[From Wikipedia, the free encyclopedia]
The cave is a cavity in the earth’s upper crust, сообщающаяся with the surface of one or more entrances. Another definition: the cave is a natural underground cavity available for penetration of the person having with sunlight parts and length (depth) more than the other two dimensions. The largest caves in the complicated system of passages and halls, often with a total length of several tens of kilometers. Caves — an object of study of Speleology. A considerable contribution to the study of caves make the cavers.
The cave by their origin can be divided into five groups: tectonic, erosive, glacial, volcanic and, finally, the biggest group of karst. Caves in привходовой part, if appropriate morphology (horizontal spacious entrance) and the location (close to the water) used by the ancient people as comfortable dwellings.
Caves of origin
Most of these caves. It is karst caves have the greatest extent and depth. Karst caves are formed due to the dissolution of rocks water, so they found only there, where lie soluble rocks: limestone, marble, dolomite, chalk, as well as gypsum and salt. Limestone, and especially marble, dissolves pure distilled water is very bad. Several times solubility increases, if in water there is the dissolved carbon dioxide (and it is always present in natural water), but, still dissolves limestone poorly compared, say, with plaster or with salt. But it turns out that this has a positive effect on the formation of the longest caves, as gypsum and salt caves not only quickly formed, but quickly destroyed.
A great role in the formation of caves play tectonic cracks and faults. Cards explored caves, very often you can see that the moves are related to tectonic disturbance which can be traced to the surface. Also, for the education of the cave must have a sufficient amount of water sludge, successful form of relief: precipitation with large area should get into the cave, the entrance to the cave should be significantly higher than the place where they are unloaded underground water, etc.
Many karst caves are a relict of the system: water flow formed the cave, away from it due to changes in the topography or the deeper levels (because of decrease of local erosion basis — the bottom of the adjacent river valleys), or ceased to fall in the cave because of changes in the surface water catchment, after which the cave undergoes different phases of aging. Very often studied caves are small fragments of an ancient cave system, opened destruction enclosing mountain ranges.
Evolution of the karst processes and their chemism are such that often water and dissolved minerals rocks (carbonates, sulphates, after some time, lays them on the roofs and the walls of caves in the form of massive cor thickness of up to a meter or more (cave marble onyx) or specific to each cave ensembles of mineral aggregates caves, forming stalactites, stalagmites, helictites, draperies and other specific karst mineral forms — sinter.
Recently more caves opens the rocks, traditionally considered некарстующимися. For example, in Sandstone and quartzite table mountains тепуи South America were discovered caves Абисмо guy Colette depth -671 m (2006), Cueva Ojos de Cristal (Cueva Ojos de Cristal) is approximately 16 km (2009). Apparently, these caves have also karst origin. In a hot tropical climate, under certain conditions, quartzite can be dissolved with water.
Another exotic example of the formation of karst caves could be a very lengthy and the deepest in the continental U.S. cave Лечугия (and other caves Карлсбадского national Park). The modern hypothesis, it formed dissolution of limestone ascending thermal waters, rich with sulfuric acid.
Some caves can occur in any rocks as a result of formation of tectonic faults. Typically, these caves are found in the sides are deeply embedded in the high reaches of the river valleys, when vast tracts of breed break away from the sides, forming cracks отседания (шерлопы). Cracks отседания usually with depth converge wedge. Most often they fall over loose deposits from the surface of the array, but sometimes a rather deep vertical caves depth up to 100 m Шерлопы are widely distributed in Eastern Siberia. They have been studied relatively weak and is likely to occur very often.
Caves, formed insoluble rocks by mechanical erosion, that is worked by water containing grains of solid material. Often, these caves are formed on the shore of the sea under the influence of the surf, but they are insignificant. However, it is possible education and caves, based on primary tectonic fissures going under ground streams. Known quite large (hundreds of meters long) caves formed in sandstones and even granites. Examples of the large erosion of caves can be T.S.O.D. (Touchy Sword of Damocles) Cave in gabbro (4 km/-51 m, new York), Bat Cave in gneisses (1.7 km, North Carolina), Upper Millerton Lake Cave in granites (California).
The caves formed in the body of the glaciers melted water. These caves are found in many glaciers. Glacial meltwaters absorbed by the body of the glacier on major cracks or at the intersection of cracks forming moves, sometimes passable for a man. The length of these caves can be up to several hundred meters, depth — up to 100 m and more. In 1993 in Greenland was discovered and studied the giant ice well «Изортог» 173 m depth, inflow of water in the summer it was 30 m3.
Another type of glacial caves — caves, formed by a glacier, where внутриледниковых and subglacial water at the edge of the glaciers. Melt-water in these caves can flow as at glacier Lodge and glacial ice.
A special type of glacial caves — caves formed by the glaciers in the place of exit located under the glacier underground thermal waters. Hot water can do the bulk of the gallery, however, such caves lie not in the glacier, and under it, because the ice проплавляется bottom. Thermal glacier caves are found in Iceland, Greenland and grow to significant size.
These caves occur during volcanic eruptions. Lava flow, cooling down, covered with a solid crust, forming лавовую pipe, inside of which still flowing molten rock. After the eruption already, in fact, ended, lava flows from the bottom end of the tube, and inside the tube remains cavity. It is clear that the lava caves lie on the surface, and often roof collapses. However, as it turned out, lava caves can reach very large sizes, up to 65.6 km length and 1100 m depth (cave Казумура, Hawaii).
In addition to the lava tubes vertical volcanic caves — the crater of the volcano.
The cave on the type of host rocks
The longest in the world mammoth cave (USA) — karst, laid in the limestone. It has the total length of the passages more than 600 km The longest cave Russia — cave Botovskaya, over 60 km long, was laid in a relatively thin formation of limestone, nestled between the Sandstone, is located in Irkutsk region, pool R. Lena. Slightly behind her Large Орешная — long in the world karst cave in conglomerates in the Krasnoyarsk region. The longest cave in гипсах — Optimistic, Ukraine, length of more than 230 km. The formation of such longest caves in гипсах associated with a specific location breeds: layers of gypsum containing cave, are overlaid on top of limestone, due to what the vaults not falling in. Known cave in rock salt, in glaciers and in the solidified lava, etc
Caves in size
The deepest cave of the planet, too karst: Krubera-Voronya (to -2196 m), snow (-1753 m) in Abkhazia. In Russia the deepest cave Throat Барлога (900 m) in Karachaevo-Cherkessia. All these records are continuously changing, invariably only one thing: the leaders are the karst caves.
The depth of the cave is called the altitude difference between the input (the top-most of the inputs, if any) and the lowest point of the cave. If in the cave there are moves above input, using the concept of amplitude — the difference in level between the lowest and the highest point of the cave. According to estimates, the maximum depth of moves caves beneath the surface (not to be confused with the depth of the cave!) may not exceed 3,000 meters deep any cave crush the weight of the overlying rocks. For karst caves maximum depth of occurrence is defined basis карстования (lower limit of karst processes, coinciding with the base of the limestone strata), which can be lower than the erosion basis thanks to siphon channels. The deepest cave is currently cave Krubera-Voronya depth 2196 m, this is the first and only cave, which has overcome the barrier of 2 km. First surveyed cave depth of 1000 metres was the French abyss Berger, considered to be the deepest in the world with the opening in 1953 to 1963.
Although the living world of the caves, as a rule, not very rich (excluding привходовую part where sunlight), however, some animals live exactly in caves or even only in the caves. First of all, it bats, many species use the cave as a daily shelter or for wintering. And bats fly sometimes in very remote and inaccessible corners, perfectly guided in the labyrinth of narrow passages.
In addition bats, in some caves in areas with warm climates several species of insects, spiders (Neoleptoneta myopica), shrimp (Palaemonias alabamae) and other crustaceans, salamanders and fish (Amblyopsidae). Cave species adapt to the dark, and many of them lose sight organs and pigmentation. Often these species are very rare, many of them are endemic.
Primitive people used the caves around the world as the home. More often in caves settled animals. Many animals died in the caves traps, beginning with vertical wells. A very slow evolution of the caves, their constant climate, security from the outside world have preserved to us, a great number of archaeological finds. This fossil pollen plants, the bones of long-extinct animals (cave bear, cave hyena, mammoth, woolly rhinoceros), the rock paintings of ancient people (caves Капова in South Ural, Divya in the Northern Urals, Тузуксу Kuznetsk Alatau, Niah-Кейвз in Malaysia), the tools of their labour (PP. Terrible, Okladnikov anthropological remains, Fireplace in Altai), human remains of different cultures, including Neanderthals, age up to 50-200 thousand years (the cave of Teshik-Tash in Uzbekistan, Denisova cave in the Altai, CRO-Маньон in France and many others).
Water, as a rule, is in many caves and karst caves are obliged by it of its origin. In the caves can be found condensate film, drops, streams and rivers, lake and waterfalls. Siphons in caves significantly complicate passage, require special equipment and special training. Quite often there are underwater caves. In привходовых areas caves water is often present in a frozen state, in the form of ice deposits, often very considerable and perennial.
The air in the caves
In most caves air suitable for breath due to natural circulation, although there are caves in which you can be only in gas masks. For example, the air can poison guano deposits. However, in the vast majority of natural caves air exchange with the surface enough. Causes of air movement is often used as the temperature difference in the cave, and on the surface, therefore, the direction and intensity of the circulation depend on the season and weather conditions. In the large holes movement of air is so intense that turns into the wind. For this reason, the air draught is one of the most important features when looking for a new caves.
There are also mechanical (clay, sand, gravel, boulders) and chemogenic deposits (stalactites, stalagmites and so forth). In cave systems with active watercourse, as a rule, mechanical deposits are presented as blocky blockages, often very large amounts of produced as a result of the collapse of the arch moves, which forms the dissolution of the water flow. Blockages are a challenge to go through, and the danger, because the balance глыбового Zavala often unsustainable. Clay deposits are widely represented in the galleries, which had left active watercourse, to impose the mechanical insoluble particles of rocks. In the limestone, which holds the cave, soluble component is calcium carbonate, which is often, only about 50 % of the breed. Other minerals, as a rule, insoluble, and if the water is, the solvent of breed, presents in the form of droplets, infiltrate, with small consumption of water, incapable of providing mechanical particle transport, begins accumulation of clay sediments. Very often the ancient passages completely overlap clay.
Chemogenic deposits (sinter) are also decorated with ancient galleries of the cave, where the water, slowly фильтруясь on cracks in the limestone, saturated with calcium carbonate and acid in the cavity of the cave, a small change of water vapor partial pressure at separation drops, or if dropped it on the floor, or in the case of turbulence in flowing, from a saturated solution occurs crystallization of calcium carbonate in the form of calcite.
Some caves are open to the visitors tour groups (so-called showcaves). For this part of the cave, the most spacious and rich sinter, lay walkways, stairs, bridges, is the electric lighting; in some cases, if the input part of the cave is a technically difficult part, make their way into the tunnels. On the territory of the former USSR the most famous are the Marble cave in the Crimea, Kungurskaya in the Urals, in Abkhazia Novy Afon.