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, 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 🙂

The first written evidence of the existence of an unusual state of the soil, later designated as “permafrost”, remained from Russian explorers of the 17th century who conquered Siberia. The Cossack Y. Svyatogorov became the discoverer, and members of the expeditions I. Rebrova and S. Dezhneva have already studied the issue in more detail. In their dispatches to the court, they described the peculiarity of individual zones in the taiga, in which, even in summer, the earth retains winter frost. In 1640, the governors M. Glebov and P. Golovin, in a message to the Russian Tsar, did not hide their sincere bewilderment:

The earth, my lord, does not melt even in the middle of summer.

They finally established themselves in the existence of areas of "permafrost" during the beginning of the industrial development of the North. In 1828, the drifter F. Shergin cut through the first meter of ice soil in Yakutsk, reaching a mark of just under 116 and a half meters in 9 years and not meeting a single aquifer on the way. A. Middendorf, having measured the temperature throughout the Sherigin mine, drew a line under the answer. Thus, the unbelievable became an obvious fact of the geography and geology of the country.

Permafrost of the Yamal Peninsula in the north of Western Siberia, on the territory of the Yamalo-Nenets Autonomous Okrug of Russia.

The concept of "permafrost" first appeared in the scientific community in 1927. The author of the term was the Soviet scientist M.I. Sumgin, one of the founders of domestic science to study this phenomenon.

scientific definition

Under the permafrost, it is customary to consider the cryolithozone with a temperature regime of 0 ° C and below and, accordingly, the presence of underground ice in it. According to Sumgin, this is soil permafrost with an age of 2 years or more, the maximum accumulation values ​​are measured in millennia.

For a while there was a certain confusion in terminology. The meaning of the word "permafrost" did not have a clear definition, which led to inconsistencies. This position was justly criticized and therefore other names were proposed. There were attempts to widely disseminate the names "permafrost rocks", "perennial cryolithozone". But as a result, Sumgin's term stuck.

The period during which the frozen state of rocks is formed divides them into three types:

• Short-term frozen rocks (for hours and days),
• Seasonally frozen rocks (for months),
• Permafrost (for years)

A separate category includes intermediate or transitional forms of frozen rocks. They are called flights. An example is the case when seasonally frozen rock does not have time to thaw during the summer period and persists for several years.

A large proportion of today's permafrost resulted from the impacts of the last ice age. Ice volumes in frozen rocks can be up to 90 percent. Nowadays, the process of their slow melting is observed.

Features of frozen soils

Low temperatures in permafrost conditions, which are of a long seasonal or permanent nature, naturally leave their mark on the state of the local soil. In it, peculiar chemical and biological processes take place. One example is shown in the photo on the left.

Humus accumulates above the frozen water-resistant layer in the process of coagulation (thickening) of organic substances. Moreover, its supra-permafrost regeneration or the so-called supra-permafrost gleying does not strongly depend on the graces of nature. For the process to start, a small amount of annual precipitation is enough.

The schlieren (ice layers) formed in the ground, breaking the aquifer capillaries, block the access of moisture from the upper permafrost horizons to the lower root-inhabited environment. All phenomena occurring in the soil under permafrost conditions are especially characteristic of. As a result of mechanical changes in the soil due to the presence of a frozen layer, the tundra acquired its own special appearance. Cryogenic deformations in the form of cryoturbation (mixing under the influence of the temperature difference of the soil mass) and soliflucation (sliding of the soil mass saturated with water from the slopes along the frozen layer) gave the tundra relief undulating outlines, when swollen mounds alternate with dips of thermokarst depressions. For the same reason, spotted tundras formed.

Minus temperatures also affect the structuring of the soil, causing its cryogenic character. They force the products of soil formation to pass into more condensed states, while sharply slowing down their mobility. Soil ferrugination occurs as a result of permafrost coagulation of colloids. According to some researchers, cryogenic phenomena also enrich the middle part of the podzolic soil profile with silicic acid. These scientists consider the whitish powder to be the result of permafrost differentiation of the soil plasma.

Distribution areas

Permafrost has a global distribution. She captured at least ¼ of the land of the earth, including the highlands of Africa. Australia is the only continent where this phenomenon is absent at all.

The vast expanses of Russia are the focus of permafrost. More than half of the territory of the largest country in the world falls on the cryozone. It is most widespread in Transbaikalia and Eastern Siberia, where the lowest point of permafrost lies in the upper part of the Vilyui River at a depth of 1370 meters. The record was set in 1982.

Economic impact

Accounting for permafrost is important for construction, exploration and other economic work in the regions of the North. It can both create problems and be beneficial. The ability to serve as a natural refrigerator for food storage lies on the surface. In addition, in permafrost conditions, the formation of hydrate deposits of gases used by humans, in particular methane, is likely.

The high strength of frozen rocks makes mining very difficult. But at the same time, there is another, strong side: the permafrost cements the rocks, which made it possible to successfully develop kimberlite pipes in the quarries of Yakutia, bringing the walls of the bowls to a sheer state. A striking example of the latter is the example of the Yakut quarry Pipe Udachnaya.

The Igarsk Museum of Permafrost is a unique phenomenon, not only because its main exhibition halls are located in the thickness of permafrost, but also because the main exhibit of the museum is the permafrost itself.

From the first years of the construction of the city, scientists conducted its research, the permafrost station was opened in 1931. Along the way, the idea of ​​demonstrating to the population the results of a careful attitude to nature was hatched. This idea belonged to the permafrost scientist Mikhail Ivanovich Sumgin, who visited the research station in 1938. By that time, shaft wells and counter drifts to them were dug. A year before the start of World War II, five cells were equipped by excavation, separated from the corridor by partitions and doors. Their walls, like the corridor, were lined with a thin layer of ice. The volume of excavated soil was 468 cubic meters.

The constructed premises were of research value, but nevertheless, for those who wished, primarily schoolchildren and guests of the city, the first excursions were already conducted by the station staff. So one of the chambers, in fact, already then began to be used as a biomuseum. Its exhibits were frozen lizards, ruffs, hawk moth in suspended animation, insects: bumblebees, ladybug and fly. Scientists replenished the biomuseum to the best of their ability and received visitors.

As a kind of scientific experiment to study the possibility of preserving paper and in memory of the Great Patriotic War, on April 6, 1950, the station staff laid a bookmark of newspapers of the war period - Pravda, Izvestia, Trud and Krasnoyarsk Rabochy with a testament to open a box with newspapers immured in it on May 9, 2045.

March 19, 1965 is considered the official opening date of the Permafrost Museum in Igarka. The first exhibits, besides those mentioned above, were books on permafrost and plants frozen into ice. Nature seemed to be going towards enthusiasts, revealing its centuries-old secrets. In one of the walls of the corridor, during the passage, tree trunks were exposed, their sections, which make it possible to judge the age - more than 50 thousand years.

And yet it was still a museum on a voluntary basis, the rest of the premises were used as scientific laboratories. And the scientists continued to experiment: this is how the idea of ​​building an underground skating rink was born, with the possibility of its year-round use by athletes and amateurs.

On October 25, 1996, the underground laboratories of the Permafrost Research Station were taken into municipal ownership. Large-scale work was carried out to overhaul the underground part, expand and create new exhibition halls. Undoubtedly, the underground part of the museum is considered to be the main one in the local history complex "Museum of Permafrost". But there are also interesting exhibits in the departments of nature, history, construction site No. 503, and the exhibition and exposition hall. In the hall of nature, for example, located in front of the entrance to the dungeon, there are bones of prehistoric animals found in the vicinity of Igarka, including a mammoth tooth. And the guides, talking about the features of the growth of trees, demonstrate the trunk of a ten-year-old Christmas tree with horizontally running roots - this is how the trees look for the moisture they need for growth in the thawed soil layer.

A huge role in the development of the museum, its popularization was played by the first museum guide Pavel Alekseevich Evdokimov, the former director of the museum Maria Vyacheslavovna Mishechkina and her late husband Alexander Igorevich Toshchev. Their merits include not only the preservation of soils from weathering from contact with people (and this is also a whole range of measures), but also the opening and modernization of new halls, the introduction of museum traditions, and extensive publishing activities.

Water located in the bowels and on the surface freezes to a depth of 500 m or more. Over 25% of the entire land surface of the Earth is occupied by permafrost rocks. In our country, more than 60% of such a territory, because almost all of Siberia lies in the zone of its distribution.

This phenomenon is called permafrost, or permafrost. However, the climate can change in the direction of warming over time, so the term "perennial" is more appropriate for this phenomenon.
In the summer seasons - and they are very short and fleeting here - the top layer of surface soils can thaw. However, below 4 m there is a layer that never thaws. Ground water can be either under this frozen layer or remain in a liquid state between permafrost (it forms water lenses - taliks) or above the frozen layer. The top layer, which is subject to freezing and thawing, is called the active layer.

POLYGONAL SOILS

Ice in the ground can form ice veins. Often they occur in places of frost (formed during severe frosts) cracks filled with water. When this water freezes, the soil between the cracks begins to compress, because ice occupies a larger area than water. A slightly convex surface is formed, framed by depressions. Such polygonal soils cover a significant part of the tundra surface. When the short summer comes and the ice veins begin to thaw, whole spaces are formed, similar to a lattice of pieces of land surrounded by water "channels".

Among the polygonal formations, stone polygons and stone rings are widespread. With repeated freezing and thawing of the earth, freezing occurs, the ice pushing larger fragments contained in the soil to the surface. In this way, the soil is sorted, since its small particles remain in the center of the rings and polygons, and large fragments are shifted to their edges. As a result, shafts of stones appear, framing the finer material. Mosses sometimes settle on it, and in autumn stone polygons amaze with unexpected beauty: bright mosses, sometimes with bushes of cloudberries or lingonberries, surrounded on all sides by gray stones, look like specially made garden beds. In diameter, such polygons can reach 1-2 m. If the surface is not even, but inclined, then the polygons turn into stone strips.

The freezing of fragments from the ground leads to the fact that on the summit surfaces and slopes of mountains and hills in the tundra zone, a chaotic heap of large stones appears, merging into stone “seas” and “rivers”. For them there is a name "kurums".

BULGUNNYAKHI

This Yakut word denotes an amazing form - a hill or hillock with an ice core inside. It is formed due to the increase in the volume of water during freezing in the supra-permafrost layer. As a result, the ice lifts the surface layer of the tundra and a hillock appears. Large bulgunnyakhs (in Alaska they are called the Eskimo word "pingo") can reach up to 30-50 m in height.

On the surface of the planet, not only belts of continuous permafrost in cold natural zones stand out. There are areas with the so-called island. It exists, as a rule, in the highlands, in harsh places with low temperatures, for example, in Yakutia, and is the remnants - "islands" - of the former, more extensive permafrost belt that has been preserved since the last.

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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 masses.

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 diversity of 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 heat turnover and the heat balance of 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.
In 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 up 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 border 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 at 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 is found 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 the 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.

There are 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 permafrost boundary runs along the coast of the Pacific Ocean, not reaching it a little, then it passes along the western slope of the North American Cordilleras, crossing them at about 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 the southern coast of Hudson Bay and, leaving the Labrador Peninsula to the north, it goes to the coast of the Atlantic Ocean.

The permafrost also includes the islands of Greenland and Iceland.

In the southern hemisphere, permafrost covers the entire continent of Antarctica and 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 that are characteristic of the regions of the permafrost zone are, in general, the following: negative average annual air temperature, dry, cold long winters, short summers, low precipitation, 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 coincide to some extent 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 visible, 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. In this case, roof ruptures and outpouring of water on the surface with the formation of ice can 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.

On a significant part of the land - on 25% of its area, where the average annual temperatures are negative, at a certain depth from the surface of the rock they have a negative temperature for many years. Layers of rocks with a negative temperature are called permafrost layers - permafrost ("permafrost"). Permafrost can be dry and waterless, but much more often it contains frozen water, and sometimes liquid water is also present.
The boundary of permafrost on the Eurasian continent divides the Kola Peninsula into the northern (larger) and southern (smaller) parts and from the throat of the White Sea along the Arctic Circle goes to the Urals. In the Ural Mountains, the border bends sharply to the south, and then goes to the West Siberian Plain and crosses it from the Ob (the city of Tobolsk) to the Yenisei (the mouth of the Podkamennaya Tunguska). Along the right bank of the Yenisei, the border descends to the south, captures part of the territory of the Mongolian People's Republic, again enters the territory of Russia near the city of Blagoveshchensk and, making a slight bend to the south, turns to the Tatar Strait. The boundary of permafrost runs along Kamchatka in such a way that only a strip along the coast of the southern half of the peninsula remains beyond its borders. In North America, permafrost occupies the Yukon, Mackenzie, Hudson Bay, and northern half of Labrador basins (Fig. 86).
Permafrost has been noted on the Arctic and Antarctic islands. The question of the presence of permafrost on land covered with continental ice (Greenland, Antarctica) cannot yet be considered clarified.
The permafrost boundary is mobile. At present, there is some retreat to the north.
On the territory located inside the permafrost distribution boundary, areas with continuous permafrost, areas with taliks and insular permafrost.

The temperature of permafrost at a depth of 15-20 m varies from -0.1 to -1.2°, depending on the set of conditions (relief, vegetation, snow cover, etc.). Beneath the “runoff strips” (rivers or groundwater streams), the temperature rises and often there is no permafrost at all or it lies deeper than in neighboring areas.
The thickness of permafrost is different (from a few meters to 600-800 m). In general, the power increases in the direction from middle to high latitudes. The greatest thickness of permafrost - 800 m - was noted on the coast of the Khatanga Bay. The lower limit of permafrost depends on the arrival of heat from deeper earth layers.
Above the permafrost, on the surface, there is a layer of seasonal permafrost, which thaws in the warm season. The thickness of this layer is determined by climatic conditions and reaches 5 m. When permafrost is deep, it is separated from seasonal permafrost by a layer that does not freeze at all.
Underground waters in permafrost conditions are distinguished by great originality. The ice formed when water freezes in the pores of the rock cements the rock, making it waterproof. In some places there are accumulations of underground ice ("rock ice"): lenses, layers, veins buried under a layer of rock or wedged into the rock. In permafrost, supra-permafrost, inter-permafrost and sub-permafrost groundwaters are distinguished.
suprapermafrost waters- water of the seasonal permafrost layer. They feed on atmospheric precipitation, water from ground ice melting in summer and are not abundant. Usually these waters are weakly mineralized, with the exception of highly mineralized waters that accumulate in drainless basins. When the temperature drops below 0°, the supra-permafrost water exerts pressure on the water that has not yet frozen, the latter accumulates in places with the lowest pressure and, freezing, raises the already frozen upper layers, forming hydrolaccoliths and mounds (bulgunnyakhs). Water that breaks through to the surface turns into ice mounds - ice. In the warm season, supra-permafrost waters come to the surface in numerous sources.
Interpermafrost waters are located in the very thickness of the permafrost and can only be in an unfrozen state if they are in motion. More often they can be observed in the areas of taliks. Interpermafrost waters connect suprapermafrost waters with subpermafrost ones; while their movement can be downward and upward. In the first case, they feed on supra-permafrost waters and their qualities (temperature, salinity) are dependent on external conditions; in the second, they feed on subpermafrost waters and have properties in common with them.
subpermafrost waters never freeze and often have pressure. The degree of their mineralization is different, the temperature increases with depth. From the groundwater of regions without permafrost, subpermafrost waters differ in terms of supply and discharge. These waters are fed through taliks, and when they come to the surface, they form ascending springs. All three types of water interact under the valleys of large rivers and in the basins of lakes, i.e., where there is no permafrost.
The emergence of permafrost is possible at low temperatures with a low thickness of the snow cover, which is unable to protect the rocks from freezing. Such conditions existed during the Ice Age in areas not covered with ice, and now exist where winters are severe and with little snow, and summers are so short that the layer frozen in winter does not have time to thaw (for example, in Yakutia). Permafrost could have been preserved as a relic of the last epoch of glaciation, but it can also occur in modern conditions. The emergence of permafrost is observed on newly formed islands in river deltas flowing into the Arctic Ocean.