The collapsible-soil susceptibility map viewer contains several layers of coverage — from the CGS publication EG-14 Collapsible Soils of Colorado; from other published regional susceptibility maps; from regional maps not formally published, and from basemaps — as described following:
EG-14 contains in-depth information on how collapsible soils are formed, what their characteristics are, and what are the inherent hazards they pose.
The following specific geologic coverages are derived from the map plate in EG-14. For more in-depth information, refer directly to that publication.
EG-14 Evaporite formations
Exposed evaporite rocks contain soluble minerals and are generally soft, poorly covered with vegetation, and prone to erosion. Highly collapsible soils are well known to occur in alluvial-fan and colluvial depositional systems where sediments are derived from evaporite formations.
EG-14 Cretaceous and Tertiary formations
These poorly indurated bedrock formations, with high percentages of clay and silt, are easily eroded and sediment yield is high. Sediments derived from these formations can have the characteristics of collapsible soils when deposited in alluvial-fan, colluvial, alluvial, and eolian depositional systems.
EG-14 Dune and sheet sand deposits
Dune and sheet sand deposits are generally an exclusion zone for collapsible soils because of the packed grain-to-grain contacts of the sand, unless they have characteristics of the eolian deposits below.
EG-14 Eolian (wind blown) loess deposits
Loess is composed primarily of clayey to sandy silt that accumulates as blanket deposits where wind-blown dusts settles out of the air. The depositional process results in a soil structure with low density, high porosity, and a meta-stable open skeletal fabric. Loess soils are widespread in eastern Colorado and adjacent to the Front Range.
EG-14 18-inch precipitation boundary
This coverage indicates areas of Colorado where annual precipitation exceeds 18 inches (45 cm). The statewide study of Colorado reveals that the higher precipitation is an exclusion zone for collapsible soils. Above 18 inches of annual precipitation, soil-saturation levels increase and potential for soil collapse comes to an end. These zones are generally mountainous areas where significant winter snow pack accumulates.
EG-14 Collapsible soil case history locations
Locations of collapsible soil occurrences that were compiled for the CGS statewide collapsible soil study.
From CGS regional susceptibility maps
Regional coverages were compiled from various CGS publications, on-line downloads, and unpublished sources and are available on the CGS Bookstore. The boundaries of these regional studies are also included as a selectable coverage in the map viewer.
This coverage is one of several digital shapefiles for Douglas County that is part of a series available at the CGS Bookstore.
Coverage is part of a digital publication that includes significant GIS data.
Collapsible soil susceptibility of the Roaring Fork River corridor, Garfield County — map layer for Map Series 34
Collapsible soil susceptibility of the Colorado River corridor in the vicinity of Rifle, Garfield County — map layer for Map Series 47
Collapsible soil susceptibility map in the Rangely-Dinosaur vicinity, Rio Blanco and Moffat Counties — created for the Colorado statewide study of collapsible soil (coverage not currently published).
Collapsible soil susceptibility map of the Montezuma Valley corridor in the vicinity of Cortez, Montezuma County — created for the Colorado statewide study of collapsible soil (coverage not currently published).