What is a cave definition. How are caves formed? Hypothesis about the origin of karst areas

Caves are the last unexplored frontier of our planet, mysterious world, which only the most desperate daredevils dare to look into. Labyrinths stretch for miles under our feet underground caves and tunnels. Today the caves remain the most little explored places on the planet, and yet people rarely manage to descend into the dark dungeons first. The strangest and least known animals on Earth already live here...

Postojna Yama, Slovenia
Caves can be divided according to their origin into five groups. These are tectonic caves, erosion caves, ice caves, volcanic caves, and, finally, the most large 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.

Most of these caves. It is karst caves that have the greatest length and depth. Caves are formed due to the dissolution of rocks by water. Therefore, karst caves are found only where soluble rocks occur: limestone, marble, dolomite, chalk, as well as gypsum and salt.
Limestone, and even more so marble, dissolves very poorly with pure distilled water. The solubility increases several times if dissolved water is present in the water. carbon dioxide(and it is always dissolved in water, in nature), however, 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.

Leak formations in Katerloch Cave, Austria.

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 widespread in Eastern Siberia. They are relatively poorly studied, and probably occur quite often.

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.

Lava cave, Hawaii.

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 long and 1100 m deep (Kazumura Cave, Hawaiian Islands).

A typical gallery in Mammoth Cave, Kentucky.


It's funny, but mammoths have never been found in the cave. Just English word mammoth also means "huge". Back in the 19th century, this cave was discovered in Kentucky under the Flint Ridge. At first, saltpeter was mined in it, but one day the deposits were depleted and a certain entrepreneur bought that place. With the help of servants, he tried to explore the depths of the dungeon, but failed. By the beginning of the 20th century, as many as 5 tiers and more than 200 grottoes, galleries and passages were discovered in the cave. Their total length was as much as 500 kilometers! End of this underground country so still not found. But the Mammoth Cave cannot boast of special beauties or miracles. Its arches consist of red limestone, which practically does not form streaks, so there are fewer figured stalactites than in other caves, much more modest in size. Although the visual range is poor, the places are called loudly - one of the corridors is called Broadway, and the underground river is called Styx. However, there is something that guides are happy to demonstrate to guests - stone sculpture, reminiscent of the profile of the mother of President George Washington. So that tourists do not leave their autographs on the walls, they are given a special Hall of Records. Respectable guests can leave not a wall inscription, but a respectable business card. From largest city Kentucky, Louisville can be reached by car in 4-5 hours, and the closest city in the cave is the city of Brownsville

241,595 m - length -192.6 m - depth

232,000m-length -15.0 m-depth All speleologists in the world know the Optimistic Cave, and it is not surprising - in terms of the length of the labyrinth, this is the largest cave on the continent and the second largest in the world after the American system Flint-Rich and Mammoth.


218 450m-length -193.9m-depth (Wind Cave), cave in the north in the north-east. foothills rocky mountains(Black Hills Mountains), South. Dakota (USA). Entrance at the bottom of Wind Cave Canyon. Known since 1881. The natural entrance has a diameter of 0.35 m; a shaft with an elevator was built for sightseers. A voluminous labyrinth with a dense network of galleries. The length is over 120 km, the elevation difference is 172 m. The cave is worked out in limestone thermal waters rich in minerals. Equipped for excursions.

209 600m-length -488.9m-depth Lechuguilla (eng. Lechuguilla) - a cave in the national park carlsbad caves. One of the longest caves in the world (210 km) and the deepest cave in the continental United States (−489 m). The cave is unique in its origin and variety of crystalline mineral deposits. The name of the cave corresponds to the name of the canyon in which the entrance is located, and that, in turn, is named after the Latin name of the common local species agaves (Agave lechuguilla).

183 600 m-length -108.5 m-depth (Fisher Ridge), labyrinth-type karst cave in the ridge. Fisher in zap. foothills of the Appalachians, Kentucky (USA). Has three entrances. The length is more than 113 km, the height difference is 60 m. Numerous int. wells connect a multi-level complex of galleries. The river is drained. Green River. Known since 1981. The edge passages are only 250 m east of mammoth cave. Visited by natives 800-1200 years ago.
Ox Bel Ha,Mexico
182 150 m-length -33.5 m-depth Bull Bel Ha (Mayan meaning "three ways of water"; officially System Ox Bel Ha) is a cave system in Quintana Roo, Mexico. It is the longest explored underwater cave in the world.

175 664 m-length -355.1 m-depth

- a cave in the Western Caucasus, which is the second deepest cave in the world (-1753 mi, considered the most difficult in the territory of the former USSR and the most difficult siphon-free cave in the world. It is located in one of the spurs of the Bzybsky ridge in the thickness of reef Jurassic limestones.

Three large underground waterfalls: Irkutsk (the height of the two knees of the waterfall is 45 m), Record (25 m) and Olympic (32 m). A giant blocky collapse in the bottom part is the blockage of the Metrostroy, 127 m high. Most of The route to the bottom part runs along an underground river (the length is more than 7 km, the water flow in low water is from 50 l/s in the upper reaches, up to 200 l/s in the bottom part). The Diamond Gallery is a side passage of the cave at a depth of 750 m, covered with large gypsum crystals for 100 m. Flower way - a passage in a blocky blockage, covered with white crystals

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New Athos cave is a formation in karst rocks in Abkhazia, it is included in the list giant caves in the world.
The ancient abyss on the side of the mountain is called the abyss by many, it was studied in 1961. mini-expedition (4 people). Soon the New Athos cave gained fame, and tourists began to head towards it.

The New Athos cave consists of 9 large cavities, where tourists come. They are attracted by interesting formations inside, similar to skulls, figures, etc. The New Athos cave is interesting, as we have already said, for its size, as well as the legends associated with it, for example, that angels once lived in it.

Big Oreshnaya Cave is largest cave Russia by the length of passages and the volume of underground spaces. This is the largest conglomerate cave on the planet. The conglomerates consist of boulders and pebbles of variously colored limestones and dolomites cemented with reddish-brown calcareous sandstone. They are of variable strength and porosity, subject to dissolution and collapse, to the point of becoming a sticky, reddish brown, sandy clay.

- a cave in the Urupsky district of the Karachay-Cherkess Republic. The most deep cave in the territory Russian Federation. Depth - about 900 m. Length - about 3000 m. (The cave has not been fully explored, so these figures can be increased).
The entrance to the cave is located in the upper reaches of the river. Atsgara, which is the first right tributary of the river. Urup is a hole in the ledge of a ruined limestone rock ledge. The absolute height mark of the entrance is 2825 m above sea level.
Discovered and first examined in August 1994 by a group of speleologists from Rostov-on-Don, Cherkessk and Donetsk

Genetically, the cave can be attributed to the class of corrosion-erosion caves. Morphologically, it is a series of wells (the most significant is the Grand Prix, 65 m deep), alternating with small sub-horizontal passages. Starting from a depth of -630 m (from the Magnitny Hall), the path through the cave runs through the blockage with a vertical amplitude of about 200 m. ).

Ordinskaya cave - located on the eastern outskirts of the village of Orda Perm Territory, on the left bank of the river. Kungur. It is embedded in gypsum and anhydrite of Permian age. Consists of "dry" and underwater parts. The length of the dry part is 300 meters, underwater - 4600 meters. To date Orda cave is the longest flooded cave in Russia. In addition, part of the cave is the longest siphon in the CIS - 935 meters.

The Orda Cave is located in the bowels of Kazakovskaya Gora, a hill with a plateau-like flat top, skirted by the Kungur River. The height of the hill does not exceed 50 m. On its surface there are large sinkholes, in one of which, located on the southern steep slope, is the entrance to the cave

Dolganskaya Yama and Dolphin caves are wintering grounds for bats. Here is the most numerous [source not specified 83 days] colony of wintering bats in Siberia (more than 2000 individuals).
The Dolgan karst system is the only known complex of voids in Russia in permafrost with a year-round positive temperature. It is a testing ground for geological, biological, paleontological, hydrogeological, glaciological, microclimatic and geomorphological observations. Studied since late 1970s

Rock paintings in Lascaux cave, France.
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 pollen of fossil plants, bones of long-extinct animals (cave bear, cave hyena, mammoth, woolly rhinoceros), cave drawings ancient people (caves Kapova in the Southern Urals, Divya in the Northern Urals, Tuzuksu in the Kuznetsk Alatau), tools of their labor (villages Strashnaya, Okladnikova, Kaminnaya on Altai-human remains of different cultures, including Neanderthals, up to 50-200 thousand years old ( cave Teshik-Tash in Uzbekistan, Denisova cave in Altai, Cro-Magnon in France and many others).
Water, as a rule, is found in many caves, and karst caves owe their origin to it. In the caves you can find drops, streams and rivers, lakes and waterfalls. Siphons in caves often complicate movement, require special equipment and special training. Often there are underwater caves. Air in the caves
In most caves, the air is breathable due to natural air circulation, although there are caves in which you can only be in gas masks. For example, guano deposits can spoil the air. cave deposits
There are mechanical (clay, sand, pebbles, boulders) and chemogenic deposits (stalactites, stalagmites, etc.).
Some caves are equipped for visiting tour groups(the so-called showcavesFor this, in the part of the cave, the most spacious and rich sinter formations, walkways, ladders, bridges are laid, electric lighting is created, in some cases, if the entrance part of the cave is a technically difficult area, tunnels are made. On the territory of the former USSR, the most famous caves are Marble in the Crimea, Kungurskaya in the Urals, Novoafonskaya in Abkhazia.

All the beauty opens up if you go down a little below the recession of the water, where a narrow valley of decent depth has formed, from which you can see the holes leading to the Sablinsky caves. Surprising is the fact that all Sablinsky caves are of anthropogenic origin, looking at them, it is impossible to assume this. However, this is true - the Sablinsky caves were created in the process of making glass, they were dug out, because the glass industry needed a lot of sand. This explains the similarity internal device, which, by the way, does not detract from their merits at all.

This cave complex also includes Pigeon Cave and Yale Coba. Once, in 1825, this cave was visited by the famous Russian playwright A.S. Griboyedov, one of the lower corridors of the cave is named after him.

One of the most beautiful and famous caves in the CIS are

Kungur caves, so named because of the city of Kungur, located in Perm region. The Kungur caves are the real dwelling of the Snow Queen - covered with ice and hoarfrost, they leave an indelible impression of themselves.


Kungur caves attract many tourists, who later tell about huge icicles, about feeling like in a real fairy tale, about how, opening their mouths with admiration, they wandered along the passages.


Kungur cave is one of huge caves on Earth and the only cave in the Russian Federation specially designed for tourists. This incredible natural object, surrounded by many legends, is located in the Urals, between Perm and Yekaterinburg. Researchers claim that the Kungur cave is almost 10-12 thousand years old.

Kapova cave is located in old rock in Bashkortostan, where ancient drawings dating back to the Paleolithic have been preserved. The Kapova Cave was first discovered in the middle of the 18th century, but it was examined in detail already in the middle of the 20th century, when huge galleries with cave paintings were found.


The age of this cave with an underground river is more than 2 million years. It was discovered and explored by the leader of the Maori tribe, Tane Tinorau, and the English surveyor Fred Mays in 1887.





Salt caves have been known for a long time, but it was in the UK that the first artificial salt cave.
The gentle sounds of the waves on the shore, the reassuring rustle of sand under your feet, the invigorating freshness of the salty air. Closing your eyes, you can imagine yourself on the beach. Open them and look around - there is a salt cave around you, and you are not sitting on sand, but on salt, salt on the walls, and in the air, and everywhere.

Dolgorukov massif


The caves are a system with a length of 2.5 km and are not deep, only 25 meters. Opened by the founder of speleology Edouard Alfred Martel.


In 1935, classical music concerts began to be organized here, after lighting was installed and an electric imitation of dawn over water was created.

Along with the usual route to Cango, you can also take the so-called "Adventure Tour" through hard-to-reach passages.

There are over 150 limestone caves in Bermuda, but the most famous are the Crystal Caves. They got their name from the crystal clean water flowing under their vaults. The water is so clear that you can even see the bottom of the caves, the depth of which sometimes reaches 17 meters.
It is believed that the caves were formed during ice ages when the sea level was 100-130 meters lower. Rain water seeped through the soil, and the resulting underground stream with high acidity dissolved the limestone. As a result of this process, voids appeared in the caves. The dripping water formed stalactites and stalagmites.
When the water level in the seas rose, these voids were filled sea ​​water, and the formation of caves stopped.

This cave system located in the Blue Mountains. The natives call them "Binumea" - which means "Dark Places". They believed in the healing properties of the water of the underground river and brought sick people here.


The widest and highest cave "Lukas" is the most visited. The entrance fee to each cave is taken separately, and than harder route- the more expensive.

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A real underworld - this is how you can describe the cave of the Yellow Dragon, which is located in famous nature reserve Zhangjiajie. Lighting is installed everywhere here, which gives this place a simply unreal look. One gets the impression that you are visiting some fairy-tale character.
The cave itself is very large, with several levels, each with its own unique illumination. At the bottom there is a river that you can go down by boat. We are sure you will remember this trip for the rest of your life!

The cave is located in a remote area of ​​the Selma plateau, about 1600 m above sea level, in Oman. It was discovered in 1983 by Don Davidson, a geologist who studied water resources. Davidson died ten years later, leaving Oman for good to go hiking in the Andes. He rented a car and left a note saying where he was going. Nobody ever saw him again.


By the name of the limestone plateau "Kras" (Karst) in Slovenia are called all the karst caves in the world. Included in the UNESCO World Heritage List, the Škocjan Caves are the most enchanting sight on this plateau.


Majestic karst grottoes, 30 waterfalls and a 2.5 km deep underground gorge are part of this cave system. Its total length is 6 km.

Here you can see: fantastic calcite columns and stalagmites in the Cave of the Winds, and underground river 108 km long in the "Pure Water Cave".


IN " Deer Cave", thanks to a hole in the ceiling, a piece of land appeared covered with lush vegetation, illuminated by the sun. This place is called -" Garden of Eden ".

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"Giant ice world"- this is the name of this cave system, which is located 40 km from Salzburg, translated from German. They were first explored in 1879 by scientist Anton Posselt. Since then, the Eisriesenwelt caves have become one of the most popular tourist spots, which is visited annually by about 200 thousand people.


Pride national park USA in New Mexico - Carlsbad Caves have long been known in the world of travelers. First of all, they are appreciated for their stunning stalactite sculptures of the most extraordinary form and unique grottoes! What is only the grotto of the Green Lake, in which the water is of a malachite color.

But people who are terribly afraid of bats are unlikely to like these caves, because there are about seventeen species of them here!

A large number of secrets and mysteries are always associated with caves, 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 indicates 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 was remembered only in 1951, when the Greek Giannis Petrohelios again found and opened it. Indeed, 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 sunlight enters deep into the cave, creating amazing reflections 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 officially recognized as a nature reserve and a World Heritage Site. 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 the US state of 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 gypsum mining here. A rare species of shrimp, crayfish and blind fish have been found in an underground river. 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 electric lighting was installed throughout its entire length. 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 the underwater 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 is possible only when the upper layer of the glacier is washed away, 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 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 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 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 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 (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 built 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%.

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 of speleology. Speleologists make a significant contribution to the study of caves.

Caves are found in almost all adventure novels; this is an indispensable attribute of such works. After all, mysterious darkness reigns here, a booming and deceptive echo, and the light from torches and lanterns is not able to completely disperse the darkness. Robbers used to hide in caves, pirates hid their treasures in them, underground passages passed through them, connecting remote places. Popular beliefs endowed these places with all sorts of evil spirits - from ancient nymphs to Scandinavian trolls.

In fact, such fascinating life rarely boils in caves - it is usually quiet and calm here, and stalactites are the main treasures. Their bizarre forms give a special flavor to underground voids. Let's talk about those caves that stand out among all others for their volume and beauty, which causes serious interest among tourists.

Melissina cave, Greece. The secluded island of Kefalonia is the largest in the Ionian Sea. There is a proper atmosphere here - luxurious landscapes with clean beaches, delicious wine and ancient monasteries. The island is also famous for its caves, Melissina is the most beautiful of them. Only now, the inexorable time and nature made the cave full of holes - after the earthquake, the dome partially collapsed and now sunlight penetrates inside. However, this only embellished the underground decoration. Now the lake in the cave shines through with the rays of the sun, visitors can admire the clear water of an amazing blue hue. But you can’t drink it - it is salty, as it comes from the sea through hidden channels. This place was chosen long before the tourists by the ancient Greek priests, who built here the sanctuary of the god Pan. There are a lot of legends around the cave, but is it possible to do without them in Greece? It is said that the nymph Melissa drowned herself in the underground lake. The reason for her death is either Pan's coldness towards her, or his betrayal, or maybe vice versa, persistent harassment. Once in this place, it would be best to ride a boat on the lake. The nearest town to the cave is Sami, and you can get here by bus from the capital of Kefallonia, the city of Argostoli.

Postojna Yama, Slovenia. The name "postojna" in Slovenian means "inn", and "pit" does not need to be translated. Postojna Pit is the largest cave in all of Slovenia and one of the largest in Europe in general. Here underground galleries are spread over 20 kilometers. Nature has created such beauty in the depths of the limestone plateau of Krase with the help of the Pivka River. However, despite its name, the cave never acted as an inn. But already in the 19th century it was landscaped especially for visiting tourists. Electricity and the world's first cave railway appeared here. The train overcomes 7 kilometers of the way past unusual stalactites and stalagmites, the further journey has to be made on foot. The largest hall in the cave is called the Concert Hall, it is not surprising that even a whole conference of speleologists once took place here. Local reservoirs are also interesting, because even living creatures - proteas - are found here. They have no eyes, they look like a mixture of an albino lizard and a worm. Proteas are distant relatives of salamanders. Having been here, stand on the Russian bridge, built after the First World War by the hands of Russian prisoners of war especially for the Austrians. Not far from here is the city of Postojna, but it will be from Ljubljana - the bus will get here in an hour.

Marble cave, Ukraine. The plateau of the Crimean mountain Chatyr-Dag is literally strewn with wells, mines and caves. The most famous place here is the Marble Cave. Popularity was brought to her by her large size (length - more than two kilometers) and attractive surroundings. Visitors first enter a hall called the "Fairy Tales Gallery". Stalagmites rise here, which resemble fantastic creatures in their appearance. You can see Santa Claus, Mammoth and the Frog Princess. In the next hall - the Palace, there is a miraculous royal couple created by nature, along with a retinue. Also in the cave there is a Rebuilding Hall. It is not entirely clear why it got such a name, because its main attraction is the huge stalagmite "The Tower that fell". Tourists can look into the gallery of the "Tiger Way", in which the bones of a cave bear were once found. You can walk around all the local beauty in an hour, for people there are special paths among the sinter formations. In the cave, you can even find pearls, which are formed from small stalactites that have fallen into puddles of water. Although there is no value from pearls, they look interesting. The closest to the cave is the village of Marble, and you can get here by taxi from Yalta.

New Athos cave, Russia. This formation in Abkhazia is one of the largest in the world. The cave is located inside the Apsara Mountain near the New Athos Monastery, and this is what it owes its name to. There are nine huge halls in the dungeon, the height of the ceiling reaches up to 100 meters. Inside the cave, in addition to lakes, there are also a lot of stalactites in the form of jellyfish, deer and fantastic creatures. This unusual place was discovered in the middle of the 20th century. A failure leads to the cave, nicknamed the Bottomless Pit. Although it was known to the locals for a long time, it was only in 1961 that the speleologist Givi Smyr decided to explore this place. Today, getting into the cave is much easier than then. In summer, an underground railway runs here, tourists even jokingly call it the Abkhaz metro. The train runs between three stations, but then you will have to walk along specially laid out paths. The halls have recently been renamed for political reasons - the Hall of Georgian Speleologists has become the Hall of Speleologists, and the Sukhumi Hall has become the Givi Smyr Hall. Many tourists like to shout loudly in the center of the Apkhyarts hall - after all, there is an excellent and loud echo here. The city of New Athos is closest to the cave, and it would be better to get here from Sochi or Adler by taxi. On the way, in the area of ​​the Psou River, the border with Abkhazia will be crossed.

Kungurskaya cave, Russia. This place is the pride of the Urals, the cave itself is hidden in the depths of the Ice Mountain. It is quite cool here, in some remote grottoes the temperature does not rise above 0 at all, in winter it is all -30°C. Such a unique climate has led to the appearance of quite rare jewelry - crystals from multi-year ice. In order to give them an even more bewitching look, there is laser illumination here, in particular under the arches of the Polar and Diamond Grottoes. For tourists, ice sculptures created by man are also located in the cave. But this place is not famous for ice floes, there are also quite traditional beauties here - stalagmites, stalactites, and there are about 70 lakes here. The largest of them, Big Lake, occupies almost one and a half square kilometers. However, the cold does not prevent living creatures from being present in the cave; once a person also lived here. It is said that there was once a hermit's hut in the Cross Grotto. A well dug here testifies in favor of this theory, and someone's bast shoe was recently found here. In the Coral Grotto there is a bar where you can mark the descent. The city closest to the cave is Kungur, and you can get here by bus from Yekaterinburg, the journey will take 5 hours.

Reed Flute Cave, China. The ancient city of Guilin is located in the center of the Guangxi region. The area here is very picturesque, limestone cliffs of bizarre shape are crowded around. Their companions are traditionally karst caves, of which there are many around Guilin. The most beautiful of them is the Reed Flute Cave. She got her name thanks to the reed that grew near her entrance. It is believed that it is from the stems of this plant that the most melodic flutes are obtained in China. Although the dungeon is not huge - its length is only 500 meters, but nature here has done a lot of work on interior design. And the Chinese themselves decided to complement the impressions with colorful lighting. As a result, the grottoes resemble palace gardens and halls, only the places of trees and columns were occupied by stalagmites and stalactites. In one of the halls, tourists are attracted by an underground lake, and in the other, the giant stalactite Staff of the Dragon King strikes the imagination. It supports the vault of the Crystal Palace hall, which can accommodate almost 1000 people at the same time. Guides assure that lost tourists can get lost in time. They say that one onlooker spent three years here, although it seemed to him that several hours had passed. The closest to the cave is the city of Guilin, the journey from Beijing will take a day and a half.

Mammoth Cave, USA. It's funny, but mammoths have never been found in the cave. It's just that the English word mammoth also means "huge". Back in the 19th century, this cave was discovered in Kentucky under the Flint Ridge. At first, saltpeter was mined in it, but one day the deposits were depleted and a certain entrepreneur bought that place. With the help of servants, he tried to explore the depths of the dungeon, but failed. By the beginning of the 20th century, as many as 5 tiers and more than 200 grottoes, galleries and passages were discovered in the cave. Their total length was as much as 500 kilometers! The end of this underground country has not yet been found. But the Mammoth Cave cannot boast of special beauties or miracles. Its arches consist of red limestone, which practically does not form streaks, so there are fewer figured stalactites than in other caves, much more modest in size. Although the visual range is poor, the places are called loudly - one of the corridors is called Broadway, and the underground river is called Styx. However, there is something that the guides are happy to show the guests - a stone statue that resembles the profile of the mother of President George Washington. So that tourists do not leave their autographs on the walls, they are given a special Hall of Records. Respectable guests can leave not a wall inscription, but a respectable business card. From the largest city of Kentucky, Louisville, you can get here by car in 4-5 hours, and the closest city in the cave is the city of Brownsville.

This report is available in high definition.

People very rarely explore the vast and unexplored, but not National Geographic photographer Stephen Alvarez, who has been exploring and photographing the largest and deepest caves in the world throughout his career.

Cave exploration by Stephen Alvarez.

A cave is a cavity in the ground that communicates with the surface by one or more inlets. (Photo by Steven Alvarez):

The largest caves are complex systems of passages and halls, often with a total length of up to several tens of kilometers. (Photo by Steven Alvarez):

Caves according to their origin can be divided into 5 groups: tectonic, erosional, ice, volcanic and, finally, the largest group - karst. Let's talk about them in more detail. (Photo by Steven Alvarez):

(Photo by Steven Alvarez):

As already mentioned, the vast majority of caves - karst. It is these caves that have the greatest length and depth. (Photo by Steven Alvarez):

Karst caves are formed due to the dissolution of rocks by water, so they are found only where there are soluble rocks: limestone, marble, chalk, gypsum or salt. (Photo by Steven Alvarez):

Tectonic caves can occur in any rocks as a result of the formation of tectonic faults. They are found in the sides of river valleys deeply cut into the plateau, when huge massifs of rock break off from the sides, forming cracks. (Photo by Steven Alvarez):

These fissures sometimes form quite deep vertical caverns up to 100 meters deep. (Photo by Steven Alvarez):

3rd type of caves - erosion. They are formed in the rocks due to mechanical, that is, "cut" 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. (Photo by Steven Alvarez):

Spectacular ice caves are formed in the body of glaciers by melt water. (Photo by Steven Alvarez):

Melt water forms passages, sometimes passable for humans. The length of such caves can be several hundred meters, the depth - up to 100 meters or more. (Photo by Steven Alvarez):

Also, ice caves can be formed in the glacier at the exit point of underground thermal springs located under the glacier. Hot water can create voluminous galleries in the ice. Thermal ice caves are found in Iceland, Greenland and reach quite large sizes. (Photo by Steven Alvarez):

The last type is volcanic caves. They occur during volcanic eruptions. The lava flow, cooling down, is covered with a hard crust, forming a lava tube. After the end of the eruption, lava flows out of the tube from the lower end, leaving a cavity inside the tube. (Photo by Steven Alvarez):

Lava caves can be very large, up to 65.6 km long and 1,100 m deep. (Photo by Steven Alvarez):

In addition to lava tubes, there are vertical volcanic caves - the vents of volcanoes. (Photo by Steven Alvarez):

The living world of the caves is not very rich, however, some animals are found here. Firstly, these are bats that use caves as shelter or for wintering. Moreover, bats often fly into remote and hard-to-reach places in caves, navigating well in narrow labyrinth passages. (Photo by Steven Alvarez):

In addition to bats, insects, spiders, shrimps, salamanders and fish live in some caves. All cave species adapt to complete darkness, and many of them lose their organs of vision. (Photo by Steven Alvarez):

As is known from history, primitive people used caves all over the world as a dwelling. Even more often, animals settled in the caves. (Photo by Steven Alvarez):

Usually water is found in many caves, and karst caves owe their origin to it. Often there are beautiful ones. We have already talked about them in detail. (Photo by Steven Alvarez):

(Photo by Steven Alvarez):

In most caves, the air is breathable, although there are caves where you can only be in gas masks. (Photo by Steven Alvarez):

In addition to caves, which by definition have access to the surface, there are closed underground cavities in the earth's crust. The deepest underground cavity with a length of 2,950 meters was discovered by drilling on the coast of Cuba. (Photo by Steven Alvarez):

In, except for the Earth, caves were found on and. (Photo by Steven Alvarez):

(Photo by Steven Alvarez):

(Photo by Steven Alvarez):

(Photo by Steven Alvarez):