What is a karst cave. Karst caves

Karst caves, photos of which can be seen in this article, are widespread throughout the world. It is for this species that formation with the greatest extent and depth is characteristic. In most cases, when caves form naturally, their shape depends on the degree of influence of water on rocks. That is why karst caves are found in those places where there are deposits of various soluble rocks.

Limestone dissolves very poorly under the influence of pure water. At the same time, if the water contains an increased amount of carbon dioxide, the solubility of the rock can accelerate several times.

Basic data

Karst caves are underground cavities that can form an exit to the surface or form in a closed space. In fact, they are depressions of various lengths and lengths, created naturally, without human intervention, in a variety of karst rocks. At the same time, the karst layer in each cave has its own percentage of moisture content.

It is noteworthy that salt caves are formed and destroyed quickly enough, as a result of which they almost never have time to reach the same length as limestone or marble, formed under the influence of water.

The relief of the caves

For the accelerated formation of such caves, it is necessary to have small cracks and depressions called kars in the rock layers, as well as a network of such natural holes as:

• Funnels. A characteristic feature is the irregular or conical shape of the recess. They reach a diameter of up to 250-300 m at a depth of 50 m to 100 m. At the bottom, you can find special holes called ponors, into which the bulk of groundwater gradually drains. These sites are often the initial formations of future mines, wells or abysses, the depth of which in some cases exceeds a thousand meters. So, for example, one of the largest abysses in the world called Jean-Bernard is located in the Alps of France. Its depth is 1410 m.
• Basins are cavities periodically filled with water (disappearing lakes).
• Polya are hollows 20-200 km 2 in size. They are also characterized by periodic filling with water.
• Wells.
• Mines.

It is noteworthy that underground passages and depressions of various lengths initially form in karst rocks, and a full-fledged karst cave begins to gradually form from them, the formation of which can take more than one hundred years.

Education

The formation of karst caves largely depends on tectonic cracks and faults, into which large volumes of water sediments flow over a long period. In addition, for the formation of a cave, it is necessary that the entrance to it be located much higher than the place where groundwater accumulates. It is noteworthy that the main feature of karst processes is that often water, having dissolved the rock, after some time washes it back, forming a number of sinter formations.

The degree of expressiveness of karst forms

According to the degree of expressiveness, surface and underground karst formations can be divided into:

• naked - pronounced and located on the surface of the earth;
• turfed - can be covered with a layer of soil;
• covered - the karst layer is covered with loose sediments with an insoluble structure;
• armored - the karst layer is covered with semi-rock and rock formations.

Inside such caves, as a result of the lack of access to sunlight and the increased content of carbon dioxide concentration, a special microclimate has been observed for centuries, which allows preserving the natural beauty of karst formations.

Climate influence

In regions that are characterized by low air temperatures, the underground cavities of karst caves in the winter season freeze so much that even in summer the temperature in them does not rise above zero. In such caves one can often observe the formation of ice crust, stalactites or other forms of frozen moisture on the ceiling and walls.

Karst caves of the world

The longest cave in the world, formed in limestone, was named Mamontova. It is located in the USA (Kentucky) and has a total length of over 400 km. Two rivers flow through it at once: the Styx and the Echo.

The longest cave in gypsum - Optimistic - is located in Ukraine (Ternopil region, Podolia). It was discovered back in 1966. The length of the passages in it is more than 230 km. The area of ​​the cave itself reaches 2 hectares. This length was achieved due to the fact that the layers of gypsum in which the cave was formed are covered from above with a layer of limestone, which keeps the vaults from collapsing.

It is noteworthy that the deepest caves in the world are also karst. An example is the Abkhaz: Krubera-Voronya and Snezhnaya. The depth of the first is 2191 m, and the second is 1753 m.

A large number of karst caves are also found in Europe. The most famous of them is the Moravian Karst (Czech Republic). Its underground karst deposits of Devonian limestone formed over 350 million years ago. It represents a whole area of ​​karst subsidence.

At the same time, one of the most popular caves among tourists remains the Postojnska Yama karst cave (Slovenia). Its total length is no more than 20 km, however, the Poika River flows through its underground territory, in the waters of which you can see unusual whitish fish without eyes.

Karst caves in Russia

Despite the variety of karst caves around the world, the largest and longest of them - Bolshaya Oreshnaya - is located in the Krasnoyarsk Territory.

One of the longest limestone caves in Russia is Botovskaya (Irkutsk region). Its length is about 60 km.

The deepest karst cave, Gorlo Barloga, is located in Karachay-Cherkessia and goes 900 m deep.

Caves of the Crimean Peninsula

Special attention should be paid to the Crimea, which has long been famous for its karst cavities.

Despite the fact that their formations occupy an impressive part of the peninsula, karst caves such as:

1. Red. The labyrinths of its passages occupy 6 floors with a vault height of about 30 m and a length of halls up to 80 m. It accounts for 1/3 of the area of ​​all formations of this type on the peninsula. The underground river Su-Uchkhan flows along the bottom of the cave, the vaults of which are decorated with extremely beautiful columns, stalagmites and stalactites.
2. Marble is located at an altitude of 1000 m above sea level. It got its name as a result of formation in marbled limestone. It contains the most beautiful cascades of lakes, placers of cave pearls and stone waterfalls.
3. Emine-Bair-Khosar occupies one of the first places among the world's natural phenomena. It represents more than 1,500 galleries and halls, a small fraction of which is equipped for tourists to visit. In this cave, you can see a unique collection of the remains of representatives of the wild fauna that inhabited the Crimean peninsula several million years ago.

Research Features

Underground waters gradually wash out and widen the cracks in the rock and begin to form galleries and grottoes. It is noteworthy that those karst caves, where water flows make more impressive paths for themselves, gradually expand and form an intricate system of underground passages, which can be located at various levels and connected by mines and wells of various depths.

Any person who decides to travel along the underground river must always remember that this is a very dangerous occupation. Despite the fact that most of the tunnels are quite wide, they gradually narrow in certain areas. At the same time, under the influence of the current, the boat can simply crash against the walls of the cave. In addition, tourists in such suits are also waiting for numerous rapids and waterfalls, as well as unexpected deep abysses. You can also get serious injuries by bumping into natural growths of rock: both protruding from the water and hanging from the ceiling. As a result, you can be knocked off the boat into icy water, which is fraught not only with bruises, but also with hypothermia. That is why, when exploring karst caves, you must be extremely careful and careful in order to keep only pleasant impressions from an unforgettable trip to these wonderful places.

Karst is understood as a geological process and related phenomena that develop as a result of the interaction of water with soluble rocks. These include zones in which the properties of rocks change, surface and underground karst forms, and karst deposits.

In the zones of changes in the water-physical and physical-mechanical properties of rocks, disintegration, brecciation, cavernousness and deconsolidation of rocks occur. On the surface of soluble rocks, negative corrosion forms are formed - niches, karr, funnels, hollows, fields, ditches, karst logs, ravines, valleys and canyons. Niches are recesses of various shapes and genesis on the slopes of karst massifs. Carr are microforms in the form of grooves, grooves, holes on horizontal or vertical surfaces of rocks. Closed, rounded, oval or irregularly shaped depressions up to 100 m in diameter, widening upwards, form funnels, and more than 100 m in diameter form depressions. Polya are closed or semi-closed forms of various sizes (up to 500 km2 in area), having a flat bottom and periodically flooded by karst waters. Karst ravines, ravines, valleys and canyons differ from one another in the steepness of the slope and the nature of the runoff absorption (from partial to complete). Ditches are elongated corrosion-gravity depressions with steep sides, usually oriented parallel to the crest of the slope. With selective dissolution, positive forms occasionally appear - remnants (towers, cones, etc.).

Underground karst forms include negative corrosion, corrosion-erosion or corrosion-gravity forms, having a width or height at the entrance less than the length or depth (caves, wells, mines). Caves are horizontal, inclined or complex (labyrinth) cavities in karst rocks with a cross section of more than 30 cm. Vertical cavities in karst rocks of a cone-shaped, cylindrical, slit-like or other complex shape up to 20 m deep are called wells; and with a depth of more than 20 m - mines.

Karst deposits - sediments of different genesis, composition and size - are formed in surface and underground karst forms (residual clay; landslide accumulations; water mechanical deposits; carbonate flour, breccia, calcareous tuff, stalactites, stalagmites, stalagnates, bark, cave pearls; bone material , ice, etc.).

One of the main conditions for the development of karst is the presence of carbonate, sulfate or salt rocks in the section of the earth's crust. According to their lithology, four subgroups are distinguished: I - strata of the same type of karst rocks; II - strata of interbedding of different types of karst rocks; III - strata of interbedding of karst and non-karst rocks; IV - interlayers of karst rocks among non-karst ones; seven lithological types: carbonate, sulfate, hydrochloric, carbonate-sulfate, terrigenous-carbonate, terrigenous-sulfate, carbonate-terrigenous; nine lithological types: limestone, dolomite, chalk, gypsum, rock salt, limestone-gypsum, terrigenous-limestone, terrigenous-gypsum, limestone-terrigenous.

According to the nature of the overlying deposits, the types of karst are distinguished: open (karsting rocks come to the surface or are covered with sedimentary unconsolidated deposits up to 2 m thick), covered (karsting rocks are covered with sedimentary unconsolidated deposits of various genesis with a thickness of more than 2 m), overlapped (karsting rocks are covered with sedimentary cemented deposits, igneous or metamorphic rocks of different thicknesses), overlapped-covered (karsting rocks are overlain by sedimentary cemented, igneous or metamorphic rocks and sedimentary non-cemented deposits of different thicknesses).

Separately, manifestations of hydrothermokarst are distinguished - the processes of dissolution of rocks, the formation and filling of karst forms and fluids. Hydrothermokarst, mainly in carbonate rocks, is associated with the formation of many deposits - lead, zinc, antimony, mercury, uranium, gold, fluorite, barite, celestite, Icelandic spar, bauxites, etc.
More than 60% of the territory of Russia is subject to the development of karst processes in rocks from the Archean-Proterozoic to the Neogene age. The most developed are terrigenous-carbonate (40%), carbonate-terrigenous (24%) and carbonate (14%) lithological types of karst.

The largest area (40.6%) is occupied by territories of a simple structure, where in the section there are overlapping karst rocks of one or two systems, 24% of the territory has a complex structure (3–5 systems); 2% - a very complex structure (more than five systems).
Karst rocks are more developed in the European part of Russia (72%), less - in the Asian part (64%). They are present in 70% of the permafrost area and in 33% of the area covered by Quaternary glaciation.

Caves. One of the most striking manifestations of karst is the caves. They are horizontal and inclined. The caves consist of galleries, halls (grottoes), meanders (winding galleries), narrow passages and manholes, organ pipes (going up from the gallery of usually blind wells), blockages (sections of the gallery with a collapsed vault). Large caves often form labyrinths: flat (without floors or laid in one layer) or three-dimensional (going to great depths). In flooded caves, there are lakes, streams, cave rivers with waterfalls and siphons (places where the river goes under the arch of the cavity). There are caves completely filled with water.

In the middle of the twentieth century. in Russia, about 350 small karst caves were known, the longest of which were considered in limestone - Vorontsovskaya (Western Caucasus, more than 5 km), and in gypsum - Kungurskaya (Urals, 4.5 km). There was no information about karst mines in Russia. As a result of active speleological research, more than 4 thousand natural cavities of various sizes and origins have been discovered to date, of which 141 belong to large caves more than a kilometer long and more than 100 m deep. ), in gypsum - Kulogorskaya-Troya (16.25 km, Arkhangelsk region), in conglomerates - Bolshaya Oreshnaya (47.0 km, Krasnoyarsk Territory). Most of the large caves are in the Greater Caucasus (35), in the Pinego-Kuloi (22) and South Ural regions (19).

The use of caves in the country is quite diverse. For industrial purposes, they are used to organize water supply; in medical - for treatment (for example, bronchial asthma in the underground workings of a potash mine in the Perm region); in sports - for various sporting events; in scientific - for geological, biological, archaeological and other research; in tourism as excursion objects (Kungurskaya, Kapova, Vorontsovskaya, Big Azishskaya caves, Sablinsky catacombs).

The Kungur Ice Cave is one of the largest caves in Russia. Its length is 5.7 km. The cave is located on the outskirts of the city of Kungur (Perm Territory) on the right bank of the Sylva River at the base of the slope of Ice Mountain. The entrance to the cave is located in a rock outcrop of Lower Permian gypsum, anhydrite and dolomite. The cave is a labyrinth formed in the slope part of the Sylva river valley. The average thickness of the roof is 65.0 m. Based on the theodolite survey conducted by E. P. Dorofeev, a plan of the cave was drawn up, which includes 48 grottoes (the largest are the grotto of Geographers, about 50 thousand m3, the grotto Velikan, about 45 thousand m3). The amplitude of the cave is 32 m, the area is 65.0 thousand m2; volume - 206 thousand m3. There are 70 lakes in the cave with a total area of ​​7.4 thousand m2 (the largest underground lake - Friendship of Peoples - with an area of ​​1,460 m2). In different seasons of the year, the number and size of lakes change. Kungur cave is famous for its ice formations. At the entrance to it, mainly congelation ice is developed, which occurs when water freezes (sinter, lacustrine, segregation, ice-cement and vein). ice is formed as a result of air exchange between and underground cavities or their individual sections. These are crystals (leaf-shaped, tray, pyramidal, rectangular, needle-shaped) and complex shapes (ensembles). Special observations have shown that the intensity of sublimation is 0.2 mm/day. (in the water layer). These ices have low mineralization and are sensitive to pollution.

Kapova cave (Shulgan-Tash) is located in the Republic of Bashkortostan and is part of the Shulgan-Tash nature reserve. This is one of the largest multi-storey caves in the Urals, 2,640 m long, an archaeological monument of world significance with Paleolithic paintings and ancient people's sites. It was formed in a karst massif on the right bank of the Belaya. The massif is composed of limestones of the Visean stage of the Lower Carboniferous. The entrance to the cave looks like an arch 48x18 m in size. The cave is a system of galleries, corridors and halls of north-north-west and north-east strike, located on three levels. The most significant halls (Chaos, Drawings, Diamond, Crystal) are formed on the middle and upper tiers. At the bottom, the Shulgan River flows (average water flow is 50 l / s), which disappears from the surface 2.5 km north of the cave. In the siphon part of the river, at the entrance to the cave, the depth reaches 30 m. The oldest is the middle floor of the cave, where the modern entrance to it is located. The cave is decorated with calcite sinter formations, in winter - with ice stalactites and stalagmites.

In 1959, the zoologist A. V. Ryumin discovered Paleolithic drawings of an ancient man in the cave, which brought her world fame. To date, more than 50 different types of colorful images of animals (mammoth, rhinoceros, bison), an anthropomorphic creature, paint spots and various geometric signs in the form of trapezoids, rectangles and triangles, made in ocher of various tones, have been found in the cave. The sizes of the drawings are from 6 cm to 1.06 m. They are placed in four halls: in the Dome, Signs and Chaos on the middle tier and in the Drawings Hall on the upper tier. The age of the drawings is at least 13–14 thousand years. Points, scrapers, notched tools, blades with a blunt edge, and some other tools made of local cave limestone and calcite, as well as flint and green-brown jasper, were found in the cultural layer on the middle tier of the cave. Many legends, legends, beliefs and fairy tales are associated with the cave.

Karst caves are underground cavities formed in the thickness of the earth's crust, in areas where readily soluble carbonate and halogen rocks are distributed. Being subjected to leaching and mechanical impact, these rocks are gradually destroyed, which leads to the formation of various karst forms. Among them, the most interesting are underground karst forms - caves, mines and wells, sometimes characterized by a very complex structure.

One of the main conditions for the development of karst caves is the presence of karst rocks, which are distinguished by significant lithological diversity. Among them are carbonate rocks (limestones, dolomites, writing chalk, marbles), sulfate (gypsum, anhydrite) and halide (rock, potassium salts). Karst rocks are very widespread. In many places, they are covered by a thin cover of sandy-argillaceous deposits or directly come to the surface, which favors the active development of karst processes and the formation of various karst forms. The intensity of karst formation is also significantly affected by the thickness of the rocks, their chemical composition and occurrence features.

As already mentioned, the builder of karst caves is water. However, in order for water to dissolve rocks, they must be permeable, i.e., fractured. Rock fracturing is one of the main conditions for the development of karst. If a carbonate or sulphate massif is monolithic and consists of solid rock varieties devoid of fracturing, then it is not affected by karst processes. However, this phenomenon is rare, since limestones, dolomites and gypsums are fissured in nature. Cracks that cut through limestone massifs have a different origin. Allocate cracks lithogenetic, tectonic, mechanical unloading and weathering. The most common are tectonic cracks, which usually cut through different layers of sedimentary rocks, without refracting during the transition from one layer to another and without changing their width. Tectonic fracturing is characterized by the development of complex mutually perpendicular cracks 1-2 mm wide. Rocks are characterized by the greatest fragmentation and fracturing in zones of tectonic disturbances.

Falling on the surface of a karst massif, atmospheric precipitation penetrates deep into this massif through cracks of various origins. Circulating through underground channels, water leaches the rock, gradually widens the underground passages and sometimes forms huge grottoes. Moving water is the third prerequisite for the development of karst processes. Without water, which dissolves and destroys rocks, there would be no karst caves. That is why the features of the hydrographic network and the peculiarity of the hydrogeological regime largely determine the degree of cavernousness of the karst strata, the intensity of leaching processes, and the conditions for the development of underground cavities.

The main role in the formation of many karst cavities is played by infiltration and inflation rain and snowmelt waters. Such caves are of corrosion-erosion origin, since the destruction of the rock occurs both due to its chemical leaching and mechanical erosion. However, one should not think that these processes proceed simultaneously and continuously. At different stages of the development of caves and in different parts of them, one of these processes usually dominates. The formation of some caves is entirely associated with either corrosion or erosion processes. There are also nival-corrosion caves, which owe their origin to the activity of melted snow waters in the zone of contact between the snow mass and karst rock. These include, for example, relatively shallow (up to 70 m) vertical cavities in the Crimea and the Caucasus. Many caves arose as a result of the collapse of the roof over underground corrosion-erosion voids. Some natural cavities were formed by leaching of rocks by artesian, mineral and thermal waters ascending along cracks. Thus, karst caves can be of corrosion, corrosion-erosion, erosion, nival-corrosion, corrosion-gravity (failure), hydrothermal and heterogeneous origin.

In addition to infiltration, inflation and pressure waters, condensation waters also play a certain role in the formation of caves, which, gathering on the walls and ceiling of caves, corrode them, creating bizarre patterns. Unlike underground streams, condensation waters affect the entire surface of the cavity, and therefore have the greatest impact on the morphology of the caves. Particularly favorable conditions for moisture condensation are characterized by small cavities located at a considerable depth from the surface, since the amount of condensation moisture is directly dependent on the intensity of air exchange and inversely on the volume of the cavity. Observations carried out in the Crimean Mountains showed that 3201.6 m 3 of water condenses in the studied karst caves during the year (Dublyansky, Ilyukhin, 1971), and in the underground cavities of the entire main ridge 2500 times more (i.e. 0, 008004 km 3). These waters are highly aggressive. Their rigidity exceeds 6 meq (300 mg/l). Thus, due to infiltration waters, the caves of the Crimean Mountains, as shown by simple calculations, increase by about 5.3% compared to the total volume. The average mineralization of condensation waters is about 300 mg/l, therefore, they carry out 2401.2 tons (8004 10 6 l X 300 mg/l) of calcium carbonate during the year. The total removal of calcium carbonate by karst springs in the Crimean Mountains is about 45,000 tons/year (Rodionov, 1958). Consequently, the role of condensation waters in the formation of underground cavities is relatively small, and their impact on the rock as a denudation agent is limited mainly to the warm period.

How is the process of leaching of karst rocks proceeding? Let us consider this issue in general terms using carbonate formations as an example. Natural waters always contain carbon dioxide, as well as various organic acids, with which they are enriched upon contact with vegetation and seepage through the soil cover. Under the action of carbon dioxide, calcium carbonate is converted to bicarbonate, which is much more readily soluble in water than carbonate.

This reaction is reversible. An increase in the content of carbon dioxide in water causes the transition of calcite into solution, and with a decrease in it, precipitation of calcium bicarbonate (lime sediment) from an aqueous solution occurs, which accumulates in some places in a significant amount. There is an inverse relationship between carbon dioxide content and water temperature.

The solubility of limestones increases sharply when groundwater is enriched with acids and salts. So, when groundwater is enriched with sulfuric acid, the reaction proceeds according to the equation

The carbon dioxide released as a result of this reaction is an additional source of hydrocarbonate formation.

The degree of solubility of gypsum and anhydrite also depends on the presence of certain acids and salts. For example, the presence of CaCl 2 in water significantly reduces the solubility of gypsum, on the contrary, the presence of NCl and MgCl 2 in water increases the solubility of calcium sulfate. The dissolution of gypsum can, in principle, also occur in chemically pure water.

Although we call carbonate and sulfate rocks easily soluble, they dissolve extremely slowly. It takes many, many thousands of years to form underground voids. At the same time, karst rocks dissolve and collapse only along cracks; outside the cracks, they remain very strong and hard as before.

Atmospheric waters penetrating into karst massifs along cracks and tectonic disturbances are initially characterized by a predominantly vertical movement. Having reached an aquiclude or a local basis of erosion, they acquire a horizontal movement and usually flow along the fall of rock layers. Part of the water seeps into deep horizons and forms a regional runoff. In this regard, several hydrodynamic zones are distinguished in the karst massif, namely, the zone of surface, vertical, seasonal, horizontal, siphon and deep circulation of karst waters (Fig. 1). Each of these hydrodynamic zones is characterized by a certain set of karst forms. Thus, vertical underground cavities - karst wells and mines - are confined to the zone of vertical water circulation or the aeration zone. They develop along vertical or gently sloping cracks as a result of periodic leaching of rocks by melted snow and rain waters. Horizontal caves are formed in the zone of horizontal circulation, where there is a free flow of non-pressure waters to river valleys or the periphery of a karst massif. Inclined and horizontal cavities are noted in the zone of siphon circulation, characterized by pressure waters that move in underflow channels, often below the local erosion base.

The development of caves, in addition to morphostructural and hydrogeological features, is also significantly influenced by climate, soil, vegetation, wildlife, as well as human economic activity. Unfortunately, the role of these factors in cave formation is currently far from sufficiently studied. It is to be hoped that this gap will be closed in the near future.

The theory of the origin of limestone karst caves developing in rocks with horizontal bedding was developed by W. M. Davis (1930). In the evolution of the so-called two-cycle caves, formed during the double uplift of the limestone massif, he distinguished five main stages: a) rudimentary channels formed in the zone of complete saturation of slowly moving phreatic waters under pressure; b) mature galleries, when mechanical erosion (corrasion) begins to dominate under the conditions of propagation of free-flow vadose flows; c) dry galleries, resulting from the departure of water into the depths of the massif due to local uplift of the territory; d) sinter-accumulative, characterized by the filling of galleries with sinter-drop and other cave deposits; e) destruction of underground galleries (peneplanization).

On the basis of the development of Davis's views, an idea was created about the phreatic (cave galleries are developed by groundwater under pressure) and vadose (groundwater freely, not under pressure, moves along the galleries towards drainage systems) stages of cave development (Bretz, 1942).

The questions of the evolution of underground cavities were most fully developed by Soviet researchers G. A. Maksimovich (1963, 1969) and L. I. Maruashvili (1969), who identified several stages in the formation of horizontal karst caves. The first stage is fissure, then crevice. As the width of cracks and crevices increases, an increasing amount of water penetrates into them. This activates karst processes, especially in areas of pure rock differences. The cave passes into the canal stage. With the expansion of channels, underground flows acquire turbulent motion, which favors an even greater increase in the processes of corrosion and erosion. This is the stage of the underground river, or vokluzovaya. It is characterized by a significant filling of the underground channel with a water stream and its exit in the form of an open source to the day surface, as well as the formation of organ pipes, the collapse of vaults, and the growth of grottoes.

Due to the erosion of the bottom of the underground channel, water seeps through cracks into the depths of carbonate and halogen strata, where it develops new cavities at a lower level, forming the lower floor of the cave (Fig. 2). Gradually, underground channels expand. The water flow partially and then completely goes into the lower horizons of the massif, and the cave becomes dry. Only infiltration water penetrates into it through cracks in the roof. This is a corridor-grotto scree-scree (water-gallery, according to L.I. Maruashvili) stage of cave development. It is distinguished by a wide distribution of chemical and mechanical accumulation (in gypsum caves, the stage of sinter accumulation is absent). The ceiling and walls of the cave are covered with various calcite deposits. Stone and earthen "talus" are formed, the latter are located mainly under the organ pipes. Sediments of rivers and lakes also accumulate. With the departure of the watercourse, the further increase in the underground cavity slows down sharply, although the corrosive activity continues due to infiltration and condensation waters.

As the cave develops, it passes into the corridor-grotto landslide-cementation (dry-gallery, according to L.I. Maruashvili) stage. At this stage, as a result of the collapse of the roof over the underground cavities, it is possible to open some parts of the cave. The gradual collapse of the cave roof leads to its complete destruction, which is especially typical for the upper parts with a small roof thickness. In the surviving areas, only karst bridges and narrow arches remain. With the complete destruction of the cave, a karst valley is formed.

If the thickness of the roof exceeds 100-200 m, then, as a rule, no dips are formed in it, and underground cavities are filled with blocks of rock that have fallen from the ceiling and brought sandy-argillaceous deposits, which break the cave into separate isolated cavities. In this case, the development of the cave ends with a corridor-grotto landslide-cementation stage (grotto-chamber stage, according to L. I. Maruashvili).

The duration of individual stages of the cave-forming cycle, which differ in their hydrodynamic and morphological features, the specifics of physicochemical processes and the peculiarity of bioclimatic conditions, is measured in tens and hundreds of millennia. Thus, the dry-gallery stage of the Kudaro Cave in the Caucasus has been going on for 200-300 thousand years (Maruashvili, 1969). As for the early stages of cave development (fissure, slit, channel and vault), their duration is much shorter. Caves "may reach a mature water-gallery state several millennia from the initial moment of their development." In this regard, experimental studies by E. M. Abashidze (1967) on the dissolution of crack walls in glauconite limestones of the Shaori reservoir (Caucasus) are of interest. Experiments have shown that for 25 years of continuous filtration, depending on the flow rate, hairline cracks of 0.1-0.25 mm in size can increase to 5-23 mm.

Thus, karst caves are characterized by a complex evolution, the features of which depend on a combination of various factors that often determine significant deviations from the considered scheme. The development of caves, for one reason or another, can stop or start again at any morphological and hydrological stage. Complex cave systems usually consist of sites at different stages of development. So, in the Ischeevskaya cave in the Southern Urals, there are now sections from the canal stage to the karst valley.

A feature of many caves is their multi-tiered, and the upper tiers are always much older than the underlying ones. The number of floors in different caves varies from 2 to 11.

The distance between two adjacent levels of multi-storey caves ranges from several meters to several tens. The collapse of the arches separating the cave floors leads to the formation of giant grottoes, sometimes reaching a height of 50-60 m (Krasnaya and Anakopiya caves).

G. A. Maksimovich connects the appearance of a new floor with the tectonic uplift of the area where the cave is located. N. A. Gvozdetsky assigns the main role in the development of multi-storey caves in conditions of high thickness of karst rocks to ascending movements, which he considers not as a disturbing factor, but as a general background for the evolution of karst. According to L. I. Maruashvili, the multi-tiered caves can be determined not only by the tectonic uplift of the karst massif, but also by the general lowering of the ocean level (eustasia), which causes an intensive deepening of river valleys and a rapid decrease in the level of horizontal circulation of karst waters.

Layering is best expressed in the caves of the plains and foothills, which are distinguished by relatively slow tectonic uplifts. During the formation of caves, sometimes there is a shift in the axis of cave galleries from the original vertical plane. The Tsutskhvatskaya cave is interesting in this respect. Each younger (of the four lower) tiers of this cave is shifted to the east relative to the previous one, and therefore the underground section of the Shapatagele River is currently located much to the east than during the formation of the higher tiers of the cave. The displacement of the axis of cave galleries is associated with the inclination of tectonic cracks, to which underground cavities are confined.

What is the age of karst caves and by what signs can one judge the beginning of the formation of the cave? According to L. I. Maruashvili, the period of its transition to the scree (water-gallery) stage should be taken as the beginning of the formation of the cave, since at the earlier stages of its development the cave is not yet a cave in the usual sense: it is poorly developed, completely filled water and completely impassable.

Various research methods are used to determine the age of the caves, including paleozoological, archaeological, radiocarbon and geomorphological. In the latter case, the hypsometric level of caves is compared with the levels of surface forms. Unfortunately, many of these methods only provide an upper limit on the age of a cave. Direct and indirect evidence proves the very long existence of karst caves, sometimes determined by many millions of years. Of course, the age of caves largely depends on the lithological composition of the rocks in which they are formed, and the general physical and geographical situation. However, even in easily soluble sulfate (gypsum, anhydrite) formations, caves remain for a very long time. Of interest in this regard are the gypsum caves of Podolia, the beginning of their formation dates back to the Upper Miocene. I. M. Gunevsky, based on the features of the geological structure of the territory, the degree of rock fracturing, the nature of the relief, the morphology of underground cavities and the structure of sinter formations, distinguishes the following stages of the formation of Podolsk caves: Upper Sarmatian (the beginning of intense deep erosion), Early Pliocene (characterized by the intensification of processes of the vertical direction ), Late Pliocene (horizontal groundwater circulation processes prevail over vertical ones), Early Pleistocene (cave formation processes reach their maximum intensity), Middle Pleistocene (underground karst formation processes begin to fade), Late Pleistocene (accumulation of mineral and chemogenic formations), Holocene (accumulation of blocky deposits). Thus, the age of the world's largest gypsum caves Optimistic, Ozernaya and Kryvchenskaya in Podolia apparently exceeds 10 million years. The age of limestone caves may be even more significant. So, some ancient karst caves of the Alai Range (Central Asia), which are of hydrothermal origin, according to Z. S. Sultanov, were formed in the Upper Paleozoic time, that is, more than 200 million years ago.

Ancient caves are found, however, relatively rarely, remaining for a long time only in the most favorable natural conditions. Most of the karst caves, especially in heavily watered sulfate rocks, are of young, predominantly Quaternary or even Holocene age. Of course, separate galleries of complexly constructed multi-tiered caves were formed at different times and their age can vary considerably.

For a quantitative assessment of karst cavities, G. A. Maksimovich (1963) offers two indicators: the density and density of karst caves. Density refers to the number of caves related to an area of ​​1000 km 2, and density is the total length of all cavities within the same conventional area.

J. Korbel proposed to characterize the size of karst caves with an indicator of voidness, calculated by the formula

Where V - the volume of soluble rock in which the cave is developed, in 0.1 km 3; L- distance (on the plan) between the extreme points along the main axis of the system of cavities - 0.1 km; J- the distance between the two most distant points along the perpendicular to the main axis - 0.1 km; H - the difference in marks between the highest and lowest points of the cave system is 0.1 km.

To determine the size of caves, there is also another method, which is associated with the calculation of the volume of cavities. If the cavity has a complex shape, then it should be represented as a set of various geometric shapes (prism, cylinder, full and truncated cone, full and truncated pyramid with a base of any shape, ball, etc.), the volume of which is calculated by the Simpson formula

Where v - the volume of the geometric figure, m 3; h - figure height, m; s1, s2, s3 - areas of the lower, middle and upper sections of the figure, m 2. Verification of this method by Crimean speleologists showed that errors in calculating the volume of cavities using the Simpson formula do not exceed 5-6%.

Karst caves

Cave- a natural cavity in the upper thickness of the earth's crust, communicating with the earth's surface by one or more outlets passable for humans. The largest caves are complex systems of passages and halls, often with a total length of up to several tens of kilometers. Caves are an object of study for speleology.

Caves can be divided according to their origin into five groups. These are tectonic caves, erosional caves, ice caves, volcanic caves, and finally, the largest group, karst caves. Caves, in the entrance part, with suitable morphology (horizontal spacious entrance) and location (close to water) were used by ancient people as comfortable dwellings.

Types of caves

Karst caves

Limestone, and even more so marble, dissolves very poorly with pure distilled water. Solubility increases several times if dissolved carbon dioxide is present in water (and it is always dissolved in water, in nature), but limestone still dissolves slightly, compared to, say, gypsum or, moreover, salt. But it turns out that this has a positive effect on the formation of extended caves, since gypsum and salt caves not only quickly form, but also quickly collapse.

A huge role in the formation of caves is played by tectonic cracks and faults. According to the maps of the explored caves, one can very often see that the passages are confined to tectonic faults that are visible on the surface. Also, of course, for the formation of a cave, a sufficient amount of water precipitation is necessary, a successful form of relief: precipitation from a large area should fall into the cave, the entrance to the cave should be located noticeably higher than the place where groundwater is discharged, etc.

The chemistry of karst processes is such that often water, having dissolved the rock, after a while deposits it back, forming the so-called. sinter formations: stalactites, stalagmites, helictites, draperies, etc.

The world's longest Mammoth Cave in the United States is embedded in limestone. It has a total length of passages of more than 500 km. The longest cave in gypsum is Optimistic, in Ukraine, with a length of more than 200 km. The formation of such long caves in gypsum is associated with a special arrangement of rocks: the layers of gypsum that enclose the cave are covered from above with limestone, due to which the vaults do not collapse. The longest cave in Russia is the Botovskaya cave, over 60 km long, laid in limestone, located in the Irkutsk region, the Lena river basin. Slightly inferior to it is Big Oreshnaya - a karst cave in conglomerates in the Krasnoyarsk Territory. The deepest caves of the planet are also karst: Krubera-Voronya (-2191 m), Snezhnaya (-1753 m) in Abkhazia. In Russia, the deepest cave is Gorlo Barloga (-900 m) in Karachay-Cherkessia. All these records are constantly changing, only one thing is invariable: karst caves are in the lead.

Tectonic caves

Such caves can arise in any rocks as a result of the formation of tectonic faults. As a rule, such caves are found in the sides of river valleys deeply cut into the plateau, when huge rock masses break off from the sides, forming sagging cracks (sherlops). Seizure cracks usually wedge together with depth. Most often they are covered with loose deposits from the surface of the massif, but sometimes they form rather deep vertical caves, up to 100 m deep. Sherlops are widely distributed in Eastern Siberia. They are relatively poorly studied, and probably occur quite often.

erosion caves

Caves formed in insoluble rocks due to mechanical erosion, that is, worked out by water containing grains of solid material. Often such caves are formed on the seashore under the action of the surf, but they are small. However, the formation of caves, worked out along the primary tectonic cracks by streams going underground, is also possible. Quite large (hundreds of meters long) erosional caves are known, formed in sandstones and even granites.

Glacial caves

Another type of glacial caves are caves formed in a glacier at the point where intraglacial and subglacial waters exit at the edge of glaciers. Meltwater in such caves can flow both along the glacier bed and over glacial ice.

A special type of glacial caves are caves formed in a glacier at the point where underground thermal waters come out. Since the water is hot, it is able to make voluminous galleries, however, such caves do not lie in the glacier itself, but under it, since the ice melts from below. Thermal ice caves are found in Iceland, Greenland and reach considerable sizes.

Volcanic caves

These caves are formed during volcanic eruptions. The lava flow, cooling down, is covered with a solid crust, forming a lava tube, inside of which molten rock is still flowing. After the eruption has already, in fact, ended, the lava flows out of the tube from the lower end, and a cavity remains inside the tube. It is clear that lava caves lie on the very surface, and often the roof collapses. However, as it turned out, lava caves can reach very large sizes, up to 65.6 km in length and 1100 m in depth (Kazamura Cave, Hawaii).

The deepest caves in the world

Longest caves in the world

The largest caves in the territory of the former USSR

Speleofauna, environmental issues

Although the living world of caves, as a rule, is not very rich (excluding the entrance part, where sunlight enters), nevertheless, some animals live in caves, and in caves at that. First of all, of course, these are bats, many of their species use caves as a daily shelter or for wintering. Moreover, bats fly, sometimes, into very remote and hard-to-reach corners, perfectly orienting themselves in narrow labyrinth passages.

In addition to bats, in some caves, in areas with a warm climate, several species of insects live, spiders ( Neoleptoneta myopica), crayfish, shrimp ( Palaemonias alabamae), salamanders and fish ( Amblyopsidae). Moreover, cave species adapt to complete darkness, lose their sight. Often these species are very rare, endemic.

archaeological value

Primitive people used caves all over the world as a dwelling. Even more often, animals settled in the caves. Many animals died in the cave-traps, starting from steep wells. The extremely slow evolution of caves, their constant climate, and protection from the outside world have preserved a huge number of archaeological finds to us. These are the pollen of fossil plants, the bones of long-extinct animals (cave bear, cave hyena, mammoth, woolly rhinoceros), rock paintings of ancient people (Kapov caves in the Southern Urals (drawings), Divya in the Northern Urals (cave bear), Tuzuksu in the Kuznetsk Alatau ), tools of their labor (Strashnaya, Okladnikova, Kaminnaya in Altai), human remains of different cultures, including Neanderthals, up to 50-200 thousand years old (Teshik-Tash cave in Uzbekistan, Denisova cave in Altai, Cro-Magnon in France and many others).

In culture

The cave has an important symbolic meaning.

Notes

Links

• Caves of Kugitang (Turkmenistan) Cap-Kutan system. Photo tour and some literature.
• B. Mavlyudov. Reflections on ice in caves
• Caves of the Perm region. Ordinskaya cave. Cave Diving

Wikimedia Foundation. 2010 .

Karst caves

The dissolution (leaching) of certain rocks causes a number of phenomena that are called karst or, in a word, karst. These phenomena were first studied on the Karst lime plateau in Yugoslavia. They are found where soluble rocks are common: rock salt, gypsum, chalk, limestone, dolomite. Surface and underground waters leach large and small cavities in them, which often have bizarre shapes, forming caves, dips, grottoes.

When the roof collapses over the karst voids or the rocks lying from the surface are leached, peculiar relief forms appear - karst. Of these, the most common funnels of various sizes and shapes, hollows and dips; car-ry - recesses, ditches, cracks, furrows that cut through the earth's surface.

Under the influence of karst, many amazing phenomena occur: rivers, streams, lakes disappear (literally fall into the ground); some rivers suddenly "emerge" to the surface; on the seabed, fresh water flows from karst cavities. It is believed that some legends about suddenly disappearing cities (say, about the invisible city of Kitezh) arose under the influence of karst failures into which buildings collapsed. Such phenomena are not uncommon in areas where karst is developed.

The study of karst is associated primarily with practical needs: the construction of cities and individual structures, the operation of railways, etc. Karst failures, for example, have repeatedly occurred near the railroad track on the Moscow-Gorky line. One of the funnels had a diameter of 50 m. It took 15 wagons of soil to fill it. Even more trouble is caused by karst failures in cities. There are cases when houses fell into karst cavities, and entire neighborhoods were destroyed. So, in Johannesburg (South Africa) at the end of 1962, a whole factory disappeared underground, in a failure, and later - a residential building. Apparently, these dips arose as a result of large pumping of groundwater. Stability was broken in karst cavities, in dolomites and limestones lying under the city.

It is very difficult to carry out hydraulic engineering construction in karst areas.

Despite this, construction is underway in karst areas. Thus, the Pavlovskaya hydroelectric power station on the Ufa River, Kakhovskaya on the Dnieper and many other dams are located in places where karst is developed. But here, even before the start of construction, geographers and geologists worked to study the karst and suggested measures to combat it. After all, despite all the "cunning" of karst, it can be successfully dealt with. For example, to inject cement through wells into underground voids or “heal” funnels with soil.

Karst greatly complicates underground work: driving mines, adits, tunnels. Often underground streams and rivers flow in karst voids, there are underground lakes. But underground, karst can also become a human helper: speleologists (cave explorers) manage to penetrate hundreds of meters into the depths of mountains through karst caves.

Karst caves are wonderful creations of nature. Fanciful labyrinths, galleries; majestic grottoes and "bottomless" abysses; stone "icicles" of stalactites and stalagmite columns; turbulent streams, waterfalls and the quietest lakes; special fauna and fragile crystalline formations - all this is found in karst caves. Some of them are very large. In the Middle Transnistria, the length of the Lake Cave is 21.6 km, and the Main (Crystal) Cave is 18.8 km. The famous Kungur cave in the Cis-Urals is 4.6 km long; it has more than 30 lakes. The largest cave is Mammoth (USA, Kentucky); the total length of all its branches is 240 km. There are many caves in the Caucasus, in the Crimea. In the summer of 1979, Soviet speleologists, who explored the Caucasian cave Snezhnaya, descended to a depth of 1190 m. The world's deepest karst failure is the cave of Pierre-Saint-Martin in France (1332 m).

Karst is ancient and modern. In the Volga valley, on the Samarskaya Luka, one can see karst forms formed more than 150 million years ago. This is an ancient karst. Modern karst processes have different intensity. And yet their speed, in general, is not very high. Over the years and decades, a large karst cavity, or karra, cannot form. So the age of most modern karst forms is many thousands or even millions of years.

For the formation of karst, the presence of soluble rocks is still not enough. Of great importance are the depth of groundwater (the lower their level, the deeper the karst forms), the chemical composition of surface and groundwater, relief, climate, as well as human activities (mining, construction, hydraulic structures, etc.). Therefore, it is very difficult to study karst, its causes, features and methods of dealing with it.

Karst is found in many vast areas of our country: in the Central Russian and Volga Uplands, in the basin of the Oka, Klyazma, the upper reaches of the Dnieper and Don, in the Volyn Upland, in the Baltic States, on the O-Dvina watershed, in the northern part of Belarus, in the Carpathians and Transcarpathia, in the Crimea and the Caucasus, in the Caspian lowland, in the Urals and in the Cis-Urals. Karst is also widespread in Eastern Siberia, in the Western Baikal region, in Primorye and the Amur region, in Kazakhstan and Central Asia. It has been studied in the most detail in the European part of the country. However, even here, in many areas, it has not yet been studied well enough.

A young local historian can learn about the existence of karst in a given area from the stories of local residents and specialists, as well as from landforms, caves, etc.

Karst can be detected by characteristic landforms (karr, sinkholes); along disappearing streams and rivers; in areas where the amount of water in the river decreases or sharply increases; major groundwater sources. In large karst depressions and karst ravines, heavily overgrown small sinkholes are not uncommon, which are not easy to notice. However, it should be remembered that it is precisely such pockets of dense vegetation that indicate the existence of sinkholes here.

It is necessary to examine karst landforms very carefully, keeping in mind the possible encounter with deep karst wells, dips; one cannot act alone, without the participation of experienced senior comrades, teachers. It should be limited to the inspection and measurement of karst landforms from the surface (without descending into dips, caves). Conduct an eye survey of the areas of their distribution, plot these areas on small-scale maps and diagrams. Particular attention should be paid to damage to roads and individual structures due to karst manifestations. Karst caves are very dangerous: it is easy to get lost in them; in addition, deep karst wells and abysses are often found in them.

Source: yunc.org