Why sinkholes around the world

Construction workers stand near a sinkhole along a street in the city of Amiens, northern France, on August 13, The five meter deep and ten meter wide sinkhole appeared in the centre of Amiens overnight on August 11, which the local municipal services believe could have been triggered by the collapse of a medieval cave in the vicinity. A sinkhole is seen in a condominium complex, Jan. The hole is estimated to be about 80 feet long and 20 feet wide.

A sinkhole that the government reported was caused by mine work nearby has grown wider since it opened in July in Coyuca de Catalan, Guerrero State, Mexico, seen here on Aug. This image made from a May 2, video shows a huge sinkhole the length of two football fields and the depth of a six-story building on a farm in Rotorua, New Zealand. A worker stumbled upon the chasm before dawn this week when he was rounding up cows for milking on the farm near the North Island town of Rotorua.

It appeared after several days of heavy rainfall. A large sinkhole opened next to a construction dig on a residential street in Rome, swallowing several parked cars but causing no reported injuries, Feb.

Nate left destruction in south Nicaragua with roads, businesses and houses damaged along with hundreds of fallen trees. A van remains in a sinkhole, Sept. In this aerial photo, debris is strewn about after a sinkhole damaged two homes in Land O' Lakes, Fla.

A sinkhole that started out the size of a small swimming pool and continued to grow has swallowed a home in Florida and severely damaged another. A sinkhole that opened up May 3, , behind a Windermere, Fla. A car falls into a hole in a flooded street, as heavy rainfall hits Mersin, Turkey, Dec. Louis police officer looks over a large hole in 6th Street, June 29, , in St.

Nongle sinkhole, China: Large areas in China, especially in the provinces of Guangxi and Guizhou, are covered in limestone formations, deposited in a former ocean some to million years ago and later pushed above sea level by tectonic forces. Large sinkholes in China are called tiankengs , or "sky holes.

The Great Blue Hole, Belize: A beautiful circular diameter of nearly 1, feet gives us what is called the Great Blue Hole in Belize, one of the most impressive displays of sinking in the world. The Great Blue Hole, located off the coast of Belize, is a sinkhole researchers believe is the largest of its kind, at over ft across and ft deep. Undersea explorer Jacques Cousteau made the site famous in by declaring it one of the best diving places in the world.

What's at the bottom of the Great Blue Hole in Belize? Whether caused by human activity or by nature, recent ones or ancient ones - sinkholes are intriguing formations the creation of which involves the unstoppable forces of nature. Visit www. Follow us on :. Kirti Pandey. Updated Jun 05, IST. Some sinkholes - especially the ancient ones covered by vegetation or seawater - are downright exotic.

Some recent ones occurring in cities look scary. Some are shaped like shallow bowls or saucers whereas others have vertical walls; some hold water and form natural ponds. Typically, sinkholes form so slowly that little change is noticeable, but they can form suddenly when a collapse occurs.

Such a collapse can have a dramatic effect if it occurs in an urban setting. The map below shows areas of the United States where certain rock types that are susceptible to dissolution in water occur. In these areas the formation of underground cavities can form, and catastrophic sinkholes can happen. These rock types are evaporites salt, gypsum, and anhydrite and carbonates limestone and dolomite. Evaporite rocks underlie about 35 to 40 percent of the United States, though in many areas they are buried at great depths.

Since Florida is prone to sinkholes, it is a good place to use to discuss some different types of sinkholes and the geologic and hydrologic processes that form them. The processes of dissolution, where surface rock that are soluble to weak acids, are dissolved, and suffusion, where cavities form below the land surface, are responsible for virtually all sinkholes in Florida.

Dissolution of the limestone or dolomite is most intensive where the water first contacts the rock surface. Aggressive dissolution also occurs where flow is focused in preexisting openings in the rock, such as along joints, fractures, and bedding planes, and in the zone of water-table fluctuation where groundwater is in contact with the atmosphere.

Rainfall and surface water percolate through joints in the limestone. Dissolved carbonate rock is carried away from the surface and a small depression gradually forms. On exposed carbonate surfaces, a depression may focus surface drainage, accelerating the dissolution process.

Debris carried into the developing sinkhole may plug the outflow, ponding water and creating wetlands. Gently rolling hills and shallow depressions caused by solution sinkholes are common topographic features throughout much of Florida. Cover-subsidence sinkholes tend to develop gradually where the covering sediments are permeable and contain sand.

In areas where cover material is thicker, or sediments contain more clay, cover-subsidence sinkholes are relatively uncommon, are smaller, and may go undetected for long periods. Cover-collapse sinkholes may develop abruptly over a period of hours and cause catastrophic damages. They occur where the covering sediments contain a significant amount of clay. Over time, surface drainage, erosion, and deposition of sinkhole into a shallower bowl-shaped depression.

Over time, surface drainage, erosion, and deposition of sediment transform the steep-walled sinkhole into a shallower bowl-shaped depression. New sinkholes have been correlated to land-use practices, especially from groundwater pumping and from construction and development practices.

Sinkholes can also form when natural water-drainage patterns are changed and new water-diversion systems are developed. Some sinkholes form when the land surface is changed, such as when industrial and runoff-storage ponds are created. The substantial weight of the new material can trigger an underground collapse of supporting material, thus causing a sinkhole.

The overburden sediments that cover buried cavities in the aquifer systems are delicately balanced by groundwater fluid pressure. The water below ground is actually helping to keep the surface soil in place. Groundwater pumping for urban water supply and for irrigation can produce new sinkholes in sinkhole-prone areas. If pumping results in a lowering of groundwater levels , then underground structural failure, and thus, sinkholes, can occur. Do you think you know about groundwater?

Quiz icon made by mynamepong from www. Follow me to the Land Subsidence website! Roads, buildings, and other types of construction may cause water to collect in certain areas and wash away the supporting rock layer especially at low sea levels and after a heavy rainfall.

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