These data were compiled to delineate the distribution of karst and potential karst and pseudokarst areas of the United States. The data in this report are preliminary, and there is an expectation of upgrade in content, quality, and resolution in future versions. The data are released as an Open-File Report to expedite transfer of this information to various users across the United States.
These data were compiled from multiple sources at various spatial resolutions. They are intended for use as guidance in determining the distribution of areas of potential karst at national, State, and regional scales. Because of differences in projection and scale of the various geologic datasets, spatial errors and location inconsistencies are particularly noticeable along some State boundaries, particularly coastlines and riparian borders. These data should not be used to define boundaries for site-specific applications or for legal purposes. This report describes new digital maps delineating areas of the United States, including Puerto Rico and the U.S. Virgin Islands, having karst or the potential for development of karst and pseudokarst.
These maps show areas underlain by soluble rocks and also by volcanic rocks, sedimentary deposits, and permafrost that have potential for karst or pseudokarst development. All 50 States contain rocks with potential for karst development, and about 18 percent of their area is underlain by soluble rocks having karst or the potential for development of karst features. The areas of soluble rocks shown are based primarily on selection from State geologic maps of rock units containing significant amounts of carbonate or evaporite minerals. Areas underlain by soluble rocks are further classified by general climate setting, degree of induration, and degree of exposure. Areas having potential for volcanic pseudokarst are those underlain chiefly by basaltic-flow rocks no older than Miocene in age.
Areas with potential for pseudokarst features in sedimentary rocks are in relatively unconsolidated rocks from which pseudokarst features, such as piping caves, have been reported. Areas having potential for development of thermokarst features, mapped exclusively in Alaska, contain permafrost in relatively thick surficial deposits containing ground ice. This report includes a GIS database with links from the map unit polygons to online geologic unit descriptions.