Cave

, New Mexico]] A cave or cavern is a natural underground space large enough for a human to enter. Some people suggest that the term cave should only apply to natural cavities some part of which is in total darkness; however, in popular usage, the term includes smaller spaces like sea caves, rock shelters, and grottos.

Speleology 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).

Types and formation

The formation and development of caves is known as speleogenesis. 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 by dissolution. s in Hall of the Mountain King, Ogof Craig a Ffynnon, South Wales.]]

Solutional cave

Solutional caves are the most frequently occurring caves and such caves form in rock that is soluble, such as limestone, but can also form in other rocks, including chalk, dolomite, marble, salt, and gypsum. Rock is dissolved by natural acid in groundwater that seeps through bedding-planes, faults, joints etc. 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) and naturally occurring organic acids. The dissolution process produces a distinctive landform known as karst, characterized by sinkholes, and underground drainage. Limestone caves are often adorned with calcium carbonate formations produced through slow precipitation. These include flowstones, stalactites, stalagmites, helictites, soda straws and columns. These secondary mineral deposits in caves are called speleothems.

The portions of a solutional cave that are below the water table or the local level of the groundwater will be flooded.

The world's most spectacularly decorated cave is generally regarded to be Lechuguilla Cave in New Mexico. Lechuguilla and nearby Carlsbad Cavern are now believed to be examples of another type of solutional cave. They were formed by H₂S (hydrogen sulfide) gas rising from below, where reservoirs of oil give off sulfurous fumes. This gas mixes with ground water and forms H₂SO₄ (sulfuric acid). The acid then dissolves the limestone from below, rather than from above, by acidic water percolating from the surface.

Primary cave

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

Lava tubes are formed through volcanic activity and are the most common 'primary' caves. The lava 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, Hawaii, and many other places. Kazumura Cave near Hilo is a remarkably long and deep lava tube; it is .

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

, Santa Cruz Island, California]] 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, solutional caves have been flooded by the sea and are now subject to littoral erosion. Sea caves are generally around in length but may exceed .

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

in Big Four Glacier, Big Four Mountain, Washington, ca. 1920.]] Glacier caves occur in ice and under glaciers 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").

Anchihaline cave

Anchihaline 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 faunas.

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 sinkholes 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.

*The longest surveyed underwater cave is the Ox Bel Ha Cave System in Yucatán, Mexico at . This was the first cave to be explored to a depth of more than . (The first cave to be descended below was the famous Gouffre Berger in France.) The Illyuzia-Mezhonnogo-Snezhnaya cave in Abkhazia, () and the Lamprechtsofen Vogelschacht Weg Schacht in Austria () are the current second- and third-deepest caves. The deepest cave record has changed several times in recent years.

*The deepest vertical shaft in a cave is in Vrtoglavica Cave in Slovenia. The second deepest is Patkov Gušt at in the Velebit mountain, Croatia.

*The largest room ever discovered is the Sarawak chamber, in the Gunung Mulu National Park (Miri, Sarawak, Borneo, Malaysia), a sloping, boulder strewn chamber with an area of approximately and a height of . 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 in Phong Nha-Ke Bang National Park in Quang Binh Province, Vietnam. Explored by joint Vietnamese-British cave scientists of the British Cave Research Association, it is in length, high and wide over most of its length, but over high and wide for part of its length.

World's longest caves

# Mammoth Cave, Kentucky Another, the Diepkloof Rock Shelter in South Africa contains evidence of human habitation and use of symbols dating back 60,000 years.

In the animal kingdom, caves offer shelter, including uses such as maternity dens.

In Germany some experts found signs of cannibalism in the caves at the Hönne.

Caves are also important for geological research because they can reveal details of past climatic conditions in speleothems and sedimentary rock layers.

Caves are frequently used today as sites for recreation. Caving, for example, is the popular sport of cave exploration. For the less adventurous, a number of the world's prettier and more accessible caves have been converted into show caves, where artificial lighting, floors, and other aids allow the casual visitor to experience the cave with minimal inconvenience. Caves have also been used for BASE jumping and cave diving. The book Caverns of Magic by Hal G. P. Colebatch surveys some of the instances of cave stories in literature and mythology.

Caves are also used for the preservation or aging of wine and cheese. The constant, slightly chilly temperature and high humidity that most caves possess makes them ideal for such uses.

See also

, Slovenia]] , Mexico.]]

Cave Conservancies

Cave Research Foundation

Cenote

Flowstone

List of caves

National Speleological Society

Pit cave

Speleology

Speleothem

Subterranean lake

Subterranean river

References

External links

Australian Speleological Federation (ASF), AU

British Caving Association (BCA), UK

The Mulu Caves Project, A British-Malaysian collaboration to explore the caves of the Gunung Mulu National Park, Sarawak

Classification of Caves A list of cave types with links to further information

Journal of Cave and Karst Studies

National Speleological Society (NSS), US

International Union of Speleology (UIS).

Speleological Abstract (SA/BBS) An annual review of the world's speleological literature.

The Virtual Cave Large educational site with numerous photographs of various types of caves and cave formations and descriptions of how they form.

cave-biology.org Cave biology (biospeleology) in India.

Biospeleology; The Biology of Caves, Karst, and Groundwater, by Texas Natural Science Center, The University of Texas at Austin and the Missouri Department of Conservation.

Tour Caves A Google Map of Commercial Tour Caves in the US.

French Caves List of Commercial Caves in France.

Caves of Croatia List and details about longest and deepest caves and pits in Croatia.

Cathedral Cave Preserve A privately owned speleological research and educational park. US

The latest news from the caving scene.

World Cave Database

Category:Coastal geography Category:Erosion landforms Category:Fluvial landforms