﻿J. LeConte — Elevation of the Sierra Nevada. 175 



highest summits and deepest canons, viz : about the head waters 

 of the King and Kern rivers. 



The relation of the Tertiary to the present river-beds is 

 unique only in middle California, because there the lava-flow 

 was sufficient only to rill up the valleys, not to cover deeply 

 the divides. On these divides therefore the rivers located their 

 new channels. Farther north the lava-flood was so deep and 

 universal that either the rivers have not been able to cut 

 through, or if they have, there is no definite relation of these 

 channels to the old channels. Farther south the lava did not 

 extend and the rivers were not displaced. 



Contemporaneous Movement in the Plateau and Basin Regions, 



We have already seen, p. 170, that the inner gorge of the 

 Grand Canon was formed by a second elevation of the Plateau 

 region, and that according to Dutton, this movement took place 

 at the end of the Tertiary. It is almost certain then, that it 

 was correlated with the Post-tertiary elevation above insisted 

 on. The new river-canons of mid-California, the deeper por- 

 tions of the canons of Southern California, and the inner gorge 

 of the Grand Canon are contemporaneous and produced by the 

 same general movement. The movement in the Sierra was ac- 

 companied by a prodigious outflow of lava. In the Plateau 

 region it was attended by the formation of a system of N. and 

 S. fissures several hundred miles long, breaking the crust of 

 the earth into huge oblong blocks which, settling unequally, 

 have given rise to those wonderful N. and S. displacement-cliffs 

 which equally with the E. and W. erosion-cliffs (p. 170), are a 

 characteristic feature of the region. It was attended here also 

 with outflows of lava, but on a lesser scale than in California. 

 It was attended also with a readjustment, if not the formation, 

 of the great fissures and faults of the Basin region. In con- 

 nection with the elevation of the Sierra, the great fault-scarp 

 on the east side of the Sierra was doubtless increased. The 

 same is true of the fault-scarp on the west side of the Wasatch 

 range. The elevation therefore was not only general over the 

 whole region, but also local, i. e. greater along these ranges. 



Contemporaneous movements in Southern Oregon. 



The Basin region, as long ago shown by Gilbert and Howell*, 

 is affected by a system of N. and S. fissures breaking the crust 

 of the earth into oblong blocks, which in settling have been 

 mostly tilted so as to give rise to a series of monoclinal N. and 

 S. ridges. This is well shown in the following fig. (fig. 8) 

 taken from Howell. We have already said these were pro- 



* Wheeler Survey, vol. iii. 



