—— ae 
iin FORCE 
a 
Pat 
Figure 55. Soil cutter and pump undergoing preliminary testing at NCEL, 
working in a hole filled with water in hard, rocky soil. 
CASING THROUGH SEDIMENTS 
Over a major part of the deep ocean's bottom, the basement and 
sedimentary rocks of the earth's crust are overlain by layers of sediments 
to various depths. This is so because (1) currents carrying heavy media 
eventually deposit it in the depths, and (2) materials coming to rest on the 
ocean's surface such as dust, nonorganic debris from marine life, and volcanic 
ash would fall vertically through the water, in the absence of strong currents. 
Even with strong currents particulate matter would be rather uniformly dis- 
tributed, except near shore. Such heavy materials are represented by mud 
slides and sand falls, especially near shore. In the Pacific, recent theories of 
floor spreading are well correlated with known rates of sedimentation. The 
deep western Pacific, the point of submergence of the crust below Asia, has 
very heavy layers of sediment; this agrees well with the spreading rate. The 
eastern Pacific, or ‘new floor’ has a relatively thin layer. Only on steep 
slopes or summits of seamounts can exposed rock be expected with any 
certainty. 
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