Smith.] 



Islands of Southern California. 



215 



flounced terrace, and that submarine. Further, in the case of San 

 Nicolas, no pronounced terraces have been developed on the steep 

 southern face, notwithstanding the softness of its rocks. 



Thus marine abrasion in the softer rocks, where the subaerial 

 topography is generally mature, is more rapid, not only on account 

 of the greater resistance of the harder rocks, but also on account of 

 the gentler slopes which characterize the softer areas. Further, 

 given a submergence of both harder and softer areas, the terraces 

 formed on the latter are more nearly continuous (or sooner become 

 so), and therefore more evident to the eye, than those formed on 

 the surfaces of the harder rocks, since the general subaerial dissec- 

 tion is less pronounced in the softer than in the harder areas. If a 

 deeply dissected area of resistant rocks, characterized by steep 

 slopes and V-shaped canyons, is submerged, the terracing will 

 occur at first mainly along the submerged divides, which now form 

 the salients of the coast line. This notching of the crests can 

 never form so marked a feature as continuous terracing even of the 

 same development in other respects, and where such broken ter- 

 races are worn down by erosion their recognition is sometimes 

 very difficult. This will account, in part at least, for the doubtful 

 character of the notching near the southeastern end of Santa 

 Catalina (see page 190). If, in such a case as that just referred to, 

 the ocean remained for a sufficient length of time at one level, the 

 salients would, of course, be cut back, so as to give a more or less 

 continuous terrace. 



Cutting is most rapid, other things being equal, where the 

 material composing the sea cliffs is most nearly in the condition for 

 transportation, or is most readily brought into that condition, as in 

 the case of a friable sandstone, or a loose-textured rock of any sort. 



Rapid removal of the material cut away by wave action is essen- 

 tial to further rapid and continuous cutting, the most favorable con- 

 dition being that in which the material is disposed of by currents 

 as rapidly as it is furnished by the waves. It would therefore 

 follow that wherever rapid cutting is taking place, there is also 

 rapid removal of the eroded material. The finer the particles 

 transported by littoral or other currents, or the more powerful the 

 currents, other things being equal, the more widespread will be the 



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