Mountains of the South 231 



types of the great series of metamorphic and igneous rocks. 

 Tertiary lavas occur along important fault zones. The ancient 

 sedimentary formations which were intruded, cut, and injected 

 by igneous molten rocks from the depths of the earth have been 

 largely removed by erosion. Only remnants of them remain 

 in the form of metamorphic quartzites, schists, and marbles 

 (crystalline limestone). 



The San Gabriel Range is divided into north and south 

 parallel ridges or ranges by a valley that extends east and west 

 almost through the range. The East and West forks of the 

 San Gabriel River meet near the center of the range, and from 

 here the main river flows south and across the alluvial San 

 Gabriel Valley, which lies at the base of and parallel with the 

 range. (The alluvial San Gabriel Valley is not the valley of 

 San Gabriel River.) East from the head of the East Fork of 

 San Gabriel River the middle fork of Lytle Creek occupies the 

 valley leading eastward nearly to Cajon Pass. West from the 

 West Fork Tujunga Canyon opens west and south to La Canada 

 Valley, which is the western continuation of the alluvial San 

 Gabriel Valley. The range or ridge lying south of the east-west 

 valley is the Sierra Madre Range. The main range lies to the 

 north and is generally higher than the Sierra Madre. The 

 Sierra Madre has its culminating point in Cucamonga Peak, 

 8,91 1 feet. The highest point in the north range is San Antonio 

 Peak (Old Baldy) , 10,080 feet. South of the alluvial San 

 Gabriel Valley and La Canada Valley are the Verdugo Mountains 

 and the San Rafael Hills. These are cut off from the San Gabriel 

 Range by the fault which extends along the foot of the main 

 range. 



The San Bernardino Mountain Range 



The San Bernardino Mountain range is a faulted block ex- 

 tending 80 miles in a generally easterly direction from Cajon 

 Pass. The width of the range in its western portion, where 

 both the height and the width are greatest, is about 30 miles. 



