Published online by Cambridge University Press: 10 January 2011
Introduction: why are hazards associated with karst important?
Karst refers to terrains in which the geomorphology and hydrology, both at the surface and in the subsurface, are largely governed by dissolution of carbonate and/or evaporite rocks. Some distinctive characteristics of karst environments include: (1) the presence of enclosed depressions (dolines or sinkholes and poljes), swallow holes and large springs; (2) the prevalence of underground drainage through channels resulting from dissolutional enlargement of discontinuity planes. Groundwater flow in these interconnected conduits circulates much faster than in aquifers controlled by granular or fracture permeability (Ford and Williams, 2007). Three main types of karst settings can be differentiated: bare karst, covered or mantled karst and interstratal karst, depending on whether the soluble rocks are exposed at the surface, covered by unconsolidated deposits or overlain by non-karst rocks (caprocks), respectively.
Karst developed in evaporite rocks has distinctive features primarily due to the higher solubility and lower mechanical strength of the evaporites (Gutiérrez et al., 2008a). The equilibrium solubilities of gypsum (CaSO4·2H2O) and halite (NaCl) in distilled water are 2.4 and 360 g/l, respectively. By comparison, the solubilities of calcite (CaCO3) and dolomite (MgCa[CO3]2) minerals in regular meteoric waters are commonly lower than 0.1 g/l. The solubilities of these carbonate minerals are largely dependent on the pH of the water, which is generally controlled by the carbon dioxide partial pressure.
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