Karst is a distinctive topography in which the landscape is largely shaped by the dissolution of carbonate bedrocks (usually limestone, dolomite, or marble). This geological process, occurring over many thousands of years, results in unusual surface and subsurface features ranging from sinkholes, vertical shafts, disappearing streams, and springs, to complex underground drainage systems and caves.
Karstic aquifers can contain significant groundwater resources due to their high porosity. Groundwater is stored in fractures and partings, which are caused by metamorphism, uplift and weathering. In carbonate rocks like limestone, these fractures may become considerably enlarged due to dissolution of the limestone (calcium carbonate). Karstic aquifers such as in limestone regions can contain considerably more groundwater than other fractured rock aquifers. An example is the Jenolan Caves west of Sydney, where large underground caverns store and transmit very large quantities of groundwater.