120 
THE GRAND CANON DISTRICT. 
climate passed from a humid to an arid condition, and of two or more 
epochs when a throe of upheaval followed a considerable pei’iod of repose. 
And the presumption will grow stronger, and at last become very powerful, 
that this change of climate and one of the throes of upheaval, the birth of 
the present Grand Canon, the most ancient basaltic eruptions of the Uin- 
karet and Sheavwits, and the starting of the greater faults of the region, 
were not only contemporaneous events, but were mutually associated and 
interdependent. 
The facts which have been recited in this and in the preceding chapter 
seem to me to indicate the following order of sequence in the events which 
have resulted in the production of the Grand Canon. At the close of Mio- 
cene time the larger part of the general denudation of the Mesozoic strata 
had been completed. Considerable masses of the Permian were then remain- 
ing, which have since been eroded. At that time the surface of the country 
was situated at a level not far above the sea, and was at a base level of 
erosion. It had been so for a long stretch of time, sufficient, in fact, to have 
allowed of the obliteration of most of the inequalities which had been gen- 
erated by the upheavals and erosion occurring in late Eocene and early 
Miocene time. At length a new epoch of upheaval set in, hoisting the 
country from 2,000 to 3,000 feet, and somewhat unequally. Under ordi- 
nary circumstances this would have resulted in the production of fresh feat- 
ures by the corrasion of streams. But a change of climate from moist to 
arid had in the meantime occurred. The streams were in chief part dried 
up, leaving only the Colorado and a few of its more powerful tributaries. 
Such streams as remained alive corraded their channels, but the greater part 
of the platform suffered no other havoc than the slow waste by sapping of 
the edges of the Permian remnants in much the same manner as it does at 
the present time. Contemporaneously with the upheaval the Hurricane fault 
was developed. Possibly some form of displacement of much less magni- 
tude than that now existing was ah-eady established; possibl}^ a part 
of the present displacement was effected during this particular throe of 
upheaval. Accompanying the uplifting and faulting movement were the 
earliest volcanic outbreaks, represented by the lava caps of the Trumbull, 
Logan, and Emma platforms. At length the uplifting action paused for a 
