238 



HEEZEN AND MENARD 



[chap. 12 



Fig. 7. Preliminary chart of Hudson submarine canyon. (After Heezen et al., 1959.) 



sediments and sedimentary rocks lies at the base of the continental slope off 

 New England (Fig. 8). Thus the main difference in morj)hology in many places 

 between the trenchless continental margins and those with a marginal trench 

 appears to be that, in the former, the trench has been filled with sediments. 

 Elsewhere, as in the Gulf of Alaska, a buried marginal trench has not yet been 

 revealed by seismic stations. 



In the continental margins of the Atlantic, Indian, Arctic and Antarctic 

 Oceans, and the Mediterranean Sea, the continental rise generally represents 

 the Category III provinces. The Pacific, however, is bounded by an almost 

 continuous line of marginal trenches. The high seismicity, vulcanism and 



