256 



Adven hires in Scenery 



present valley, that is, the bed-rock below the filling of alluvium 

 and the crumpled and folded clays and sandstones, is hundreds 

 of feet below the present surface, estimated to be as much as 

 3,000 feet in some of the lower places. 



A Worn-down Plain of Erosion 



Back in Pliocene time (late Tertiary) about six or seven 

 million years ago southern California was considerably nearer 



FIG. 74. Cloister wing, Mission Inn, Riverside. 



sea level than now. The mountain ranges, San Bernardino, San 

 Gabriel, San Jacinto, and Santa Ana, with the San Bernardino 

 Valley and Ferris Plain between them, and differing greatly 

 in elevation, once formed a continuous surface. It may seem 

 strange to think of the top of the San Bernardino Mountains as 

 part of a plain that once extended to Lake Elsinore and the 

 broad plain about Perris. The San Bernardino Mountains were 



