14 A GAZETTEER OF UTAH. [bull. 166. 
this valley it begins to burrow into an inclined plateau or series of 
plateaus, which dip gently to the north, directly against its course. 
The canyon rapidly deepens, its depth being increased both by the 
slope of the river and by the rise of the plateau. In this canyon it 
flows for three-score miles, and suddenly emerges into the sunlight in 
Gunnison Valley, at the foot of the Book Cliffs, where it is crossed 
by the Rio Grande Western Railway. This canyon is another result 
of priority of occupation by the stream. 
Beyond Gunnison Valley the river soon enters another canyon, in 
the depths of which it is joined by Grand River, which flows through 
a canyon in the same plateau. Thence the stream, now known as the 
Colorado, pursues a southwestern course through a continuous canyon 
2,000 to 3,000 feet in depth. This canyon in different parts has 
received various names, Labyrinth and Stillwater canyons being 
applied to portions above the junction of the rivers, Cataract Canyon 
to the portion immediately below the junction of the rivers, and Glen 
Canyon to that near the mouth of San Juan River. 
Within this plateau region are three groups of mountains of eruptive 
origin, the La Sal, the Henry Mountains, and Navajo Peak, the latter 
a single dome. These were formed by attempted outbursts of volcanic 
rock in a plastic condition, which, failing to reach the surface, bulged 
up the overlying stratified beds and forced its way between them, thus 
presenting the appearance of being interstratified. Subsequent erosion 
has laid bare the volcanic nucleus and the interstratified beds of 
volcanic rock. 
The country west of the Wasatch and its plateaus is a region drained 
to neither ocean, but to the atmosphere. It forms a part of the great 
interior basin of the North American continent. It consists of many 
basins, some of which are independent, others connected, and separated 
by narrow mountain ranges. The ranges are for the most part short, 
from 20 to 100 miles in length, and consist in the main of monoclinal 
uplifts, with here and there a volcanic peak. The variation in altitude 
is great, but no point is far above the sea. Most of the valleys are 
broad and nearly level, and filled to a great depth with material washed 
from the mountains by winter rains and spring floods, since all the 
detritus brought into them is deposited there as the streams sink. 
GREAT SALT LAKE. 
The greatest of these valleys is that occupied by Great Salt Lake. 
This, which has almost the dimensions of an inland sea, being 80 miles 
in length, and ranging with irregular outlines from 25 to 50 miles in 
width, collects the water from all the streams draining the Wasatch 
Range, the Bear, Weber, Ogden, Provo, American and Spanish forks, 
and many smaller streams. A secondary reservoir, Utah Lake, collects 
