176 MINERAL SPRINGS OF THE UNITED STATES. [bou 
Mr. G. K. Gilbert 1 has called attention to the fact that the geological 
relations appear to accord with this hydro-thermal contrast between the 
Western States and the other divisions of the country. He refers the 
greater heat in the former to local uprisings of the geiso-thermal plain's, 
together with progressive corrugation, the intensity of the phenomena 
being heightened by the intrusion and extrusion of lavas. 
The connection of hot and warm springs with volcanic rocks, with 
uplifted mountain chains, and with dislocations or fractures of strata 
has long been recognized. Our Western States present all these con- 
ditions. Here are the most elevated portions of our country and with 
the upward movement still in progress. A single glance at the general 
geologic map of the United States suffices to show that in this portion 
of our domain evidences exist of most intense volcanic activity, both 
past and present. 
The Western States have been subdivided into four divisions, viz, 
the Rocky Mountain region, the Plateau region, the Great Basin, and 
the Pacific Coast. In the Rocky Mountain States, mountain corruga- 
tion is probably the primary cause of the hot springs found, although 
igneous areas are not wanting, as notably in the case of the Yellowstone 
National Park, in Wyoming. In the Pacific Coast region the uplifts of 
the Sierras and Coast Ranges are accompanied by igneous rocks, and 
as we proceed northward, volcanic outbursts form a striking feature. 
Almost all the springs on our Alaska list are warm or hot and in Alaska 
we find the volcanic forces still active. 
In the Great Basin, mountain corrugation is subordinate to the fault- 
ing of the strata as a cause of hot and warm springs. Mr. I. C. Russell 
describes this region as follows: 2 
u The whole immense region lying between the Sierra Nevada and 
Rocky Mountain systems has been broken by a multitude of fractures, 
having an approximately north and south trend, that divide the region 
into long, narrow, orographic blocks." 
With these profound faults hot springs are associated, and a map of 
the hot springs of the Great Basin would be, to a great extent, also a 
map of the lines of displacement. With these displacements also are 
associated volcauic rocks. In the plateau region again we find a simi- 
lar association of faulted strata and the former outpouring of igneous 
rocks. 
Although thermal springs are so characteristic of tbe Western States, 
other classes are not wanting. Alkaline, saline, chalybeate, and calcic 
springs are numerous ; many of them are carbonated and still more are 
sulphureted. Silicious springs, not prominent in other sections, are 
found abundantly in the areas of hot springs. 
1 Report of tbe United States Geographical Surveys West of tbe 100th Meridian, Vol 
III, pp. 147-140. 
2 Fourtb Annual Report of tbe United States Geological Survey, 1882-'83, p. 443. 
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