Formations that contain clays having swelling pressures higher than 2,500 pounds per square foot (as measured by the Potential Volume Change meter) are listed in order of decreasing swelling pressure: Denver Formation, Pierre Shale, Laramie Formation, Green Mountain Conglomerate, Fox Hills Sandstone, and Arapahoe Formation. Some landslides derived from these formations also contain swelling clay and are mapped with the bedrock formations listed above.
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USGS Numbered Series
Map Showing Areas Containing Swelling Clay in the Morrison Quadrangle, Jefferson County, Colorado