What are Sinkholes?

A sinkhole is the depression of the surface layer into underground cavities. The depression of the ground can be caused by several reasons, it can be one reason in particular or a combination of such. In other words, it is a natural depression that may be formed when the land surface collapses. The sinkholes are often the result of groundwater broadening cavities in limestone or other easily soluble bedrock (Sinkhole, n.d.). However, they can be also the result of human interaction with the ground such as oil drilling (Galloway, Jones, Ingebritsen, 1999, p. 110).

Cover-Collapse Sinkhole, Winter Park 1981
Photograph by Tom Scott

Sinkholes vary in size and shape, they can be soil-lined bowls or bedrock-edge crevasses. The settling of the ground can be gradually or it can be sudden. The most dangerous type of subsidence is the sudden and unexpected collapse of the land surface into underground cavities. Usually, this phenomenon occurs when the groundwater level declines either by pumping it or by the redirection of the ground water flow.

According to Galloway et al., (1999), in the United States are more than 17,000 squares miles have been directly affected by subsidence. Among the main causes of this phenomenon are underground mining, natural compaction, hydro-compaction, aquifer-systems compaction, and drainage of organic soils (p. 1).

United States Geological Survey/ Hyndman David, Hydman Donald, 2017

This map shows the areas that are susceptible to sinkholes and other types of subsidence. While there are higher possibilities of sinkholes in some regions, they can occur anywhere in the United States.

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Works Cited