The most amazing caves in the world

Always associated with caves a large number of secrets and mysteries, because this is a whole world of magic, silence and silence. Even in ancient times, caves were used to shelter humans and animals, and some were even considered the abode of the gods. In nature, there are no two identical caves, because some have lakes, others have halls with grottoes, wells, glaciers and waterfalls. For many thousands of years, rainwater has destroyed the stone, forming stalactites and stalagmites of bizarre shape. In some caves, calcite is formed in the form of pearls, flowers, thin twigs, crumbling at the slightest touch. We present to your attention a rating of the most amazing and beautiful caves in the world.

1Giant Crystal Cave, Mexico

A cave of giant crystals in Mexico was discovered by ordinary miners who were working in the south of the country. At the depth of a three-hundred-meter mine, they discovered a cave, literally strewn with huge crystals from the inside. The crystals in the caves are translucent, and their color varies from bright white to golden. The crystals are rectangular or cylindrical in shape, and their length reaches several meters. The base of the cave is stone, which speaks of its ancient origin. The huge crystals in it were formed by nature over several million years. Apparently, the room of the Crystal Cave was previously filled with rock, which was gradually washed away by underground waters, after which such unusual formations remained.

2. Na Pali Coast Cave in Kauai, Hawaii

The Hawaiian island of Kauai was formed over 5 million years ago as a result of volcanic activity in the area. One of the most spectacular sights of the island is the coast of Na Pali. Here, the rocks practically hang over the sea, and exotic plants grow on their surface and various birds nest. In addition to picturesque volcanic mountains and evergreen beaches, tourists are attracted here by mysterious caves. For many centuries, sea waves methodically carved volcanic rocks, thus forming the caves of Hawaii. In the caves you can enjoy virgin nature and sea views.

3. Melissani Cave, Greece

The Melissani cave, located on the Greek island of Kefalonia, was forgotten for several centuries and remembered only in 1951, when the Greek Giannis Petrohelios again found and opened it. After all, even in Greek mythology this cave was mentioned as the dwelling of the nymphs. The reason for such a violent fantasy of the ancient Greeks is quite understandable - the cave with its turquoise lake surrounded by dense forest looks truly fabulous. Melissani cave has a stone base, on which there are shallow azure waters, at the top there is a huge stone dome with a huge hole through which it enters deep into the cave sunlight, creating amazing highlights on its walls. The entrance to the Melissani cave is also very picturesque - it is overgrown with greenery, and the "door" is decorated with natural brownish stone "plaster".

4. Skocjan Caves, Slovenia

One of the most famous karst cave systems on our planet is the Škocjan Caves. On the beautiful Kras Plateau, located in the southwest of Slovenia, these wonderful caves are located, officially recognized as a reserve and object world heritage. Shkocyansky caves owe their appearance to the local river with the name "River" flowing through it, which for centuries "cut down" the caves in karst deposits. However, as a result of water erosion, several arches of the cave collapsed, forming karst failures "Mala Dolina" and "Velika Dolina", separated by a natural bridge. On the territory of Velika Dolina, the River goes underground, appearing on the surface after 34 kilometers already in Italy. In addition, there are many dangerous funnels, dips and small waterfalls on the territory of the Shkocyan Caves. The largest European grotto, the Martel Hall, is also located in the caves.

5. Marble Caves in Chile Chico, Chile

High in the Andes is one of the deepest lakes in the world - Lago General Carrera (Chilean name) or Lago Buenos Aires (Argentinean name), since the lake is located on the border of Chile and Argentina. Not far from the Chilean city of Chile Chico are the famous Marble Caves. Although the walls of the caves are not made of marble at all, but of limestone, but against the background of turquoise water, its vaults, which have white and blue tones of color, look very impressive. Thanks to this natural beauty, thousands of tourists come to see the Marble Caves every year. Small pleasure boats bring tourists here, allowing you to see all the splendor of the shades of the cave, as well as look into the natural windows, as if melted in the walls of the labyrinth of the Marble Caves - boats can no longer drive there. In addition to the amazing Marble Caves, fishing lovers also come to the lake, because its waters are rich in trout and salmon, as well as some other types of fish.

6. Mammoth Cave in Kentucky, USA

Mammoth Cave is located in US state Kentucky. This unique karst cave has a unique microclimate. The cave was discovered about 4,000 years ago; the remains of ancient torches are still found in it. The cave was used by local tribes for various purposes. American scientists have discovered the mummy of a man who died in this cave more than 2,000 years ago. After numerous studies, scientists came to the conclusion that a person was engaged in the extraction of gypsum here. Found in an underground river rare view shrimp, crayfish and blind fish. In addition, flocks of bats live in the cave. Since the end of the 19th century, Mammoth Cave has become a tourist attraction, for which purpose electric lighting. However, if you wish, you can walk through the cave as in ancient times - with a paraffin lamp.

7. Cenotes of the Yucatan Peninsula, Mexico

Cenotes are peculiar formations in caves that appear in the rocks under the influence of water. South of the Mexican resort of Cancun, located on the Yucatan Peninsula, is one of the most beautiful cenotes. According to some reports, in ancient times Yucatan was an underwater reef. After the water left, huge caves remained. The caves and grottoes of the Yucatan are completely underground. There are no land rivers on the peninsula - they all flow underground. Once upon a time, the Mayan peoples considered cenotes sacred and drank water from them during religious ceremonies. Tourists from all over the world come to the Yucatan to swim, dive and admire the underground scenery. And ancient stalactites and stalagmites make undersea world truly fabulous. Through the cracks of the caves, sunlight penetrates into the cenotes, giving them a special beauty.

8. Blue Caves, Greece, Zakynthos Island

On Zakynthos, one of the largest Greek islands, there are amazing Blue Caves. Among tourists, the island has gained popularity due to its scenic area, including beaches and villages. In the village of Volimes is located the Blue Cave, which can only be reached through the sea, however, as well as to most of the island. If you visit the Blue Cave at sunset or sunrise, you can enjoy the blue color of the sky and ocean reflected in it. For many years of water erosion, the rocks have taken on the appearance of amazing natural arches. Due to the unusual light effects of the Blue Caves, this place is one of the most visited in Greece. In addition to the beautiful caves, Zakynthos has a famous beach, considered one of the best in the world.

9. Fingal's Singing Cave, Scotland

For many centuries on the island of Staffa (the island belongs to the group of the Inner Hebrides) in Scotland, the rains and the sea have formed one of the largest caves in the world - Fingal's Singing Cave. The cave owes its name to the famous Scottish poet James MacPherson. According to legend, the giant Fingal, in order to connect Scotland and Ireland, built a dam, along which a huge giant passed into his dwelling, while Fingal lay down to rest before the fight with him. However, his wife was resourceful and said that it was the baby, the son of Fingal, who was sleeping. The huge giant imagined the size of the father of this "baby" and fled in fear, destroying the dam behind him. According to legend, Staff Island is part of this dam. The second reason for this name of the cave is the Geltian meaning of the phrase "Cave of Melodies". The name was given to the cave due to the fact that during the surf, the cave hall repeatedly repeats the sounds of the sea, as if singing!

10 Skaftafell Ice Cave, Iceland

On the edge of glaciers, amazingly beautiful structures are often formed - ice caves. In Iceland, on the lagoon of the Svinafellsjokull glacier, there is the famous Skaftafell Cave. Over the past centuries, the glacier has compressed so much that it has almost no air bubbles, due to which almost all sunlight is absorbed, except for the blue fraction visible inside the cave with the naked eye. Although such blue ice can only be washed away upper layer glacier, for example, in winter. However, such light is found in floating icebergs and other ice caves. Skaftafell cave has a seven meter entrance on the shore. At the end of the cave narrows to one meter. However, it is not safe to visit ice caves, as they are constantly transforming and can collapse at any moment. Only in winter visiting such caves is relatively safe. As ice caves move with the glacier, crackles can often be heard inside them.

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 under the influence pure water dissolves very badly. However, if the water contains increased amount 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. characteristic feature is an irregular or cone-shaped 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 - 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 1500 galleries and halls, a small fraction of which is equipped for visiting tourists. 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 the streams of water make their own more impressive paths, gradually expand and form an intricate system. underground passages, which may be located on various levels and connected by shafts 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 shot down from a boat in ice water, which is fraught with not only bruises, but also 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 caves are underground cavities formed in the thickness 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 features of occurrence.

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 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, soils, vegetation, animal world, and economic activity person. 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 most complete questions of the evolution of underground cavities were 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 the combination of the most various factors, which 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 on Southern Urals at present, there are sections from the canal stage to the karst valley.

A feature of many caves is their multi-tiered, and upper tiers always much older than those below. 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 early stages in its development, the cave is not yet a cave in the usual sense: it is poorly developed, completely filled with 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 fracturing of rocks, 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 ( middle 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 in different time and their age can vary considerably.

For quantification karst cavities GA 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 - volume 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%.