Geographic Character: Central Division. 107 
the Uintah range having an east and a west trend, and thus forming a con- 
necting link between the eastern ranges of the Rocky Mountains and the 
western, or Wahsatch range, which borders the Great Basin on its eastern 
side. The Rocky Mountains in Montana and Idaho are more irregular than 
the Park Mountains. An important range is the Bitterroot which forms the 
main divide between the Missouri River and Columbia river drainage basins. 
The Coeur d’Alene ranges lie west and northwest of the Bitterroots. The 
Big Horn Mountains lie to the east and still farther in that direction are the 
Black Hills, which are separated from the main Rocky Mountain system. 
The Great Basin without an outlet to either ocean lies between the 
Wahsatch Mountains on the east and the Sierra Nevada mountains on the west. 
It is an area containing great ranges of mountains with broad valleys between 
them threaded by few streams, as the region is essentially an arid one. Salt lakes 
abound, usually found in the smaller basins of which the Great Basin consists, 
Great Salt Lake, which receives part of the drainage of the Wahsatch moun- 
tains, is in the east an inland sea of about 2000 square miles (5180 qkm) and 
strongly saline through the action of the enormous evaporation of this region. 
Two valleys in the Great Basin lie below the level of the sea. One of 
these is called Death Valley and is found in eastern California. It is a 
desert Iying between the Amargosa and Panamint ranges. The second de- 
pressed basin is in southern California and is denominated the Colorado 
Desert from 100—200 feet below the sea. A low water-parting shuts it off 
from the Gulf of California and the Colorado River. In times of freshet in 
the latter, the river overflows and forms a shallow lake in this depression, 
known as Salton Lake. — Two rivers of the Great Basin merit attention. The 
Humboldt River rises in the Humboldt Range and flows south-westward, to 
disappear in the Humboldt sink. This river waters a narrow belt in each valley, 
which it crosses, and this is true of the Sevier River, which after a long 
sinuous course empties what little water remains in its channel into Sevier Lake. 
Great Salt Lake is the remnant of a much larger lake which geologists 
tell us covered a large part of the area of the Great Basin. The shore-line 
can be easily traced high up on the mountains that surround the Basin. This 
former lake has been called Lake Bonneville and it had its outlet north- 
ward into Snake River. The Basin ranges extend far down into Mexico, 
and have a north-and-south direction. The mountains are never high and are 
often destitute of large trees, and sometimes are mountain deserts. The blocks 
out of which the ranges are carved are uplifted abruptly, so that the rocks 
dip gently away to the other side. These ranges have been modified by 
vulcanism and the volcanic material is often piled up in peaks and small 
plateaus. The Colorado River of the West naturally divides the region into a 
northern and a southeastern portion '). 
1) Power, Jonn W.: Physiographie Regions of the United States. National Geographie Mono- 
graphs Vol. I, No.3. 1895. 
