echo-sounders. He added that the pits and mounds of the 

 microrelief areas are in places 6 ft (18+ meters) from 

 bottom of depression to top of rise, but usually only 6 to 

 30 ft (1.8 to 9. 1 meters). 



The author of this report has defined microrelief 3 

 as the very small surficial topographic features that are 

 superimposed on both major and intermediate relief and 

 are distinguishable by examination of bottom photographs 

 (fig. 1). Vertical heights are measured in centimeters 

 and meters, and lengths in meters and occasionally tens 

 of meters. Major underwater relief, at the other extreme, 

 encompasses the larger earth features such as deep trenches, 

 high plateaus, rises, and mountain ranges. Intermediate 

 relief consists of the smaller underwater topographic fea- 

 tures such as low hills, valleys, banks, small basins, 

 gullies, and island slopes that may be parts of major fea- 

 tures, but are still too large to be photographed in their 

 entirety with present-day underwater cameras. Micro- 

 relief, as defined by the author, covers 100 percent of the 

 sea floor, whereas intermediate and major relief features 

 are localized and discontinuous. 



11 



