University of California. 



[Vol. 2. 



doubt due to terracing. San Nicolas must have been at one time 

 higher than at present, the island having been completely cut 

 away at one stage in the coastal uplift. The same thing is now, 

 again, taking place; for, judging from the submarine shelf on the 

 northern side, the greater part of the island has been cut away in 

 recent geological times, and were the present rate of cutting to 

 continue, it would not be long before the whole of the island, with 

 its records of earlier terracing, would be planed off. (Cortes, 

 Tanner, and Osborn Banks are examples of islands whose tops 

 have been wholly removed during the recent stages of wave- 

 cutting. They will be treated more fully later, under the head of 

 submarine features.) The small number of well-developed terraces 

 found on San Nicolas as compared with the number on San 

 Clemente may be accounted for by rapid cutting in the soft rocks 

 forming this island, the cliffs on the terraced side having been cut 

 back so rapidly that many of the previously-formed terraces were 

 wholly obliterated. 



The drainage of San Nicolas is much like that of San Clemente. 

 Numerous steep-graded channels score the shorter slope of the 

 island, tending to the formation of cirques ; while few, long, narrow 

 and apparently shallow troughs characterize the northern slopes. 

 There are a few indentations on the northern coast, but it is 

 probable that none of them represent drowned valleys of the 

 present cycle of erosion. 



That the island is a faulted block needs little more proof than 

 its form, which is as definitely that of a tilted crust-block as is that 

 of San Clemente. Below sea-level the contrast between the two 

 slopes is even greater than in the case of San Clemente. 



The topography of the island has been called young. This 

 conclusion is based not only on the character of the chiseling due 

 to subaerial erosion, but also on the apparently slight modification 

 of the fault scarp, — a striking feature, in view of the fact that the 

 island is composed of soft sandstone, and faces the open ocean, and, 

 therefore, the direction of greatest waves. The abruptness of the 

 fault scarp can not be due wholly to rapid wave-cutting, for the 

 submarine contours show only a comparatively small amount of 

 wave-cutting on this side of the island, and the high angle is 



