Soils that are susceptible to collapse are deposited or formed in semi-arid to arid terrain. There also needs to be terrain that 1) has the clay- and silt-rich rocks that are the ultimate source materials that erode and supply the sediments for the formation of the soils, and 2) the topographic relief and/or depositional environment where meta-stable, low density soils can form. The image below is a block diagram from the Roaring Fork River valley in west-central Colorado that shows those landforms and surfical deposits. These types of depositional environments are widespread in Colorado. Click here for a map of the state that shows the locations of collapsible soil case histories CGS compiled for its study.

Block diagram of an actual digital elevation model from CGS Map Series 34. Tan areas are those types of surficial deposits that may be susceptible to collapsible soils. The blue and purple shaded areas are underlain by evaporite bedrock where sinkholes are potential hazards.

Click here for more information about evaporite karst and sinkholes in Colorado.