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Cave

2007 Schools Wikipedia Selection. Related subjects: Geology and geophysics

   Lechuguilla Cave, New Mexico
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   Lechuguilla Cave, New Mexico

   A cave is a natural underground void large enough for an adult human to
   enter. Some scientists stipulate that it must be large enough that some
   portion of it will not receive daylight; however, in popular usage, the
   term includes smaller spaces like cliff cavities, rock shelters and sea
   caves. Speleology is the scientific exploration and study of all
   aspects of 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. These may involve a combination
   of chemical processes, erosion from water, tectonic forces and
   atmospheric influences.

Primary caves

   Exploring a lava tube in Hawaii
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   Exploring a lava tube in Hawaii

   Some caves are formed at the same time as the surrounding rock. These
   are called primary caves.
     * Lava tubes are formed through volcanic activity. They are the most
       common primary caves. Lava flows downhill and the surface cools and
       solidifies. The lava now flows under this crust, until the eruption
       ends. If the liquid lava inside the crust flows out, a hollow tube
       remains.

   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.

   Painted Cave, one of the world's largest sea caves, Santa Cruz Island,
   California
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   Painted Cave, one of the world's largest sea caves, Santa Cruz Island,
   California

Secondary caves

   Secondary caves are formed inside the rock after the rock itself has
   formed by processes such as solution and erosion.
     * Sea caves are very common along coasts around the world. Also known
       as littoral caves, they form from wave action along zones of
       weakness in sea cliffs. Most commonly these are faults, but may
       also be dikes or bedding plane contacts. Some wave-cut caves are
       now high and dry due to uplift. Conversely, in places like
       Thailand's Phang Nga Bay, solutional caves have been flooded by the
       sea and are now subject to littoral erosion. Sea caves are
       generally rather small but may exceed 300 meters in length. One of
       the largest concentrations of large sea caves is found on Santa
       Cruz Island in California.

   Glacier cave in Big Four Glacier, Big Four Mountain, Washington, ca.
   1920.
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   Glacier cave in Big Four Glacier, Big Four Mountain, Washington, ca.
   1920.
     * Glacier caves occur in ice 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. (These are sometimes called ice
       caves, though this term is properly reserved for caves which
       contain year-round ice formations).

     * 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, granite, salt,
       sandstone, fossilized coral and gypsum. The most common process of
       cave formation is karstification, which is the solution of rocks by
       rain water.
          + 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.
     * Talus caves are the openings between rocks that have fallen down
       into a pile, often at the bases of cliffs.

   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.

   The largest and most abundant solutional caves are located in
   limestone. Limestone dissolves under the action of rainwater and
   groundwater charged with H[2]CO[3] ( carbonic acid) and naturally
   occurring organic acids. The dissolution process produces a distinctive
   landform known as karst, characterized by sinkholes, sinking streams,
   and underground drainage. 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).

   Lechuguilla and nearby Carlsbad Caverns are now believed to be examples
   of another type of solutional cave. They were formed by acid rising
   from below, where reservoirs of oil give off sulfurous fumes, rather
   than by acidic water percolating from the surface.

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.
   Canyon passage in Mammoth Cave, world's longest
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   Canyon passage in Mammoth Cave, world's longest

   The system with the greatest total length of passage is Mammoth Cave (
   Kentucky, USA) at 579 km in length. This record is unlikely to be
   surpassed in the near future as the next most extensive known cave is
   the Optymistychna system in Ukraine, at 214 km.

   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. This was the first cave to be explored to a depth of more
   than 2 km. (The first cave to be descended below 1 km was the famous
   Gouffre Berger in France). 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. This
   particular record has changed several times in recent years.

   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.

   The largest individual cavern ever discovered is the Sarawak Chamber,
   in the Gunung Mulu National Park ( Sarawak, Borneo, Malaysia), a
   sloping, boulder strewn chamber with an area of approximately 600 m by
   400 m and a height of 80 m.

   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

   Townsend's Big-eared bats in a cave
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   Townsend's Big-eared bats in a cave

   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). Some authors use separate terminology for aquatic
   forms (e.g., stygobites, stygophiles, and stygoxenes).

   Of these animals, the troglobites are perhaps the most unusual
   organisms. Troglobitic species often show a number of characteristics,
   termed troglomorphies, 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, 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. Other aquatic troglobites include cave
   fish and the Olm.

   Bats, such as the Gray bat and Mexican Free-tailed Bat, 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 ecosytem, and the fact that
   cave regions tend to be isolated from one another, caves harbour 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.
   These are usually relatively short-lived incursions, due to the lack of
   light and sustenance.

   Some tropical caves of southeast Asia are rich in cave fauna and some
   even have cave flora

Archaeological and social importance

   Taino petroglyphs in a cave in Puerto Rico
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   Taino petroglyphs in a cave in Puerto Rico

   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. Cave
   paintings are of particular interest. One example is the Great Cave of
   Niah, which contains evidence of human habitation dating back 40,000
   years.

   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.
   Retrieved from " http://en.wikipedia.org/wiki/Cave"
   This reference article is mainly selected from the English Wikipedia
   with only minor checks and changes (see www.wikipedia.org for details
   of authors and sources) and is available under the GNU Free
   Documentation License. See also our Disclaimer.
