No abstract available.

Abstract Salt (halite, NaCl) is the most soluble of common rocks; it is dissolved readily and forms a range of subsidence or collapse features as a result of human activities. Bedded or domal salt deposits are present in 25 of the 48 contiguous United States and underlie nearly 20% of the land area. These salts occur in 17 separate structural basins or geographic districts in the United States, and either local or extensive examples of natural or man-made salt karst are known in almost all of these basins or districts. Human activities have contributed to the development of salt karst. Boreholes or underground mines may enable (either intentionally or inadvertently) unsaturated water to flow through or against the salt deposits, thus allowing development of small to large dissolution cavities. If the dissolution cavity is large enough and shallow enough, successive roof failures can cause land subsidence or catastrophic collapse. Because salt dissolution proceeds rapidly, human-induced karst features often develop quickly and with dramatically adverse impacts. Industries associated with local salt-dissolution and collapse features include solution mining (e.g., Cargill sink, Kansas; and Grand Saline sink, Texas), petroleum activities (e.g., the Wink sinks, Texas; Panning sink, Kansas; and Gorham oil field, Kansas), and underground, dry mining of salt (e.g., Jefferson Island mine, Louisiana; and Retsof mine, New York).