Small but significant areas of Colorado are underlain by Mesozoic and/or Paleozoic evaporite deposits. The purpose of this map is to describe the geologic conditions where near-surface evaporite rocks occur in Colorado and to provide a general description and hazard potential of ground subsidence that can occur from rock dissolution in evaporite terrain. The publication includes a statewide map (1:500,000 scale), an illustrated 28-page map discussion report, and GIS data.
From a geologic hazard standpoint, the most important characteristic of evaporite bedrock is that they dissolve in the presence of fresh water. The dissolution of evaporite rock alters ground and surface water flows, and creates subsurface voids such as caverns, open fissures, and solution pipes. Collapse of these subsurface voids manifests itself at the surface as subsidence — a geologic hazard and risk for overlying structures. Ground and surface water can be captured by the subsurface voids to create closed topographic basins and disappearing streams, subterranean rivers, and re-emergent springs. These landforms are described collectively as karst morphology.
The data includes those areas of Colorado underlain by near-surface evaporite bedrock and point locations of sinkholes and subsidence features where they have been discerned. Digital ZIP download. OF-12-02D