by water, the sediment-water interface is probably firm 

 and sharply defined most of the time. The presence of 

 coarse sand, gravel, pebbles, and boulders, of course, 

 denotes a very hard bottom, capable of sustaining heavy 

 underwater loads. Such bottom materials are usually 

 easily determinable by photographic sampling. The fresh- 

 ness of the upper surfaces of manganese nodules, capping 

 of sediment, banking of sediment, etc., give clues to the 

 rate of sediment accumulation. Changes in bottom materials, 

 outcrops, and chemical deposits can be studied photographi- 

 cally by tracing sediment boundary lines. 



Repetition of patterns of sea floor features assists 

 in extending the results of photo interpretation to other 

 areas. Photographs can be compared on a geographic 

 basis, by targets, by animal populations, or by micro- 

 relief types. 



DISCUSSION OF THE ORIGIN AND 

 OCCURRENCE OF MICRORELIEF 



General 



The sea floor can be described as a huge jigsaw 

 puzzle. Much remains to be done before all the pieces of 

 information concerning the individual phenomena that con- 

 tribute to the formation of the microrelief can be fitted 

 into a single, overall pattern. Nevertheless, some general 

 statements can be made with respect to the origin, distri- 

 bution, and relationships of the microstructures. 



Thus, examination of surfaces and smaller related 

 parts of larger underwater features has shown that the 

 same kind of environment may extend for great distances. 

 For example, Mero 16 states that sea floor sediments tend 

 to be rather uniform over large regions and that a few 

 chemical analyses of nodules can be averaged to give fairly 

 reliable results. Averages of heights for visible targets 

 distinguished in the photographic study described in this 

 report are shown in figure 7. A specific area of the 



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