8 THE OCEAN FLOOR 



majority have summits a few hundred feet below the 

 surface but carry above it white diadems of living coral. 

 They are the lovely atolls of the South Seas. 



In the northern part of the Pacific Ocean we find the 

 vastest lowlands of the earth's crust, with enormous 

 areas lying at depths of more than 15,000 feet. It is a 



Fig. 3. The Antarctic bottom current in the Atlantic 



