248 



HEEZEN AND MENARD 



[chap. 12 



graphy of the Southern California continental l)or(lerland. The Blake Plateau 

 apparently consists of many basins tilled to overflowing. 



f. Continental rise 



The topography of the continental rise (continental apron), which lies at the 

 base of the continental slope, is generally smooth (Fig. 14). Although minor 

 irregularities are not uncommon, these irregularities are rarely more than 



GULF OF MEXICO 

 Physioqrophic Provinces 



96 95 94 93 



90 



89 88 87 66 



85 e-i 



83 



82 81 



80 



Fig. 15. Physiographic provinces of the Gulf of Mexico, showing the prominent Mississippi 

 Cone. The Mississippi Cone dominates the floor of the Gulf of Mexico and turbidity 

 currents traversing this cone have built the Sigsbee Abyssal Plain. (After Ewing, 

 Ericson and Heezen, 1958.) 



10 fm in anij)litude. Occasionally, the continental rise is punctuated by 

 numbers of rather large seamounts often linear in pattern (e.g. off the eastern 

 coast of Brazil, the northwest coast of Africa, the northeast coast of the 

 United States, Peiii, the west coast of Central America, the coast of Baja 

 California and the Gulf of Alaska). The continental rise may often be divided 

 into two parts : the upper continental rise and the lower continental rise. A 

 typical example is shown in Fig. 5. Although in several areas, notably central 



