 25 feet. Upper 10 feet is granular grading downward to massive _- structure; clay is friable to firm, plastic to slightly plastic, and well drained. Main exposures are // \ 'Coral. \51 l / hilltops, divides, and gently sloping uplands and footslopes. 17 K/ II 4>,’ L33 // 24 i““l\ Z l /’ ‘ I SHALLOW TO DEEP CLAYS ON HARD COMPACT LAVAS Earth 1,to 10 feet deep is 70% lean, ifs \ _, 12‘ / . .. m 23 granular, friable to firm, slightly plastic, brownish Clay and 30% fat, granular, very firm, plastic, 5"" 3".” SM": "99' on/Noadwo 319 _»____ poorly drained. brownish clay. Bedrock is the same rock of Unit 1. Scattered exposures on hill- I ” ‘ ’ 819 tops, saddles, and footslopes. \\ \ 33 \ 22 SHALLOW TO DEEP CLAYS 0N HARD MIXED LAVAS Earth, 1 to 10 feet deep of brownish, fat ‘\ _________ ”'3’ and lean clays, is same as earth portion of Unit 10; bedrock is the rock of Unit 2. Scattered exposures on gently sloping upland areas, 5F l W SHALLOW T0 DEEP CLAYS ON MODERATELY HARD LAVAS Earth, 1 to 10 feet deep of brownish, |\\ 9 l 17 29 .- x If . :4 fat and lean Clays, is same as earth portion of Unit 10; bedrock is the rock of Unit 3. The one 9 \x‘Z_/\ 32 exposure is the gently sloping upland of Witipon. Moen. ‘51] - “so ' * 16 23 12 k @ SHALLOW TO DEEP LIMONITIC GRAVELLY CLAYS 0N HARD COMPACT LAVAS 1 to 8 feet of 25 5 clay earth with top 1 to 3 feet containing 30 to 70% limonitic gravel; lean, brownish bottom clays are friable to firm, slightly plastic. and poorly drained. Bedrock is same as rock of Unit 1. Exposed 3‘ 22 818 in scattered gently sloping upland area. 20 818 SHALLOW TO DEEP LIMONITIC GRAVELLY CLAYS 0N HARD MIXED LAVAS Earth,1 to 8 feet deep is same as earth portion of Unit 13; bedrock is rock of Unit 2. MANGROVE-SWAMP DEPOSITS Loose, coarse to fine, calcareous sand with small scattered areas 18 l T R U K i S L A of mucky earth on sandy subsoil; submerged at high tide 0.5 to 2 feet. Occurs as irregular fringe i mg m TRUST TEFI ITORY OF THE PACIFIC lS :‘L — MARSHLAND DEPOSITS Muck and peat of various depths on sandy or plastic clay subsoils; (U SIA ADMINISTRATING AUTHORITY) ‘IiJC‘T 6 to 16 feet deep. Water table at or near ground surface. Occurs mainly on coastal plains. ’ I 17 I7 FILL Earth and rock fill on broad to elongate coastal flats on Moen, Param, Eten, and Dublon l Island. Seaward margins protected by good to damaged seawalls of loose rock masonry or cement : 317 walls. Water table at or near sea level; fill elevations from sea level to 8 to 10 feet. Bearing 17 817 13 capacity generally excellent to good except in local muddy areas. Extensive areas surfaced with 15 good to broken concrete pavement. i 4+» 18 21 ‘ I/" \ NOTE: Unit 6, CORAL LIMESTONE, and Unit 18, CORAL BOULDERS, COBBLES, AND GRAVEL, occur only ,/ iii on the barrier-reef and lagoonal islands. See map 8. \ 8 A \ \ ‘ \’ \\ l / AL 9 17 72 , i 65 SYMBOLS 7) , 7 / >7) / IO/ ' , R7 0 - 15 10 0 Rock sample Site I k%a/‘ 087 Soil sample site , 8 816 5606 Quarry 16 R6 ’381‘ Rock sample site at quarry COTII—I 12 22/30” 22/30r ,/W\_/ro, M Edgy/(CHOP! ()0 (fl ref-N5 815 8150 m.N_ ET ,1 23 1’ coral ETEN ANCHORAGE // (Mfg/“x ogre! ,’/ g 17 o\\ ,7 / 7T22'oor . l " ’ 7°22/00" 151’47’00” 366000m.E_ 369 371 50’00” 372 52'30II 376 377 378 379 151'54’30” W856 5 Scale 125,000 Ed‘m" “Ms (AFFE) 1 E o IStatute Mile interpretations of engineering materlals by Harold G. May and James U.S. ARMY MAP SERVICE, FAR EAST - 57-041 - R-15 - 1/59 ~ 3.4c 1000 500 5""; 1000 000'“ E. Paseur, 1954-1956. Prepared under the direction of the Engineer, Hq AFFE/8A, by the U.S. Army Map Service, Far East. I 2 eers Compiled in 1957 by photogrammetric (multiplex) methods. Coastal hydrography compiled from USHO 1000 500 0 1000 2000 Yards Charts 6048, 6050. 1944, Horizontal and vertical control established by Corps of Engineers, 1951. Names l I-—I T—l IEZEF !-—-I transliterated in accordance with rules of the U.S. Board on Geographic Names. Major roads are classi- 1 5. 0 N , _ fied by reconnaissance by the 64th Engineer Battalion (Base Topographic), 1952 and reclassified from E 1 wheel Mlle H E aerial photography dated 1955; other roads are classified from source maps and aerial photography and COVERAGE DIAGRAM INDEX TO ADJOINING SHEETS are not verified by reconnaissance. Coastal vegetation are classified by reconnaissance by Military Geology Branch, Intelligence Division, Office of the Engineer, Hq AFFE/SA. with personnel of the U.S. Geological CONTOUR INTERVAL IO METERS \V‘ \\\\\§\x\§\§: Survey, 1955. Map not field checked. VERTICAL DATUW MEAN SEA LEVEL 0§1§§$ 7' 4544 ll NW . . . "1}“, i“: ’ Englneerlng materials data based on field investigations and laboratory test 1954-1955 compiled ‘\\\§“\\\\' MAP 34 . . ' \ . and prepared by Military Geology Branch. Intelligence Division, Office of the Engineer, Hq, U.S. TRANSVERSE MERCATOR PROJECTION \ -‘\\ \~\\\ \\ ‘ Army Japan with personnel of the U.S. Geological Survey_ HORIZONTAL DATUM IS BASED ON THE ASTRONOMIC STATION No. 2 (IBM): \ 15I'53’34.3' EAST OF GREENWICH, 7'2l’37,7’ NORTH ' LEGEND 4544 ll! SW 4544 III SE 4544 ll SW HYDROGRAPHIC DATUI: APPROXIMATE LEVEL OF LOWEST LOW WATER MAP 30 MAP 32 MAP 35 ROADS BLACK NUMBERED LINES INDICATE THE 1.000 METER UNIVERSAL TRANSVERSE All weather MERCATOR GRID. ZONE 56. INTERNATIONAL SPHEROID hard surface m 0' more lanes old: .- LAuu Built-up are: THE LAST THREE DIGITS or TN: GRID NUMBERS ARE OMITTED 4543 IV NW 4543 N NE 4543 I NW loose or light surlace, lvro or more lanes lit __ " “N" Church; School; Cemetery G" MAP 3' MAP 33 MAP-‘6 hard surface, one lane wide — Limit of danger line; Submerged reel loose or light surlace, one lane rude m Wreck: Sunken; Exposed 0.09, 4.”, Photo-stereo Photo-plonimetric Map Fail or dry weather, loose surlace, two or more lanes wide Sunken rocks; foreshore flats on GRID ZONE DESIGNATION: To cw: A STANDARD REFERENCE 0N \\ on This snEET To NEAREST loo METERS m GLOSSARY Fair or dry weather, loose surlace, one lane wide ======== flocks bore or arrasll' Reel 3 MILS ‘4 "”5 DENT E c ~ Nom on In . Iod,ooo M. SQUARE I l I ATIDN SAMPLE POINT. ; SCHOOL A USHO Chart 6048 19“ (reliability good) 0 V Cant chill .. .. . ‘ ' . .. ' for on ‘ do n ,, Depth Curve: and I“ Fathom: Hm Mm identilyiu 100.000 mm, B. USHO Chart 6050, 1944 (rellablllty good). Unun on capo, point Standard gauze railroad. single track -—l—r——i-— R ., D , Ditch sonarein which the point lies: LP Aerial photography: Fob., July 1946. . eservolr, ml, 2, Locnta lirstVERTICAL [rid line to LEFT 0! Standard gauge railroad, double mail I U S if LP point and rend LARGE rigures labellnl the I. I ' ’ "3"“ 83““ railroad, single "m I ” APPnoxmATE IIEAN DECLINATION loss 3:153:11'353309"mm mum.“ 78 . . ’ ‘ _ FOR cenren or SNEET . Esllmatetonthslrom grid line to point: 1 "3"" 13“" ”mm mm” °' multlole "u" ""_"'_""'l RIO! Ptddr: Marsh ANNUAL “some CHANGE l’ EASYERLV 3. Locate first NORIIONTAL grid line mow Power transmission line _________ / u d, _ , ooh-i and read LARGE llgurzs labeling tho . ‘ .. 1e Iagram only to cblarn numerrcal values. line either In the left or nzht mourn, or Soot elevation In meters: Checked; Unchecked x I“ ma "'W- To determine magnelic north lino, conned the mum“? élxlm "tremor on the line use": _ _ . 15 Wall; Lem; Cliff _.___—_ __Wg/i§ Woods Scr h pivol point “P" on Ihe south edge of the map a: rmnloz:am:: 11;:le :2: Estlmntetenthslrom grid linoto ”I": 8 : ll " Walemlleel ol mill; Located object Principal navigation light of lighthouse; Anchorage __ * i; or Ol'ollrer Tropical grass; Coconut grove with the value of the angle between GRID NORTH and MAGNETIC NORTH, as planed on the degree scale or the north edge of the map. [ARCH "In"! 0' "N If“ WWW"; SAMPLE REFERENCE: LP781168 example: 315 000 ll reporting beyond 18' in any direction, _ prolix Grid lono Designation, as: 56NLP73116_8_I 1958 MOEN SW, CAROLINE ISLANDS TRUK ISLANDS CAROLINE ISLANDS 125,000 Military Geology of Truk Islands MAP 36 Engineering Materials UMAN NW 3 . 151-47'001 366 47/30” 367 368 369 370 \Q: 371 50100” 373 79 151 54,30” 7-2200” _, . , / 7‘22’00” \ .. I I -. / 2 {14d 5 10 17 Lo/ 23 ,, 23 san / 6? I 6:}, 10 1 / Coral f .51 7/ OROR EN U 0 T g ,x' r / ® U W \ .1 ”£1“le ANCHORAGE , ft) \{3‘ ’ ““““““ 4. ’ 19 1 17 coral 3 * flUncoverLl foot/2 8 814 (W 8 . , 1. 14 * z . XX /’ 8 \\ Q / r x x CI / 7aiyynun ark 50mg. _ on ’3an /~_/12 g \‘xé—ZJ \éo%5‘ , /" 7@ ’ 508* “s3 ’ Cora I\ 21\ {[11 \e f / 9 \ 0‘ , 2 I / If ’ 17 cor-l b‘xgoral reel \‘0 1 ,, coral ‘ 'N.-l \ \ 35-33 {7-1}, a " swuwhy,“ \ ”if 1 out ,0, / ‘. R . W’fig} u \ \ l [(7) I r . j x , . YLfi ‘EEAKS- fi/gflg %@ \ s 17 ‘ 19 813 . , fez}, , . , 7_ s I~ I , oral 813 i ~ \Q a $er 3,...3syncoveIW ., 3% c ‘1" W coma » . I , ~ .12.. ”‘6 Ix : L~~J/ " r375,\\ Er{2 fee , 3 - o ‘ ~ ‘ 'ncovers ,- 8 Q or: 12 (a 15I@,.}, root ' coral \ a cornt‘cyléllil \ 5'0 79 , Cor l 1 I 20 I 12 12 \ I, I I coral l I . :19; I 6. . ' x i an I ’ -~ ' I. / ENGINEERING MATERIALS MAP TRUK ISLANDS Unwvers 2 fun I I l I 5:. - ' . 9 l I | /, .:",', 1 l I l I 312 ." ”‘x \\ n K i l . I 812 I ’/ EXPLANATION N “”0 E” I" l' 'I 23 32 1 I I I coral 26 coral 6 I I ‘ coral .s—JO/ 4 \ ,‘ l DESCRIPTION 10 1 hog um,” . ncovers 3 leet m/ 16 ,0. ‘I' / ,‘13f / I» I ,’ licoral HARD COMPACT LAVAS Bare bedrock of uniformly hard, compact, darlcgrey basalt and andesite 10 ’,\ / 22 (,I I/ sign lava flows from 35 to 160 feet thick; columnar jointing common. Exposed in cliffs. ,6 13 l 18 / s-nd / / It A“ sand // I [I \\\\ ’/ lI I \\ \“\~ HARD MIXED LAVAS Bare bedrock of series of hard, dark-grey, heterogeneous basalt and andesite 1 ] /// .' “i l \\\\ sb55\\ Coral lava flows, of various hardness and composition, with scattered, interbedded, indurated, pyroclastic 3265 l 20 x ; [I on ‘Txg’f‘océassgx‘ 13 (if: 6 breccia lenses. Columnar jointing general and dikes locally common. Exposed in cliffs and on D 2 "’ =Ai \ 11' 1 J Sign \ss \“ssL \ coral I/ A 811 811 rockland hillcrests. 7 1 \\ 22 [I [I \\\ _\\‘ Uncovors I‘loot 22 LJ 15 I \, coral ,' 1 ‘\~\‘ ‘S \\ ‘~— / Hv ’ \»\\ \\\\ b 5 MODERATELY HARD LAVA Bare bedrock of a moderately hard, light-grey, massive, fractured I, ‘ // 1s (/57, \L“ ‘x\\ _ 20,00” 20'00” —- cm" 15 1 ' trachyte lava flow at least 150 feet thick. Cross fracturing and a rough platey cleavage about / Ig/ ‘~\\ \5‘ 54 / ISI 0 so normal to fracture faces are common. Exposed on rockland summit and cliffs of Witipb‘n, Moen. / I A, /:& ‘ V“ / ,3, 9) 29 \\ n ‘ V :63} II I . \ .. v . I I ”24,77 ------ _ _ . .4... HARD MIXED BRECClA AND LAVA Bare bedrock of dark-grey, very firmly bonded, pyroclastic / $5,; ,I fit? ,1 ,I’ [I 18 °”’ /(//— ‘ :r; . . breccia; baSalt rock blocks 1 inch to 6 feet across common; some interbedded basaltic lava; dikes 1 fig?) 6; 95,: r I’ ’2'? 5“ ‘ [I [l cm. / coral cut breccia and lava. Ex osed on rock slo es and sea cliffs of Udot and Eot. 15 . I , ‘ l I’ i . p , p > , 12 $11., ’f it ,3 I 15 I TRUST TERRITORY or THE PACIFIC ISLANDS . r, , ‘. I, MIXED VOLCANIC BRECCIA AND CONGLOMERATE Exposed or partially concealed beds of per- l ,0 WI ~ 'I' o /, II’ (U.S.A. ADMINISTRATING AUTHORITY) 3] 55 ciastic breccia up to 300 feet thick and conglomerate beds 10 to 35 feet thick; angular blocks ,5 2 ‘ x " . ” if; un 0" FUIMIOHO / 6 L4 and rounded boulders and cobbles of basalt and andesite embedded in indurated matrix of volcanic 12 1 > ,3.” ‘ ,' detritus. Main exposures in Cliffs. 3 33.4% I ,' 810 810 , u 12 10 .. .. .. we? »' go; :' :«n CALCAREOUS BEACH SANDS Loose, poorly graded, fine to coarse, angular to subrounded grains (10 OROR EN KUKUWU ,‘gffi . W3" II send and shells of coral-reef detritus. Exposed up to 2 feet above high-tide level along sand beaches and adjacent , 12 A534 {I}? 17 I sandy flats. Only subaerial source of sand in Truk islands. Viké A , Adi, U f l 21 at???» ‘I’AA ” W I 33 SHALLOW To VERY DEEP STONY CLAYS 85% stony, lean, residual clay 1 to 30 feet deep over Fgfig’fgflk 15 volcanic bedrock and 15"0 bouldery talus 1 to 50 feet deep on volcanic bedrock. Clay is granular. ig’s’gséI/{é’}, I firm, slightly plastic to plastic, and moderately to well drained. 50% of clay and 50 to 90% of Zéygfjéfi, T R l I Pi L A G O 0 N talus are volcanic boulders and cobbles. Main exposures are the broad steeper slopes of volcanic 19 fiwf/gflé if . I / \Ef/‘r’ \ islands. ’rgiééwfl #1,?! ”L5 41 ‘»»\\\ E‘ 1 13 y W ,. / g\ DEEP To VERY DEEP RESIDUAL CLAYS Residual, lean, brownish clay 10 to 50 feet deep on , /. 2:~ 23 12 {wz’é’yl// \ I 5; volcanic bedrock, average depth 25 feet. Upper 10 feet is granular grading downward to massive \ IE1), g; 2.34 \ 2} 1 3“ng 12 5]) 12 structure; clay is friable to firm, plastic to slightly plastic, and well drained. Main exposures are \\.°f_a_-/ \,_ \\ o Swag-f2 . .‘ _,—Io / 35 809 hilltops, divides, and gently sloping uplands and footslopes. \ l/D; g' \ 13 2 A 3%,???‘3 17 /, 309 I I I ha- , m, , . I SHALLOW TO DEEP CLAYS ON HARD COMPACT LAVAS Earth,1 to 10 feet deep is 70% lean, I 24 ("If 5’ ‘1 / 18 u in . fi’ésap ‘ EIPIOTA granular, friable to firm, slightly plastic, brownish clay and 30% fat, granular, very firm, plastic, L532 // .154, \\ 2 7” $3 2 I I poorly drained, brownish clay, Bedrock is the same rock of Unit 1. Scattered exposures on hill- _____ ‘/ \\ \Q; J” 1.2 tops, saddles, and footslopes. ““xssu‘ ‘\ 22 8 g“ lUnun on Chukusirip 28 ‘\ \ o I A 3 \ x 1 \ [I 30 W % SHALLOW To DEEP CLAYS ON HARD MIXED LAVAS Earth, 1 to 10 feet deep of brownish, fat 14 \\ 18 \\ y/ / 1’ a and lean clays, is same as earth portion of Unit 10; bedrock is the rock of Unit 2. Scattered , \ \ . z ,/ 12 exposures on gently sloping upland areas. \\ Unhn In Nepwasu 3 [X shzeIls 1 \\\ 24 3.3; s \ I\ 2 18 ,r/ 36 fl SHALLow To DEEP CLAYS ON MODERATELY HARD LAVAs Earth, 1 to 10 feet deep of brownish, I, \x o\\ coral fat and lean clays, is same as earth portion of Unit 10; bedrock is the rock of Unit 3. The one "U" M 0’13""9 I 6: [III 18 ’ 3-2: 23 exposure is the gently sloping upland of Witipon, Moen. KEN-111 ‘, 22/76“ / ‘ . \ x/ \ \. a 808 W SHALLOW TO DEEP LIMONlTlC GRAVELLY CLAYS ON HARD COMPACT LAVAS 1 to 8 feet of 08 \ IW 19 x 08 s 3%th clay earth with top 1 to 3 feet containing 30 to 70% limonitic gravel; lean, brownish bottom clays 15 \ I~e__/ °°"' \\ are friable to firm, slightly plastic, and poorly drained. Bedrock is same as rock of Unit 1. Exposed ‘ \ In scattered gently sloping upland area, 377 53,30” 378 379 151°54’30” ) / t\\ 31 o r [I o / . , o \ w SHALLow T0 DEEP LlMONlTlC GRAVELLY CLAYS ON HARD MlXED LAVAS Earth,1 to 8 feet deep 7 17 0° fake 13a“ % I 7 1700’ I", , 11 \ x“ § \ is same as earth portion of Unit 13; bedrock is rock of Unit 2. Dvssssy . V , _. . \\ 66 11/] , ‘ " <3 (I! AMI" Liand « ' ‘ , ,If ' Unun o Nukanapx‘clo?“ ', ‘ MANGROVE-SWAMP DEPOSITS Loose, coarse to fine, calcareous sand with smallscattered areas 805 305 ‘ \\ 23 \\\s\ " of mucky earth on sandy subsoil; submerged at high tide 0.5 to 2 feet. Occurs as irregular fringe \\ 5; \\ along coasts. \\ QROR EA; ll/IUKANAP ‘I .3... _ I 3 l Fats—L“; MARSHLAND DEPOSITS Muck and peat of various depths on sandy or plastic Clay subsoils; \\ ‘ 27 \ :—“““_,,.._-u-—— 6 to 16 feet deep. Water table at or near ground surface. Occurs mainly on coastal plains. 0‘7 It 807 8 . — I 07 ., IT 3 FILL Earth and rock fill on broad to elongate coastal flats on Moen. Param, Eten, and Dublon \‘I II , island. Seaward margins protected by good to damaged seawalls of loose rock masonry or cement I I 17 23 walls. Water table at or near sea level; fill elevations from sea level to 8 to 10 feet. Bearing 15 I 2 III capacity generally excellent to good except in local muddy areas. Extensive areas surfaced with I. , (I good to broken concrete pavement. \ -, . ‘ ‘ , I I ' \ 25 I ,V t ' ,' , _ , 0W NOTE: Unit 6, CORAL LIMESTONE, and Unit 18, CORAL BOULDERS, COBBLES, AND GRAVEL, occur only l 804 , 1 . .. . '., ‘ ' ' SAPOTIU \\ on the barrier-reef and lagoonal islands. See map 8. l _ -’. a , ' . 1 ,. 7 7 G ‘I I E. ‘ U é} f133 ’ SYMBOLS ,"UV" / no w — I / / 17'30” 1730” R7 . / 7 \jg . 0 Rock sample Site / // Ir 8 8 00° 19 S7 27 I6— ’ I It. ' . . 4 g. I / ,r 21 I I 06 06 m.N_ 0 Soil sample site / ’ ’ '- \“ ‘ '-‘ ' . "" /\4_5J/ SW“ II 3 / I / .. . ‘ ’ // \\ 06 I / 1600” ~—‘ MAM 16/00” ’ l . - -» (/ \N X Quarry , Faneu Island / 5 = / \ / / / , .; . ‘ 1’ x 21 s r , G . \ i, . . 19, jitRe Rock sample site at quarry \32 // l/ f?” , WWI 7m "M's // ‘ . / I ., , é; / l/ 803000m. u, “AAA-$37252?” I ,/ l/ ’ 22 31 I 33 30 L5; 7'17’00” ' 7'17’00” 151°47’00” 366000m.E 4730” 367 368 369 370 377°00m> E. 53’30” 378 379 151°54’30” 5230” 376 37g 151‘54’30” wess 5 Scale 1:25000 . 1 . . . . Edition 2AMS (AFFE) 1 E 0 IStatute Mile Interpretations of engineering materials by Harold G. May and James us, ARMY MAP SERVICE, FAR EAST . 57.041 . R-15 .1/59. 3_4c E " * ' E. Paseur 1954-1956. Prepared under the direction of the Engineer, Hq AFFE,8A, by the US. Army Map Service, Far East. 1000 500 0 1000 2000 Meters ' Compiled in 1957 by photogrammetric (multiplex) methods. Coastal hydrography compiled from USHO I 1;; I I PS—OIO H {0 10001 ZOOOYId Charts 6048, 6050. 1944. Horizontal and vertical control established by Corps of Engineers, 1951. Names l H H ,_' H H L fl ar 5 transliterated in accordance with rules of the US. Board on Geographic Names. Major roads are classi- 1 0 IN f IM‘l fied by reconnaissance by the 64th Engineer Battalion (Base Topographic), 1952 and reclassified from au ":3 ‘5 aerial photography dated 1955; other roads are classified from source maps and aerial photography and g ‘ ‘ ‘ 1 ‘ COVERAGE DIAGRAM INDEX TO ADJOINING SHEUS are not verified by reconnaissance. Coastal vegetation are classified by reconnaissance by Military Geology “w““w \ Branch, Intelligence Division, Office of the Engineer, Hq AFFE/BA, with personnel of the US. Geological CONTOUR INTERVAL IO METERS WITH SUPPLEMENTARY CONTOURS AT 5 METER INTERVALS W Survey, 1955. Map not field checked. VERTICAL DATUM: MEAN SEA LEVEL "“\\ 4544 " NW Engineering materials data based on field investigations and laboratory test 1954-1955, compiled MAP 34 and prepared by Military Geology Branch, Intelligence Division, Office of the Engineer, Hq, u.s. TRANSVERSE MERCATOR PROJECTION Army Japan with personnel of the US. Geological Survey. HORIZONTAL DATUM lS BASED oN THE ASTRONOMIC STATION NO. 2 (l95i) 151'53’34.3” EAST OF GREENWICH. 7'21’37,7” NORTH 4544 I” SW 4544 ”I SE 4544 ll SW LEGEND HYDROGRAPHIC DATUM: APPROXIMATE LEVEL OF LOWEST Low WATER MAP 30 MAP 32 MAP 35 ROADS BLACK NUMBERED LINES INDICATE THE 1.000 METER UNIVERSAL TRANSVERSE "I mm" MERCATOR GRID. ZONE 56, lNTERNATlONAL SPRERoID 4543 Iv Nw 4543 N NE 45431 Nw hard surlace, two or more lane: wide _____ fl.- Builtup are: __~______1__. 6" TR: LAsr THREE DIGlTS or THE GRlD NUMBERS ARE OMITTED MAP 3‘ MAP 33 MAP 6 loose or light surllce, lvro or more lanes wide A,_ -’=lfléus- Church; School; Cemetery #_._ hard surface, one lane wide __,,____,-. _ Limit ol danger line; Submerged reel __ ' COMPILATlON METHODS loose or light surlnce, one lane wide ___ - “- Wreck: Sunken; Exposed *L__._.__ 0.”, 40:5, Photo-stereo Photo-planimetric Map GLOSSARY , . _ GRID ZONE DESIGNATION: To our: A STANDARD REFERENCE on W :» (:l L F1" or dry weather, loose surface, two or more lanes wide ———-——— Sunken loclls, Foreshore ilols 3 ZR 94 NHL: 55" "“5 SHE“ To NEAREST 10° mums . grour en as: ’3" 0' “TY "Emu-10°59 “who"! ""e “49 ———— :======= Rocks bare or MS": Reel ..._77A...AA_W "'5 loom M. SQUARE loENTifICATloN SAMPLE pom; t CHURCH A_ USHO Chart 6048, 1944 (reliability good). “ “ "I ““‘I 9““ Cart track; trail __w. ___._. __-___ Depth Curves and Soundings in Fathom: ___L__ Lind Imm “Emmi“ mm mm 3- I-ISHO Chart 60.50. 1944 (reliability 800d). squarein whicblho polnlllesz LP AerIaI photography. Fab-I July 1946. Standard gauge railroad, single track , —-t——-l—l— Reservoir Dam' Ditch Standard gauge lzilroad, double tracll ___ —*—ll—-*- . ‘ 2"” Salt evaporator: v_____ Narrow gauge rariroad, Single track *k -v—"-—v-— ,,‘Ir Narrow gauge railroad, double or multioh tuck Rice Paddy; Marsh Power transmission line MA_ _________ ,” [:1 Spot elevation in meters: Checked; Unchecked ____, " us "11.5 "I”? "Mm" ________..,___ Wall; Levee: Cliff w__ _.._..§A§ A Woods; Scrub “EH—cf. Wltemheei oi mill; located object ELEVEW o onv Principal navigation light oi lighthouse; Anchorage H * \1/ iropical grass; Coconut grove W___. [::II:] APPNOXIMAYE MEAN DECLINATION 1955 FOR CENTER OF SHEET ANNUAL MAGNETIC CHANGE I' EASYERLV U. diagram only to obtain numn'ml valves. To determine magnofic north lino, connect the pivot point "P" on tho booth dye of Ibo mm with ”to value of the angle between GRID NORTH and MAGNETIC NORTH, as plan-d on "be doom scale of my north edge of tho map. 2. Locate first VERTlCAL grid line to LEFT of point and road LARGE figures IIDBIIHI the LP lino either In the top or bottom margin, or on the line itself: 71 Emma“ tonlhs from grid line to point: 3 3. Locate first HORIIONTAL grid line BELOW point and lead LARGE llgures labeling the line ollhor In the left or right margin, or lGNORE [In SMALLER figures or any on III. IIn. itself: 12 l'ifl "MW"? "'85! I" for finding Estimate tenths from grid line to point: 2 the full Coardlnntes. Us: ONLY the LARGER Mom M "In M numbvr: sAMPLt llthnENCE: LP713122 9""‘9"; 8 000 ll reporting beyond la‘ In any direction, Q6 UMAN NW, CAROLINE ISLANDS prolix Grid Zone Damnation, IS: SSNLP713122 1958 TRUK ISLANDS I V V V A A, iia oo 0 Tu san s CAROLINE ISLANDS 1:25.000 LI ID (I II S W 0° f; 313$; f 3113338IRZIISIIIIkIIII'IIeIZS 151°32Ioor 339 32/30” 340 342 343 , 35'007 344 345 346 347 348 37/30II 349 350 351 151°39'30" ° 1 If 7°27100II I I I 5\—I // I I \O\IV //, 30/7\ 7 27 00 I . / ao 30 \‘ " \ I K/SZ I 22 W, ; coral 822 22 m ””””””””” Dry level coastal areas of sandy flats and rock and earth fill, barrier»reef islands, and the four \\ ‘52 \\ “114 EXCELLENT UNSUITABLE GOOD Japanese-built airfields; elevations 1 to 10 feet above sea level. Extensive stands of coconut and "if"_______"v:___::’i““ufi": » 7-8 (only because breadfruit on the sand and grass, brush, and some coconut on the fill. Some fill, clearing, and 777777 I """""""""""" ‘ _______ I 0f SIZE) drainage required. I 77777777777777777777 285 Scattered upland flats on slopes, plateaus, and crests of highlands; subgrade mostly clay and 44 29 4, 27 41 GOOD UNSUITABLE GOOD some rock. Scattered stands of coconut, natural forest, and brush and sizable grassy areas. 24 coral Some clearing, blasting, and bridging required for roads. W’a' _ 26 ”26'” ’ I 4/4 cora T R u K , 8 821 Broad extensive areas of moderate to steep terrain on hillsides: subgrade mostly clay and some 21 FAIR UNSUITABLE UNSUITABLE boulder talus. Scattered stands of coconut, natural forest, and brush and extensive areas of dense 3} reed grass. Cut and fill, clearing, and drainage required. 2 32 I coral 23 Z; I 'I 18 coral 28 I I. . . Jr’xx/ .- -c I1», ‘3 Broken or long smuous rocky escarpments and some very steep earth slopes; subgrade bedrock I [La/T” ‘ I Pr? ' 2: POOR UNSUITABLE UNSUITABLE and some areas of clay and boulder talus. Extensive stands of natural forest and scrub. Road I “2.77"” ,» lilslari ’ 19 construction requires blasting, cut and fill, clearing, drainage. and possibly tunneling. ,x/ "x - A I//:- \\ COIZI 30 ,,//’r 15 I z; ‘I , , ' I . II 26 22 , ,, 25:00: _ I _ f Mangrove swamps and marshes on coastal lowlands. Swamp bottom is loamy sand and some 29 \X 51:4 1/,4x/ —— 25 coral W 25 00 820 . 5- . POOR UNSUITABLE UNSUITABLE muck; in marshes, organic muck in places 16 feet deep over clay subsoil. Raised rockfill road. 20 ‘ 25 74,7 V 20 26 820 I I ' * beds required in swamps and rock-fill displacement of muck in marshes. ,,.5\ IO'\ ’47’/,// I coral / ‘I I ,x” I6); 18 Q I ”7/7,, I |\\ 7/ 30 I 26 ,— 1/”/ j 1 a L 1( I 11 x I 31 \ x p ///‘ 1‘ ----- / I 1/” I I5 24 Coral ,— . x 19 , 21 r 24 5 29 . /,, 0 % 2 5 I '/ 21 , xxxxxx 2 O TRUST TERRITORII 0P THE PACIFIC ISLANDS , <8) 23 WIHIISIIIII 22 24 29 (U.S.A. ADMINISTRATING AUTHORITY) 12 ® ‘3 23 /I° ,/'“// 31 //// _ 1X 11 27 819 ”A L. E, ,.,,.L ,.. E l // . I” ""7 7" .,,. I 7 W" H 7 7 I i 19 819 19 28 19 23 I 22 23 20 //.r 24 £11 I /,,// 21 27 4,7 /"’ 21 Coral /-/e/”‘ ’/ 17 I 21 29 24 ’4’/,/’// coral I 23 lo 7/” 5‘ x,/ ’ r 11 . ‘ L4 indicates swept depth area in feet /,,~/‘/ 23 15 1.4/35, 18 I I 17 //"// 21 I Coral 818 II 18 " I I8 W??? ‘° ~ Ax/ , I I 15 a 2 \IOr floora , :',"',{:C°I3I reef I I . J " 17 I ; Keg” {IE ~ I ‘9 . ,x’" I r - . . 13 ///.. I 21 I I Coral 4 , I . 7,, ' ”(A/7,,» I 27 I 25 I w \L/ \ fl _ 2 Cmflgfdw 26 I I 3 I 13 is 5.. 3 15 I I I “C > 20 3 27 I 2 17 I19 (fi 12 13 I“ 16 - I, 19 coral Coral at g 21 17I I Coral 15 . j- 5 '— ,5 I (“floral reef 17 4k 28 {4/1 I I 15 @Coral 44 5 12 6 I I j . Coral 15 11 17 (3;) _ 5 15 I i. eaten ,_. or? 17 “"8' 817 81/ , WW WW I7 : " i” I I LAMOSEU BAY W 21 23 I mmral ' @Coral 19 16 I 19 I i 3 30 I _ 21 I 15 Coralyreeffl 12 @ l I . , I 25 3 3 K 17 15 51 18 39 40 (2g 41 Q9 42 50 22 . W . coral fligmral 23 19 £9 3 3 29 14 816 E, 111 ~ 816 I0 3 o 24 .. I7 11 22’30” W —I7 23 —~—« 2230’ I0 13> 21 29 18 3 3 1}, 21 15 V 27 g \/ 15 20 815000m.N_ /3 I5 3 17 K 16 21 2; Coral root 4 , 19 I?" C I f ”633 19 - _/ ‘ g _ _ . ' . i . ‘~='\212 °"‘ ""ss 22 4 17 . I j " v . . ‘ - ' . '. ~ ., I 0 * Coral r 9'1’\, . I 3 . , . ,- ,. ~ 2 I 29 13 20 Miami (”I 7‘22’00” -- 7°22’00” 151”32’OO” 339000m,E 32/30” 340 341 348 37/30' 151°39’30” W8563 Scale 1:25.000 . . . 1 . . . . Edmon Z-AMS (AWE) 1 2 o ISIalure Mlle Interpretations for road and airfield construction by Harold G. May, U.s. ARMY MAP SERVICE, FAR EAST - 57-041 - R-15 — 2/59 - 3.40 I——I t 1 I 1 t L 1 1 I .. E ‘" W 1 ,. —W V - 1954-1955. Prepared under the direction of the Engineer, Hq AFFEI'8A, by the US. Army Map Service, Far East. 1000 500 U _.mm...“,,__I999_m_w_c fig 2000 Meters Compiled in 1957 by photogramrnetric (multiplex) methods. Coastal hydrography compiled from USHO I 101001 I—‘I I ‘00 IV—J F—I O 1000 — ~~~~~ °OOOY (1 Chart 6049, 1944. Horizontal and vertical control established by Corps of Engineers, 19511 Names trans» l H H “H }_{ r——l _____ _. ‘2‘ ar 5 Iiterated in accordance with rules of the US. Board on Geographic Names. Major roads are classified by 1 I, reconnaissance by the 64th Engineer Battalion (Base Topographic), 1952; other roads are classified from I , I 1 2 Y ' I III INauticaI MIIe source maps and aerial photography and are not Verified by reconnaissance. Coastal vegetation are clas- ' I ' ' ' ’ r I I I T" ‘ COVERAGE DIAGRAM INDEX TO ADJOINING SHEETS sifted by reconnaissance by Military Geology Branch. Intelligence Division, Office of the Engineer, Hq AFFE/8A, , with personnel of the us, Geological Survey, 1955. Map not field checked. CONTOUR INTERVAL I0 METERS VERTICAL DATUM MEAN SEA LEVEL Road and airfield construction compilation based on field observations 1954-1955 by Military 4544 II NW , I ' ‘ ' ‘ . ' ' I . - - I - ' i ' EEpififgyheBrsnghGéiglzllglieailugzuggsmn Office of the Engineer Hq U 8 Army Japan With person TRANSV ERSI: M ERCATOR PROJ ELTION MAP 41 HORIZONTAL DATUM IS BASED ON THE As'i‘RCNoMIC STATION NO 2(1981) 151°53/34 3” EAST or GREENWICH, 7‘ISII37.7” NORTH \\ \ 4544 IIISW 4544 III SE 4544 II SW A‘s . LEGEND HYDROGRAPHIC DATUM' APPROXIMATE LEVEL or LOWEST Low WATER MAP 37 MAP 39 MAP 42 ROADS BLACK NUMBERED LINES INDICATE THE 1000 METER UNIVERSAL TRANSVERSE AI? weather MERCATOR GRID ZONE 56. INTERNATIONAL, SPHEROID THE LAsT THREE DIGITS OF THE CRIB NuMPEos ARE OMITTED 4543 IV NW 4543 IV NE 4543 | NW \w\w§ hard surlace, two or more lanes Wide , , NONE Built 111) area , , LEN s. . \\\‘\.‘\\§ \ MAP a \\\ \ W \\ \ loose or light surlace, two or more lanes wide None Church, School. Cemetery .. ...,...,_... I \\‘\$§\\\\'\e\§\‘\\.\\\\\\\\\§\\\\ \\ 38 MAP 40 MAP 43 \\ 4“ ‘c IIaId snilace, one lane wide , , ,7 None Limit 01 danger line. Submerged reel L7LA. I f /[ COMPILATION METHODS loose or Irghi surlace, one lane wide . , None Wreck Sunken. Exposed , L, . o I ., .I_ g / 4045’ r1 Photo-stereo Photo-planimetric Map _ o i I _ . "fl'girf’wf’i’i’ "’ “""” "I, ' ""’."””"" ’ ""A' ' 2 , .- . fan or dry weather, loose surlace, two or more lanes wrde mergers . Sunken rocks; Foreshore flats I on I GRID ZONE DE"II’NAIION II ‘ A h ”MW "”9“” II" 1 W ' " ' 0R - / 34 MIL: f 56N I X “I GLOSSARY Fail or dr weather, loose surlace, one lane wide , e r e r : :: R Ii b h' R t ‘ 3 MILE. I “Him-“ ' ”A V" 1 » - - I “C 5 “9 0’ awas I ee . , , f / I 100000 M ”3““ ”If“ I A. USHO Chart 6049, 1944 (reliability good). Berg .2.Lv.c.,.s%,,.*_.,,,__W_.”A mountain, peak Cart track; trail ___.__~"E Depth Curves and Soundings in Faihoms z _ I 1 m, Wm “my” 100000 mm I I I Aerial photography: lvFeb., July 1946; 2-Jan. 1949. Nom en bay . c I I I I I ”iandald au e l3IIl03d, Sill Ie track , , -—+—+——t—-— @\_ I .I “4‘13““ ‘" “III” ”‘5 WI”! I155 I LP I I (NM 8" *L_____._LLL_‘LL7 anchorage o E E E Regen,” Dam, Man A i, 7 W I a, 2 IbeatetIrsH/ERTICAL grid Ilneio 1m 01 I I Unun en cape point Standard gauze railroadI double track .L. . . —++-—II-—H— I.-- :‘ We. and Im inner LEW; imIIIIE III.) I I ,.__.._E,.___-___A_ _____________ I 2’5” Salt evaporators .. . W m . , m, ”7777 7,7, ,.. \‘nfl hm» either II the top or bottom 'VMIXIII, or I I I Narrow gauge railroad. srngle track , , —T_‘—P— __ ApnnoxiwATE nun oui INATION 1355 on IneIIneliseII I I43 I . 2’6” A “- — roa CENTER or SHEET I Esirmaie tenths 110m grid line to own. I I BI Narrow gauge lallltlad, double or multiple tract . —-rr—'“—n— Rice paddy; Mam, 7 W W, W n n : ANNUAL mourn WANG; Ir “gnu” I I 3, locatelIrsi MORIIONTALngnIIneBELow I P A ,I I mini and read LARGE iigules IauelIng tire? I enter transmissmn line , ,, . .. . ... L .I I:- Use diagram only to obtain numerical vclwx. L, Inc E‘I'IEI In the left or rIini margin, or i I I Spot elevation In meters. Checked, Unchecked , x mg mg NIP“? Mangrove WWWW .2, "or To determine magnetic north line. conned the i 4 q 1 ’ d I I“ “W"? ‘I‘WII1 or t t I I ‘15) I— . ,, ,, I Era IIIIIWPI‘I I 888 are PI n mg I: sIImatPIemhs ram ng Ine spam I , ,._ Wall, Levee CIItI mum. “fig/fig I 1 pm" pom, P on m. mom Edge 0! ”'6 map I the NI' rnc' Iaies Ilse ONLV ihe 1 I I J I Woods; Scrub , ,, W , L. ., . __ Ed WIiiI the min, or the angle between GRID i Muir 'Im~-s«>l:neI :a- . ._ 1.74; “MIMI “ ” '3 DE 8" °‘°"""°" ‘ UDOT sw CAROLINE ISLANDS Principal hawgation light oi lighthouse; Anchorage * \L Ironical grass, Coconut grove , ,,,,, E ,, , the degree scale at the north edge of the map. I — II I 1958 TRUK ISLANDS CAROLINE ISLANDS 1325,000 TOL N‘W Military Geology of Truk Islands MAP 38 Roads and Airfields 3 a / 15193200,, 339 32,30, 340 341 345 51 . 151 39 3924200” 7°22'OO” . .. I 17 Coral reel 1 . oral Coral 10 22 13 15 are '3:- o -. W C(Iml ' 314 814 14 “14% I 131 / ‘c 27 v% D 11 I" 21 1 , 12 Coral new, (M C/ 9 z o A Coral reefiiii- (1‘ 21 Coral {6 . Coral Q C ’ ‘ ‘Cbral reel 13 17 0m: i Coral teeff'i-‘rh 1 — 23 2 A 1A) 24 U ‘2 \ 3 2013' "i 15 /r x a (”3) We“ , ‘i . 813 13 K J 4 13 Coral/ ‘, 3/ 11 1, 13 12 3 11 __________ , l\‘ ‘1 \I ‘1 18 21 ,-_ 1,131 39 1’11; \\ l“ I i 19 room ,1 //»i.\ \\_// // 5, X e 1 2 I. \ 1, 2: 193171 5 8 28 ‘ 812 12 12 i 16 18 31 I cm‘ 21 33 // \\\\ ‘i I 2‘ (i K 15/" 35 18 \\ 24 ‘x\ 1_\ 811 811 1 1 /§, 1” i 45.2.. ‘ ° 3 ~\\ 0R0 EN MISS N , l ‘ _ 20100." — “‘6‘ \\ ———— 8 L 15 4 E” \3_~4,,/' 20’00” 18‘\ ‘ ”ZNK coral \\ \ 28 16 4 E \‘x\ mm an en Unikopi 12 A0 ~-_/ ‘\ 1/8 ‘\ \\ 14 23 i ~\ 24 x a; / 22 29 ~.\\ _ [LICK HARBOR u” 23 \\ . , ‘\\ 11 K31 - . ' \ \ coral 2 ,1 ’74:, \V \‘s‘ v/ (51} \‘KLA VII 8 1 m 8 ' / rotf'fikgfifi 1 i \ 810 10 O coral x, \/o/ I \ 3/—/o\ @ /\Y .\ i 3 3 24 "r1“ 4 r / 15 2.1. \\ 3, EN WISENIF a 25 \ 1 3 25 ‘\ 12 \\ 3 29 sand and shells‘\\ coral 3 \\\\ \ (2) 2‘ .\ 3 22 \\\ 23 3 coral \ \\\ 28 f x 17 l/ \\ i’ 11 i coral / 809 ‘~ I 2 I 809 ,_ 0.9-- ‘2 SUITABILITY FOR ROAD AND AIRFIELD CONSTRUCTION 18 ® 25d 2 E l / K sari 23 x 1 2 1 . MAP TRUK ISLANDS . 3 ‘ 29 19 J - / W C) ’ \ ~ 17 4. , \ \\ coral 16 ( 11 co.a \\ s \ coral \ “ \ 25 mm 23 \\\ °\ 42 _ Road suitability is on the basis of gradient, relief, curves and tangents, subgrade conditions, and vegetation. Airfield suitability is in terms of an airbase with ‘Qx\ \\ — a 10,000-foot runway and heliport suitability on basis of a SOC-foot diameter field. Suitability terms, in order of decreasing suitability, are: excellent, good, ”‘- \\ “sex 28 “s.\ 27 _______________________________ fair, poor, and unsuitable. 22 \\ \‘rc 21\‘\ ______ _,. _________________________ CW" ‘1 ‘\ $52 29 ‘ \V: ______________________ 31 \ “ \\ 25 23 191 \19 W \ 25‘s. 29 s t bl f 803 cora \ ‘~\ \ ui a iity or *— 8 1 ., s , \ \ ~ 1 . . -»—- 08 . It: 08 \b w 18 .\ / 33 \98 T R U K I S I. A N D 5 Unit Terrain description "CDiai: Coral sand 1‘ 18 L2. \\ \ ,: 4 3 1‘ 34 ~\\ 21 Roads Airfields Heliports a; 7 I. “"3' \‘30 “T:— x, 19 \\ 31 Coral ‘, />\ \ \ 31» W“ \\\ “"d UNSUITABLE Dry level coastal areas of sandy flats and rock and earth fill, barrier-reef islands, and the four 23 27 i / ’ 112 ‘x\ egg?“ sand ‘~.\ & _-- EXCELLENT GOOD Japanese-built airfields; elevations 1 to 10 feet above sea level. Extensive stands of coconut and 23 sand I , x” 2 19 \\ 44 45 \\\ __________ 46 """""""""""" (only because breadfruit on the sand and grass, brush, and some coconut on the fill. Some fill, clearing, and sand 39 40 I41 / ’ \‘~\ 43 ‘x """""" 0f size) drainage required. 21 I x 21 ' \ 19 ,i / \ sand 1 ‘\\ \ 17 ' I 21 15 2,5532%“ 13 I 11 ‘ ~.\ cgrsal 35 TRUST TERRITORY OF THE PACIFIC ISLANDS Scattered upland flats on slopes, plateaus, and crests of highlands; subgrade mostly clay and - .711 ' E Coral (U.S.A. ADMINISTRATING AUTHORITY) GOOD UNSUITABLE GOOD some rock. Scattered stands of coconut, natural forest, and brush and sizable grassy areas. / 807 l a 19 O7 \\ Some clearing, blasting, and bridging reqUired for roads. _ 807 soeu REEF Coral \ Coral reel \\ “xx \\ Broad extensive areas of moderate to steep terrain on hillsides; subgrade mostly clay and some \\ 29 \X “1;, FAIR UNSUITABLE UNSUITABLE boulder talus. Scattered stands of coconut, natural forest, and brush and extensive areas of dense \ \\ reed grass. Cut and fill, clearing. and drainage required. 27 A; x \ Broken or long sinuous rocky escarpments and some very steep earth slopes; subgrade bedrock _ i i, 17’30” \ \ , 17 30 \ 31 \ POOR UNSUITABLE UNSUITABLE and some areas of clay and boulder talus. Extensive stands of natural forest and scrub. Road 19 \\ \ construction requires blasting, cut and fill, clearing, drainage, and possibly tunneling. \ \ r, 1 — 806 9 \ \ 806°00m-N. 27 06 06 23 \ 3—51 \\\ \\ _ ___________ IE} _____________________ \ 35, \\ Mangrove swamps and marshes on coastal lowlands. Swamp bottom is loamy sand and some PA CIFI C 0 C EA N 355 T: —————— ma] 21 “*X \ POOR UNSUITABLE UNSUITABLE muck; in marshes, organic muck in places 16 feet deep over clay subsoil. Raised rockfill road- \ \\ 17 ‘ beds required in swamps and rock-fill displacement of muck in marshes. _._ \ coral 438 418 12 \ _3_6, - 15 19 \ / 7317/00" b° m" \\ I I I I ’6 32 l 7°17ioo” 151°32/00” 339000m£ 32’30” 340 341 342 344 345 346 348 37/30” 349 350 351 151°39’30” W855 3 Scale 1:25,ooo . . 1 . . . . Ed'm" Z'AMS (AFFE) 1 5 0 lstaiute Mile Interpretations for road and airfield construction by Harold G. May, US. ARMY MAP SERVICE. FAR EAST ~ 57-041 - R-15 - 2/59 ~ 3.40 ‘ ’ ‘ * *L ' fi‘ 1954-1955. Prepared under the direction of the Engineer, Hq AFFE/SA, by the US. Army Map Service, Far 10'00 500 0 1030 3‘00 Meters East. Compiled in 1957 by photogrammetric (multiplex) methods. Coastal hydrography compiled I . . . . 1000 500 O 1000 2000 Yards from USHO Chart 6049, 1944, Horizontal and vertical control established by Corps of Engineers, 1 H H ,_, ,_, ,_, 1 1951. Names transliterated in accordance with rules of the US. Board on Geographic Names. 1 g 0 lNautical Mile Major roads are classified by reconnaissance by the 64th Engineer Battalion(BaseTopographic), ‘ I; 1952; other roads are classified from source maps and aerial photography and are not verified COVERAGE DIAGRAM lNDEX TO ADJOINING SHEETS by reconnaissance. Coastal vegetation are classified by reconnaissance by Military Geology Branch, Intelligence Division, Office of the Engineer, Hq AFFE/8A, with personnel of the U18. CONTOUR INTERVAL ‘0 METERS Geological Survey, 1955. Map not field checked. Road and airfield construction compilation based on field observations 1954-1955 by Military Geology Branch, Intelligence Division, Office of the Engineer, Hq, U.$. Army Japan with person- nel of the U. S. Geological Survey. ROADS All weather hard suriace, two or more lanes wide loose or light surface, two or more lanes wide . . hard surlace, one lane wide loose or Iighl suilace, one lane wide Fair or dry weather, loose surlace, two or more lanes wide , . ; . Fair or dry weather, loose surlace, one lane wide . Carl track, (rail Slandaid gauge railroad, Single track Standard gauge railroad, double hack Narrow gauge railroad, Single track Narrow gauge railroad. double or multiple tract Power transmissron line , Spot elevation in meters: Checked, Unchecked ,,,.. ___W%75§ Wall; Levee; Clill Waierwhee! oi mill; Located obiecl LEGEND None Built-up area on None Church: School: Cemetery None leII of danger line, Submerged reel “ / None Wreck' Sunken, Exposed a 4 45 o 11’ OR Sunken rocks, Foreshore flats OR 84 MILS :: , Rocks bare or awash, Reel .. .. 3 “ll-5 _._..A4AA Depth Curves and Soundings in fathoms —+—+———+— . Reservoir; Dam; Dilch 49—11—11— z’o” Salt evaporator: , fiflfl— APPROXIMATE MEAN DECLINATION 1955 1'6" FOR CENTER or SHEET fl Rice Paddy; Marsh WWW, ,7, a_ ANNUAL MAGNETIC CHANGE 1' EASTERLV 7 Use diagram only to obtain numerical values. .1,“ x,“ Nipa; Mangrove __m,... 7 q OTower Printipal navigation light oi lighthouse; Anchorage 7 * i; To determine magnetic north line, conned the pivot point "P" on the south edge oftbe map with the veins of the angle between GRID NORTH and MAGNETIC NORTH, 01 piolfed on the degree scoie at the north edge of the map Woods; Scrub ugh,” , , ,, ”17.7,“. I:II: Tropical grass; Coconut grove ,,,,i,,.,.,.. 1.7, DI: VERTICAL DATUM: MEAN SEA LEVEL TRANSVERSE MERCATOR PROJECTION HORIZONTAL DATUM lS BASED ON THE ASTRONOMIC STATION N0. 2 (I95l): 151'53’34.3” EAST OF GREENWICH. 7‘21/37.7” NORTH HYDROGRAPHIC DATUMI APPROXIMATE LEVEL OF LOWEST LOW WATER BLACK NUMBERED LINES INDICATE THE 1.000 METER UNIVERSAL TRANSVERSE MERCATOR GRID, ZONE 56, INTERNATIONAL SPHEROID THE LAST THREE DIGITS OF THE GRID NUMBERS ARE OMITTED GRID ZONE DESIGNATIONI TO GIVE A STANDARD REFERENCE ON THIS SHEET To NEAREST 100 METERS SAMPLE POINT: TRAIL JUNCTION 100,000 M. SQUARE IDENTIFICATION 1, Read letters identifying 100,000 meter square in which the point has: LP Locate first VERTICAL grid line lo LEFT of paint and read LARGE Irgures labeling the LP line either in the top or bottom margin, or on the line iisell: 48 Estimate tenths from grid line to point: 9 ,Lucaie first HORIZONTAL grid line BELOW point and read LARGE figures labeling the line either in the left or right margin, or on the line itself: 11 Estimate tenths from and line to paint: 1 E" u IGNORE the SMALLER figures of any grid number; these are Ior finding the full coordinates. Use ONLY the LARGER figures of the grid number; SAMPLE REFERENCE: LP489111 "ample: 806000 If reporting beyond 18° in any direction, k; '— prefix Grid Zone Designation, as: 56NLP489111 1958 7/ I “\\\ COMPILATION METHODS Photo-planimetric Photo-stereo W A. USHO Chart 6049, 1944 (reliability good). Aerial photography; 1-Feb., July 1946; Z-Feb. 1947. 4544 || NW MAP 41 4544 IIISW 4544 III SE 4544 II SW MAP 37 MAP 39 MAP 42 4543 IV NW 4543 N NE 4543 I NW MAP 38 MAP 40 MAP 4.3 GLOSSARY Berg .A*,._._ mmountain, peak Nom en bay 0ror en anchorage Unun en cape, point TOL NW, CAROLINE ISLANDS TRUK ISLANDS CAROLINE ISLANDS 135,000 U D O T 812 2° 3° 4° 5° 6° 7° Lt IILLILLLI 11/ T‘% Military Geology of Truk Islands MAP 39 Roads and Airfields 151".‘59'3m 352 40'004353 354 355 356 357 42/30' 358 359 360 301 362 45iool 353 364 365 15117100! 7‘27’00” i ’ , 30 I 29 I I , I l , 7 27/00l I coral I 29 , , , , I l 23 I I i 34 , I coral I L I I 24 coral I I 30; ,r’}\\ I 26 cora|,I ‘ ,’/ \ t, I coral I i I i 34 , I I I 21 SUITABILITY FOR ROAD AND AIRFIELD CONSTRUCTION , I coral 8 823 ” ' ' ”‘"”‘“ ""’I‘““'““‘ ' " 23 ‘ 7'" I‘ "‘“"""" 53' " I 51 23 “WW” MAP TRUK ISLANDS ’ ’ W‘ 23 r I 1 coral I 9 I I : I j I 29, I I I cora I I I Road suitability is on the basis of gradient, relief, curves and tangents, subgrade conditions, and vegetation. Airfield suitability is in terms of an airbase with I 30 I 31 I a 10,000-foot runway and heliport suitability on basis of a 500-foot diameter field. Suitability terms, in order of decreasing suitability, are: excellent, good, I 7 I Z I; l l I I; L A G 0 0 N fair, poor, and unsuitable. ‘ J i i 31 g 24 I i ,5_5, coral , 30 , (A I I?” I I Suitability for , i 29 /(3" 1 Unit Terrain desciption I , I 27/ cat,» I Roads Airfields Heliports , ‘ 28 a , / W ,,,,,,,,,,, , 8 822 rrrrr 7777- -+ 777 7 . 22 - 7777777mi 7 7777 7 7 7 277+ , 2 , 7 7 77 7 7 7 7 7 7 7 22 I I coral; , I, 241/ I Dry level coastal areas of sandy flats and rock and earth fill, barrier-reef Islands, and the four I I ‘V” I UNSUITABLE Japanese-built airfields; elevations 1 to 10 feet above sea level. Extensive stands of coconut and I ’1 + I 21 EXCELLENT (only because GOOD breadfruit on the sand and grass, brush, and some coconut on the fill. Some fill, clearing, and 77 351.3, ______________________________________________ _________________________________________ of size) drainage required. . , / 58 59 3 60 . coral Scattered upland flats on slopes, plateaus, and crests Of highlands; subgrade mostly clay and I 24 18 I GOOD UNSUITABLE GOOD some rock. Scattered stands of coconut, natural forest, and brush and sizable grassy areasl / oral reel‘, 2 ~72 I 18 Some clearing, blasting, and bridging required for roads. =z7iisc+2raireer i 1,, coir ITRUST TERRITORY OF THE PACIFIC ISLANDS i I ‘~7\\ I i, I “7 (U.S.A. ADMINISTRATING AUTHORITY) , ,6 28 I I 1 l7 coral I 520mm” I, / 21...", ,, _ ,,,,,,,, AW, ,, 21 ,_,, ,, ,,,,,, I ,, .. , , A, ,,, , A ,, 7 7+7 +— 821 821 , WW, , ._ . ,ssss l 77777 77 7 2f 7 ,- 7 7 77 7 as - - .L a ”W, ’ ; Broad extensive areas of moderate to steep terrain on hillsides; subgrade mostly clay and some , i I g; I 12 ‘ '5 2; 22 3 FAIR UNSUITABLE UNSUITABLE boulder talus. Scattered stands of coconut, natural forest, and brush and extensive areas of dense I 26 I I reed grass. Cut and fill, clearing, and drainage required. , coral I 24 28 l i I 20 18 13 , . i I 15 Vhile Sand Islet U s Zfeet ‘ Broken or long sinuous rocky escarpments and some very steep earth slopes; subgrade bedrock I ,s, "COVE! POOR UNSUITABLE UNSUITABLE and some areas of clay and boulder talus. Extensive stands of natural forest and scrub. Road 2) construction requires blasting, cut and fill, clearing, drainage, and possibly tunneling. - 2 10 I 17 3- |+_, I coral 12 3 . 820 25’00’l ,._L 1,, 17 14 .. Mangrove swamps and marshes on coastal lowlands. Swamp bottom is loamy sand and some / 800 I 20 coral I 5 POOR UNSUITABLE UNSUITABLE muck; in marshes, organic muck in places 16 feet deep over clay subsoil. Raised rockfill road. 25 00' L I 21 21 ‘ beds required in swamps and rock-fill displacement of muck in marshes. l 13 I. ‘ ‘ » .l i - I s L A N s i 21 ; I ’ I I i 20 , 22 I 15‘: I I ______ ___ I19 -, ,_,_ 77--c,g_\ . I "“"--7 ______ c 3513}“‘ I i 7..2\ re; . ____ 8 819 l 19 , Coral reel" 17 l 19 I 16 coral 22 18 I 21 / ‘I c rel reef 17i é:%5 2/7 , 13 'i 16 4, 13l , .913 2k” ‘ ‘ Cm I 16 22 ”coral Im II ' " 18 I ,’/ i \ 11 i I ’0) 17 I I I ‘3 ” 813 , i g \ 8l8 ._ We... , LL. ., I8 7. 77 7 7 I 777 7 fig 7 ‘8 .Ico‘iai 1, 20 ’- 15 , , Carol 1] i\ / I, ; 18 i , 1 \53 I / I I I / I I 15 . I , ‘2 sand I 21 T3 22/ I I I ( 4 , i , I 115 12 ‘ I 6; I [r/ i g],_\\ I send and shells sand and shells 17 i 16 r 5 \ I : 18 30/ 1,8 I I sand I :oral ‘, I, I, [ll \\\L2_§' /// : i i i r \7/ i, 3 I I I I; I I I 12 18 I l l, .- 3 a}; 7, I v "‘17 ” , 12 I 18 17 I 22 i a i i i l I I I I I I I I‘ l , I l \ i 1 I i \ \, i i = , \ I 53 54 55 17 I 56 13 16 i, t, 64 65 21 , 18 l‘ 19 , 1 ‘ coral \‘ ‘,\ 16 13 1, La indicates swept depth area in feet I I, \ \,, I 1 ll \\ \\\ 1, I ‘, \\ l , i /'_‘\ \ r i, i 17 I / r \i i, \ , is i HID/3°.) I i 816 816 “' ~ \ l ' I 6 '”‘““““"" ’ coral I 21 i, /I 1, \ z I j ,1 Lg, , x, 18 . g l I Wei /6 DOT ROAD I 13 x \ , . s_ \ \ ‘i I I ,\ (anchorage) 18 7 s_ \\\ t, ,\ 18 X 22 I 54 Kg 8 R coral 10 \O \-7____16\ \\ \\ 13 55 \‘1 I I d 533 ’ sand ‘s7s‘ \\ I, ‘~4 It, , 13 I ‘ 5 7 12 \ 4 “7\\ \, \, /, 17 29 \\ + (/"\\sand , 12] . , ~ 3, 13 C r l \\i\ \\ //;o— \ / 3 i, care 2 \t’t // ?2‘50’ # + L I GDI cI)?al ,3_3, I 17 — /, 2+, \, 15 147% 22/30" / g I: \ \‘74/ I B 1 // l 17 17 42 //1/6 \\ >>>>> ,,_77’ ’ TT’T—K T—ATV Effl/ / 1 Q: \\ I 11 42 ~; 62 12 “Q,"J», y:_-,_-7 “““ 13 : J: I , 10 \ i i \X 21 I 17 8 3L 10 10 / Ix \\ r , x : coral \ \16 815 815000mN . _ . . M- esssgfiflw Lie .2 1 .ss. _, . , . \ 5 . \ t 12 , X, 17 I ,3 tat, K” .c , t, I ; \s‘ 11 \s. // 7——- 1 \ r 13 ,.\\ / J 3 \ I I 17 Q7) 11 <9 \s ,1 15 (313 ,o 7 . Coral reel 0 4 I X I I I 4 3 Cora 33.“ /is: /,6\ + 5)“ CM 13 is : 15 = i It, 1 2 I 4 \ i I 13 //10\ I I, 702200" ‘ 2 °”’ 2 -~ TJCM I \‘X I 13 I shells 5/ 8 3\ is l ' 12 1 NW“ 7+22+oo~ 151“”.9’30” SSZOOOmE. 40/00" 353 354 355 356 357 42/30” 362 45’00” 363 364 365 151“47’OO” 361 W855 5 Scale 1:25.000 Edition 2AMS (AFFE) 1 2 0 IStatute Mile Interpretations for road and airfield construction by Harold G. May, US. ARMY MAP SERVICE. FAR EAST - 57-041 - R-15 .2/59 - 3. 4c -1 . Prepared under the direction of the Engineer, Hq AFFE/SA, by the US. Army Map Service. Far 1°00 50° 0 1000 2000 MEWS 1954 955 East. Compiled in 1957 by photogrammetric (multiplex) methods. Coastal hydrography compiled I 1000 I ' 1 50‘0 ' I I ‘0 1000 2000Y d from USHO Chart 6049, 1944. Horizontal and vertical control established by Corps of Engineers, , ,_, ,_, ,_, ,_, H fl a' s 1951. Names transliteratedhn accordance with rules of the us. Board on Geographic Names. . . Maior roads are classified by reconnaissance by the 64th Engineer Battalion (Base Topographic), 1 0 lNaUI'Ca' M'Ie 1952; other roads are classified from source maps and aerial photography and are not verified COVERAGE DIAGRAM INDEX TO ADJOINING SHEETS by reconnaissance. Coastal vegetation are classified by reconnaissance by Military Geology Branch, Intelligence Division, Office of the Engineer, Hq AFFEISA, with personnel of the US. CONTOUR INTERVAL '0 METERS WITH SUPPLEMENTARY CONTOURS AT 5 METER INTERVALS Geological Survey, 1955. Map not field checked. Road and airfield construction compilation based on field observations 1954-1955 by Military Geology Branch, Intelligence Division, Office of the Engineer, Hq, US. Army Japan with person- nel of the U.S. Geological Survey. LEGEND ROADS All weather hard surlace, two or more lanes wide c__,.i None Built-up area , loose or light surface, two or more lanes wrde None Church; School; Cemetery v hard surlace, one lane Wide issuiiifl None Limit of danger line; Submerged reel loose or light surface, one lane wrde None Wreck: Sunken; Exposed 7 Fair or dry weather, loose surface, two or more lanes wide : Sunken rocks; Foreshore llats __ Fair or dry weather, loose surlace, one lane wide 7, Cart tracli; trail Rocks bare or awash; Reel ..._.__-_ Depth Curves and Soundings in Falhoms __ Standard gauge railroad, Single track __.___M.#, Reservorr; Dani; Ditch Standard gauge railroad, double tracIl __ ‘ . 2"” Salt evaporators W‘L Narrow gauge railroad, Single track i." Narrow gauge railroad, double or multiple tracll WW —rr—“—1r— Rice Paddy; Marsh Power transmission line ,~¥.___c,.__.m___.__ _c_.____./ Spot elevation in meters: Checked; Unchecked if . I46 ‘ms Nipa; Mangrove Wall; Levee; Clill ___, if. A % Woods; Scrub Waterwheel ol mill. Located obiect fi,i V 010*" Principal navigation light ol lighthouse; Anchorage _ * 3/ Tropical grass; Coconut grove ‘1‘:- C]- —.________ L (1‘ -DD WEE] 4‘45’ .. on 54 arts APPROXiMATE IEAN DECLINATION I955 FOR CENTER OF SHEET ANNUAL MAGNETIC CHANGE I’ EASTERLV Use diagram only to obtain numerical values. To delerrruna magnetic north lino, conned the pival point "P" on the south edge of the map villi the value of the angle between GRID NORTH and MAGNET'C NORTH, as plolhd on thodagreoscoloallllenofiltodge o’ the "rap. VERTICAL DATUM: MEAN SEA LEVEL TRANSVERSE MERCATOR PROJECTION HORIZONTAL DATUM IS BASED ON THE ASTRONOMIC STATION NO. 2 (i95l ): ISI°53’34.3’ EAST OF GREENWICH. 7°2l’37,7” NORTH HYDROGRAPHIC DATUM: APPROXIMATE LEVEL OF LOWEST LOW WATER BLACK NUMBERED LINES INDICATE THE 1000 METER UNIVERSAL TRANSVERSE MERCATOR GRID, ZONE 56, INTERNATIONAL SPHEROID THE LAST THREE orcrrs or THE GRID NUMBERS ARE ouirreo GRID zons DESIGNATION: N TO GIVE A STANDARD REFERENCE ON THIS SHEET TO NEAREST 100 METERS MILO“) M. SQUARE IDENTIFICATION LP lGNORE the SMALLER liguros ol any grid number; these are lor lindlng the lull coordinates. Use ONLY the LARGER figures ol the and number; example: 815 000 SAMPLE POINT: : SCHOOL I. Read letters identilyinz 100,000 meter square in which the pomt lies: Locate llrst VERTICAL 3nd line to LEFT at point and read LARGE llaures labeling the line either in the top or bottom margin, or on the line itsell: Estimate tenths lrom grid line to point: locate first HORIZONTAL and line BELOW point and read LARGE llgures labeling the lino either in the ten or right margin, or on the line itsell: Estimate tenths lrom [rid line to point: I“ P LP 58 16 4 SAMPLE REFERENCE: LP589164 Il reporting beyond 18“ in any direction prellx Grid Zone Domination, as: I 55NLP589164 1958 4544 ll NW MAP 41 \\\I§§\§i\§§§\\ 4543 N w 4543 iv NE 4543 l w x \ mm MAP 38 MAP 40 Milli:j 43 COMPILATION METHODS Photo-stereo Photo-planimetric Map W ‘ GLOSSARY A. usno Chart 5049, 1944 (reliability good). Barnes" czggmxfi; Aerial photography: Feb., July 1946 UDOT SE, CAROLINE ISLANDS Military Geology of Truk Islands MAP 40 Roads and Airfields TRUK ISLANDS 711‘ K) N 11 CAROLINE ISLANDS 125,000 , , ll 1 \ I ; 0., 2. 3., 4.. 5. 6. 7., 151 away 352 40'000 353 354 355 356 357 42/30/I 358 359 360 361 362 49007 364 365 151'47/007 7'22/00!r . . 7'22’00' Dra 11 31 J 3 7 7 21 k f I0 7 1? “'3' - cr1r1al 12 17 5 coral 2 1 11 11 o 12 11 \. 10 \ 3 \lo 16 O \V 16 \' 1o 11 14 8 814 14 \ 31 C 31 14 G: $011 8 2 h 2 17 11 15 e5 6 \ 17| 12 F Cora , 7 / 16 1 o, 10 \o l 22 5 1 3/ 16 i 10 17 ’10 1 ’0 , Ci: 15 51 cgraal ' 1 2 1 / i) “1‘0 1 '12 car1 23 ‘0 2‘ 0 14 17 813 813 1 M w“ 3 7» w ----- v 0 10 coral ( 10/ 5 1 coral :5 19 3 61 ./ \\ coral )7 2 \\ 22 <2) 20 14 C(23rlal \17 58 meal 5 9 6 O 3 6 coral 6 5 \\ IO 7 15 ‘1 22 19 T \\ coral V0 G \O \ '5 3 \\ 2 12 24 czral 21 (7/ 16 \ 3/ coral l coral l0 9 IX \ cora \ B 1 12 12 812 1, 70 \ ‘ 5 20 \ I S I. A N D S O coral r.) OROR N PENIOR \\ 19 2 \\ Lu indicates swept depth area in feet 17 \\ \ i, 16 \\ 19 23 \ / \\ coral cor43l l4 1‘ 1 \1 24 24 \\ // \\ coral 3‘. 811 ‘ 1.9.. x 11 811 \ r 3 \ 28 1 \ 21 2 I i + 5 —— 18 2 I r/ 20 00 I \\ 17 2 0 egg 20 00 l \ 5 ‘l 33 \\ 31 15 ' 1__r \ 4 1 \\ 5 21 19 1 r r R U \ K L A G 0 O N ~= 1 \ , 23 2° 3 I \\ 27 coral 20 2 4 l 1 \ 1 coral coral cora 2 2 21 1 \ 26 2 29 18 coral 1 23 ‘1, . 3 810 1 s 810 ’o 1 O 1 1 1 O 1 O ‘0‘ // ' \ I\\ \r\ 30 18 1 4 / l \ \ coral ’ x 22 ,r .1 1 ,3 1 \ 22 TRUST TERRITORY OF THE PACIFIC ISLANDS 18 8 I \ / 1 ,\ 1 \ 18 1, (U.S.A. ADMINISTRATING AUTHORITY) 22 \\_g/ I \ 1‘ 25 _________ a £1 1 \ ‘1‘ ' cora' cm" 20 ___,-—-"”’ 15:31 18 [I \\ 17 \\ coral —’—— _______ 19 1/ ‘\ \\ £5) 27 __/ ————————— T‘ 25 1” 18 \\ \\ 19 1 1””, ______ ,\ -_ I \ \ r _________ 17 r’@\ IT‘r ’1 \\ 23 21 \ I r““'—” 22 g?“ l 3 1‘ 1 14 1| 1’ \ \\ 1 23 I 809 809 ...... . ‘ x "a 094 ; i *— 09 - "a Wya- * * A _.--_._-_. 24 i x 19 SUITABILITY FOR ROAD AND AIRFIELD CONSTRUCTION 1’, \ \ \\ 18 axx”, 23 \\ \\ 1... indicates swept depth area in feet MAP TRUK ISLANDS 23 22 /IP ‘‘‘‘‘‘‘‘‘‘‘‘ \\ i \\ 9 24, \ 19 : \ 21 i ’/ \\ I \‘ 43 r 1/ \ I \ . . . , . 1 (I \\ 1 \\ 1 Road suitability is on the basis of gradient, relief, curves and tangents, subgrade conditions, and vegetation. Airfield suitability is in terms of an airbase with —_ ________ I / \ I \\ 1 a 10,000-foot runway and heliport suitability on basis of a SOD-foot diameter field. Suitability terms, in order of decreasing suitability, are: excellent, good, ' ‘‘‘‘‘‘‘‘‘‘‘‘ _\\ 1 11 \\ 21 ,z 21 1' \\ 1 fair, poor, and unsuitable. ‘ ~\\ 1 29 \ 1’ ‘ ,gg, I Tszg I “—4 \ i , \ . 23 ~4 \\ 13—31 1‘ 1 \\ ,______,_,_13 _____ A ______ \ ‘x 1 \\ f --——- ------------------------------------------- “\ \ ‘ Suitability or 8 ”-4- 21 \ \ WE. \ .E .7 W, W W, Lu, , #7. u. _ ._..L 808 _-- ——-— T‘ "T 08 \ \ 19 08 \ Terrain description 08 a 23 \{3 \\ Roads Airfields Heliports corAal \\\\‘\\\ 1 £1 \\\\ \ \ 21 \\\ 1 \ UNSUITABLE Dry level coastal areas of sandy flats and rock and earth fill. barrier~reef islands, and the four 21 \\ 1 \ 1 Japanese-built airfields; elevations 1 to 10 feet above sea level. Extensive stands of coconut and . 54 \ l \\ 60 EXCELLENT 1°“1Y because GOOD breadfruit on the sand and grass, brush, and some coconut on the fill. Some fill, clearing, and 52 53 19 55 23\ 5 57 58 59 of size) drainage required. 17 246 21 22 1 '\ 27 san \\ 17 1 I \\ 20 . 1 11 \\ I j \\ ' Scattered upland flats on slopes. plateaus, and crests of highlands; subgrade mostl cla and 4 . r t Y Y r5 \\ 1 \\ 22 GOOD UNSUITABLE GOOD some rock. Scattered stands of coconut, natural forest, and brush and sizable grassy areas. \\ g3, 19 I ‘\\ Some clearing, blasting, and bridging required for roads. 8 807 . . 1 o7 . — —— 07 19‘ x r ‘x\ island) 1 17 \ “~ 21 GB 16 5 \‘~ 2“ Broad extensive areas of moderate to steep terrain on hillsides; subgrade mostly clay and some IO 21 1 18 FAIR UNSUITABLE UNSUITABLE boulder talus. Scattered stands of coconut, natural forest, and brush and extensive areas of dense wal ; reed grass. Cut and fill, clearing, and drainage required. Q 23 lo r3991 24 £1” Broken or long sinuous rocky escarpments and some very steep earth slopes; subgrade bedrock 17,30” __ I3 POOR UNSUITABLE UNSUITABLE and some areas of clay and boulder talus. Extensive stands of natural forest and scrub. Road __ 17,30, 1 ( construction requires blasting, cut and fill, clearing, drainage, and possibiy tunneling. 1 1 25 29 /- 8 806000m.N- O6 \ 21 06 7 > 06 21 3 0 23 sand 29 27 \\ *‘ Mangrove swamps and marshes on coastal lowlands. Swamp bottom is loamy sand and some \\ L3. 23 POOR UNSUITABLE UNSUITABLE muck; in marshes, organic muck in places 16 feet deep over clay subsoil. Raised rockfill road- 29 ‘\ beds required in swamps and rock-fill displacement of muck in marshes. 13 \ .\ I \\\ 25 23 fl) 22 \\ 23 , ~ 25 \\ , . m" cm 16 ‘/ 23 a \\2\ 23 1/ 1 1 24 27 I ‘~‘\ 1 I rum! 1 536121 15 A. ‘9 17 28 \ 24 \‘WL 22 d’, I 1 30 mm 7’17/00r 151'39’30” 352000m.E_ 40'00” 353 354 355 356 357 42'30’ 358 359 360 P 362 45/00” 363 364 365 151'47'00” 361 W856S Scale 125,000 Edition 2-AMS (AFFE) 1 l o ISt t t M'I - - - - , , , , , f , , , , 1 a u e '5 Interpretations for road and airfield construction by Harold G. May, US. ARMY MAP SERVICE. FAR EAST . 57-041 - R-15 < 2/59 - 3.4C Prepared under the direction of the Engineer, Hq AFFE/BA, by the US. Army Map Service, Far 10100 1__1 500 0 1000 2000 Mae's 1954-1955. East. Compiled In 1957 by photogrammetric (multiplex) methods and from 155,180. USHO 1000 500 0 1000 2000 Yards Chart 6049, 1944. Coastal hydrography compiled from USHO Chart 6049, 1944. Horizontal and L ,_.I H 1—1 1—1 ,._1 , ___, vertical control established by Corps of Engineers, 1951. Names transliterated in accordance 1 1 0 IN 1. IM'I 4 with rules of the US. Board on Geographic Names. Coastal vegetation are classified by reconnais- I , . . 1 1 r . . . 1 . 311 I03 Ie sance by Military Geology Branch, Intelligence Division, Office of the Engineer,Hq AFFE/BA,with personnel of the U.S. Geolo ical Surve , 1955. M ‘ . ' . 3 y_ 3" .“°‘ “9'“ Chem? . .. CONTOUR INTERVAL IO METERS WITH SUPPLEMENTARY CONTOURS AT 5 METER INTERVALS COVERAGE D'AGRAM ”‘05" To ADJO'N’NG SHEETS Road and airfield construction compilation based on field observations 1954-1955 by Military VERTICA DATUM‘ MEAN SEA L’VEL Geology Branch, Intelligence Division, Office of the Engineer, Hq, U. 8. Army Japan with person- L t w 4544 11 NW nel of the U.S. Geological Survey. \\ TRANSVERSE MERCATOR PROJECTION \\\ MAP 41 HORIZONTAL DATUM IS BASED ON THE ASTRONOMIC STATION NO. 2 (1951). \ 151'53/34a” EAST or GREENWICH. 7‘21'37,7' NORTH LEGEND HYDROGRAPHIC DATUM : APPROXIMATE LEVEL OF LOWEST LOW WATER xii“?! 4M54A4Pm3$9E fixing; A ROADS BLACK NUMBERED LINES INDICATE THE 1.000 METER UNIVERSAL TRANSVERSE All weather MERCATOR GRID, ZONE 56, INTERNATIONAL SPHEROID . None THE LAST maze DIGITS or THE GRID nuuseas ARE OMITTED 4543 IV NW 4543 IV NE 4543 1 NW hard suriace, two or more lanes wide ______.. None Buillun area WWL,.L. \ r . GN loose or lighl surlace, two or more lanes wide _ None Church; School; Cemetery 3 I 1Cem \\ _.‘\ MAP 38 MAP 4C MAPI___413 hard suriace. one lane rude None Limrt oi danger line; Submerged reel loose or light surlace, one lane wide None Wreck: Sunken; Exposed I "‘5’ COM T ODS o'io _ PILA ION METH fair or dry weather, loose surface, two or more lanes wide Eire: W .7, Sunken rocks; Foreshore IlaIs 0R “0:1LS GRID ZONE DESIGNHION' 1:1:2:é:;2~:€::igfiiziaSE?! Photo'stereo Map Fan or dry weather, loose surlace, one lane wide ; ,_, ; Rocirs bare or awash; Reel 3 WLS 100,000 M. SQUARE IDENTIFICATION SAMPLE POINT: x 112 W GLOSSARY Ca" "3““ ""' *“n” ”em“ CW” 3"“ ‘" ”mm mm rm: 1°1”""‘”1.l°°'°°° meter LP \ A. 1:55.180, USHO Chart 5049, 1944 (reliability good). 31:": 53:11:31: 1 , square in w 16 t 9 din ies: I Standard gauge reilioad. “we track .H—é— Reservon; Dam; Ditch 2, Locate lirsi VERTICADL grid lrne to LEFT 01 A911“ photography: JUIY 1946- Standard gauge railroad, double traclr ._____— —#-—¢t-—+t- S It LP point and read LARGE irgures Iabeirrrgihe 2’1” 3 , 1 th in i b it , Narrow gauge railroad, Single hack .______.__. —r—‘—v— APPROXIMATE MEAN DECLINATION 1955 1111191151111"; up or 0 am margin m 53 z’l” FOR CENTER OF SHEET Estimate tenths from grdl t ' t: 5 Narrow gauge railroad, GOUNE Ol MUIIIDIE track “TV—“W'— Rice Paddy; Marsh ANNUAL NAGNETIC CHANGE 1’ EAerRLv 3. Locate Iirsi HORIZONTAL at: IrnEDBIZLow . . / t d d tuner I b i PM" t'ansm'ss'on hne ‘ ‘ 'WW“ U” diagram 0N7 9° obtain WWW, VGMSr fizleneiltaor'frai the left #1131 firm}: Spot elevation in meters: Checked; Unchecked " 74.6 “/55 NW5 ”"3”“ Yo delermine magnetic north lino, connect the ”3:0“ '2' “mu“ "l:'“'9'df"Y WI the line Itselli 13 1 _ 1. H ri num er; esa are or in in . ; Wall; Levee; CI!" 921‘ P'Vo' porn! P °" the Nb odqe °' the MP titre run EOOYflInIles. Us: ONLY M: Estimate tenths Irom grid line to no nt 4 1 _ 1 Warm; Scrub with I!» value of the angle barman GRID LARGER Mares 0' the rind number: SAMPLE REFERENCE: LP535134 Waterwheel 0' "Hui Locum Obie“ ———'_ V 0 we, NORTH and MAGNETIC NORTH, as plotted an example: 806000 ll reporting beyond 18" in any direction, 3/ Tropical grass; Coconut grove the degree scale at "a norfll edge of the map. ._. pm” GM 1°” D'S'SMHM' “1 56NLP535134 TO L N E, CARO LI N E 'SLAN DS 1958 Principal navigation light ol lighthouse, Anchorage __.L ’1‘ TRUK ISLANDS I 7’ Milia Geoo o ru sands CAROLINE ISLANDS 125,000 MOEN NW 3° 2° 3° 4° 5° 3° my“ Listndkrirhehs 151'47roo' 366 new 357 368 369 37O 371 soroor 372 373 374 375 52/30! 376 377 373 379 151“54’30' o . ° 1 I 7 32,00, IO/ Fanama 53’ ”w W 27 ‘7~L—~/ \ 16 I 35 7 32 00 9 LVislafi) 2%? \I ' \ coral /,, _ \\ coral £:’/°;:7~>cj-\:EEE \ Coral\ \\ 22 29 /,L_\\ \ \O . ’19, \\ £9“ / 21 13 \\ 8 I , (I 12 \I Uncovers 1 foot *\ - \ sand grad shells III I\ \ coral [I I 1 \,\ SUITABILITY FOR ROAD AND AIRFIELD CONSTRUCTION 34 2, \\\ \\ Coral reef \I e DS e I . MAP, TRUK ISLAN 24 h I, 5 \I L 25\\ ,’/ \ f 36 Cora|\ 5 //I 39 28 \L,K< 4 / Coral \\,V‘<,/ sand coral 8 Road suitability is on the basis of gradient, relief, curves and tangents, subgrade conditions, and vegetation. Airfield suitability is in terms of an airbase with 30 7“" 32 32 832 32 a 10,000-foot runway and heliport suitability on basis of a SOD-foot diameter field. Suitability terms, in order of decreasing suitability, are: excellent, good, fair, poor, and unsuitable. 55 35 33 Q Suitability for . . ' sand 30 Unit Terrain descriptlor. 33a Roads Airfields Heliports ‘3" clear UNSUITABLE Dry level coastal areas of sandy flats and rock and earth fill, barrier-reef islands, and the four ‘ 35 GOOD Japanese-built airfields; elevations 1 to 10 feet above sea level. Extensive stands of coconut and EXCELLENT (only because breadfruit on the sand and grass, brush, and some coconut on the fill. Some fill, clearing, and 33 35 of size) drainage required. 27 1 831 831 ___.. 31 3i 35 Scattered upland flats on slopes, plateaus, and crests of highlands; subgrade mostly clay and ,_. indicates swept depth area in feet GOOD UNSUITABLE GOOD some rock. Scattered stands of coconut, natural forest, and brush and sizable grassy areas. 36 Some clearing, blasting, and bridging required for roads. 33 “mi coral 72 73 74 75 76 77 78 79 80 Broad extensive areas of moderate to steep terrain on hillsides; subgrade mostly clay and some FAIR UNSUITABLE UNSUITABLE boulder talus. Scattered stands of coconut, natural forest, and brush and extensive areas of dense 3“ reed grass. Cut and fill, clearing, and drainage required. mm 35 . 29 coral ' 35 coral 3 830 LL... 3O 30 30 Broken or long sinuous rocky escarpments and some very steep earth slopes; subgrade bedrock POOR UNSUITABLE UNSUITABLE and some areas of clay and boulder talus. Extensive stands of natural forest and scrub. Road 34%| 36 construction requires blasting, cut and fill, clearing, drainage, and possibly tunneling. CM CM] sand Ego shells 31I cora . 30 34 I Mangrove swamps and marshes on coastal lowlands. Swamp bottom is loamy sand and some sand , POOR UNSUITABLE UNSUITABLE muck; in marshes, organic muck in places 16 feet deep over clay subsoil. Raised rockfill road- 52,1", / beds required in swamps and rock-fill displacement of muck in marshes. T R l a K L A G 0 O N 34 (r 30/00” 7 . /r— 30'ti0” I \ 27 ‘ 829 829 29 29 , 29 ,\ I lg 30 , 4,6, TRUST TERRITORY OF THE PACIFIC ISLANDS 34 , silo as. 22 f 7 ‘i, U.S.A. ADMINISTRATING AUTHOR TY) 35 18 L “/28 ‘ 30 1 28 22 shells M x’/ ,x’xo saagd // 2 / /3 30 (2’ 1 > coral 828 828 24 28 28 ,2 7/ I80 I“ 29 29 /// Loral \\ , /l<‘\ fig IK coral Ir coral /// 28 ’ 29 3' 28 / 31 27 18 . 24 TRUK ISLANDS/ ,0 ,, sheIis ’/ 6 \ / / 2 3 a) 25 , 8 827 27 27 29 12 29 29 L_, indicates swept dept area in feet 29 29 8 826 26 26 30 u Iii 66 67 68 69 7O / l I i 28 I 30 / 29 ‘I 11 / 29 23 \\ co‘ral // \\\ /, 8 825 v 25 25 19 27’30’ — + 27,30, 23 13/ III 21 ,1 l I III / l 8 8240mm“. 24 u / 24 7 0 . :-.a;.---.~, ”4 7' m y r7; VIM " °°”' “ - 4’“ gents/“$35. ‘fi’a. 7°27I00' J ‘ ‘ “ a" ‘ 7:27roor/ 151‘47’00’I 366 OOOmEI 47’30’ 367 368 369 370 371 5000” 373 374 P 52,30,376 377 378 b ‘1’ 379 151°54’30/r 375 ,.. 5 “I856 A s FFE Scale 1:25.000 Edition 2- M (A 1 . . . . ) 1 5 o IStatute Mile Interpretations for road and alrfleld 'constructlon by Harold G. May, u.s_ ARMY MAP SERVICE, FAR EAST . 57.041 _ RLIE, L 2/59 . 3,4C ~ 5 ' 19541 . Prepared under the direction of the Engineer, Hq AFFE,'8A, by the U.S. Army Map SerVIce, Far East. 1000 500 O 1000 2000 Meters 955 Compiled in 1957 by photogrammetric (multiplex) methods. Coastal hydrography compiled from USHO l P——-{ l--—-l I-—~I I——l I—l Chart 6048, 1944. Horizontal and vertical control established by Corps of Engineers, 1951. Names trans- IOIOO H H 523* H H? 1000 2000 Yards Iiterated in accordance with rules of the US. Board on Geographic Names. Major roads are classified by Q’ r 7‘ reconnaissance by the 64th Engineer Battalion (Base Topographic), 1952; other roads are classified from 1 o lNautical Mile ' ‘ ‘ ‘ ‘ ‘ L ‘ ‘ J COVERAGE DIAGRAM lNDEX To ADJOINING SHEETS source maps and aerial photography and are not verified by reconnaissance. Coastal vegetation are clas- sified by reconnaissance by Military Geology Branch, Intelligence Division, Office of the Engineer, Hq AFFE/SA, with personnel of the U.S. Geological Survey, 1955. Map not field checked. CONTOUR INTERVAL IO METERS . . . . . . . l : 203? and alrfleld construction compllatlon based on field observatlons 1954-1955 by Military VERT CAL DATUM MEAN SEA LEVEL 4544 ” NW eo ogy Branch, Intelligence Division, Office of the Engineer, Hq, U. 8. Army Japan with person- ‘ he. of the us. 660.08,”, Sum, TRANSVERSE MERCATOR PROJECTION “AP 4‘ HORIZONTAL DATUM is BASED ON THE ASTRONOMIC STATION N0. 2 (I951) 151‘53'34 3' EAST OF GREENWICH. 7°2I’37, ' N RTH 7 O 4544l|l SW 4544 III SE 4544 ll SW LEGEND HYDROGRAPLHIC DATUM : APPROXIMATE LEVEL OF LOWEST LOW WATER MAP 37 MAP 39 MAP 4‘2 ROADS BLACK NUMBERED LINES INDICATE THE 1,000 METER UNIVERSAL TRANSVERSE All weather MERCATOR GRID, ZONE 56, INTERNATIONAL SPHEROID T , 4543 IV NW 4543 IV NE 4543 l NW hard surface, two or more lanes wlde ,,,,,,,, None Built-up area LLLLLLL LL LLLLLHL .L None HE LAST THREE DIGITS OF THE GRID "UHBERS ARE OIITTED w‘Q,\\\ , . . L C , » Icem: \s‘~,\\\\s\ v3 .. MAP 38 MAP 40 M 43 oose or Ilght surface, the or more lanes wlde L L L None Church, School, emelery if. L mid I . \‘\:\\{\\,_¢.\\\‘\\\ +- , \. \>.o.\\. \\.\\. hard surface, one lane wide iLLLLLLLLLLLLLL LL None Limlt ol danger line; Submerged reel LL LL . t COMPILATION METHODS loose or light surface, one |ane wrde LL L LLLLLLLLLLL None Wreck: Sunken; Exposed L LL L L «a 3:“ Photo-stereo Photo-planimatric Map . ? NATION: . . r » , . Farr or dry weather, loose surface, two or more lanes Wide fi:: Sunken rocks, Foreshore llats L L. L L LL LLLLL t Sand GR") 10“ DESK; 70 “NE A STANDARD REFERENCE 0" \ ' ':y I * ,9" 56M rills SHEET TO NEAREST loo METERS m ' . - - » ~- ,_ - 0 GLOSSARY ancho Fair or dry weather, loose sur ace, one lane wide L Rocks bale or awash; Reel LL L L L LL * Iooooo M. s UARE lDENl’IFlCATI N , - , ~ '0' en rage p 3, if , ° 0 “MP“ F°"”- T SUNKEN ROCK A. usno Chart 6048, 1944 (reliability good). UM“ en me. ”0,," Cart track, trail LLLLLLLLL LLLLLLLLLLLLLLLL ____-- Depth Curves and Soundlngs In fathom: LL .LLL ’q \ 2 “ma Mm ”MM" 100,000 mm Aerial photography: Feb., July 1946. Standard au e raIIroad, Sill to track L, 7,7 —-+—+—r—— . . » \— “W' '" "hit" me p°'"‘ "'5: LP 3 K g Reservoir, Dam, Ditch LL LL LL LL LLLLi C] 2. Locate tlrsl VERTICAL grid line to LEFT at Standard gauge railroad, double track , ,ii —tt—li—«— Palm and read LARGE firms hbelmz the , 2"” Salt evaporators ,.L,LL LL LLL7LLLLLLv LP llhe either in the too or bottom margin, or Narrow gauge railroad, srngle track 7L LL ~77— APPEOXIMATE MEAN DECLINATION I955 onthehnellsell: 75 _ _ 3’6” . FOR CENTER OF SHEET Estimate tenths from Elld line to 11mm: 4 "3"“ ENE! ”I‘m“. double 0' "WHIP” "39“ 7777 —"—"“—"'_ Rice Paddy; Marsh ,iLL L ,LLL LLLLLL LLL ANNUAL MAGNETIC CHANGE l’ EASTERLV 3. Locate lirst HORIZONTAL grid IIne BELOW . . . // L , . . ‘ paint and read LARGE llzures labeling the POW“ transmissmn “"9 7- 7—77777 ”~77. . > 1:]- Uu diagram only in obtain numerical minor. line either In the Ian or right mm", or Spot elevation in meters: Checked; Unchecked ,, , , " as X,“ Nina, ”any” 777 77 ' ' - To determine ”09M”: mm. It“, conned m. IGNORE the SMALLER “lures at any on the line Itsell: 28 , . H H End "Dinner; "'85! are '07 "MINE Estimate tenths from [ltd line to point: Wall; Levee; Clill 7 WV MAWW m [:ID PM” PM” P 0" "-0 300'” edge 0’ ”is MP the lull coordinates. Use ONLY the Woods; Scrub LLLLL. L . LLLLLLL . 7 wirh rho value of rh. angle bow GRID LARGER Mules or the and number. SAMPLE REFERENCE: Lp754283 Wt h I I 'II;l td b' ILLLLL._LLL L I? TOW V I: .. am ee 0 m. me 0 rec * o 3/ 7 7 [:‘CI NORTH and MAGNETIC NORTH, a: pron-don "m” 82 000 L'.Li.i°§.’."fzii’.°Bi.‘.§.;l.2”,’.§l'°“‘°"' 55NLP764283 MOEN NW, CAROLINE ISLANDS Principal navigation light at lighthouse; Anchorage _LL, lropical glass; Coconut grove LLLLLLLLLLLLLL LL the doom scale or the north odge of the map. 1958 CAROLINETRILngZLI/NNDDSS 1'25,000 N“ (C) E N S X§\V 00 20 3o 40 5o 66 70 Military Geology of Truk Islands " I- Isolatiiii . I Idiot MAP 42 Roads and Airfields 151°47/OO” 366 47/30" 367 368 369 370 371 50/00! 372 373 378 379 151 ”A, 7°27'OO” ,/ I I l , , i 4 22 28 /, 1 “703' a 10 4 ,. / 16 49 ‘ I g / _ i' I l2 777777777777 .21 ,3 ‘9 l 3 / 14 5 0‘ 17 (7/ ....... \ & L33, ; more EN NEWACHO L \ ’ ,« ‘i ; 1 i . . . ' , . 82 _23 / I I i I 15 32 Milk / . .. _ _ , sly.) 3 25 ,I / 17 t l I 0‘ {j}; ) . .;._.l . . I , ,1 x i i I i, . /. 8 ~ 6 . swan, m // 7/13 '1 I, I “ sang Nulwisei // // I g, il l’ ,' I 1’ K \ , 5, l 0 2 34 / as ‘, 171 I, x 2 i \ g ; ,/ “ \ :fi 9 24‘ ”SHEIJ d ' i. 23 29 i \ \‘1/ l ‘ / i sand \ "f" 411)?” X . ’/ i W \ 5 t/ . ‘. rah“ ’“ 30 21 \\ 8 /I \\ “39'2“ //\\ 23 'r. .' . I 19 ’x 25 28 Ky kw i 4 h ,,/—r’ -, -» ; 3 UCLA ROAD i , f “faxe— ,/:.:;-\-11 as /, ,xsde ,1 11 (OROR EN NEPUNG) r: Ear-n ’ \\\ \I/ < 33 ’I "’ 1 " ’ i 62 I \, I 51 , I_J 5‘1 1 2 _ I / t\ / , AZ, 2 i Y I / 31 /\\\\:::\9/ [’V—\\ / Vt ‘ . l‘,‘é‘_\5 a!" gob // / / \ \ .i‘ "r / 2’ W )‘I It?» d117,: til/(e .. . 822 _ 22: .. \\I\8 cor II ,J)“I{:-‘:';(’.gll n‘ r coral -. / 53311 \‘719/1/Dl‘flj /// 17 I l3 1 23 ///’ and // I, ‘6‘] \ [/X, 66 67 68 69 22 i, a}, 78 79 Q, \ agar II I /// 15 . , /’ 33 / coral 18 sand and shells 821 17 28 21 ~:~7E}EE§"“' IIII' Iran; W" 7 I, awe} " #fiyll/{fgé’ywzav . . It 164%?» w ‘I‘ easy" 31 30 sand ‘ I3 24 i 19 27 c 31 coral I /’x V, . > coral 19 i / I ~ , 820 I 20 _-l m ,.. w P 25/00” I 23 7 M , 12 ‘s / RCfl‘N/Aéfi‘gOSET 55 \\ / / _I ‘7 R UK L A G 0 ON” L ,,—»\\ / 2: \\\ 7/ \t / 15‘ V 18 K 8 COTE /’ ‘\ \ ral \ / i i/ I \‘ ‘ 'x 24 ,i f 17 \\___3v’ A84 1_,_‘ \ I 24' 7 i6 , . \, . .. .3 SUITABILITY FOR ROAD AND AIRFIELD CONSTRUCTION ”'d ' """m I \ /4\ // iv 77 7,, 8 I 9 \ / l/ / / 19 7" fl‘ xvi/(’3 ; 33 MAP, TRUK ISLANDS r” ’ , Road suitability is on the basis of gradient, relief, curves and tangents, subgrade conditions, and vegetation. Airfield suitability is in terms of an airbase with a 10,000-foot runway and heliport suitability on basis of a 500-foot diameter field. Suitability terms, in order of decreasing suitability, are: excellent, good, 29 fair, poor, and unsuitable. 32 Suitability for Terrain description } 8 Roads Airfields Heliports , 7 453% s: at 18 .. 15 x \ UNSUITABLE Dry level coastal areas of sandy flats and rock and earth fill, barrier-reef islands, and the four \ \\ 22 GOOD Japanese-built airfields; elevations 1 to 10 feet above sea level. Extensive stands of coconut and 16 I 18 \\ \ 31 EXCELLENT (only because breadfruit on the sand and grass, brush, and some coconut on the fill Some fill, clearing, and T R U K , I s L A I N D S \ \\ sand 0f size) drainage required. I \\ \\ \ TRUST TEIiRITORY or THE PACIFIC ISIANDS ‘7 ‘\ 23 coral \\ \ Scattered upland flats on slopes, plateaus, and crests of highlands; subgrade mostly clay and (US A- ADMINISTRAT'NG AUTHORITY” UNSUlTABLE GOOD some rock. Scattered stands of coconut. natural forest, and brush and sizable grassy areas. 17 I Some clearing, blasting, and bridging required for roads. t t I i I iii 317 A_E~ 17 if 18 Broad extensive areas of moderate to steep terrain on hillsides; subgrade mostly clay and some UNSUITABLE UNSUITABLE boulder talus. Scattered stands of coconut, natural forest, and brush and extensive areas of dense 21 /-\ reed grass. Cut and fill, clearing, and drainage required. // \\ ,1 8 i 3.“. 72 U‘“ 73 Broken or long sinuous rocky escarpments and some very steep earth slopes; subgrade bedrock UNSUITABLE UNSUITABLE and some areas of clay and boulder talus. Extensive stands of natural forest and scrub. Road construction requires blasting, cut and fill, clearing, drainage, and possibly tunneling. 17 , coral . I \‘\ 8 ' fie"! 9:77; 16 Mangrove swamps and marshes on coastal lowlands. Swamp bottom is loamy sand and some ’1 val/"(MR UNSUITABLE UNSUITABLE muck; in marshes, organic muck in places 16 feet deep over clay subsoil. Raised rockfill road- ,J’fi'j V033? beds required in swamps and rock-fill displacement of muck'in marshes. a % . 12 “’TV/TVTVTTT‘~~_E 2230” f \ 7/7\ IEJ coral '\ 12/, 16 13 s 12 ' ‘ .2_0i 33 s \ 1K“ 15 I K \ l\ 'h‘ 4 ‘ l7 \\ x I ,_ \ x s 1613 - ‘ 1 \ f 17 10 A , , ~ ‘ “*~»L—_l__ '/ "" l \ 10 fi\ A w Iol .s \ \ he \ 7 V 8 000m cor I42 { 32 A%% ®§§ \‘T’ A ‘l fl I 815 15 'N- ‘, 5 5 0/ 10 8 n, 3/5 s1 \ ‘ 15 /, l 3 ‘ . are . . . :2 - - . K I122 “Lo 4 12 9 ,- o._ '5’ l l \3u/ 31 , £53 51 %§_ - _ .Qf/A ~ Li! // "(coral lmm on Neawachang ‘ 3 Coral i0 4 * ' i" ' _ ' f V“ 16 ETEN ANC 1 4 as «)6 -:' ' film ' , Cora /‘\' 2 / 12 23 Qatar EN UN No { of! 12 , AC3 '5 \13 Cora gag f% 3 a“, “95.. NM; _ coral 5 J) 17 _°i\ 5 / 7°22'00” ..; "7‘53 ”XIII ”W s . . liltifihl EL 0 I \/} 7; (V, 151°47/OO” 366 000m.E' 47’30” d €67 368 369 370 371 5000” 373 374 P 5230” 376 377 378 379 151°54’5i0’ 375 W856 5 Scale 1:25.000 Ed'tw” “MS (AFFE) 1 5 0 1$tatute Mile Interpretations for road and airfield construction by Harold G. May, U.s. ARMY MAP SERVICE, FAR EAST - 57-041 - R-15 - 2/59 - 3.4c ' 1954-1955. Prepared under the direction of the Engineer, Hq AFFE,’8A, by the US. Army Map Service, Far East. 1080 500 0 1000 2000 Meters Compiled in 1957 by photogrammetric (multiplex) methods. Coastal hydrography compiled from USHO 1000 500 0 1000 2000 Yards Charts 6048, 6050, 1944. Horizontal and vertical control established by Corps of Engineers, 1951. Names I ,_, ,_, ,_1 ,_{ ,_, ‘ fl transliterated in accordance with rules of the U18. Board on Geographic Names. Major roads are classi- 1 5‘ 0 , . fied by reconnaissance by the 64th Engineer Battalion (Base Topographic), 1952 and reclassified from 1Nautica|MIle aerial photography dated 1955; other roads are classified from source maps and aerial photography and COVERAGE DIAGRAM INDEX TO ADJOINING SHEETS are not verified by reconnaissance. Coastal vegetation are classified by reconnaissance by Military Geology Branch, Intelligence Division, Office of the Engineer, Hq AFFE/8A, with personnel of the US. Geological CONTOUR INTERVAL 10 METERS \V‘ \V§§‘§‘<\\$§ Survey, 1955. Map not field checked, VERTICAL DATUM: MEAN SEA LEVEL $§§®$ . 4544 “ NW Road and airfield construction compilation based on field observations 1954-1955 by Military ' \§N\\§ , Geology Branch, Intelligence Division, Office of the Engineer, Hq, U.S. Army Japan with person- TRANSVERSE MERCATOR PROJECTION \ :\\\‘\1}\\ . MAP 4‘ Hal of the U.S. Geological Survey. HORIZONTAL DATUM Is BASED ON THE ASTRONOMIC STATION N0. 2 (1951): \ MK ' . 151'53/34.3' EAST OF GREENWICH, 7'21’37.7' NORTH . .\.‘. , ~‘ LEGEND HYDR GRAPHIC DATUM APPROX MATE LEVEL OF LOWEST LOW WATER ‘ I i 4544 "'SW 4544 “I SE 4544 H SW 0 2 I ROADS MAP 37 MAP 39 MAP 42 BLACK NUMBERED LINES INDICATE THE 1.000 METER UNIVERSAL TRANSVERSE ‘“ '4"th W MERCATOR GRID. ZONE 56, INTERNATIONAL SPHEROID hard suilace, two or more lanes wide a ”N“ Builtup area H_.____—_. ‘1‘ W ‘ ”E “ST “REE ”‘6'“ °F T"! GRID ”"an ”E ““775” 4543 IV NW 4543 [V NE 4543 I NW loose or light surface, two or more lanes wide _ '1 UN“ Church; School; Cemetery —___ 8 I {Cairn G" \ MAP 38 MAP 40 MAP 43 hard SUIIHCE, one lane Wlde _W— — Limit 0t danger line; Submerged reef _c_ _- lose 0 l' ht 5 face one lane w'd - - COMPILATION METHODS o r ig ui , II _ 3—: Wreck. Sunken, Exposed 0'09, 4.“, Photo-stereo Photo-planimetric Map Fair or dry weather, loose surlace, two or more lanes wide = Sunken rocks; Foreshore llats , 0R GRID ZONE DES'GNHIONI TO GIVE A STANDARD REFERENCE 0N § 0R THIS SHEET To NEAR: Tl c z s m GLOSSARY fair or dry weather, loose surface, one lane wide ======== Rocks bare or awash; Reel 3 wins 8‘ "”5 Tooooo M SQUAigrquENTIFICATION SAMPLE POINT‘ ; CH 5 00 M I R Nom 9" bay Can "m m“ D the d .. , “h ' ' - 5 001 A. usno Chart 6048, 1944 (reliability good). Oror an anchor". . _.___—— ____.._ ep urves an In a oms L Read Imus ”Mum“ 100.000 mm, LP 3. [1|st Charth605'9, 19431 i(reli984bsility good). Unun en cape, point Standard gauge railroad, single track —+—+—t—— ., _ . . a. square In which the point lies: Aeria p otograp y: ab., uy l . Reservoir Dam Ditcn . . . . , , 2. L i VERTICAL d LEF Standard gauge railroad, double track -Ii-—N——+t— {gr-g LP pzfriimanldsiud LARGE flirglur’elgalxelmzttfl , _ 2's” Salt evaporators — ,~ ~,,, - n, . b n . , Narrow gauge railroad, smgle "a“ _ T APPROXIMATE MEAN DECLINATION l955 Jemillizrellzwfi on or o om mm" or 781 . . _ Fon CENTER OF SHEET Estimate tenths from grid lineto point: Narrow gauge railroad, double or multiple track I Rice Paddy; Marsh “—— u L ANNUAL MAGNETIC CHANGE I’ EASTERLY 3. LocateiirstHORIZON‘iAL ”idling snow Pow” transmissmn “"9 ' —‘——— """"" I ‘ |:]- Use diagram only to obtain numerical values. fian::::,r?:dt;:ffff L??::Jfi::fivt: Spot elevation in meters: Checked; Unchecked . M6 a,“ "'9‘; ”"3”" ~—~—~————— ' ‘ To derermi‘ne magnem "or". line, conned m, lGNORE the SMALLER times or any on the line ltsell: 16 . . ,, ,, arid number; these are for finding Estimate tenths 1min grid Iirie to paint: 8 W N; L ; CI'II a § pivot point P on the south edge of the map _ a evee I [’1 Woods; Scrub ——-——-'—“ mm with the value of the an Ie between GRID magi: elfgdyzassthauzzdoxIEMb‘ehre' AMPLE . V Waterwheet of mill; Located object $ ohm" NORTH d MAGNETIC NgRTH l n d mmpie- 8 000 ' s REFERENCE LP781168 an , as p o e on ' If reporting beyond 18" in any direction, Principal navigation light at lighthouse; Anchorage * 3/ Tropical grass; Coconut grove . _ _._ DC) the degree scale at The north edge of The map. -1—5 “'“i‘G'm 2°" D““"“”°“- W I55NLP731158 MOEN SW, CAROLI N E ISLAN D8 1958 ‘N Military Geology of Truk Islands MAP 43 Roads and Airfields TRUK ISLANDS H I’M A §I FE x37 . o CAROLINE ISLANDS 125,000 T: 2° 3° 4° 5° 7 3 3 3 3 sized/376 377 378 379 151“54'30i 151'47/00/1 366 \ 4760” 357 368 369 70 71 50,00” 72 ' 73 ‘l/ o/ 7°22/00i 7'22’00” 4 of 33 .‘ggr‘ A arm! 46 lo 17 L4 23 / 23 lo, i._i am v_.l Coral ‘ FEM \ 15/£./’ “ . ‘i/ 47 r’ 1 ' ) 0 L 5 1' 7/ 7’ OROR EN N” 0 5 v I - ”grim ANCHQRAGE ,/ 1 ' 2 X, ——————————— 1\ I53 / 19 K3 1 l 22 0 \\ / 17 coral *U coversJ foot 2 ‘ \x // 814 , r - / 8T4 , find? ,4“ as. Coral 29 17 coral corll m are.” 813 813 r - ‘ ‘ ‘0 8 U5 ll: / . \ - ’ coral and 16 Unco ' s 2 fig: .. . . l 5“" ’ V 8 U; .- l coral . 12 o lo 9 7O \ carol 75 79 10 ' 16 1 sand 19 20 7 12 12 58"“ Un overs coral \/ O x 13 24 Uncovers. 2 feet * ' [\\, 8/3 J" sand 18 o'/ ‘/ 15 \\r P FY“ ”Relic 3* 812 812 coral 61 v /I I )13 14 OROR E Flam f, \ u [idea 1 foot 23 32 20 16 / ‘l-r/ 16 \ coral Z6 corel 0/ 61 l 0 1 / coral /\0 / / ’/ 17/30” 17'30/I —— ,r 3 / 3; r’ ,r / I I 1 39/ \J u 806 19 06 I 0/ 32 , 17 r 29 21 I 9050mm“. 25 4/“ 4i) mus l, 3 I can 5 ’// u E I ll \\\ 7°l6’00 —— «(fl—fl 7°l6 00 \, ‘\\ J//’i°,// , a Feneu Island ‘ x 34 35 ‘7 ' coral shell: 37 shells soaooom. N. .905” 803 22 3] 33 ’ I ll _. . ° I 7'17’00” U . [7 1”7 00 151‘47’00” 366000m.E 4760" 357 368 369 370 371 50’00” 377900!". E. l5|°53’30" 378 379 15l°54'30 52/30” 376 377 378 379 151 54 30 “’855 5 Scale 125,000 ' ' n 2-AMS AFFE l . . . . . . Ed'm ( ) 1 2 o IStatute Mile Interpretations for road and airfield construction by Harold G. May. US. ARMY MAP SERVICE. FAR EAST . 57-041 - R-15 ~2I59 3‘40 ' ’ ' * i T 1954-1955. Prepared under the direction of the Engineer, Hq AFFE,8A, by the U.S. Army Map Service, Far East. 1000 500 0 10E) 2300 Meters Compiled in 1957 by photogrammetric (multiplex) methods. Coastal hydrography compiled from USHO I I i I I 1 fi‘ Charts 6048 6050 1944 Horizontal and vertical control established by Corps of Engineers 1951 Names 1000 500 0 1000 2000 Yards i v - ' ' l l—i l—i H l-——-i l—-—-i1 - transliterated in accordance with rules of the U.S. Board on Geographic Names. Major roads are classi- 1 O IN t‘ lM'l - ' - - - - - au lca ie fied by reconnaissance by the 64th Engineer Battalion (Base Topographic), 1952 and reclassrfled from 7 . r 1 fl COVERAGE DIAGRAM INDEX TO ADJOINING SHEETS aerial photography dated 1955; other roads are classrfied from source maps and aerial photography and are not verified by reconnaissance. Coastal vegetation are classified by reconnaissance by Military Geology Branch, Intelligence Division, Office of the Engineer, Hq AFFE/8A, with personnel of the US. Geological CONTOUR INTERVAL IO METERS WITH SUPPLEMENTARY CONTOURS AT 5 METER INTERVALS Survey, 1955. Map not field checked. VERTICAL DATUM: MEAN SEA LEVEL 4544 ” NW Road and airfield construction compilation based on field observations 1954-1955 by Military MAP 41 Geology Branch, Intelligence Division, Office of the Engineer, Hq, U.S. Army Japan with person- TRANSVERSE MERCATOR PROJECTION nel of the US. Geological Survey. HORIZONTAL DATUM is BASED ON THE ASTRONOMIC STATION no. 2 (l95l) - U I l5| 53’34.3” EAST OF GREENWICH. 7 2| 37.7” NORTH 4544 IIISW 4544 III SE 4544 II SW LEGEND HYDROGRAPHIC oATuu: APPROXIMATE LEVEL or LOWEST Low WATER MAP 37 MAP 39 MAP 42 ROADS AII m BLACK NUMBERED LINES lNDlCATE THE 1.000 METER UNIVERSAL TRANSVERSE wea 8' a LAN.“ ‘ nib. MERCATOR GRID. ZONE 56. INTERNATIONAL SPHEROID 4543 IV NW 4543 IV NE 4543 I NW hard surface, two or more lanes wide .777 Bmltup area 7.77777..- ‘7W 6" THE LAsT THREE DlGlTS or THE GRID NUMBERS ARE OMlTTEn . . 3 LAle _ , ICelrl‘ MAP 38 MAP 40 MAP 43 loose or light surface, two or more lanes wide 77 Church, School, Cemetery 77........ . i ’1’ . m hard surface, one lane wide 77 7... —_ Limit of danger line; Submerged reel 7 + COMPILATION METHODS loose or light surface, one lane wide 7 ,7. 77 m Wreck: Sunken; Exposed 77 _____.-..... .7 a» .Aliud 0,”, 4°45/ Photostereo Photo-planimetric Map GLOSSARY Fair or dry weather, loose surface, two or more lanes wide 77.7.77: Sunken locks; foreshore flats 77.777 * + Sand on °R GRID ZONE DESIGNATION: To my: A STANDARD nzrmmc: on V "'- 7 Oror en L age * 84 MiLs Tlils SHEET To NEAREST 100 METERS ~ . . , - Unun en cape point Fair or dry weather, loose surIace, one lane wide -.-. :::::::: Rocks bare or awash; Reef .7-.....-77 _\ * 3 "”5 l00,000 M. SQUARE IDENTIFICATION SAMPLE POINT: t CHURCH A. USHO Chart 6048, 1944 (reliability good). ' . . ~r l . .. Cari track; trail 7..., .777-.- . Depth Curves and ‘ ln fathoms __ zd" 12 mm [mm “WNW loo.ooo mm, B. llSHO Chart 6050, 1944 (reliability good). > . _ Aerial photography. Feb., July 1946. Standard gauge railroad single track . . 5‘1“"9'" “"5" "‘9 90"" “95- LP ' T W ““ Resem": Dam? DIN?" 7—77» -— .7 2. Locute first VERTICAL grid line to LEFT of Standard gauge railroad, double track 77..“ . —-+l—ll——-ii— ”mm”. point and read LARGE lrgures labeling the 2’s” . Salt Evaporator: 777 “WWW LP line either in the top or bottom margin. or Narrow gauge railroad, single track .7...7.7 —v—"—r— _ _ APPROXIMATE MEAN DECLINATION l955 on the line itself: 71 . 3"” FOR CENTER or SHEET Estimate tenths from grid line to point: 3 "3"" gauge “'"oadi dome 0' multiple "‘5“ Rice Paddy; Marsh 7 _______ .— ‘k h ‘ ANNUAL MAGNETIC CHANGE l' EASTERLV 3, Locate firstHORIZONTAL and line BELOW Po“, transmission line . point Ind read LARGE figures labeling the 7 77 77.. ,,,,,,,,, D Use diagram only to obtain numerical Vail”. line either in the left or right margin, or 77 x... "iii: "new" fi~# if r. domino Mimic "on" "M “M "'- Lfrl°lfliif“litt‘ifl‘llf‘llr'ril ‘2".~‘"°."".°".‘:"; ii i -. ‘22 - - u n r S It'll l E" 5 mm II “16 0 0m 2 DE pivot point P on the south edge of "I. map the full coordinates. Use ONLY the g P with the value of lb. angle between GRID LARGER iigur-s of the arid number; SAMPLE REFERENCE: LP713122 example: 8 000 if reporting beyond 18‘ in any direction, % prefix Grid Zone Designation. IS: 56NLP713122 U MAN NW, CARO LIN E ISLAN DS Spot elevation in meters: Checked; Unchecked ., - 7m¥rj§ )3 ofower Wall; Levee; Cliff Waterwheel of mill; Located object 7 Principal navigation light of lighthouse; Anchorage * 3/ Woods; Scrub 77.....7. . Tropical grass; Coconut grove 777.77- -----. CID NORTH and MAGNETIC NORTH, a: ploilod on the degree scale at tfh north edge of the map. 1958 151 7°27’00” 823 322 I321 25’00’ 820 819 818 317 816 22'30’ 815000m.N_ 7°22'OO’ 151‘ TRUK ISLANDS U D (l T S ‘W Military Geology of Truk islands . o o o o , CAROLINE ISLANDS 125,000 0 2° 3° 4 5 6° 7 MAP 44 Underground InstallatIons °3zloor 339 32/30” 340 341 342 343 35/00! 344 345 346 347 348 37130” 349 350 351 151'39/30' I , ' I l \7\_ / I 1 I I‘VOK’I \\\,g\/ /. 27K» / 7 27 00 1 / \ ' \\ J \\ Ill ‘\ / ——L ‘~ - 48 30 ' ‘ K,” xi ,1” 27 29 m. cm, _2_6, I 0’ / ’ l 5 ‘, Sites Suitable for Tunnel—type Underground Installations ,I 29 Dr \ l , r 22 /»—--\-—“"/ I@ [I I\\ ,‘I coral 30 \x x/ I 23 /” Site Rock Excavation Rock Disposal Overlying Underlying Access coral “ PA C I F I C O C E A N 5 number type conditions characteristics of rock material material 29 T 0 L coral l Undivided Fair 3/; Rock out by fine- General construc- Soils up to Undivided Good to 8 2 3 lava. possibly grained dikes y; tion; road build- 30 feet thick lava lower part "‘" 23 some drain- 230 feet thick ing; swamp fill; of site / age problems dump in sea 155 2 Undivided Fair y; Rock out by fine— General construc— Soils up to Undivided Fair; no 27 (I lava possible grained dikes y; tion; road build- 30 feet thick lava road ‘. some drain- 200 feet thick ing I I, age problems I. FALEA; IOU/JI/ Flood 90mins [51/ ,o 3 Undivided Fair y; Rock out by fir—17- General construc- Soils up to Undivided Road at fl/ 0”“? ---------- “7.3;? lava possibly grained dikes ; tion; road build- 30 feet thick lava foot of some drain- 220 feet thick ing hill 29 322 ._,___‘__.i_~ age problems ""3 ‘ _____________ l 28 I 24 I LI Undivided Fair J; Rock out by fine- General construc— Soils mostly Undivided Road at lava possible grained dikes 2/; tion; road build- less than lava foot of “““““““““““““““ some drain- 150 feet thick ing 5 feet thick hill 41 age problems . y 27 5 Undivided Fair ; Rock out by fifi- General construc- Soils mostly Undivided Road at “1,2, 23 lava possibly grained dikes l 3 tion; road build- less than lava foot of g/ 1 0 some drain- 160 feet thick ing 5 feet thick hill 26,. ’4’” /\ 16 ‘2 5; age problems x,» ”carol 31 1 ————-- 821 \5;/ 1 3 w W 3 com 6 Undivided Fair J; Rock out by fine- General construc— Soils mostly Undivided Road at .19 I4 26 CD 32 /,-—/”' lava possibly grained dikes 1]; tion; road build- less than lava foot of 3 ”I“ “'3' 23 2% ///,- some drain- 300 feet thick ing 5 feet thick hill 12 22 CE?“ 19 ”'3‘ 28 32 age problems coral —\ 21 ”7/,” 2 Z3 (—0 coral ”7’” J ‘ a ,———"' 7 Basalt Good; possi— Polygonal colum- General construc— Very thin Undivided Fair ap— 21 4 --/""/— 33 bly drainage nar jointing; tion; road build- soil or bare lava preach to coral 12 III 6, 28 ”yet” coral problems 150 feet thick ing; add to rock rock mesa top 23 27 \I 2 “/2” A /’”‘\\ 25 “a; debris from west 3 0 ”xx” / 1 r 4 21 gal/v I Q; l/ Dike rock may have different blasting characteristics 22 Des \ I. r _ 24 __ x. L g/ See photo plate 15 A — 25’00” 19 18 ,L—r' 20 29 n- 820 20 .u \h 25 /— 3 7 24 " TRUK LAG ON 3 \O/ 25 7/ 23 24 23 23 11 x 31 \\ ,/ 30 f ,, sand and shells 4 l/ / ,x’ 31 29 . , ”x, ...... x, 21 g , /.x’ 2 19 ® 21 ,l/T’” 24 29 I x/,/ o 27 2 ,,—/’ ‘ ’ 21 2 29 5 TRUST TERRITORY on THE PACI lC ISLANDS Q) 24 22 2‘ (U.S.A. ADMINISTRATING AUTHORITY) ,2 r; ,«""/“—a 31 ”,d—”/’/ 27 , 7’" . ,-—/‘/ {2 19 319 ”,4 , x — £1 1g 19 21 23 3 VI. 22 19 ”(X/ 23 13 —’ SUITABILITY FOR UNDERGROUND INSTALLATIONS w L b, .. . z. ,, 27 21 1} MAP, TRUK ISLANDS so u .7 . .7 \_,I0\ ~ /3 [0—— Suitability terms, in order of decreasing suitability, are: excellentr 800d. fair, poor. and unsuitable. 23 o A . Coral Q) Coral C) Suitability for 17 Unit Description 21 15 Tunnel type Bunker type 21 16 -_ I >_ - 18 m II ' 8l8 — Rock conditions good to fair for tunneling. Adequate cover available with short ’ W 10 EXCELLENT UNSUITABLE horizontal entries. Drainage good. Stony overburden less than 30 feet thick. _, 15 \12 o ' 12 Slopes greater than 65%. .fi 4 . 3 17 ‘ $17 /2 . . 21 I \0’6-\ , Coral 4 fig 16 19 13 Rock conditions fair to poor for tunneling. Adequate cover avallable WIth short Y 25 K . 1 cm, 21 . . . 2 Coral 1 GOOD POOR horizontal entrIes. DraInage good. Stony clay overburden less than 30 feet is \ 4 <42 thick. Slopes greater than 65%. l 13 . . 13 17 15 ago 2 17 I 12 13 I, _ ., \° \ 6 19 19 4g ._ . , , , 17 "'3‘ IS : 3 18 K Rock conditions good to fair for tunnelIng. Long horIzontal entrIes or verbal 3/\cm. m, Com 5 18 17 FAIR POOR shafts required to reach adequate cover. Drainage fair to good. Gravelly and 15 @CM, 4} 5 stony clay overburden O to 10 feet thick. Slopes less than 65%. 15 5 coral 17 (31 15 W _. 11 17 cor2a 817 Rock conditions fair to poor for tunneling. Long horizontal entries or vertical “Coral W... 18 poop» poor; shafts required to reach adequate cover. Drainage fair to good. Gravelly and 0/\ 18 19 stony clay overburden 1 to 10 feet thick. Slopes less than 65%. I 19 15 Coral @ Rock conditions good to fair for tunneling. Vertical shafts or long horizontal 17 POOR GOOD entries required to reach adequate cover. Clay soil overburden 10 to 50 feet 43 49 17 50 15 5] 18 thick with relatively few rock outcrops. Drainage good. Slopes less than 65%. ; a l . . . . . . . 3 ‘ ‘8 18 21 Rock condItIons fan to poor for tunneIIng. Long horIzontal entrIes or vertIcal l 2 shafts required to reach adequate cover. Drainage fair to good. Clay soil 17 POOR EXCELLENT overburden 10 to 80 feet thick with few rock outcrops and easily excavated. I5 17 (:13 47 d _ Slopes less than 65%. . 1816 16 816 15 No feasible means of tunneling to adequate cover. Soils difficult to excavate, UNSUITABLE UNSUITABLE saturated. or periodically flooded. Low flat coastal lowlands, mangrove swamps, fresh-water marshes. and beaches. Locally suitable for small hasty fortifications. 11 19 oral reel 17 Selected site or area where a tunnel-type installation with a minimum floor space of 60,000 square feet ' 0‘5 could be excavated with only 100 to 300 feet of horizontal entry required to reach 100 feet of cover. 17 __ 22.30, (See accompanying table.) 11 X Location of existing Japanese World War II caves. I8 15 V / 815 3 15 I 11 17 & 16 2} 2 2 19 Enrol reef 3:: 19 . ( . 15 11 I/I'II 12 Coral reaf‘ 22 17 3 ‘ . A _ . £9, \ * r sip, 29 3 a (D ' < ' 2 1 1 13 I o 20 ‘ “5.: «MM . mam-I ('0 7.2200,, 32/00, 339 000m,E_ 3.2/30I 340 341 342 343 35'00' 344 345 346 p 343 37/30! 349 350 351 5139/30! 347 W856 5 Scale 1:25.000 ' ‘ l . . . . Ed'I'°” Z‘AMS (AFFEI I 2 9 18mm Mile Interpretatlons for underground Installation constructlon by Elmer D. us. ARMY MAP SERVICE. FAR EAST ~ 57-041 -R-15 - 2/59 — 3.40 Prepared under the direction of the Engineer, Hq AFFE7‘8A, by the U.S. Army Map Service, Far East. 100° 50° 0 1000 2000 Meters Patterson' 1954-1955' Compiled in 1957 by photogrammetric (multiplex) methods. Coastal hydrography compiled from USHO I I I I"“I I I—I H ‘I Chart 6049, 1944. Horizontal and vertical control established by Corps of Engineers, 1951. Names trans- 10100 H 1—1 52; H H: 1000 2300 Yards literated in accordance with rules of the US. Board on Geographic Names. Major roads are classified by g I 1 _ _ reconnaissance by the 64th Engineer Battalion (Base Topographic), 1952; other roads are classified from I . . Y I x O INaUt'Ca' ”"9 source maps and aerial photography and are not verified by reconnaissance. Coastal vegetation are clas- ‘ A ‘ ‘ COVERAGE DIAGRAM INDEX TO ADJOINING SHEETS sified by reconnaissance by Military Geology Branch, Intelligence Division, Office of the Engineer, Hq AFFE/BA, with personnel of the U.S. Geological Survey, 1955. Map not field checked. CONTOUR INTERVAL IO METERS VERTICAL DATUM' MEAN SEA LEVEL Underground installation compilation based on field observations 1954-1955 by Military Geology 4544 II NW Branch. Intelligence Division, Office of the Engineer, Hq, U.S. Army Japan with personnel of the MAP 48 U.S. Geological Survey. TRANSVERSE MERCATOR PROJECTION HORIZONTAL DATUM IS BASED ON THE ASTRONOMIC STATION N0. 2 (195l )1 I I° 3'34 3” EAST OF GREE ' / II ' 5 5 NWlCH, 7 2i 37,7 NORTl 4544 IllSW 4544 III SE 4544 II SW LEGEND HYDROGRAPHIC DATUM: APPROXIMATE LEVEL or LOWEST LOVI WATER ~ MAP 44 MAP 46 MAP 49 ROADS \\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\§\§\§§ \ BLACK NUMBERED LINES INDICATE THE Iooo METER UNIVERSAL TRANSVERSE W KRKKQ‘Q ‘WXK All weather MERCATOR GRID. ZONE 56. INTERNATIONAL SPHEROID §s\\\>\\\:\\\\§\ fixgm 4543 iv NW 4543 N NE 4543 l NW 5 .\. t \ hard surface, two or more lanes wide None Burn-up area WWW,,,, , , 7,, 7 None ”IE LASI THREE DIGITS or ”IE GRID NUMBERS ”IE OMITIED §&M‘ §v\\\‘§3‘§v2»“ .‘:‘<\ . . G. s x §\\\\\\\ \\\‘\‘\3\ \\ MAP 45 MAP 47 MAP so loose or light surlace, two or more lanes wide None Church, School. Cemetery iii ,lll__,__,,. in. l- : LC?” § Wm“ \\\ hard surlace, one lane mac 7,,” None LImII oi danger line. Submerged reel 7 COMPILATION METHODS loose or light surlace, one lane wide A, ,,,,,, None Wreck: Sunken, Exposed 7 HA 4°45’ Photo-planimetric ‘ I Fair or dry weather, loose surface, two or more lanes wide l:::;e Sunken rocks; Foreshore flats ,, M 0 H OR GRID 10“ “SIGN‘IIONI TO GIVE A STANDARD “(FERENCE 0" ‘ ' I " ' . 0R :4 virus 56N THlS SHEET To NEARESI 100 METERS FaIr or dry wealher, loose surlace, one lane wide 7 , . . 1 . . Rocks bare or awash. Reel , , , 3 "ll-5 100.000 MSQUARE IDENTIFICATION SAMPLE POINT: TRAIL JUNCTION A. USHO Chart 6049, 1944 (reliability 800d). Berg ggggggggg (SI-88:63: _ maunrain peak Cari track, trail L”, 7. .___-__._ Depth Curves and SoundIngs in Fathom: ,,,,, ,_ Read Mm mmnymg 100.000 mete, AerIaI photography: I'FEb'v IIIIy 1946; Z'Ian‘ 1949' Nom en I bay . . r r - LP _ _ __ Standard gauge rallwad' angle In“ '7" " _I__I_I_ RESEWWl Dal“. WC" L 2. :23:1IIIs:IlI/;;TIIIEADLD:IIIGIIIISTIE lo LEFT of 3“” 9:" _ _._ anchorage Slandard gauge railroad. double track WWW, ,, —-II--II—II— porn! and read LARGE rrgvres labelmg me "II" W—vw—sm‘ - 53991 90”“ 2’6” Salt EVaDDIZIOIS .. ”LL . . . m. L. ,_ 7. LP line either In the top or bottom margin, or Narrow gauge railroad, Single track , —1—‘—-r— APPROXIMATE uEAN DECLIMTIoN l955 on'rlrelrnerlsell: 43 2’5” ron CENTER or SHEET Estrmalelenihslrom gridllnelo mm: 9 "3”“ 3““ ”'"WI- “III” °' "WIN?” "a“ , —"_‘“‘"‘""' RIce Paddy; Marsh ANNUAL MAGNEYIL‘ calmer II EASTERLV 3 Locale IIrsi HORIZONTAL illdllne mow . . x I II dL RGE . . PW “"5""55'“ “"° » , ~ , A , , , u» diagram only I. on... mmr val-m. $3222.17: min. L.‘“.f§ir".'?§1.".i’".f Soul elevation in melers Checked; Unchecked , 746 )(M6 NIoa, Mangrove ”77777777777 , , To defermlne magnorr'c nor-Iii lino, conned the I530“ I? Smum I'Kl'l'es'D'dW onlhelmeilsell. 15 . ‘ n n num er; as: are or In In E h I I l . Wall; Levee; Cliff ,, Wailfi P"°' 9‘7"" "P °" ’I“ “’“II‘ “’98 °I II” ”'°P fire lull coordinates. Use ONLY In: Shmmml 5 mm “Mum WM 2 W h f b V l0 8 Woods; SCIIIII * "5" v i W with the value of the angle hem." GRID LARGER figures of lhe and number, SAMPLE REFERENCE: “3439152 “a” ”I 0 mm" Locmd 0 ICCI F‘v” ““ O I" I NORTH and MAGNETIC NORTH, 01 plotted on "ample- 815000 II IEDOIINIZ beyond 18" In any direction, I Principal navigahon IrglIl ol Iighlhouse; Anchorage ,, )I‘ 3/ lropical grass; CoconIIt grove the degree scale or Ibo north dye of the map. _ I WI" G'I‘I 1“" D's'inaImII 3" I56NLP439152 U DOT SW, CAROLI N E ISLAN DS 1958 TRUK ISLANDS CAROLINE ISLANDS 1125,000 TOL NW7 5° 6° 7° Military Geology of Truk Islands MAP 45 Underground Installations 3 s 3 a 1 151 3980” 151°32’00” 339 32/30” 340 341 42 48 5 7°22'oo" 7°22’00” 17‘ / '0 . l /’o 5'com Coral reel 22 23 Cgrlal@ [0/ 15 c I l ”/- 19 ora lee (k? ' cola/1:? has. 2 / 8” 814 14 ”digit? in 1, 15 " K .9 Coral \ 27 1 -- / 14 . 1 i 25 2 Z 3 1 21 12 18 23 4 Coral feral reel 1 22 LEMOTOL BA Y 21 Coral reel 1 151: Coral reel ‘ 17 2l 2 a . 17 .“12 22 .Corai-T-a gin Coral net???» 1 z ' 2 11 24 V 12 \ ‘ 29 8 3 ' 1,3) 1 8 /\ I a 13 \1/1 11 4 1d 12 3 11 18 21 39 1940 1 e5 24 Qfl‘w Hagen -. s 28 “Sea “%%% "w 812 E‘12 12 g, . g M 18 31 21 33 \\\ 18 j 35 24 r: 811 811 \ 1 1 R0 EN MISSIHN ‘ “'2‘" \ ég ‘x\ l ,i ’ 34 ,’ — I II 20/00" — “ \ ’“’“ 8 Q 15 4 fi, \5/ 2000 18“ \ \ x \ coral ‘\\ 28 15 \ 4 k‘ “\ coral , \\ 12 ‘~_/’ \\\\\\ 14 29 23 ‘~\\ [LICK HARBOR { \\ \ (L5)? . \‘x ‘r’l’ir.’ 64 81 10 \ng . ./).“M" ”a 2‘ I 810 0 mar \ \ ‘\(:/ \\:J 5 , ., , {a / 24 ‘\\ 29 ‘ 25 ~\\ \——0Rl ' EN WISENIF 11 \\\ 2 3.5. 25 \ \ f ‘x ‘x 17 3 \\ ‘~\ I . 22 29 15 x \ 2 _ / 22 sand and shefis‘xx \\\ J ' ., - coral 23 \\\\\\ T 8 V V (2) A 23 o. m x , \‘s\ 62 \ U U U; " 28 x n U K I ‘ ‘ / “ SUITABILITY FOR UNDERGROUND INSTALLATIONS \\\\ «(1; i‘ coral \ 11 4‘ coral ~ 809 \\ \ \ coral “09 Q9 ” 12‘ MAP TRUK ISLANDS is 2 25 T R UK L A G O O N In... an ’ Corgi 53"" 23 \“\ \‘K Sites Suitable for Tunnel-type Underground t ations Suitability terms, in order of decreasing suitability, are: excellent, good, fair, poor, and unsuitable. 36 \ x 29 ”4 . ., \\ 21 Site Rock Excavation Rock Disposal Overlying Underlying Access Suitability for . . \‘\\ com number type conditions characteristics of rock material material - Descriptlon \‘st 25 cm“ 7 L Tunnel type Bunker type “\i‘~\ 8 y Basalt Excellent Polygonal colum— General construc- Very thin Not seen Good from \ “x\ 28 to good nar jointing; tion; road build— soil east and Rock conditions good to fair for tunneling. Adequate cover available with short cgi'zal \\ \‘ \\ LG. 260 feet thiCk ing; add to talus; north; EXCELLENT UNSUITABLE gorizontal 63th:: anSLr/iage good. Stony overburden less than 30 feet thick. 25 23 19 19 \ 25* dump in sea poor from °pes 5"“ er 3 /°‘ 8 _ 08 coral /— fl \\ \‘xc \ southwest 1 308 08 . ; "_' \L COW 51:11 \ \\s\ Rock conditions fair to poor for tunneling. Adequate cover available with short "0'3" \‘i\ 18 L2. \‘ st 30 9 Undivided Actual 100 feet thick General construc- Soil up to Undivided Good to GOOD POOR horizontal entries. Drainage good. Stony clay overburden less than 30 feet @ ‘.‘ ”'a' \‘~\ lava conditions tion; road build— 30 fee: thick lava general thick. Slopes greater than 65%. Coral 27 1, /§‘ \\ unknown ing; swamp fill in places area 23 ‘1‘ // 12 \\\\ . . . Rock conditions good to fair for tunneling. Long horizontal entries or vertical 23 9 53"“ 40 I41 // 12 19 ‘\\ lO Undivided Probably lOO to 150 feet General construc— 5011 UP 1'0 Unleld-Ed Poor FAIR POOR shafts required to reach adequate cover. Drainage fair to good. Gravelly and 5““ 3 2, : 21 lava fair thick tion; road build— 30 feet thick lava stony clay overburden o to 10 feet thick. Slopes less than 65%. I / \\ . ”G I \\\ ing in places 53" i / _ , . . . . Rock conditions fair to poor for tunneling. Long horizontal entries or vertical Unle1ded Probably 100 to 150 feet General construc- 3011 up to. Unlelded G006“) POOR POOR shafts required to reach adequate cover. Drainage fair to good. Gravelly and lava fail" thiCk til-0n; road bUlld- 30 feet tthk laVa road to stony clay overburden 1 to 10 feet thick. Slopes less than 65%. 8 807 ing; dump in sea in places site ”‘ 07 See photo plate 15 B Rock conditions good to fair for tunneling. Vertical shafts or long horizontal POOR GOOD entries required to reach adequate cover, Clay soil overburden 10 to 50 feet \\ 17 11 , thick with relatively few rock outcrops. Drainage good. Slopes less than 65%. 29 \\ coral coral l/ \ lr’ Rock conditions fair to poor for tunneling. Long horizontal entries or vertical \ / shafts required to reach adequate cover. Drainage fair to good. Clay soil \ / POOR EXCELLENT overburden 10 to 80 feet thick with few rock outcrops and easily excavated. \\ // Slopes less than 65%. \\ , —— / M 17/30" 31 \ ,’ _ . . . . 17 30 \\ 30 ,1 No fea5ible means of tunneling to adequate cover. Sorls difficult to excavate, \ / UNSUITABLE UNSUITABLE saturated, or periodically flooded. Low flat coastal lowlands, mangrove swamps, ‘ 1’ fresh-water marshes, and beaches. Locally suitable for small hasty fortifications. _' 806 806000m.N \ i . 23 \ .’ 35' \\ I, 5 Selected site or area where a tunnel-type installation with a minimum floor space of 60,000 square feet \\ 35 J 0 could be excavated with only 100 to 300 feet of horizontal entry required to reach 100 feet of cover. 17 ‘x ‘i 31 (See accompanying table.) \\ coral \\ I coral \ X \ .ai it 17 19 \\ \ i \ x i 3 7°17/oo” ”'3' \ ‘ I f ‘ 7°17roo” 151°32’00” 339000m.E 32’30” 340 341 342 343 344 345 346 P 348 37’30” 349 350 351 151°39’30” 347 W856 5 Scale 125,000 Edition 2‘AMS (AFFE) 1 i o lstatute Mile Interpretations for underground installation construction by Elmer D. us, ARMY MAP SERVICE. FAR EAST . 57.041 . R.15 . 2/59 . 3,4(3 J 1 1 'r ' Patterson, 1954-1955. Prepared under the direction of the Engineer, Hq AFFE/SA, by the U.S. Army Map Service, Far 1090 500 0 1000 20,00 Meters East. Compiled in 1957 by photogrammetric (multiplex) methods. Coastal hydrography compiled 1000 500 0 1000 2000 Yards from USHO Chart 6049, 1944. Horizontal and vertical control established by Corps of Engineers, , H H H H E E 1951. Names transliterated in accordance with rules of the U.S. Board on Geographic Names. 1 0 lNautical Mile Major roads are classified by reconnaissance by the 64th Engineer Battalion(BaseTopoSraDhiC>, _ 1 r r COVERAGE DIAGRAM INDEX TO ADJOINING SHEETS 1952; other roads are classified from source maps and aerial photography and are not verified by reconnaissance. Coastal vegetation are classified by reconnaissance by Military Geology INT - \\\‘ - Branch, Intelligence Division, Office of the Engineer. Hq AFFE/8A, with personnel of the U.S. CONTOUR ERVAL IO METERS \\\\\\\\\\\\\ 4544 ll NW Geological Survey, 1955. Map not field checked. VERTICAL DATUM‘ MEAN SEA LEVEL \\\<§\\ \\\“\ . \ MAP 48 Underground installation compilation based on field observations 1954-1955 by Military Geology TRANSVERSE MERCATOR PROJECTION ‘\\\\\\\\§\‘\\‘\ Branch. Intelligence Division. Office of the Engineer. Hq. U.S. Army Japan with personnel of the HORIZONTAL “TU" IS BASED ON THE ASTRONOMIC STATION No. 2 (I951), \ \\\\\\\\\\\\\\ \\\ \ U.S. Geolo ical Survey. - - .\ - . ‘-,'€;'"\\\ ~~ .. \ 8 ISI 53/34.3' EAST OF GREENWICH. 7 21’37.7' NORTH §§N§§§§§§w$\\ 4544 lllsw 4544 III SE 4544 ll SW LEGEND HYDROGRAPHIC DATUM: APPROXIMATE LEVEL OF LOWEST LOW WATER NMQ§T®§N \\\\ MAP 44 MAP 46 MAP 49 ROADS BLACK NUMBERED LINES INDICATE THE 1.000 METER UNIVERSAL TRANSVERSE MERCATOR GRID ZONE 56 INTERNATIONAL SPHEROID All . . mm“ THE LASY rune: DIGITS or THE GRID NUMBERS ARE ouirreo \ 4543 IV NW 4543 N NE 4543 1 NW hard surface. two or more lanes wide , None Built-up area i, i , . ,, W, on -" MAP 45 MAP 47 MAP 50 loose or light surface, two or more lanes wide i... ,, None Church; SCllDDI: Cemetery 77A“- 777777 :\\\ \\ hmdsmhu,omlmewMe,_ in, , l, None Umnolflnyihm;swmemw mfl ,l,i, COMPILAUON METHODS loose or lighl surlace. one lane wide "iii," ,i, None Wreck; Sunken; Exposed i, ,iiiiu a I ‘0”, Photo-stereo Photo-planimetric Map .7 0 ii on ‘ - lmw _,__,_, - GRID ZONE DESIGNATION: lo GIVE A STANDARD REFERENCE on \ _ GLOSSARY fair or dry weathei.‘loose suilace, two or more lanes wide , Sunken rocks, Foreshore llats ill on u “Ls ”"5 SHE“ To MARE“ m METERS m ' Berg mountain, peak Fair 0i dry weather. loose surlacei one lane wide W. i. :1 ;=:_ Roclis bare or awash; Reel ll, Will , ._ 3 “LS 100,000 iii. SQUARE IDENTIFICATION SAMPLE pom; TRAIL JUNCTION A. usuo Chart 5049, 1944 (reliability good), Nom en h bay anc ora e Cari track; trail lliilllliii, iii, __-_-.. Depth Curves and “ ‘ in fathom: Lite-d Wm idenhlrmg 100,000 mm, Aerial photography; l-Feb., July 1946; Z-Feb. 1947- garnet" cape. poignt q if n th ii s: LP Standard gauge railroad. Single tract fill. , —+-+—t— Resewom Dam; Ditch 7777i iiiflfiiWAr \ 2.102::ISsTJéRTIEADErrIdIIIneto LEFT ol 81 d d I d. d III I II iii,” , w poinland read LARGEligureslabelinglhe 3" 3‘ gauge ””03 0“ 9 I30 2"” Salt evaporator: "7W fill, LP line either iii the lop or bottom margin, or Nanow ungaiaflmad onyelmck , _i_u m. APPROXIMATE MEAN DECLINATION l955 onihehneinuk 48 _ I'd" FOR cENfER 0F SHEET Estimate tenths lrorn grid line to point: 9 Narrow gauge railroad, double or multiple track ,_ -w—“—vr- Rm Paddy; Marsh ._.,_,l. ¥#_U t‘ “ “mu“ “Grime CHANGE iI usrmr 3. Locate lirstHORIZONTAL grid line BELOW . . /' . point and read LARGE ligures labeling the Power transmission line Mi, 7 iii 7 “i ._ Egg lg use diagram only io oblai‘n numerical rub-s. line 911"" in in. left or right margin, or . . . , . I x N' ; M o e ___,_ ._,_l eriill,ll______ - - - , IGNORE the SMALLER ligures al ii in i ‘r ll: 11 Spot elevation in meters. Checked, Unchecked ,i,, i as 155 ”’3 angi V 7"” d°""_"'"e 2""th mm” "M’ (ma "n grid number; these are lor minim; ggtimeatrteentshes 1mm grid lineto paint: 1 Wall' Levee CIIII % DE} P‘V°' P°"" "P °" Ibo M “99 “W." m the lull coordinates. Use ONLY the . , Will". — Wu Ta Woods; Scrub l, "#77777! vi", m w,” a, ,i,‘ angle (”W GRID LARGER iiiiuies of in and number; SAMPLE REFERENCE: LP489111 WatelWhEEI 01 mi”? Located DIJICCI , ,, .7» 0 cm" NORTH and MAGNETIC NORTH, a: plofhd on example: 806000 ll reporting beyond 18” in any direction, I A Principal navigation light of lighthouse; Anchorage _,__i * \1/ Tropical grass; Coconut grove ,wmlllllfiA»- [:‘EI the degree scale ml the north edge of "in map. _ We” G'm 1"“ D“""’“°"' “1 SSNLP489111 TOL NW, CAROLI N E '8 N US 1958 ‘ Military Geology of Truk Islands CAROLINETRIUSL'SALNNBSS 125,000 I] D G VT S E 0° 2° 3° 4° 5° 6° 7° MAP 46 Underground Installations 3 a 151°39I30I 352 40/000353 354 355 355 357 42/30' 358 359 360 361 362 45mm 353 364 65 151 47IooI , . 7°27Ioo' 7 27I00I I 30 29 I coral 29 28l core mfg Sites Suitable for Tunnel-type Underground Installations 34 Site Rock Excavation Rock Disposal Overlying Underlying Access c201“ number type conditions characteristics of rock material material U L A L U ~ 823 823 23 .11 dd 23 l Basalt Good 150 feet thick General construc— Soil u to Not seen Road at 55 , coral . - P Ln tion; road build- 30 feet thick foot of I 29 ing,‘ dump in sea in places hill ‘ coral E 0 7' 30 31 T R U K L G 0 0 N l Breccia Good to fair 160 feet thick General construc- Soil up to Breccia Good A tion; road build— 50 feet thick 31 i ‘I 55 54' ing; dump in sea on lower slopes I ra 1. 30 ‘j U 0 0 7' 17/” ‘1, l Undivided Good to fair 160 feet thick General construc- Soil up to Undivided Good if 29 / ' lava tion; road build- 30 feet thick lava old road 27 , 3 >/ ’1’ Dim/I ; ing; swamp fill repaired 822 28 2 2 I .. 8 » ,' 22 22 “W“ 95,73, : 24/ 2 Undivided Good to fair 210 feet thick General construc— 8011 up to Undivided Excellent \w’ lava tion; road build- 50 feet thick lava 21 ins 29 C: '_ ______ "coral ________________________________ :t’ —————————— 7—‘________________“_T‘___T___'T”T“"T"_—_______—T'T—____—___"‘ ‘__"'T““___"‘T—____:’__________""'____ fir—3| _______ —'—— """""""""""""""""""""""" " ,,/r In I ,z’ I 27 A’,,.—’ @ I z/ a I. 3 y Breccia Good to fair Indurated breccia General construc- Soil up to Breccia Poor; is, 7/4”” T‘\~~--\_ ,x” i 160 feet thick tion' road build- 0 feet thick foot th ,x”’/ 53 1 4 “~~L\\\ 55 28 [,x 57 58 59 a 60 ‘. .’ 3 pa. ‘ /- -2,“ coral , coral i breaks thro ing, dump in sea to site 1,,» 23 I ~~c_ ,-/”’/ 28 I \‘T‘\ \L 2‘ 18 13 ‘1‘ fragments; widely —/,,/ . ‘\-~-,,\ l spaced or no .-~. I 3 L\» \ =;.-..Cor-IreeI I 1%... TRUST TERRITORY OF THE PACIFIC ISLANDS \ Joints; fine- 28 I, (U.S.A. ADMINISTRATING AUTHORITY) 17 16 \\ grained dikes 821 CO,“ 2 TEECOHI reef Ii 2 1 ll. ,. \ - 821 33 12 9 2; 22 ll Breccia Good to fair Indurated breccia General construc— Soil mostly thin Breccia Poor; 26 w 250 feet thick; tion; road build- but up to 30 footpath coral 24 , 23 1 fine-grained ing; dump in sea feet thick in to site I °°"' 18 ‘3 dike 5 place is l l I I $3.1 17 Uncovers Meet 5 Breccia Good to fair Indurated breccia General construc- Soil mostly thin Breccia Very poor; 11 200 feet thick; tion; road build— but up to 30 footpath l V“ fine—grained ing; dump in sea. feet thick on K“ :~:3‘/;\- 04/ dikes lower slopes 17 x “\i“ ~ - 15 x ‘x- ‘x 8 25,00, °°"’ [a 12 \\ ~~\ :5 \\ R 17 14 6 Breccia Good to fair Indurated breccia General construc- Soil mostly thin Breccia Very poor _ 820 820 __ QEN— \ l,” \ 20 m cm, 230 feet thick; tion; road build- but up to 30 25’00' \ ‘\\ ‘\\ l \\ :tx‘i‘ 21 fine-grained ing; dump in sea feet thick on \ ‘\\ l 13 '..,%“3P\’ \‘32 dikes lower slopes \ ‘ 7 Undivided Good to fair 160 feet thick General construc- Soil up to O Undivided Good if T R U K I S L A N D S lava tion; road build- feet thick on lava old road ,‘ _________________ \ ing; dump in sea lower slopes repaired I ~~~~~ «---:“~»e«—---_ \ -i_‘_\__\ _______ “a--- 22 y See photo plate in 15 1‘ 19 ~~~~~~~~~ ,g_:“~~«»-__,_‘ 19 1‘ 13 “T“~<~___g:: :::: 10ral_< : ‘1 16 co‘ral TTTNT “““““ —:: TTTTTTTTTTTT I “meow reel ‘\ 23 ~~~~~ TTTT‘T“‘:::TTC—“E‘E~87e_f‘k‘rr I 15 Unun en Chéfial ‘ --------- __“‘r __________ a 819 \\ 19 : __________ \.\ 19 19 Cor-I reel' . \\ 14 17 I \\:‘ \ \ 22 l \C\ 18 19 22 13 i > 15 I 22 \\\\ coral 21 .. x‘) .. Coral reef _ 19 I \\ \\ I \\ ‘~. 17 1 ‘~\\“\. lTY FOR UNDERGROUND INSTALLATIONS i 17 i | A l 17 5 MAP, TRUK ISLANDS , i ,5}; \ | Suitability terms, in order of decreasing suitability,,are2 excellent, good, fair, poor, and unsuitable. l‘ 17 l -- 14 I If s\ Suitability for I / n \ 818 818 Unit Description I «can. I 20 l ‘ I Tunnel type Bunker type 11 \\:O 3<<13 , Rock conditions good to fair for tunneling. Adequate cover available with short 15 1511*. I EXCELLENT UNSUITABLE horizontal entries. Drainage good. Stony overburden less than 30 feet thick. ,2 sand I Slopes greater than 65%. 17 Rock conditions fair to poor for tunneling. Adequate cover available with short 18 GOOD POOR horizontal entries. Drainage good. Stony clay overburden less than 30 feet thick. Slopes greater than 65%. 18 8 817 w. a Rock conditions good to fair for tunneling. Long horizontal entries or vertical ‘77. 17 FAIR POOR shafts required to reach adequate cover. Drainage fair to good. Gravelly and stony clay overburden 0 to 10 feet thick. Slopes less than 65%. \\ Rock conditions fair to poor for tunneling. Long horizontal entries or vertical \\ POOR POOR shafts required to reach adequate cover. Drainage fair to good. Gravelly and \\ \ stony clay overburden 1 to 10 feet thick. Slopes less than 65%. \\ \\ 64 65 21 5 ‘1‘ 16 1a \ I Rock conditions good to fair for tunneling. Vertical shafts or long horizontal \\ \\ p00R GOOD entries required to reach adequate cover. Clay soil overburden 10 to 50 feet \\ \ thick with relatively few rock outcrops. Drainage good. Slopes less than 65%. l__ \ \\ ' \\ ‘ ,r . . 1* 1 : I“ .. 1 . ,_7 ., - ~ 10 /3,, 1‘1“, 816 316 Rock conditions fair to poor for tunneling. Long horizontal entries or vertical . ' . .. T _I'.", ‘ "I. ‘ “:1... ' ’ ' ‘ ' '- ' ' ' . ' - ' ’ \ .15. ,I \ \ 18 shafts required to reach adequate cover. Drainage fair to good. Clay soil ‘ ‘‘‘‘‘ ’I \ \\ POOR EXCELLENT overburden 10 to 80 feet thick with few rock outcrops and easily excavated. OROR El DOT ROAD 13 \\ Slopes less than 6596. 11 ('nChor'Ke) 18 T“ ‘1 _____ \\\ 18 sand carol 10 \0 * T‘T‘xlfi \\ \ 13 55 _ 3 I a~~\\\ \\ i_1 .. . No feasible means of tunneling to adequate cover. Soils difficult to excavate, 7 12 {’3‘ 3‘" \\\ \\\\ / 17 ,7" UNSUITABLE UNSUITABLE saturated, or periodically flooded. Low flat coastal lowlands, mangrove swamps, _ \ m,.,__‘§t.f““;m\wm 31 13 cm <3 \‘\\ \ ”’io~ ‘4 _ . . .. . . to . 3“ . Tumwifilfmmum‘ 39,. > . 2 x, x“ 22,30, __ 0‘ y .> fresh water marshes, and beaches Locally suitable for small hasty fortifications %g{‘fit::‘:“ . 1. . \‘afiwfiszfififitztfifih . _lk7 l I \ \\ 15 ______ / 7 _ 22/30” ' ‘lilm xxuigmlrmw 4 2 / \ ______________ co rel / . I’II'ID'M ‘W [In - 61 17 17 ’16 \ \\ ________________ . Selected site or area where a tunnel-type installation with a minimum floor space of 60,000 square feet 2 12 _/ _____ ”C? ...... 13 ’ could be excavated with only 100 to 300 feet of horizontal entry required to reach 100 feet of cover. 31 10 1 10 \\\ (See accompanying table.) 8 2 1 \\ i\ corul \ \16 815 snowman. 15,, a la 5% ‘2 x E 10 11 9 ‘11:; 11 ’ \ 13 i x I I0 / . 11 3 ‘5‘ 7 \\ I 8 C I . 21 1 0 13 18 ! cor-I 14 L 15 I: : ora 6‘ \ I 13 I 11 '°\ i l 12 7.22100” __.z \ 13 : shells i K 0} I15 3\/ 8 3\ \6 1 1 MOM.“ 7°22’00l, 151°39’30” 352000m,E. 40’00”353 354 355 356 357 42’30” 358 359 360 P 362 45/00” 363 364 365 151°47’00” 361 W856$ Scale 1'25000 Edition 2-AMS (AFFE) 1 t o isiaiute Mile Interpretations for underground installation construction by Elmer D. u.s. ARMY MAP SERVICE. FAR EAST - 57-041 - R-15 .2/59 . 3.4c E2}! . Patterson 1954-1955. Prepared under the direction of the Engineer, Hq AFFE/8A, by the U.S. Army Map Service, Far 1000 H 5?O_‘ H l_? 1°00 2°00 Mews ' East. Compiled in 1957 by photogrammetric (multiplex) methods. Coastal hydrography compiled I 1000 500 0 1000 2000 Ya d from USHO Chart 6049, 1944. Horizontal and vertical control established by Corps of Engineers, [ 1—1 1—1 ,_, ,__—_, H E r S 1951. Names transliterated in accordance with rules of the U.S. Board on Geographic Names. 1 0 lNauticaI Mile Maior roads are classified by reconnaissance by the 64th Engineer Battalion(BaseTopographic), 1952; other roads are classified from source maps and aerial photography and are not verified E E COVERAGE DIAGRAM INDEX TO ADJOINING SHEETS by reconnaissance. Coastal vegetation are classified by reconnaissance by Military Geology Branch, Intelligence Division, Office of the Engineer, Ho AFFE/BA, with personnel of the U.S. CONTOUR INTERVAL ‘0 METERS WITH SUPPLEMENTARY CONTOURS AT 5 METER INTERVALS Geological Survey, 1955. Map not field checked. VERTICAL DATU": "EA" SEA LEVEL 4544 11 NW Underground Installation compilation based on field observations 1954-1955 by Military Geology MAP 48 Branch, Intelligence Division, Office of the Engineer, Hq, U. S. Army Japan with personnel of the TRANSVERSE MERCATOR PROJECTION \§ U.S. Geological Survey. HORIZONTAL DATUM Is BASED ON THE ASTRONOMIC STATION no. 2 (1951): K 151°53’34.3' EAST OF GREENWICH. 7'21’37.7’ NORTH ‘1» ‘S‘N‘ESNN “o\\\\<‘§§\$‘§\§\ 4544 IIISW 4544 III SE 4544 ll SW LEGEND HYDROGRAPHIC DATUII: APPROXIMATE LEVEL OF LOWEST Low WATER {\\ i~§§$§§§\\\\\ MAP 44 MAP 45 MAP 49 u .; . n..\~.\t ROADS BLACK NUMBERED LINES lNDlCATE THE 1.000 METER UNIVERSAL TRANSVERSE \ \\‘\\\V§§§\:§i§§\§\§§§ ® All weather IERCATOR GRID. ZONE 56. INTERNATIONAL SPHEROID \§\\\\\§\\s§cf\\\\§ \ 4543 IV NW 4543 N NE 4543 I NW 1 iat'M‘. .\_\\“\~. 3e hard surface, M w more lam wide None Bump am m: LAST THREE oicirs or THE GRID uuunens ARE ouirreo \{\\\\\“ “\N _ —_ . . on \\\\\ \ \\ MAP 45 MAP 47 MAP so loose or Iighl surlace. two or more lanes wide None Church, School, Cemetery \\\\\\\\\\\\“\\\\\\\ hard surface, one lane wide —_ None Limit of danger line; Submerged reel 4.”, COMPILATION METHODS loose or light surlace, one lane wide ___._.. None Wreck: Sunken; Exposed 0.10, on Photo-stereo Photo-planimotrlc Map Fair or dry weather, loose surface, two or more lanes wide 2 Sunken rocks; Foreshore Ilats on u ””5 GR”) ZONESDGEfiGMTION: :3.g"Sliz‘nsxnflzfsgfigiagzg: W I: GLOSSARY Fair or dry weather. loose swim. one lane wide ======== Rocks hare or awash; Reel 3 I 1L5 100,000 M. SQUARE IDENTIFICATION SAMPLE Pomr: ; SCHOOL A. USHO Chart 6049 1944 (reliability good). 33:; $32,103:; Carl track; trail _______ Depth Curves and " " in fathom: Lima mm idenlilying 100,000 mm, A971" photography: Fol, July 1946 . . square in which the point I’es: LP Standard "m "'"m’ ”we "a“ — " ‘. Darn; Ditch 2. Locate iiui VERTICAL lgriiiliine to tin or sundam [lull "mom doub'e "a“ LP point and reed LARGE figures labeling the ~ . a’o" Salt evaporator: line either in the too or bottom margin, or Narrow gouge rlilroad, Single track I I APPROXIMATE MEAN DECLINATION 1955 1 on in. 1m. 1m"; 58 . _ a e ’ ron CENTER OF SHEET Estimate tenths from grid line to po'nt: "WW KW“ ”"10“: double 0' "WNW ""3" Rice Paddy; Marsh ANNUAL MAGNETIC CHANGE l' EASTERLV 3. Locale first HORIZONTAL glidline B'ELow . . , / . point and read LARGE figures Iahel'ng th Power transmssiori line _ ......... , u' u. diagram only 99 ouch. m! values. line either in in. left or right marlgin, a: 16 . - . . x x Illa; " _ - ~ ‘ IGNORE the SMALLER figures of any (h I‘ '1 ll; soot elevation Il‘l meters. Checked, Unchecked us as T? “W": "PW" M '"‘" “W M ma number; these are Ior Iinding gziimzi;ni°.:iisii'smm grid line to point: VII": levee; Clili _._............... Al PM” P°"" V °" "" W“ “’9' °' '5' "'“P in. Iuii coordinates. Use ontv llle Wt ll I l ." L ted b'eci ¢ To", Woods; Scrub villi "0. value of ”in angle between GRID [ARGE'Rligures olthe grid number; SAMPLE REFERENCE: LP589154 "I“ 9' ° "1'? W M M 0 worm and MAGNETIC Monmaspion-don """W 815 000 II "porous beyond 18' many aircciion. Principal navigation light oi lighthouse; Anchorage _ * ~12 Tropical grass; Coconut grove uni-loom xdeaifhe nodh edge of the map. — 9"“ 0"“ 1"“ ”"mmm- "‘ 56NLP589164 U DOT SE, CAROLI N E ISLAN DS 1958 TRUK ISLANDS 7' Military Geology of Truk Islands CAROLINE ISLANDS 125,000 - f © IL! N E 0° 2° 3° 4° 5° 6° 7° MAP 47 Underground Installations L MW 151 "39/301! 35 40'00» 353 354 355 356 357 42/309r 358 359 360 361 362 4mm 354 365 151'47900! . , 7'22’00' 7 22,00 ‘ M 7 \ 1 k f l 7 12 CW" ' colrlal 12 I 7 22 I C/ C 11 B ,2 11 \ b \ 3 “I 16 \, \\\\_/ 15 n 14 8 914 14 \ 31 14 63 \7’011 8 2 " _ 6 11 GE 15 6 v 3 12 C 10 / To 0 2; J ‘ a; m 1 I ‘-: 13 @ng 16 73 51 4} 51 . , ._ ~ .- ~ 3 , k 5%- ' carol 12 (lb o/< 21> coy2al 4 ‘0 8 813 11 ' 1 item , 13 49L 7‘ ‘ ‘ 13 $11.. ” 13 1 ' '0' mag: 11, w / 1 \ 1} Z . m, - . ._ \ '- . ‘ \o 20 12 a OROR EN . '- ‘ ., ~‘- , ’ 0/, i 21 3 / 13 15 \\ > ,. v. i coral \\ 8 .- \ ' 'i; , : . .f colrgl 3 J I:\ ' ’ - ‘ 17 (”a , q, , 20 6 > I O ’5 coral r 53 r 22 2 13 3 1 , 4 l_ 23 58 .19. 59 60 Q 6 3, 12 @ m. 65 )‘xL/l I 7 f 15 a 11L i 19 \Io 3 i coral \0 ,- ' 23 16 k‘x\ ', 12 24 coral 21 y 11 *— ,fli coral 23 coral l0 u, 4 ,‘ I coral 9 \ 812 812 3 ' l 12 T. 15 i / \\ i l 2 ‘1 13a 1' I S L A N D S 6 cog: /— OROR N PENIOR l [7' 1 19 9 “i ,l/ 3 r_.. indicates swept depth area in feet fl ‘1, 16 15 3 i” , 1', IO cgrgal 2: 421 {’X coral \ / -X I *5 1 1 j a 19 \- \ 11 24 \ 2 coral 811 811 \\ is 11 \ \ 1 ‘1 28 2, 20'00” —— \\ 54 ‘1‘ 17 22 5 —— 18 20/00” \ \ 5 ,--— \\ l/ \\ \ 31 ’° "\ K L A G 0 0 N -_- a ‘\ 23 20 \ coral \ 20 \\ coral \ \\ SUITABILITY FOR UNDERGROUND INSTALLATIONS 910 810 o 1 ' 9 MAP TRUK ISLANDS 18 \ "1 , a $ // 22 I 1 \\ Suitability terms, in order of decreasing suitability. are: excellent, good, fair, poor, and unsuitable. I 44 )23 \ Xi- Suitability for g; Descfipfion 20 . 55 Tunnelfype Bunker type C°TL—_,——""'/— Rock conditions good to fair for tunneling. Adequate cover available with short .-———T""—w— EXCELLENT UNSUITABLE horizontal entries. Drainage good. Stony overburden less than 30 feet thick. 25 Slopes greater than 65%. coral 17 22 309 809 Rock conditions fair to poor for tunneling. Adequate cover available with short GOOD POOR horizontal entries. Drainage good. Stony clay overburden less than 30 feet 22 thick. Slopes greater than 65%. 28 A3 Rock conditions good to fair for tunneling. Long horizontal entries or vertical FAIR POOR shafts required to reach adequate cover. Drainage fair to good. Gravelly and l , \ stony clay overburden 0 to 10 feet thick. Slopes less than 65%. 23 i —--i --------------------------- I/ \\ 21 , a..\ - T‘T‘\~‘\ 1 1.2.9.1 \ ,// \\\ ' ' /—_‘\ 11% 23 \\\/ \\ 3—31 Kr \ Rock conditions fair to poor for tunneling. Long horizontal entries or vertical / 1 \‘ 19 \\ \\ 1" 2.31-1\ POOR POOR shafts required to reach adequate cover. Drainage fair to good. Gravelly and 1’ 12' I ———————————————————————————————————————————————————————————————————— \ x ‘\ ,' stony clay overburden 1 to 10 feet thick. Slopes less than 65%. 2° 2° / cm 7‘ 808 8 2‘ 08 . \ 9 . . . a «1 3 13,23 1’ 21 ‘ ‘1 \ . —,_, if“ \\ Rock conditions good to fair for tunneling. Vertical shafts or long horizontal \‘,\3 ‘1‘ ‘ 21 \‘\\ POOR GOOD entries required to reach adequate cover. Clay soil overburden 10 to 50 feet \\ i \ thick with relatively few rock outcrops. Drainage good. Slopes less than 65%. ‘~~—’ 21 \ fig! \ .. . . . C 2 52 53 54 19 55 23\\ 56 57 Rock conditions fair to poor for tunneling. Long horizontal entries or vertical 63 64 5 65 17 24 21 ~\ 2 v POOR EXCELLENT shafts required to reach adequate cover. Drainage fair to good. Clay soil 1 27 sand \\ 2 I 17 overburden 10 to 80 feet thick with few rock outcrops and easily excavated. \ \ Slopes less than 65%. l I \\ 24 ¢ \ '5 \\\ No feasible means of tunneling to adequate cover. Soils difficult to excavate, 31 \x .13.. UNSUITABLE UNSUITABLE saturated, or periodically flooded. Low flat coastal lowlands, mangrove swamps, ,x~\ 807 807 \\ fresh-water marshes, and beaches. Locally suitable for small hasty fortifications. '1' K‘s/)1 \ I | \ I Gshnd) 24\\\ .’ 21 15 19 s g r \ é; 1o ‘xs : .le 1° 21 18 \“~\\ I coral ‘\~\\ ,' 1_1indicates swept depth area in feet “\ \\ i 23 7 \\\\ i oral 23 21 IO ‘\\ 25 I «339d 2'1 coral 18 \‘Sr 5 17130” —— 7 [r \\ i —— 26 _. 17/30» £1 I (r ‘\\\ 1 corn] ’ ‘s 1 1 st. 8 8 000m. 25 7° ~, 06 06 N. 06 \ / 21 06 i i : 06 21 3 x 1’ l 23 and 29 27 \\ ‘\ r, i \ I \\ 13}. 23 / 24 : iii. 29 \\ / , I 13 \\\ 1’, 54.9; i 1 ‘\\ i l 25 23 d4 22 \\\\ I, 3 cgraal °°”' 16 '/, 25 ‘x.\ 23 I], : 2 , 2 3 “~\\ ’ I 4i 27 7°17100' I @323, 15 1., m 17 23 i / \ 24 \~\\ 22 r’ 1 30 °°"' 717,00, 151°39’30” 352000m.E_ 40'00” 353 354 355 356 35] 42/30' 358 359 360 P 362 45’00" 363 364 365 151‘47’00” 361 W855 5 Scale 125,000 Edition Z-AMS (AFFE l . . . . . ) 1 2 9 35‘3”“ “"9 Interpretations for underground installation construction by Elmer D. U.S. ARMY MAP SERVICE, FAR EAST ~ 57-041 -R-15- 2/59 -3.4c ‘ Patterson 1954-1955. Prepared under the direction of the Engineer, Hq AFFE/BA, by the U.S. Army Map Service, Far 10‘00 500 o 1000 2000 Me‘e's ' . . . , p—q b—fi h—a F—4 F—4 p————————————————————————4 East. Compiled in 1957 by photogrammetric (multiplex) methods and from 1:55,180, USHO 1000 500 o 1000 2000 Yards Chart 6049, 1944. Coastal hydrography compiled from USHO Chart 6049, 1944. Horizontal and , ,_, ,_, ,_L ,_, ,_1 , vertical control established by Corps of Engineers, 1951. Names transliteratevd in accordance 1 1 O 1N t' lM'Ie with rules of the US. Board on Geographic Names. Coastal vagetation are classified by reconnais- . . r j . . , au ica i sance by Military Geology Branch. Intelligence Division, Office of the Engineer,Hq AFFE/BA,‘with personnel of the U.S. I ‘ al S . ' . Geo ogic urvey, 1955 Map not field checked CONTOUR INTERVAL 10 METERS WITH SUPPLEMENTARY CONTOURS AT 5 METER INTERVALS COVERAGE DIAGRAM INDEX TO ADJOINING SHEETS Underground installation compilation based on field observations 1954-1955 by Military Geology VERTICAL “TU”: MEAN 55“ LEVEL Branch, Intelligence Division, Office of the Engineer, Hq, U.S. Army Japan with personnel of the U.S. Geological Survey. TRANSVERSE MERCATOR PROJECTION 4544 ” NW HORIZONTAL DATUM IS BASED ON THE ASTRONOMlc STATION NO. 2 (1951): MAP 48 151°53’34.3' EAST OF GREENWICH. 7'21’37.7’ NORTH ‘ LEGEND HYDROGRAPHIC DATUI : APPROXIMATE LEVEL or LOWEST LOW WATER 4544 H sw 4544 ”I SE 4544 " sw ROADS BLACK NUMBERED LINES INDICATE THE 1.000 METER UNIVERSAL TRANSVERSE MAP 44 MAP 45 MAP 49 A“ "my ‘ MERCATOR GRID. ZONE 56, INTERNATIONAL SPHEROID hard surface, [W0 0! mme lanes wide ____ None Bui|[.up are; W NONE 7 , 6N THE LAST THREE HIGHS OF THE GR’D "UHBERS ‘RE OIITTED loose or “gm surface, two or more lanes wide None Church; School; Cemetery __...._.__..__ 3 11' 189W i\ 4543 IV NW 4543 N NE 4543 I NW hard surface, one lane wide ___________ None Limit of danger line; Submerged reel MAP 45 MAP 47 "Alp—51° loose or light surlace, one lane wide ____ None Wreck: Sunken; Exposed 4.”, - 7 fair or dry weather loose surlace two or more lanes wide WNW.-.“ ~~ Sunken rocks foreshore Ilals o m on GR”) ION: DES'GNATION: 7° 6"" A ST‘ND‘RD REFERENCE 0N COMPILATION METHODS ' ‘ ’ OR 84 MIL5 THIS sum To NEAircsr 100 METERS Ph°‘°'5t°”° M” . r ,,:;:::; - anus . V Fair or dry weather, loose surace, one lane wide A- Rocks hare or awash, Reel 100,000 M. SQUARE IDENTIFICATION 5mm: pomT, x “2 W 0 GLOSSARY h Carl "M; "a” ——“—‘—— _._._____ Depth Curves and m Fathoms 1. Read letters identifying 100,000 meter LP A. 155,130, USHO Chart 5049' 1944 (reliability good). Uror an :n: Drag: . r. m H ; nun on ___._—c p , porn Standard gauge railroad, srngle track — —+—+—4— Reservoir; Darn; Ditch CIV 2‘ :23: msJERTIEADBEM'm: to LEFT 0! Aerial photography: July 1945. Slandard gauge railroad, double lraclr LP point and md LARGE figures l-beling the a’l” Salt evaporator: line either in the top or bottom margin, or Narrow gauge railroad, srngle track APPROXlMAYE MEAN DECLiNATION 1955 onthelmeilself: 53 ’1” FOR CENTER or SHEET Estimate tonlhs from grid lineto point: 5 "allow KNEE lallload. double 0' "WWW "a“ the: Paddy; Marsh _______—_._.____ ANNUAL quNETic CHANGE I' EASTERLY 3, LocatelirstHORlZONTAL gridlrng azLow P . I‘ 7” p i, . _ . pornt and read LARGE figures labeling the ower transmissmn ine ___— .......... . [:l. Uu dlcgmm only lo obtain Mm] values. 11". am." in in. rm or “gm margin, or Spot elevation in meters: Checked; Unchecked ‘Ms ”/56 "m; Mangrove '_”—_‘—‘_ ‘ T° dawn“ ""9”": "W lino, cm the if:055,33:"iiitizrt'iirrxa'.3: Egifliilrfgiifi'imm [rid 1,". to porn!‘ 134 Wall Law 01111 afifi [3:] pin» porno "P" on the mili dye or u» now: m m" mam,” U“ 0,,” m - ' ' A WOOdS; SEND M with the value of lhe angle between GRID LARGER liaures oi the 1116 number: SAMPLE REFERENCE: 351 4 w1 h l 1 'll 1 id Den :31 TOW I 806000 LPS 3 a 9"" ee 0 m' i “ca 9 0 I —— 0 NORTH and MAGNETIC NORTH, as plotted on dumps: ll reporting beyond Is“ in my direction, Principal naVigalion hum of lighthouse; Anchorage ._ * 3/ lroplul grass; Coconut grove DD methane scale at lb. north edge of the rum. " prefix and Zone Designation, n: 56NLP535134 TOL N E, CAROLI N E ISLAN DS 1958 TRUK ISLANDS CAROLINE ISLANDS 1:25,000 MOEN NW7 Military Geology of Truk Islands MAP 48 Underground Installations 1958 151-47/00' 366 4730' 367 368 369 370 371 select 372 373 374 375 52/30: 376 377 378 379 151-54I30' . , - I I 7 32 00' i 27 \ \\\\ I/ I I 16 I 35 7 32 00 \ ’ coral /,,_‘\ coral 22 29 r’”\ \\O\ /1'9 3 \X 30 17 / \ ‘ / \ coral coral I 12 I uncove's 1 monk sand grid shells I/ 2 \\ \\ coral /l \ \ I l \s\ \ z \\ I ' \\ 23 xix 17 x 34 ‘i . 22 ‘ coral / \\ \I El ree \I Iiil 24 \\ g \I 4 //l 24 7 17 \ ‘\ coral // II 3‘ / x 5 l “3'3“ 5 39 37 23 \\\\Q / Coral \\igV—/ sand coral \V « 8 332 32 3° 32 32 32 27 coral 27 ,5; . . . 30 27 Sites Suitable for Tunnel-type Underground Installations Site Rock Excavation Rock Disposal Over-lying Underlying Access cg?“ number t conditions characteristics of rock material material M 0 E Ill 35 l y Andesite Very good; Polygonal colum— General construc— Soil 10 feet Conglom— Excellent 36 ”P 27 possible nar jointing; tion; road build— thick erate 831 831 31 29 if 1 \ rock fall platy fracture; ing; dump in sea ll- feet _“31 l near cliff 160 feet thick thick 23 < / face ,_, indicates swept depth area in feet 36 2 Andesite Good Polygonal colum- General construc— Basalt 30 feet Breccia Fair 53"" 29 nar jointing; tion; road build- thick and thin 77 78 7 66 67 68 69 70 7I platy fracture; ing soil 9 75 feet thick 3 Basalt Good; some Polygonal colum- General construc- Soil 10 feet Not seen Excellent 5:358, support nar Jointing; tion; road build- thick if road 8 22 saglls needed near irregular frac- ing; swamp fill improved __30 35 830 30 25 30 entries ture 200 feet thick 23 24 it Basalt Good Polygonal colum- General construc— Soil up to Undivided Fair; no sand and shells nar jointing; tion; road build— 30 feet thick lava road platy fracture; ing cgrlal 29 60 feet thick 31 l . . . d l 28 29 35 5 Andes1te Good Polygonal colum— General construc— 8011 up to Conglom- Fair; 5"" / 30'00" - + 29 nar jointing; tion; road build- 30 feet thick erate abandoned /l—— 3000” platy fracture; ing 10 feet road to I 27 829 29 110 feet thick site “29 ‘ \\ 829 y See photo plate 13 ,9 30 , TRUST TERRITORY OF THE PACIFIC ISLANDS 633,, .53 22 '@ U.S.A. ADMINISTRATING AUTHOR TY) \l 28 30 1 28 22 shells all I, ’ (I sand z” 9 / /3 / 1 / 8 828 it 28 28 ,, 28 / o \\ [x \ I/ I8 I 29 29 / cyal \\ |\ coral [l coral ,’ \1‘\\\ \\‘~’/( /// D I 29 27 SUITABILI | Y FOR UNDERGROUND INSTALLATIONS TRUK ISLANDS/ MAP, TRUK ISLANDS Suitability terms, in order of decreasing suitability, are: excellent, good, fair, poor, and unsuitable. 8 827 W Suitability for 27 Unit Description Tunnel type Bunker type 12 Rock conditions good to fair for tunneling. Adequate cover available with short EXCELLENT UNSUITABLE horizontal entries. Drainage good. Stony overburden less than 30 feet thick. Slopes greater than 65%. Rock conditions fair to poor for tunneling. Adequate cover available with short GOOD POOR horizontal entries. Drainage good. Stony clay overburden less than 30 feet thick. Slopes greater than 65%. 826 __ 826 Rock conditions good to fair for tunneling. Long horizontal entries or vertical FAIR POOR shafts required to reach adequate cover. Drainage fair to good. Gravelly and stony clay overburden 0 to 10 feet thick. Slopes less than 65%. Rock conditions fair to poor for tunneling. Long horizontal entries or vertical POOR POOR shafts required to reach adequate cover. Drainage fair to good. Gravelly and stony clay overburden 1 to 10 feet thick. Slopes less than 65%. Rock conditions good to fair for tunneling. Vertical shafts or long horizontal POOR GOOD entries required to reach adequate cover. Clay soil overburden 10 to 50 feet thick with relatively few rock outcrops. Drainage good. Slopes less than 65%. 825 825 __. Rock conditions fair to poor for tunneling. Long horizontal entries or vertical 19 shafts required to reach adequate cover. Drainage fair to good. Clay soil POOR EXCELLENT overburden 10 to 80 feet thick with few rock outcrops and easily excavated. Slopes less than 65%. 27'30’ — [I a 27/30! No feasible means of tunneling to adequate cover. Soils difficult to excavate, ,’I N .I UNSUITABLE UNSUITABLE saturated, or periodically flooded. Low flat coastal lowlands, mangrove swamps, 18/ a“ ,, fresh-water marshes, and beaches. Locally suitable for small hasty fortifications. I/ r (I I] 5 Selected site or area where a tunnel-type installation with a minimum floor space of 60,000 square feet ,’ 0 could be excavated with only 100 to 300 feet of horizontal entry required to reach 100 feet of cover. / 824000m.NI __ (See accompanying table.) II! 824 X Location of existing Japanese World War II caves. [/1 , I II I I I I I ,« i9... 7'27'00’ “ 7'27’00” 151’47’00” 366 000m.E_ 47'30' 367 358 369 370 371 5000” 374 P 52/30” 376 °‘ 3779‘ 378 b ‘3 379 151‘54’30” 375 S “V856 Scale 1225,000 Edition Z-AMS (AFFE) I . . . . . 1 o lstatute Mile Interpretations for underground installation construction by Elmer D. U.S. ARMY MAP SERVICE, FAR EAST - 57-041 - R~15 - 3/59 .3.4c Prepared under the direction of the Engineer, Hq AFFE,"8A, by the U.S. Army Map Service, Far East. 1000 500 0 1000 2000 Meters Patterson, 1954'1955- Compiled in 1957 by photogrammetric (multiplex) methods. Coastal hydrography compiled from USHO i r——q 1—4 i——-i H H 3 Chart 6048, 1944. Horizontal and vertical control established by Corps of Engineers, 1951. Names trans- 1000 500 O 1000 2000 Yards literated in accordance with rules of the US. Board on Geographic Names. Major roads are classified by f H H l l H H reconnaissance by the 64th Engineer Battalion (Base Topographic), 1952; other roads are classified from 1 § 0 INauticaI Mile source maps and aerial photography and are not verified by reconnaissance. Coastal vegetation are clas- E ‘ ‘ ‘ ‘ ‘ COVERAGE DIAGRAM INDEX TO ADJOINING SHEETS sified by reconnaissance by Military Geology Branch, Intelligence Division, Office of the Engineer, Hq AFFE/BA, , with personnel of the U.S. Geological Survey, 1955. Map not field checked. CONTOUR INTERVAL I0 METERS Underground Installation compilation based on field observations 1954-1955 by Military Geology VERTICAL mm": MEAN SEA LEVEL 4544 " NW Branch, intelligence Division, Office of the Engineer, Hq, U.S. Army Japan with personnel of the MAP 48 U.S. Geological Survey. TRANSVERSE MERCATOR PROJECTION HORIZONTAL DATUM IS BASED ON THE ASTRONOMIC STATION No. 2 (I95!) isi°53'34.3' EAST or GREENWICH. 7°2I’37.7’ NORTH 4544 IIISW 4544 III SE 4544 II SW LEGEND HYDROGRAPHIC oATUM : APPROXIMATE LEVEL or LOWEST Low WATER MAP 44 MAP 46 MAP 49 ROADS . BLACK NUMBERED LINES INDICATE THE I_ooo METER UNIVERSAL TRANSVERSE All weather MERCATOR GRID, ZONE 56, INTERNATIONAL SPHEROID 4543 IV NW 4543 IV NE 4543 I NW hard surlace, two or more lines wide __‘, __ None Built-up area i i i.” "'5 “57 THREE ”'6'” 0F “‘5 cm” “'5‘” A“ ”"17“ . _ MAP 45 MAP 47 MAP 50 loose or Ii lit surface, two or more lanes Wide Mi, None Church; School; Cemetery Wiim .. 1.5 \\\\\\"‘.- . Ii a IE I d N .‘§§\\\\\\=T\‘\\\ ar su ace, one one m e m". one L' 'l to l’ ; s b d l I I lflll 0 anger In! I! merge ICC COMPILATION METHODS loose or light surface, one lane wide None Wreck: Sunken; Exposed WW 7 , Photo‘stereo Photo-plunimetrlc fair or dry weather, loose surface, two or more lanes Wide ———-— S lie oclis; Fo esh c this ,,,,, i 6“” 1°“ DESIGMT'O": TO GIVE A STANDARD REFERENCE 0N V - - ~ i I I I a u" n ' r 0' 56N THIS SHEET To NEAREST 100 METERS W 0 GLOSSARY h air or d weather, oose sur ace, one m in e Mi :;:::::: Rocks bare or a ash; Reel 7, W”... . ror an MC 0'33. ry w I II I looooo M. SQUARE IDENTIFICATION SAMPLE POINT. + SUNKEN ROCK A. USHO Chart 6048, 1944 (reliability good). Unun en not point Cart track, trill ._.w__-...._AAA .._._--__ Depth Curves and ln fathoms “ma Mm “mm“ 100.000 mm Aerial photography: Feb., July 1946. Si d d I d, in Ie i cli _...._ —f——0—f— ._ , , sou-rein which the point has: lP ll'l ar gauze rol lo: I: ll Reserve", Dam, on". ‘i, ,,......-_ .w, 7A 2. Locate flfil VERTICAL and line In LEFT of Standard gauge railroad, double track "W DOIl'll and read LARGE ligures labeling the . . 2’!” Slit CVIPOlliolS lemma..- -._._.___._____.__ LP line either In the top or bottom margin, or Narrow gauze mlroad, smzle track .‘ ,_ii I it APPROXIMATE NEAN DECLINATION l955 on the line itself: 76 , _ 3'" ron CENTER or SHEET [1' r f "I l 'dl l ’i: Narrow "“19 "m“! double °' multiple luck V-~> , Rice Paddy; Marsh .__.._.,__ll.A.__.__.._,.._ .S ANNUAL IAGNETIC CHANGE i' EASYERLV 3, L203: firsihosiri’z‘bniisi. ifiiifnz‘iiziow 4 , . . II I . . paint and road LARGE lgures label n in Power transmrssmn line no .i “N.--“ I :I. Uu diagram only In obtain mm! values. line either in the left olr right nllflfllfl, 0: Spot elevation in meters: Checked; Unchecked Mfg, " No X146 "'9‘; "any”! WWWWW W h WWW-W "" To deforming magnum: nor"- lino, cm "I. IGNORE "" SM‘LLER "3“” olany 0" the line itself: 28 . I , i "P" "I. .d f "I. W1 number; these m for human Estimate with: from grid line to point: 3 Will: ”we; CII" _“ _ _ §Zi§ CH: 9"" P°”' 0" nu“! 9' ° W the toll coardrnales. Us: ONLY the WI h I I 'II I Id b' i t; Tow" Woods; Stlub ___,,,__., '“77’ !_"T VIM "to "flu. 0' "I anal. bohvoon GRID [NIGER figures of the grid number; SAMPLE REFERENCE: LP764283 .9", ee 0 m‘ I m e 0 I“ “*’7 0 NORTH and MAGNETIC NORTH, al pfofhd on "1mg“: 3 000 If reporting beyond 18" in any direction, Principal navigation light ol lighthouse; Anchorage M * xii Tropical grass; Coconut grove #_____iw..c,l..i mm the dogr‘o neck a! oh. nadir .49. of the up. 24 P""‘G“° 1"" °"’i"“'°"v “3 56NLP754233 M OEN NW, CAROLI N E 'SLAN DS Military Geology of Truk islands TRUK ISLANDS CAROLINE ISLANDS 1.25,000 6° 7° MAP 49 Underground Installations 151°47/00r 365 47/30" 367 368 369 370 371 50/00! 52'30” 376 @377 373 151'54/30!‘ a -v, . , _, .aw , . Vt. ° I00! 7 27/001! i i I I I / ; V we m V ”W5 X «:W ”avid? e253,»? 7 27 ' 1’ GD ' cgfimee . . . I I ,, ‘ ‘4 f‘ more 4' A ‘ ' Sites Suitable for Tunnel-type Underground Installations f o : ‘élfvygfwfl‘i , E l l "’" . fire? ‘9 ' /e . ' _ ___________ 21 19 I > if ff 7 Site Rock Excavation Rock Disposal Overlying Underlying Access i' 13 i s 8 | l number type conditions characteristics of rock material material 1 ,1 o M 0 E A/ EL i ‘33 i - ‘ 7 8 6 _l/ Trachyte Very good Irregular frac- General construc— Soil up to Undivided Fair from i i 11 l . _. a“ “as“ . WI ‘ 823 23 ’ turing; weather- tion; road build- l0 feet thick lava east; other i i 53"“: M162 \Ke/ 52 ' . _. \Unun e‘n / ed surface very ing ways diffi- ‘i‘ l i ' d/\Nlilkylsel . l 31 l i 1 15 12 san / soft, 150 feet cult l 1.4 , 5/\\ I 62 coral o/x/ / 34 thick HI E / 2 \ l 23 \ i [,a- a. , \ : 29 [x 7 Andesite Fair; possi- Polygonal colum— General construc- Soil up to 30 Breccia Poor j“ 5i! ii] 23 i 19 g, '/ ble drainage nar jointing; tion; road build- feet thick over 10 feet 9/ >3: ‘3 UCLA ROAD ”aging—rv”, problems platy fracture; ing undivided lava thick Vgol ,1 (OROR EN NEPUNG) 21 (lee—e” 50 feet thick up to 100 feet twigfi 5; “’1; , coral /, thick L9 ; -j . \8 list; 1 . -' (fig 19 /’/ 31 822 _ 8 Basalt Very good Polygonal colum- General construc- Soil up to Not seen Excellent *f‘iwal . .g .. _ 4 5”." / / coral / ’ 822 her jointing; tion; road build— 30 feet thick \: . ~ . iyfchial \ 11 / platy fracture; ing; swamp fill .a—s J3\\ se' ~ . " ,~ 5. e14". .. of 15 9 7a] /’ 16| // \ '1 l / cora ,’ 160 feet thick tw" - lifiRpg Lag/5P7 11 0 I; \ 1 12 1f l 62 / // Sign r’/ - . . . / \ / // 9 AndeSite Probably Polygonal colum- General construc- Thin 5011 over Undiv1ded Very poor; ff‘x"\\ \fmd 31,“, she”: *‘ ‘ 19 / 1 good nar jointing; tion; road build- several lava lava no roads 1:37] 1‘ 72 41 , / 77 78 79 ‘53 some prisms in- ing flows and. steep ill: \ shell, 10:“ / ,/ clined to face; approach is? I. , \° // 150 feet thick .9: ‘l 32.. .‘r‘ ' . m t "’ - . . " 3&1? ain‘t-rum: »' / / lO Ande51te Probably Polygonal colum- General construc- 8011 up to Undivided Very poor; ”/27 . "to \‘fi‘k‘k m ‘ o -, *r l 23 821 - - . . . - 9,1555 .4 a; 1454.13 - " ' ”‘9‘: swim—ion ”-1- . . ’ s 821 - good nar Jointing, two, road build- 10 feet thick lava flows no roads and )7 55%»: 574:?! 1W5fifigfmgk“i‘ii¢VP‘-wl 'Vfifiw 8 //2 coral /, 160 feet thick ing steep 5E3iliéf€éz liggggrgr ,. J Eiggéfiémwré $3 .. cm ’/ // approach entity, - ' gr;;zv 522/? .‘ ' ‘3},fivsffimma ’ ’ “it. - 31% a}? ..:u . ll Andesite Very good Polygonal colum- General construc— [thin soil over Undivided Very good; ““ " g“ g: 31 : 30 mar jointing; tion; road build- undivided lava lava flows road to sand ' 70 feet thick ing; mix with flows 60 feet site talus thick 12 Basalt Probably Some polygonal General construc- Thin soil Undivided Very poor; 31 cozr7a| x/‘/ and good columnar joint- tion; road build— lava flows no roads and mm 820 breccia ing; 200 feet ing; easy disposal steep ,’ 13 :1: 820 25,00” thick in vicinity approach \15 g I/ 1} Sc I 25’00” \ / . 1, era 13 Breccia Probably Fragments up to Road building ,- Thin soil or Undivided Fair ROLEX/”FMOSET L5; 53"” \Q good 1+ feet diameter; fill; easy dis- none lava flows ” \\\o\ 200 feet thick posal in vicinity . , 15 \ A", > coral l/ See photo plates 3, 11 B, and 66 B ' ‘4“ / Coral ‘ 41 _V_l . ‘ i 24 'I 1‘ . , I $\\ ll royal 23 sand anid shells“ -’ {nun/[en .Neaiiwo I /l r ' 819 819 - K 33 \ coral SUITABILITY FOR UNDERGROUND INSTALLATIONS x MAP, TRUK ISLANDS Suitability terms, in order of decreasing suitability, are: excellent, good, fair, poor, and unsuitable. 29 32 Suitability for Unit Description Tunnel type Bunker type - Rock conditions good to fair for tunneling. Adequate cover available with short , i 20 34 22 8 818 _ l EXCELLENT UNSUITABLE horizontal entries. Drainage good. Stony overburden less than 30 feet thick. 31 28 18 ’sand 18 S'°Pes greater than 65% Sites Suitable for Tunnel—t e Under round Installations YP g Rock conditions fair to poor for tunneling. Adequate cover available with short Site Rock Excavation Rock Disposal Overlying Underlying Access GOOD POOR horizontal entries. Drainage good. Stony clay overburden less than 30 feet number type conditions characteristics of rock material material thick. Slopes greater than 65%. D U 5 L 0 IV / 5 A A N D l Undivided Very good Polygonal colum- Road building; Soil up to 30 Breccia Poor Rock conditions good to fair for tunneling. Long horizontal entries or vertical lavas, nar Jomtlng; mix with talus feet thick over 10 feet FAIR POOR shafts required to reach adequate cover. Drainage fair to good. Gravelly and mOStly 260 feet tthk undJ-Vlded lava thiCK stony clay overburden 0 to 10 feet thick. Slopes less than 65%. basalt flows 2&0 feet thick .. . . . . . 817 3 __ Rock conditions fair to poor for tunnellng. Long horizontal entries or vertical , . . - x I,» 17 POOR POOR shafts required to reach adequate cover. Drainage fair to good. Gravelly and 2 OliVJ-ne Very gOOd Polygonal COlum‘ Road building, 3011 1113.130 30 UndiVJ-ded Poor Q‘xvn stony clay overburden 1 to 10 feet thick. Slopes less than 65%. basalt naJ‘ jointing; mix with talus feet thick over lava flows , /\\ 30 feet thick undivided lava . . flows 130 feet Rock conditions good to fair for tunneling Vertical shafts or long horizontal thiCk POOR GOOD entries required to reach adequate cover. Clay soil overburden 10 to 50 feet thick with relatively few rock outcrops. Drainage good. Slopes less than 65%. . . 3 Undivided Not known 200 feet thick Road building No soil UndiVided Fair; old Rock conditions fair to poor for tunneling. Long horizontal entries or vertical séquence lava flows r?ad to 23 shafts required to reach adequate cover. Drainage fair to good. Clay soil With two Slte 4 POOR EXCELLENT overburden 10 to 80 feet thick with few rock outcrops and easily excavated. thiCk ba— ‘\ Slopes less than 65%. salt flows 2 816 _ . , , . . ' 1... 815 . . No feasible means of tunneling to adequate cover. Soils difficult to excavate, ll Basalt Probably good 50 feet thiCk Road metal; NO soils over UndiV'lded Very good ,4” 7, UNSUITABLE UNSUITABLE saturated, or periodically flooded. Low flat coastal lowlands, mangrove. swamps, dump in sea undivided lavas lava flows fresh-water marshes, and beaches. Locally swtable for small hasty fortlflcatlons. 110 feet thick 5 Selected site or area where a tunnel-type installation with a minimum floor space of 60,000 square feet 5 Basalt Probably good 50 feet thick Road metal; Soil up to 30 Undivided Excellent 0 could be excavated with only 100 to 300 feet of horizontal entry required to reach 100 feet of cover. swamp fill feet thick over lava flows (See accompanying table.) undivided lava I I 2230’ 22 30 X Location of existing Japanese World War II caves. flows 20 feet , thick ' . , NO 3', x i i \, ' , 20 k , ' 1 l I i / \/ I4 corn 7- d ,r com/v ;.. , 8 8150°0m-N ’ l ./ “ m" i 5 /iiT a oJ-ztil a my ti) 19 r ‘ ‘ 15 I l l 0/ 53 ' 1 I9 co( 2 / c\oral - ///{/, 2] 3 l 3 a; ‘ 14 K I 0 \V‘\ i i Z ”V’! 4 12 51 “~ ___ ‘1’!" _______ 53nd. 0‘ II ‘I \3 31 I? 51 ’- - ' ‘ 13 d \‘s coral “lieu “--_m¥3 “"5 ’R CD”! ”a ‘ U an on Noawachang ‘ " Coral ,o ‘ ' * 11 ‘~-___ “3,1,. L331 /’ 15 ETEN ANCHORAGE / ‘ 1 1 ac 0 .‘I6 Coral r-x 20 I” 115 .oelx 2 / ‘2 22 Walton: EN UN N. 16 2 ml, 11 fl' 3 ~ °°"' / 4] q Coral reel ’3 ,3 Corn $167.. _ 3 u : coral ,é’ sand 17 —°\ , / 7.2200, 5 4 .4'3- -' "~‘- gig F’ fl *1» 7 /5\ / / f .. . a , é) l\~// / 7.2200,, 151'47’00” 366000m.E. 47’30” 367 368 369 370 371 50’00” 373 374 355 52’30” 376 377 379 151°54’30” W855 5 Scale 125,000 Edition 2-AMS (AFFE) 1 i o ISfatute Mlle | t t t' f d d ’ t H t' t t' b El D U S ARMY MAP SERVICE FAR EAST 57041 R 15 - 3/59 3 40 n erpre a IOI'IS 01" un ergroun "IS a a Ion COI’IS I'UC IOI'I y mer . . . i ' ' - - - . . » - 1000 500 0 1000 2000 Meters Patterson, 19544955- Prepared under the direction of the Engineer, Hq AFFE/BA, by the U.S. Army Map Servtce, Far East. I H E H H H Compiled in 1957 by photogrammetric (multiplex) methods. Coastal hydrography compiled from USHO 1000 500 0 1000 2000 Yards Charts 6048, 6050, 1944. Horizontal and vertical control established by Corps of Engineers, 1951. Names CF ,_, ,__, ,__, E ,___ transliterated in accordance with rules of the U.S. Board on Geographic Names. Major roads are classi- 1 § 0 IN t' lM'I fied by reconnaissance by the 64th Engineer Battalion (Base Topographic), 1952 and reclassified from E a" tea 'e aerial photography dated 1955; other roads are classified from source maps and aerial photography and COVERAGE DIAGRAM lNDEX T0 ADJOINING SHEETS are not verified by reconnaissance. Coastal vegetation are classified by reconnaissance by Military Geology ‘ , .. ‘ . Branch, Intelligence Division, Office of the Engineer, Hq AFFE/SA. with personnel of the us. Geological CONTOUR INTERVAL l0 METERS \\\:“ \\\\§“§‘§§§§§k§ Survey, 1955. Map not field checked VERT'CAL DATUW MEAN SEA LEVEL $$§i§§§§§q§ 4544 ll NW . . . . . .. "s‘ ‘~\\\ Underground Installation compilation based on field observations 1954—1955 by Mllltary Geology \“§3%\\s\\ ~\~‘ Branch, Intelligence Division, Office of the Engineer, Hq, U. S. Army Japan with personnel of the TRANSVERSE MERCATOR PROJECTION \ \ \§§\\\;\\ \§S‘\Q\: MAP 48 U.S. Geological Survey. ‘ HORIZONTAL DATUM IS BASED ON THE ASTRONOMIC STATION N0. 2 (I95l ): 5 §\ \\ §§Q§4 151'53’3413' EAST or GREENWICH, 7'21/37.7' NORTH , ~ Rs“ LEGEND 3&1 4544 lllSW 4544 III SE 4544 Il SW . ~ V HYDROGRAPHIC DATUM- APPROXIMATE LEVEL OF LOWEST LOW WATER Efi MAP 44 MAP 46 MAP 49 ROADS : u‘ ' BLACK NUMBERED LINES INDICATE THE [,000 METER UNIVERSAL TRANSVERSE §:\\\§ All weather , M MERCATOR GRID, ZONE 56. INTERNATIONAL SPHEROID SEQ hard surface, two or more lanes wide — & BUlII-UD area W— 7%” THE “57 ”“5 ””175 °F THE GR”) "”“BERS “5 OMITTED ng 4543 IV NW 4543 IV NE 4543 I NW loose or light suilace, two or more lanes wide #2:: Church; School; Cemetery ___.__ a: 199an G" “3- ‘3” MAP 45 MAP 47 MAI:’I_§9l hard surface, one lane wide __ — Limit 0i danger line; Submerged real _ _ _ .- .. loose or light surface, one :ane wide _ -::——: Wreck. Sunken, Exposed 4:» 0.09, 4'45’ GRID ZONE DESIGNATION W G E Photo-stereo Photo-planimelric Map Fall or dry weather, loose sur ace, two or mute lanes wide I Sunken rocks; Foreshore flats _— + : IV A STANDARD REFERENCE on V . . , . . * ' 0R °R 55M THIS sum TO NEAREST 100 METERS \\\\\\\\\\\\\ .- ~ . I: GLOSSARY Fail or dry weather, loose sullace, one lane wide ======== Rocks bare 0i awash; Reel __ \ * 3 “is 5‘ “”5 100.000 M, SQUARE IDENTIFICATION SAMPLE polNT: I SCHOOL A USHO Ch rt 6048 19“ ( l‘ b'l't d) Nom en bay , , a .. . \f . a , re re try 300 . Oror on L u. C3” "3°“, "a" —e————— —————— Devil Curves and "1mm“ re H,“ mm, mm", mm, m, LP a. 03% Chart 6050, 1944 (reliability good). Um", m cm. ”in, Standard gauge railroad, single track _ —l——o—+—- Reservoir; Darn; Ditch a» 2.512::illslVfafi‘gAplfrr‘iii‘iisntin LE" 0' Aerial photography. Feb., July 1946. Standard gauge railroad, double track Y —H—+t— polnl and read LARGE figures labellngthe ‘ _ 2"" Salt , LP line either in the top or bottom margin, or Narrow gauge railroad, Single track - fi—‘—— APPROXIMATE MEAN DECLINATION 1955 on the line itself: 78 . . 1"" ron CENTER or SHEET Eshmltetenfhslmm and line to pomt: 1 ”3"" “”59 '“lmad- “WW °l “lump" "a“ , Rice Paddy; Marsh ~_____._— ANNUAL MAGNETlC CHANGE l' EASTERLV 3. Locate inst HORIIONTALyid Ilne mow . . , l . a dLARGEl Power transmlsswn line ,,,,,,,,, / . [—|- Use diagram only to obtain numerical values. , lizlemertlier'ei: the left DIIEVI:RII::lE:,‘:: Spot elevation in meters: Checked: Unchecked " us "IAS Nina; ° To de'e’mifle magnetic north line, conned the IGNORE "" SMALLER "3““ 9' W °" "‘°""°““"3 16 , 1 H ,, and number; those are for llndmg Estimate tenths from grid linelo point: 8 Wall; Levee; Cliff n" ———~% DD my” point P on the south edge °f ”'9 map the full coordinates, Use ONLY the Wt h I l .H L [d b ‘ ,3 Tom w°°d33 5"“ # with the value of lhe angle between GRID LARGER figures of the End number; SAMPLE REFERENCE: LP781168 . a 8'" 9° ° ”“ ' “a 9 ° 1“ k 0 NORTH and MAGNETIC NORTH, as ploffed on example: 8 000 "reporting beyond 18" iii any direction, Principal navigation light 01 lighthouse; Anchorage ‘ * xl/ Tropical grass; Coconut grove _ ___ DI: the degree scale oi the norffi edge of lhe map. g PM” ““0 1°"? D‘s'lmmm '51 56NLP781168 M OEN SW, CAROLI N E ISLAN DS 1958 TRUK ISLANDS CAROLI N E ISLANDS 1225,000 UMAN NW Military Geology of Truk Islands MAP 50 Underground Installations 151°47'oor 365 47'30” 367 368 369 370 371 50/00” 373 374 52130/r376 378 379 15i°54130r 7°22’OO” . . , 7°22’00” 5 ‘. o/ 33 \12 .3; . ~ 2"”??? 45 10 23 / 23 ml I / ; A15 / 17/ . \ ...m._mm 7 17 4&0/ / i \ J , ' \\ / 00R R EN wiry/yo ,4 W3 '. 3 ° CC’ ‘ Ti/ , j ., / ,3; 41;.‘;$:,_ . ‘ ,_E_7_‘§N ANCHORAGE . is . . m ' ' , 22 ----- e 814 Weaversd foot 2 g 9!; (’VT’T/ flfigéags‘ \ / 17 can 814 i ‘ r! ' . «i s . . .- . . (: £13) I gig , /’/§JN§%Vé§% mot ' .. l ‘ . r - i « , I avaafifi'i’g’fi‘e 9 udz‘rsrieei a?3::£«f§ .. 29 twa‘otéy-firfiazezza . , 17 cm. .Omaflangg"€v¢¢dfiwvwar I I zeaezgfiimtvzsa: / cor-I ‘ffiiwzfifrz‘r' r" / l'm‘zclrh 24 , flfloy/fé‘ / 151.4517" 17 “inert? 8 ‘ ' 19 813 13 60131 9 b 51% . . «13’ . . 15 _ :pfli ‘ I com o ’_ ,l'fff. '. ‘ , \ \/. mi _ / > 1 an. . . ,/ vi , r »»»»»»» , l . ' , . ‘ ’49)" {I/fiifg. Sites Suitable for Tunnel-t pe Under round Installations .‘ daily/a ‘ l 1 _ 'jzgjfi'éfég‘ ' Site Rock Excavation Rock Disposal Overlying Underlying Access 62 0 * ""45”,? . number t e conditions characteristics of I‘OCk material material an on Unr'kei Uncovers. 2 feet * J. 4 $3,}; YP ' _ '44", (wk 5 T E Al x- - ‘49 mania, _ . . . . g 812 . . . _.‘!‘—"e$,‘:‘2¢¢94’4'4 l Basalt Very good Some rock is Fill; dump in UndiVided Basalt Excellent - 12 es u b e r e —t e nder rou d st t ns “9‘! » “0&7, Slt S lta 1 f0 Tunn l yp U g n In alla lo §,é$f‘e\§‘:¢:£’/ where rock fractured and sea lavas 110 feet 8 feet ‘5}‘(1‘4’ ,0“ v. in - _ . . . Site Rock Excavation Rock Disposal Overlying Underlying Access ' Elf “k‘étégz‘itia‘q f5 2:12 d gga::::eghick Elli: gettlzfn tthk number type conditions characteristics of rock material material fifie‘ma‘ ra ure y. F E F A ll/ . {e395, 5011. " ‘W‘rfi‘ ' e ' Soi u to O n 'v‘ded xce ent 7 5 "We . . . l Basalt Good Widely spaced . Road to tal, l P‘ 3 U do. i E ll \ . . i‘ "n 2 Basalt Very good, Some rock is Fill; dump in Weathered Conglomer- Excellent vertical JOll’ltlng; dump in sea feet thick over lava flows ,v'n. to“ . . . . . ~ — but underlain fractured and sea breCCia 9O ate u to 65 feet thick undiVided lavas ‘ 4/ p 100 feet thick haufi'f‘i'l‘n by conglom- weathered; feet thick 5 feet - 1 l ,l- . . I 'rn erate 30 feet thick thick Iqfifi . 3 ”a; U M A N 2 - ‘ ' ’v'ded o . . 13 I’ . . . Basalt Good Polygonalcolum Read metal, SOll unto 3-0 Undl l P or -- nu' on Unum giiflf l Basalt Good Polygonal colum— Road metal; S011 up to 30 UndiVlded Excellent 8 5 mar JOinting; mix With talus feet thick over lava flows as . ,1_"\ My . . . . . _ 811 ll 7 6 f et th' k b lt 20 feet -. _____ ,, '5‘ - 1755’? nar JOlntlng,‘ dump in sea feet thick over lava flows K 5 e 1c 1:31:21: 2/ ,. gigs}, ,2; ‘ 50 feet thick undivided lavas 20,00” we 19 ‘ ii)? iii: In 95 feet thick 20,00” _ I A \ _ . . . . / i’r‘l’l’l . .. 3 Basalt GOOd Polygonal 001111“— Road metal, 8011 UP to 30 UnleldEd Poor 5, //fifi;’ffifl‘§$i§g§§ 2 l/ Basalt Good Polygonal colum— Road metal; Soil up to lO Breccia Poor . . . _ . . . .1. 4. was. _ ‘ g . . . nar JOlntlflg: le With talus feet Fthk OVGI‘ lava flows W‘al fl/,1§;z¢;?éa;f;§it / nar JOinting; mix With talus feet thick over up to lO 50 feet tthk unleldEd lavas 2 , ,.’9f,i{fi=};1i¢fiii.tu ‘i 65 feet thick undivided lavas feet thick 100 feet thick coral 62 ray, gfigafi'qrflm‘r r 20 feet thick 12 «(fl fillfi'éé‘22 i _ . . . a wig out GEE a I ll Basalt Good Polygonalcolum— Road metal; SOil upto 30 UndiVlded Poor 0 eyi fiii,"\€§'€“m I 3 Basalt Good 60 feet thick Road metal; Soil up to Basal con— Excellent nar JOinting; le With talus feet thick over lava flows 5é1¥0éw un en Fanmono I swamp fill 30 feet thick tact not 60 feet thick undiVided lavas 11 "l’k/rflgggfi" I seen 510 so feet thick 10 \// ”a . y 5... late 5 B - 810 .. .. .. $5; waagfifif I p . . . _ OROR EN KUKUWU In; my; . / r 5 Basalt Fair Polygonal colum- Road metal; SOil up to 30 UndiVided Very 12 $3, fifiljg‘i : T R U K / (II I S L A N D S . . . . . I II . l nar jOlnting; le With talus feet thick over lava flows poor if! 5.35:5???“ .n Unuf I / / total thickness undivided lavas 5: ‘fiéfifi‘fii I 15 // l/ 17 33 90 feet, main 30 feet thick 0 tweeter/1% 10 16 [7 /’ flow 60 feet fi“’¢‘"’m"’¢é‘ Lia, sand and shells/ // 55 «new» '5 r ,« T R U K L A G 0 0 N T 0M”?! w 30 6 Basalt Good 90 feet thick Road metal; No soil over Undivided Poor ,{I’w’efi’r’éfl’fl // ’/ / \“\~\\ . . . . I. ’ZéA‘V/fl" // 13 / 11 ’ r \s- mix With talus undiVided lavas lava flows 'y‘o'fiV/ih/ /,/ )0 / / ~\\\ .5; 20 feet thick éwb‘zéil, 12 / // / 17 \ ‘17 25 O > ‘i‘fi “ \ 809 — .ef’é'fle‘a 35 809 4 A a i 9 i figfif’o‘afi“ 5““ ,x I’Q‘t’r e rflfifioflddfie‘ Vegas? MAP, TRUK ISLANDS ' "’ ‘0” 28 Suitability terms, in order of decreasing suitability, are: excellent, good, fair, poor, and unsuitable. 12 Suitability for 12 ,/ l Descflpfion /’ i \\5\\ 21 ' Tunnelfype Bunker type / l 4 i 36 [lo/why 17 L, . / R0 IEN ARA GA 23 Rock conditions good to fair for tunneling. Adequate cover available with short I23 I, I41 \ 808 - EXCELLENT UNSUITABLE horizontal entries. Drainage good. Stony overburden less than 30 feet thick. , I \ \ 308 Slopes greater than 65%. l l \\ II II \\\ Rock conditions fair to poor for tunneling. Adequate cover available with short 377 15°53'30" 378 379 l5l°54’30” \\ GOOD POOR horizontal entries. Drainage good. Stony clay overburden less than 30 feet 7017'00” 7ol7loofl o \\ thick. Slopes greater than 65%. W/fldwfi ”Rik I \11 \\\ a flux ":43 Atkin Island 805 .l. ‘ Unuri o Nukanapwiil 0 . . , \ Rock conditions good to fair for tunneling. Long- horizontal entries or vertical 5 ’ l 1‘! ‘ FAIR POOR shafts required to reach adequate cover. Drainage fair to good. Gravelly and Wfifi stony clay overburden 0 to 10 feet thick. Slopes less than 65%. a"? ,{ , 2 n; . fri 1", . N . Rock conditions fair to poor for tunneling. Long horizontal entries or vertical . )9. )5!!- 8 807 - . [MW POOR POOR shafts required to reach adequate cover. Drainage fair to good. Gravelly and " ’45:} stony clay overburden 1 to 10 feet thick. Slopes less than 6500. law . . /§(" M... air - ’41? Rock conditions good to fair for tunneling. Vertical shafts or long horizontal “’4; I POOR GOOD entries required to reach adequate cover. Clay soil overburden 10 to 50 feet l f{ thick with relatively few rock outcrops. Drainage good. Slopes less than 65%. I‘ ’ -// I 804 804 ‘ .. Rock conditions fair to poor for tunneling. Long horizontal entries or vertical ; f shafls requued to reach adequate coven Dranage fah to good. Cay so“ / 17,30” _ 6- POOR EXCELLENT overburden 10 to 80 feet thick with few rock outcrops and easily excavated. Slopesless than 6500. 17’30” _ 3 8060mm“. No feasible means of tunneling to adequate cover. Soils difficult to excavate, 21 . 06 UNSUITABLE UNSUITABLE saturated, or periodically flooded. Low flat coastal lowlands, mangrove swamps, .. "M" IX fresh-water marshes, and beaches. Locally suitable for small hasty fortifications. IG’OO” — . . . l6’OO” 1 1" L F aneu Island \ / x A 2/” / l, 9 ‘ 3 ,r’ ‘ , i 5 Selected site or area where a tunnel-type installation with a minimum floor space of 60,000 square feet 7 Q I, é/gfl’oEN SAPOPI 3 gravel l/rid shells 0 could be excavated with only 100 to 300 feet of horizontal entry required to reach 100 feet of cover. \ , l/ 24 // (See accompanying table.) ”7/ / l, i L 1! 8030mm. N. 803 / /,’ o i 1 4 21 / X Location of existing Japanese World War II caves. 9‘ 00ml 5; f ' 17 7’ 22 7-17100, I I I I I °\ i II I {(4% / I / 7.17100), 151'47’00” 3660mm.E_ 47'30” 367 368 369 370 371 50’00” 377000m. E. |5i053rgon 5.054130” 52130” 376 378 379 151°54'30” W856 5 Scale 1:25,000 Edition 2-AMS (AF FE) .L _ i 2 o IStatute Mile Interpretations for underground installation construction by Elmer D. U.S. ARMY MAP SERVICE. FAR EAST . 57-041 - R~15 -3159- 3.40 Prepared under the direction of the Engineer, Hq AFFE/SA, by the U.S. Army Map Service, Far East. 1000 500 0 1000 2000 Meters Patterson: 1954‘1955- Compiled in 1957 by photogrammetric (multiplex) methods. Coastal hydrography compiled from USHO l H H k—1 i—-‘1 l—-‘ 5 Charts 6048, 6050. 1944. Horizontal and Vertical control established by Corps of Engineers, 1951. Names 1000 500 0 1000 2000 Yards transliterated in accordance with rules of the U.S. Board on Geographic Names. Major roads are classi- [ H H H m E fied by reconnaissance by the 64th Engineer Battalion (Base Topographic), 1952 and reclassified from 1 o INautlcalMile aerial photography dated 1955; other roads are classified from source maps and aerial photography and ‘ COVERAGE DIAGRAM INDEX TO ADJOINING SHEETS are not verified by reconnaissance. Coastal vegetation are classified by reconnaissance by Military Geology granch. lilégllslgergfe Division, Office of the Engineer, Hq AFFE/8A, with personnel of the us. Geological CONTOUR INTERVAL IO METERS WITH SUPPLEMENTARY CONTOURS AT 5 METER INTERVALS ““‘wW \\3 rve , . ' u y 3” "°t he'd CheCked' VERTICAL DATUM: MEAN SEA LEVEL ’9“ ‘ 4544 ii Nw Underground installation compilation based on field observations 1954-1955 by Military Geology \ MAP 48 Branch, Intelligence Division. Office of the Engineer, Hq, U.S. Army Japan with personnel of the TRANSVERSE MERCATOR PROJECTION ' ”‘3 Ge°'°g'°a' suwey' HORIZONTAL oATUH is BASED ON THE ASTRONOMIC STATION No. 2 (i95i) 15l'53’34,3” EAST OF GREENWICH. 7'2l’37.7” NORTH LEGEND ‘ 4544IISW 4544IH SE 4544IISW HYDROGRAPHIC DATUH: APPROXIMATE LEVEL or LOWEST Low WATER MAP 44 MAP 46 MAP 49 ROADS All Neither BLACK NUMBERED LINES INDICATE THE 1.000 METER UNIVERSAL TRANSVERSE , .dh NERCATon GRID. ZONE 56, INTERNATIONAL SPHEROID ‘ hard surface. trio oi more lanes wide & Bum-up ml ——» 'JTIW' cu m: LAST THREE DIGlTs or THE Gain NUMBERS ARE oHirrEn 4543 IV NW 4543 N NE 4543 I NW loose or light surlace, two or more lanes wide u—‘flé'. Church; School; Cemetery id’ {99”} MAP 45 MAP 4'7 “AF—f0 hard surface, one lane wide l — Limit ol danger line; Submerged reel . ii '1} ’ loose or light surlace, one lane wide w ___________ m Wreck: Sunken; Exposed 4°45! COMPILATI_ON METHODS ‘ 0-0,; on Photo-stereo Photo-planimetric Map GLOSSARY Fair or dry weather, loose surface, two or more lanes rude Sunken rocks Foreshore llats GRID zoni DESIGNATION: To GIVE A STANDARD REFERENCE 0N f . d m I , I . I 3 :7” “ "”5 nus SHEET TO NEAREST ioo iimris m . I: Oror “1 hang: a" or ry m er, oase surace, one one ride WW :::::::: Rocks bare or "rash; Reel mono M.SQUAIE IDENTIFICATION SAMPLE POINT: i CHURCH A, USHO Chart 6048 1944 (reliability good) Unun en cape, point Critli'i‘l, " J' ‘ ’ ... ' a rat, III N __-___ Depth Cums and in Fathom: “ma [mm Momma" 100,000 mm B. USHO Chart 6050, 1944 (reliability good). Stundard gauze railroad, single tuck _ _ —o—+—-+—- lle ivoir- Dam' D'lcli @ aquarein whichlha pomtliu: LP Aerial DhOIOEI’aDhVI F81)” July 1945. ' $9 . i l w—-—— 2.LocatclirstV£RTlCAL (ridlinelo LEFT of Standard gauze railroad, double tuck —ii-—»—ii— “a n pcintand ma LARGE iigures llbelirutho , _ 1"” Salt evaporator: “will!!! LP 1‘ . Narrow gauge railroad, Single track 1"” h z...“ "Hahn“ “A" DECLINHION I955 ol::y:t::l’.llr.lsi::'llop or bottom mll‘llfl, or 71 . . _ — ron CENTER or SHEET Ei‘ r t th 1 ‘dl r i: 3 Narrow gauge "'"Md' double 0' multiple track _____ , RIC! Plddy; Marsh “ h “e - ANNUAL HAanic CHANGE il EASTERLV 3. L23: lirainllosm'lgiill'xl. :ddlfnzoézLow Power transmission line l _ ___,____./’ F “- . . , point Ind and LARGE 1‘. es Iabaingiho . . __ U” “9"” only '° °b""" mm! ""W‘- lino either in the left o'r |Iiglit mnrlgin, or Spot elevation in meters: Checked; Unchecked __.__ x as x,“ "'9" - “" To dolor-mine magmric norm lino, conned rho IGNORE "'- SMALLERIirum of my on tholincilnll: 12 . . u,, d b ;m 1 I'd ' ' '; Will; Levee; Cliff ______ __W A WM‘ 5 I! ':l prvof porrif P on Ibo south dye of the mg: ‘1': ISIIHZi-izidiiu: Iii; igmic m: [slim-in tenths from grid Iinnlo point 2 Watemheel 0' mill Located mm 13 Olower s, cm with rh. Volvo of Mn angll bow-or- GRID :filzfillzlligum £6,558; number; SAMPLE REFERENCE: ”3713122 ' T“; NORTH and MAGNETIC NORTH, as plan-d on ' ll reporting beyond II' in my dinctiori, W. .. DD _. - "new: Mitigation lig l o IKMIIOIISC, Anchorue _ * xix Tropical grass, Coconut grim rhodogru scale or in. nor-"i Ing of the map. PM” 0"“ 1”" D”"""'°"' “ 56NLP713122 U MAN NW, CAROLI N E ISLANDS 1958