On the surface, karst forms are represented carrami, gutters and ditches, ponors, funnels different types, depressions, hollows, blind valleys(fig. 8.1).
Stone cavities are oval depressions sunk into the surface of the rock. If they form under a stronger surface crust and expand deeper, it is called a taphon. If the superficial crust is not developed, the cavities are usually small and narrowed. Stone cavities are formed by the processes of selective weathering and abrasion, especially mechanical weathering, chemical weathering. They provide shelter for lower plants and some animals. The honeycombs form an irregular, more or less dense network of tiny, usually 1-5 cm deep wells that resemble hive cells.
Karry is a variety of shallow excavations formed mainly by the leaching of limestone by surface atmospheric waters. N. A. Gvozdetsky, one of the experts in karst, identified the following types of carrs: dimple, tubular, grooved, grooved, fissured and a number of others (Fig. 8.2 and Fig. 16 in the color insert). All these forms have a depth of up to 20 cm, rarely the extent of the relief reaches 1–2 m. The most typical are grooved carriages, represented by parallel grooves, separated by sharp ridges. Rel-
Honey is the result of predominantly chemical weathering and rock decay. The influence of the water contained in the rock on individual minerals is significant. For sandstones, especially cement, the individual sand grains are interconnected. The effect of water and air changes in the chemistry of the individual rock components and thus changes its strength at the surface and to a certain depth below the surface. Some sandstones have combs, others are cuckoo or completely irregular. Other honeycombs just follow a certain place in the rock.
The ef with grooved carr is reminiscent of a washboard, and the areas of development of numerous carr are called carr fields.
Troughs and ditches are more extended and deeper areas of karst leaching of the limestone surface, inheriting surface cracks and reaching a depth of 5 m.
Ponors are narrow holes, inclined or vertical, that occur at the intersection of cracks with the further development of the dissolution and leaching process. These channels serve as a runoff of surface waters and direct them into the depths of the rock mass.
Individual wells glow, gradually merge, the sections between them disappear. Examples of very old honeycombs are the so-called rock watches. Pseudo-seizures are understood as tricks developed in rocky rocks. It can also be found in quartz, granite, granodiorite. We designate small grooves, grooves and ridges on the surface of the rocks, punctured and etched with water. The most common types of pseudo-skeletons are grooves, holes, and common. The formation of these shapes involves the same processes as scratches, i.e. chemical corrosion by rainwater, humic acids, etc. But mostly mechanical erosion.
Karst funnels are subdivided into: 1) surface leaching funnels, 2) sinkholes, 3) suction tedders (corrosion-suffosion, according to N.A.Gvozdetskiy). The first type of craters resembles a crater from a shell or bomb explosion (Fig. 8.3). They are formed due to the rock leached from the surface. Usually in the center of such a funnel there is a ponor channel through which water leaves. The diameter of the funnels is usually up to 50 m, rarely more, and the depth is 5-20 m. The sinkhole funnels are associated with the collapse of the vault over the cavity worked out by the waters at a certain depth. Corrosion-suffusion funnels arise when karst limestones are overlain by a layer of sandy deposits and the latter are washed into the underlying karst cavities. At the same time, from the sand layer,
These are places where the concentration of iron compounds, mainly limonite, and less often manganese. Iron components strike the rock with ocher or rusty-brown color, manganese compounds are brown or black. The deposition of these substances occurred mainly from groundwater solutions, rainwater leakage, usually above the less permeable position. These compounds are often associated with the emergence of young volcanic rocks, but they usually originate from a layer of sedimentary rocks. As more stable rock formations, these positions create the appearance of small convex weathering patterns on the rock walls.
deposits into ponores and a suction or washout funnel is formed. Suffusion processes are widespread in nature.
The saucers and depressions are small, small sinkholes. If funnels of different genetic types merge several pieces together, then a karst basin is formed with a number of depressions at the bottom. Sometimes the bottom of the hollows can be flat.
They occur as thin flat plates and plates on vertical cracked surfaces or as horizontal layers of iron-bearing sandstone or adhesives. In the Czech Republic, we find ironic inlays in parts of the Bohemian Cretaceous Basin of quartz sandstone. National park also includes 10 national reserves, 6 nature reserves and 16 national reserves. Lowest point: at the foot of the Pleshiv Plain.
Longest and deepest cave: Skalinsky Stream cave system. Figure 1 - Barrier failure. Geological structure: five paleoalpine tectonic units - kremnikum is the main building element of the territory, tourneicum is a scroll with a coronella, for example, in the Tournier basin or in the vicinity of Shtitnik, meliat, Borks and Gemericum. These parts are partially covered with young kenozoic deposits.
The fields are rather large, hundreds of meters in diameter, irregularly shaped depression, formed at the confluence of a number of hollows and craters. Including the failed ones.
Karst wells and mines are channels that go almost vertically into limestone massifs for tens and hundreds of meters with a diameter of several meters. They are formed by leaching along cracks, sometimes by surface water flows that erode limestones. Shafts are called vertical cavities with a depth of more than 20 m, and less - wells. If the mines are connected with each other, as well as with sub-horizontal passages and caves, then karst abysses are formed, reaching depths of 1000 m or more.
The siliceous cliffs have a layer of stones, which is characterized by cracks in deposits, calcareous-dolomite development with coarse moisture limestones, turning into limestone in a vise to the pad. The upper part of the silk abyss - tuyere limestone, Hallstatt limestone. Jurassic deposits are preserved only in some parts. Chalky precipitation - Yasovskaya planina. Quaternary deposits - on the slopes of aircraft.
Relief Slovak Karst began to form between the junior and senior Quaternary pickups and the relative drawdown, which arose hollows and troughs, which were fleshed out under the influence of denudation processes and erosion of rivers. The Slovak Karst is characterized by high plateaus, steep plains, valleys, valleys and valleys.
Blind valleys are small rivers flowing in karst areas, having a source, but suddenly ending at some funnel or ponora, where all the water goes. Sometimes the valleys are half-blind, when the water of the river suddenly goes underground, and then, after a few kilometers, reappears, as it happens in the Western Crimea near Sevastopol. The Su-uksu River, starting on the slopes of the mountains, suddenly disappears, and then only its dry valley with pebbles continues. After 10-12 km, the river reappears as a powerful source and already as a river. Black flows into the Sevastopol Bay. It should be noted that such blind and half-blind valleys are widely developed in places where karst rocks are spread - in the Urals, in Bashkiria, in the Leningrad, Smolensk, Nizhny Novgorod regions, in the Crimea and the Caucasus.
Karst topography: It was formed by the hydrosphere on the lithosphere. Karst forms are forms formed by dissolving lime with water. Part of the karst is caves and slopes. There are several morphological types of caves - horizontal, vertical and cave cavities.
The Slovak Karst is located on the border of the ocean and continental type climate and lies on the pass of lowland and mountainous climate. Warmest month: July. Coldest month: January. Average annual quantity precipitation: 630 mm - 990 mm. Although exploring karst and caves is usually considered just a hobby of a limited group of applause-cavers, many people love to visit open caves in the Czech Republic and abroad and visit karst areas in Croatia, Slovenia, Provence, Kentucky. South-East Asia and other places.
In some areas of the European Plain, lakes are known that suddenly disappear and then reappear. The fact is that these lakes are located in karst basins or sinkholes. The ponors present in them are clogged with silt, and then the water in the lakes is kept. But if such a "plug" is washed out, then the water goes into a sinkhole and deeper into the karst cavities.
Karst territories are also beautiful for us studying them - their names do not come from beauty. In its original meaning, the term "hail" meant a rocky landscape south of the Alps with countless springs of water and vegetation, overcoming which for medieval pilgrims was like suffering to overcome a sandy desert. However, karst areas mean, in addition to tourist attraction, areas of economic importance and sources of unique mineral resources and, above all, water.
Thus, the study of karst and caves helps to decipher their development and contributes to protection and sustainable use. Since every story has a beginning, let's go back to the late seventies. However, in the Central European region, researchers in caves were the first to use the paleomagnetic method to refine geochronological data. Time shortens us to the mid-90s, when one of us regularly attended a working symposium in Slovenia. It was a period of over-building of infrastructure - especially highways.
Karst caves arise in various ways: by dissolution, leaching and erosion; by collapse, opening and subsequent erosion of tectonic cracks. Groundwater, flowing through cracks or fractured tectonic zones, gradually dissolves and leaches limestone or dolomite. Thus, cave cavities are formed, often multi-storey and complex, when separate large caves - "halls" - are connected to other narrow channels, cracks, often with streams flowing along them.
During their construction, the remains of the caves appeared along with the fillings; but there were no ceilings in the cave, limestone limestones were dissolved as a result of chemical denudation, which steals more or less part of the rock and gradually reveals deeper parts of the karst massif and partially or completely fossilized caves. Local specialists were pleased with the results as the motorway building companies allowed them to study in detail. On the other hand, they were somewhat helpless - they used various dating methods available, especially biostratigraphic ones, but to no avail; the cave sedimentary layers of the cave were either completely sterile, or rare remains were destroyed and not identified.
Large cave complexes have been forming for a long time - tens and hundreds of thousands of years. Many important paleontological and archaeological finds have been made in the caves, which make it possible to date the upper floors of the caves to an older age than the lower ones. The development of caves is closely related to fluctuations in the level of the groundwater table and the local basis of erosion, such as a river, as well as tectonic movements. When lowering the mirror groundwater the already depleted cave cavities are drained, and the process of dissolution and leaching goes to a lower level. This can continue several times according to the stages of cutting the river and fluctuations in the level of groundwater. In the area of permafrost in caves, drip-like forms, consisting of ice, are developed.
In this situation, we suggested to our Slovenian colleagues from the Karst Research Institute of the Slovenian Academy of Sciences and Arts in Postojna that we would try to reuse the paleomagnetic method to determine the age of deposits. Despite a rather primitive sampling method, the paleomagnetic properties of sediments have been successful. It was quite a miracle, and the results that were surprisingly surprising for local residents and somewhat overturned by the interpretation of the cave sediment epoch and the concept of the development of the Karst and the Classic Karst caves, we presented in the next school of Karras.
At the bottom of the caves are often found reddish clay deposits, the so-called "terra-rossa", or "red earth", which is an insoluble part of carbonate rocks, enriched in iron and aluminum oxides. However, the most impressive feature of the series karst caves are stalactites and stalagmites - bizarre dripstone formations that create a unique appearance of cave halls (Fig. 8.4). The thing is that the water dripping from the ceiling of the caves is saturated with CO gas due to the dissolution of carbonate rocks, and in addition, it is saturated with calcium bicarbonate - Ca (HCO,) 9. This happens by reaction
After the lecture there was a long silence, as in a temple, and then several requests from the first two; In the end, Ivan Gams said "the musician" everyone talked about and accepted. All photos: Andrey Mievts, Author's archive. Markov Caves Spodmol in Postojna, Classic Karst. Profile of rhythmically laminated sediments.
This was the beginning of building a multi-state and multidisciplinary team of karst and geochronological exploration teams. Individual jobs are methodologically augmented - some specialize in paleontology, others in numerical dating, in our paleomagnetism jobs, etc. the study gradually spread to Slovakia and Italy, Hungary, South Korea, Macedonia, Greece, and also recently also to Austria. Of course, the work also took place on the territory of the Czech Republic - especially during the reconstruction of the accessible caves.
CaCO 3 + CO 2 + H 2 0 ^ Ca (HC0 3) 2.
This water, dripping from the ceiling, loses some of its carbon dioxide, as a result of which the reaction shifts to the left and bicarbonate again passes into CaCO 3, which is deposited both on the ceiling of the cave (stalactite) and on the bottom (stalagmite). First of all, on the floor of the cave there are influxes, similar to the melted wax of a candle. These are the so-called gurus. Then stalagmites with a wide base appear on the guras, and even later - resembling a stick or a pillar. Much later, stlactites, very similar to ordinary icicles, begin to form on the ceiling of the cave. After some time, stalactites and stalagmites can close together, and then bizarre columns are formed. There are beautiful multi-tiered caves in the mountains of the Crimea, where they formed in thick strata of limestones of the Upper Jurassic; in the Czech Republic, Slovenia, the Urals, the Caucasus and elsewhere.
Why are we dealing with karst and caves? Karst systems represent a unique source of paleogeographic and paleoclimatic information - kras serve as a trap that stores information. The most important data carriers are karst sediments. In the zone temperate climate both on the surface of karst areas and in numerous caves, large-scale karst deposits or blankets are widespread in many karst areas; only subsurface cavities are present.
Karst inequalities and voids retain faults, chemical and organic particles in natural environment life of the cave. They hold a record that can be missed from karst and is absent in many geological past periods in the stratigraphic record. This feature is characterized by the dynamics of the cave environment.
Until now, it was about open karst. However, in many areas, especially platform areas, where closed karst is developed, there are
the so-called suffusion funnels. They arise when the process of leaching into karst cavities begins from the strata of deposits overlapping karst forms. Gradually, a funnel is formed in place of this stratum, and even lower - cavities, into which these deposits can fall (Fig. 8.5).
Profile panorama in multi-layer shell floors with fossil clay inserts. Acquaintance with the processes of karstogenesis and speleogenesis is based mainly on the dating of karst deposits and correlation deposits in a non-fractured environment and obtained indirectly from the development of karst relief, valleys and other geomorphological elements and units. Comprehensive knowledge of karst sediments, their composition, storage method and, in particular, their age, makes it possible to decipher global paleogeographic and other changes.
But not everything is so simple and unambiguous. Cave sediments represent a challenging research goal and especially dating. It is clear that only sediments can be found at the entrance to the cave and not far from it - these are the sediments of the so-called entrance fractions; there is a well-developed bedding, the content of paleontological and archaeological remains is significant, and each layer has its own meaning and position. Problematic is the fact that sediments belonging to this environment are rarely included in the fossil record.
Karst forms develop wherever karst rocks are present - limestone, dolomite, gypsum, anhydrite, rock salt. Covered karst is widely developed within the Russian plate, since the Carboniferous and Devonian limestones are everywhere overlain by moraine and fluvioglacial Quaternary deposits. There is also an ancient karst, for example, near Moscow, where clayey Upper Jurassic pockets lie in karst forms on the surface of Carboniferous limestones. During the Permian, Triassic, Early and Middle Jurassic, this area was dry land and intensive karst formation took place on it.
 Rice. 8.5. Suffusion funnel in the lower reaches of the river. Pakhra (photo 3. Vinogradov) |
Gypsum karst is developed on the northern slopes of the Ufa plateau in Bashkiria, where the Lower Permian red-colored rocks with interlayers of gypsum and dolomites are widespread. Karst basins there have depths of up to 100 m and a diameter of up to several kilometers. The gypsum karst caves in Transnistria are 142.5 km long (Optimistic cave), ranking second in the world. The famous Kungurskaya "ice" cave in the Perm region in the Urals is 5.6 km long and formed in gypsum and anhydrite of the Kungurian stage of the Lower Permian. It is famous for its 150-160 m long grottoes with ice ceilings on the vaults and floors.
End of work -
This topic belongs to the section:
GRAVITATIONAL FIELD OF THE EARTH
The laws of falling bodies on Earth were studied by Galileo Galilei (1564-1642). He was the first to determine the magnitude of the acceleration of gravity (gravity): g = 9.8 m / s2. They were installed independently
EARTH'S MAGNETIC FIELD
More than 400 years ago, W. Hilbert suggested that the Earth itself is a magnet, but the mechanism of the emergence of its magnetization has not yet gone beyond the scope of the hypothesis.
Minerals
All substance crust and the Earth's mantle consists of minerals that are diverse in shape, structure, composition, abundance and properties. All rocks are composed of minerals or products
Rocks
Rocks are natural mineral aggregates that form in the lithosphere or on the Earth's surface during various geological processes. The bulk of the rocks are
STRUCTURE OF THE EARTH'S CREST
grains, as a rule, increase with increasing temperatures of metamorphism (Fig. 2.26). In the previous section, the general internal structure earthly
RELATIVE GEOCHRONOLOGY
One of the main tasks of geology is to recreate the history of the development of the Earth and its individual regions. This can be done only if the sequence of geological events is known, if we know
Lt; »J
/ L f L
ISOTOPE METHODS FOR DETERMINING THE AGE OF MINERALS AND ROCKS
Numerous attempts to find a natural clock in the macrocosm that would make it possible to reliably establish the age of rocks and ores, the time of manifestation and duration of geological processes have not been crowned
P (1CHCHn J
235JJ 207pb 207pb
TECTONICS OF LITHOSPHERIC PLATES - MODERN GEOLOGICAL THEORY
In the 50s. XX century geological and geophysical studies of the Earth were carried out extremely intensively. This was especially true of the oceans, about the structure of the bottom of which and even more about the structure of the earth's crust in
WEATHERING
Most of the geological processes on the Earth's surface are due to the action of solar energy and gravity. Such processes are called exogenous. All rocks under the influence of the whole
PROCESSES OF HYPERGENEV AND WEATHERING CRUST
The hypergenesis zone is understood as the surface part of the earth's crust, continuously exposed to various exogenous factors and in which rocks tend to enter into equilibrium with a continuous
FORMATION OF SOILS AND THEIR PROPERTIES
Almost the entire land surface is covered with a thin layer of soil, energetically and geochemically very active, in which the interaction between living organisms, the atmosphere, the hydrosphere and
GEOLOGICAL ACTIVITIES OF SURFACE FLUID WATER
Water currents do tremendous geological work on the land surface. Rivers, streams, streams carry the bulk of weathering products to lakes, seas and oceans. Annual solid runoff (you
TEMPORARY WATER FLOWS
Temporary water flows occur when atmospheric precipitation or snow melts. The rest of the time, runoff in flat conditions leads to the formation of ravines, since some channelless sweat
GEOLOGICAL ACTIVITIES OF RIVERS
Rivers flowing on all continents except Antarctica do a lot of erosional and accumulative work. The high flow and regime of rivers depend on the way they are fed and on the climatic
RIVER MOUNTAINS, DELTA AND OUTDOOR
Large rivers flow into seas and oceans, smaller rivers into lakes and large rivers... In the place where the channel of the lower course of the river - the mouth - goes out to the sea, an independent landscape and geologist is formed
DEVELOPMENT OF RIVER VALLEYS AND FORMATION OF RIVER TERRACES
In its development, any river goes through a number of stages: from youth to maturity.
GEOLOGICAL ACTIVITIES OF GROUNDWATER
All waters found in the pores and cracks of rocks below the Earth's surface are groundwater. Some of these waters move freely in the upper part of the earth's crust under the influence of gravity.
TYPES OF WATER IN ROCKS
There are several types of water in rocks. 1. Crystallization water is part of the crystal lattice of some minerals, for example, in gypsum - CaS04 2H2
TRAFFIC AND GROUNDWATER REGIME
The groundwater table behaves depending on the relief, rising at watersheds and lowering to rivers, ravines and other drainage sites. Naturally, the water in the aquifer under the influence of
UNDERGROUND WATER AND THE ENVIRONMENT
Hydrogeological processes occurring in the upper part of the earth's crust are closely related to economic activities people - water supply, operation of urban agglomerations, justification of construction
KARST PROCESSES
Karst processes develop in rocks soluble by natural surface and underground waters: limestone, dolomite, gypsum, anhydrite, rock and potassium salts. The basis is n
GRAVITATION PROCESSES
If rocks become unstable, then one fine moment, under the influence of gravity, a collapse or landslide may occur. There can be many reasons for creating instability. This
GEOLOGICAL ACTIVITIES OF LAKES
A lake is a depression on the surface of the land - a basin partially filled with water. Lakes do not have a direct connection with oceans or seas and are most widely developed in areas of humid water.
GEOLOGICAL ACTIVITIES OF BOLOTS
A swamp is an accumulative formation characterized by temporary or permanent excessive moisture, the presence of moisture-loving vegetation and the presence of peat deposits. Moisture
WIND GEOLOGICAL ACTIVITIES
Wind is one of the important geological agents that change the face of the Earth. He performs geological work everywhere, but very unevenly. The work of the wind will be much more intense where
DEFLATION AND CORROSION
Deflation is the blowing of loose, disintegrated rocks from the Earth's surface, and corrosion is the grinding of rock ledges with solid particles carried by streams
ACCUMULATION OF EOL MATERIAL
Wind-blown dust particles, "flowing" sands, hurricane-thrown debris and pebbles must accumulate somewhere, forming strata of aeolian deposits. Dust, volcanic ash and the smallest
DESERT TYPES
Deserts are grouped into types based on whether they are dominated by deflation or different ways of accumulating loose material. Stony (rocky) deserts, or gammads, represent the sob
GEOLOGICAL ACTIVITIES OF SNOW, ICE AND GLACIERS
In the modern era, 11% of the land, or 17 million km2, is occupied by glaciers and ice sheets, with a volume of about 30 million km3. Of these, 98% falls on the continental covers, 2% - on the shelf
DESTROYING (EXARATIVE) ACTIVITIES OF GLACIERS
The term gouging is used to refer to the eroding activity of the glacier, which occurs due to the tremendous pressure, movement of the ice, and the impact on the glacier bed included in
TRANSPORTATION AND ACCUMULATIVE ACTIVITIES OF GLACIERS
During its movement, the glacier captures and carries various material, ranging from fine sand to large blocks weighing tens of tons. They get into the body of the glacier in various ways.
WATER-GLACIAL SEDIMENTS
Large continental ice sheets, when they melt, supply a huge mass of water. Entire rivers flow along the surface of the edge of the glacier, inside it and under the ice, creating tunnels in it. St
Sh1shshshshshshch
Rice. 13.7. Scheme of water migration and sorting of clastic material in loose rock (after A.K. Orvin, 1942). a - the beginning of freezing and water migration; b - pushing debris to the edges, because in the center
FOLDING VIOLATIONS
Observing strata of rocks, crumpled into folds, it seems that the forms of folds are infinitely varied. In fact, they can be reduced to several basic types and can be easily distinguished in the seeming chaos of different
BREAKING VIOLATIONS
Until now, we have been talking about such deformations of rock strata that did not violate the continuity of the stratum, although the stratum in this case could be very bent. In other words, even in the most difficult folds, you can
EARTHQUAKE MECHANISM AND ITS PARAMETERS
An earthquake of a tectonic type, that is, associated with the internal endogenous forces of the Earth, is a cracking process that occurs at a certain finite speed, and not instantaneously. He is before
EARTHQUAKE DISTRIBUTION AND THEIR GEOLOGICAL POSITION
Spread to the globe earthquakes are extremely uneven (Fig. 18.7). Some places are characterized by high seismicity, while others are practically aseismic. Concentration zones
EARTHQUAKE FORECAST
Despite all the efforts of various researchers, it is not yet possible to predict the decade, year, month, day, hour and place where an earthquake will occur. A seismic strike occurs suddenly and
SEISMIC CONSTRUCTION AND SOIL BEHAVIOR DURING EARTHQUAKES
All construction in earthquake-prone areas is carried out according to special requirements aimed at increasing the strength of buildings. These are special foundations; and methods of fastening the walls of buildings; and
MAIN STRUCTURES OF THE LITHOSPHERE
Continents and oceans have different crustal structures and ages. The continental crust has a thickness of up to 75 km, on average 40 km, and, as already mentioned, consists of three layers (from top to bottom):
HUMAN AND GEOLOGICAL ENVIRONMENT
The past century was marked by an unprecedented human attack on the natural, including geological, environment, which is understood as the most superficial part of the earth's crust, subject to man-made
ACHIEVEMENTS IN THE STUDY OF THE EARTH
Second half of XX century. was marked by indisputable achievements in the study of not only the Earth, but all the planets Solar system... The decisive factors were advances in technology and technology. Mankind
THE CONCEPT OF NONLINEARITY IN GEOLOGY
What was stated in the previous sections shows the variety of tasks of geology as a science. However, they ultimately boil down to one main task - to predict deep and near-surface zones.
HEAT FIELD OF EARTH
The temperature of the surface part of the earth's crust depends almost entirely on solar radiation, but daily and seasonal temperature fluctuations do not penetrate deeper than several tens - hundreds of meters. Sun
More varied. The rivers work in dungeons, the depth of which reaches several kilometers.
Underground relief are countless caves and abysses, mines and craters. The waters flowing here in complete darkness rarely break through to the surface. Underground lakes are like black mirrors. They are full of secrets, cave pearls are hidden in them. This is such a peculiar world, the nature of which is still poorly understood. This is the world of stalagmites and stalactites. All this is called karst relief, or simply karst. The term "karst" comes from the name of the Karst (Kras) plateau, which is located on one of the peninsulas in the Adriatic. The almost waterless plateau is replete with funnels, dry hollows, sinkholes, cracks, bottomless wells. - a complex of forms created by nature as a result of dissolution with water and precipitation of the dissolved material. Karst landforms range in size from the first centimeters (karr, holes, furrows, etc.) to many hundreds of meters and kilometers. Little is known about uneven terrain less than 1 cm in size.
Karst topography usually forms in areas composed of water-soluble rocks. Most often they are limestone, dolomite, gypsum, anhydrite, marble, saline clay and salt. Dissolution occurs at a high rate, which is why this group is even called karst rocks. But shale, sandstone, granite, quartzite, basalt, etc. are also susceptible to dissolution. Their dissolution rate is tens of thousands of times less than that of karst rocks.
Karst formation occurs because there are not only rocks that can be dissolved, but also flowing water and cracks in rocks. A person sees the later stages of karst formation, since it is impossible to observe the migration of water along the thinnest cracks. The mechanisms of karst relief formation at the first stages are most likely associated with the permeability of the rock. The most common forms of karst relief are funnels, saucers, mines, wells, karr, valleys, polia, caves, cauldrons, dams and curtains, terraces, stalactites, stalagmites, etc.
Carr are usually formed on the surface of fractured limestones and dolomites by rainwater, the trickles of which create gullies. Huge karr fields are located in, their depth reaches several meters. Karst sinkholes on the surface are more common. Their diameter is from 1 to 500 m, and the depth is from 0.5 to 45 m. Chains of craters often merge, forming karst valleys.
In the Rhodope Mountains (South) there are amazing creatures of nature - rock bridges. They are huge arches thrown over large valleys, along the bottom of which a barely noticeable stream now flows. These are the remains of ancient underground valleys that crossed this part of the Rhodope 1.5 million years ago. For many millennia, underground waters have dissolved marbles, destroyed the walls of caves and created a fantastic world of dungeons. Finally, the walls of the caves could not stand it and collapsed, pushing the bed of the underground river aside. The height of the "wonderful bridges" reaches 30 m, and the width is 50 m. Here, in the niches of the former, parking lots are open ancient man, discovered stone axes, ceramics.
The Karst Plateau (territory i) is a rocky desert that amazes with its dull appearance. There is no water and no greenery to be seen. Its surface is covered with cracks, pits, potholes and craters. There are also rivers, but they flow beneath the surface of the earth in dark and damp underground channels. In addition to lack of water, at every step, the traveler is expected by deep cracks, gaps, bottomless wells. There are areas where craters literally, like pockmarks, dug the surface. Their number reaches 150 pieces per square kilometer. Red-brown clays with rubble found at the bottom of the craters are the product of not only the chemical dissolution of limestone, but also the washout along the cracks of the karst massif, as well as dust brought by the wind.
Shafts and wells are narrow, almost vertical channels created by the expansion of cracks. The diameter of the wells is different - from 0.3 to 350 m, the depth can reach 1300 m. Karst valleys, occupied by the channels of both underground and surface rivers, are characterized by a sharp stepwise longitudinal profile. Strange rivers emerge from the cave, flow for several kilometers on the surface, and then hide again in the cave. These valleys have no floodplain, no terraces, no floods or floods. A special type of karst is polya - closed or semi-closed hollows. The areas of the fields reach 500 - 600 km2, depth - hundreds of meters, width - 10 - 15 km. One of them - in the northwestern part of the Dinaric Highlands - covers an area of 380 km2. The axis of the basin coincides with the direction of the mountain ranges and the orientation of the folded structures. During periods of heavy rainfall, thin soil particles are washed off and gradually all cracks are filled with water. This leads to the termination of filtration, and precipitation contribute to the silting up of depressions.
Karst caves are deep underground. They are very diverse in size and configuration, which is explained not only by the occurrence of karst rocks, but also by a certain stage of their development. In caves, among the numerous forms of karst associated with the accumulation of solute, stalactites and stalagmites are mainly known. Lime icicles - stalactites - reach a height of several meters and a thickness of 1.5 - 5 m. During the growth of stalactites in the water, the content of CaCO3 decreases. The precipitated calcium carbonate cements the clastic material and forms carbonate incrustations. Stalagmites - calcareous pillars and cones - grow from bottom to top and reach a height of 15 - 20 m. All this happens very slowly. It is estimated that the 19 m high stalagmite in the Carlsbad Cave formed about 50 million years ago. The drip forms of karst relief include dams that block underground passages... Lakes appear behind such dams. But the age of the dams is younger than the stalagmites - 9-10 thousand years. Under the influence of warm humid monsoons, limestone rocks undergo karsting, as a result of which many bizarre landscapes arise: either sheer cliffs rise above the abyss, or yawns in the mountains deep caves, then stone bridges are thrown across the rivers. All this is called tower karst. In some areas where limestone rocks have been destroyed, rounded valleys with a flat bottom have formed. In such valleys, at the same distance from each other, cone-shaped limestone hills rise, and at their foot there are stepped fields like an amphitheater, which makes each hill look like a giant castle with fortress walls and watchtowers. Sometimes in the valleys small hills with sharp peaks are visible, from a distance resembling huge haystacks. Karst valleys, as a rule, are very wide, and in the middle of them there are often blocks of limestone.
In the warm and humid conditions of the tropics karst relief takes on bizarre forms. There are domed hills and ridges, towers, sharp cones, karst plains. The systems of rounded domes are dissected by gorges that have arisen along tectonic fractures. The periphery of the domes is framed by tower karst. Karst hollows and plains are separated by jagged ridges and deep hollows. Limestone debris that fell from the slopes of towers or domes quickly collapses.
The dense vegetation that covers the slopes contributes to the activity of waters with a content of acids of different compositions. Therefore, as a rule, debris does not accumulate at the foot of karst hills or small mountains. Weathering turns them into sand and clay, which are quickly carried away by jets of water during rainy periods. The highest intensity of karst processes is in wet areas, and the lowest in dry ones.
Flowing water dissolves not only carbonate and saline, but also silicate rocks, in which this process is thousands of times slower. Sandstones, granites, shales and other crystalline rocks dissolve. River water flowing through such rocks in the humid tropics contains a lot of soluble silica. The relief forms associated with silicate karst are diverse. On in South America dips, wells, mines, funnels are observed in quartzite. On the Guayquinima plateau in quartzites, even a system of caves with a length of about 2 km with horizontal passages and deep wells was discovered.
Giant mines with a diameter of 350 m and a depth of more than 500 m are observed on the Roraima plateau, composed of ancient quartzites. Based on the analysis of quartzites, which contain silicate karst, it can be concluded that dissolution of both quartz grains and silicate cement occurs here. Moreover, the process should not stop for tens and hundreds of millions of years.
The forms of silicate karst are formed as a result of both dissolution of rocks and their biochemical weathering.
