Karst Sinkhole in Ekhtiarabad, NW Kerman

Ekhtiarabad sinkhole which is located 14 km NW of Kerman, near a homonymus Village, appeared suddenly in July the first, 1998. Mechamism of formation of the cave system which created the hole is of great importance for detecting suspected subterranean caves in the region. In this regard, several ideas have been put forward, namely,dissolution of evaporites, dissolution of limestone, and mechanical wash-out of fine sands (piping). To resolve this problem, geologic and hydrogeologic conditions of the region were analysed, and a hydrogeochemical approach, based upon evaporite dissolution index, was proved to be efficient. The index is over 40 in the vicinity of the hole, but decreases abruptly away from it to less than 5, indicating dissolution of evaporites, which seem to be gypsum. Some other clues, such as electrical conductivity of groundwaters, evaporitic facies of Neogen sediments, and a nearby gypsum mine all increase this possibility. Several mechanisms; as decline in groundwater level, trrafics, and enhanced disssolution induced by pumping groundwat ers are suspected as collapsed triggers.