PHYSICAL GEOGRAPHY 87 



VALLEYS OF THE TRANSVERSE BELT 

 The lowland valleys of Southern California are of 

 many kinds and, owing to the plain-like character of 

 the bottoms of the larger of these, we term them 

 the valley plains. Some of these, like the Colorado 

 and Mojave Deserts, are of very large magnitude. 

 The details of these are well known and cannot be 

 particularized here. Others of less magnitude are 

 herein described as the Foothill Valleys and the 

 Downey Plain. Besides these there are several propor- 

 tionately narrow, smaller and elongated, ribbon-like 

 valleys which occur along or between the great fault 

 lines and which are trough-like and sometimes of the 

 graben type. Of this latter type are the valleys of 

 LaCanada, the Elsinore, Elizabeth Lake and similar 

 valleys along the San Andreas Rift, the east belt of 

 the larger San Jacinto Valley and parts of the passes 

 known as the Tejon, Cajon and San Gorgonio. Like- 

 wise the Chuckwalla, Pinto and Amboy Valleys of the 

 Desert Side are apparently of this graben type, but 

 this is not certain. 



The Santa Clara River occupies a long and narrow 

 synclinal valley. There are various other kinds of 

 small valleys, some of them in the highland areas 

 called "potreros" ; notably the San Jacinto and Morongo 

 Indian Reservation Potreros in the foothills on either 

 side of San Gorgonio Pass and many others, particu- 

 larly those of the Peninsula Ranges. The two in- 

 stances first mentioned occur at the intersections of 

 fault lines. 



There are also downcutting stream-course valleys, 

 particularly in the mountain areas, but these are either 

 absent, shallow, or otherwise inconspicuous in the 



