Documents and data about sinkholes, "one of many kinds of karst landforms, which include caves, disappearing streams, springs, and underground drainage systems. ... Karst is a generic term which refers to the characteristic terrain produced by erosional processes associated with the chemical weathering and dissolution of limestone or dolomite." Provides a FAQ, and a poster showing Florida's sinkholes and diagrams of sinkhole formation. Some material specific to Florida. From the Florida Geological Survey.