THE NAVY OCEAN SCIENCE PROGRAM 29 



program. These characteristics aiFect the transmission of sound 

 and the magnetic and gravitational fields of the earth. Thus 

 they influence sonar-system design, undersea warfgire, and the 

 operation of deep submersibles. Other properties of the sea floor 

 also affect the design, installation, and maintenance of under- 

 water engineering structures and influence rescue, salvage, and 

 man-in-the-sea operations. Knowledge and interpretation of 

 sea-floor topography are a major accomplishment and are dis- 

 cussed more fully in the section titled "Major Accomplishments." 



Geophysical investigations at sea are being conducted over 

 a variety of structural types in many geographic areas to deter- 

 mine sediment distributions, thicknesses, and acoustical and 

 other physical properties. These t5T)es include mountains, 

 trenches, abyssal plains, long escarpments, sea mounts, and 

 continental rises, slopes, and shelves. Structures and thick- 

 nesses of the sediments are determined principally by seismic 

 reflection methods. Seismic profilers, including energy soiu-ces 

 such as the electrical "sparker" or the more recent pneumatic 

 "air gun," are used. Low-frequency echo sounders are also being 

 used successfully to determine the structures of the upper 

 sediments. 



Since sediment thicknesses considerably affect the performance 

 of sonar systems, the thicknesses have commonly been measured 

 down to the underlying crustal rocks. The measurements also 

 provide knowledge of the sediment structures, deformation, 

 geological history and, to a lesser extent, composition and rates 

 of sedimentation and erosion. Valid interpretations are now 

 beginning to be made on the worldwide distributions of these 

 sedimentary layers. Until 1965 emphasis had been on the de- 

 lineation of structure, but in the past two years there has been 

 growing emphasis on the measurement of energetics so necessary 

 to sonar design £ind potentially useful in geological interpreta- 

 tion. 



Cores and dredge samples are collected as data for the de- 

 liberate study of specific geological provinces. They are returned 

 to the laboratory for detailed measurements of physical and 

 chemical properties, as well as to determine deposition rates 



