THE QUATERNARY PERIOD IN EUROPE. 569 



This elevation of the Sierra took place at the end of the Tertiary or 

 beginning of the Quaternary, and doubtless contributed greatly to the 

 severity of the glaciation in California, but must not be confounded 

 with the northern continental movement, which occurred about the 

 same time, and was far more efficient in determining general glaciation. 

 Coincident with the Sierra elevation by block-tilting, as already ex- 

 plained (p. 265), similar orogenic movements took place in the Basin 

 region. Thus it is seen that the river-beds of California show, not con- 

 tinental crust-oscillations like those of the East, but mountain-making 

 by crust-block-tilting. 



We have seen that the submarine channels of the California coast 

 differ from those of the Eastern coast, in that they are not continuous 

 with the present subaerial river- channels. We have also just seen that 

 the river-beds of the Sierra differ from those on the Eastern coast, in 

 that they have been displaced from their old positions, and have cut 

 much deeper. Now, the reason of this difference is probably the same 

 in the two cases, viz., recent orogenic changes. We have seen that the 

 Sierra took its present form and height at the beginning of the Qua- 

 ternary. It is probable that great orogenic changes occurred at the 

 same time in the Coast Range also. In both cases, too, the orogeny was 

 attended with floods of lava. Much of the lava, and presumably many 

 of the ridges of the Coast Range, were formed at that time. By these 

 changes the mouths of the rivers were changed from their original places. 



History of the Sierra Range. — This range was born out of the ocean 

 by horizontal crushing and bulging, as already explained (p. 252), at 

 the end of the Jurassic. During the whole Cretaceous and Tertiary it 

 was subjected to erosion, until by the end of that time the rivers had 

 reached their base-levels, and the range was reduced to very moderate 

 height. The crest was then about the region of the Yosemite, for the 

 erosion into the granite is deepest about that region. Then came, at 

 the end of the Tertiary and beginning of the Quaternary,- the tilting of 

 the Sierra earth-block, the formation of the great fault-cliff, and the 

 transference of the crest to the extreme eastern side ; the outpouring 

 of the lava ; the displacement of the rivers ; and the cutting of the new 

 river-beds. By this great movement, the already old Sierra was re- 

 juvenated, and entered upon a new cycle of changes by erosion, which 

 is still progressing. 



TJie Quaternary Period in Europe. 



In Europe the phenomena were more irregular, the oscillations 

 more numerous, and perhaps more local, than in America. This is in 

 accordance with the general difference in the geological history of the 

 two continents. Nevertheless, the general character of the phenomena 

 was similar in the two countries. 



