The multitudes of mineral and hot springs in Colorado are a fascinating
and interesting facet of the Mountain Province. Some are located along
major faults, where the rocks are so broken and shattered that
groundwater can move freely toward the surface. Colorado Springs,
Manitou Springs, and Eldorado Springs are on the fault complex that
forms the east edge of the Front Range. Glenwood, Juniper, Steamboat,
and Poncha Springs are on well defined faults also.
[Illustration: Glenwood Hot Springs flow from Pennsylvanian shales of
the Belden Formation, where sedimentary layers are faulted by the sharp
upward tilting against the south side of the White River Plateau. Behind
the hotel and on the right can be seen the Mississippian Leadville
Limestone, cut by the Colorado River. (From a painting by William H.
Jackson, courtesy of Colorado State Archives and Public Record)]
Many other springs do not seem to be controlled so strongly by faulting,
but owe their presence to sources of volcanic or magmatic heat which
exist near to the surface of the ground. Some springs of this type issue
from Precambrian granite, or Cenozoic volcanic rock, while others flow
from sedimentary rock layers. Waunita Hot Springs and Pagosa Springs,
although near volcanic rocks, reach the surface through porous
sandstones and shales of Cretaceous age. Mt. Princeton Hot Springs comes
from alluvium but its heat source is the intrusive igneous rock which
makes up part of the adjacent mountain.
Springs of another general type are also present in Colorado where
aquifers, generally sandstones, are dissected by erosion. These springs,
usually not highly mineralized or warm, are most often found in the
Plateau Province. Such springs are frequent at the bases of the great
sandstone cliffs of Mesa Verde and Colorado National Monument.
Manitou’s carbonated springs, which attract many tourists, have their
origin in the arrangement and nature of the rocks through which the
water flows. Water from the Pikes Peak region, slightly acid from its
contact with the granitic rock, flows into the Manitou limestone all
along Ute Pass fault, which extends from Cheyenne Mountain northwest to
Woodland Park. Descending through channels along the fault, the water
becomes pressurized. Because of its pressure and its acid content, it
partly dissolves the calcium carbonate of the limestone, and from then
on carries carbon dioxide in solution. As the water comes to the surface
at the low point of the fault exposure, near the west edge of Manitou,
the pressure is released and the carbon dioxide effervesces, just as a
bottle of soda water effervesces when the cap is removed.