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University of California, 



[Vol. 2. 



the steep faces of these islands. At the present sea-level a terrace 

 of greater or less extent has been developed (see fig. 4) on the 



Figure 4. — Subaerial and submarine slope on the northern side of San Clemente Island, where 

 the submarine platform is least developed. 



steeper sides of both islands. Further, in the case of San Clemente, 

 elevated terraces are found on the steeper side, toward the north- 

 western end of the island, where the slopes are somewhat gentler. 



Other things being equal, cliff erosion is more rapid in soft than 

 in hard rocks. The more resistant character of the harder rocks 

 will be somewhat offset by the greater hardness of the cutting tools 

 furnished by its disintegration. But the beach material at any 

 given point may be composed to a greater or less extent of drift 

 from other parts of the coast, in addition to the material of its own 

 cliff. This would render the influence of the difference in cutting 

 tools more or less uncertain. The differences resulting from differ- 

 ence in the character of the rocks are seen in the cases of San 

 Clemente and San Nicolas, where the conditions are somewhat 

 similar, except that the gentle slope of San Nicolas faces the land, 

 while that of San Clemente faces the ocean. The submarine plat- 

 form of San Clemente, though broad, is much less so than that of 

 San Nicolas. 



That a moderate slope, with its consequent low cliffs, and there- 

 fore more rapid cutting, is of more importance (up to a certain limit) 

 than the character of the material eroded, is seen by comparing 

 Santa Catalina and San Clemente Islands, both of which are com- 

 posed largely of hard rocks. San Clemente, with its gentle slope 

 on the southern side, is terraced in a remarkable degree, while 

 Santa Catalina, with its high, sheer cliffs, shows only one pro- 



2000 ft 



