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.
High hydraulic gradient created by steep terrain or entrenched rivers. Moving water corrodes much faster than standing water. All other factors are equal to the steep gradient of a fast flow. Therefore, a high hydraulic gradient reduces the residence time, thereby hindering the development of equilibrium between the rock and the surrounding waters. High level precipitation: more water.
High biological activity. As discussed in the weathering lecture, plants, algae and lichens not only release acids, but are also responsible for increasing the amount of carbon dioxide entering the groundwater system. Blue-green algae can form surface karst, characterized by pitting and sharp relief ridges and peaks. This epilitic karst plant is called phytokarst.
Karst landform usually forms in areas 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.
Organic waste: Phosphate-rich guano, produced by birds and bats, highly corroded limestone. Rock phosphate, formed by the reaction of guano and limestone, fills karst cavities, in some cases to a depth of 20 m, forming commercial sediments.
- Humus also releases organic acids.
- Algae: produces phytokarst.
Classic dinar Karst-Slovenia and Montenegro. The karst form of the Czech Republic is developed almost exclusively in various types of limestones, and less often in dolomite limestones belonging to the main geological and geomorphological units of the Bohemian Massif and the Outer Western Carpathians.
Karst formation occurs because there are not only rocks that are amenable to dissolution, but also flowing water and cracks in rocks. A person sees the late 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.
The most important karst regions, that is, the Moravian karst, the Czech karst and the predominant part of the karst regions of northern Moravia, are developed in Devonian limestones and, more rarely, in Silurian limestones and dolomite limestones. They are non-metaphoric or only slightly metamorphosed, but they are severely damaged and bend during orogenesis.
Surface forms of karst
Most of the small karst areas were developed in crystalline limestones, metamorphosed of varying intensity in the Moldavian, Lugansk and Moravian-Silesian parts, in the central Czech metamorphic islets, etc. carbonate rocks mainly belong to the Paleozoic era.
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.
Jurassic limestones show limited karstification at Lugikum. Large karst areas are developed in the Klippen belt of the Outer Western Carpathians in the eastern part of the republic. Cretaceous limestones belong to the limited development of facies of the Czech Cretaceous Basin. A clear karstification can be traced to the west of the town of Kutná Hora.
The karst regions of the Czech Republic are predominantly small islands with imperfectly developed karst morphology and a limited variety of karst forms. Only the Moravian Karst is a more developed karst zone with overseas karst phenomena, including free underground water flows. Due to the dominant lithology of karst rocks, our karst regions are carbonate karst, belonging to the Central European type of polycyclic and polygenetic karst.
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.
This is an isolated type of karst that develops through repeated karstification under changing climatic and geomorphological conditions. Hydrothermal karst, primarily described from the Araganit Zbrashov cave, is a special type of karst. It developed due to the activity of penetrating thermal mineral waters through the limestone massif.
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Specificity karst areas reflects, for example, their differentiated geomorphological evolution. Due to the small area of carbonate outcrops, the variety of karst forms is very limited. Karst areas have basically identical geomorphological evolution with the geomorphological subdivision to which they belong. With the exception of the Moravian Karst and several other karst regions, their expression in the relief is the same. They usually form eminences or short ridges, eventually morphological depressions.
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 funnels 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.
The dominant part of the surface of carbonate rocks is covered with weathering products and other sedimentary covers of variable age and genesis. Sedimentary cover accelerates the karst process, in a confined space, or, conversely, slows down the development of karst, turning karst into a fossil state. Evidence of previous karstations is usually preserved under sediments.
The oldest proven karstification period occurred during the deposition of Lower Paleozoic carbonate rocks and consists of several local karstification phases. A number of fossil karst forms were the result of this period, hidden under chalk in the Czech and Moravian karsts. The youngest period of karstification lasts from marine retreat in the Upper Cretaceous to the present. The most important underground cave systems developed during the Tertiary are in the Bohemian, Moravian and North Moravian karsts, as well as some other isolated karst islands.
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 disappear into the cave again. 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.
The above-mentioned karstification phases gave rise to typologically different karst forms depending on tectonic, climatic and hydrological conditions. The evolution of karst areas also differed in different regions... Pseudo-karst phenomena often occur in the Czech Republic. They are represented by karst and morphologically similar forms developed in non-karst rocks. They are especially rich in thick Upper Cretaceous sandstone sequences of the Bohemian Cretaceous Basin. Caves developed along cracks, bedding planes, and in block debris are common as well as cracks and niches.
Karst caves are located 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: sometimes they rise above the abyss sheer cliffs then the mountains are gaping 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 flat bottoms 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.
Some of these natural forms have been modified by humans. Features developed in calcareous spongylites, rocks and limestone sandstones of the Czech Cretaceous Basin are often classified as transitional or karst forms. The most extensive systems of pseudokarst cracks and talus of caves and mines are developed in the sandstones and marls of the muhshi zone of the Western Carpathians.
Syngenetic heterogeneities are probably the basis of cavities in the volcanoclastic rocks of the Doupovskie mountainous hills. Pseudo-map cavities, i.e. mainly covered with open cracks, cracks and cavities in talus in isolated rocks and rocky cliffs, found in places throughout the territory of our republic. They develop in solid rocks with blocky decays, especially in igneous and metamorphic rocks.
In the warm and humid conditions of the tropics, the 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 cracks. 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.
Our Karst Heritage Think about Ireland's natural heritage and what comes to mind? Some of the finest karst landscapes and features in Europe are found in Ireland. Why should the best examples of these functions be preserved? We owe future generations to preserve our heritage so that it can become their Karst, has a distinctive character. For conventional three-dimensional landforms, karst landforms add a “fourth dimension,” namely underground landforms, a kind of negative replica of surface drainage patterns to which it is closely related. Karst areas are of particular beauty both for local residents and for visitors. The tourist potential of areas such as the Burren Cave and the Marble Arch does not need to be developed. They are fundamental to understanding and appreciating our historical, environmental and archaeological heritage... They are often the only source of drinking water, especially in rural areas.
- They are an integral part of our natural heritage.
- Conservation has direct and immediate benefits to humanity.
- They are a valuable scientific and educational resource.
The dense vegetation that covers the slopes promotes the activity of waters with different acid 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.
Arterial drainage can change not only the landscape, but also a much more water regime - main distinctive characteristic karst areas. Overexploited and intrusive tourism can reduce visual appeal and pose a threat to the ecology of karst areas. Development where inadequate attention to waste disposal can lead to pollution groundwater karst, and in this process affect the ecology. Irresponsible treatment of caves can lead to damage, loss of amenities and the educational, scientific and archaeological value of the caves.
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.
The need for natural stone for gardens has emerged from recent threats. The stone covered in water from the limestone sidewalks is very attractive and has been removed in many places by heavy mechanical work, leaving a scarred surface that will take centuries of weathering before it is restored to its former condition. Stone should not be removed from any limestone sidewalk for garden use. Satisfactory substitutes should always be available from quarry waste or reclaimed stone.
The Heritage Council and the UK Countryside Agency noted the scale of the limestone pavement trade. What do you need to keep? Our goal should be to preserve the best examples of the main features of karst. The “best” can be viewed at the international, national and county levels. Main features: caves, limestone pavement, turlaphs, streams, karst springs and karst landscapes.
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.
Achievement of successful conservation Achievement of successful conservation presupposes: selection of sites worthy of conservation; determination of practical methods of site management; availability of a good legal framework, supported by site monitoring; and raising public awareness and support. The official recognition and designation of sites is just one step. Conservation must be supported by landowners who are the custodians of these special zones for all, and the public must, in turn, support them and their efforts.
The forms of silicate karst are formed as a result of both dissolution of rocks and their biochemical weathering.
The relief is divided into surface, transitional and underground.
If the karst rocks directly overlook earth surface, that is open or naked karst. If they are covered from above by non-karst sediments, then this is covered karst .
Naked Karst occurs in mountainous areas, and covered - on the plains. Stands out yet indoor karst, which is noted in areas where karst rocks are thick and contain a large number of various impurities.
After the soluble part of these rocks is completely leached, a weathering crust is formed, not completely red in color and is called terra rossa(red earth). V further development the karst underneath this crust proceeds in the usual way. This karst is called closed.
In the area of open karst, under the influence of rain or melt water, a microrelief is formed on the surface of limestones carrow... This is a system of ridges and furrows separating them, up to 2 m deep. Such a surface is called tar fields.
Transitional forms connect surface and underground zones. In places of increased fracturing of limestones, with vertical circulation of water, ponors, that is, channels absorbing surface waters... When they expand, sinkholes having a slit or saucer shape. With a large expansion, cracks turn into wells and shafts that can reach great depths. Example: the depth of the Snezhnaya mine in the Caucasus is 1370 m.
Failure, or surface funnels, when merged, form blind ravines, ridges and the largest karst forms - polya... The fields are vast, usually flat-bottomed, with steep walls, karst depressions several kilometers, and sometimes several tens of kilometers across. So, the Popova polya area in Yugoslavia is 180 km 2.
Polya may have tectonic origin, that is, karst develops in large tectonic cracks. Sometimes they are formed due to a sinkhole over an underground river, or by erosion and removal of products of erosion of insoluble rocks that occur among limestones.
TO underground forms karst include caves and chasms.
Caves called underground cavities formed in karst areas and having one or more outcrops to the surface. They are formed when water expands underground cracks. In many caves, on the bottoms, walls or vaults, drip forms... On the ceiling in the form of icicles - stalactites, at the bottom of the cave - stalagmites. When they merge, drip columns are formed. There are often underground rivers in the caves. They originate either in the area of the karst massif, or begin outside of it. Sometimes underground rivers come to the surface.
Karst landforms (according to D.G. Panov)
1 - punishments; 2, 3 - surface leaching funnels; 4 - sinkhole funnel; 5 - karst valley; 6 - polie; 7 - cave.
Literature.
- Smolyaninov V.M.General geography: lithosphere, biosphere, geographic envelope... Study guide / V.M. Smolyaninov, A. Ya. Nemykin. - Voronezh: Origins, 2010 - 193 p.
