Cave
Overview
A cave or cavern is a natural underground space large enough for a human to enter. The term applies to natural cavities some part of which is in total darkness. The word cave also includes smaller spaces like rock shelter
Rock shelter
A rock shelter is a shallow cave-like opening at the base of a bluff or cliff....

s, sea caves, and grotto
Grotto
A grotto is any type of natural or artificial cave that is associated with modern, historic or prehistoric use by humans. When it is not an artificial garden feature, a grotto is often a small cave near water and often flooded or liable to flood at high tide...

s.

Speleology
Speleology
Speleology is the scientific study of caves and other karst features, their make-up, structure, physical properties, history, life forms, and the processes by which they form and change over time...

 is the science of exploration and study of all aspects of caves and the environment which surrounds the caves. Exploring a cave for recreation or science may be called caving, potholing, or, in Canada and the United States, spelunking (see caving
Caving
Caving—also occasionally known as spelunking in the United States and potholing in the United Kingdom—is the recreational pastime of exploring wild cave systems...

).
The formation and development of caves is known as speleogenesis
Speleogenesis
Speleogenesis is the origin and development of caves, the primary process that determines essential features of the hydrogeology of karst and guides its evolution...

.
Unanswered Questions
Encyclopedia
A cave or cavern is a natural underground space large enough for a human to enter. The term applies to natural cavities some part of which is in total darkness. The word cave also includes smaller spaces like rock shelter
Rock shelter
A rock shelter is a shallow cave-like opening at the base of a bluff or cliff....

s, sea caves, and grotto
Grotto
A grotto is any type of natural or artificial cave that is associated with modern, historic or prehistoric use by humans. When it is not an artificial garden feature, a grotto is often a small cave near water and often flooded or liable to flood at high tide...

s.

Speleology
Speleology
Speleology is the scientific study of caves and other karst features, their make-up, structure, physical properties, history, life forms, and the processes by which they form and change over time...

 is the science of exploration and study of all aspects of caves and the environment which surrounds the caves. Exploring a cave for recreation or science may be called caving, potholing, or, in Canada and the United States, spelunking (see caving
Caving
Caving—also occasionally known as spelunking in the United States and potholing in the United Kingdom—is the recreational pastime of exploring wild cave systems...

).

Types and formation

The formation and development of caves is known as speleogenesis
Speleogenesis
Speleogenesis is the origin and development of caves, the primary process that determines essential features of the hydrogeology of karst and guides its evolution...

. Caves are formed by various geologic processes. These may involve a combination of chemical processes, erosion from water, tectonic forces, microorganisms, pressure, atmospheric influences, and even digging.

Most caves are formed in limestone
Limestone
Limestone is a sedimentary rock composed largely of the minerals calcite and aragonite, which are different crystal forms of calcium carbonate . Many limestones are composed from skeletal fragments of marine organisms such as coral or foraminifera....

 by dissolution
Solvation
Solvation, also sometimes called dissolution, is the process of attraction and association of molecules of a solvent with molecules or ions of a solute...

.

Solutional cave

Solutional caves are the most frequently occurring caves and such caves form in rock that is soluble, such as limestone
Limestone
Limestone is a sedimentary rock composed largely of the minerals calcite and aragonite, which are different crystal forms of calcium carbonate . Many limestones are composed from skeletal fragments of marine organisms such as coral or foraminifera....

, but can also form in other rocks, including chalk
Chalk
Chalk is a soft, white, porous sedimentary rock, a form of limestone composed of the mineral calcite. Calcite is calcium carbonate or CaCO3. It forms under reasonably deep marine conditions from the gradual accumulation of minute calcite plates shed from micro-organisms called coccolithophores....

, dolomite
Dolomite
Dolomite is a carbonate mineral composed of calcium magnesium carbonate CaMg2. The term is also used to describe the sedimentary carbonate rock dolostone....

, marble, salt, and gypsum
Gypsum
Gypsum is a very soft sulfate mineral composed of calcium sulfate dihydrate, with the chemical formula CaSO4·2H2O. It is found in alabaster, a decorative stone used in Ancient Egypt. It is the second softest mineral on the Mohs Hardness Scale...

. Rock is dissolved by natural acid in groundwater that seeps through bedding-planes
Bed (geology)
In geology a bed is the smallest division of a geologic formation or stratigraphic rock series marked by well-defined divisional planes separating it from layers above and below. A bed is the smallest lithostratigraphic unit, usually ranging in thickness from a centimeter to several meters and...

, faults, joints and so on. Over geological epochs cracks expand to become caves or cave systems.

The largest and most abundant solutional caves are located in limestone. Limestone dissolves under the action of rainwater and groundwater charged with H2CO3 (carbonic acid
Carbonic acid
Carbonic acid is the inorganic compound with the formula H2CO3 . It is also a name sometimes given to solutions of carbon dioxide in water, because such solutions contain small amounts of H2CO3. Carbonic acid forms two kinds of salts, the carbonates and the bicarbonates...

) and naturally occurring organic acid
Organic acid
An organic acid is an organic compound with acidic properties. The most common organic acids are the carboxylic acids, whose acidity is associated with their carboxyl group –COOH. Sulfonic acids, containing the group –SO2OH, are relatively stronger acids. The relative stability of the conjugate...

s. The dissolution process produces a distinctive landform known as karst
KARST
Kilometer-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 the Kras region in Slovenia and Northern Italy. It will consist of...

, characterized by sinkhole
Sinkhole
A sinkhole, also known as a sink, shake hole, swallow hole, swallet, doline or cenote, is a natural depression or hole in the Earth's surface caused by karst processes — the chemical dissolution of carbonate rocks or suffosion processes for example in sandstone...

s, and underground drainage. Limestone caves are often adorned with calcium carbonate
Calcium carbonate
Calcium carbonate is a chemical compound with the formula CaCO3. It is a common substance found in rocks in all parts of the world, and is the main component of shells of marine organisms, snails, coal balls, pearls, and eggshells. Calcium carbonate is the active ingredient in agricultural lime,...

 formations produced through slow precipitation. These include flowstone
Flowstone
Flowstones are composed of sheetlike deposits of calcite formed where water flows down the walls or along the floors of a cave. They are typically found in "solution", or limestone caves, where they are the most common speleothem. However, they may form in any type of cave where water enters that...

s, stalactite
Stalactite
A stalactite , "to drip", and meaning "that which drips") is a type of speleothem that hangs from the ceiling of limestone caves. It is a type of dripstone...

s, stalagmite
Stalagmite
A stalagmite is a type of speleothem that rises from the floor of a limestone cave due to the dripping of mineralized solutions and the deposition of calcium carbonate. This stalagmite formation occurs only under certain pH conditions within the underground cavern. The corresponding formation on...

s, helictite
Helictite
A helictite is a speleothem found in limestone caves that changes its axis from the vertical at one or more stages during its growth. They have a curving or angular form that looks as if they were grown in zero gravity...

s, soda straw
Soda straw
A soda straw is a speleothem in the form of a hollow mineral tube. They grow in places where water leaches slowly through cracks in rock, such as on the roofs of caves...

s and columns. These secondary mineral deposits in caves are called speleothem
Speleothem
A speleothem , commonly known as a cave formation, is a secondary mineral deposit formed in a cave. Speleothems are typically formed in limestone or dolostone solutional caves.-Origin and composition:...

s
.

The portions of a solutional cave that are below the water table
Water table
The water table is the level at which the submarine pressure is far from atmospheric pressure. It may be conveniently visualized as the 'surface' of the subsurface materials that are saturated with groundwater in a given vicinity. However, saturated conditions may extend above the water table as...

 or the local level of the groundwater will be flooded.

The world's most spectacularly decorated cave is generally regarded to be Lechuguilla Cave
Lechuguilla Cave
Lechuguilla Cave is, as of June 2011, the sixth longest cave known to exist in the world, and the deepest in the continental United States , but it is most famous for its unusual geology, rare formations, and pristine condition....

 in New Mexico
New Mexico
New Mexico is a state located in the southwest and western regions of the United States. New Mexico is also usually considered one of the Mountain States. With a population density of 16 per square mile, New Mexico is the sixth-most sparsely inhabited U.S...

. Lechuguilla and nearby Carlsbad Cavern are now believed to be examples of another type of solutional cave. They were formed by H2S (hydrogen sulfide
Hydrogen sulfide
Hydrogen sulfide is the chemical compound with the formula . It is a colorless, very poisonous, flammable gas with the characteristic foul odor of expired eggs perceptible at concentrations as low as 0.00047 parts per million...

) gas rising from below, where reservoirs of oil give off sulfurous fumes. This gas mixes with ground water and forms H2SO4 (sulfuric acid
Sulfuric acid
Sulfuric acid is a strong mineral acid with the molecular formula . Its historical name is oil of vitriol. Pure sulfuric acid is a highly corrosive, colorless, viscous liquid. The salts of sulfuric acid are called sulfates...

). The acid then dissolves the limestone from below, rather than from above, by acidic water percolating from the surface.

Primary cave

Some caves are formed at the same time as the surrounding rock. These are sometimes called primary caves.

Lava tube
Lava tube
Lava tubes are natural conduits through which lava travels beneath the surface of a lava flow, expelled by a volcano during an eruption. They can be actively draining lava from a source, or can be extinct, meaning the lava flow has ceased and the rock has cooled and left a long, cave-like...

s are formed through volcanic activity and are the most common 'primary' caves. The lava
Lava
Lava refers both to molten rock expelled by a volcano during an eruption and the resulting rock after solidification and cooling. This molten rock is formed in the interior of some planets, including Earth, and some of their satellites. When first erupted from a volcanic vent, lava is a liquid at...

 flows downhill and the surface cools and solidifies. The hotter lava continues to flow under that crust, and if most of the liquid lava beneath the crust flows out, a hollow tube remains, thus forming a cavity. Examples of such caves can be found on the Canary Islands
Canary Islands
The Canary Islands , also known as the Canaries , is a Spanish archipelago located just off the northwest coast of mainland Africa, 100 km west of the border between Morocco and the Western Sahara. The Canaries are a Spanish autonomous community and an outermost region of the European Union...

, Hawaii
Hawaii (island)
The Island of Hawaii, also called the Big Island or Hawaii Island , is a volcanic island in the North Pacific Ocean...

, and many other places. Kazumura Cave
Kazumura Cave
Kazumura Cave is a lava tube and has been surveyed at 40.7 miles long and 3,614 feet deep making it the longest and deepest lava tube in the world. The cave is located on the island of Hawaii on the eastern slope of Kilauea. Kilauea is the most recently active volcano on the Big Island...

 near Hilo is a remarkably long and deep lava tube; it is 65.6 km (40.8 mi).

Lava caves, include but are not limited to lava tubes. Other caves formed through volcanic activity include rift caves, lava mold caves, open vertical volcanic conduits, and inflationary caves.

Sea cave or littoral cave

Sea caves are found along coasts around the world. A special case is littoral caves, which are formed by wave action in zones of weakness in sea cliffs. Often these weaknesses are faults, but they may also be dykes or bedding-plane contacts. Some wave-cut caves are now above sea level because of later uplift. Elsewhere, in places such as Thailand's Phang Nga Bay
Phang Nga Bay
Phang Nga Bay is a 400 km² bay in the Andaman Sea between the island of Phuket and the mainland of the Malay peninsula of southern Thailand. Since 1981, an extensive section of the bay has been protected as the Ao Phang Nga National Park...

, solutional caves have been flooded by the sea and are now subject to littoral erosion. Sea caves are generally around 5 metre in length but may exceed 300 metres (984.3 ft).

Corrasional cave or erosional cave

Corrasional or erosional caves are those that form entirely by erosion by flowing streams carrying rocks and other sediments. These can form in any type of rock, including hard rocks such as granite. Generally there must be some zone of weakness to guide the water, such as a fault or joint. A subtype of the erosional cave is the wind or aeolian cave, carved by wind-born sediments. Many caves formed initially by solutional processes often undergo a subsequent phase of erosional or vadose enlargement where active streams or rivers pass through them.

Glacier cave

Glacier caves occur in ice and under glacier
Glacier
A glacier is a large persistent body of ice that forms where the accumulation of snow exceeds its ablation over many years, often centuries. At least 0.1 km² in area and 50 m thick, but often much larger, a glacier slowly deforms and flows due to stresses induced by its weight...

s and are formed by melting. They are also influenced by the very slow flow of the ice, which tends to close the caves again. (These are sometimes called ice caves, though this term is properly reserved for caves that contain year-round ice formations).

Fracture cave

Fracture caves are formed when layers of more soluble minerals, such as gypsum, dissolve out from between layers of less soluble rock. These rocks fracture and collapse in blocks of stone.

Talus cave

Talus caves are the openings between rocks that have fallen down into a pile, often at the bases of cliffs (called "talus
Scree
Scree, also called talus, is a term given to an accumulation of broken rock fragments at the base of crags, mountain cliffs, or valley shoulders. Landforms associated with these materials are sometimes called scree slopes or talus piles...

").

Anchialine cave

Anchialine caves are caves, usually coastal, containing a mixture of freshwater and saline water (usually sea water). They occur in many parts of the world, and often contain highly specialized and endemic fauna.

Physical patterns

  • Branchwork caves resemble surface dentritic stream patterns; they are made up of passages that join downstream as tributaries. Branchwork caves are the most common of cave patterns and are formed near sinkhole
    Sinkhole
    A sinkhole, also known as a sink, shake hole, swallow hole, swallet, doline or cenote, is a natural depression or hole in the Earth's surface caused by karst processes — the chemical dissolution of carbonate rocks or suffosion processes for example in sandstone...

    s where groundwater recharge occurs. Each passage or branch is fed by a separate recharge source and converges into other higher order branches downstream.
  • Angular Network caves form from intersecting fissures of carbonate rock that have had fractures widened by chemical erosion. These fractures form high, narrow, straight passages that persist in widespread closed loops.
  • Anastomotic caves largely resemble surface braided streams with their passages separating and then meeting further down drainage. They usually form along one bed or structure, and only rarely cross into upper or lower beds.
  • Spongework caves are formed as solution cavities are joined by mixing of chemically diverse water. The cavities form a pattern that is three-dimensional and random, resembling a sponge.
  • Ramiform caves form as irregular large rooms, galleries, and passages. These randomized three-dimensional rooms form from a rising water table that erodes the carbonate rock with hydrogen-sulfide enriched water.
  • Pit cave
    Pit Cave
    A pit cave, or vertical cave — or often simply called a pit or pot — is a type of natural cave which contains one or more significant vertical shafts rather than being predominantly a conventional horizontal cave passage. Pit caves typically form in limestone as a result of long-term erosion by...

    s
    (vertical caves, potholes, or simply "pits") consist of a vertical shaft rather than a horizontal cave passage. They may or may not be associated with one of the above structural patterns.

Geographic distribution

Caves are found throughout the world, but only a portion of them have been explored and documented by cavers. The distribution of documented cave systems is widely skewed toward countries where caving has been popular for many years (such as France
France
The French Republic , The French Republic , The French Republic , (commonly known as France , is a unitary semi-presidential republic in Western Europe with several overseas territories and islands located on other continents and in the Indian, Pacific, and Atlantic oceans. Metropolitan France...

, Italy
Italy
Italy , officially the Italian Republic languages]] under the European Charter for Regional or Minority Languages. In each of these, Italy's official name is as follows:;;;;;;;;), is a unitary parliamentary republic in South-Central Europe. To the north it borders France, Switzerland, Austria and...

, Australia
Australia
Australia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...

, the UK
United Kingdom
The United Kingdom of Great Britain and Northern IrelandIn the United Kingdom and Dependencies, other languages have been officially recognised as legitimate autochthonous languages under the European Charter for Regional or Minority Languages...

, the United States
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...

, and so on.). As a result, explored caves are found widely in Europe, Asia, North America, and Oceania
Oceania
Oceania is a region centered on the islands of the tropical Pacific Ocean. Conceptions of what constitutes Oceania range from the coral atolls and volcanic islands of the South Pacific to the entire insular region between Asia and the Americas, including Australasia and the Malay Archipelago...

 but are sparse in South America, Africa, and Antarctica. This is a great generalization, as large expanses of North America and Asia contain no documented caves, whereas areas such as the Madagascar dry deciduous forests
Madagascar dry deciduous forests
The Madagascar dry deciduous forests represent a tropical dry forest ecoregion generally situated in the western part of Madagascar. The area has high numbers of endemic plant and animal species but has suffered large-scale clearance for agriculture...

 and parts of Brazil
Brazil
Brazil , officially the Federative Republic of Brazil , is the largest country in South America. It is the world's fifth largest country, both by geographical area and by population with over 192 million people...

 contain many documented caves. As the world’s expanses of soluble bedrock are researched by cavers, the distribution of documented caves is likely to shift. For example, China
China
Chinese civilization may refer to:* China for more general discussion of the country.* Chinese culture* Greater China, the transnational community of ethnic Chinese.* History of China* Sinosphere, the area historically affected by Chinese culture...

, despite containing around half the world's exposed limestone - more than 1000000 square kilometres (386,102.2 sq mi) - has relatively few documented caves.

Records and superlatives

  • The cave system with the greatest total length of surveyed passage is Mammoth Cave
    Mammoth Cave National Park
    Mammoth 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...

     (Kentucky
    Kentucky
    The Commonwealth of Kentucky is a state located in the East Central United States of America. As classified by the United States Census Bureau, Kentucky is a Southern state, more specifically in the East South Central region. Kentucky is one of four U.S. states constituted as a commonwealth...

    , USA
    United States
    The United States of America is a federal constitutional republic comprising fifty states and a federal district...

    ) at 628 kilometres (390.2 mi) in length. This record is unlikely to be surpassed in the near future, as the next most extensive known cave is Jewel Cave near Custer, South Dakota
    Custer, South Dakota
    Custer is a city in Custer County, South Dakota, United States. The population was 2,067 at the 2010 census. It is the county seat of Custer County.-History:...

    , at 242 kilometres (150.4 mi).

  • The longest surveyed underwater cave is Sistema Sac Actun in Yucatán
    Yucatán
    Yucatán officially Estado Libre y Soberano de Yucatán is one of the 31 states which, with the Federal District, comprise the 32 Federal Entities of Mexico. It is divided in 106 municipalities and its capital city is Mérida....

    , Mexico at 215 km (133.6 mi). The record has been exchanged several times with Sistema Ox Bel Ha
    Sistema Ox Bel Ha
    Ox Bel Ha is a cave system in Quintana Roo, Mexico. It is the longest explored underwater cave in the world and ranking no. 4 including dry caves. As of October 2011 the surveyed length is of underwater passages....

    , currently at 182 kilometres (113.1 mi).

  • The deepest known cave (measured from its highest entrance to its lowest point) is Voronya Cave
    Voronya Cave
    The Krubera Cave is the deepest known cave on Earth. It is located in the Arabika Massif of the Gagrinsky Range of the Western Caucasus, in the Gagra district of Abkhazia, Georgia’s breakaway republic.The difference in the altitude of the cave's entrance and its deepest explored point is...

     (Abkhazia
    Abkhazia
    Abkhazia is a disputed political entity on the eastern coast of the Black Sea and the south-western flank of the Caucasus.Abkhazia considers itself an independent state, called the Republic of Abkhazia or Apsny...

    ), with a depth of 2191 metres (7,188.3 ft). This was the first cave to be explored to a depth of more than 2 kilometres (1.2 mi). (The first cave to be descended below 1 kilometre (0.621372736649807 mi) was the famous Gouffre Berger
    Gouffre Berger
    The Gouffre Berger is a French cave discovered on 24 May 1953, by Joseph Berger, Bouvet, Ruiz de Arcaute and Marc Jouffray. From 1953 to 1963, it was regarded as the deepest cave in the world at , relinquishing this title to the previous contender, Pierre Saint Martin in 1964, after further...

     in France
    France
    The French Republic , The French Republic , The French Republic , (commonly known as France , is a unitary semi-presidential republic in Western Europe with several overseas territories and islands located on other continents and in the Indian, Pacific, and Atlantic oceans. Metropolitan France...

    .) The Illyuzia-Mezhonnogo-Snezhnaya cave in Abkhazia
    Abkhazia
    Abkhazia is a disputed political entity on the eastern coast of the Black Sea and the south-western flank of the Caucasus.Abkhazia considers itself an independent state, called the Republic of Abkhazia or Apsny...

    , (1753 metres or 5,751.3 ft) and the Lamprechtsofen Vogelschacht Weg Schacht in Austria
    Austria
    Austria , officially the Republic of Austria , is a landlocked country of roughly 8.4 million people in Central Europe. It is bordered by the Czech Republic and Germany to the north, Slovakia and Hungary to the east, Slovenia and Italy to the south, and Switzerland and Liechtenstein to the...

     (1632 metres or 5,354.3 ft) are the current second- and third-deepest caves, respectively. The deepest cave record has changed several times in recent years.

  • The deepest vertical shaft in a cave is 603 metres (1,978.3 ft) in Vrtoglavica Cave
    Vrtoglavica Cave
    The Vrtoglavica Cave is a cave located inside the Kanin mountain in the Slovenian part of the Julian Alps, near to the border between Slovenia and Italy. The cave holds the record for having the deepest single vertical drop of any cave on Earth at a depth of ....

     in Slovenia
    Slovenia
    Slovenia , officially the Republic of Slovenia , is a country in Central and Southeastern Europe touching the Alps and bordering the Mediterranean. Slovenia borders Italy to the west, Croatia to the south and east, Hungary to the northeast, and Austria to the north, and also has a small portion of...

    . The second deepest is Patkov Gušt
    Velebit caves
    The Velebit mountain of Croatia has several deep caves with some of the world's largest subterranean vertical drops."Lukina jama" cave is 1392 m deep , the deepest cave in Croatia and the deepest in southeast Europe...

     at 553 metres (1,814.3 ft) in the Velebit
    Velebit
    Velebit is the largest though not the highest mountain range in Croatia. Its highest peak is the Vaganski vrh at 1757 m.The range forms a part of the Dinaric Alps and is located along the Adriatic coast, separating it from Lika in the interior...

     mountain, Croatia
    Croatia
    Croatia , officially the Republic of Croatia , is a unitary democratic parliamentary republic in Europe at the crossroads of the Mitteleuropa, the Balkans, and the Mediterranean. Its capital and largest city is Zagreb. The country is divided into 20 counties and the city of Zagreb. Croatia covers ...

    .

  • The largest room ever discovered is the Sarawak Chamber
    Sarawak chamber
    The Sarawak Chamber is a huge chamber in Gua Nasib Bagus , which is located in Gunung Mulu National Park, in the Malaysian state of Sarawak on the island of Borneo. It is considered to be the largest known underground chamber in the world....

    , in the Gunung Mulu National Park
    Gunung Mulu National Park
    Gunung Mulu National Park near Miri, Sarawak, Malaysian Borneo, is a UNESCO World Heritage Site that encompasses incredible caves and karst formations in a mountainous equatorial rainforest setting...

     (Miri
    Miri
    Miri is a city in northern Sarawak, Malaysia, on the island of Borneo. It is the second largest city in Sarawak, with a population of about 300,000, and the government administrative centre of Miri District in Miri Division....

    , Sarawak
    Sarawak
    Sarawak is one of two Malaysian states on the island of Borneo. Known as Bumi Kenyalang , Sarawak is situated on the north-west of the island. It is the largest state in Malaysia followed by Sabah, the second largest state located to the North- East.The administrative capital is Kuching, which...

    , Borneo
    Borneo
    Borneo is the third largest island in the world and is located north of Java Island, Indonesia, at the geographic centre of Maritime Southeast Asia....

    , Malaysia), a sloping, boulder strewn chamber with an area of approximately and a height of 80 metres (262.5 ft). The nearby Clearwater Cave System is believed to be the world's largest cave by volume, with a calculated volume of 30,347,540 m3.

  • The largest passage ever discovered is in the Son Doong Cave
    Son Doong Cave
    Son Doong cave is a cave in Phong Nha-Ke Bang National Park, Bo Trach District, Quang Binh Province, Vietnam. The cave is located near the Laos-Vietnam border . It has a large fast-flowing underground river inside.The cave was found by a local man named Hồ-Khanh in 1991...

     in Phong Nha-Ke Bang National Park in Quang Binh Province
    Quang Binh Province
    Quảng Bình , formerly Tiên Bình under the reign of Le Trung Hung of the Lê Dynasty, this province was renamed Quảng Bình in 1604) is a province in the North Central Coast of Vietnam....

    , Vietnam
    Vietnam
    Vietnam – sometimes spelled Viet Nam , officially the Socialist Republic of Vietnam – is the easternmost country on the Indochina Peninsula in Southeast Asia. It is bordered by China to the north, Laos to the northwest, Cambodia to the southwest, and the South China Sea –...

    . Explored by joint Vietnamese-British cave scientists of the British Cave Research Association
    British Cave Research Association
    The British Cave Research Association is a speleological organisation in the United Kingdom. Its object is to promote the study of caves and associated phenomena, and it attains this by supporting cave & karst research, encouraging original exploration , collecting and publishing speleological...

    , it is 4.6 km (2.9 mi) in length, 80 m (262.5 ft) high and wide over most of its length, but over 140 m (459.3 ft) high and wide for part of its length.

World's five longest surveyed caves

  1. Mammoth Cave, Kentucky
    Kentucky
    The Commonwealth of Kentucky is a state located in the East Central United States of America. As classified by the United States Census Bureau, Kentucky is a Southern state, more specifically in the East South Central region. Kentucky is one of four U.S. states constituted as a commonwealth...

    , USA
  2. Jewel Cave, South Dakota
    South Dakota
    South Dakota is a state located in the Midwestern region of the United States. It is named after the Lakota and Dakota Sioux American Indian tribes. Once a part of Dakota Territory, South Dakota became a state on November 2, 1889. The state has an area of and an estimated population of just over...

    , USA
  3. Optymistychna Cave
    Optymistychna Cave
    Optymistychna is a gypsum cave located near the Ukrainian village of Korolivka, Borschiv Raion, Ternopil Oblast. , it has 230 km of mapped passageways and is the largest cave complex in Eurasia...

    , Ukraine
    Ukraine
    Ukraine is a country in Eastern Europe. It has an area of 603,628 km², making it the second largest contiguous country on the European continent, after Russia...

  4. Wind Cave, South Dakota
    South Dakota
    South Dakota is a state located in the Midwestern region of the United States. It is named after the Lakota and Dakota Sioux American Indian tribes. Once a part of Dakota Territory, South Dakota became a state on November 2, 1889. The state has an area of and an estimated population of just over...

    , USA
  5. Sistema Sac Actun, Mexico
    Mexico
    The United Mexican States , commonly known as Mexico , is a federal constitutional republic in North America. It is bordered on the north by the United States; on the south and west by the Pacific Ocean; on the southeast by Guatemala, Belize, and the Caribbean Sea; and on the east by the Gulf of...


Ecology

Cave-inhabiting animals are often categorized as troglobite
Troglobite
Troglobites are small cave-dwelling animals that have adapted to their dark surroundings. Troglobite species include spiders, insects, fish and others. They live permanently underground and cannot survive outside the cave environment. Troglobite adaptations and characteristics include a heightened...

s (cave-limited species), troglophiles (species that can live their entire lives in caves, but also occur in other environments), trogloxene
Trogloxene
Trogloxenes are species which live close to caves or at the very entrance of the cave. Cliff swallows, cave swallows, cave swiftlets, reticulated pythons, rats, bats, bears, raccoons and humans are considered to be trogloxenes...

s (species that use caves, but cannot complete their life cycle wholly in caves) and accidentals (animals not in one of the previous categories). Some authors use separate terminology for aquatic forms (for example, stygobites, stygophiles, and stygoxenes).

Of these animals, the troglobites are perhaps the most unusual organisms. Troglobitic species often show a number of characteristics, termed troglomorphic, associated with their adaptation to subterranean life. These characteristics may include a loss of pigment (often resulting in a pale or white coloration), a loss of eyes (or at least of optical functionality), an elongation of appendages, and an enhancement of other senses (such as the ability to sense vibrations in water). Aquatic troglobites (or stygobites), such as the endangered Alabama cave shrimp
Alabama cave shrimp
The Alabama cave shrimp, Palaemonias alabamae, is a species of shrimp in the family Atyidae, found only in caves in the state of Alabama.-Conservation status:...

, live in bodies of water found in caves and get nutrients from detritus washed into their caves and from the feces of bats and other cave inhabitants. Other aquatic troglobites include cave fish, the Olm
Olm
The olm, or proteus , is a blind amphibian endemic to the subterranean waters of caves of the Dinaric karst of southern Europe. It lives in the waters that flow underground through this extensive limestone region including waters of the Soča river basin near Trieste in Italy, through to southern...

, and cave salamanders such as the Texas Blind Salamander
Texas Blind Salamander
The Texas Blind Salamander ', is a rare cave-dwelling troglobite amphibian native to San Marcos, Hays County, Texas, specifically the San Marcos Pool of the Edwards Aquifer. The salamander has blood-red external gills for absorbing oxygen from the water. The salamander's mature length is...

.

Cave insects
Cave insects
Caves are perhaps the most distinct and well-defined of insect habitats. A number of insects are permanent habitual inhabitants of caves, characterized by marked specializations for the extreme conditions. These are the true cavernicole species. Most caverniculous insect species are severely...

 such as Oligaphorura (formerly Archaphorura) schoetti are troglophiles, reaching 1.7 millimetre (0.0669291338582677 in) in length. They have extensive distribution and have been studied fairly widely. Most specimens are female but a male specimen was collected from St Cuthberts Swallet in 1969.

Bat
Bat
Bats are mammals of the order Chiroptera "hand" and pteron "wing") whose forelimbs form webbed wings, making them the only mammals naturally capable of true and sustained flight. By contrast, other mammals said to fly, such as flying squirrels, gliding possums, and colugos, glide rather than fly,...

s, such as the Gray bat
Gray Bat
Myotis grisescens once flourished in caves all over the southeastern United States, but due to human disturbance, Gray Bat populations declined severely during the early and mid portion of the 20th century. At one cave alone, the Georgetown Cave in Northwestern Alabama, populations declined from...

 and Mexican Free-tailed Bat
Mexican Free-tailed Bat
The Mexican free-tailed bat , also known as the Brazilian free-tailed bat, is a medium-sized bat that is native to the Americas and is widely regarded as one of the most abundant mammals in North America...

, are trogloxenes and are often found in caves; they forage outside of the caves. Some species of cave crickets are classified as trogloxenes, because they roost in caves by day and forage above ground at night.

Because of the fragile nature of the cave ecosystem, and the fact that cave regions tend to be isolated from one another, caves harbor a number of endangered species, such as the Tooth cave spider
Tooth cave spider
The tooth cave spider is a 1/16 inch long arachnid. It is endemic to Texas and is considered an endangered species....

, Liphistiidae
Liphistiidae
The spider family Liphistiidae comprises 5 genera and 85 species from Southeast Asia, China, and Japan. They are among the most basal living spiders, belonging to the suborder Mesothelae...

 Liphistius trapdoor spider, and the Gray bat
Gray Bat
Myotis grisescens once flourished in caves all over the southeastern United States, but due to human disturbance, Gray Bat populations declined severely during the early and mid portion of the 20th century. At one cave alone, the Georgetown Cave in Northwestern Alabama, populations declined from...

.

Caves are visited by many surface-living animals, including humans. These are usually relatively short-lived incursions, due to the lack of light and sustenance.

Cave entrances often have typical florae. For instance, in the eastern temperate United States, cave entrances are most frequently (and often densely) populated by the bulblet fern, Cystopteris bulbifera
Cystopteris bulbifera
Cystopteris bulbifera ' is a low-growing rock fern with creeping stems and narrow elongate deltate fronds which grow to 75 cm , native to eastern North America with two disjunct populations in the west. It is found only on calcareous substrates such as limestone. It commonly festoons limestone cave...

.

Archaeological and cultural importance

Throughout history, primitive peoples have made use of caves for shelter, burial, or as religious sites. Since items placed in caves are protected from the climate and scavenging animals, this means caves are an archaeological treasure house for learning about these people. Cave painting
Cave painting
Cave paintings are paintings on cave walls and ceilings, and the term is used especially for those dating to prehistoric times. The earliest European cave paintings date to the Aurignacian, some 32,000 years ago. The purpose of the paleolithic cave paintings is not known...

s are of particular interest. One example is the Great Cave of Niah
Niah Caves
Niah Caves is located within the district of Miri in Sarawak, Malaysia. Part of Niah National Park, the main cave, Niah Great Cave, is located in Gunung Subis and is made up of several voluminous, high-ceilinged chambers...

, in Malaysia, which contains evidence of human habitation dating back 40,000 years. Another, the Diepkloof Rock Shelter
Diepkloof Rock Shelter
Diepkloof Rock Shelter is a rock cave in Western Cape, South Africa in which has been found some of the earliest evidence of the human use of symbols, in the form of patterns engraved upon ostrich eggshell water containers. These date around 60,000 years ago.The symbolic patterns consist of lines...

 in South Africa contains evidence of human habitation and use of symbols dating back 60,000 years.

See also

  • Cave Conservancies
    Cave Conservancies
    A cave conservancy is a specialized land trust that primarily manages caves or karst features in the United States. Organizations that serve as cave management consultants to cave owners are usually considered cave conservancies. Almost all cave conservancies are non-profit organizations, but their...

  • Cave Research Foundation
    Cave Research Foundation
    The Cave Research Foundation is an American private, non-profit group dedicated to the exploration, research, and conservation of caves. The group arose in the early 1950s from the exploration efforts at Floyd Collins Crystal Cave, now within Mammoth Cave National Park...

  • Cenote
    Cenote
    A cenote is a deep natural pit, or sinkhole, characteristic of Mexico and Central America, resulting from the collapse of limestone bedrock that exposes groundwater underneath...

  • Flowstone
    Flowstone
    Flowstones are composed of sheetlike deposits of calcite formed where water flows down the walls or along the floors of a cave. They are typically found in "solution", or limestone caves, where they are the most common speleothem. However, they may form in any type of cave where water enters that...

  • List of caves
  • National Speleological Society
    National Speleological Society
    The National Speleological Society is an organization formed in 1941 to advance the exploration, conservation, study, and understanding of caves in the United States. Originally located in Washington D.C., its current offices are in Huntsville, Alabama...

  • Pit cave
    Pit Cave
    A pit cave, or vertical cave — or often simply called a pit or pot — is a type of natural cave which contains one or more significant vertical shafts rather than being predominantly a conventional horizontal cave passage. Pit caves typically form in limestone as a result of long-term erosion by...

  • Speleology
    Speleology
    Speleology is the scientific study of caves and other karst features, their make-up, structure, physical properties, history, life forms, and the processes by which they form and change over time...

  • Speleothem
    Speleothem
    A speleothem , commonly known as a cave formation, is a secondary mineral deposit formed in a cave. Speleothems are typically formed in limestone or dolostone solutional caves.-Origin and composition:...

  • Subterranean lake
  • Subterranean river
    Subterranean river
    A subterranean river is a river that runs wholly or partly beneath the ground surface – one where the riverbed does not represent the surface of the Earth ....


External links

The source of this article is wikipedia, the free encyclopedia.  The text of this article is licensed under the GFDL.
 
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