Mountains of the South 251 



by streams, so that broad terraces now stand along the sides of 

 valleys, remnants of the former plain of deposit. 



East Face of Range Marked by Fault 



The east slope of the Santa Ana Mountain range is definitely 

 and abruptly cut off at its base by the fault which marks the 

 east side of the uplifted block. This is the Elsinore fault, a con- 

 tinuation southward of the Whittier fault. It may be traced 

 southward a distance of 50 miles. Elsinore Lake lies in a de- 

 pressed valley or basin caused by the sinking of a fault block 

 east of the line of the Elsinore fault. Sierra Peak, near the north 

 end of the range, is more than 3,000 feet in altitude. The 

 altitude of the crest of the range increases southward, and cul- 

 minates in Santiago Peak, which is 5,680 feet in height. Much 

 of the higher part of the range is so rugged as to be reached 

 with difficulty, even on foot, and many slopes are practically 

 impassable. 



Up the steep escarpment from north of Lake Elsinore a 

 highway has been constructed across the range. Along this 

 highway the granite rock that forms the core of the mountains 

 is exposed, and also the metamorphic rocks that were intruded 

 by the molten magma. The granite and the metamorphosed 

 rocks have been broken into blocks which show crushing and 

 polishing (slickensiding) due to the fault movement. Near the 

 top of the mountain a striking feature is that of giant blocks 

 of granite in the form of huge boulders which have been formed 

 by erosion and chemical action. These immense granite blocks, 

 rounded by wind and weather, project above the surface as 

 boulders. These form an outstanding feature of this mountain 

 region and are well worth the climb over this mountain high- 

 way to see. 



The highway continues to the west through the gently 

 rolling country with its many scattered boulders of granite pro- 

 jecting through the meager coating of residual soil, and passes 

 downward into San Juan Canyon. Contact between the gran- 



