SECT. 2] 



ABYSSAL PLAINS 



315 



2. Regional Description 



A. Western North Atlantic 



The abyssal plains of the northwest Atlantic have been crossed dozens of 

 times by ships employing precision depth recorders (see Fig. 3, Chapter 12, p. 

 235). Most of this work has been accomplished by the Lamont Geological 

 Observatory's Research Vessel Vema. 



Fig. 3. Bathymeti'ic chart of the Sohm Abyssal Plain. (After Heezen, Ewing and Ericson, 

 1955.) 



a 



Sohm Abyssal Plain 



The best studied abyssal plain is the Sohm Abyssal Plain south of Newfound- 

 land (Heezen et at., 1955, 1959). The plain is T-shaped and generally about 

 200 mi wide (Fig. 3) ; the depth increases in each arm of the T toward the stem 

 where the slope changes to south. The greatest depth (3181 fm corrected) is 

 found at the south boundary of the plain, near 29°N (Fig. 4). In the northern 

 part of the plain, small topographic irregularities are unknown ; but toward the 

 south, peaks 50 to 500 fm high increase in number until they finally replace the 

 plain (Fig. 5). North of the Bermuda Rise the plain surrounds a line of huge 



