A Sinkhole, also known as a cenote, sink, sink-hole, swallet, swallow hole, or doline (the different terms for sinkholes are often used interchangeably), is a depression or hole in the ground caused by some form of collapse of the surface layer. Most are caused by karst processes – the chemical dissolution of carbonate rocks or suffosion processes. Sinkholes vary in size from 1 to 600 m (3.3 to 2,000 ft) both in diameter and depth, and vary in form from soil-lined bowls to bedrock-edged chasms. Sinkholes may form gradually or suddenly, and are found worldwide.
What do you call it? Structural movement, Structural Subsidence, Sinkhole or sink hole, Foundation crack, Slab crack, Erosion?
Sinkholes may capture surface drainage from running or standing water, but may also form in high and dry places in specific locations. Sinkholes that capture drainage can hold it in large limestone caves. These caves may drain into tributaries of larger rivers.
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. Sinkholes often form through the process of suffosion. For example, groundwater may dissolve the carbonate cement holding the sandstone particles together and then carry away the lax particles, gradually forming a void.
Occasionally a sinkhole may exhibit a visible opening into a cave below. 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.
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. Sinkholes also occur in sandstone and quartzite terrains.
As the rock dissolves, spaces and caverns develop underground. These sinkholes can be dramatic, because the surface land usually stays intact until there is not enough support. Then, a sudden collapse of the land surface can occur.
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.
Sinkhole Artificial processes
Collapses, 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. More commonly, collapses 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.
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 a collapse of the roof of an existing void or cavity in the subsurface, resulting in development of a sinkhole.
Definition Of Sinkhole
1: a hollow place or depression in which drainage collects
2: a hollow in a limestone region that communicates with a cavern or passage
A sinkhole is a hole in the ground that forms when water dissolves surface rock. Often, this surface rock is limestone, which is easily eroded, or worn away, by the movement of water.
In a landscape where limestone sits underneath the soil, water from rainfall collects in cracks in the stone. These cracks are called joints. Slowly, as the limestone dissolves and is carried away, the joints widen until the ground above them becomes unstable and collapses. The collapse often happens very suddenly and without very much warning. Water collects in these collapsed sections, forming sinkholes.
Sinkholes also form when the roofs of caves collapse. Sinkholes are often funnel-shaped, with the wide end open at the surface and the narrow end at the bottom of the pool.
Sinkholes vary from shallow holes about 1 meter (3 feet) deep, to pits more than 50 meters (165 feet) deep. Water can drain through a sinkhole into an underground channel or a cave. When mud or debris plugs one of these underground caves, it fills with water to become a lake or a pond.
Sinkholes occur naturally, especially where there is abundant rainfall, and the rock beneath the surface soil is limestone. For instance, a cenote (pronounced “seh-NOH-tay”) is a type of sinkhole that forms when the roof of an underground cave collapses, exposing the water to the surface. Cenotes are very common on the Yucatan Peninsula of Mexico. There are more than 2,000 cenotes on the Yucatan, and they are a main source of fresh water for people there. Ancient Mayans believed cenotes were passageways to the underworld.
People can create sinkholes when building roads, aquifers, or other types of construction. Altering land in these ways can weaken the underlying rock and make it more susceptible to sinkholes. Sinkholes can open up in the middle of busy streets or in neighborhoods, especially during heavy rainfall.
The land surrounding the Dead Sea in the Middle East is prone to sinkholes because of the prevalence of rock salt, which is easily dissolved by water. Tourists who are unaware of sinkholes and even scientists studying sinkholes have been injured by falling into them.
Some parts of the United States are very susceptible to sinkholes. In May 2008, a large sinkhole formed in Daisetta, Texas, a suburb of Houston. The sinkhole formed when an underground mound of rock salt collapsed. The sinkhole swallowed several cars, oil drilling equipment, and oil tanks. In one day, the Daisetta sinkhole had grown to 200 meters (656 feet) in diameter and 75 meters (246 feet) deep. Within a couple weeks a 23-meter (7-foot) deep lake had formed in the sinkhole, and a 2-meter (7-foot) alligator had taken up residence in the waters.
What Is A Sinkhole And How Are They Caused?
There are many reasons why a sinkhole is created in the ground, but here are some of the leading causes resulting in devastating sinkholes in that region (Panos, 2020).
Water is the reason for 90 per cent of the sinkholes occurs in any area. Here are some of the reasons given which will elaborate my opinion.
Like gypsum rocks and limestone rocks, some of the rocks can be easily dissolved in water and made cavities in the rocks. It leads to the formation of sinkholes, and this process is known as weathering (Grape, n.d.). Water could be stored for few days to 100 and 1000 years, and when the limit ended, the soil collapses and a sinkhole is formed.
Rock does not dissolve in water:
It happens when rocks do not dissolve in water and create a layer of the rocks below the surface. But these rocks are minor and move from their place due to the flow of water and causes a sinkhole. Like in Guatemala in 2010, a triple story building dropped by a sinkhole and caused the death of 15 people. It all happened due to the weak layer of rocks under the ground (Research, n.d.).
This situation is due to the flow of water movement above the ground. Due to water flow, the surface behind the land gets leaked and after that cause a sinkhole in that region.
Due to human activities like explosions, industrial works and collapsing the surface due to mining, sinkholes are created, which causes the loss of hundreds of lives and buildings.
It includes the natural causes of the formation of a sinkhole, the areas where limestone, clay or sand is the land’s inner surface. When an earthquake occurs, it causes these surface to collapse and causes sinkholes.
Some dangerous sinkholes are listed below:
The giant Qattara natural sinkhole, located west of Cairo, Egypt, is the world’s largest natural sinkhole, measuring 80 kilometres long and 120 kilometres high.
This deadly, sludge-filled soft sandpit has an otherworldly appearance and a staggering scale. The scheme would include digging a trench from Qattara’s edge to the Mediterranean, then allowing the sink to fill with water through a tunnel eventually (Levin, 2019).
The new lake would eventually grow to rival Lake Eerie’s size (at least 160 years in the future), at which stage the desert sun would evaporate any extra water supply. They’re pretty sure it will, at the very least.
A variety of desert sinkholes can be found in Egypt. The almost incomprehensibly large Qattara hole is entirely natural, having formed due to furious winds tearing through the slimy salt beds down to the water table. Qattara is the minty-green field (Panos, 2020).
The Great Blue Hole, Belize
With its beautiful circular depth of almost 1,000 feet, the Great Blue Hole in Belize is among the most spectacular sinkhole shows in the world.
This sinkhole off the coast of Belize is over 400 feet deep and has darker water the deeper you reach, allowing you to see underwater rock formations (Grape, n.d.).
The earth pushes you in Soviet Russia. The sinkhole in Berezniki started in 1986 and has only gotten worse with time.
It measures more than 200 metres deep, 80 metres high, and 40 metres wide.
It’s important to note that this region produces 10% of the world’s potash, and the sinkhole is dangerously close to damaging the mine’s only rail line (Levin, 2019).
Xiaozhai Tiankeng, China
It is also the world’s most enormous sinkhole since it was found in 1994 during the China Caves Project exploration.
Such a double depth sinkhole has a waterfall in its depth of over 2,100 ft, thanks mainly to an underwater river in the Chinese forests. The entire hole measures 2,000 feet in length and 1,760 feet in width (Grape, n.d.).
The upper bowl is over 1,000 feet wide, with a further 1,100 feet of fall in the lower bowl.
Filling Of The Sinkholes
Here are some tips related to the filling of sinkholes:
Take care of your surroundings. Clean out the depression with any litter, vegetation, or other clutter.
Using effective drilling and digging, try to assess the size of the opening.
Fill the depression gradually with fill soil containing a high percentage of clay and a low percentage of sand. Debris or rock should not be used as fill material. Water will trickle through the cracks in the gravel to create an even deeper cavity below if you do so (Levin, 2019).
Keep doing this until the depression is consistent with the ground. Since the fill soil will compress and accumulate with time, you will want to overfill the void. Make sure the ground slopes away from the base to prevent water from getting along the foundation walls. The ground should slope away from the base walls, preferably at a 5 percent gradient over a 10-foot period.
Before planting, you might want to set down a few inches of topsoil or potting soil above the filled field to improve that a new sinkhole does not appear. Topsoil may assist in the establishment of vegetation.
You should either plant seeds or use landscaping materials (Grape, n.d.).
Open sinkholes bind surface and groundwater, allowing toxins applied to the site to reach specific water sources directly. Sinkholes used to be a familiar spot for dumping waste, such as rusted metals and pesticide cans. These practices resulted in heavily contaminated wells until the issue was finally detected, and the procedure was primarily discontinued (Levin, 2019).
Grape, L. (n.d.). Sinkhole – Solving Drainage and Erosion Problems. Retrieved from Fairfax County: https://www.fairfaxcounty.gov/soil-water-conservation/drainage-problem-sinkhole
Levin, N. (2019). 11 Largest Sinkholes in the World. Retrieved from Largest.org: https://largest.org/nature/sinkholes/
Panos, A. (2020). What are the causes of sinkholes? Retrieved from ice: https://www.ice.org.uk/news-and-insight/latest-ice-news/what-are-the-causes-of-sinkholes
Research, B. (n.d.). What causes sinkholes and where do they occur in the UK? Retrieved from BGS Research: https://www.bgs.ac.uk/geology-projects/sinkholes-research/what-causes-sinkholes-where-uk/