5. Recent Developments 

 in the Investigation of the 

 Deep Ocean Floor 



kjince the conclusion of the Swedish Deep-Sea Expedi- 

 tion, considerable progress has been made in investi- 

 gating the ocean floor by seismic and other methods. A 

 brief summary of these investigations, insofar as they 

 have been pubhshed, is given in this chapter. 



As stated above, the method generally used in the 

 seismic investigations has been that of refraction shoot- 

 ing, in which sound waves from depth charges exploding 

 at distances of several miles from the ship are recorded 

 by means of hydrophones suspended near the water 

 surface. This method affords an advantage over the 

 reflection method by revealing not only the thickness 

 of the unconsolidated sediment carpet but also the 

 velocity of sound waves through the underlying sub- 

 stratum. 



The results of recent investigations in the Pacific 

 Ocean by British and American expeditions have in 

 general confirmed earlier results from the "Albatross" 

 concerning thickness of the sediment carpet, namely 



G9 



