13 exposed. lateral growth is promoted. Erosion of the coral and cementatior of the resulting sediments also affect the formation and geology of thi atoll. Enewetak Atoll has been forming for at least 43 million years resulting in a 4.500-foot stratification of reef-derived carbonate deposils. Several drilling programs have been conducted to determine the subsurface composition and deposition of Enewetak Atoll. The Atomi Energy Commission (AEC) and Los Alamos Scientific Laboratory drillec 33 holes less than 200 feet deep during 1950-51. The U.S. Geologica Survey (USGS) drilled three deep holes, two to the basalt (volcanic rock base), during 1951-52.6 An additional 174 shallow core holes were drilled in support of Defense Nuclear Agency (DNA) programs’ to understanc the near subsurface geology (less than 300-foot depth) of the atoll in 1972. 73. Based on results of the USGS and DNA drilling programs, the subsurface geology of the atoll is found to be both laterally and vertically ; variable. In general, the ocean-side reef consists of well cementec limestone, whereas the backreef and lagoon sediments consist oi ( uncemented coralline sands and gravels derived from the ocean ree! organisms and the many patch and pinnacle reefs in the lagoon. Holes . drilled near the ocean reef edge penetrated predominately moderate tc - well cemented sediments, whereas holes near the lagoon penetratec : predominately uncemented to poorly cemented sediments. Thi: ‘ correlation between surface and subsurface distribution of rock types i: indicative of little lateral shifting of the reef and associated depositec | environment during the past few million years. A generalized geologic profile beneath the islands is as follows unconsolidated coralline sands and gravels between the island surface and the intertidal zone; within the intertidal zone, a layer of well cemented coralline beachrock from a few inches to 8 to IO feet thick is found. Recent coralline sands andgravels exist between the beachrock and 45-foot depth, whereas an alternating sequence of cemented and uncemented coralline sands and gravels exist to 600 feet.8 Between 600 and 1,000 feet the sediments again are composed of uncementedcoralline sands and gravels, and between 1,000 and 1,200 feet cemented coralline sands and gravels are encountered. Beneath 1,200 feet and to the top of the basalt, the sediments are predominately uncemented coralline sands and gravels with occasiona’ cemented layers. CLIMATE EnewetakePete is of the tropical marine type with temperatures tanging from 7I°F to 94°F and humidity in the 73 to 80 percent range. Cee Ratacts ATTos asi + Description and History: 1526-1972