Cave

Alternate meanings: Cave (disambiguation)

The outside world viewed from a cave
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The outside world viewed from a cave

A cave is a natural underground void.

Contents

Cave types and formation

Caves are formed by geologic processes. These may involve a combination of chemical processes, tectonic forces and atmospheric influences.

Primary caves

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

Lava tube cave at Craters of the Moon
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Lava tube cave at Craters of the Moon

Lava tubes are formed through volcanic activity. They are the most common primary caves. Lava flows downhill and the surface cools down and becomes hard. The lava now flows inside its crust, until the eruption ends. The liquid lava inside the crust flows out and leaves a hollow tube. The most important lava tubes are found on Hawaii (Big Island). Kazumura Cave near Hilo is the longest and deepest lava tube of the world and also the eighth longest cave of the United States.

Blister caves are also formed through volcanic activity.

Secondary caves

Secondary caves are formed inside the rock after the rock itself has formed by processes which removes material such as solution and erosion.

Erosion is a mechanical form of weathering which is caused by the abrasive action of wind or water.

  • Sea caves are very common at all coasts of the world, but as they are restricted to the zone where waves work on the rocks of the coast they are generally rather small.
Ice cave in Big Four Glacier, Big Four Mountain, Washington, ca. 1920
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Ice cave in Big Four Glacier, Big Four Mountain, Washington, ca. 1920
  • Ice caves occur in and under glaciers, formed by melting. They are also influenced by the very slow flow of the ice which tends to close the caves again.

Solutional caves may form anywhere with rock which is soluble, and are most prevalent in limestone, but can also form in other material, including chalk, dolomite, marble, loess, ice, granite, salt, lava, sandstone, and gypsum. The most common process of cave formation is karstification, which is the solution of rocks by rain water.

Cave formation in limestone occurs because limestone dissolves under the action of rainwater and groundwater charged with CO2 (carbonic acid) and naturally occurring organic acids. The dissolution process produces a distinctive landform known as karst and characterized by sinkholes, sinking streams, and underground drainage.

Limestone solution is the single most important process forming caves and the origin of the great majority of all caves on Earth. The reason for this abundance is the facts that limestone is so common and the slowness of the solution process. If it was faster, the lifespan of limestone caves would be much shorter and their number much lower.

Speleothems in Hall of the Mountain Kings, Ogof Craig a Ffynnon, South Wales
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Speleothems in Hall of the Mountain Kings, Ogof Craig a Ffynnon, South Wales

Limestone caves are often adorned with calcium carbonate formations produced through slow precipitation, including the most common and well-known stalactites and stalagmites. These secondary mineral deposits in caves are called speleothems. The world's most spectacularly decorated cave is generally regarded to be Lechuguilla Cave (New Mexico, USA).

Distribution

Caves are sparse in South America, Africa, and Antarctica, but are found widely in Europe, Asia, and North America.

The distribution of cave systems so far discovered is widely skewed toward countries where caving is popular (such as the United States, France, Italy, the UK etc.). It is likely that many more systems will be discovered, especially in China, which, despite containing around half the world's exposed limestone - more than 1,000,000 km2 - has hardly been explored underground.

Life

Caves are often home to a type of animals called troglodites. These animals, like the endangered Alabama cave shrimp, are usually small, albino and sightless. They often live in bodies of water found in the caves and are fed by detritus washed into the caves by groundwater movement.

Bats, like the Gray bat and Mexican Free-tailed Bat, are another kind of non-trogladite animal found in caves that have surface openings.

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

Records

Caves can reach considerable dimensions. Of the cave systems that have been discovered so far, the most extensive is Mammoth Cave (Kentucky, USA) with 560km of passages.

The deepest known cave (2004) is the Voronya Cave (Abkhazia, Georgia), with a depth of 1,830m. The Lamprechtsofen Vogelschacht Weg Schacht in Austria (1632m) and Gouffre Mirolda - Lucien Bouclier cave in France (1626m) also deserve mention.

The deepest individual vertical drop within a cave, is 516m in the Lukina jama, which is in the Velebit mountain, in Croatia. The largest individual cavern found is the Gua Niah (also known as the Sarawak Chamber), Deer Cave (Borneo, Malaysia) with an area of approximately 600m by 400m and a height of 80m.

Archaeological and social importance

Caves are also an archaeological treasure house as primitive people used caves as their shelter and sometimes burial place. Items placed in caves are protected from climate and scavanging animals. One example is the Great Cave of Niah, which is one of the largest limestone caves in the world as well as an archaeological treasure house. It was here that archaeologists discovered the evidence of Man’s existence dating back 40,000 years.

Caving is the sport of cave exploration.

See also

External links



cy:Ogof da:Grotte de:Höhle eo:Kaverno ms:Gua nl:Grot ja:洞窟 sv:Grotta

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