A natural cavity in the Earth's surface, generally hollowed out by the action of water, and most spectacularly developed in limestones (soluble in mildly acid rainwater), in which huge vaults and interconnected river systems may form. Caves are also made by the action of sea water against cliffs, as in Fingal's Cave in the Scottish Hebrides. Ice caves may form in glaciers by streams of meltwater.
for artificial caves used as dwellings, such as those in north China, see yaodong.A cave is a natural underground void large enough for an adult human to enter. however, in popular usage, the term includes smaller spaces like cliff cavities, rock shelters and sea caves. The act of exploring a cave for recreation is called "caving", "potholing", or occasionally (only in the United States) "spelunking".
Types and formation
Caves are formed by geologic processes.
Primary caves
Some caves are formed at the same time as the surrounding rock. 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 such as solution and erosion. Also known as littoral caves, they form from wave action along zones of weakness in sea cliffs. (These are sometimes called ice caves, though this term is properly reserved for caves which contain year-round ice formations). The most common process of cave formation is karstification, which is the solution of rocks by rain water.
The largest and most abundant solutional caves are located in limestone. The world's most spectacularly decorated cave is generally regarded to be Lechuguilla Cave (New Mexico, USA).
Lechuguilla and nearby Carlsbad Caverns are now believed to be examples of another type of solutional cave.
Distribution and Records
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 the United States, France, Italy, the UK etc.). As a result, explored caves are found widely in Europe, Asia, North America, and Oceania 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 and parts of Brazil 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, despite containing around half the world's exposed limestone - more than 1,000,000 km² - has relatively few documented caves.
The system with the greatest total length of passage is Mammoth Cave (Kentucky, USA) at 579 km in length.
As of 2005, the deepest known cave (measured from its highest entrance to its lowest point) is Voronya Cave (Abkhazia, Georgia), with a depth of 2,140 m. The Gouffre Mirolda - Lucien Bouclier cave in France (1733 m) and the Lamprechtsofen Vogelschacht Weg Schacht in Austria (1632 m) are the current second and third deepest caves.
The deepest individual pitch (vertical drop) within a cave is 603 m in the Vrtoglavica cave in Slovenia, followed by Patkov Gušt (553 m) in the Velebit mountain, Croatia.
Since new caves are continually being explored, the various records of cave dimensions need to be updated fairly frequently.
For information on a specific cave, see list of caves.
Inhabitants
Cave-inhabiting animals are often categorized as troglobites (cave-limited species), troglophiles (species which can live their entire lives in caves, but also occur in other environments), trogloxenes (species which use caves, but cannot complete their life cycle wholly in caves) and accidentals (animals not in one of the previous categories). Aquatic troglobites (or stygobites), such as the endangered Alabama cave shrimp, live in bodies of water found in caves and get nutrients from detritus washed into their caves and from the faeces of bats and other cave inhabitants.
Bats, such as the Gray bat and Mexican Free-tailed Bat, are trogloxenes and are often found in 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 ecosytem, 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, Liphistiidae Liphistius trapdoor spider and the Gray bat.
Caves are visited by many surface-living animals, including humans.
Some tropical caves of southeast Asia are rich in cave fauna and some even have cave flora
Archaeological and social 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 scavanging animals, this means caves are an archaeological treasure house for learning about these people.
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 sediment 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.
User Comments Add a comment…