Smith.] 



Islands of Southern California. 



205 



the past variable structures, changing with the strength and char- 

 acter of the currents in and about the channel, and with the amount 

 of detritus transported by them. The eastern end of the channel 

 is opposite the mouth of the Santa Clara Valley of the South. 

 During the recent depression of the coast the stream of this valley 

 would have been engaged rather in building up its grade than in 

 corrading its channel. During the post-Pliocene elevation, how- 

 ever, the conditions must have been, in general, different, and 

 during at least a part of that time the stream has been engaged in 

 re-excavating its valley, partially filled during the Pliocene depres- 

 sion. At such times it must have furnished considerable detritus 

 to the neighboring coastal currents. It is not at all improbable, 

 therefore, that at some time (or times) during the later stages of 

 the coastal elevation, when drift was abundant or other conditions 

 were especially favorable, the eastern ridge was built to the very 

 surface of the ocean, so as to make a land connection with, at least, 

 the eastern islands of the group, and afterward broken down by 

 waves and currents during later movements of the land. 



The broad embayment of the southern part of the California 

 coast had, during Pliocene and a part, at least, of post-Pliocene 

 times, a much greater extent than at present, since it included a 

 broad area of comparatively shallow water, extending from the 

 present coast line inland to the eastward of Los Angeles. Along 

 shore it extended from just north of Santa Monica to Newport 

 Bay. This area, which will be spoken of as the Los Angeles 

 embayment, is now a low plain, bordered by mountains on all sides 

 except the seaward facing; and near the center of its coastal 

 border stands the isolated mass of San Pedro Hill. 



Coastal Topography. — The comparative value of the various 

 factors concerned in the evolution of coastal topography can best 

 be learned from the study of actual occurrences where one or more 

 of these factors, through unusual development, become of prime 

 importance in the formation of certain coastal features, or where, 

 through the variation of some other factor or factors, the factor under 

 consideration becomes of relatively greater importance. Such has 

 been made the main basis for the following conclusions. Owing to 

 the variety of conditions presented, the field under discussion, is an 



