A
sinkhole, also known as a
sink,
shake hole,
swallow hole,
swallet,
doline or
cenoteA cenote is a sinkhole with exposed rocky edges containing groundwater. It is typically found in the Yucatán Peninsula and some nearby Caribbean islands...
, is a natural depression or hole in the surface topography caused by the removal of
soilSoil is a natural body consisting of layers of mineral constituents of variable thicknesses, which differ from the parent materials in their morphological, physical, chemical, and mineralogical characteristics. It is composed of particles of broken rock that have been altered by chemical and...
or bedrock, often both, by water. Sinkholes may vary in size from less than a meter to several hundred meters both in diameter and depth, and vary in form from soil-lined bowls to bedrock-edged chasms. They may be formed gradually or suddenly, and are found worldwide. These terms are often used interchangeably though many will distinguish between those features into which a surface stream flows and those which have no such input. Only the former would be described as sinks, swallow holes or swallets.
Mechanisms
Mechanisms of formation may include the gradual removal of slightly soluble bedrock (such as
limestoneLimestone is a sedimentary rock composed largely of the mineral calcite . The deposition of limestone strata is often a by-product and indicator of biological activity in the geologic record...
) by percolating water, the
collapseSubsidence is the motion of a surface as it shifts downward relative to a datum such as sea-level. The opposite of subsidence is uplift, which results in an increase in elevation...
of a
caveA cave or cavern is a natural underground void large enough for a human to enter. Some people suggest that the term cave should only apply to cavities that have some part that does not receive daylight; however, in popular usage, the term includes smaller spaces like sea caves, rock shelters, and...
roof, or a lowering of the
water tableThe water table is the level at which the groundwater pressure is equal to atmospheric pressure. It may be conveniently visualized as the 'surface' of the groundwater in a given vicinity. It usually coincides approximately with the 'phreatic surface', but can be many feet above it...
. Occasionally a sinkhole may exhibit a visible opening into a cave below. In the case of exceptionally large sinkholes, such as Cedar Sink at
Mammoth Cave National ParkMammoth Cave National Park is a U.S. National Park in central Kentucky, encompassing portions of Mammoth Cave, the longest cave system known in the world. The official name of the system is the Mammoth-Flint Ridge Cave System for the ridge under which the cave has formed. The park was established...
, USA, a
streamA stream is a flowing body of water with a current, confined within a bed and stream banks. Depending on its locale or certain characteristics, a stream may be referred to as a branch, brook, beck, burn, creek, kill, lick, rill, river syke, bayou, rivulet, or run...
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
limestoneLimestone is a sedimentary rock composed largely of the mineral calcite . The deposition of limestone strata is often a by-product and indicator of biological activity in the geologic record...
,
carbonate rockCarbonate rocks are a class of sedimentary rocks composed primarily of carbonate minerals. The two major types are limestone and dolomite, composed of calcite and the mineral dolomite respectively...
,
salt bedsHalite is the mineral form of sodium chloride, NaCl, commonly known as rock salt. Halite forms isometric crystals. The mineral is typically colorless to yellow, but may also be light blue, dark blue, and pink depending on the amount and type of impurities...
, or rocks that can naturally be dissolved by circulating ground water. 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.
Sinkholes can be human-induced. New sinkholes have been correlated to land-use practices, especially from ground-water pumping, construction, and development practices. Sinkholes can also form when natural water-drainage patterns are changed and new water-diversion systems are developed. Some sinkholes form when the land surface is changed, such as when industrial and runoff-storage ponds are created. The substantial weight of the new material can trigger an underground collapse of supporting material, thus causing a sinkhole.
Occurrence
Sinkholes may capture surface
drainageDrainage is the natural or artificial removal of surface and sub-surface water from an area. Many agricultural soils need drainage to improve production or to manage water supplies.-Early history:...
for running or standing water, but may also form in currently high and dry locations. The state of
FloridaFlorida is a state located in the southeastern region of the United States, bordering Alabama to the northwest and Georgia to the north. It was the 27th state admitted to the United States...
in the USA is known for having frequent sinkholes, especially in the central part of the state. The Murge area in southern Italy also has numerous sinkholes. Sinkholes can be formed in retention ponds from large amounts of rain.
Sinkholes are usually but not always linked with
karstKilometer-square Area Radio Synthesis Telescope is a Chinese telescope project to which FAST is a forerunner. KARST is a set of large spherical reflectors on karst landforms, which are bowlshaped limestone sinkholes named after a Yugoslavian geologist Karst. It will consist of about 30 individual...
landscapes. In such regions, there may be hundreds or even thousands of sinkholes in a small area so that the surface as seen from the air looks pock-marked, and there are no surface streams because all drainage occurs sub-surface.
Sinkholes have been used for centuries as disposal sites for various forms of
wasteWaste is unwanted or unusable material.In living organisms, waste is the unwanted substances or toxins that are expelled from them. More commonly, waste refers to the materials that are disposed of in a system of waste management.Waste is directly linked to human development, both technologically...
. A consequence of this is the
pollutionPollution is the introduction of contaminants into an environment that causes instability, disorder, harm or discomfort to the ecosystem i.e. physical systems or living organisms . Pollution can take the form of chemical substances, or energy, such as noise, heat, or light...
of
groundwaterGroundwater is water located beneath the ground surface in soil pore spaces and in the fractures of lithologic formations. A unit of rock or an unconsolidated deposit is called an aquifer when it can yield a usable quantity of water. The depth at which soil pore spaces or fractures and voids in...
resources, with serious
healthAt the of the creation of the World Health Organization , in 1948, Health was defined as being "a state of complete physical, mental, and social well-being and not merely the absence of disease or infirmity"....
implications in such areas. In contrast, the
Maya civilizationThe Maya is a Mesoamerican civilization, noted for the only known fully developed written language of the pre-Columbian Americas, as well as its art, architecture, and mathematical and astronomical systems. Initially established during the Preclassic period , many Maya cities reached their highest...
sometimes used sinkholes in the
Yucatán PeninsulaThe Yucatán Peninsula, in southeastern Mexico, separates the Caribbean Sea from the Gulf of Mexico, with the northern coastline on the Yucatán Channel...
(known as cenotes) as places to deposit precious items and sacrifices.
Sinkholes also form from human activity, such as the rare but still occasional collapse of abandoned
mineMining is the extraction of valuable minerals or other geological materials from the earth, usually from an ore body, vein or seam. Materials recovered by mining include base metals, precious metals, iron, uranium, coal, diamonds, limestone, oil shale, rock salt and potash...
s in places like
West VirginiaWest Virginia is a state in the Appalachian and Mid-Atlantic regions of the United States, bordered by Virginia to the southeast, Kentucky to the southwest, Ohio to the northwest, and Pennsylvania and Maryland to the northeast...
, USA. More commonly, sinkholes occur in
urban areaAn urban area is characterized by higher population density and vast human features in comparison to areas surrounding it. Urban areas may be cities, towns or conurbations, but the term is not commonly extended to rural settlements such as villages and hamlets.Urban areas are created and further...
s due to water main breaks or
sewerA sanitary sewer is a type of underground carriage system, , for transporting sewage from houses or industry to treatment or disposal...
collapses when old
pipePipeline transport is the transportation of goods through a pipe. Most commonly, liquid and gases are sent, but pneumatic tubes that transport solid capsules using compressed air have also been used....
s give way. They can also occur from the overpumping and extraction of groundwater and subsurface fluids.
Many sinkholes are also found in Northern Michigan. These are prominent in Alpena County in Northeast Michigan. In Lachine, Michigan there are five sinkholes that are found to be very deep , and within two miles of each other. Alpena's visitor information cites their sinkholes as an attraction for visitors to the area. In August 1998 a 16 year old Alpena boy survived a 200+ ft fall in an open sinkhole 3/4 a mile off of Leer road in Lachine Michigan (The
Alpena NewsThe Alpena News is a general daily newspaper in the City of Alpena, Michigan. USA. It has an approximate circulation of 10,000, and is published by Ogden Newspapers, Inc. News reports are available on line. The paper was founded in 1902...
8-21-1998). A majority of sinkholes in Alpena are also found underwater. Many divers explore these on a regular basis.
When sinkholes are very deep or connected to caves, they may offer challenges for experienced cavers or, when water-filled,
diversCave diving is a type of technical diving in which specialized SCUBA equipment is used to enable the exploration of natural or artificial caves which are at least partially filled with water...
. Some of the most spectacular are the
ZacatónZacatón is one of a group of five interconnected sinkholes, or cenotes, located in the northeastern state of Tamaulipas, Mexico. It is the deepest water-filled sinkhole in the world with a total depth of...
cenote in Mexico (the world's deepest water-filled sinkhole), the
BoesmansgatBoesmansgat, also known in English as "Bushman's Hole", is believed to be the third-deepest submerged freshwater cave in the world, approximately 270 metres deep...
sinkhole in South Africa,
SarisariñamaThe Sarisariñama tepui is a mountain in the Jaua-Sarisariñama National Park at the far south-west of Bolívar State, Venezuela, near the border with Brazil. Height: 2,300 metres....
tepuy in Venezuela, and in the town of
Mount Gambier, South AustraliaMount Gambier is the second most populous city in South Australia after Adelaide, the capital of the state.It is approximately 450 kilometres south of Adelaide and 435 kilometres west of Melbourne.-History:...
. Sinkholes that form in coral reefs and islands that collapse to enormous depths are known as
Blue HoleBlue Hole is a diving location on east Sinai, a few kilometres north of Dahab, Egypt on the coast of the Red Sea.The Blue Hole is a submarine pothole , around 130m deep. There is a shallow opening around 6m deep, opening out to the sea and an 26m tunnel, known as the arch, the top of which is 52m...
s, and often become popular diving spots.
In the
United StatesThe United States of America is a federal constitutional republic comprising fifty states and a federal district...
, the most damage from sinkholes tends to occur in
FloridaFlorida is a state located in the southeastern region of the United States, bordering Alabama to the northwest and Georgia to the north. It was the 27th state admitted to the United States...
,
TexasTexas is the second-largest U.S. state in both area and population, and the largest state in the contiguous United States.The name had wide usage among native Americans, meaning "friends" or "allies"...
,
AlabamaAlabama is a state located in the southeastern region of the United States of America. It is bordered by Tennessee to the north, Georgia to the east, Florida and the Gulf of Mexico to the south, and Mississippi to the west. Alabama ranks 30th in total land area and ranks second in the size of its...
,
MissouriMissouri is a state in the Midwest region of the United States bordered by Iowa, Illinois, Kentucky, Tennessee, Arkansas, Oklahoma, Kansas and Nebraska. Missouri is the 18th most populous state with a 2008 estimated population of 5,911,605. It comprises 114 counties and one independent city....
,
KentuckyThe Commonwealth of Kentucky is a state located in the East Central United States of America. Kentucky is a Southern state situated in the Upland South, although the state is infrequently placed, geographically and culturally, in the Midwest. Kentucky is one of four U.S. states constituted as a...
,
TennesseeTennessee is a state located in the Southeastern United States. According to the 2008 census, it has a population of 6,214,888, an increase of nearly 9.5% since 2000. Tennessee is the 14th fastest growing state in the US and is ranked 17th by population. It is ranked 36th by total land area. In...
, and
PennsylvaniaThe Commonwealth of Pennsylvania , often colloquially referred to as PA by natives and Northeasterners, is a state located in the Northeastern and Middle Atlantic regions of the United States...
.
Palmyra, PennsylvaniaPalmyra is a borough in Lebanon County, Pennsylvania, United States. It is part of the Lebanon, PA Metropolitan Statistical Area. The population was 7,096 at the 2000 census.-Geography:Palmyra is located at ....
is the sinkhole capitol of
AmericaThe United States of America is a federal constitutional republic comprising fifty states and a federal district...
.
The
overburdenOverburden is the term used in mining and archaeology to describe material that lies above the area of economic or scientific interest, e.g., the rock, soil and ecosystem that lies above the coal seam or ore body. It is also known as 'waste'...
sediments that cover buried cavities in the aquifer systems are delicately balanced by
groundwaterGroundwater is water located beneath the ground surface in soil pore spaces and in the fractures of lithologic formations. A unit of rock or an unconsolidated deposit is called an aquifer when it can yield a usable quantity of water. The depth at which soil pore spaces or fractures and voids in...
fluid pressure. The water below ground is actually helping to keep the surface soil in place. Groundwater pumping for urban water supply and for irrigation can produce new sinkholes in sinkhole-prone areas. If pumping results in a lowering of groundwater levels, then underground structural failure, and thus, sinkholes, can occur.
See also
- Blue Hole
Blue Hole is a diving location on east Sinai, a few kilometres north of Dahab, Egypt on the coast of the Red Sea.The Blue Hole is a submarine pothole , around 130m deep. There is a shallow opening around 6m deep, opening out to the sea and an 26m tunnel, known as the arch, the top of which is 52m...
- Blyvooruitzicht
Blyvooruitzicht is a gold-mining village in Gauteng, South Africa. It is situated about 3.5 km South of the centre of Carletonville and 80 km westwards from Johannesburg.-History:...
- Cenote
A cenote is a sinkhole with exposed rocky edges containing groundwater. It is typically found in the Yucatán Peninsula and some nearby Caribbean islands...
- Foiba
Foiba is a type of deep natural sinkhole, doline, sink and is a collapsed portion of bedrock above a void. Sinks may be a sheer vertical opening into a cave, or a shallow depression of many acres which are common in the Kras region, a karstic plateau region shared by Italy, Slovenia and...
- Great Blue Hole
The Great Blue Hole is a large underwater sinkhole off the coast of Belize. It lies near the center of Lighthouse Reef, a small atoll from the mainland and Belize City. The hole is circular in shape, over across and deep. It was formed as a limestone cave system during the last glacial period...
- Karst topography
Karst topography is a landscape shaped by the dissolution of a layer or layers of soluble bedrock, usually carbonate rock such as limestone or dolomite....
- Lake-burst
A Lake-burst is a phenomenon referred to in Irish mythology, in which a previously non-existent lake comes into being, often when a grave is being dug. It is thought to be a reference to the collapse of the thin roof of a water-filled cave, creating a sinkhole....
- Lake Peigneur disaster
Lake Peigneur is located in the U.S. State of Louisiana north of Delcambre and west of New Iberia, near the northernmost tip of Vermilion Bay.-History:...
- Oak Island
Oak Island is a 140-acre island in Lunenberg County on the south shore of Nova Scotia, Canada. The tree-covered island is one of about 360 small islands in Mahone Bay and rises to a maximum of 35 feet above sea level....
- Pipe Creek Sinkhole
Pipe Creek Sinkhole near Swayzee in Grant County, Indiana, is one of the most important paleontological sites in the interior of the eastern half of North America. Uncovered in 1996 by workers at the Pipe Creek Junior limestone quarry, the sinkhole has yielded a diverse array of fossils from the...
- Sarisariñama
The Sarisariñama tepui is a mountain in the Jaua-Sarisariñama National Park at the far south-west of Bolívar State, Venezuela, near the border with Brazil. Height: 2,300 metres....
- Sinkhole Dersios
The Dersios sinkhole is a sinkhole in Arcadia, Greece.The sinkhole, which has a depth of , has been known since antiquity and is located towards the north end of the plateau of Palaiochora at a height of 750 m above sea level on mount Parnon...
- Subsidence
Subsidence is the motion of a surface as it shifts downward relative to a datum such as sea-level. The opposite of subsidence is uplift, which results in an increase in elevation...
- Turlough (lake)
A Turlough, or Turlach, is a unique type of disappearing lake found mostly in limestone areas of Ireland, west of the River Shannon. The name comes from the Irish "tuar", meaning dry, with the suffix "lach", meaning a place . The "lach" suffix is often mistakenly spelled and/or thought to refer to...
- Voçoroca
In Brazil, a voçoroca or boçoroca is a geological phenomenon that consists of a sudden collapse of a large area of land caused by rain and windstorms. This occurs on ground where surface vegetation is scarce and cannot protect the ground from runoff...
- Zacatón
Zacatón is one of a group of five interconnected sinkholes, or cenotes, located in the northeastern state of Tamaulipas, Mexico. It is the deepest water-filled sinkhole in the world with a total depth of...
External links