160 SOiUTHERN CALIFORNIA GEOLOGY 



Creek, the San Andreas, the San Jacinto, Reche Can- 

 yon, Grapevine Canyon, the Elsinore, San Onofre, 

 and the Inglewood faults respectively. 



SAN GORGONIO PASS 



The pass is itself a wonderful example of the meet- 

 ing and crossing place of rifts of great displacement, 

 of several directional groups and of different ages, 

 which contribute to the making of one of the most 

 beautiful and interesting pieces of earth architecture 

 in America. The oldest of the rifts which compose 

 this complex were probably faults of the north-south 

 directions which outlined the west side of the Colorado 

 depression at the east end of the Pass, and probably 

 was of pre-Miocene age. Movement was revived along 

 it in Pleistocene times as probably indicated in the 

 Whitewater and Palm Springs Faults. Next in age 

 probably were the northeast-exitending Raywood, 

 Potrero, and Morongo faults at the southeast end of 

 the mountain. Then followed the east-west-trending 

 faults of the Transverse Belt — the Banning and Law- 

 rence faults already described — which are of Miocene or 

 earlier age. With their making the great east-west 

 pass between the guardian summits of San Jacinto 

 and San Gorgonio which now border it was first opened 

 across the pre-existing north-south fault scarp of the 

 west side of the Colorado depression. Then came 

 the northwesterly-extending San Andreas rift of Plio- 

 cene and Pleistocene time. This cut diagonally south- 

 eastward across the entire group of older faults as 

 shown in the figure. This may be an older fault line 

 along which there probably was a revival of move- 

 ment, just as a few present-day shocks are the sur- 



