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A sinkhole is a depression or hole in the ground caused by some form of collapse of the surface layer. The term is sometimes used to refer to doline, enclosed depressions that are locally also known as ''vrtače'' and shakeholes, and to openings where surface water enters into underground passages known as ''
ponor A ponor is a natural opening where surface water enters into underground passages; they may be found in karst landscapes where the geology and the geomorphology is typically dominated by porous limestone rock. Ponors can drain stream or lake wate ...
'', swallow hole or swallet. A ''
cenote A cenote ( or ; ) is a natural pit, or sinkhole, resulting from the collapse of limestone bedrock that exposes groundwater. The regional term is specifically associated with the Yucatán Peninsula of Mexico, where cenotes were commonly used for ...
'' is a type of sinkhole that exposes groundwater underneath. A ''sink'' or ''stream sink'' are more general terms for sites that drain surface water, possibly by infiltration into sediment or crumbled rock. Most sinkholes are caused by karst processes – the chemical dissolution of
carbonate rocks Carbonate rocks are a class of sedimentary rocks composed primarily of carbonate minerals. The two major types are limestone, which is composed of calcite or aragonite (different crystal forms of CaCO3), and dolomite rock (also known as doloston ...
, collapse or
suffosion Suffosion is one of the two geological processes by which subsidence sinkholes or dolines are formed, the other being due to collapse of an underlying cave or void, with most sinkholes formed by the suffosion process. Suffosion sinkholes are normal ...
processes. Sinkholes are usually circular and vary in size from tens to hundreds of
meters The metre ( British spelling) or meter ( American spelling; see spelling differences) (from the French unit , from the Greek noun , "measure"), symbol m, is the primary unit of length in the International System of Units (SI), though its pre ...
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.


Formation


Natural processes

Sinkholes may capture surface
drainage Drainage is the natural or artificial removal of a surface's water and sub-surface water from an area with excess of water. The internal drainage of most agricultural soils is good enough to prevent severe waterlogging (anaerobic condition ...
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 Erosion is the action of surface processes (such as water flow or wind) that removes soil, rock, or dissolved material from one location on the Earth's crust, and then transports it to another location where it is deposited. Erosion is di ...
or gradual removal of slightly soluble bedrock (such as
limestone Limestone ( calcium carbonate ) is a type of carbonate sedimentary rock which is the main source of the material lime. It is composed mostly of the minerals calcite and aragonite, which are different crystal forms of . Limestone forms wh ...
) by percolating water, the collapse of a
cave A cave or cavern is a natural void in the ground, specifically a space large enough for a human to enter. Caves often form by the weathering of rock and often extend deep underground. The word ''cave'' can refer to smaller openings such as se ...
roof, or a lowering of the
water table The water table is the upper surface of the zone of saturation. The zone of saturation is where the pores and fractures of the ground are saturated with water. It can also be simply explained as the depth below which the ground is saturated. T ...
. Sinkholes often form through the process of
suffosion Suffosion is one of the two geological processes by which subsidence sinkholes or dolines are formed, the other being due to collapse of an underlying cave or void, with most sinkholes formed by the suffosion process. Suffosion sinkholes are normal ...
. For example, groundwater may dissolve the carbonate cement holding the
sandstone Sandstone is a clastic sedimentary rock composed mainly of sand-sized (0.0625 to 2 mm) silicate grains. Sandstones comprise about 20–25% of all sedimentary rocks. Most sandstone is composed of quartz or feldspar (both silicates) ...
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 Papua New Guinea (abbreviated PNG; , ; tpi, Papua Niugini; ho, Papua Niu Gini), officially the Independent State of Papua New Guinea ( tpi, Independen Stet bilong Papua Niugini; ho, Independen Stet bilong Papua Niu Gini), is a country i ...
or
Cedar Sink Cedar Sink is a vertical-walled large depression, or sinkhole, in the ground, that is located in Edmonson County, Kentucky and contained within and managed by Mammoth Cave National Park. The sinkhole measures from the top sandstone plateau to the ...
at
Mammoth Cave National Park Mammoth Cave National Park is an American national park in west-central Kentucky, encompassing portions of Mammoth Cave, the longest cave system known in the world. Since the 1972 unification of Mammoth Cave with the even-longer system under F ...
in
Kentucky Kentucky ( , ), officially the Commonwealth of Kentucky, is a state in the Southeastern region of the United States and one of the states of the Upper South. It borders Illinois, Indiana, and Ohio to the north; West Virginia and Virgin ...
, an
underground stream A subterranean river is a river that runs wholly or partly beneath the ground surface – one where the riverbed does not represent the surface of the Earth. It is distinct from an aquifer, which may flow like a river but is contained within a pe ...
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 Carbonate rocks are a class of sedimentary rocks composed primarily of carbonate minerals. The two major types are limestone, which is composed of calcite or aragonite (different crystal forms of CaCO3), and dolomite rock (also known as doloston ...
, salt beds, or in other soluble rocks, such as
gypsum Gypsum is a soft sulfate mineral composed of calcium sulfate dihydrate, with the chemical formula . It is widely mined and is used as a fertilizer and as the main constituent in many forms of plaster, blackboard or sidewalk chalk, and drywa ...
, that can be dissolved naturally by circulating
ground water Groundwater is the water present beneath Earth's surface in rock and soil pore spaces and in the fractures of rock formations. About 30 percent of all readily available freshwater in the world is groundwater. A unit of rock or an unconsolidate ...
. Sinkholes also occur in
sandstone Sandstone is a clastic sedimentary rock composed mainly of sand-sized (0.0625 to 2 mm) silicate grains. Sandstones comprise about 20–25% of all sedimentary rocks. Most sandstone is composed of quartz or feldspar (both silicates) ...
and
quartzite Quartzite is a hard, non- foliated metamorphic rock which was originally pure quartz sandstone.Essentials of Geology, 3rd Edition, Stephen Marshak, p 182 Sandstone is converted into quartzite through heating and pressure usually related to ...
terrains. As the rock dissolves, spaces and
cavern A cave or cavern is a natural void in the ground, specifically a space large enough for a human to enter. Caves often form by the weathering of rock and often extend deep underground. The word ''cave'' can refer to smaller openings such as sea ...
s 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.


Space and Planetary Bodies

On 2 July 2015, scientists reported that active pits, related to sinkhole collapses and possibly associated with outbursts, were found on the
comet A comet is an icy, small Solar System body that, when passing close to the Sun, warms and begins to release gases, a process that is called outgassing. This produces a visible atmosphere or coma, and sometimes also a tail. These phenomena ...
67P/Churyumov-Gerasimenko by the ''
Rosetta Rosetta or Rashid (; ar, رشيد ' ; french: Rosette  ; cop, ϯⲣⲁϣⲓⲧ ''ti-Rashit'', Ancient Greek: Βολβιτίνη ''Bolbitinē'') is a port city of the Nile Delta, east of Alexandria, in Egypt's Beheira governorate. The ...
''
space probe A space probe is an artificial satellite that travels through space to collect scientific data. A space probe may orbit Earth; approach the Moon; travel through interplanetary space; flyby, orbit, or land or fly on other planetary bodies; o ...
.


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 Louisiana , group=pronunciation (French: ''La Louisiane'') is a state in the Deep South and South Central regions of the United States. It is the 20th-smallest by area and the 25th most populous of the 50 U.S. states. Louisiana is borde ...
, Mississippi and
Texas Texas (, ; Spanish language, Spanish: ''Texas'', ''Tejas'') is a state in the South Central United States, South Central region of the United States. At 268,596 square miles (695,662 km2), and with more than 29.1 million residents in 2 ...
, in the United States of America. More commonly, collapses occur in
urban area An urban area, built-up area or urban agglomeration is a human settlement with a high population density and infrastructure of built environment. Urban areas are created through urbanization and are categorized by urban morphology as cities, ...
s due to
water main A water distribution system is a part of water supply network with components that carry potable water from a centralized treatment plant or wells to consumers to satisfy residential, commercial, industrial and fire fighting requirements. Definit ...
breaks or sewer collapses when old
pipe Pipe(s), PIPE(S) or piping may refer to: Objects * Pipe (fluid conveyance), a hollow cylinder following certain dimension rules ** Piping, the use of pipes in industry * Smoking pipe ** Tobacco pipe * Half-pipe and quarter pipe, semi-circul ...
s 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.


Classification


Solution sinkholes

Solution or dissolution sinkholes form where water dissolves limestone under a soil covering. Dissolution enlarges natural openings in the rock such as joints, fractures, and bedding planes. Soil settles down into the enlarged openings forming a small depression at the ground surface.


Cover-subsidence sinkholes

Cover-subsidence sinkholes form where voids in the underlying limestone allow more settling of the soil to create larger surface depressions.


Cover-collapse sinkholes

Cover-collapse sinkholes or "dropouts" form where so much soil settles down into voids in the limestone that the ground surface collapses. The surface collapses may occur abruptly and cause catastrophic damages. New sinkhole collapses can also form when human activity changes the natural water-drainage patterns in karst areas.


Pseudokarst sinkholes

Pseudokarst sinkholes resemble karst sinkholes but are formed by processes other than the natural dissolution of rock.


Human accelerated sinkholes

The
U.S. Geological Survey The United States Geological Survey (USGS), formerly simply known as the Geological Survey, is a scientific agency of the United States government. The scientists of the USGS study the landscape of the United States, its natural resources, a ...
notes that "It is a frightening thought to imagine the ground below your feet or house suddenly collapsing and forming a big hole in the ground." Human activities can accelerate collapses of karst sinkholes, causing collapse within a few years that would normally evolve over thousands of years under natural conditions. Soil-collapse sinkholes, which are characterized by the collapse of cavities in soil that have developed where soil falls down into underlying rock cavities, pose the most serious hazards to life and property. Fluctuation of the water level accelerates this collapse process. When water rises up through fissures in the rock, it reduces soil cohesion. Later, as the water level moves downward, the softened soil seeps downwards into rock cavities. Flowing water in karst conduits carries the soil away, preventing soil from accumulating in rock cavities and allowing the collapse process to continue. Induced sinkholes occur where human activity alters how surface water recharges groundwater. Many human-induced sinkholes occur where natural diffused recharge is disturbed and surface water becomes concentrated. Activities that can accelerate sinkhole collapses include timber removal, ditching, laying pipelines, sewers, water lines, storm drains, and drilling. These activities can increase the downward movement of water beyond the natural rate of
groundwater recharge Groundwater recharge or deep drainage or deep percolation is a hydrologic process, where water moves downward from surface water to groundwater. Recharge is the primary method through which water enters an aquifer. This process usually occurs ...
. The increased runoff from the impervious surfaces of roads, roofs, and parking lots also accelerate man-induced sinkhole collapses. Some induced sinkholes are preceded by warning signs, such as cracks, sagging, jammed doors, or cracking noises, but others develop with little or no warning. However, karst development is well understood, and proper site characterization can avoid karst disasters. Thus most sinkhole disasters are predictable and preventable rather than “ acts of God”. The
American Society of Civil Engineers American(s) may refer to: * American, something of, from, or related to the United States of America, commonly known as the "United States" or "America" ** Americans, citizens and nationals of the United States of America ** American ancestry, p ...
has declared that the potential for sinkhole collapse must be a part of land-use planning in karst areas. Where sinkhole collapse of structures could cause loss of life, the public should be made aware of the risks. The most likely locations for sinkhole collapse are areas where there is already a high density of existing sinkholes. Their presence shows that the subsurface contains a cave system or other unstable voids. Where large cavities exist in the limestone large surface collapses can occur, such the Winter Park, Florida sinkhole collapse. Recommendations for land uses in karst areas should avoid or minimize alterations of the land surface and natural drainage. Since water level changes accelerate sinkhole collapse, measures must be taken to minimize water level changes. The areas most susceptible to sinkhole collapse can be identified and avoided. In karst areas the traditional foundation evaluations (
bearing capacity In geotechnical engineering, bearing capacity is the capacity of soil to support the loads applied to the ground. The bearing capacity of soil is the maximum average contact pressure between the foundation and the soil which should not produce s ...
and settlement) of the ability of soil to support a structure must be supplemented by geotechnical site investigation for cavities and defects in the underlying rock. Since the soil/rock surface in karst areas are very irregular the number of subsurface samples ( borings and
core sample A core sample is a cylindrical section of (usually) a naturally-occurring substance. Most core samples are obtained by drilling with special drills into the substance, such as sediment or rock, with a hollow steel tube, called a core drill. The h ...
s) required per unit area is usually much greater than in non-karst areas. In 2015, the U.S. Geological Survey estimated the cost for repairs of damage arising from karst-related processes as at least $300 million per year over the preceding 15 years, but noted that this may be a gross underestimate based on inadequate data. The greatest amount of karst sinkhole damage in the United States occurs in Florida, Texas, Alabama, Missouri, Kentucky, Tennessee, and Pennsylvania. The largest recent sinkhole in the USA is possibly one that formed in 1972 in Montevallo, Alabama as a result of man-made lowering of the water level in a nearby rock quarry. This "December Giant" or "Golly Hole" sinkhole measures long, wide and deep. Other areas of significant karst hazards include the Ebro Basin in northern Spain; the island of
Sardinia Sardinia ( ; it, Sardegna, label=Italian language, Italian, Corsican language, Corsican and Tabarchino ; sc, Sardigna , sdc, Sardhigna; french: Sardaigne; sdn, Saldigna; ca, Sardenya, label=Algherese dialect, Algherese and Catalan languag ...
; the Italian peninsula; the Chalk areas in southern England;
Sichuan Sichuan (; zh, c=, labels=no, ; zh, p=Sìchuān; alternatively romanized as Szechuan or Szechwan; formerly also referred to as "West China" or "Western China" by Protestant missions) is a province in Southwest China occupying most of t ...
, China; Jamaica; France; Croatia; and Russia, where one-third of the total land area is underlain by karst.


Occurrence

Sinkholes tend to occur in karst landscapes. Karst landscapes can have up to thousands of sinkholes within a small area, giving the landscape a pock-marked appearance. These sinkholes drain all the water, so there are only
subterranean river A subterranean river is a river that runs wholly or partly beneath the ground surface – one where the riverbed does not represent the surface of the Earth. It is distinct from an aquifer, which may flow like a river but is contained within a pe ...
s in these areas. Examples of karst landscapes with numerous massive sinkholes include Khammouan Mountains (
Laos Laos (, ''Lāo'' )), officially the Lao People's Democratic Republic ( Lao: ສາທາລະນະລັດ ປະຊາທິປະໄຕ ປະຊາຊົນລາວ, French: République démocratique populaire lao), is a socialist ...
) and Mamo Plateau (Papua New Guinea). The largest known sinkholes formed in sandstone are Sima Humboldt and Sima Martel in
Venezuela Venezuela (; ), officially the Bolivarian Republic of Venezuela ( es, link=no, República Bolivariana de Venezuela), is a country on the northern coast of South America, consisting of a continental landmass and many islands and islets in th ...
. Some sinkholes form in thick layers of homogeneous limestone. Their formation is facilitated by high groundwater flow, often caused by high rainfall; such rainfall causes formation of the giant sinkholes in the Nakanaï Mountains, on the
New Britain New Britain ( tpi, Niu Briten) is the largest island in the Bismarck Archipelago, part of the Islands Region of Papua New Guinea. It is separated from New Guinea by a northwest corner of the Solomon Sea (or with an island hop of Umboi the D ...
island in Papua New Guinea. Powerful underground rivers may form on the contact between limestone and underlying insoluble rock, creating large underground voids. In such conditions, the largest known sinkholes of the world have formed, like the Xiaozhai Tiankeng (
Chongqing Chongqing ( or ; ; Sichuanese pronunciation: , Standard Mandarin pronunciation: ), alternately romanized as Chungking (), is a municipality in Southwest China. The official abbreviation of the city, "" (), was approved by the State Cou ...
, China), giant sótanos in
Querétaro Querétaro (), officially the Free and Sovereign State of Querétaro ( es, Estado Libre y Soberano de Querétaro, links=no; Otomi: ''Hyodi Ndämxei''), is one of the 32 federal entities of Mexico. It is divided into 18 municipalities. Its cap ...
and
San Luis Potosí San Luis Potosí (), officially the Free and Sovereign State of San Luis Potosí ( es, Estado Libre y Soberano de San Luis Potosí), is one of the 32 states which compose the Federal Entities of Mexico. It is divided in 58 municipalities and i ...
states in Mexico and others. Unusual processes have formed the enormous sinkholes of Sistema Zacatón in
Tamaulipas Tamaulipas (), officially the Free and Sovereign State of Tamaulipas ( es, Estado Libre y Soberano de Tamaulipas), is a state in the northeast region of Mexico; one of the 31 states which, along with Mexico City, comprise the 32 Federal Entiti ...
(Mexico), where more than 20 sinkholes and other karst formations have been shaped by volcanically heated, acidic groundwater. This has produced not only the formation of the deepest water-filled sinkhole in the world—
Zacatón Zacatón is a cenote (a thermal water-filled sinkhole) belonging to the Zacatón system - a group of unusual karst features located in Aldama Municipality near the Sierra de Tamaulipas in the northeastern state of Tamaulipas, Mexico. It is the ...
—but also unique processes of
travertine Travertine ( ) is a form of terrestrial limestone deposited around mineral springs, especially hot springs. It often has a fibrous or concentric appearance and exists in white, tan, cream-colored, and even rusty varieties. It is formed by a pro ...
sedimentation in upper parts of sinkholes, leading to sealing of these sinkholes with travertine lids. The U.S. state of
Florida Florida is a U.S. state, state located in the Southeastern United States, Southeastern region of the United States. Florida is bordered to the west by the Gulf of Mexico, to the northwest by Alabama, to the north by Georgia (U.S. state), Geo ...
in North America is known for having frequent sinkhole collapses, especially in the central part of the state. Underlying limestone there is from 15 to 25 million years old. On the fringes of the state, sinkholes are rare or non-existent; limestone there is around 120,000 years old. The Murge area in southern Italy also has numerous sinkholes. Sinkholes can be formed in retention ponds from large amounts of rain. On the Arctic seafloor,
methane emissions Increasing methane emissions are a major contributor to the rising concentration of greenhouse gases in Earth's atmosphere, and are responsible for up to one-third of near-term global heating. During 2019, about 60% (360 million tons) of methane r ...
have caused large sinkholes to form.


Human uses

Sinkholes have been used for centuries as disposal sites for various forms of
waste Waste (or wastes) are unwanted or unusable materials. Waste is any substance discarded after primary use, or is worthless, defective and of no use. A by-product, by contrast is a joint product of relatively minor economic value. A waste prod ...
. A consequence of this is the pollution of groundwater resources, with serious health implications in such areas. The
Maya civilization The Maya civilization () of the Mesoamerican people is known by its ancient temples and glyphs. Its Maya script is the most sophisticated and highly developed writing system in the pre-Columbian Americas. It is also noted for its art, a ...
sometimes used sinkholes in the
Yucatán Peninsula The Yucatán Peninsula (, also , ; es, Península de Yucatán ) is a large peninsula in southeastern Mexico and adjacent portions of Belize and Guatemala. The peninsula extends towards the northeast, separating the Gulf of Mexico to the north ...
(known as
cenotes A cenote ( or ; ) is a natural pit, or sinkhole, resulting from the collapse of limestone bedrock that exposes groundwater. The regional term is specifically associated with the Yucatán Peninsula of Mexico, where cenotes were commonly used for ...
) as places to deposit precious items and human sacrifices. When sinkholes are very deep or connected to caves, they may offer challenges for experienced
caver Caving – also known as spelunking in the United States and Canada and potholing in the United Kingdom and Ireland – is the recreational pastime of exploring wild cave systems (as distinguished from show caves). In contrast, speleology is ...
s or, when water-filled, divers. Some of the most spectacular are the
Zacatón Zacatón is a cenote (a thermal water-filled sinkhole) belonging to the Zacatón system - a group of unusual karst features located in Aldama Municipality near the Sierra de Tamaulipas in the northeastern state of Tamaulipas, Mexico. It is the ...
cenote in Mexico (the world's deepest water-filled sinkhole), the
Boesmansgat Boesmansgat, also known in English as "Bushman's Hole", is a deep submerged freshwater cave (or sinkhole) in the Northern Cape province of South Africa, which has been dived to a depth of . Boesmansgat was believed to have first been explored by ...
sinkhole in South Africa, Sarisariñama tepuy in Venezuela, the Sótano del Barro in Mexico, and in the town of
Mount Gambier, South Australia Mount Gambier is the second most populated city in South Australia, with an estimated urban population of 33,233 . The city is located on the slopes of Mount Gambier, a volcano in the south east of the state, about south-east of the capital A ...
. Sinkholes that form in coral reefs and islands that collapse to enormous depths are known as
blue hole A blue hole is a large marine cavern or sinkhole, which is open to the surface and has developed in a bank or island composed of a carbonate bedrock ( limestone or coral reef). Their existence was discovered in the late 20th century by fisher ...
s and often become popular diving spots.


Local names

Large and visually unusual sinkholes have been well known to local people since ancient times. Nowadays sinkholes are grouped and named in site-specific or generic names. Some examples of such names are listed below. * Aven – In the south of France this name means pit cave in
occitan Occitan may refer to: * Something of, from, or related to the Occitania territory in parts of France, Italy, Monaco and Spain. * Something of, from, or related to the Occitania administrative region of France. * Occitan language, spoken in parts ...
. * Black holes (not to be confused with cosmic
black hole A black hole is a region of spacetime where gravity is so strong that nothing, including light or other electromagnetic waves, has enough energy to escape it. The theory of general relativity predicts that a sufficiently compact mass can defo ...
s) – This term refers to a group of unique, round, water-filled pits in the Bahamas. These formations seem to be dissolved in carbonate mud from above, by the sea water. The dark color of the water is caused by a layer of phototropic microorganisms concentrated in a dense, purple colored layer at depth; this layer "swallows" the light.
Metabolism Metabolism (, from el, μεταβολή ''metabolē'', "change") is the set of life-sustaining chemical reactions in organisms. The three main functions of metabolism are: the conversion of the energy in food to energy available to run ...
in the layer of microorganisms causes heating of the water. One of them is the Black Hole of Andros. *
Blue hole A blue hole is a large marine cavern or sinkhole, which is open to the surface and has developed in a bank or island composed of a carbonate bedrock ( limestone or coral reef). Their existence was discovered in the late 20th century by fisher ...
s – This name was initially given to the deep underwater sinkholes of the
Bahamas The Bahamas (), officially the Commonwealth of The Bahamas, is an island country within the Lucayan Archipelago of the West Indies in the North Atlantic. It takes up 97% of the Lucayan Archipelago's land area and is home to 88% of the ar ...
but is often used for any deep water-filled pits formed in carbonate rocks. The name originates from the deep blue color of water in these sinkholes, which is created by the high clarity of the water and the great depth of the sinkholes; only the deep blue color of the visible
spectrum A spectrum (plural ''spectra'' or ''spectrums'') is a condition that is not limited to a specific set of values but can vary, without gaps, across a continuum. The word was first used scientifically in optics to describe the rainbow of colors ...
can penetrate such depth and return after reflection. *
Cenote A cenote ( or ; ) is a natural pit, or sinkhole, resulting from the collapse of limestone bedrock that exposes groundwater. The regional term is specifically associated with the Yucatán Peninsula of Mexico, where cenotes were commonly used for ...
s – This refers to the characteristic water-filled sinkholes in the
Yucatán Peninsula The Yucatán Peninsula (, also , ; es, Península de Yucatán ) is a large peninsula in southeastern Mexico and adjacent portions of Belize and Guatemala. The peninsula extends towards the northeast, separating the Gulf of Mexico to the north ...
,
Belize Belize (; bzj, Bileez) is a Caribbean and Central American country on the northeastern coast of Central America. It is bordered by Mexico to the north, the Caribbean Sea to the east, and Guatemala to the west and south. It also shares a wate ...
and some other regions. Many cenotes have formed in limestone deposited in shallow seas created by the Chicxulub meteorite's impact. * Sótanos – This name is given to several giant pits in several states of Mexico. * Tiankengs – These are extremely large sinkholes, typically deeper and wider than , with mostly vertical walls, most often created by the collapse of caverns. The term means ''sky holes'' in Chinese; many of this largest type of sinkhole are located in China. * Tomo – This term is used in New Zealand karst country to describe pot holes.


Piping pseudokarst

The 2010 Guatemala City sinkhole formed suddenly in May of that year; torrential rains from Tropical Storm Agatha and a bad drainage system were blamed for its creation. It swallowed a three-story building and a house; it measured approximately wide and deep. A similar hole had formed nearby in February 2007. This large vertical hole is not a true sinkhole, as it did not form via the dissolution of limestone, dolomite, marble, or any other water-soluble rock. Instead, they are examples of "piping pseudokarst", created by the collapse of large cavities that had developed in the weak, crumbly
Quaternary The Quaternary ( ) is the current and most recent of the three periods of the Cenozoic Era in the geologic time scale of the International Commission on Stratigraphy (ICS). It follows the Neogene Period and spans from 2.58 million yea ...
volcanic deposits underlying the city. Although weak and crumbly, these volcanic deposits have enough cohesion to allow them to stand in vertical faces and to develop large subterranean voids within them. A process called " soil piping" first created large underground voids, as water from leaking
water main A water distribution system is a part of water supply network with components that carry potable water from a centralized treatment plant or wells to consumers to satisfy residential, commercial, industrial and fire fighting requirements. Definit ...
s flowed through these volcanic deposits and mechanically washed fine volcanic materials out of them, then progressively eroded and removed coarser materials. Eventually, these underground voids became large enough that their roofs collapsed to create large holes.


Crown hole

A crown hole is subsidence due to subterranean human activity, such as
mining Mining is the extraction of valuable minerals or other geological materials from the Earth, usually from an ore body, lode, vein, seam, reef, or placer deposit. The exploitation of these deposits for raw material is based on the economic v ...
and military trenches. Examples have included, instances above World War I trenches in
Ypres Ypres ( , ; nl, Ieper ; vls, Yper; german: Ypern ) is a Belgian city and municipality in the province of West Flanders. Though the Dutch name is the official one, the city's French name is most commonly used in English. The municipality ...
,
Belgium Belgium, ; french: Belgique ; german: Belgien officially the Kingdom of Belgium, is a country in Northwestern Europe. The country is bordered by the Netherlands to the north, Germany to the east, Luxembourg to the southeast, France to the ...
; near mines in
Nitra Nitra (; also known by other alternative names) is a city in western Slovakia, situated at the foot of Zobor Mountain in the valley of the river Nitra. It is located 95 km east of Bratislava. With a population of about 78,353, it is the fifth ...
,
Slovakia Slovakia (; sk, Slovensko ), officially the Slovak Republic ( sk, Slovenská republika, links=no ), is a landlocked country in Central Europe. It is bordered by Poland to the north, Ukraine to the east, Hungary to the south, Austria to th ...
; a
limestone Limestone ( calcium carbonate ) is a type of carbonate sedimentary rock which is the main source of the material lime. It is composed mostly of the minerals calcite and aragonite, which are different crystal forms of . Limestone forms wh ...
quarry in
Dudley Dudley is a large market town and administrative centre in the county of West Midlands, England, southeast of Wolverhampton and northwest of Birmingham. Historically an exclave of Worcestershire, the town is the administrative centre of the ...
, England; and above an old
gypsum Gypsum is a soft sulfate mineral composed of calcium sulfate dihydrate, with the chemical formula . It is widely mined and is used as a fertilizer and as the main constituent in many forms of plaster, blackboard or sidewalk chalk, and drywa ...
mine in Magheracloone,
Ireland Ireland ( ; ga, Éire ; Ulster-Scots: ) is an island in the North Atlantic Ocean, in north-western Europe. It is separated from Great Britain to its east by the North Channel, the Irish Sea, and St George's Channel. Ireland is the s ...
.


Notable examples

Some of the largest sinkholes in the world are:


In Africa

*
Boesmansgat Boesmansgat, also known in English as "Bushman's Hole", is a deep submerged freshwater cave (or sinkhole) in the Northern Cape province of South Africa, which has been dived to a depth of . Boesmansgat was believed to have first been explored by ...
– South African freshwater sinkhole, approximately deep. * Lake Kashiba – Zambia. About 3.5 hectares (8.6 acres) in area and about deep.


In Asia

*
Blue Hole A blue hole is a large marine cavern or sinkhole, which is open to the surface and has developed in a bank or island composed of a carbonate bedrock ( limestone or coral reef). Their existence was discovered in the late 20th century by fisher ...
– Dahab, Egypt. A round sinkhole or blue hole, deep. It includes an archway leading out to the Red Sea at , which has been the site for many freediving and scuba attempts, the latter often fatal. * Akhayat sinkhole is in
Mersin Province Mersin Province ( tr, ), formerly İçel Province ( tr, ), is a province in southern Turkey, on the Mediterranean coast between Antalya and Adana. The provincial capital and the biggest city in the province is Mersin, which is composed of fo ...
, Turkey. Its dimensions are about in diameter with a maximum depth of . * Well of Barhout
Yemen Yemen (; ar, ٱلْيَمَن, al-Yaman), officially the Republic of Yemen,, ) is a country in Western Asia. It is situated on the southern end of the Arabian Peninsula, and borders Saudi Arabia to the north and Oman to the northeast and s ...
. A deep pit cave in Al-Mahara, Yemen. * Bimmah Sinkhole (Hawiyat Najm, the Falling Star Sinkhole, Dibab Sinkhole) – Oman, approximately deep. * The Baatara gorge sinkhole and the Baatara gorge waterfall next to
Tannourine Tannourine ( ar, تنورين, also Tannoureen, Tannorine) is a Lebanese town located in the Batroun District, part of the Governorate of North Lebanon, 80 km from the capital Beirut. Tannourine is formed by a cluster of mountain settlements ...
in
Lebanon Lebanon ( , ar, لُبْنَان, translit=lubnān, ), officially the Republic of Lebanon () or the Lebanese Republic, is a country in Western Asia. It is located between Syria to the north and east and Israel to the south, while Cyprus li ...
* Dashiwei Tiankeng in
Guangxi Guangxi (; ; alternately romanized as Kwanghsi; ; za, Gvangjsih, italics=yes), officially the Guangxi Zhuang Autonomous Region (GZAR), is an autonomous region of the People's Republic of China, located in South China and bordering Vietnam ...
, China, is deep, with vertical walls. At the bottom is an isolated patch of forest with rare species. *The
Dragon Hole Dragon Hole, also known as Yongle Blue Hole named after the third Ming emperor, is the deepest known blue hole in the world at deep. It is located about north of Drummond Island in the Paracel Islands. Blue holes generate a distinctive blue ...
, located south of the
Paracel Islands The Paracel Islands, also known as the Xisha Islands () and the Hoang Sa Archipelago ( vi, Quần đảo Hoàng Sa, lit=Yellow Sand Archipelago), are a disputed archipelago in the South China Sea. The archipelago includes about 130 small coral ...
, is the deepest known underwater ocean sinkhole in the world. It is deep. * Shaanxi tiankeng cluster, in the
Daba Mountains The Daba Mountains, also known by their Chinese name as the Dabashan, are a mountain range in Central China between the watersheds of the Yellow and Yangtze Rivers. Part of the larger Qinling mountain range, it cuts through four provinces: Si ...
of southern
Shaanxi Shaanxi (alternatively Shensi, see § Name) is a landlocked province of China. Officially part of Northwest China, it borders the province-level divisions of Shanxi (NE, E), Henan (E), Hubei (SE), Chongqing (S), Sichuan (SW), Gansu (W), Ningx ...
, China, covers an area of nearly 5019 square kilometers with the largest sinkhole being 520 meters in diameter and 320 meters deep. * Teiq Sinkhole (Taiq, Teeq, Tayq) in Oman is one of the largest sinkholes in the world by volume: . Several perennial
wadi Wadi ( ar, وَادِي, wādī), alternatively ''wād'' ( ar, وَاد), North African Arabic Oued, is the Arabic term traditionally referring to a valley. In some instances, it may refer to a wet (ephemeral) riverbed that contains water on ...
s fall with spectacular waterfalls into this deep sinkhole. * Xiaozhai Tiankeng
Chongqing Chongqing ( or ; ; Sichuanese pronunciation: , Standard Mandarin pronunciation: ), alternately romanized as Chungking (), is a municipality in Southwest China. The official abbreviation of the city, "" (), was approved by the State Cou ...
, China. Double nested sinkhole with vertical walls, deep.


In the Caribbean

* Dean's Blue Hole – Bahamas. The second deepest known sinkhole under the sea, depth . Popular location for world championships of free diving, as well as recreational diving.


In Central America

* Great Blue Hole – Belize. Spectacular, round sinkhole, deep. Unusual features are tilted stalactites in great depth, which mark the former orientation of limestone layers when this sinkhole was above sea level. * 2007 Guatemala City sinkhole * 2010 Guatemala City sinkhole


In Europe

*
Hranice Abyss Hranice Abyss ( cs, Hranická propast) is the deepest flooded pit cave in the world. It is a karst sinkhole near the town of Hranice, Czech Republic. The greatest confirmed depth is , of which is underwater. In 2020, a scientific expedition to ...
, in the
Moravia Moravia ( , also , ; cs, Morava ; german: link=yes, Mähren ; pl, Morawy ; szl, Morawa; la, Moravia) is a historical region in the east of the Czech Republic and one of three historical Czech lands, with Bohemia and Czech Silesia. The me ...
region of the Czech Republic, is the deepest known underwater cave in the world. The lowest confirmed depth (as of 27 September 2016) is 473 m (404 m below the water level). * Pozzo del Merro, near Rome, Italy. At the bottom of an conical pit, and approximately deep, it is among the deepest sinkholes in the world (see Sótano del Barro below). * Red Lake
Croatia , image_flag = Flag of Croatia.svg , image_coat = Coat of arms of Croatia.svg , anthem = "Lijepa naša domovino"("Our Beautiful Homeland") , image_map = , map_caption = , capit ...
. Approximately deep pit with nearly vertical walls, contains an approximately deep lake. * Gouffre de Padirac – France. It is 103 m (338 ft) deep, with a diameter of 33 metres (108 ft). Visitors descend 75 m via a lift or a staircase to a lake allowing a boat tour after entering into the cave system which contains a 55 km subterranean river. *
Vouliagmeni Vouliagmeni ( el, Βουλιαγμένη, meaning "sunken") is a seaside suburb and former municipality 20 km south of Athens city centre. Since the 2011 local government reform it is part of the municipality Vari-Voula-Vouliagmeni, of which ...
– Greece. The sinkhole of Vouliagmeni is known as "The Devil Well", because it is considered extremely dangerous. Four scuba divers have died in it. Maximum depth of and horizontal penetration of . * Pouldergaderry – Ireland. This sinkhole is located in the
townland A townland ( ga, baile fearainn; Ulster-Scots: ''toonlann'') is a small geographical division of land, historically and currently used in Ireland and in the Western Isles in Scotland, typically covering . The townland system is of Gaelic ori ...
of Kilderry South near Miltown, Co. Kerry at . The sinkhole, which is located in an area of karst bedrock, is approximately in diameter and deep with many mature trees growing on the floor of the hole. At the level of the surrounding ground, the sinkhole covers an area of approximately 1.3 acres. Its presence is indicated on
Ordnance Survey Ordnance Survey (OS) is the national mapping agency for Great Britain. The agency's name indicates its original military purpose (see ordnance and surveying), which was to map Scotland in the wake of the Jacobite rising of 1745. There was ...
maps dating back to 1829.


In North America


Mexico

*
Cave of Swallows The Cave of Swallows, also called the Cave of the Swallows ( es, Sótano de las Golondrinas), is an open-air pit cave in the municipality of Aquismón, San Luis Potosí, Mexico. The elliptical mouth, on a slope of karst, is 49 by 62 m wide ...
San Luis Potosí San Luis Potosí (), officially the Free and Sovereign State of San Luis Potosí ( es, Estado Libre y Soberano de San Luis Potosí), is one of the 32 states which compose the Federal Entities of Mexico. It is divided in 58 municipalities and i ...
. deep, round sinkhole with overhanging walls. * Puebla sinkhole – Santa Maria Zacatepec,
Puebla Puebla ( en, colony, settlement), officially Free and Sovereign State of Puebla ( es, Estado Libre y Soberano de Puebla), is one of the 32 states which comprise the Federal Entities of Mexico. It is divided into 217 municipalities and its cap ...
. diameter and deep, it is still growing . 2021. * Sima de las Cotorras
Chiapas Chiapas (; Tzotzil and Tzeltal: ''Chyapas'' ), officially the Free and Sovereign State of Chiapas ( es, Estado Libre y Soberano de Chiapas), is one of the states that make up the 32 federal entities of Mexico. It comprises 124 municipalities ...
. across, deep, with thousands of green parakeets and ancient rock paintings. *
Zacatón Zacatón is a cenote (a thermal water-filled sinkhole) belonging to the Zacatón system - a group of unusual karst features located in Aldama Municipality near the Sierra de Tamaulipas in the northeastern state of Tamaulipas, Mexico. It is the ...
Tamaulipas Tamaulipas (), officially the Free and Sovereign State of Tamaulipas ( es, Estado Libre y Soberano de Tamaulipas), is a state in the northeast region of Mexico; one of the 31 states which, along with Mexico City, comprise the 32 Federal Entiti ...
. Deepest water-filled sinkhole in world, deep.


United States

* Amberjack Hole – blue hole located off the coast of
Sarasota, Florida Sarasota () is a city in Sarasota County on the Gulf Coast of the U.S. state of Florida. The area is renowned for its cultural and environmental amenities, beaches, resorts, and the Sarasota School of Architecture. The city is located in the sou ...
. * Bayou Corne sinkholeAssumption Parish, Louisiana. About 25 acres in area and deep. * The Blue HoleSanta Rosa, New Mexico. The surface entrance is only 80 feet (24 m) in diameter, it expands to a diameter of 130 feet (40 m) at the bottom. * Daisetta SinkholesDaisetta, Texas. Several sinkholes have formed, the most recent in 2008 with a maximum diameter of and maximum depth of . * Devil's MillhopperGainesville, Florida. deep, wide. Twelve springs, some more visible than others, feed a pond at the bottom. * Golly Hole or December Giant – Calera, Alabama. Appeared 2 December 1972. Approximately by and deep. * Grassy CoveCumberland County, Tennessee. in area and deep, a
National Natural Landmark The National Natural Landmarks (NNL) Program recognizes and encourages the conservation of outstanding examples of the natural history of the United States. It is the only national natural areas program that identifies and recognizes the best e ...
. * Green Banana Hole – a blue hole located off the coast of
Sarasota, Florida Sarasota () is a city in Sarasota County on the Gulf Coast of the U.S. state of Florida. The area is renowned for its cultural and environmental amenities, beaches, resorts, and the Sarasota School of Architecture. The city is located in the sou ...
. * Gypsum Sinkhole – Utah, in
Capitol Reef National Park Capitol Reef National Park is an American national park in south-central Utah. The park is approximately long on its northsouth axis and just wide on average. The park was established in 1971 to preserve of desert landscape and is open all ye ...
. Nearly in diameter and approximately deep. *
Kingsley Lake Kingsley Lake is an almost perfectly circular lake of about in North East Florida, is located inside Clay County about east of Starke, Florida. According to some sources, it is the oldest and highest lake in Florida, located on the edge of th ...
Clay County, Florida. in area, deep and almost perfectly round. * Lake Peigneur
New Iberia New Iberia (french: La Nouvelle-Ibérie; es, Nueva Iberia) is the largest city in and parish seat of Iberia Parish in the U.S. state of Louisiana. The city of New Iberia is located approximately southeast of Lafayette, and forms part of the L ...
, Louisiana. Original depth , currently at Diamond Crystal Salt Mine collapse. * Winter Park SinkholeWinter Park, Florida. Appeared 8 May 1981. It was approximately wide and deep. It was notable as one of the largest recent sinkholes to form in the United States. It is now known as Lake Rose.


In Oceania

* Harwood Hole
Abel Tasman National Park Abel Tasman National Park is a New Zealand national park located between Golden Bay and Tasman Bay / Te Tai-o-Aorere at the north end of the South Island. It is named after Abel Tasman, who in 1642 became the first European explorer to sight N ...
, New Zealand. deep.


In South America

* Sima HumboldtBolívar, Venezuela. Largest sinkhole in sandstone, deep, with vertical walls. Unique, isolated forest on bottom. * In the western part of Cerro Duida, Venezuela, there is a complex of canyons with sinkholes. Deepest sinkhole is deep (from lowest rim within canyon); total depth .


See also

* * * * * * * * * * * * * * *


References

Bibliography *


External links


US Geological Survey Water Science School page about sinkholes

Video of Sinkhole forming in Texas
(8 May 2008) * Googl
map
of deepest "hole" for each state (Andy Martin)
Tennessee sinkholes
54,000+ sinkholes * {{Authority control Road hazards Dinaric karst formations Natural disasters