CORE SAMPLES OF THE OCEAN BOTTOM 



By Charles Snowden Piggot 

 Geophysical Laboratory, Carnegie Institution of Washington 



[With 6 plates] 



If one examines a map of the world, or a globe, the most noticeable 

 feature is the preponderance of water to land. In fact, the ocean 

 occupies 72 percent of the surface of the earth — nearly three-quar- 

 ters — and very little is known of it by comparison with our knowledge 

 of the land. Geologists and others have studied the land and what 

 lives on it so thorouglily that we now have reliable knowledge of its 

 history, and the many changes that have taken place, both in the 

 land itself and the plants and animals that lived on it, throughout 

 many millions of years. These studies have been of great value both 

 theoretically and practically and they are being continued with in- 

 creased application. But all this time nearly three-quarters of the 

 earth's surface has remained almost unknown and unstudied, because 

 it lies below great depths of water. At one place the water is 6 

 miles deep. Here the bottom lies below us deeper in the sea than 

 Mount Everest rises above us into the sky. Though much of what 

 is now dry land was once below the surface of the ocean, it appears 

 that the water covering it was never very deep. Though the sedi- 

 ments themselves might be many thousands of feet thick they were 

 deposited layer on layer in shallow seas. Apparently, much of the 

 bottom of the ocean has always been ocean bottom, and during aU 

 those millions of years that the ocean has existed there it has been 

 accumulating the sediments dropped upon it from the waters above. 

 These sediments, lying layer upon layer in the bottom, have become 

 the repository of the historical record of the ocean. The record of 

 what happened in the water above is filed away in the mud and clay 

 and ooze below. The rocks and pebbles and sand brought by ice, 

 the clay and mud brought by rivers and ocean currents, the skeletons 

 of marine organisms which lived and died and evolved into various 

 forms throughout the ages constitute this record. Some types of 

 these organisms live only in cold water, others in warm water, some 

 live in shallow lagoons, others in the depths of the open sea. Some 

 prefer fresh water while others survive only in salty water. Some 

 lived a long time ago, and others have evolved into their present 



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