530 VOSE PAH ALTEANGONTE 
life; by the formation of a fissure on the eastern slope, the 
hheaving of the whole mountain block on its eastern side with a 
great eastern fault-scarp,; the transference of the crest to the 
extreme margin with great increase of the western slope and 
consequent revival of the erosive energy of the rivers. Coinci- 
dent with this in middle California there was a great outpouring 
of lava which ran in streams down the western slope, filling up 
the old river beds, and displacing the rivers. The displaced 
rivers, with recently and fiercely aroused energy, immediately 
commenced cutting new channels, which are now 3000 to 6000 
feet deep, and far below the old; so that these latter are left 
with their lava-covered gravels high up on the present divides 
This was the work of the Ozarkian. This intensely interesting 
geological story has been so often told that we only recall here 
its outlines in order to apply them to the case in hand. 
In southern California, beyond the limits of the lava flows 
this post-Tertiary elevation and revival of erosive energy was 
fully as great, or even greater than in middle California; but the 
rivers were not displaced, and therefore they continued to cut in 
the same places, but to far deeper levels ; so that the margins of 
the wide old river beds with their gravels are left hung up high 
on the sides of the present canyons.? The distinction, however, 
between the wide shallow tertiary troughs and the deep narrow 
post-Tertiary canyons is equally sharp here. 
We have spoken thus far only of the deep canyons which 
trench the western slope as being of post-Tertiary origin ; but the 
same is true also of the whole scenery of the high Sierra. It all 
belongs to the post-Tertiary, and its bold, rugged, savage gran- 
deur is due to its extreme recency. The wildness of youth has 
not been yet tempered and mellowed by age. 
It is evident then that the Ozarkian is here sharply marked 
off from the Tertiary. How is it in regard to its relation to the 
present? In the lower parts of the canyons the Ozarkian grades 
insensibly into the present, for the rivers are still, cutting. But 
tAm. Jour. Sci., Vol. XX XII, 167, 1886. 
2 Am. Jour. Sci., Vol. XXXII, 174, 1886. 
