PHYSICAL AXD CLIMATIC SETTING 7 



Basin Sea and on their west rolled the waves of the 

 primeval sea which was in a way the progenitor of 

 the Pacific Ocean. These waters and the cloud- 

 deluges that drained into them scoured from the as- 

 cending ridges the sediment which they brought up, 

 depositing it to a depth of thousands of feet in the 

 depressions the uprising ridges left undisturbed. 

 However, this first effort of the earth-crust to form a 

 California was a failure. In the course of geologic 

 time its uplifts were again submerged, carrying be- 

 neath the primeval flood its shallow river-beds to be 

 buried under renewed sedimentation. After a few 

 more millions of years, the earth-crust made a new 

 effort. The Great Basin Sea was drawn off toward 

 the north. The most potent creative agencies were 

 invoked. By a stupendous uplift the Sierra Nevada 

 arose, carrying thousands of feet aloft the old stream- 

 beds and other tokens of the primitive land which 

 failed. Volcanoes broke out, raised high cones to 

 form great mountains and to spread lava crusts of 

 great depth over thousands of square miles. Then 

 came new upward movement carrying the Sierra Ne- 

 vada much higher than at present, and the local oc- 

 currence of the ice age. Glaciers ground down the 

 igneous rocks that had arisen and cut deep gorges 

 in which ran new rivers carrying new depths of 

 sediment to form broader valleys between and around 

 the mountains. The Sierra Nevada was ice-clothed. 

 The Coast Range had many of the growing-pains of 

 the Sierra Nevada but in less degree. Later an era 

 of subsidence dropped the coast region of the State 



