Hello! Imagine such a situation that you are in an ice age... Wouldn't want to, right? But on Earth there are places that remind him a little, which will be discussed in this article...
In these so-called periglacial (paraglacial) regions, an even more amazing phenomenon occurs. It is a repeating pattern of mud deposits and rock on flat areas of the surface.
Polygons (polygons bounded by cracks) are the largest such figures; there are also stone rings. Similar patterns are formed as a result of thrusting and heaving, which are replaced by thaws, over thousands of years.
Mountain landscapes.
Permafrost landscapes are found not only in high latitudes (near the poles), but also high in the mountains. Even on the tops of the mountains located on the ice caps lie. An example, the East African city of Kilimanjaro, 5895 m high.
The reason for the formation of integuments from perennial and ice in hot latitudes is that the temperature with increasing altitude, for each next kilometer, drops by 5 - 10 ° C.
Similar mountain peaks in the Southern Hemisphere are found in New Zealand, Australia, New Guinea and the South American Andes.
Many mountains in the Northern Hemisphere are covered with ice caps all year round, even on the tops of some low mountains, such as the Scottish, snow and ice lie for a significant part of the year.
In the alpine, or mountain, tundra, there is no permafrost at all, or there may be very little of it. Melt water has time to seep into the depths, so there is not much dirt on the surface. Here, as in the Arctic tundra, the main plants are mosses, lichens, and shrubs, which make up the diet of mountain goats and deer.
Personally, I don't like winter, cold and always look forward to summer. So, I would not even want to get into this permafrost 🙂
Modern glaciers occupy a small area on the territory of Russia, only about 60 thousand km 2, however, they contain large reserves fresh water. They are one of the sources of river nutrition, the importance of which is especially great in the annual flow of the rivers of the Caucasus.
The main area of modern glaciation (more than 56 thousand km 2) is located on the Arctic islands, which is explained by their position in high latitudes, which determines the formation of a cold climate.
The lower boundary of the nival zone here descends almost to sea level. Glaciation is concentrated mainly in the western and central regions, where more precipitation falls. The islands are characterized by cover and mountain cover (network) glaciation, represented by ice sheets and domes with outlet glaciers. The largest ice sheet is located on the North Island New Earth. Its length along the watershed is 413 km, and its maximum width reaches 95 km.
As you move eastward, more and more of the islands remain ice-free. So, the islands of the archipelago Franz Josef Lands almost entirely covered by glaciers New Siberian Islands glaciation is typical only for the northernmost group of islands De Longa, and on the island Wrangel there is no cover glaciation - only snowflakes and small glaciers are found here.
The thickness of the ice sheets of the Arctic islands reaches 100-300 m, and the water supply in them approaches 15 thousand km 2, which is almost four times the annual flow of all Russian rivers. The glaciation of the mountainous regions of Russia, both in terms of area and volume of ice, is significantly inferior to the cover glaciation of the Arctic islands. Mountain glaciation is typical for the highest mountains of the country - the Caucasus, Altai, Kamchatka, mountains of the North-East, but also occurs in low mountain ranges of the northern part of the territory, where the snow border lies low (Khibiny, the northern part of the Urals, the mountains of Byrranga, Putorana, Kharaulakh mountains), as well as in the Matochkina Shara area on the Northern and Southern islands of Novaya Zemlya.
Many mountain glaciers lie below the climatic snow limit, or "365 level," at which snow remains on a horizontal underlying surface for all 365 days of the year. The existence of glaciers below the climatic snow limit becomes possible due to the concentration of large masses of snow in negative landforms (often in deep ancient kars) of leeward slopes as a result of snowstorm transport and avalanches.
The area of mountain glaciation in Russia is slightly more than 3.5 thousand km 2. The most widespread karovye, karovo-valley and valley glaciers. Most of the glaciers and glaciation areas are confined to the slopes of the northern points, which is due not so much to the conditions of snow accumulation, but also to greater shading from sun rays(insolation conditions). In terms of glaciation area among the mountains of Russia, it occupies the first place Caucasus(994 km 2). It is followed by Altai (910 km 2) and Kamchatka(874 km 2). Less significant glaciation is typical for the Koryak highlands, the Suntar-Khayat and Chersky ranges. Glaciation of other mountainous regions is small. The largest glaciers in Russia are the glacier Bogdanovich(area 37.8 km 2, length 17.1 km) in the Klyuchevskaya group of volcanoes of Kamchatka and the glacier Bezengi(area 36.2 km 2, length 17.6 km) in the Terek basin in the Caucasus.
Glaciers are sensitive to climate fluctuations. In the XVIII - early XIX centuries began a period of general reduction of glaciers, which continues to this day. The internal waters of Russia are represented not only by accumulations of liquid water, but also water in the solid state, which forms modern cover, mountain and underground glaciation. The area of underground glaciation is called the cryolithozone (the term was introduced in 1955 by the Soviet permafrost specialist P.F. Shvetsov; earlier, the term " eternal Frost").
Cryolithozone -- top layer earth's crust, characterized by negative temperatures of rocks and the presence (or the possibility of existence) ground ice. It consists of permafrost rocks, underground ice and non-freezing horizons of highly mineralized groundwater.
In the conditions of a long cold winter with a relatively small snow cover, the rocks lose a lot of heat and freeze to a considerable depth, turning into a solid frozen mass. In summer, they do not have time to completely thaw, and negative ground temperatures persist even at shallow depths for hundreds and thousands of years. This is facilitated by the huge reserves of cold that accumulate during the winter in areas with a negative average annual temperature. So, in Central and North-Eastern Siberia, the sum of negative temperatures during the period of snow cover is -3000...-6000°C, and in summer the sum of active temperatures is only 300-2000°C.
Rocks that are at temperatures below 0 ° C for a long time (from several years to many millennia) and are cemented by moisture frozen in them are called permafrost, or permafrost. Ice content, i.e. The ice content of permafrost can be very different. It ranges from a few percent to 90% of the total rock volume. In mountainous regions, ice is usually scarce, but on the plains, underground ice often turns out to be the main rock. Especially a lot of ice inclusions are found in clayey and loamy deposits of the extreme northern regions of Central and North-Eastern Siberia (on average from 40-50% to 60-70%), which are distinguished by the lowest constant ground temperature. Permafrost is an unusual phenomenon of nature, which was noticed by explorers in the 17th century. It was mentioned in his works by V.N. Tatishchev (beginning of the 18th century). First Scientific research permafrost was carried out by A. Middendorf (mid-19th century) during his expedition to the north and east of Siberia. Middendorf for the first time measured the temperature of the frozen layer at a number of points, established its thickness in the northern regions, and suggested the origin of permafrost and the reasons for its wide distribution in Siberia. In the second half of the XIX century. and the beginning of the 20th century. permafrost was studied along with exploration work by geologists and mining engineers. AT Soviet years major special studies permafrost M.I. Sumgin, P.F. Shvetsov, A.I. Popov, I.Ya. Baranov and many other scientists.
The area of distribution of permafrost in Russia occupies about 11 million km 2, which is almost 65% of the country's territory (see Fig. 1).
Rice. one.
Its southern border runs along the central part of the Kola Peninsula, crosses the East European Plain near the Arctic Circle, deviates south along the Urals to almost 60 ° N, and along the Ob - north to the mouth of the Northern Sosva, then passes along the southern slope Siberian Uvalov to the Yenisei in the area of Podkamennaya Tunguska. Here the border turns sharply to the south, runs along the Yenisei, goes along the slopes of the Western Sayan, Tuva and Altai to the border with Kazakhstan. On the Far East the permafrost boundary goes from the Amur to the mouth of the Selemdzha (the left tributary of the Zeya), then along the foothills of the mountains on the left bank of the Amur to its mouth. There is no permafrost on Sakhalin and in the coastal regions of the southern half of Kamchatka. Permafrost spots are found south of the border of its distribution in the Sikhote-Alin mountains and in the highlands of the Caucasus.
Within this vast territory, the conditions for the development of permafrost are not the same. The northern and northeastern regions of Siberia, the islands of the Asian sector of the Arctic and the northern island of Novaya Zemlya are occupied by a continuous low temperature permafrost. Its southern border passes through the northern part of Yamal, the Gydan Peninsula to Dudinka on the Elisei, then to the mouth of the Vilyui, crosses the upper reaches of the Indigirka and Kolyma and goes to the coast of the Bering Sea south of Anadyr. To the north of this line, the temperature of the permafrost layer is -6...-12°С, and its thickness reaches 300-600 m and more. Distributed south and west permafrost with talik islands(thawed soil). The temperature of the permafrost layer is higher here (-2...-6°С), and the thickness decreases to 50-300 m. Near the southwestern margin of the permafrost area, there are only individual spots (islands) of permafrost among the thawed soil. The temperature of the frozen ground is close to 0°C, and the thickness is less than 25-50 m. island permafrost.
Large reserves of water are concentrated in the frozen mass in the form of underground ice. Some of them were formed simultaneously with the host rocks (syngenetic ice), the other - when water freezes in previously accumulated strata (epigenetic). The large thickness of the permafrost, the findings of well-preserved mammoths in it, indicate that permafrost is a product of a very long accumulation of cold in the rock masses. The vast majority of researchers consider it a relic of the ice ages. The modern climate in most of the permafrost area only contributes to its preservation, so the slightest disturbance of the natural balance leads to its degradation. This must be taken into account in the economic use of the territory within which permafrost is widespread.
Permafrost affects not only groundwater, the regime and nutrition of rivers, the distribution of lakes and swamps, but also many other components of nature, as well as human economic activity. In the development of minerals, laying roads, construction, and agricultural work, it is necessary to carefully study the frozen soil and prevent its degradation.
Permafrost and its features
Remark 1
Permafrost (or permafrost, permafrost, permafrost, permafrost) is part of the permafrost zone, which is characterized by the absence of periodic thawing. The total permafrost area of the planet is 35 million square meters. km. This is about 25% of all land. Completely permafrost is absent in Australia. In Africa, permafrost occurs only in the highlands.
The most extensive areas of permafrost:
- northern Alaska;
- north of Europe;
- Canada;
- North of Asia;
- Antarctica;
- Islands of the Arctic Ocean.
Permafrost regions occupy the upper part of the earth's crust. The temperature in these territories does not rise above 0 ºС (for several millennia). The groundwater in this zone is permanently in the form of ice. The soil freezes up to 1 km deep. The record freezing depth is 1370 m.
In permafrost, deposits of methane hydrate are formed.
According to various sources, from 60% to 65% of the territory of Russia is permafrost. It is more widely distributed in Transbaikalia and Eastern Siberia. The highest limit of permafrost is located in Yakutia in the upper reaches of the Vilyui River.
Accounting for permafrost is very important when carrying out geological exploration, construction and other work in the northern regions.
Study of permafrost
Some of the first descriptions of permafrost were made by Russian explorers of the 17th century who conquered the expanses of Siberia. For the first time, Ya. Svyatogorov drew attention to the state of the soil cover. Later, the soils were studied by the pioneers Ivan Rebrov and Semyon Dezhnev. They pointed to the presence of special taiga zones in which the soil does not thaw even in summer. In 1640, M. Glebov and P. Golovin confirmed that the earth does not thaw in the middle of summer.
As a special geological phenomenon, the concept of "permafrost" was put into use by the founder of the permafrost school in the Soviet Union, M.I. Sumgin in 1927. He pointed out that this concept implies the permafrost of the soil, which persists from two years to several millennia.
The term "permafrost" has often been criticized, so alternatives have been proposed: permafrost and permafrost. But these options are not widely used.
The concept of "frozen rocks" according to the duration of the existence of rocks in a frozen state is divided into such concepts as:
- short-frozen rocks (day, hours);
- seasonally frozen rocks (months);
- permafrost rocks (tens, hundreds and thousands of years).
Between these species there are mutual transitions and intermediate forms. So, seasonally frozen rock during the summer may not thaw and exist for several years. Such forms are called "flights".
Permafrost is by origin a relic of the glacial epochs of the Quaternary period. In the post-glacial period, climate warming was observed, which led to the thawing of frozen rocks and the reduction of their distribution areas. This proves the insular nature of the distribution of permafrost, the existence of certain species and parts of flora and fauna in the thickness of frozen rocks, and an active thawing process.
Not all scientists agree with this point of view. Some believe that permafrost is a modern phenomenon. As proof, they cite observations of the development of permafrost on islands recently formed in the deltas of large Siberian rivers. main reason permafrost occurs - long winters with little snow and low temperatures and short summers, during which ice accumulates in the soil, as it does not have time to melt.
Soil cover of permafrost areas
Specific soil structures are formed in permafrost areas, including stone and peat circles, stone garlands, polygonal cracks, and stone stripes. These structures, formed under the influence of cryogenic processes, are located on the tops of many mountains.
In soils located in the zone of permanent or long-term seasonal permafrost, a set of processes occur that depend on the impact of low temperatures. Above the frozen layer - aquiclude - due to coagulation organic compounds there is an accumulation of humus, or supra-permafrost regeneration of humus, gleying even with a small annual volume of precipitation.
The formation of schliers (layers of ice) in the soil contributes to the rupture of capillaries, as a result of which the pulling of water from the suprapermafrost horizons to the root layer stops.
Ring structures can result from both soil freezing and water freezing. When water freezes, mainly peat circles are formed, which are associated with variable thawing and freezing of water, rupture and expansion of the soil layer. When the soil freezes and subsidence cracks appear, stone rings are formed. Spring meltwater flows into cracks, carrying out fine-grained material and leaving coarse detrital material on the surface. This is how a polygonal system of cracks is formed.
The presence of a frozen layer causes such processes as:
- soliflucation - sliding along the frozen layer from the slopes of the soil mass saturated with water;
- cryoturbation - mixing of the mass of the soil cover under the influence of a temperature difference.
These phenomena are especially widespread in the tundra zone. Cryogenic deformations determine the formation of patchy tundras and a characteristic hilly-depression relief, including heaving hillocks and thermokarst depressions.
Cryogenic soil structuring occurs under the influence of low temperatures. The negative temperature regime contributes to the transition of the products involved in the processes of soil formation into more condensed forms, which will greatly slow down their mobility. The influence of cryogenic phenomena is associated with the enrichment of the middle part of the profile of subgolden soils with silicic acid. At the same time, the whitish powder is considered as a consequence of the permafrost differentiation of the soil plasma.
Cryogenic coagulation of colloids determines the ferruginization of taiga soils.
Seasonal frost. Seasonal freezing - thawing and their causes. The tilt of the earth's axis to the plane of the ecliptic determines the change of seasons on Earth. The result of the change of seasons is the periodic seasonal freezing and thawing of some near-surface horizon of the earth's crust. Seasonal fluctuations in heat supply and consumption, with its constant deficit in zones gravitating towards the poles, eventually lead to the development of permafrost. The seasonal change of seasons leads to the fact that a layer of seasonal (summer) thawing is formed above the permafrost, freezing in winter, and outside the permafrost area - layers of seasonal freezing, thawing in summer.
Southern border of the Eternal, permafrost
Rice. 1. Scheme of changing the depth of seasonal freezing - thawing:
1 - zone of potential seasonal thawing, 2 - seasonally freezing and thawing rocks, 3 - permafrost.
In addition to the layer of winter freezing and summer thawing, which is characteristic of middle and high latitudes and in some places of southern latitudes, a short-term frozen state of rocks occurs at times, lasting several hours or, less often, several days.
The patterns of seasonal permafrost phenomena are illustrated by the graph (Fig. 1).
It can be seen from the graph data that the actual depth of seasonal freezing and thawing is greatest at the southern border of permafrost. To the north of it, it is less due to the actual decrease in the depth of seasonal thaw (i.e., the depth of potential thaw), and to the south it is less due to the lower depth of actual freezing.
active layer. The layer of seasonal freezing and thawing is called the active layer. There is a layer of seasonal thawing, located above the permafrost, and a layer of seasonal freezing above the thawed substrate. In this case, they proceed from the premise that there is a permanently frozen rock stratum (permafrost) and a permanently thawed stratum (outside the permafrost region). The first is characterized by seasonal thawing, i.e. potential seasonal freezing is veiled by the presence of permafrost; the second is characterized by seasonal freezing, since potential thawing is not manifested here due to the small depth of winter freezing. Therefore, the names are given - seasonal thaw layer for the permafrost area and layer of seasonal freezing - for the area outside the permafrost. Today, other names are increasingly used: active layer over permafrost, referring to seasonal freezing and thawing over permafrost and active layer over thawed substrate, referring to seasonal freezing over the thawed rock mass.
In the active layer, the most significant annual temperature fluctuations occur, the largest part of the annual heat turnover takes place, and physical, physico-chemical and geological processes develop most intensively. This is the intermediate layer through which the heat exchange of the Earth's surface with the permafrost takes place. Seasonal freezing and thawing in the active layer predetermines the direction and nature of physical, physicochemical and geological processes, which, in turn, determine the features of the cryogenic structure and properties of frozen rock strata.
Geographic distribution of seasonal freezing very large. In fact, it is observed everywhere, with the exception of the subtropics and tropics, where it is possible only in high mountains. In the area of permafrost, the active layer is ubiquitous. It is absent only in the case when the permafrost lies directly under the glacier, cover or mountain. Then the frozen state (glacier ice) starts from the day surface. In Greenland, frozen soil was found under glacier ice, 2 to 5 m thick. According to M. G. Grosswald, icy rock was found under glacier ice on Franz Josef Land.
Active layer power depends on a complex of physical, geographical and geological factors and varies from a few centimeters to 3-5 m, rarely up to 8-10 m.
The thickness of the active layer is variable from place to place due to the usual variegation natural conditions on the surface, as well as lithological heterogeneity and spatial changes in soil moisture.
Even within the same area of the terrain, the depth of seasonal freezing and thawing is not the same from year to year. But this depth, with the invariability of climatic and other physical and geographical conditions, fluctuates around a certain constant average value.
The change in the depth of freezing and thawing from north to south depends on:
From the degree of continental climate;
From the duration of winter cooling;
From the average annual air temperature;
From the mean temperature of the coldest month;
From the amplitude of temperatures on the surface;
From the sum of negative temperatures;
From the nature of the soil, that is, from whether they are represented by boulders and gravel, or sand and clay, or peat, etc.
The process of seasonal freezing and thawing depends on the degree of moistening of the type of soil, as well as on the density and thickness of the snow cover, the nature of the vegetation cover, surface moistening, etc. Moss cover and peat play a special role in seasonal freezing. Moss and peat act as heat insulators in a dry state, due to the abundance of air in them, and as coolants, due to their high hygroscopicity. The abundance of water favors evaporation and, consequently, cooling (the latent heat of evaporation of water is 7.25 times greater than the latent heat of melting ice).
Soil filtration and thaw depth are causally related: the greater the filtration, the greater the thaw depth.
The depth of seasonal freezing and thawing, i.e., the thickness of the active layer and its temperature regime, are determined by the heat exchange between the soil and the atmosphere. The thickness of the active layer depends on the heat exchanges and heat balance rocks.
If over a number of years there is an increase in the depth of seasonal freezing, which is not compensated by a corresponding increase in the depth of thawing in summer, usually thin frozen horizons are formed in the rocks, which
can exist from one to several years and represent the prototype of permafrost. Such frozen horizons are called flights.
In this case, the winter heat cycles in rocks at negative temperatures exceed the summer heat cycles at positive temperatures. At the same time, the average annual temperature of the rocks drops below 0°. If the heat turnover at positive temperatures again exceeds the heat turnover at negative temperatures, the overshoots will disappear.
Processes taking place in the active layer. The active layer is such a horizon of the earth's crust, within which the most active, most dynamic processes of rock transformation take place: their disintegration to a dust fraction, soil formation, soil heaving, solifluction, all processes leading to the formation of a permafrost microrelief, seasonal hydrolaccoliths, etc. d.
Of particular importance is the moisture regime of the soils of the active layer, and especially if they are represented by fine-grained varieties - clays, loams, etc. The density, composition, occurrence conditions and nature of the soils (lithologically homogeneous or heterogeneous) are also essential.
Seasonal freezing rates different. In the north, the rate of seasonal freezing is 1-3-5 cm, per day. Full freezing is reached already in November - December. In the south, with a high thickness of the active layer, seasonal freezing occurs during the entire period of cooling, i.e., throughout the winter.
Seasonal thaw rates usually slower.
Permafrost. permafrost - these are frozen rocks characterized by temperatures from 0 ° and below, containing ice in their composition and being in this state for a long time - from several years to many millennia.
Permafrost on the globe is distributed mainly in the polar and circumpolar regions, as well as in high-mountain regions of temperate and even tropical latitudes, and occupies about 25% of the entire land area of the Earth. These are vast territories in the north and northeast of Eurasia and North America, this is all of Greenland and all of Antarctica. In Russia, permafrost occupies about 60% of the area.
AT Western Europe permafrost is possible only in the Alps. In the European part of Russia, permafrost is common in the Far North - in the tundra and forest tundra. From the Kola Peninsula, where it is available only in its northern part, the southern
the permafrost border goes to the mouth of the river. Mezen and further almost along the Arctic Circle to the Urals, shifting here quite strongly to the south. Within Western Siberia the border occupies an almost latitudinal position to the river. Yenisei near the mouth of the river. Podkamennaya Tunguska, where it turns sharply to the south and, following along the right bank of the river. Yenisei, goes beyond the borders of Russia, delimiting significant areas of Mongolia. Again, the southern boundary of permafrost appears in Russia west of Blagoveshchensk, following northeast to about 131 ° 30 "E, from where it again turns south, crosses the Amur River near the mouth of the Arkhara River and again leaves the country. Then it reappears in Russia east of M. Khingan, then goes northeast and breaks off near the shore of the Sakhalin Gulf.On the Kamchatka Peninsula, the southern border runs from southwest to northeast approximately in the middle of the peninsula
By the nature of distribution, permafrost can be divided into three zones: 1 - continuous, 2 - permafrost with islands of thawed soils and 3 - island (permafrost islands among thawed rocks).
Each of these zones is characterized by different thicknesses and temperatures of frozen strata. At the same time, even inside the zones, the power and temperature change in the direction from the north, to the south - the power decreases, the temperatures increase.
The zone of continuous permafrost is characterized by the greatest thickness of frozen strata - from 500 meters or more to 300 m and their lowest temperatures - from 2 ° C to 10 ° C and below.
Continuous permafrost in Russia is developed: in the northern part of the Bolshezemelskaya tundra, in the Polar Urals, in the tundra of Western Siberia, in the northern part of the Central Siberian Plateau (north of the Nizhnyaya Tunguska river valley), on the entire Taimyr Peninsula, on the islands of the Severnaya Zemlya archipelago, on the New Siberian Islands, on the Yano-Indigirskaya and Kolyma coastal plains and the delta of the river. Lena, on the Leno-Vilyui alluvial plain, on the Leno-Aldan plateau and in a vast area of the Verkhoyansk, Chersky, Kolyma, Anadyr ridges, as well as the Yukagir plateau and other internal highlands, on the Anadyr plain.
In the zone where there are islands of thawed rocks among the permafrost, the thickness of the frozen strata sometimes reaches 250-300 m, but more often from 100-150 to 10-20 m, temperatures from 2 to 0°C. This type of permafrost occurs in the Bolshezemelskaya and Malozemelskaya tundra, on the Central Siberian plateau between the Nizhnyaya and Podkamennaya Tunguska rivers, in the southern part of the Lena-Aldan plateau, in Transbaikalia.
Insular permafrost is characterized by low thickness of frozen strata - from several tens of meters to several meters, and temperatures close to 0°C.
Insular permafrost occurs on the Kola Peninsula, in the Kanin-Pechora region, in the taiga zone of Western Siberia, in the southern part of the Central Siberian Plateau, in the Far East, in the northern part of Sakhalin Island, along the coast of the Sea of Okhotsk and in Kamchatka.
In the mountainous zone from the Sayan Mountains to Kopet-Dag and in the Caucasus, permafrost rocks are found mainly along the periphery of glaciation regions and most often have an insular distribution. There is permafrost in the rocks that make up the bottom of the polar shelf Laptev and East Siberian seas, on the shelf north of Alaska.
Significant areas of permafrost in Central Asia. These are the areas of the Hindu Kush, Eastern Tien Shan, Nan Shan, Kun Lun, the Himalayas and the high plateau of Tibet.
On the North American continent, the boundary of permafrost runs along the coast Pacific Ocean, not reaching it a little, then it passes along western slope North American Cordillera, crosses them near 53 0 s. latitude, turns sharply to the north, following in this direction to 57 ° N. sh. Then this border goes to the southeast, reaches south coast Hudson Bay and, leaving the Labrador Peninsula to the north, it goes to the shores of the Atlantic Ocean.
The permafrost also includes the islands of Greenland and Iceland.
AT southern hemisphere permafrost covers the entire continent of Antarctica, is present in the highlands of the Andes in South America. Africa and Australia are completely devoid of permafrost.
The main features of the climate, which are characteristic of the regions of the permafrost zone, are generally the following: negative average annual air temperature, dry, cold long winters, short summer, low rainfall, especially in winter. Characteristic, therefore, is the anticyclonic state of the atmosphere in winter, which favors low precipitation, high air transparency, and strong heat losses from the earth's crust. Therefore, the largest territories occupied by permafrost in Eurasia and North America, to some extent coincide with the spaces occupied by the Asian and North American anticyclones.
Hydrogeological conditions of the permafrost region. Groundwater has a very significant impact on the formation of permafrost, permafrost, in turn, is a powerful factor in creating a specific hydrogeological environment.
The emergence of a layer of permafrost can contribute to the division into parts of one or another single aquifer, create aquicludes that were not previously noticeable, disrupt the mutual connection of surface and groundwater, localize places of supply and discharge, confining them to areas of taliks, change the direction and speed of movement groundwater, etc. Thus, in the frozen zone, very special conditions arise for the location, supply, movement and discharge of groundwater.
Groundwater affects the thermal regime of rocks. They change their thermophysical properties. The movement of groundwater causes convective heat flows. Due to the interaction of convective heat transfer with the conductive heat flow coming from the earth's interior, there is a redistribution of thermal energy in rocks, which changes their temperature field and the very conditions for the development of permafrost.
The freezing of aquifers leads to a peculiar distribution of ice in rocks, which depends mainly on the degree of water saturation of the horizon, the composition of the rocks, and also on their water permeability due to porosity, fracturing, etc. In addition, due to uneven freezing, in aquifers significant stresses and in-situ pressure often occur, as a result of which water can move under pressure towards areas with lower in-situ pressure. AT this case Roof ruptures and outpouring of water on the surface with the formation of icing may occur. If there is no breakthrough of the roof, then accumulations of ice are formed in the form of fairly large bodies - sheeted or laccolithic. Hydrolaccoliths, which form near the earth's surface, appear in the relief in the form of convex heaving mounds.
Groundwater classification:
1. permafrost waters, contained in thawed rocks above the permafrost roof. Among them, waters stand out: a) the active layer and b) perennial non-through taliks (under-channel, sub-lake, the so-called non-merging permafrost).
2. The waters of the talik zones, located in through taliks, limited by frozen rocks from the sides. The talik zones serve as the main pathways for communication between surface, subpermafrost, and interpermafrost waters. Through these zones, various types of groundwater are fed and discharged.
3. Subpermafrost waters are the waters of the first aquifer or aquifer fractured zone from the base of the permafrost. Among these waters, contacting and non-contacting waters are distinguished. The former are in one or another direct interaction with the frozen strata, the latter are not connected with it by direct interaction, i.e., they lie at a considerable depth from it.
4. interpermafrost waters, contained in thawed rocks enclosed between the horizons of frozen rocks.
5. intrapermafrost waters, contained in localized areas of thawed rocks, bounded on all sides by frozen rocks. These waters are isolated from any interaction with other types of groundwater.
When asked the meaning of permafrost, given by the author to dry the best answer is "Permafrost" (perennial cryolithozone) - part of the cryolithozone, characterized by the absence of periodic thawing. With a total area of 35 million km². Distribution - the north of Alaska, Canada, Europe, Asia, the islands of the Arctic Ocean.
Permafrost regions are the upper part of the earth's crust, the temperature of which does not rise above 0 ° C for a long time (from 2-3 years to millennia). In the permafrost zone, groundwater is in the form of ice, its depth sometimes exceeds 1000 meters.
Permafrost is a global phenomenon, it occupies at least 25% of the entire land area. the globe. The only continents without permafrost are Australia and Africa. Much of the permafrost is inherited from the last ice age and is now slowly melting. The ice content in frozen rocks varies from a few to 90%. Deposits of gas hydrates, in particular methane hydrate, can form in permafrost.
One of the first descriptions of permafrost was made by Russian explorers of the 17th century, who conquered the expanses of Siberia. For the first time, the Cossack Y. Svyatogorov drew attention to the unusual state of the soil, and the pioneers from the expeditions organized by Semyon Dezhnev and Ivan Rebrov studied in more detail. In special messages to the Russian Tsar, they testified to the presence of special taiga zones, where even in the midst of summer the soil thaws by a maximum of two arshins.
The term "permafrost", as a specific geological phenomenon, was introduced into scientific use in 1927 by the founder of the school of Soviet permafrost M. I. Sumgin. He defined it as the permafrost of the soil, continuously existing from 2 years to several millennia. The word permafrost did not have a clear definition, which led to the use of the concept in various meanings. Subsequently, the term was repeatedly criticized and alternative terms were proposed: permafrost rocks and permafrost, but they were not widely used.
65% of the territory of Russia are permafrost regions. It is most widely distributed in Eastern Siberia and Transbaikalia.
The deepest limit of permafrost is noted in the upper reaches of the Vilyui River in Yakutia. The record depth of permafrost is 1370 meters, recorded in February 1982.
Accounting for permafrost is necessary when carrying out construction, exploration and other work in the North. Thus, large houses in the regions of the north are built using special technologies, in particular, the built box of a panel house is left for several years so that the house settles down. If the soil under it begins to float, then it is dismantled and collected in a new place.
Permafrost creates many problems, but it also has benefits. It is known that food can be stored in it for a very long time. On the one hand, permafrost greatly interferes with the development of northern deposits, since frozen rocks have an exceptionally high viscosity and are difficult to extract. On the other hand, it was thanks to the permafrost, the cementing rock, that it was possible to build unique quarries in Yakutia (for example, the Udachnaya pipe quarry) with almost sheer walls). The sides of these quarries are held by ice, and in a warmer climate they would inevitably float.
Construction in the permafrost zone
The presence of permafrost in certain regions of our country poses many problems for scientists, the solution of which is of great practical importance. Most of these problems have already been solved by scientists.
Answer from Innocent[newbie]
Permafrost is soil that contains frozen water and has a temperature below zero. In this article, we will talk about what permafrost is and what types of terrain are distinguished depending on the conditions of the permafrost distribution zone.
Permafrost always contains ice, which may be in the form of crystals in the pores between soil particles or in the form of thick layers of ice in the soil. During thawing, frozen soils containing a significant amount of ice turn out to be excessively moistened. Therefore, buildings and structures that are built on such soils undergo significant settlement.
The layer of soil which cold period freezes in the spring and thaws in the spring is called the active layer. If such a layer is connected to the surface of the permafrost zone, then such a surface is called confluent. The thickness of the active layer layer depends on the exposure of the slopes, on the terrain, on the humidity and composition of the soils.
It also depends on climatic factors and vegetation cover. The ground thaws to a greater extent on the south side on the slopes than on the north side. Grass cover, trees and shrubs contribute to the fact that the permafrost is located closer under them than in other open areas. This is due to the fact that they create a shadow that prevents the everfrozen soil from thawing in depth.
For example, in peat-moss bogs that have a depth of 10 centimeters to several meters, even in the warm season, the level of frozen soil is located at a depth of no more than one meter. The thickness of the active layer averages from 1 to 2 meters in the sandy soils of the Far North. In clay and peat-bog from 0.39 to 1.29 meters. In the southern regions of frozen soils, the depth of the active layer can reach 2.5-4.5 meters. Permafrost covers 47% of the territory of the former Soviet Union. Depending on the conditions of the permafrost distribution zone, the following types of terrain are distinguished:
1. Places are dry with adequate surface runoff. Such places can be steep slopes of hills, rocky hills, areas with a close occurrence of hard rocks, and others. Such soils do not change their properties when freezing or thawing. With the provided surface runoff of melt water, the thickness of the active layer in such areas is from 2.5 meters and more.
2. Damp places with excessive moisture in certain periods of the year and signs of surface waterlogging. Such places can be gentle slopes of mountains of southern exposure, flat watersheds, composed of sandy and clay subsidence soils with a relative humidity of 0.71-0.91 from the yield point. With unsecured surface runoff, summer thawing of the soil does not exceed 2.5 meters.
More information can be found here: link