Colorado Geology

This creation of the Rockies as they exist now occurred between 60 and 70 million years ago; as the peaks rose, they were eroded by the elements. Wind and water carried the eroded material, creating the Great Plains. As the tectonic plates collided, some were pushed deep into the earth. They melted and formed liquid rock, creating volcanoes and lava fields. In south-central Colorado are the remains of an enormous ancient supervolcano that produced the largest single eruption known in the earth's entire geologic history: the eruption rained volcanic material so quickly that the layers retained enough heat to weld back into solid rock. This rock mixed with gases and the volcano collapsed back on itself to create a deep crater.

The volcanoes created the environment for vast mineral wealth in the region. Hot waters dissolved and reacted with the rock, creating ore deposits of gold, silver, copper, lead, zinc, and other minerals, including uranium. The most productive deposits of uranium and vanadium are in the Uravan mineral belt, a relatively small area in southwestern Colorado. The belt extends from Gateway through Uravan to Slick Rock. The carnotite deposits (a source of uranium) are part of a larger pattern of deposits in southwestern Colorado, southeastern Utah, northeastern Arizona, and northwestern New Mexico.

Bill Gillette/U.S. Environmental Protection Agency, Underground uranium mining in Nucla, Colorado, May 1972, National Archives and Records Administration

Colorado has a long history of mining. The search for gold and silver in the mid-1800s and the creation of mines throughout the Colorado Mineral Belt were important factors in Colorado becoming a U.S. territory and, in 1876, a state. This settler-colonial process entailed taking land from the Plateau tribes in order to exploit mineral resources, including coal resources, which helped drive continued expansion. While mining for uranium began in the late 19^th century, with the rise of nuclear power after World War II, the element increased in importance. Waves of prospecting and development of the state’s uranium resources resulted in an increase in the settler-colonial population and industrialization, and the displacement of the Ute Mountain Ute and other Native communities in order to satisfy the uranium frenzy on the Colorado Plateau.

Presently, the prevalence of hard-rock mining has diminished in Colorado. Colorado citizens and government agencies continue to wrestle with the physical hazards and environmental impacts caused by mining. There are an estimated 23,000 abandoned mine sites on both public and private land. Environmental issues like water quality degradation and increased sedimentation continue to represent some of the key issues faced by citizens today. Acid mine drainage is water that is discharged from mining related activities; the drainage can degrade the water quality of streams and water supplies, harming aquatic life. Sedimentation occurs by surface runoff, which leads to the blockage of streams and can result in flooding of roads and residences as well as harming fish.

Sources

Colorado Geological Survey / Colorado School of Mines. "Abandoned Mine Lands." Accessed March 26, 2018.

Colorado Geological Survey / Colorado School of Mines. "Ground Subsidence." Accessed March 26, 2018.

Fischer, R. P. and L. S. Hilpert. "Geology of the Uravan Mineral Belt." Geological Survey Bulletin 988-A. U.S. Department of the Interior, Geological Survey. U.S. Government Printing Office, 1952. Accessed March 26, 2018.