OF-14-13 Geologic hazards derivative map of the Whitewater quadrangle, Mesa County, Colorado

This map is a derivative map created from information compiled on OF-14-09 Geologic Map of the Whitewater Quadrangle, Mesa County, Colorado. The following hazards have been either mapped or identified: rockfall, landslides, and problematic soils and bedrock that have the potential to swell (expand) or subside (collapse or settle).

The topography of this quadrangle is dominated by the Gunnison River and tributary creeks. Rockfall hazards occur below cliffs, found along the river and creek canyon rims. Landslides form in two general geomorphic conditions. The most extensively formed are very large ancient landslide complexes within the canyons where weak claystones of the Morrison Formation are exposed below the rim rocks and have failed, causing retrogressive toppling and slumping failures of the Dakota Sandstone and Burro Canyon Formation cap rock. The second system consist of smaller landslides and soil slips along mesa bluffs where Pleistocene gravel caps high terrace remnants that are underlain by Mancos Shale.

Problematic soils and bedrock contain properties that cause volumetric changes, generally when they become wetted beyond their original natural condition. There are two basic mechanisms: Swelling or expansive soil and bedrock, and compactive (collapsible) or settling soil and bedrock. Problematic soils derived from shale bedrock can also be corrosive to certain metals and concrete.

A more in-depth discussion of the hazards and the general areas they occur in may be found in the Author’s Notes on the geologic map. Map and GIS data are provided. Digital ZIP download. OF-14-13D