sinkhole

/singk"hohl'/, n.

1. a hole formed in soluble rock by the action of water, serving to conduct surface water to an underground passage.

2. Also called sink. a depressed area in which waste or drainage collects.

[1425-75; late ME; see SINK, HOLE]

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or sink or doline

Depression formed as underlying limestone bedrock is dissolved by groundwater.

Sinkholes vary greatly in area and depth and may be very large. The two main varieties are those caused by the collapse of a cavern roof, and those caused by the gradual dissolving of rock under a soil mantle. Collapsed sinkholes generally have steep rock sides and may receive streams that then flow underground. Soil-mantled sinkholes are generally shallower; they may become clogged with clay and hold a small lake.

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▪ geology

also called  Sink, or Doline,  

      topographic depression formed as underlying limestone bedrock is dissolved by groundwater. It is considered the most fundamental structure of karst topography. Sinkholes vary greatly in area and depth and may be very large. There are two main varieties, one caused by the collapse of the roof of a cavern, the other by the gradual dissolving of rock under a soil mantle. Collapsed sinkholes generally have steep rock sides and may receive streams that then flow underground. The soil-mantled sinkhole is generally shallower than the collapsed sinkhole and receives local drainage; it may become clogged with clay and hold a small lake. Some sinkholes, formed at low sea-level stages during the Pleistocene epoch, are now half-drowned and are known as cenotes (cenote).

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