Sinkholes are the drama queens of geological formations. They occur when groundwater dissolves the rock beneath topsoil over time. Particular kinds of soluble rock are more susceptible to dissolving. Places with limestone, gypsum, and salt beds are all more prone to sinkholes opening. The openings are spectacular to see. Rock dissolves over time, and one day the topsoil just collapses into the ground, taking with it anything and everything attached; building, cars, even unsuspecting people. Because, they sometimes occur in crowded cities and residential neighborhoods. Most noteworthy are these five. They’re the biggest in the world, but a bigger one could open up any time.
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Umpherston Sinkhole, South Africa
Locals call this picturesque sinkhole “The Sunken Garden.” It opened after groundwater eroded a section of limestone, creating caves. Then the top of the cavern collapsed, leaving this sinkhole. In 1886, James Umpherston, a settler and politician in South Africa, beautified the sinkhole and opened it to the public. In the evenings, possums fill the gardens in the sinkhole, feeding on pests that gather in the floodlights.
It’s not natural causes creating the sinkholes consuming this Russian city. Rather, Berezniki was built on top of a massive potash mine in the Ural mountains. In 2006, fresh spring water flooded the chambers of the mine, eroding the remaining columns holding the cavern ceilings in place. The sinkholes appear indiscriminately, the largest bears the nickname “Grandfather,” measuring 450 by 225 feet. (x)
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A corroded sewer system was responsible for the mysterious noises residents heard for weeks in 2007. The noises led up to the collapse of this 62 mile deep sinkhole. It’s an almost perfect circle that killed five citizens and caused the evacuation of over a thousand more. Because of the corroded system, sewage leaked into the ground, dissolving limestone and volcanic ash beneath the street. In 2010, a second sinkhole opened. This one was 300 feet across and swallowed a three story factory. Again sewage pipes were to blame, along with hurricane season, and a volcano eruption. (x)
Four sinkholes, discovered in Venezuela in 1961, mark the landscape of Cerro Sarisarinama. They’re all almost perfect circles, and the largest, Sima Humboldt, measures 219 by 195 feet across. Each sinkhole contains within it a unique ecosystem, separate from the surrounding jungle. (x)
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Finally, you can find this massive sinkhole at the second lowest place in Africa at 436 feet below sea level. Since the early 20th century, politicians and developers have seen potential in the desert. While politicians have considered developing the depression, with everything from hydroelectric energy plants to flooding. Only a sinkhole remains in the Northwest Egyptian desert. Sludge and quicksand fill the actual sinkhole which measures 50 by 75 miles.