Caves. Their education. Formation and development of caves What natural processes contribute to the formation of caves

Before answering the question “How are caves formed?”, you need to understand what caves are and what they are like.

Caves are empty spaces in rocks underground or under water, as well as above ground. Caves can be through-holes with several openings or with one. They are divided into horizontal, vertical, as well as inclined and single-level or multi-level. The sizes of the caves also vary. It happens that the cave stretches for many kilometers, rises or falls even under the water of an underground river. But the most important difference between one cave and another is the material from which they are made and how they were formed.

So, the most large group caves are Karst. They are divided into marble, salt, crystal, gypsum and limestone caves, as well as others. Such caves are formed due to the dissolution of various rocks in water, and many of them have their own stalactites and stalagmites.

Evolutionists argue that the main factor creating these caves is groundwater, saturated with carbon dioxide, which seeps through cracks along the limestone layers. This process, in their opinion, takes millions of years. But recently another factor has become known that washes out caves much faster - sulfuric acid.

There are also erosive caves by water (along the coastline), which are mechanically washed away by water with large grains of sand, fragments of stones, etc. Tectonic caves are formed on the sides of rivers in places of tectonic faults.

Volcanic caves appear during volcanic eruptions, when lava hardens, creating a kind of pipe through which it further flows, forming voids. Caves in volcanic vents are also volcanic. During the global flood, called Noah's Flood in the Bible, there was worldwide volcanic activity, as a result of which many caves of this type very quickly formed.

Cave - cavity at the top earth's crust, communicating with the surface by one or more inlet openings. Another definition: a cave is a natural underground cavity accessible to human penetration, having parts not illuminated by sunlight and a length (depth) greater than the other two dimensions. The largest caves are complex systems passages and halls, often with a total length of up to several tens of kilometers. Caves are an object of study for speleology. Speleotourists make a significant contribution to the study of caves.

Caves according to their origin can be divided into five groups: tectonic, erosion, glacial, volcanic and, finally, the largest group - karst. The caves in the entrance area, with suitable morphology (horizontal spacious entrance) and location (close to water), were used by ancient people as comfortable dwellings.

Caves by origin

Karst caves

Most of these caves are like this. It is karst caves that have the greatest extent and depth. Karst caves are formed due to the dissolution of rocks by water, so they are found only where soluble rocks occur: limestone, marble, dolomite, chalk, as well as gypsum and salt. Limestone, and especially marble, dissolves very poorly in pure distilled water. Solubility increases several times if dissolved carbon dioxide is present in the water (and it is always present in natural water), but still limestone dissolves poorly compared to, say, gypsum or, especially, salt. But it turns out that this has a positive effect on the formation of extended caves, since gypsum and salt caves not only form quickly, but also quickly collapse.

Tectonic cracks and faults play a huge role in the formation of caves. From the maps of the studied caves one can often see that the passages are confined to tectonic disturbances that can be traced on the surface. Also, for the formation of a cave, a sufficient amount of water precipitation is necessary, a favorable form of relief: precipitation with large area should fall into the cave, the entrance to the cave should be located noticeably above the place where the groundwater is discharged, etc.

A bunch of karst caves are relict systems: the water flow that formed the cave left it due to changes in topography either to deeper levels (due to a decrease in the local basis of erosion - the bottom of neighboring river valleys), or stopped flowing into the cave due to changes in the surface drainage area, after causing the cave to go through various phases of aging. Very often, the caves studied are small fragments of an ancient cave system, exposed by the destruction of the host mountain ranges.

The evolution of karst processes and their chemistry are such that often water, having dissolved the mineral substances of rocks (carbonates, sulfates), after some time deposits them on the vaults and walls of caves in the form of massive crusts up to a meter thick or more (cave marble onyx) or special for each cave of ensembles of mineral aggregates of caves, forming stalactites, stalagmites, helictites, draperies and other specific karst mineral forms - sinter formations.

Recently, more and more caves have been opening in rocks that were traditionally considered non-karst. For example, in the sandstones and quartzites of the tepui table mountains of South America, the Abismo Gai Collet caves, with a depth of −671 m (2006), and Cueva Ojos de Cristal, with a length of 16 km (2009), were discovered. Apparently, these caves are also of karst origin. In hot tropical climates, under certain conditions, quartzite can be dissolved by water.

Another exotic example of the formation of karst caves is the very long and deepest Lechugia Cave in the US mainland (and other caves of the Carlsbad national park). According to the modern hypothesis, it was formed by the dissolution of limestone by rising thermal waters saturated with sulfuric acid.

Tectonic caves

Such caves can appear in any rock as a result of the formation of tectonic faults. As a rule, such caves are found on the sides of river valleys deeply cut into the plateau, when huge masses of rock break off from the sides, forming subsidence cracks (sherlops). Subsidence cracks usually converge like a wedge with depth. Most often they are filled with loose sediments from the surface of the massif, but sometimes they form quite deep vertical caves up to 100 m deep. Sherlops are widespread in Eastern Siberia. They have been studied relatively poorly and are probably quite common.

Erosion caves

Caves formed in insoluble rocks due to mechanical erosion, that is, worked through by water containing grains of solid material. Often such caves are formed on the seashore under the influence of the surf, but they are small. However, the formation of caves is also possible, excavated along primary tectonic cracks by streams going underground. Quite large (hundreds of meters long) erosion caves formed in sandstones and even granites are known. Examples of large erosion caves include T.S.O.D. (Touchy Sword of Damocles) Cave in gabbro (4 km/−51 m, New York), Bat Cave in gneisses (1.7 km, North Carolina), Upper Millerton Lake Cave in granites (California).

Glacier caves

Caves formed in the body of glaciers by melt water. Such caves are found on many glaciers. Melted glacial waters are absorbed by the body of the glacier along large cracks or at the intersection of cracks, forming passages that are sometimes passable for humans. The length of such caves can be several hundred meters, depth - up to 100 m or more. In 1993, a giant glacial well “Isortog” with a depth of 173 m was discovered and explored in Greenland; the influx of water into it in summer was 30 m³ or more.

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

A special type of glacial caves are caves formed in glaciers at the outlet of underground thermal waters located under the glacier. Hot water can create voluminous galleries, but such caves do not lie in the glacier itself, but underneath it, since the ice melts from below. Thermal glacial caves are found in Iceland and Greenland and reach significant sizes.

Volcanic caves

These caves appear during volcanic eruptions. The lava flow, as it cools, becomes covered with a hard crust, forming a lava tube, inside which molten rock still flows. After the eruption has actually ended, the lava flows out of the tube from the lower end, and a cavity remains inside the tube. It is clear that lava caves lie on the very surface, and often the roof collapses. However, as it turned out, lava caves can reach very large sizes, up to 65.6 km in length and 1100 m in depth (Kazumura Cave, Hawaiian Islands).

In addition to lava tubes, there are vertical volcanic caves - volcanic vents.

Caves by type of host rock

The longest cave in the world, Mammoth Cave (USA), is a karst cave built in limestone. It has a total length of passages of more than 600 km. The longest cave in Russia is the Botovskaya cave, over 60 km long, laid in a relatively thin layer of limestone, sandwiched between sandstones, located in the Irkutsk region, river basin. Lena. Slightly inferior to it is Bolshaya Oreshnaya - the world's longest karst cave in conglomerates in the Krasnoyarsk Territory. The longest cave in gypsum is Optimisticheskaya, in Ukraine, with a length of more than 230 km. The formation of such extended caves in gypsum is associated with a special arrangement of rocks: the layers of gypsum containing the cave are covered with limestone on top, due to which the vaults do not collapse. There are known caves in rock salt, in glaciers, in solidified lava, etc.

Caves by size

The deepest caves on the planet are also karst: Krubera-Voronya (up to −2196 m), Snezhnaya (−1753 m) in Abkhazia. In Russia, the deepest cave is Gorlo Barloga (−900 m) in Karachay-Cherkessia. All these records are constantly changing, but only one thing remains constant: karst caves are in the lead.

The deepest caves in the world

The depth of a cave is the difference in height between the entrance (the highest of the entrances, if there are several of them) and the lowest point of the cave. If there are passages in a cave located above the entrance, the concept of amplitude is used - the difference in levels between the lowest and highest points of the cave. According to estimates, maximum depth The occurrence of cave passages under the surface (not to be confused with the depth of the cave!) can be no more than 3000 meters: deeper than that, any cave will be crushed by the weight of the overlying rocks. For karst caves, the maximum depth is determined by the karst base (the lower limit of karst processes, coinciding with the base of the limestone strata), which can be lower than the erosion base due to the presence of siphon channels. The deepest cave is currently the Krubera-Voronya cave with a depth of 2196 m, this is the first and only cave that has crossed the 2 km mark. The first cave to be explored with a depth of more than 1000 meters was the French Berger Abyss, which was considered the deepest in the world from its discovery in 1953 until 1963.

		Depth, m	Location
1	Krubera-Voronya
2
3
4	Lamprechtsofen
5	Mirolda
6	Jean-Bernard
7	Torca del Cerro
8	Pantyukhinskaya
9	Sima de la Corniza
10			Slovenia

The longest caves in the world

		Depth, m	Location
1	Mamontova
2
3	Ox-Bel-Ha
4	Optimistic
5
6
7	Sak-Actun
8			Switzerland
9	Fisher Ridge
10	Gua-Air-Jernich		Malaysia

Contents of the caves

Speleofauna

Although the living world of caves, as a rule, is not very rich (excluding the entrance part where sunlight reaches), nevertheless, some animals live in caves or even only in caves. First of all, this the bats, many of their species use caves as daily shelter or for wintering. Moreover, bats sometimes fly into very remote and hard-to-reach corners, perfectly navigating the narrow labyrinthine passages.

In addition to bats, some caves in warm climates are home to several species of insects, spiders (Neoleptoneta myopica), shrimp (Palaemonias alabamae) and other crustaceans, salamanders and fish (Amblyopsidae). Cave species adapt to complete darkness, and many of them lose their organs of vision and pigmentation. These species are often very rare, many of them endemic.

Archaeological finds

Prehistoric people used caves all over the world as homes. Even more often, animals settled in caves. Many animals died in trap caves starting from vertical 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. This is pollen from fossil plants, bones of long-extinct animals (cave bear, cave hyena, mammoth, woolly rhinoceros), cave drawings ancient people (Kapova caves in the Southern Urals, Divya in the Northern Urals, Tuzuksu in Kuznetsk Alatau, Niah-Caves in Malaysia), tools of their labor (Strashnaya, Okladnikova, Kaminnaya in Altai), human remains of different cultures, including Neanderthals , up to 50-200 thousand years old (Teshik-Tash cave in Uzbekistan, Denisova Cave in Altai, Cro-Magnon in France and many others).

The caves may have served as modern cinemas.

Water in caves

Water is usually found in many caves, and karst caves owe their origin to it. In caves you can find condensation films, drops, streams and rivers, lakes and waterfalls. Siphons in caves significantly complicate passage and require special equipment and special training. Underwater caves are often found. In the entrance areas of caves, water is often present in a frozen state, in the form of ice deposits, often very significant and perennial.

Air in caves

In most caves, the air is breathable due to natural circulation, although there are caves in which you can only be in gas masks. For example, guano deposits can poison the air. However, in the overwhelming majority natural caves air exchange with the surface is quite intense. The reasons for air movement are most often the temperature difference in the cave and on the surface, so the direction and intensity of circulation depend on the time of year and weather conditions. In large cavities, the air movement is so intense that it turns into wind. For this reason, air draft is one of the important signs when searching for new caves.

Cave deposits

There are mechanical (clay, sand, pebbles, blocks) and chemogenic deposits (stalactites, stalagmites, etc.). In cave systems with an active watercourse, as a rule, mechanical deposits are presented in the form of blocky rubble, often of very large volumes, formed as a result of the collapse of the arch of passages, which is formed by dissolution of the water flow. Rubbles are difficult to pass and dangerous, since the balance of a blocky rubble is often unstable. Clay deposits are widely represented in galleries that were abandoned by an active watercourse that carried out mechanically insoluble rock particles. The soluble component of the cave's limestone is calcium carbonate, which often makes up only about 50% of the rock. The remaining minerals, as a rule, are insoluble, and if the water dissolving the rock is presented in the form of a drop, an infiltrate, with low water flow, unable to provide mechanical transport of particles, the accumulation of clay deposits begins. Very often ancient passages are completely blocked by clay.

Chemogenic deposits (sinter formations) also usually decorate the ancient galleries of the cave, where water, slowly filtering through cracks in the limestone, is saturated with calcium carbonate, and when it enters the cave cavities, due to a slight change in the partial pressure of water vapor when a drop comes off, or when When it falls on the floor, or when turbulence occurs during draining, calcium carbonate crystallizes from the saturated solution in the form of calcite.

Excursion caves

Some caves are equipped for visiting by excursion groups (so-called showcaves). To do this, in the part of the cave that is most spacious and rich in sinter formations, pedestrian paths, ladders, bridges are laid, and 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 Mramornaya in Crimea, Kungurskaya in the Urals, and Novoafonskaya in Abkhazia.

Caves in the Solar System

In addition to the Earth, caves have been discovered on the Moon and Mars. Apparently, these are volcanic caves, ancient traces of volcanic activity.

Artificial caves

Caves - dungeons of the industrial world

Under any large city there is a system of technical dungeons: basements of above-ground buildings, metro, life support systems (plumbing, heating, sewerage, electrical and telephone cables, fiber optic network), bomb shelters, bunkers in case of war, etc.

The cave is like the dwelling of holy ascetics

Many holy ascetics built their homes in the caves. Later, monasteries and Lavras were founded on these places:

Kiev-Pechersk Lavra
Pskov-Pechersky Monastery
Holy Dormition Cave Monastery (Crimea)
Kholkovsky Monastery
Chelter-Koba
Basarbovsky Monastery
Cave churches in Ivanovo

Holy ascetics who lived in caves:

“And Lot went out from Zoar and began to live in the mountain, and his two daughters with him, for he was afraid to live in Zoar. And he lived in a cave, and his two daughters with him" (Genesis 19.30)
“And he the Prophet Elijah entered a cave there and spent the night in it” (3rd Book of Kings 19.9)
Hilarion of Kyiv
Anthony Pechersky
Varlaam Pechersky

Caves-houses

Many peoples built their homes in caves, as they were easy to keep clean and maintain a constant temperature throughout the year.

Cappadocia
Anasazi
Guadiz
Sassy Di Matera

Medicinal caves

Many medical institutions have rooms called “salt caves”. The walls are lined with potassium salt bricks, and patients spend some time in them, listening to music and receiving a healing effect.

Entertaining caves

There are well-known caves of horror as part of amusement parks, cafes and bars decorated to look like caves.

Caves in mythology, mysticism and religion.

V. G. Ivanchenko wrote about the symbolic and mystical meaning of caves in his article “The Sign of the Cave”, published in the magazine “Orientation”.

Caves in art, literature and film

Caves appear in many fantasy works (both fantasy and science fiction). Caves (more precisely, bunkers) in science fiction mainly serve as shelters after a global catastrophe that has made life on the surface impossible. And also caves in fantasy are inhabited by: gnomes, kobolds, goblins, dragons, and in Russian folk tales the “Mistress of the Copper Mountain”, the Serpent Gorynych, lives there. In northern mythology, Sirtya live in caves. One of the most famous literary heroes who ended up in the caves was: Tom Sawyer, along with Becky Thatcher, Bilbo Baggins.

Underground cavities

In addition to caves that have access to the surface and are accessible to direct study by humans, there are closed underground cavities in the earth’s crust. The deepest underground cavity (2952 meters) was discovered by drilling on the coast of Cuba. In the Rhodope Mountains, an underground cavity was discovered at a depth of 2400 meters during drilling. On Black Sea coast In Gagra, drilling discovered underground voids at a depth of up to 2300 meters.

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Moscow State Institute of Steel and Alloys

Vyksa Branch

(University of Technology)

Abstract on the subject

crystal physics

On the topic: “Formation of caves and karsts”

Student: Pichugin A.A..

Groups:MO-07 (MFM)

Teacher: Lopatin D.V.

Moscow 2008

I. General information about caves and karsts

II. Hypothesis about the origin of karst areas

III. Conditions for the formation of caves

IV. Types of caves:

1. Karst caves

2. Tectonic caves

3. Erosion caves

4. Glacier caves

5. Lava Cave

V. Caves in the Baikal region

VI. Cave Kyzylyarovskaya named after. G.A. Maksimovich.

General information about caves and karsts

Karst(from German Karst, after the name of the limestone alpine plateau Kras in Slovenia) - a set of processes and phenomena associated with the activity of water and expressed in the dissolution of rocks and the formation of voids in them, as well as peculiar relief forms that arise in areas composed of relatively rocks that are easily soluble in water (gypsum, limestone, marble, dolomite and rock salt).

Negative relief forms are most characteristic of karst. Based on their origin, they are divided into forms formed by dissolution (surface and underground), erosive and mixed. Based on morphology, the following formations are distinguished: karsts, wells, mines, failures, funnels, blind karst ravines, valleys, fields, karst caves, underground karst channels. For the development of the karst process, the following conditions are necessary: a) the presence of a flat or slightly sloping surface so that water can stagnate and seep in through cracks; b) the thickness of karst rocks must be significant; c) The groundwater level should be low so that there is sufficient space for vertical movement of groundwater.

Based on the depth of the groundwater level, karst is distinguished between deep and shallow. There is also a distinction between “bare” or Mediterranean karst, in which karst relief forms are devoid of soil and plant cover (for example, the Crimean Mountains), and “covered” or Central European karst, on the surface of which the weathering crust is preserved and soil and plant cover are developed.

Karst is characterized by a complex of surface (craters, quarries, trenches, basins, caverns, etc.) and underground (karst caves, galleries, cavities, passages) relief forms. Transitional between surface and underground forms are shallow (up to 20 m) karst wells, natural tunnels, shafts or failures. Karst sinkholes or other elements of surface karst through which surface water flows into the karst system are called ponors.

KARST, limestone plateau - a complex of irregularities, convex rock outcrops, depressions, caves, disappeared streams and underground drains. Occurs in water-soluble and weathered rocks. The process is typical for limestone, as well as in places where rocks are washed away. Many rivers are underground, and there are also many caves and large caverns. The largest caves can collapse and form a gorge or gorge. Gradually all the limestone can be washed away. The phenomenon is named after the Karst plateau in the former Yugoslavia. Characteristic karst systems are widely represented in Crimean mountains and in the Urals.

Karst can be observed in the Western Alps, in the Appalachians (USA) and in southern China because layers of limestone rocks, first consisting of a layer of calcite (calcium carbonate), up to 200 m thick, were partially eroded by water. Carbon dioxide from the atmosphere dissolved in the rain and contributed to the formation of weak carbonic acid, which in turn contributed to the erosion of rocks, especially along cleavage lines and layers, increasing them to the formation of karst caves, valleys that arose as a result of the collapse of cave walls, which with further development process can turn into gorges, and finally, the remains of limestone that have not been eroded, characteristic of a karst landscape, remain.

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

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

HYPOTHESIS ABOUT THE ORIGIN OF KARST AREAS

Namely, there is a hypothesis that:

In ancient times, 300-400 million years ago, in sea water there was a process of growth and death of living organisms that intensively used calcium to build their shells. The water was a saturated solution of calcium carbonate. The dead shells sank to the bottom and accumulated along with sediments that precipitated out of solution as a result of climate change;

Over millions of years, limestone mass accumulated in layers at the bottom;

Under pressure, the limestone sediment changed its structure, turning into stone lying in horizontal layers;

At the moment of movement of the earth's crust, the sea receded, and the former bottom became dry land;

Two scenarios for the development of events were possible: 1) the layers remained almost horizontal and undisturbed (as near Moscow); 2) the bottom bulged out to form mountains, while the integrity of the limestone layers was violated, and numerous transverse cracks and faults formed in them. This is how the future karst region was formed.

This hypothesis is confirmed by the finds of remains of ancient shells and other former living organisms in the limestone layer. Be that as it may, it is obvious that caves and the rocks where they are formed are closely related to ancient life on the ground.

CONDITIONS FOR CAVE FORMATION

There are three main conditions for the formation of karst caves:

1. Presence of karst rocks.

2. The presence of mountain building processes, movements of the earth's crust in the zone of distribution of karst rocks, as a result - the presence of cracks in the thickness of the massif.

3. Presence of aggressive circulating water.

Without any of these conditions, cave formation will not occur. However, these necessary conditions may be superimposed by local features of climate, relief structure, and the presence of other rocks. All this leads to the appearance of caves of various types. Even in one cave there are various “composite” elements that are formed in different ways. The main morphological elements of karst caves and their origin.

Morphological elements of karst caves:

Vertical abysses, shafts and wells,

Horizontally inclined caves and meanders,

Labyrinths.

These elements arise depending on the type of disturbances in the thickness of the karst massif.

Types of violations:

Faults and faults, cracks:

Bedding,

At the border of karst and non-karst rock,

Tectonic (usually transverse),

So-called side thrust cracks.

Scheme of the formation of vertical elements of caves (wells, shafts, abysses): Leaching.

Wells are formed at the intersection of tectonic cracks - at the mechanically weakest point of the massif. Water from atmospheric precipitation is absorbed there. And slowly dissolves the limestone; Over millions of years, water widens the cracks, turning them into wells. This is a zone of vertical circulation of groundwater

Nival wells (from the surface of the massif):

In winter, the cracks are clogged with snow, then it slowly melts, this is aggressive water, it intensively erodes and expands the cracks, forming wells from the surface of the earth.

Formation of horizontally inclined passages:

Water, having penetrated through the layer (layer) of karst rock, reaches the bedding crack and begins to spread along it along the plane of “dip” of the layers. The leaching process occurs and a subhorizontal passage is formed. Then the water will reach the next intersection of tectonic cracks and again a vertical well or ledge will form. Finally, the water will reach the boundary of karstic and non-karstic rocks and then spread only along this boundary. Usually an underground river already flows here and there are siphons. This is a zone of horizontal circulation of groundwater.

Formation of halls.

The halls are found in fault zones - large mechanical disturbances in the massif. The halls are the result of alternating processes of mountain building, leaching, and mountain building again (earthquakes, landslides).

Sometimes additional mechanisms are activated:

Mechanical removal of rock fragments by water flows,

The effect of pressure thermal waters (New Athos Cave).

Karst caves– these are underground cavities formed and thicker than the earth’s crust, in areas where easily soluble carbonate and halogen rocks are distributed, subject to leaching and mechanical stress, these rocks are gradually destroyed, which leads to the formation of various karst forms. Among them, the greatest interest is caused by underground karst forms - caves, mines and wells, sometimes characterized by a very complex structure. One of the main conditions formation of karst caves is the presence of karst rocks characterized by significant lithological diversity. Among them are carbonate rocks (limestones, dolomites, chalk, marbles), sulfate rocks (gypsum, anhydrites) and halide rocks (rock salts, potassium salts). Karst rocks are very widespread. In many places they are covered by a thin cover of sandy-clay 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 influenced by the thickness of the rocks, their chemical composition and features of occurrence.

Water is the builder of karst caves

As already mentioned, the builder of karst caves is water. However, in order for water to dissolve rocks, they must be permeable, that is, fractured. Rock fracturing is one of the main conditions for the development of karst. If a carbonate or sulfate massif is monolithic and consists of solid rock varieties without fracturing, then it is not affected by karst processes. However, this phenomenon is rare, since limestones, dolomites and gypsum are fractured by nature. The cracks that cut through limestone massifs have different origins. Cracks stand out 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 onto the surface of a karst massif, atmospheric precipitation penetrates into the depths of 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 uniqueness of the hydrogeological regime largely determine the degree of trickiness of karsting strata, the intensity and conditions for the development of underground cavities.

Rain and melted snow water

The main role in the formation of many karst cavities is played by infiltration and inflation of rain and melted snow water. Such caves - corrosion-erosion origin, since the destruction of rock occurs both due to its chemical leaching, and by mechanical erosion. However, one should not think that these processes occur simultaneously and continuously. At different stages of cave development and in different areas, 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, their origin due to the activity of melted snow waters in the zone of contact of the snow mass with karst rock. These include, for example, the relatively shallow (up to 70 m) vertical cavities of the Crimea and the Caucasus. Many caves arose as a result of the collapse of the roof over underground corrosion-erosive voids. Some natural cavities were formed by leaching of rocks by artesian, mineral and thermal waters ascending through cracks. Thus, karst caves can be of corrosion, corrosion-erosion, erosion, nival-corrosion, corrosion-gravity (sinkhole), hydrothermal and heterogeneous origin.

Condensation water

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. Subjected to leaching and mechanical stress, these rocks are gradually destroyed, which leads to the formation of various karst forms. Among them, the greatest interest is caused by 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, characterized by significant lithological diversity. Among them are carbonate rocks (limestones, dolomites, chalk, marbles), sulfate rocks (gypsum, anhydrites) and halide rocks (rock salts, potassium salts). Karst rocks are very widespread. In many places they are covered by a thin cover of sandy-clay 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 influenced 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, that is, fractured. Rock fracturing is one of the main conditions for the development of karst. If a carbonate or sulfate massif is monolithic and consists of solid rock varieties without fracturing, then it is not affected by karst processes. However, this phenomenon is rare, since limestones, dolomites and gypsum are fractured by nature. The cracks that cut through limestone massifs have different origins. There are cracks of 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 onto the surface of a karst massif, atmospheric precipitation penetrates into the depths of 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 uniqueness of the hydrogeological regime largely determine the degree of cavernousness of karsting 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 of rain and melted snow water. Such caves are of corrosion-erosion origin, since the destruction of rock occurs both due to its chemical leaching and mechanical erosion. However, one should not think that these processes occur simultaneously and continuously. At different stages of cave development and in different areas, 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, their origin due to the activity of melted snow waters in the zone of contact of the snow mass with karst rock. These include, for example, the relatively shallow (up to 70 m) vertical cavities of the Crimea and the Caucasus. Many caves arose as a result of the collapse of the roof over underground corrosion-erosive voids. Some natural cavities were formed by leaching of rocks by artesian, mineral and thermal waters ascending through cracks. Thus, karst caves can be of corrosion, corrosion-erosion, erosion, nival-corrosion, corrosion-gravity (sinkhole), hydrothermal and heterogeneous origin.

In addition to infiltration, infusion and pressure waters, condensation waters also play a certain role in the formation of caves, which, collecting on the walls and ceilings 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 caves. Especially favorable conditions for moisture condensation are characterized by small cavities located at a significant 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 in the studied karst caves 3201.6 m3 of water condenses 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 hardness exceeds 6 mEq (300 mg/l). Thus, due to the infiltration waters of the cave Mountain Crimea, as simple calculations show, increase compared to the total volume by approximately 5.3%. 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 from 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 effect on rock as an agent of denudation is limited mainly to the warm period.

How does the process of leaching of karst rocks proceed? Let us consider this issue in general terms using the example of carbonate formations. 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 influence of carbon dioxide, calcium carbonate turns into bicarbonate, which is much more easily soluble in water than carbonate

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

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

The carbon dioxide released as a result of this reaction turns out to be an additional source of the formation of bicarbonates.

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 for underground voids to form. In this case, karst rocks dissolve and collapse only along cracks; outside the cracks they remain very strong and hard.

Atmospheric waters penetrating into karst massifs through cracks and tectonic disturbances are initially characterized by predominantly vertical movement. Having reached the aquitard or local erosion base, they acquire horizontal movement and usually flow along the dip of the rock layers. Some of the water seeps into deep horizons and forms regional runoff. In this regard, several hydrodynamic zones are distinguished in the karst massif, namely the zone of surface, vertical, seasonal, horizontal, siphonic and deep circulation of karst waters (Fig. 1). Each of these hydrodynamic zones is characterized by a certain set of karst forms. Thus, mainly 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 inclined cracks as a result of periodic leaching of rocks by melted snow and rainwater. In the zone of horizontal circulation, where there is a free flow of free-flowing water to river valleys or the periphery of the karsting massif, horizontal caves are formed. Inclined and horizontal cavities are observed in the zone of siphon circulation, characterized by pressure waters that move in sub-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, animal world, and economic activity person. Unfortunately, the role of these factors in cave formation has not been sufficiently studied at present. It is 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 layers 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) embryonic channels formed in the zone of complete saturation of slowly moving phreatic waters under pressure; b) mature galleries, when mechanical erosion (corrosion) begins to dominate under the conditions of the spread of free-flow vadose flows; c) dry galleries that arose as a result of water moving deeper into the massif due to local uplift of the territory; d) sinter-accumulative, characterized by the filling of galleries with sinter-drip and other cave deposits; e) destruction of underground galleries (peneplanation).

Based on 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 through the galleries towards drainage systems) stages of cave development (Bretz, 1942).

The issues of the evolution of underground cavities were most fully developed by Soviet researchers G. A. Maksimovich (1963, 1969) and L. I. Maruashvili (1969), who identified several stages of the formation of horizontal karst caves. The first stage is fissure, then crevice. As the width of cracks and crevices increases, more and more water penetrates them. This activates karst processes especially in areas of pure rock differences. The cave enters the channel stage. When the channels expand, underground flows acquire turbulent movement, which favors an even greater intensification of the processes of corrosion and erosion. This is the stage of the underground river, or Vauclusian. It is characterized by a significant filling of the underground channel with water flow and its release in the form of an influx source onto 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 deep into the carbonate and halogen strata, where it develops new cavities at a lower level, forming a lower floor of the cave (Fig. 2). Gradually, the underground channels are expanding. water flow partially and then completely goes into the lower horizons of the massif, and the cave becomes dry. Only infiltration water penetrates through cracks in the roof. This is the corridor-grotto sinter-talus (water-gallery, according to L.I. Maruashvili) stage of cave development. It is characterized by a wide distribution of chemical and mechanical accumulation (in gypsum caves there is no stage of sinter accumulation). The ceiling and walls of the cave are covered with various calcite deposits. Stone and earthen screes are formed, the latter being located mainly under organ pipes. Sediments from rivers and lakes also accumulate. With the departure of the watercourse, further expansion of the underground cavity slows down sharply, although 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 above the underground cavities, the opening of some parts of the cave is possible. 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. When a cave is completely destroyed, a karst valley is formed.

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

The duration of individual stages of the cave-forming cycle, distinguished by their hydrodynamic and morphological features, the specificity of physico-chemical processes and the uniqueness 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, crevice, channel and vault), their duration is much shorter. Caves “can reach a mature water-gallery state within several thousand years from the initial moment of their development.” In this regard, the experimental studies of E. M. Abashidze (1967) on the dissolution of the walls of cracks in glauconite limestones of the Shaori reservoir (Caucasus) are interesting. Experiments have shown that over 25 years of continuous filtration, depending on the flow rate, hairline cracks measuring 0.1-0.25 mm can increase to 5-23 mm.

Thus, karst caves are characterized by a complex evolution, the features of which depend on a combination of a variety of factors that often determine significant deviations from the considered scheme. The development of caves, for one reason or another, can stop or begin again at any morphological and hydrological stage. Complex cave systems usually consist of areas at different stages of development. Thus, in the Ishcheevskaya cave in the Southern Urals, areas from the channel stage to the karst valley are currently found.

A feature of many caves is their multi-tiered nature, with the upper tiers always being 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-story caves ranges from several meters to several tens. The collapse of the vaults separating the cave floors leads to the formation of giant grottoes, sometimes reaching a height of 50-60 m (Krasnaya and Anakopiyskaya caves).

G. A. Maksimovich associates 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-story caves in conditions of high thickness of karst rocks to upward movements, which he views not as a disturbing factor, but as a general background for the evolution of karst. According to L.I. Maruashvili, the multi-tiered nature of caves can be determined not only by the tectonic uplift of the karst massif, but also by a general decrease in ocean level (eustasy), which causes intensive deepening of river valleys and a rapid decrease in the level of horizontal circulation of karst waters.

Tiering is best expressed in caves of lowland and foothill areas, characterized by relatively slow tectonic uplifts. During the formation of caves, a displacement of the axis of cave galleries from the original vertical plane is sometimes observed. The Tsutskvatskaya cave is interesting in this regard. Each younger (of the four lower) levels 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 further to the east than during the formation of the higher levels 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 what signs can be used to judge the beginning of the formation of the cave? According to L.I. Maruashvili, the period of its transition to the sinter-talus (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 caves, including paleozoological, archaeological, radiocarbon dating and geomorphological. In the latter case, the hypsometric level of caves is compared with the levels of surface forms. Unfortunately, many of these methods provide only an upper limit on the age of a cave. Direct and indirect data prove the very long existence of karst caves, sometimes lasting 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 persist for a very long time. Interesting 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 characteristics 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, identifies the following stages of the formation of Podolsk caves: Upper Sarmatian (the beginning of intense deep erosion), Early Pliocene (characterized by the intensification of vertical processes ), Late Pliocene (processes of horizontal circulation of groundwater prevail over vertical ones), Early Pleistocene (processes of cave formation reach maximum intensity), Middle Pleistocene (processes of underground karst formation begin to fade), Late Pleistocene (accumulation of mineral and chemogenic formations), Holocene (accumulation of block deposits). Thus, the age of the world's largest gypsum caves Optimisticheskaya, Ozernaya and Kryvchenskaya in Podolia apparently exceeds 10 million years. The age of limestone caves can be even more significant. Thus, some ancient karst caves of the Alai Range ( middle Asia), having hydrothermal origin, according to Z. S. Sultanov, were formed in the Upper Paleozoic time, i.e. more than 200 million years ago.

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

To quantify karst cavities, G. A. Maksimovich (1963) offers two indicators: density and density of karst caves. Density refers to the number of caves per area of 1000 km 2, and density refers to the total length of all cavities within the same conventional area.

J. Corbel proposed to characterize the size of karst caves by the voidness indicator, calculated using the formula

Where V - the volume of soluble rock in which the cave is developed is 0.1 km 3; L- the distance (on the plan) between the extreme points along the main axis of the cavity system is 0.1 km; J- the distance between the two most distant points perpendicular to the main axis is 0.1 km; N - the difference in elevation 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 involves calculating 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 using the Simpson formula

Where v - volume of the geometric figure, m 3; h - height of the figure, m; s 1, s 2, s 3 - areas of the lower, middle and upper sections of the figure, m 2. Testing of this method by Crimean speleologists showed that errors in calculating the volume of cavities using Simpson's formula do not exceed 5-6%.