Sinkholes form in karst terrain principally from the collapse of surface sediments into underground cavities in the limestone bedrock. Slightly acidic ground water slowly dissolves cavities and caves in the limestone over a period of many years. When the cavity enlarges to the point that its ceiling can no longer support the weight of overlying sediments, the earth collapses into the cavity. In the less catastrophic, type of sinkhole, a bowl-shaped depression forms at the surface, usually over a considerable period of time.
Sinkholes occur naturally, but are also induced by human activities. Pumping water from a well can trigger sinkhole collapse by lowering the water table and removing support for a cave’s roof. Construction over sinkholes can also cause collapse. Sinkhole development may damage buildings, pipelines and roadways. Damage from the Winter Park sinkhole in Florida is estimated at greater than $2 million. Sinkholes may also serve as routes for the spread of contamination to groundwater when people use them as refuse dumps.
Sinkholes occur worldwide, and in the United States are common in southern Indiana, southwestern Illinois, Missouri, Kentucky, Tennessee, and Florida. In areas with known karst topography, subsurface drilling or geophysical remote sensing may be used to pinpoint the location of sinkholes.
