Mechanisms of surface subsidence resulting from solution extraction of salt

Extraction of soluble minerals, whether by natural or man-induced processes, can result in localized land-surface subsidence. The subsidence is caused by partial or total collapse of underground cavities resulting from dissolution of salt or other soluble evaporites. In many cases, subsidence is ultimately related to the strength limit of the overlying rocks that form the unsupported roof above the cavity. If sufficient underground space is available for the loosely packed rock debris to collect, the void can migrate to the surface and produce surface subsidence, or in the extreme, catastrophic surface collapse. Ground water can erode and transport the loose material down subsidence-induced and natural cracks, or drill holes into the salt cavity. The voids formed in the higher eroded beds can then cause surface subsidence.--Modified book abstract.