Sinkholes can also form when natural water-drainage patterns are changed and new water-diversion systems are developed. They can also occur from the overpumping and extraction of groundwater and subsurface fluids.
More commonly, collapses occur in urban areas due to water main breaks or sewer collapses when old pipes give way. Artificial processes Ĭollapse formed by rainwater leaking through pavement and carrying soil into a ruptured sewer pipe.Ĭollapses, commonly incorrectly labeled as sinkholes also occur due to human activity, such as the collapse of abandoned mines and salt cavern storage in salt domes in places like Louisiana, Mississippi and Texas. On 2 July 2015, scientists reported that active pits, related to sinkhole collapses and possibly associated with outbursts, were found on the comet 67P/Churyumov-Gerasimenko by the Rosetta space probe. Then, a sudden collapse of the land surface can occur. These sinkholes can be dramatic, because the surface land usually stays intact until there is not enough support. Sinkholes also occur in sandstone and quartzite terrains.Īs the rock dissolves, spaces and caverns develop underground. Sinkholes are common where the rock below the land surface is limestone or other carbonate rock, salt beds, or in other soluble rocks, such as gypsum, that can be dissolved naturally by circulating ground water. In the case of exceptionally large sinkholes, such as the Minyé sinkhole in Papua New Guinea or Cedar Sink at Mammoth Cave National Park in Kentucky, an underground stream or river may be visible across its bottom flowing from one side to the other.
Occasionally a sinkhole may exhibit a visible opening into a cave below. For example, groundwater may dissolve the carbonate cement holding the sandstone particles together and then carry away the lax particles, gradually forming a void. Sinkholes often form through the process of suffosion. The formation of sinkholes involves natural processes of erosion or gradual removal of slightly soluble bedrock (such as limestone) by percolating water, the collapse of a cave roof, or a lowering of the water table. These caves may drain into tributaries of larger rivers. Sinkholes that capture drainage can hold it in large limestone caves. Sinkholes may capture surface drainage from running or standing water, but may also form in high and dry places in specific locations.
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