252 Adventures in Scenery 



ite and the metamorphic slates will be observed. At San Juan 

 Hot Springs a series of hot springs come up along fissures close 

 to the line of contact between the granite and the Triassic 

 slates. Continuing down San Juan Canyon Cretaceous and 

 Tertiary formations are crossed, and broad terraces which show 

 evidence of many successive uplifts. 



Region Broken by Many Faults 



At the south end of the Santa Ana Mountains Temecula 

 River crosses the south end of the range where the mountains 

 give way to the San Juan Capistrano basin, 40 miles south from 

 the Narrows at the north end of the range. No other stream 

 crosses the uplifted range throughout the 40 miles of its length 

 till the Santa Ana River is reached. The mountain range is 

 cut across by the Santa Ana River in the Narrows, a canyon 

 which divides the main range from the Puente Hills and San 

 Jose Hills to the north, these hills being regarded as the con- 

 tinuation of the Santa Ana Range. From the axis of the Santa 

 Ana Range, high above the Coastal Plain, the slope toward the 

 west is gentle. Toward the east from the crest of the range the 

 slope is very abrupt to the Elsinore Valley, the descent to which 

 is down the fault scarp along which the range was uplifted. 

 The high crest of the range has been much rasped and eroded 

 by wind and weather, and the ancient intruded magma, long 

 since cooled and crystallized to hard granite, is exposed at the 

 surface. The eastern steep fault-wall is very rugged. Whether 

 movement along the fault- plane is still going on we do not 

 positively know. That movement has occurred in time geo- 

 logically recent is known. Whether the mountain crest is still 

 being uplifted we do not know. The mountain range is young 

 as a geologic feature of the landscape. Faults along which no 

 movement has occurred within historic time such as to cause 

 earthquakes are spoken of as "dead" faults. Movements on the 

 San Andreas, San Jacinto, Elsinore, and Inglewood faults have 

 occurred within recent historical time. The Elsinore fault, 



