1 . The Coast Ranges: In general, the Coast Ranges are a rela- 

 tively old range of rather low mountains that rise abruptly at the 

 immediate coastline of the Pacific Ocean. The orientation of 

 these ranges is north to south. Between the major north-south 

 ridges there are numerous valleys ranging in size from very small 

 ones to sizable ones such as the Napa, Sonoma, and Salinas 

 valleys. The Coast Ranges are interrupted at San Francisco Bay: 

 the mountains of this system that occur north of the bay are 

 called the North Coast Ranges, those south of the bay are called 

 the South Coast Ranges. 



2. Sierra-Cascade axis: Geologically these two mountain 

 systems have had different origins, but since they form a contin- 

 uous north-south high mountain range they can be considered 

 together. The Cascade Range, which is extensively developed in 

 Oregon and Washington, reaches its southern limit in northern 

 California and is terminated there by Mt. Lassen (10,453 ft, 

 3,186 m elev.). The range is volcanic in origin throughout most 

 of its area. The Sierra Nevada is exclusively a CaUfornia range 

 which is generally non-volcanic in origin and which is character- 

 ized by the occurrence of immense expanses of granitic rocks. 

 These mountains originated by faulting. They rise gradually to a 

 crest that is frequently well above 10,000 feet (3,050 m), and 

 the range drops off very sharply to the east. Unlike the Cascades, 

 the Sierra Nevada range consists of a series of ridges, with the 

 major peaks (such as Mount Whitney) rather poorly differentiated 

 from the surrounding peaks. There is evidence of extensive glaci- 

 ation in the higher reaches of the Sierra Nevada, and this glacia- 

 tion is beheved to have had an important effect on the present 

 distribution of some woody plants in these mountains. 



The Sierra-Cascade ranges are heavily vegetated, with various 

 forest types on the lower slopes and with alpine or other montane 

 herbaceous or shrubby vegetation in the upper regions. Despite 

 the difference in geological origin between the ranges, there is 

 relatively good continuity in the vegetation types running from 

 one range into the other. 



3. Klamath Mountains: These are a geologically and topo- 

 graphically complex series of mountain ranges that occur in 



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