MAJOR ACCOMPUSHMENTS 73 



PHYSIOGRAPHY 



In the past 20 years, precise echo sounders have been developed 

 and used in all major ocean areas to provide data so extensive 

 that all of the major topographic features of the sea floor are 

 known and charted. The ocean-science contribution to this effort 

 has been the development of precise echo sounders, the record- 

 ing of a significant fraction of the data at sea, and the geological 

 interpretation of the soundings in the form of physiographic 

 diagrams. The physiographic diagrams are used in all forms of 

 oceanographic investigations and truly provide a new dimension 

 to oceanography. Because the sea includes such extensive areas, 

 these charts and diagrams are as yet inadequate in detail. Many 

 more measurements are required, as well as improvements in 

 instrumentation, before the physiography of the ocean bottom 

 is known adequately for Navy purposes. 



The charts and diagrams are most valuable in submarine 

 activities and underwater sound propagation. Particularly, 

 the roughness and slope of the bottom topography affect sound 

 transmission. Best transmission conditions occur in the flat 

 abyssal plains. Hence, a significant accomplishment has been 

 the determination that abyssal plains are flat and that they are 

 extensive. 



Slopes on continental rises (seaward side of the continental 

 slope) have been found to be quite small. These factors are of 

 importance in ASW. A knowledge of the irregular topography 

 in mountainous areas, which is still very inadequate, and the 

 shape of the continental slope, play important roles in submarine 

 operations, sound propagation, salvage operations, and building 

 engineering structures. 



SEDIMENT AND CRUSTAL STRUCTURE 



Marine geophysical programs supported by the Navy for the 

 last two decades have produced a revolution in geophysics, while 

 also providing a firm base for understanding and developing 

 sonar and many aspects of deep-sea technology. These programs 



