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University of California. 



[Vol. 2. 



platform on gentle slopes may be accounted for by considering the 

 submarine slope as simply a continuation of the subaerial slope, 

 since a low grade would normally give a greater distance from the 

 shore line to a given contour than would a higher grade. But it 

 must be remembered that this platform has in no case (except 

 where deposition appears to be the controlling factor in its forma- 

 tion) the character of a mere continuation of the subaerial slope; it 

 has everywhere the bench or terrace form. This taken in connec- 

 tion with the fact (which will be shown later)..that wave cutting is 

 greater on gentle slopes than on steep ones (as the terraces bear 

 witness), and the close correspondence of the platform's develop- 

 ment with that of the terraces, would go far to establish the origin 

 of the platform through wave action. 



The platform* as developed about San Pedro Hill is widest off 

 the western and southeastern salients, above which are found the 

 broadest and best developed elevated terraces. In the case of 

 Santa Catalina Island, the platform is wider on the side facing the 

 open ocean than on the landward side (the average width on the 

 landward side being a little over a mile, on the ocean side, nearly 

 two miles). It is, on the whole, wider in the igneous rocks than in 

 the harder quartzites; and it is widest of all on the salients. At 

 the north western end of the island the platform has a width of two 

 and a half miles; at the southeastern end, a width of about four 

 miles; and at the salient south of the Little Harbor region, a width 

 of somewhat more than four miles. 



Along the southwestern face of San Clemente Island, the plat- 

 form has an average width of three miles, while on the northeastern 

 side of the island the average width is about half a mile. The best 

 development of the platform on this side is found near the northern 

 end of the island, where folding in place of faulting has given rise 

 to somewhat gentler slopes. Along that part of the northeastern 

 coast where the fault scarp is most abrupt, the submarine platform 

 is inconspicuous. It reaches its greatest width, for this island, off 

 the salients at either extremity of the island, the maximum being 



*In what follows the width of the submarine platform is estimated from 

 the shore line to the 600-foot submarine contour, since the position of this 

 contour varies but little from that of the outer edge of the platform. 



