How are caves formed? The most famous caves

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 features of occurrence.

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

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

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

In addition to infiltration, inflation and pressure waters, condensation waters also play a certain role in the formation of caves, which, gathering on the walls and ceiling of caves, corrode them, creating bizarre patterns. Unlike underground streams, condensation waters affect the entire surface of the cavity, and therefore have greatest influence 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 base of erosion, they acquire a horizontal movement and usually flow along the fall of rock layers. Part of the water seeps into deep horizons and forms a regional runoff. In this regard, several hydrodynamic zones are distinguished in the karst massif, namely, the zone of surface, vertical, seasonal, horizontal, siphon and deep circulation of karst waters (Fig. 1). Each of these hydrodynamic zones is characterized by a certain set of karst forms. Thus, vertical underground cavities - karst wells and mines - are confined to the zone of vertical water circulation or the aeration zone. They develop along vertical or gently sloping cracks as a result of periodic leaching of rocks by melted snow and rain waters. Horizontal caves are formed in the zone of horizontal circulation, where there is a free flow of non-pressure waters to river valleys or the periphery of a karst massif. Inclined and horizontal cavities are noted in the zone of siphon circulation, characterized by pressure waters that move in underflow channels, often below the local erosion base.

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

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

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

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

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

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

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

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

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

A feature of many caves is their multi-tiered, and 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 early stages in its development, the cave is not yet a cave in the usual sense: it is poorly developed, completely filled with water and completely impassable.

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

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

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

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

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

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

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

Cave- a natural underground cavity in the upper thickness of the earth's crust, communicating with the earth's surface by one or more outlets passable for humans.

Caves may be filled with air or other gas, water, or partially solid deposits. By origin, the caves are divided into primary and secondary. Primary caves are syngenetic to tectonic rocks: gas bubbles and tunnels in lavas, cavities in reefs and calcareous tuffs, hydration caves in gypsum anhydrites; secondary caves - the result of geological processes that manifest themselves in the formed rock or glacier: weathering, leaching, blowing, suffusion, abrasion on the coasts of the seas, karst, hydrothermal, glacial caves in glaciers. The most common are karst caves. Artificial caves are called abandoned mine workings, similar to natural ones, as well as rooms carved into the rocks, mainly medieval cave cities(for example, Vardzia in Georgia and Chufut-Kale in Crimea).

The largest caves complex systems passages and halls, often with a total length of up to several tens of kilometers.

Caves go through a number of stages in their development. At the present stage, they can be located above the level of karst waters (dry caves) or in the zone of their formation (caves with lakes, rivers, source caves). Powerful streams flow in some caves, for example, the flow of an underground river in the Shkopianskaya cave (Yugoslavia) reaches 200 m / s, and the water level fluctuations are 114 m. On the coasts of the seas and islands, caves are known that are submerged below sea level and filled with water, for example Blue Hols on Andros Island (Bahamas) at a depth of up to 60 m.

Caves are a special habitat for organisms. species composition The fauna and flora of the cave is poor, the biomass index is low. The fauna is represented by invertebrates (about 460 species), some amphibians (Proteus), and cave fish. The permanent inhabitants of the cave - troglobionts - are characterized by depigmentation, blindness, sometimes gigantism, slow metabolism. Flocks of bats (bats) live seasonally in some caves, for example, about 40 thousand individuals settle in the Bakharden cave (Kopetdag, Turkmenistan) in summer. Due to the stability of the conditions of existence, representatives of ancient faunas survived. Geological processes of destruction (corrosion, erosion, weathering, collapse) of rocks, sedimentation and mineral formation simultaneously proceed in the caves. The deposits of the cave are represented by underground eluvium, deluvium, landslide-scree (gravitational) sediments, deposits of rivers and lakes, secondary water chemogenic formations, ice, organic and anthropogenic (cultural layers). Most of the caves are dominated by low-temperature conditions of mineral formation; ore-forming hydrothermal solutions penetrate into some caves. The most common are calcite, aragonite, and gypsum. Secondary chemogenic forms are represented by calcite, aragonite or gypsum mineral aggregates - stalactites, stalagmites, draperies, columns, crystallictites and corallites, etc.

Gypsum stalactites, stalagmites, crusts are described in the Gaurdak cave (Chardzhou region, Turkmenistan), located in limestones, gypsum anhydrites, and sulfur ores of the Jura, partially below the base of the sulfur deposit; in the zone of oxidation of sulfuric rocks - jarosite, halloysite, sulfur in the form of "mountain milk". Mercury sulfide mineralization was revealed in some galleries. Marble onyx is found in caves: for example, in twelve caves of the Altai-Sayan folded region, onyx reserves in talus are estimated at 300 tons. Ocher in limestone and conglomerate caves in places forms accumulations of tens of thousands of tons.

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.

Types of caves

Karst caves

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

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

The chemistry of karst processes is such that often water, having dissolved the rock, after a while deposits it back, forming the so-called. "sintered" formations: stalactites, stalagmites, stalagnates, draperies, as well as exotic helictites and so on.

Tectonic caves

Such caves can arise in any rocks as a result of the formation of tectonic faults. As a rule, such caves are found in the sides of river valleys deeply cut into the plateau, when huge rock masses break off from the sides, forming sagging cracks (sherlops). Seizure cracks usually wedge together with depth. Most often they are covered with loose sediments 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.

erosion caves

Caves formed in insoluble rocks due to mechanical erosion, that is, worked out by water containing grains of solid material. Often such caves are formed on the seashore under the action of the surf. 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, laid in sandstones and even granites.

Glacial caves

View from the bottom of a 55-meter active entrance well on the Aldegonda glacier in 2002 (Svalbard). You can see the round section of the well. The silhouette of a man is visible at the top for scale.

Characteristic lengths are a few hundred meters, depths are up to 100 m or more. In 1993, in Greenland, a giant 173 m deep Izortog glacial well was discovered and explored; the inflow of water into it in summer was 30 m 3 /cm or more. waters on the edge of glaciers. Meltwater in such caves can flow over both the glacier bed and glacial ice.

Glacier cave on the edge of the Fallbreeen glacier, Svalbard

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

Volcanic caves

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

What is the meaning of the words "karst cave"? How did these beautiful natural objects? You can find answers to these questions in this article. In addition, here we list the longest in the world (you can also see photos of these underground voids). Curiously, most of them are located in the United States.

A cave is ... The meaning of the words "karst cave"

These underground cavities from the most ancient times served as a dwelling for animals, as well as primitive people. They hid them from the cold and wild predators. Interestingly, caves have been found not only on Earth, but also on the Moon and Mars. Let us first find out the meaning of the words "karst cave".

This phrase consists of two parts: "cave" and "karst".

• A cave is any underground cavity of natural origin.
• Karst is both a process and a result of the destruction (dissolution) of certain rocks by aggressive (in terms of chemical composition) groundwater.

The term "karst" itself comes either from German word karst, or from the name of a plateau in Slovenia (Kras), where these natural phenomena appear especially strong.

What is a karst cave?

This type of caves is the most common among all other underground cavities. What is a karst cave and how is it formed?

There are two main definitions. According to the first, it is a natural cavity (emptiness) in the upper part of the earth's crust, which is connected to its surface by one or more entrances. According to the second definition, a karst cave is an underground cavity of natural origin, which is not illuminated by the Sun, but is accessible to penetration from the outside.

The study of caves is carried out by a special science - speleology, the material for which is often mined by the so-called speleologists.

How are karst caves formed?

Caves of this type are formed due to, namely, due to the dissolution of rocks by water. It should be noted that karst caves are present only in those areas of the Earth where unstable rocks occur, which are easily dissolved by water. Among these are gypsum, salt, chalk (kaolin), dolomite, marble and limestone.

Worse than all the others, limestone and marble are destroyed. Caves in these rocks are formed for a very long time. On the other hand, they are better preserved than others. For example, gypsum caves very often collapse and collapse.

An important role in the formation of underground voids is played not only by the chemical composition of water (it should contain an increased concentration of carbon dioxide), but also by the presence of cracks and extended faults in the earth's interior. They tend to be the centerlines along which caves form.

Most of the studied caves are relic type systems. This means that the water has already left these underground cavities. Nevertheless, it is she who acts as the sculptor who forms the internal "micro-relief" of the cave. saturated with sulfates and carbonates, deposits them on the walls, floors and vaults of underground cavities. This is how what we call is formed. Very often, these growths take on strange and bizarre forms that look even more unusual in the darkness.

Main types of caves

According to the mechanism of genesis (formation), in addition to karst, there are also tectonic, volcanic, erosional, and glacial caves.

Underground cavities are also classified by size (by total length and depth), as well as by the type of rocks in which they are formed. So, there are caves:

• limestone;
• plaster;
• chalky;
• salt;
• caves in conglomerates and so on.

TOP 5 longest caves on the planet

Four of the five longest caves in the world are located in the United States, and one more is in Ukraine.

(about 630 km) - the longest cave system on Earth. It was formed in limestone 10 million years ago. Every year the length of the cave increases, as speleologists explore its new corridors.

Jewel Cave (257 km) - located near the city of Custer. Its unique feature is calcite crystals, which cover the walls of all underground corridors in a thick layer.

Cave Optimisticheskaya (231 km) - a multi-level network of labyrinths in Ukraine (in the Ternopil region), the largest underground system in Eurasia. Formed in gypsum.

Wind Cave (217 km) is another American wonder of nature, which is known for its honeycomb-like patterns on the vaults.

Cave Lechugia (207 km) - a gypsum cave in the USA (New Mexico), calling card which are unusual "chandelier" formations, reaching up to 5-6 meters in diameter.

Conclusion

Well, now you know the meaning of the words "karst cave". This is an underground cavity of natural origin, which has one or more exits to the surface. All caves are classified by speleologists according to size, mechanism of genesis, as well as according to the rocks in which they are laid (formed).

“A cave is a cavity in the upper part of the earth’s crust that communicates with the surface by one or more inlets,” Wikipedia gives this definition. In fact, everything is true, but these words do not even remotely convey all the bewitching beauty, all the originality of these natural objects, which gave shelter to the first people hundreds of thousands of years ago, and now amaze their descendants with their power, diversity and, let's not be afraid of this word, splendor.

Brief information about the caves:

Let's start with what they can have just giant size. For example, the total length of the Mammoth Cave (Kentucky, USA) is more than 678 kilometers, it is considered the longest in the world.

The deepest is located in Abkhazia - Krubera-Voronya (- 2196). But the largest cave in terms of volume is located in Vietnam - Hang Son Dung. The dimensions of its main hall are amazing - 5000 meters long, 150 wide and 200 high. This volume is enough to accommodate 40 skyscrapers! By the way, it was opened only in 2009.

So on our seemingly well-trodden planet, there are still places for amazing geographical discoveries.

Types of caves:

1. Karst caves- the most numerous and, perhaps, the most beautiful group. It is the caves of this group that amaze us with their depth, length and volume. Formed by dissolving in water various breeds- limestone, gypsum, chalk, salt and even marble. And in tropical climate even quartzite can dissolve in water. An example of this is the relatively recently discovered caves of Abismo Gai Collet (length - 671 m) and Cueva Ojos de Cristal (length 16 km).
   In karst caves, due to the physical and chemical processes taking place there, stalactites, stalagmites, helictites are formed, as well as such an amazing sinter formation as cave onyx, which can be up to a meter thick.
2. Tectonic caves- formed due to tectonic faults in earth's crust. Most often found on the sides of river valleys cut into the plateau.
3. erosion caves- according to the mechanism of formation, they are somewhat similar to the formation of karst caves. Only if the latter appear due to the dissolution of rocks, then these are due to the erosion of rocks under the influence of water containing solid particles. As a rule, such caves are small, but occasionally quite large ones are found. For example, Bat Cave (length 1.7 km) in Colorado (USA).
4. Glacial caves formed under the influence of melt water in glaciers. They are usually up to several hundred meters long. A special type of glacial caves are thermal caves formed under the influence of underground thermal waters. Found in Greenland and Iceland.
5. Volcanic caves- Formed during volcanic eruptions. The youngest of all types of caves. The mechanism of their formation is as follows. During the eruption, the lava flow, gradually cooling down, is covered with a hard crust from above. A lava tube is formed, inside of which the still liquid lava moves. In the end, the part of the lava that did not have time to solidify flows out of the lower end of such a tube, and a cavity forms inside. Volcanic vents should also be considered caves of this type.

Curious facts about caves

These interesting and in many ways mysterious objects always worried about people. We can say that humanity came out of the caves. Over the millennia, a huge number of facts of "cooperation" of people with them have been accumulated. Let's take a look at the most amazing of them.

• Rock paintings found in Spanish cave of Altamira ancient man, created in the era of the Upper Paleolithic (10 thousand years ago). Drawn horses, bison, wild boars are made in several colors. Moreover, the ancient artist was able, using the unevenness of the wall, to achieve a three-dimensional effect for his images!
• In the small Australian town of Coober Pedy, located in a very hot area, almost the entire population (about 2 thousand people) lives in caves. City facilities are also located there, incl. cemetery.
• In the Luray Cave (Virginia, USA), an organ has been installed that includes stalactites in its design. It turns out an unusual, interesting sound.

Over time, we will place on the site all the collected by us Interesting Facts and put them in a separate section!

Five of the most interesting caves in the world, open for inspection

1. Waitomo Caves ( New Zealand, North Island).
2. Jaita caves (Lebanon).
3. Cuevas del Drak (Spain, Mallorca).
4. Kungur ice cave (Russia, Perm region).
5. Mulu caves (Malaysia, Borneo).

The caves are one of the most interesting objects Land for study and inspection. Ancient people reverently attributed the creation of caves to giants and inhabited them with immortal monsters guarding Realm of the Dead. Now we ourselves have become giants, but we have not ceased to admire these amazing creatures nature.

Every year, thousands of speleologists and cavers penetrate this mysterious and exciting underground universe to hear the ringing silence, see the world, plunged into darkness for thousands of years, recognize it and ... freeze with delight.

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

Caves are empty spaces in rocks underground or under water, as well as above ground. Caves are through with several holes or with one. They are divided into horizontal, vertical, as well as inclined and single-level or multi-level. The size of the cave also varies. 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 composed, and how they were formed.

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

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

Volcanic caves appear during volcanic eruptions, when lava solidifies, creating a kind of pipe through which it flows further, forming voids. Caves in the vents of volcanoes 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 formed very quickly.