Mountains of the South 253 



which extends along the northeast base of the Santa Ana Moun- 

 tains, was one of the controlling factors in the origin of the 

 mountain range. The Elsinore fault splits into the Whittier 

 and Chino faults a few miles southeast of Corona. The Whit- 

 tier fault crosses the Santa Ana Canyon about midway of the 

 canyon, and the Chino fault is less than a mile east of the upper 

 end of the canyon. Evidence of the uplifting of the land near 

 these faults is seen in terrace gravels along the canyon high 

 above the level of the stream, remnants of an old floodplain of 

 the river that has been uplifted (but not crumpled or folded) . 

 That these gravel terraces were elevated in comparatively recent 

 time is shown by the occurrence of known Quaternary (San 

 Pedro) beds in undisturbed layers west and north of Horseshoe 

 Bend near the west end of the canyon. There is no evidence 

 of recent disturbance in these deposits. Whether the faults 

 are permanently "dead" or not we do not know. Whether 

 there was any uplifting of the mountains during the earthquakes 

 that occurred in recent time we do not know. The deposits 

 mentioned show no disturbance, which is negative evidence that 

 the mountains have not been uplifted since the deposits were 

 laid down. The Ferris Plain and adjacent regions were, how- 

 ever, "shaken." The uplifting of a range of mountains, such 

 as the Santa Ana Mountains, implies that there has been move- 

 ment in the crust of the earth of considerable magnitude along 

 the Elsinore, Whittier, and Chino faults in time past. Whether 

 the time is entirely past or not we do not know. 



Mountains of Southern California 

 fart of Great System 



Thus it will be seen from this hasty glance at the mountains 

 that Southern California is marked by mountain ranges of great 

 extent. From the boundary of Mexico, where the International 

 Boundary line crosses the great Peninsular Range, mountain 

 ranges form a somewhat broken line along the Pacific Coast 

 throughout the length of the State. Northward from the 



