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The Red Lake sinkhole in Croatia

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 also known as shakeholes, and to openings where surface water enters into underground passages known as ponor, swallow hole or swallet.[1][2][3][4] A cenote is a type of sinkhole that exposes groundwater underneath.[4] Sink and stream sink are more general terms for sites which drain surface water, possibly by infiltration into sediment or crumbled rock.[2]

Most sinkholes are caused by karst processes – the chemical dissolution of carbonate rocks, collapse or suffosion processes.[1][5] Sinkholes are usually circular and vary in size from tens to hundreds of meters 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.[2][1]

Formation

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Sinkholes near the Dead Sea, formed when underground salt is dissolved by freshwater intrusion, due to continuing sea-level drop.
Collapse sinkhole in Chinchón, Spain.

Natural processes

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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.[6][7]

The formation of sinkholes involves natural processes of erosion[8] 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.[9] Sinkholes often form through the process of suffosion.[10] 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,[11] 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.[12]

Space and planetary bodies

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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.[13][14]

Artificial processes

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Main article: Pinge
A 32-foot-deep (9.8-meter) collapse formed by rainwater leaking through pavement and carrying soil into a ruptured sewer pipe in the parking lot at Georgia Tech in Atlanta, Georgia in 2005.

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, in the United States. 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.

Classification

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Solution sinkholes

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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.[15]

USGS dissolution sinkhole.
USGS dissolution sinkhole.

Cover-subsidence sinkholes

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Cover-subsidence sinkholes form where voids in the underlying limestone allow more settling of the soil to create larger surface depressions.[15]

USGS cover-subsidence sinkhole.
USGS cover-subsidence sinkhole.

Cover-collapse sinkholes

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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.[15]

USGS cover-subsidence sinkhole.
USGS cover-subsidence sinkhole.

Pseudokarst sinkholes

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Pseudokarst sinkholes resemble karst sinkholes but are formed by processes other than the natural dissolution of rock.[16]: 4 

Human-accelerated sinkholes

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Four panels illustrate the growth of soil cavities above a rock cavity. Rising water softens soil. Downward moving water carries softened soil down into rock cavity.
Man-made activities and land alterations that cause water-level fluctuations accelerate cover-collapse sinkholes

The U.S. Geological Survey 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."[15] 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.[17]: 2 [18][16]: 1 and 92  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.[19]: 52–53 

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.[17]: 26–29  The increased runoff from the impervious surfaces of roads, roofs, and parking lots also accelerate man-induced sinkhole collapses.[16]: 8 

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.[17]: 32–34  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".[20]: xii [16]: 17 and 104  The American Society of Civil Engineers 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.[19]: 88 

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.[21] Where large cavities exist in the limestone large surface collapses can occur, such the Winter Park, Florida sinkhole collapse.[16]: 91–92  Recommendations for land uses in karst areas should avoid or minimize alterations of the land surface and natural drainage.[17]: 36 

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.[19]: 88  In karst areas the traditional foundation evaluations (bearing capacity 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.[19]: 113  Since the soil/rock surface in karst areas are very irregular the number of subsurface samples (borings and core samples) required per unit area is usually much greater than in non-karst areas.[19]: 98–99 

More than three acres of trees are missing in a forest after collapsing into a funnel shaped pit with water at the bottom.
More than three acres of forest suddenly disappeared into this "December Giant" sinkhole in Montevallo, Alabama.

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.[22] The greatest amount of karst sinkhole damage in the United States occurs in Florida, Texas, Alabama, Missouri, Kentucky, Tennessee, and Pennsylvania.[23] 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 130 m (425 ft) long, 105 m (350 ft) wide and 45 m (150 ft) deep.[17]: 1–2 [19]: 61–63 [24]

Other areas of significant karst hazards include the Ebro Basin in northern Spain; the island of Sardinia; the Italian peninsula; the Chalk areas in southern England; Sichuan, China; Jamaica; France;[25]Croatia;[26] Bosnia and Herzegovina; Slovenia; and Russia, where one-third of the total land area is underlain by karst.[27]

Occurrence

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The entire surface water flow of the Alapaha River near Jennings, Florida goes into a sinkhole leading to the Floridan Aquifer groundwater
Gouffre de Padirac in France known since the 3rd c. and explored in 1889
A Floridian sinkhole in 2015

Sinkholes tend to occur in karst landscapes.[12] 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 rivers in these areas. Examples of karst landscapes with numerous massive sinkholes include Khammouan Mountains (Laos) and Mamo Plateau (Papua New Guinea).[28][29] The largest known sinkholes formed in sandstone are Sima Humboldt and Sima Martel in Venezuela.[29]

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 island in Papua New Guinea.[30] 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 662-metre-deep (2,172 ft) Xiaozhai Tiankeng (Chongqing, China), giant sótanos in Querétaro and San Luis Potosí states in Mexico and others.[29][31]

Unusual processes have formed the enormous sinkholes of Sistema Zacatón in Tamaulipas (Mexico), where more than 20 sinkholes and other karst formations have been shaped by volcanically heated, acidic groundwater.[32][33] This has produced not only the formation of the deepest water-filled sinkhole in the world—Zacatón—but also unique processes of travertine sedimentation in upper parts of sinkholes, leading to sealing of these sinkholes with travertine lids.[33]

The U.S. state of Florida 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.[34]

The Murge area in southern Italy also has numerous sinkholes. Sinkholes can be formed in retention ponds from large amounts of rain.[35]

On the Arctic seafloor, methane emissions have caused large sinkholes to form.[36][37]

Human uses

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Sinkholes have been used for centuries as disposal sites for various forms of waste. A consequence of this is the pollution of groundwater resources, with serious health implications in such areas.[38][39]

The Maya civilization sometimes used sinkholes in the Yucatán Peninsula (known as cenotes) as places to deposit precious items and human sacrifices.[40]

When sinkholes are very deep or connected to caves, they may offer challenges for experienced cavers or, when water-filled, divers. Some of the most spectacular are the Zacatón cenote in Mexico (the world's deepest water-filled sinkhole), the Boesmansgat sinkhole in South Africa, Sarisariñama tepuy in Venezuela, the Sótano del Barro in Mexico, and in the town of Mount Gambier, South Australia. Sinkholes that form in coral reefs and islands that collapse to enormous depths are known as blue holes and often become popular diving spots.[41]

Local names

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The Great Blue Hole near Ambergris Caye, Belize

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.[42]

  • Aven – In the south of France (this name means pit cave in the Occitan language).
  • Black holes (not to be confused with cosmic black holes) – 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 15 to 20 m (49 to 66 ft) depth; this layer "swallows" the light. Metabolism in the layer of microorganisms causes heating of the water. One of them is the Black Hole of Andros.[43]
  • Blue holes – This name was initially given to the deep underwater sinkholes of the Bahamas 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 can penetrate such depth and return after reflection.
  • Cenote – This refers to the characteristic water-filled sinkholes in the Yucatán Peninsula, Belize and some other regions. Some of the cenotes are developed above the rim of the Chicxulub crater and helped to identify its presence.
  • Dolina – Slovenian toponym internationally used for karst sinkholes. The original meaning is "valley" or "dale".[44]
  • Foiba – Friulan Italian dialect word (from the Latin fŏvea: "pit" or "chasm"). The name is given to sinkholes in the frontier zone between the Italian region of Friuli-Venezia Giulia, Croatia and Slovenia, in the Karst Plateau.
  • 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 250 m (820 ft), 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.[20]: 64 
  • Tomo – This term is used in New Zealand karst country to describe sinkholes.[45]
  • Vrtača, ponikva, dolac, dô – Croatian terms for sinkhole.[44][46]

Piping pseudokarst

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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 20 m (66 ft) wide and 30 m (98 ft) deep.[47] A similar hole had formed nearby in February 2007.[48][49][50]

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.[51][52] Instead, they are examples of "piping pseudokarst", created by the collapse of large cavities that had developed in the weak, crumbly Quaternary 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 mains 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.[51]

Crown hole

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A crown hole is subsidence due to subterranean human activity, such as mining and military trenches.[53][54] Examples have included, instances above World War I trenches in Ypres, Belgium; near mines in Nitra, Slovakia;[55] a limestone quarry in Dudley, England;[55][56] and above an old gypsum mine in Magheracloone, Ireland.[54]

Notable examples

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Further information: List of sinkholes
Bimmah or Falling Star Sinkhole in Oman

Some of the largest sinkholes in the world are:[29]

Africa

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  • Boesmansgat – South African freshwater sinkhole, approximately 290 m (950 ft) deep.[57]
  • Lake Kashiba – Zambia. About 3.5 hectares (8.6 acres) in area and about 100 m (330 ft) deep.
  • Blue Hole – Dahab, Egypt. A round sinkhole or blue hole, 130 m (430 ft) deep. It includes an archway leading out to the Red Sea at 60 m (200 ft), which has been the site for many freediving and scuba attempts, the latter often fatal.[58]

Asia

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Caribbean

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  • Dean's Blue Hole – Bahamas. The second deepest known sinkhole under the sea, depth 203 m (666 ft). Popular location for world championships of free diving, as well as recreational diving.

Central America

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Europe

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  • Hranice Abyss, in the Moravia 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).
  • Maqluba, in Malta is a sinkhole with a surface area of around 4,765 square metres (51,290 sq ft) situated in the village of Qrendi in Malta. The diameter is around 50m, the depth is around 15m, and the perimeter 300m.
  • Pozzo del Merro, near Rome, Italy. At the bottom of an 80 m (260 ft) conical pit, and approximately 400 m (1,300 ft) deep, it is among the deepest sinkholes in the world (see Sótano del Barro below).[citation needed]
  • Red Lake – Croatia. Approximately 530 m (1,740 ft) deep pit with nearly vertical walls, contains an approximately 280–290 m (920–950 ft) deep lake.
  • Gouffre de Padirac – France. It is 103 m (338 ft) deep, with a diameter of 33 metres (108 feet). 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 – Greece. The sinkhole of Vouliagmeni is known as "The Devil Well",[citation needed] because it is considered extremely dangerous. Four scuba divers have died in it.[68] Maximum depth of 35.2 m (115 ft 6 in) and horizontal penetration of 150 m (490 ft).
  • Pouldergaderry – Ireland. This sinkhole is located in the townland of Kilderry South near Milltown, County Kerry at 52°7′57.5″N 9°44′45.4″W / 52.132639°N 9.745944°W / 52.132639; -9.745944.[69][citation needed] The sinkhole, which is located in an area of karst bedrock, is approximately 80 metres (260 ft) in diameter and 30 metres (98 ft) 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 maps dating back to 1829.[70]

North America

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Mexico

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United States

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Oceania

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South America

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  • Sima Humboldt – Bolívar, Venezuela. Largest sinkhole in sandstone, 314 m (1,030 ft) 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 450 m (1,480 ft) deep (from lowest rim within canyon); total depth 950 m (3,120 ft).

See also

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References

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[edit]
Revisions and contributorsEdit on WikipediaRead on Wikipedia

Sinkhole

View on Grokipedia
from Grokipedia
A sinkhole is a depression or hole in the ground caused by the of surface material into an underlying void, typically formed through the dissolution of soluble by or other erosional processes. These geological features lack natural external drainage, allowing rainwater to infiltrate directly into the subsurface rather than flowing away, and they vary in from small depressions a few meters across to large chasms exceeding hundreds of meters in diameter and depth. Although most common in landscapes, where soluble rocks such as , dolomite, or underlie the surface and are gradually eroded by acidic , creating underground cavities that eventually lead to surface or sudden , sinkholes can also form through non-karst processes such as or human activities. Sinkholes form through two primary mechanisms: natural dissolution and human-induced activities. In natural processes, percolating rainwater, slightly acidified by atmospheric , dissolves minerals in the over thousands of years, enlarging fractures into caves and voids that destabilize the overlying and rock. Human factors, including groundwater pumping, , , and leaking , can accelerate this by lowering water tables or removing support, triggering collapses in vulnerable areas. There are three main types of sinkholes: solution sinkholes, which develop slowly through direct chemical of exposed , often appearing as shallow, bowl-shaped hollows; cover-subsidence sinkholes, characterized by gradual settling of unconsolidated cover material like or sand over enlarging voids; and cover-collapse sinkholes, which form abruptly when a structural in the overlying causes catastrophic , potentially within hours. A fourth category, suffosion or sinkholes, arises from the downward migration of fine particles into fissures without significant rock dissolution. Globally, sinkholes pose significant hazards in regions underlain by soluble formations, with terrain covering approximately 10–15% of the Earth's ice-free land surface, including extensive areas in the United States (such as and , where about 20% of the land is susceptible), , the Mediterranean basin, and parts of the like the and Mendips. They can endanger , , and human life, with sudden collapses damaging roads, buildings, and utilities, while gradual leads to environmental changes like altered and loss. Monitoring and mitigation efforts, including geophysical surveys and land-use regulations, are essential in high-risk zones to predict and prevent these events.

Introduction

Definition and Characteristics

A sinkhole is a depression in the ground that has no natural external surface drainage, meaning that rainwater collects within the depression and typically drains into the subsurface rather than flowing away over the surface. This feature arises from the collapse or subsidence of surface material into an underlying void, often resulting in a closed topographic low. Sinkholes are commonly associated with soluble such as or , where the ground surface exhibits these depressions as a primary . Physically, sinkholes may form suddenly through catastrophic collapse or gradually via soil piping and , leading to steep or vertical walls in some cases and more gradual slopes in others. They can develop flat bottoms if accumulates or fill with to create or lakes, enhancing their role as internal drainage basins. The presence of such water bodies underscores their hydrological characteristics, where subsurface flow predominates over . In terms of scale and morphology, sinkholes typically appear circular or elliptical, with diameters ranging from less than 1 meter to over 600 meters and depths from a few centimeters to more than 100 meters. Their shapes vary widely, including bowl-like, saucer-shaped, conical, funnel-like, or cylindrical forms, depending on the subsurface structure and material properties. These dimensions and configurations distinguish sinkholes as versatile geomorphic features that can span small localized depressions to expansive voids. Sinkholes differ from similar surface features like potholes, which are shallow erosional depressions confined to the uppermost soil or pavement layers without subsurface voids, and impact craters, which originate from extraterrestrial collisions and display shocked minerals or raised rims absent in sinkholes.

Significance and Impacts

Sinkholes pose significant risks to human life and infrastructure due to their potential for sudden and catastrophic collapses. While fatalities and injuries are relatively rare, they can occur when structures or vehicles are engulfed without warning; for example, in 2013, a man in Seffner, Florida, was killed when a sinkhole opened beneath his bedroom, swallowing him entirely. Such events have also led to injuries, as seen in 2011 when a teenager in Utah died after her family's vehicle fell into a sinkhole. Infrastructure damage is more common, with sinkholes frequently undermining roads, bridges, and buildings, particularly in karst-prone regions like Florida, Texas, Alabama, Missouri, Kentucky, Tennessee, and Pennsylvania, where the majority of U.S. incidents cause structural failures. Although comprehensive national or global databases are lacking, state-level tracking indicates hundreds to thousands of reported sinkholes annually in the United States alone, with many more unreported small events. Environmentally, sinkholes disrupt aquifers and hydrological systems by creating direct pathways for unfiltered surface water to enter , potentially introducing contaminants and pollutants that compromise . They also lead to soil loss and vegetation destruction through collapse, altering local ecosystems and reducing in affected areas. In regions, these formations can change levels, exacerbating flooding in low-lying areas or contributing to droughts by accelerating drainage, thereby unbalancing natural recharge processes. The economic burden of sinkholes is substantial, with repair and mitigation costs averaging at least $300 million annually (over the last 15 years as of 2020), covering damages to homes, utilities, and transportation networks. Worldwide, these impacts escalate to billions of dollars each year, straining systems—where the number of human-induced sinkholes has doubled since and claims for sinkhole-related damages increased by 1,200% from 1987 to 1991— and complicating and agriculture in vulnerable zones. Awareness of sinkholes dates back to ancient times, with early records possibly referencing them in biblical accounts of the Dead Sea region, such as the "slime pits" near around 2000 BCE. Modern understanding has evolved through geological surveys and monitoring programs established in the , including U.S. Geological Survey efforts since the to map risks. Recent studies highlight an increase in frequency linked to , as heavier rainfall and prolonged droughts accelerate rock dissolution and overburden instability.

Formation

Natural Processes

Sinkholes form naturally through a combination of chemical and mechanical processes that erode subsurface materials, leading to voids and eventual surface collapse. The primary chemical mechanism, known as karstification, involves the dissolution of soluble such as and dolomite by slightly acidic . Rainwater absorbs from the atmosphere and soil, forming (H₂CO₃), which reacts with (CaCO₃) in the bedrock according to the equation: \ceCaCO3+H2CO3−>Ca(HCO3)2\ce{CaCO3 + H2CO3 -> Ca(HCO3)2} This reaction produces , a soluble compound that is carried away by flowing , gradually enlarging fractures and creating underground cavities. Over time, these voids weaken the overlying and rock layers, resulting in sudden or progressive collapse to form a sinkhole. In addition to chemical dissolution, mechanical processes contribute to sinkhole development, particularly in non-soluble substrates like , clay, or unconsolidated sediments. Soil piping, a key mechanical action, occurs when erodes fine particles through pores or cracks, transporting them downward and leaving larger grains behind to form voids. This suffosion process, also termed mechanical relocation, is prevalent in granular aquifers where slow water movement facilitates particle suspension and removal without dissolution. Gravitational settling and sediment washing into subsurface fissures further exacerbate instability, allowing the surface to subside into the emptied spaces. The time scales of natural sinkhole formation vary widely, from gradual development over millennia to rapid collapses occurring in days or even minutes. dissolution typically progresses slowly, with voids enlarging over thousands to millions of years in stable terrains, influenced by factors such as rainfall intensity, which accelerates during heavy events; , where steeper slopes promote faster drainage and weakening; and vegetation cover, which stabilizes but can concentrate water flow in root channels. In contrast, mechanical piping or salt dissolution in evaporite rocks can lead to quicker , with laboratory models showing complete void formation in hours under high-flow conditions, though field-scale events in natural settings often span years to decades due to variable . Hydrological factors play a crucial role in directing these processes, as aquifers and enlarged conduits channel water preferentially through the subsurface, enhancing dissolution and erosion rates. In systems, circulates through solution-enlarged fractures and caves, lowering buoyant support for overlying sediments and promoting when water levels fluctuate. Conduits formed by initial dissolution act as drainage pathways, concentrating flow and accelerating the transport of dissolved materials or eroded particles away from the site, thereby weakening surface layers over time.

Extraterrestrial Formation

Sinkhole-like features have been observed on Mars, particularly in the planet's polar regions, where collapse pits known as the "Swiss cheese terrain" form in the south polar layered deposits. These depressions, imaged by NASA's (MRO), result from the sublimation of (CO₂) ice slabs overlying voids created by seasonal gas pressure buildup and release. Diameters of these pits can reach up to 100 meters, with depths of several meters, and they expand over time due to ongoing sublimation processes during Martian spring. Beyond the poles, karst-like sinkholes on Mars are interpreted as collapses from the dissolution of ancient deposits, such as and , in regions with evidence of past water flow. These features, larger on average than terrestrial counterparts due to Mars' lower (about 38% of Earth's), appear in outflow channels like Kasei Valles and NE , suggesting widespread subsurface voids formed in a low-pH environment influenced by high atmospheric CO₂ levels. On the , pit craters represent collapse features associated with ancient s, providing skylights into subsurface voids. NASA's (LRO) has identified over 200 such pits, with diameters ranging from 10 to 300 meters and depths up to 100 meters, often in mare basalts like . These form when the roof of a solidified collapses, exposing , cave-like interiors shielded from radiation. Asteroid Vesta exhibits pitted terrains in fresh impact craters, such as Marcia Crater, observed by NASA's Dawn spacecraft. These clusters of rimless depressions, typically tens of meters across, arise from the post-impact degassing of volatiles like water vapor trapped in the subsurface, leading to localized collapses. On dwarf planet Ceres, pit chains and isolated depressions, such as those in Samhain Catenae, indicate subsurface voids possibly linked to cryovolcanism or fracturing. Dawn mission images reveal these features, up to several kilometers long, formed by the mobilization of briny fluids or ice sublimation in impact-related settings. Formation mechanisms for these extraterrestrial features draw analogies to terrestrial sinkholes but are adapted to unique planetary conditions. On Mars, dissolution akin to Earth's processes may have occurred via acidic fluids in ancient water-rich environments, evidenced by remnants, while thermal contraction cracks in icy create voids prone to collapse. Lunar pits parallel volcanic collapses on Earth, but lower gravity allows larger tube dimensions. Volatiles on Vesta and Ceres suggest cryovolcanic or impact-induced degassing, contrasting with Earth's water-driven erosion; the absence of atmospheres accelerates sublimation, and reduced gravity enlarges feature scales compared to terrestrial equivalents. These features offer key insights into and resource potential. On Mars, polar pits and collapses signal past liquid water and preserved ice deposits, potentially hosting subsurface niches for microbial life beneath protective ice layers. Such volatiles are critical for human exploration, providing accessible water ice for fuel and life support in mid-latitude regions. On the and asteroids, pit access to stable voids informs strategies for shielded habitats, while Ceres' cryovolcanic pits highlight subsurface brines as analogs for ocean worlds' .

Classification

Karst-related sinkholes arise from the chemical dissolution of soluble bedrock, primarily and dolomite, which creates subsurface voids that eventually lead to surface depressions or collapses. This process is most active in areas where slightly acidic , derived from rainfall and soil CO2, erodes the rock over geological timescales. Unlike other formations, these sinkholes are intrinsically linked to topography, characterized by irregular drainage and landforms resulting from long-term rock . Karst processes also occur in rocks such as and , which are highly soluble and can lead to more rapid formation of sinkholes compared to carbonates. Solution sinkholes develop through the direct dissolution of surface or near-surface , typically in exposed layers without significant . These form gradually over thousands of years, producing broad, bowl-shaped depressions that can reach diameters of several meters and depths up to 10-20 meters, often enlarging progressively with continued exposure to percolating water. They are common in regions with bare or thinly covered outcrops, where rainfall directly contacts the soluble rock. Cover-subsidence sinkholes occur when unconsolidated overlying sediments, such as sand, clay, or soil, slowly settle into enlarged fissures or voids developed within the underlying . This gradual process, spanning months to years, results in shallower, funnel-shaped depressions that widen at the top, typically less than 15 meters deep, as the cover material compacts or migrates downward without abrupt failure. In contrast, cover-collapse sinkholes form suddenly when the roof of a subsurface cavity fails, causing the overlying insoluble sediments to drop into the void below. These events can happen over hours or days, producing steep-walled, circular holes that may exceed 30 meters in depth and pose immediate hazards due to their violent onset. The collapse often follows prolonged void enlargement from dissolution, leading to structural instability in the sediment cap. Evaporite sinkholes in salt domes involve dissolution of highly soluble evaporites like in tectonically uplifted structures, differing from slower carbonate processes by their extreme rapidity. These occur when unsaturated accesses salt layers, dissolving them to form cavities that collapse, as seen in the Permian Basin of and , where sinkholes up to 200 meters wide have formed over salt domes in mere days, displacing volumes like 23,000 cubic meters in a 1918 event. Their faster evolution—gypsum dissolves 150 times faster than , salt 7,500 times—results in unpredictable, often catastrophic collapses, setting them apart from the gradual, more stable topography in . Diagnostic features of -related sinkholes include their close association with other karst landforms, such as caves, springs, and disappearing streams, where rapidly infiltrates underground through swallow holes or fissures. These sinkholes are prevalent in tropical and subtropical climates with high annual rainfall exceeding 1,000 mm, which accelerates dissolution by providing abundant acidic recharge water.

Non-Karst Sinkholes

Non-karst sinkholes, often referred to as pseudokarst sinkholes, develop in insoluble rocks or unconsolidated sediments through mechanical erosion, , or other non-dissolutional processes, mimicking the appearance of features but without chemical solubilization of bedrock. These formations occur in substrates such as , glacial deposits, cohesive soils, evaporites in specific contexts, or tectonically deformed terrains, where physical forces like flow, , or structural deformation dominate. Unlike sinkholes, which form slowly over millennia through dissolution of carbonates, non-karst variants typically emerge more rapidly—sometimes in years or decades—leading to less predictable and often irregular shapes, such as linear or elongated depressions rather than the classic circular dolines. Pseudokarst sinkholes in volcanic terrains arise primarily from the collapse of subsurface voids in flows or lava tubes, where molten lava drains away, leaving hollow channels that later roof in and fail under surface load. These features are common in regions with ancient effusive volcanism, such as the of the , where lava tubes in the create open sinkholes and fissures upon collapse, sometimes reaching depths of tens of meters. For instance, in Hawaii's volcanic landscapes, sinkholes form when roofs of drained lava tubes subside, producing irregular pits that can exceed 10 meters in diameter, distinct from dissolution-driven by their association with cooling and flow dynamics rather than water chemistry. In glacial environments, pseudokarst sinkholes develop through suffosion or mechanical erosion in tills and outwash deposits, where removes fine sediments from beneath coarser layers, causing surface without dissolution. Examples include the pockmarked suffosion sinkholes on Malham Moor in England's glacial tills, ranging from 1 to 15 meters across, formed by downward piping of clay and into underlying voids created by ice retreat. These differ from by their dependence on periglacial processes and unconsolidated materials, often resulting in shallower, more clustered depressions that evolve over centuries rather than eons. Piping pseudokarst sinkholes form in cohesive soils like or through subsurface , where concentrated water flow initiates tunnels (pipes) that enlarge via headward —undercutting and backward extension—eventually leading to roof collapse and surface pits. This process is prevalent in or semi-arid alluvial plains, such as the Goodwin Creek watershed in , where flute holes associated with sinkholes average 8.5 cm in diameter and develop from pipe failures in loess pastures, or in the Czech Republic's loess-derived soils at Halenkovice, where interconnected pipe networks cause rapid up to several meters deep. In contrast to , piping sinkholes form quickly in non-soluble sediments, often linearly along buried channels, with high susceptibility to triggers like heavy rainfall. Tectonic pseudokarst sinkholes emerge from faulting or structural deformation in non-soluble rocks, where fracturing facilitates or along fault planes, producing linear depressions without dissolution. Such features, akin to fault-guided collapses, appear in tectonically active areas like California's zone, where pseudokarst-like sinkholes form from slumping into fault voids, though they are less common and often elongated compared to the rounded forms. This mechanical origin emphasizes brittle failure over chemical , contributing to their sporadic and hazard-prone nature.

Occurrence and Distribution

Geological Settings

Sinkholes primarily develop in geological settings characterized by the presence of soluble rocks, such as , dolomite, , and salt deposits, which are evaporites that readily dissolve in water. These rocks form aquifers with high permeability, allowing to infiltrate and chemically erode the subsurface over time, creating voids that lead to surface collapses. Unconsolidated sediments overlying these soluble layers can also contribute to sinkhole formation by filling voids and eventually subsiding. Hydrological factors play a crucial role, including high rates that promote dissolution through conduit networks and seasonal flooding that enhances water circulation. The epikarst, a weathered surface zone of fractured and pitted typically 5-15 meters thick, facilitates rapid infiltration and lateral water movement, concentrating flow into fissures and accelerating void enlargement. This zone acts as a near-surface , with ranging from 1% to 10%, enabling quick recharge—up to 84% of spring discharge during storms can originate from epikarst flow—thus priming the system for sinkhole development. Tectonic influences further condition sinkhole-prone environments by exposing soluble layers through uplift and faulting, which create pathways for migration. Fault lines, such as normal and strike-slip faults, structurally control sinkhole distribution by fracturing and promoting fluid that dissolves evaporites at depths up to 2,000 meters. Seismic activity, including low-magnitude earthquakes (M_L ≤ 2) associated with fault creep, can trigger collapses by inducing fracturing and altering subsurface stress, as observed in , where about 40% of documented sinkholes occur near hazardous faults. Climate dependencies significantly modulate these processes, with humid environments accelerating dissolution due to abundant and optimal flow velocities that maximize chemical reactions in moisture-limited early stages of evolution. In contrast, arid to semi-arid settings favor development, where sparse vegetation exposes and salt layers to episodic intrusion, leading to rapid sinkhole formation—sometimes in days—despite lower overall , as seen in regions like the Permian Basin.

Regional Variations

Sinkholes exhibit significant regional variations influenced by local geology, climate, and hydrology, with terrains covering approximately 10% of Earth's land surface and posing risks to over a quarter of the global population through dependency. These variations manifest in diverse formation types and densities, from dissolution-driven collapses in carbonate-rich areas to in and volcanic settings. High-risk zones include in the United States, where cover-subsidence sinkholes predominate in aquifers due to gradual soil piping over underlying voids. In China's region, tower landscapes feature massive sinkholes, or tiankeng, formed by deep dissolution in soluble carbonates, with over 30 such giant depressions documented in clusters. The Dead Sea area exemplifies -driven collapses, where rapid dissolution of underlying salt layers by undersaturated has produced thousands of sinkholes since the 1980s, accelerating due to declining lake levels. Continental patterns further highlight these differences: hosts extensive classical systems, particularly in Slovenia's region, where dense networks of sinkholes, caves, and poljes result from long-term dissolution in a humid temperate climate. In the Americas, volcanic pseudokarst dominates in , where lava tube collapses and fracture-enlarged voids mimic karst sinkholes without chemical dissolution, posing hazards in basaltic terrains. The features arid salt karst, as seen in the Jahani salt extrusion in , where hypersaline and tectonic stresses drive sinkhole formation in evaporite domes, with over 6,000 depressions mapped in a single namakier. Human factors amplify vulnerabilities in these regions; for instance, high population density in Mexico City's urban expanse exacerbates sinkhole risks through overexploitation of aquifers, leading to subsidence and collapse in compressible clay soils overlying volcanic tuff. Climate change trends, such as intensified monsoons in Asia, increase sinkhole incidence by enhancing surface water infiltration and erosion in karst-prone areas like southern China and India. Globally, geographic information systems (GIS) and remote sensing enable density mapping, revealing that karst and pseudokarst cover vast areas susceptible to sinkholes, with tools like LiDAR identifying closed depressions across continents for hazard assessment.

Human Interactions

Induced and Accelerated Sinkholes

Human activities can directly induce sinkhole formation or accelerate natural processes by altering subsurface , structural integrity, and dissolution rates. Common anthropogenic triggers include excessive extraction, underground mining, and urban infrastructure failures, which often lead to sudden collapses in vulnerable geological settings. These induced sinkholes differ from natural ones by their rapid onset and association with modifiable human practices. Overpumping of aquifers lowers water tables, removing buoyant support from overlying sediments and accelerating the dissolution of underlying soluble rocks. In , where terrain is prevalent, increased withdrawal for and urban use has correlated with a surge in sinkhole incidents; insurance claims related to sinkholes rose from approximately 2,360 in 2006 to over 7,245 in 2009, reflecting a more than 200% increase in reported collapses during that period. This trend has been exacerbated by population growth and development, with total damages exceeding $1.4 billion between 2006 and 2010. Similar patterns occur globally where intensive pumping destabilizes aquifers, such as in parts of the Dead Sea region, where water diversion has induced thousands of sinkholes since the . Underground mining creates voids that eventually collapse under surface loads, forming sinkholes long after extraction ceases. In evaporite deposits, such as salt beds, solution mining dissolves rock to produce , leaving cavities up to 100 meters in diameter that propagate upward through roof failures, resulting in surface depressions. Notable examples include the 1974 Cargill sinkhole in , a 90-meter-wide over a century-old salt mine, and the 1980 Jefferson Island event in , where a 400-meter-deep salt dome mine failure drained an entire lake. Coal mining similarly induces subsidence through pillar and groundwater infiltration into abandoned workings, as seen in , where dewatering for mines triggered over 100 sinkholes in the late . Urban development introduces additional risks through leaking infrastructure and surface disturbances that erode subsurface stability. Burst sewer lines and water mains direct concentrated flows into unconsolidated deposits, promoting piping and cavity enlargement; for instance, in Allentown, Pennsylvania, pipe leaks have caused multiple collapses by saturating and eroding underlying materials. Heavy construction vibrations and loading from buildings can fracture cavity roofs, while improper waste disposal, such as sewage impoundments, adds weight and moisture to accelerate dissolution. These factors often amplify natural processes, with human influences speeding up erosion by orders of magnitude through increased water velocity and chemical saturation. Anthropogenic sinkholes have risen in frequency, comprising the majority of damaging incidents worldwide due to expanding and resource extraction. In the United States, annual economic losses from such events amount to at least $300 million per year over the last 15 years, driven by vulnerabilities. A prominent case is the , a 20-meter-wide, 90-meter-deep chasm formed when tropical storm rains overwhelmed a clogged sewer system, eroding volcanic deposits; Samuel Bonis attributed it to burst pipes and poor maintenance rather than natural , highlighting recurring issues from a 2007 similar collapse in the same area. Recent studies indicate that human activities now trigger the vast majority of hazardous sinkholes, with global reports increasing alongside climate-amplified extremes like droughts that lower water tables further.

Detection, Prevention, and Mitigation

Detection of sinkholes often relies on geophysical surveys to identify subsurface voids and weaknesses before surface collapse occurs. Ground-penetrating radar (GPR) is a non-invasive technique that uses electromagnetic waves to image shallow subsurface features, effectively mapping potential sinkholes by detecting anomalies in soil and rock layers up to several meters deep. Electrical resistivity tomography (ERT) measures variations in soil resistivity to delineate low-resistivity zones indicative of water-filled cavities or clay-filled voids associated with karst features. Microgravity surveys detect subtle density contrasts caused by underground voids, providing a cost-effective method for delineating sinkhole-prone areas over larger scales by identifying negative gravity anomalies. These methods are frequently integrated for comprehensive site assessments in karst terrains. Surface monitoring has been enhanced by drone-based , which generates high-resolution digital elevation models to detect subtle topographic depressions signaling incipient sinkhole formation. Unmanned aerial vehicles (UAVs) equipped with sensors can penetrate vegetation cover and map features like dolines with centimeter-level accuracy, enabling early identification in inaccessible or urbanized areas. Prevention strategies in sinkhole-prone regions emphasize stabilizing subsurface conditions and controlling environmental stressors. Grouting involves injecting cementitious or chemical materials into fissures and voids to fill cavities and reinforce , a common remedial measure in areas to avert collapses during construction. Regulated extraction is critical, as excessive pumping lowers water tables and accelerates dissolution in soluble rocks; practices, such as permitting limits and monitoring wells, help maintain hydrostatic support in aquifers. Land-use restricts development in high-risk zones, directing urban expansion away from unstable terrains through ordinances that mandate geotechnical evaluations and prohibit high-density building in susceptible areas. Post-event mitigation focuses on stabilizing affected sites and restoring functionality through engineering interventions. Foam injection, using expandable polyurethane, fills voids and compacts surrounding soils to support structures, offering a minimally invasive repair for small to medium sinkholes. Bridging techniques employ plugs or micropiles to span cavities, preventing further while allowing drainage in utility corridors. Insurance and policy frameworks provide financial safeguards; for instance, Florida's Sinkhole Statute, updated in 2023, requires insurers to offer limited sinkhole coverage and mandates standardized testing protocols for claims, ensuring equitable resolution of disputes. Emerging technologies leverage for predictive modeling, integrating satellite data to forecast sinkhole risks with improved precision. AI algorithms trained on multispectral imagery achieve high detection accuracy, with F1 scores exceeding 97% for automatic sinkhole recognition, enabling early warnings by analyzing surface deformation patterns over vast areas. These models, combined with (SAR) from satellites like , monitor at millimeter resolution, supporting proactive hazard mapping in regions.

Exploitation and Cultural Aspects

Human Uses

Humans have long exploited sinkholes for resource extraction in karst regions, where these formations often expose accessible deposits of soluble rock. Limestone quarrying frequently targets the walls and floors of existing sinkholes, facilitating the removal of high-quality stone for construction aggregates and cement production without extensive removal. In areas like the in , small sinkholes function as natural depressions that pond rainwater, serving as localized reservoirs for collection and storage, particularly beneficial in semi-arid karst environments with limited . Similarly, cenotes in the have historically provided essential access, with communities lining their edges to capture and manage water inflows during dry seasons. Sinkholes also hold significant recreational and cultural value, transforming geological features into sites of human engagement. In the , scenic sinkholes known as cenotes draw millions of tourists annually for , , and , owing to their crystal-clear, subterranean waters that reveal intricate cave systems and biodiversity. These activities support local economies through , such as guided tours and access platforms, while emphasizing conservation to preserve water quality. Culturally, ancient Maya civilizations revered cenotes as sacred portals to the underworld (), conducting rituals including offerings of jade, gold, and human sacrifices to invoke rain gods like . The at , for instance, yielded over 200 human remains and artifacts from such ceremonies spanning the Classic to Postclassic periods. Agriculturally, sinkhole basins in landscapes offer fertile micro-environments amid otherwise unproductive rocky terrain, as and sediment trapping create deeper soils enriched with and moisture retention. In Mediterranean areas like , farmers adapt these depressions (dolines) for cultivating olives, grapes, and cereals, utilizing the basins' ability to collect runoff and support in water-scarce settings. Such practices enhance productivity in marginal lands, though they require careful management to avoid contaminating underlying aquifers with fertilizers or waste. While these uses provide socioeconomic benefits, they can exacerbate , such as accelerated or of systems.

Local Names and Terminology

Sinkholes are known by a variety of regional terms that reflect local geological contexts, cultural histories, and linguistic traditions, highlighting the global diversity of landscapes. In Mexico's , the term "" refers to deep, water-filled sinkholes formed by the collapse of cave roofs, often extending below the with steep walls; derived from the Yucatec Maya word ts'onot meaning "sacred well" or "hole filled with water," these features held spiritual significance for the Maya as portals to the . In , particularly in the subtropical regions of and , "tiankeng" denotes exceptionally large sinkholes exceeding 100 meters in both depth and width, characterized by steep walls and often containing ancient forests or underground rivers; the term, coined in 2001 by Zhu Xuewen, combines Chinese characters tian ("heaven") and keng ("pit"), evoking their dramatic scale, as exemplified by the , the world's deepest known at over 660 meters. In , "doline" is a widely used term for closed, funnel- or basin-shaped depressions in , ranging from 1 meter to 1 kilometer wide and formed by solution or collapse processes; originating from Slavic roots such as dol ("valley") or Slovenian dolina ("valley"), it entered international nomenclature through early studies in the . Additional terms include "swallow hole," prevalent in the United Kingdom and Australia for points where surface streams vanish into the ground, often synonymous with "swallet" and describing closed depressions that "swallow" water flows in karst terrains like the Yorkshire Dales or Nullarbor Plain. In the Balkans, "uvala" designates compound sinkholes resulting from the coalescence of multiple smaller dolines, forming larger closed depressions along tectonic zones; derived from South Slavic uvala meaning "hollow" or "depression," it is tied to the regional geology of the Dinaric Karst in areas like and Bosnia. Similarly, "polje" applies to vast, flat-bottomed fields in and surrounding regions, such as the Livanjsko Polje, where sinkholes integrate into arable plains bounded by steep walls; from polje ("field"), the term evolved to describe these agriculturally vital features shaped by episodic flooding and dissolution. These terms often evolve in tandem with local geology and human adaptation: for instance, "polje" in Croatian contexts emphasizes flat, cultivable surfaces riddled with sinkholes, contrasting with the more vertical "cenote" in the horizontal limestone platforms of , or the cavernous "tiankeng" in China's tower , where depth fosters isolated ecosystems. To address this terminological diversity, the International Union of Speleology (UIS) coordinates global standardization through its multilingual and Glossary, first compiled in the early 2000s and updated as of 2023 to unify definitions across languages, promoting consistent usage in research while preserving regional nuances like those for doline and uvala.

Notable Examples

Africa and Middle East

In the Bayuda Desert of , volcanic pseudokarst sinkholes form due to the collapse of ancient lava tubes within the basalt flows of the Bayuda Volcanic Field, a monogenetic volcanic area covering approximately 480 square kilometers. These collapses occur when the roofs of lava tubes, formed from homogeneous during volcanic activity, fail under the weight of overlying material, creating depressions that can reach widths of up to 200 meters. Such features highlight the geological uniqueness of pseudokarst processes in arid volcanic terrains, distinct from typical dissolution-based . The Dead Sea region, shared by and , has experienced a dramatic proliferation of sinkholes since the 1980s, with over 7,000 documented along its shores as of 2022 and formation continuing into 2025, driven primarily by the dissolution of underlying salt layers exposed by the lake's declining levels. The Dead Sea's surface has dropped more than 40 meters since the due to upstream diversions and , allowing undersaturated to infiltrate and dissolve the salt at depths of 20–50 meters, leading to and . Formation rates accelerated sharply after 2000, reaching 150–200 new sinkholes per year in recent decades, with a peak of around 700 in 2015 alone; ongoing hydrological changes as of 2025 continue to exacerbate the hazard, rendering coastal areas increasingly unstable. The in northern represents one of the world's largest sinkhole basins, spanning about 19,000 square kilometers and reaching depths of up to 133 meters below , formed through millennia of salt and that carved out the underlying sedimentary layers. This vast, sludgy feature, comparable in size to , exposes a rich in evaporites, contributing to its sinkhole-like morphology in an arid environment. Proposals for its exploitation include channeling Mediterranean via a 55–100 kilometer to create a , generating hydroelectric power through continuous inflow and , while a related concept involves desalinating diverted to enable agricultural cultivation in the surrounding desert. In , the ongoing conflict has compounded vulnerabilities to sinkhole events, underscoring the risks in -prone terrains amid infrastructural neglect.

Americas

In , sinkholes are prominent in urban and environments, often exacerbated by heavy rainfall and infrastructure issues. The exemplifies this, forming a cavity approximately 18 meters wide and 100 meters deep after unleashed torrential rains that overwhelmed a leaky pipe, eroding volcanic beneath the surface and causing a three-story to collapse into the void. This event, classified as a piping failure rather than a classic sinkhole, resulted in one fatality and highlighted vulnerabilities in the city's aging built on unstable volcanic fill. The in hosts one of the world's densest concentrations of sinkholes known as cenotes, with estimates exceeding 6,000 such features formed by the dissolution of limestone in this tropical, humid region. These natural wells, often interconnected through underground aquifers, served as vital water sources for ancient Maya communities and held profound spiritual significance as portals to the underworld (), where rituals including offerings and sacrifices were conducted to appease rain gods like Chaak. Among them, Cenote Ik Kil stands out for its dramatic vertical shaft, reaching about 40 meters deep with crystal-clear turquoise water, and its historical role in Maya ceremonies near the iconic site of . In , the Devil's Sinkhole in , represents a classic feature in the Zone, where a 15-meter-wide opening plunges 43 meters to a vast subterranean chamber over 100 meters across and up to 107 meters deep overall. This natural pit, formed by the collapse of a cavern roof, provides critical habitat for approximately 3 million Mexican free-tailed bats (Tadarida brasiliensis), which roost in the cool, humid interior from spring to fall, emerging at dusk in swirling clouds to forage on insects across the surrounding ranchlands. South America's sinkholes often occur in unique geological settings like table-top mountains (tepuis). Sima Humboldt, located on the summit of Sarisariñama Tepui in Bolívar State, Venezuela, is the world's deepest known sinkhole, plunging 314 meters with a rim diameter of 352 meters and expanding to over 500 meters wide at its base, where a isolated thrives in perpetual shadow. Formed through gradual erosion and collapse in the layers of the , this colossal pit exemplifies the dramatic karst-like processes in non-carbonate rocks, isolated from the surrounding tabletop plateau.

Asia and Oceania

In Asia and Oceania, sinkholes often form in landscapes dominated by soluble or in volcanic terrains mimicking features through lava tube collapses and fissures. These regions host some of the world's largest and most ecologically significant examples, where subtropical climates and tectonic activity accelerate dissolution and structural failures. Giant tiankengs—deep depressions—in southern exemplify mega-scale natural sinkholes, while mining-induced collapses in urbanizing areas highlight human impacts. Volcanic pseudokarst in the Pacific islands adds diversity, with pits forming from eruptive processes rather than chemical . The in , , stands as the largest known sinkhole by volume, measuring approximately 660 meters deep and holding about 130 million cubic meters of space within a subtropical system. Formed over millennia through the collapse of underground caves and rivers in the Daxi River valley, it features steep walls and a forested floor that harbors unique , including ancient and endemic preserved in its isolated . This has drawn scientific interest for its role in conserving relict ecosystems amid surrounding towers. Clusters of sinkholes in , particularly around Geleshan and Zhongliang towns, have increased due to drawdown from extensive operations, leading to surface collapses that threaten and . These cover-collapse sinkholes, often 10-20 meters wide and deep, result from the dissolution of underlying exacerbated by mining-induced voids and heavy rainfall infiltrating fractured . Recent incidents, including subsidences reported in 2024, underscore the ongoing risks in this densely populated region, where over 100 such events have been documented since the 2000s. In New Zealand's , the Waitomo Caves region features a network of limestone sinkholes formed over 30 million years through the dissolution of limestone by acidic . These tomo (Maori for sinkhole) entrances, some exceeding 100 meters deep, connect to underground rivers and caverns illuminated by bioluminescent glowworms, creating a unique that supports specialized . The system's accessibility has made it a key site for studying pseudokarst drainage in temperate climates, though pressures require careful management to prevent . Oceania's volcanic islands showcase pseudokarst sinkholes distinct from true , as seen in Hawaii's Volcano, where eruptive fissures and collapses form pit craters up to 1 kilometer wide. The Southwest Rift Zone features crevice pseudokarst with interconnected pits and tubes mimicking , but driven by thermal fracturing and pahoehoe lava flows rather than dissolution; recent activity in 2024-2025 has opened new sinkholes at the summit due to wall cracks. These features influence groundwater flow and provide habitats for native arthropods adapted to volcanic substrates. A notable recent event occurred in Guizhou Province, , in 2022, when heavy rains triggered multiple sinkholes in terrain, displacing villagers and damaging homes in a cluster near Fuquan City—though not directly swallowing entire villages, the collapses were linked to saturated soils over mined voids. In , similar rainfall-induced sinkholes have affected rural areas, but the 2018 Sulawesi produced liquefaction sinkholes that engulfed parts of Petobo village, burying structures under liquefied soil in a process akin to rapid . These incidents highlight how seasonal rains amplify vulnerabilities in Southeast Asia's tropical zones.

Europe

Europe hosts a variety of notable sinkholes, primarily formed through processes in regions or induced by human activities such as . These features range from dramatic natural chasms to catastrophic collapses threatening urban areas, showcasing the continent's diverse geological vulnerabilities. One of the most iconic natural sinkholes is the Macocha Abyss in the of the , a 138.5-meter-deep gorge that represents the deepest of its kind in . Formed by the collapse of a cavern roof, it connects to an extensive underground river system accessible via the Punkva Caves, drawing hundreds of thousands of visitors annually for its vertigo-inducing views from two suspension bridges. Local legend attributes its name to a stepmother who allegedly pushed her stepson into the abyss, though geological evidence points to natural dissolution over millennia. In , the Red Lake near exemplifies a massive collapse sinkhole within the Dinaric , plunging up to 530 meters deep and holding one of Europe's deepest karst lakes with a volume of 25-30 million cubic meters. The lake's striking red hue derives from in the surrounding cliffs, and its waters fluctuate seasonally due to underground drainage, making it a third-ranked global sinkhole by depth. Exploration has revealed multiple submerged caves, highlighting its role in regional . France's Gouffre de Padirac, located in the Lot department of Occitanie, stands as one of Europe's largest accessible natural chasms, measuring 103 meters deep and 35 meters wide at the entrance. Discovered in 1889 by explorer Édouard-Alfred Martel, this sinkhole opens into a vast underground network exceeding 10 kilometers, featuring a navigable subterranean river and stunning stalactite formations. Opened to the public in 1898, it attracts over 400,000 visitors yearly, underscoring its significance in European speleology. Induced sinkholes pose severe risks in mining regions, as seen in Russia's , where extraction since the 1940s has triggered multiple collapses in the city of over 150,000 residents. The largest crater, formed in 2007, spans 400 by 300 meters and 200 meters deep, displacing thousands and prompting ongoing evacuations and monitoring. Similar events, including a 2014 sinkhole measuring 30 by 50 meters, illustrate the long-term impacts of subsurface injection and dissolution on overlying . Urban sinkholes in highlight anthropogenic influences in karst-prone areas, such as the 2016 Florence incident where a burst water main created a 60-meter-long, 7-meter-deep depression that engulfed 50 vehicles in the historic city center. In , a 2021 collapse at Ospedale del Mare hospital swallowed cars in a 50-meter-wide hole linked to underground voids, while frequently experiences smaller "bouche d'enfer" sinkholes revealing ancient ruins, as in a 2020 event uncovering 2,000-year-old paving stones near the Pantheon. These occurrences, documented in national databases, emphasize 's high sinkhole density due to soluble evaporites and urban development.

References

  1. https://www.usgs.gov/faqs/what-a-sinkhole
  2. https://www.usgs.gov/water-science-school/science/sinkholes
  3. https://www.bgs.ac.uk/discovering-geology/earth-hazards/sinkholes/
  4. https://www.britannica.com/science/cave/Geographic-distribution-of-karst-terrain
  5. https://www.usgs.gov/faqs/what-difference-between-a-sinkhole-and-a-pothole
  6. https://www.dcr.virginia.gov/natural-heritage/vcbsinkholes
  7. https://education.nationalgeographic.org/resource/sinkhole/
  8. https://www.sciencedirect.com/topics/earth-and-planetary-sciences/sinkhole
  9. https://www.usgs.gov/faqs/how-can-i-tell-if-i-have-found-impact-crater
  10. https://www.cnn.com/2013/03/01/us/florida-sinkhole-explainer
  11. https://www.seattletimes.com/nation-world/huge-sink-hole-opens-causing-fatal-utah-crash/
  12. https://www.usgs.gov/faqs/how-many-sinkholes-open-a-year
  13. https://www.dcr.virginia.gov/natural-heritage/vcbsinkholes2
  14. https://www.nachi.org/sinkholes.htm
  15. https://www.usgs.gov/faqs/how-much-does-sinkhole-damage-cost-each-year-united-states
  16. https://nckri.org/karst/sinkholes/
  17. https://energy.virginia.gov/geology/Sinkholes.shtml
  18. https://oxfordre.com/naturalhazardscience/display/10.1093/acrefore/9780199389407.001.0001/acrefore-9780199389407-e-40
  19. https://pubs.usgs.gov/circ/1987/0968/report.pdf
  20. https://www.dw.com/en/climate-change-causes-more-dangerous-sinkholes-v2/a-72898512
  21. https://www2.tulane.edu/~sanelson/Natural_Disasters/subsidence.htm
  22. https://www.showcaves.com/english/explain/Speleology/Suffosional.html
  23. https://agupubs.onlinelibrary.wiley.com/doi/full/10.1002/2016JF003902
  24. https://www.jpl.nasa.gov/images/pia25553-the-ever-changing-swiss-cheese-of-mars/
  25. https://www.researchgate.net/publication/253032961_Pitting_within_the_Martian_South_Polar_Swiss_Cheese_Terrain
  26. https://marspedia.org/Sublimation_landscapes_on_Mars
  27. https://www.lpi.usra.edu/meetings/lpsc2006/pdf/1071.pdf
  28. https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2022JE007328
  29. https://www.nasa.gov/solar-system/nasas-lro-finds-lunar-pits-harbor-comfortable-temperatures/
  30. https://eos.org/articles/lunar-lava-tube-revealed-beneath-collapsed-pit
  31. https://science.nasa.gov/photojournal/pitted-terrain-on-mars-and-vesta/
  32. https://www.jpl.nasa.gov/news/what-looks-like-ceres-on-earth/
  33. https://agupubs.onlinelibrary.wiley.com/doi/full/10.1002/2016GL070370
  34. https://planetarygeomorphology.wordpress.com/2022/01/01/thermal-contraction-polygons-on-earth-and-mars/
  35. https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2022JE007303
  36. https://www.nasa.gov/solar-system/planets/mars/could-life-exist-below-mars-ice-nasa-study-proposes-possibilities/
  37. https://scienceblog.com/mars-ice-deposits-may-harbor-potential-for-microbial-life/
  38. https://www.jpl.nasa.gov/news/nasas-treasure-map-for-water-ice-on-mars/
  39. https://www.in.gov/indot/engineering/files/KARST-PROTECTION-and-INDOT-Const-7.15.2021.pdf
  40. https://kgs.uky.edu/kgsweb/olops/pub/kgs/ic04_12.pdf
  41. https://www.geology.arkansas.gov/geohazards/land-subsidence.html
  42. https://floridadep.gov/fgs/sinkholes/content/sinkhole-faq
  43. https://www.americanscientist.org/article/sinkholes-in-evaporite-rocks
  44. http://ogs.ou.edu/docs/circulars/C109.pdf
  45. https://people.wou.edu/~taylors/ES104_Lab/gwater_notes.pdf
  46. https://www.sciencedirect.com/topics/earth-and-planetary-sciences/pseudokarst
  47. https://www.usgs.gov/mission-areas/water-resources/science/karst-aquifers-pacific-northwest-pseudokarst-aquifers
  48. https://geology.teacherfriendlyguide.org/index.php/hazards-nc/hazards-karst-nc
  49. https://onlinelibrary.wiley.com/doi/10.1002/esp.3727
  50. https://www.researchgate.net/publication/257536521_Piping_in_loess-like_and_loess-derived_soils_Case_study_of_Halenkovice_site_Czech_Republic
  51. https://www.sciencedirect.com/science/article/pii/S0169555X97000317
  52. https://planetgeocast.com/episodes/are-you-karsty-sinkholes
  53. https://www.sciencedirect.com/science/article/pii/S2589471424000202
  54. https://www.karstwaters.org/wp-content/uploads/2023/06/SP9-Epikarst.pdf
  55. https://nhess.copernicus.org/articles/18/2355/2018/
  56. https://www.sciencedirect.com/science/article/abs/pii/S0169555X25003514
  57. https://geography.as.uky.edu/node/293613
  58. https://pubs.usgs.gov/circ/circ1182/pdf/15WCFlorida.pdf
  59. https://courier.unesco.org/en/articles/chinas-heavenly-pits-dive-unknown
  60. https://www.sciencedirect.com/science/article/abs/pii/S0169555X11001929
  61. https://www.showcaves.com/english/si/region/Notranjska.html
  62. http://nckms.org/wp-content/uploads/2018/05/halliday.pdf
  63. https://www.sciencedirect.com/science/article/pii/S0169555X25002697
  64. https://www.sciencedirect.com/science/article/pii/S0895981125000306
  65. https://www.intellinews.com/sinkholes-on-the-rise-across-asia-a-growing-danger-beneath-the-surface-394091/
  66. https://www.frontiersin.org/journals/earth-science/articles/10.3389/feart.2023.1207689/full
  67. https://www.flsenate.gov/UserContent/Session/2011/Publications/InterimReports/pdf/2011-104bi.pdf
  68. https://pmc.ncbi.nlm.nih.gov/articles/PMC6509126/
  69. https://agupubs.onlinelibrary.wiley.com/doi/full/10.1002/2017JF004219
  70. https://www.nationalgeographic.com/science/article/100603-science-guatemala-sinkhole-2010-humans-caused
  71. https://pubs.geoscienceworld.org/seg/tle/article/25/3/336/135245/Geophysical-applications-to-detect-sinkholes-and
  72. https://library.ctr.utexas.edu/ctr-publications/0-7071-1.pdf
  73. https://www.academia.edu/50037623/Integrated_geophysical_survey_in_a_sinkhole_prone_area_Microgravity_electrical_resistivity_tomographies_and_seismic_noise_measurements_to_delimit_its_extension
  74. https://pmc.ncbi.nlm.nih.gov/articles/PMC11548729/
  75. https://conservancy.umn.edu/bitstreams/6f615ae2-912a-4237-ae40-c170a189a35c/download
  76. https://www.pca.state.mn.us/sites/default/files/c-prp4-09.pdf
  77. https://downloads.regulations.gov/FDA-2014-N-2244-0224/content.pdf
  78. https://www.flhouse.gov/Statutes/2023/0627.706/
  79. https://www.mdpi.com/2072-4292/16/13/2264
  80. https://www.tandfonline.com/doi/full/10.1080/19475705.2021.1978562
  81. https://pubs.usgs.gov/of/2001/ofr-01-0484/ofr-01-0484so.pdf
  82. https://repositories.lib.utexas.edu/server/api/core/bitstreams/e52dbc85-b3f5-4322-9a7a-422b99ce42d8/content
  83. https://ucmp.berkeley.edu/science/fieldnotes/pakes_0806c.php
  84. https://doi-org.ezproxy.baylor.edu/10.5772/intechopen.106437
  85. https://www.smithsonianmag.com/smart-news/a-mass-grave-of-maya-boys-may-shed-light-on-human-sacrifice-in-chichen-itza-180984542/
  86. https://digitalcommons.usf.edu/kip_articles/7311/
  87. https://digitalcommons.usf.edu/cgi/viewcontent.cgi?article=1256&context=ijs
  88. https://pubs.usgs.gov/sir/2009/5049/pdf/Baker.pdf
  89. https://sites.northwestern.edu/monroyrios/some-maps/chicxulub-and-ring-of-cenotes/
  90. https://uisic.uis-speleo.org/uisglossary-en.html
  91. https://www.showcaves.com/english/explain/Karst/Tiankeng.html
  92. https://bcra.org.uk/pub/candks.oldformat/v32_2.html
  93. https://pubs.usgs.gov/wsp/1899k/report.pdf
  94. https://pmc.ncbi.nlm.nih.gov/articles/PMC5016797/
  95. https://www.merriam-webster.com/dictionary/polje
  96. https://www.showcaves.com/english/explain/Karst/Polje.html
  97. https://www.nature.com/articles/s41598-022-13678-0
  98. https://www.researchgate.net/profile/Tony-Waltham/publication/285472898_Sinkholes_and_Subsidence_Karst_and_Cavernous_Rocks_in_Engineering_and_Construction/links/624231bc5e2f8c7a03466886/Sinkholes-and-Subsidence-Karst-and-Cavernous-Rocks-in-Engineering-and-Construction.pdf
  99. https://www.researchgate.net/publication/266462319_Evolution_of_the_Dead_Sea_sinkholes
  100. https://www.jpost.com/business-and-innovation/energy-and-infrastructure/article-733798
  101. https://thenaturalhistorian.com/2024/12/09/dead-sea-chronicles-part-ii-the-lowest-place-on-earth-goes-lower-the-dead-seas-ongoing-crisis/
  102. https://www.atlasobscura.com/articles/dead-sea-sinkhole-kayaks-israel
  103. https://phys.org/news/2025-01-dead-sea-ecological-disaster.html
  104. https://www.cntraveler.com/stories/2014-06-02/qattara-depression-maphead
  105. https://www.researchgate.net/publication/320347080_CULTIVATION_OF_QATTARA_DEPRESSION_BY_THE_USE_OF_DESALINATED_WATER
  106. https://www.unc.edu/discover/conserving-sacred-portals-of-the-yucatan/
  107. https://dash.harvard.edu/server/api/core/bitstreams/c82e38b5-81d8-4321-868a-0251f8c17473/content
  108. https://sites.northwestern.edu/monroyrios/ring-of-cenotes/
  109. https://tpwd.texas.gov/state-parks/devils-sinkhole
  110. https://www.livescience.com/planet-earth/geology/14-of-the-deepest-sinkholes-on-earth
  111. https://www.bbc.com/travel/article/20221117-xiaoxhai-tiankeng-the-worlds-biggest-sinkhole
  112. https://www.ancient-origins.net/news-general/china-sinkhole-forests-biodiversity-0020750
  113. https://www.researchgate.net/publication/396198218_Formation_mechanism_analysis_of_karst_collapses_in_Geleshan_Town-Zhongliang_Town_Chongqing_China
  114. https://www.waitomo.com/
  115. https://www.tripsavvy.com/waitomo-glowworm-caves-the-complete-guide-4776329
  116. https://pubs.usgs.gov/publication/70260968
  117. https://caves.org/pub/journal/PDF/v69/cave-69-01-103.pdf
  118. https://www.usgs.gov/media/images/august-6-2025-sinkhole-summit-kilauea
  119. https://www.vulcanospeleology.org/sym06/ISV6x05.pdf
  120. https://www.scmp.com/news/china/science/article/3291950/chinese-villages-sinkhole-nightmare-continues-kitchen-floor-collapse
  121. https://www.abc.net.au/news/2018-10-04/indonesia-tsunami-petobo-and-balaroa-may-become-mass-graves/10335016
  122. https://www.adrc.asia/view_disaster_en.php?Lang=en&Key=2578
  123. https://www.south-moravia.com/en/sights/o70411-macocha-abyss
  124. https://www.tresbohemes.com/2023/07/macocha-abyss-beauty-and-tragedy/
  125. https://www.highonadventure.com/hoa18jul/czech-republic/punkva-caves-and-macocha-abyss.htm
  126. http://ui.adsabs.harvard.edu/abs/2012EGUGA..14.7132G/abstract
  127. https://www.alaturka.info/en/croatia/vid/2983-day-trip-to-vid-roman-trading-post-narona/en/croatia/2977-sinkholes-red-and-blue-lake-next-to-imotski
  128. https://www.myguidecroatia.com/culture/red-lake
  129. https://www.visit-dordogne-valley.co.uk/discover/natural-heritage/prehistoric-caves/gouffre-padirac
  130. https://www.gouffre-de-padirac.com/en/gouffre
  131. https://www.purefrance.com/en/blog/gouffre-de-padirac
  132. https://www.euronews.com/2017/12/05/welcome-to-berezniki-the-city-swallowed-by-sinkholes
  133. https://www.seattletimes.com/nation-world/sinkholes-slowly-devouring-soviet-era-city-atop-an-old-mine/
  134. https://www.mining.com/more-insane-pictures-of-russian-potash-mine-disaster-43899/
  135. https://www.nytimes.com/2016/05/26/world/europe/sinkhole-florence-italy.html
  136. https://www.bbc.com/news/av/world-europe-55589140
  137. https://www.thearchaeologist.org/blog/sinkhole-in-the-heart-of-rome-leads-to-the-discovery-of-ancient-ruins
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