Karst caves – underground cavities, communicating with the earth surface or closed, are formed at leaching of soluble rocks. Karst caves are natural shafts, wells, cavities, which have clear boundaries and appear in covering not water-saturated and water-saturated karst rocks. One of the forms of underground karst. They are divided into subtypes: corrosive-erosion, nival-corrosion, corrosive-gravity, corrosive-abrasion, travertine.
For the surface of the areas of karst development are characterized by small furrows and cavities – carras, closed depressions (funnels, pits, polya, natural wells and mines, blind ravines and valleys), niches in the cliffs. In the limestone karst of the tropics are common remains (Mogote). The most typical funnels (conical, cauldron-mitten or irregularly shaped pits) with a diameter of 1 to 200 m or more and a depth of 0.5 to 50 m, and sometimes much more. At the bottom of funnels and other depressions there are absorbing water holes – pore holes, which are often the beginning of mines or wells, chasms, sometimes reaching a depth of more than 1000 m. (maximum depth is 1410 m. – Jean-Bernard Abyss in the Alps, France). Pits and funnels can be filled with water or drained (periodically disappearing lakes). Troughs with an area of up to several tens and hundreds of km2 with disappearing watercourses are known as poles. In karsted massifs various underground passages, cavities and karst caves are formed, which often develop along cracks. One of the largest caves in the world, Mammoth Cave, with the cave system Flint Ridge (in North America on the territory of the USA, Kentucky) reaches 341 km of total length. The total length of more than 100 km. have caves Halloch (Switzerland, the Alps), Jewell (USA, South Dakota), 9 caves of the world length of more than 50 km, 14 – more than 40 km.
Complex of surface and underground karst forms is most fully expressed when the surface of soluble rocks is exposed (bare karst); less expressed when these rocks are covered with a layer of soil and turf (delayed karst), insoluble loose sediments (covered karst), semi-rock and rock formations (armored karst). In case of deep burial of soluble rocks under the nonkarst thicknesses of the buried karst is formed.
To form a karst cave requires an array of karst rocks (mainly limestone or gypsum) with a sufficient catchment area, and the height difference. Morphologically, karst caves are systems of vertical sinkholes, shafts, wells, horizontal slopes and passages, sometimes with meanders, traps, halls and labyrinths. In many karst caves there are leaky-dropped formations (stalactites, stalagmites, stalagmites) and capillary-film mineral aggregates (crystalline and corallite, heliktites, etc.), and along the edges of stagnant underground reservoirs. There are underground rivers, streams, traps, waterfalls, cave lakes. For the inner parts of caves are characterized by a special microclimate, the absence of sunlight, increased concentration of carbon dioxide, a kind of fauna (so-called speleofauna). The air temperature inside the deep extended caves is characterized by constancy and, except for glacial caves, is equal to the average annual temperature of the surrounding area.