3. Karst mapping in the United States: Past, present, and future Open Access

The earliest known comprehensive karst map of the entire United States was published in 1969, based on compilations of William E. Davies of the U.S. Geological Survey (USGS). Various versions of essentially the same map have been published since. The USGS published new digital maps and databases in 2014 depicting the extent of known karst, potential karst, and pseudokarst areas of the United States, including Puerto Rico and the U.S. Virgin Islands. These maps are based primarily on the extent of potentially karstic soluble rock types, and rocks with physical properties conducive to the formation of pseudokarst features. These data were compiled and refined from multiple sources at various spatial resolutions, mostly as digital data supplied by state geological surveys. The database includes polygons delineating areas with potential for karst tagged with attributes intended to facilitate classification of karst regions. Approximately 18% of the surface of the 50 United States is underlain by significantly soluble bedrock. In the eastern United States, the extent of outcrop of soluble rocks provides a good first approximation of the distribution of karst and potential karst areas. In the arid western states, the extent of soluble rock outcrop tends to overestimate the extent of regions that might be considered as karst under current climatic conditions, but the new data set encompasses those regions nonetheless. This database will be revised as needed, and the present map will be updated as new information is incorporated.