Along the edge at [Mesa] Verde, caves in Cretaceous Mesa Verde sandstone were used for shelter by Indians. Springs near the bases of the caves, which provided the Indian communities with water, probably contributed to the undermining of the sandstone cliffs. (Colorado Department of Highways photo)
Springs
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.
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.