From Encyclopedia Jr, free information reference for Kids
Devil's Hole near
Hawthorne, Florida
Sinkholes, also known as sinks, shakeholes, swallow holes or dolina (in the Slovene language dolina means valley), and cenotes, are a feature of landscapes that are based on limestone bedrock. They are found worldwide. One form is the collapse of a cave roof. The result in this case is a depression in the surface topography. This may range anywhere from a small, gentle earth-lined depression, to a large, cliff-lined chasm. Most often there is a small area of rock exposure near or at the bottom of a sinkhole, and a patent opening into the cave below may or may not be visible. In the case of exceptionally large sinkholes, such as Cedar Sink at Mammoth Cave National Park, there may actually be a stream or river flowing into the bottom of the sink from one side and out the other side.
Sinkholes often form in low areas where they form drainage outlets for a running or a standing water. They may also form in currently high and dry locations. Florida has been known for having frequent sinkholes, especially in the central part of the state.
A special type of sinkhole - formed by rainwater leaking through the pavement and carrying dirt into a ruptured sewer pipe
Sinkholes are usually but not always linked with a karst landscape. Karst represents a set of surface features that are characteristic of limestone under the soil. In many such regions, there may be hundreds or even thousands of sinkholes in a small area so that the surface as seen from the air looks pock-marked. Often in such areas there are few or no flowing streams on the surface because the drainage occurs sub-surface.
Sinkholes have for centuries been used as disposal sites for various forms of waste. A consequence of this is the pollution of groundwater resources, with serious health implications in such areas.
Sinkholes also form from human activity, such as the rare but still occasional collapse of abandoned mines in places like West Virginia. More commonly, sinkholes occur in urban areas due to water main breaks or sewer collapses when old pipes give way. They can also occur from the overpumping and extraction of groundwater and subsurface fluids.
Natural sinkholes can be very deep, offering extremely challenging conditions for adventurous and experienced divers. Some of the most spectacular are the Zacaton cenote in Mexico, the Boesmansgat sinkhole in South Africa, Sarisariñama tepuy in Venezuela, and in the town of Mount Gambier, South Australia.
[edit] See also
- Cenote
- Pipe Creek Sinkhole
- Sarisariñama
- Stockertown, PA
[edit] External links
