Image of the West Siberian Plain. Relief and geological structure. Excessive moisture

Siberia climate

As you know, Siberia is one of the coldest countries in the world. The most characteristic features of its climate are explained primarily by geographic location... Siberia occupies the northern part of the Asian mainland and lies in the northern and partly middle latitudes Soviet Union, within the zones of temperate and cold climates. Many thousands of kilometers separate the territory of Siberia from the coast Atlantic Ocean, high mountain ranges rise to its southern and eastern borders and prevent the penetration of warm and humid winds from the seas located to the south and east of the Asian continent. Only from the north, from the Arctic Ocean, far into the depths of Siberia, do masses of dry and cold Arctic air reach.

Almost everywhere north of the line of the Siberian Railway on the plains, plateaus and mountain ranges, a very cold winter lasts for more than six months, in the middle of which there are frosts of 40-50 °, and in some places even 60 °. However, summer in Siberia (with the exception of only its most northern regions) is warm, and in the southern half it is sometimes even hot and rather long. Already at the end of May, and in the north in June, under the bright rays of the sun, there is a strong warming of the land surface. Mercury in the thermometer rises during the day to 20–25 °, and in early July in the steppe zone, the heat often exceeds 30–35 ° for several days in a row. In almost the entire territory of Siberia, summer is much warmer than in the corresponding latitudes of the European part of the Soviet Union. In Yakutsk, which lies at the same latitude as Leningrad, the temperature in July is on average 2-3 ° higher than on the banks Gulf of Finland; the temperature difference between Kiev and Semipalatinsk is approximately the same.

The transitions from summer to winter and from winter to summer are made quickly in Siberia. Therefore, the duration of the transitional seasons - spring and autumn - is generally short.

The climate of Siberia is sharply continental throughout. The difference between the average temperatures of the coldest and warmest months in its various regions is from 35 to 65 °, and the absolute temperature amplitudes in areas such as Eastern Yakutia reach 95–105 °. The continental climate of Siberia is also manifested in rather sharp fluctuations in temperature during the day and in a relatively small amount of precipitation, which falls in most regions mainly in July and August.

The huge size of the territory and the large differences in the relief determine the significant variety of climates in individual regions of Siberia. This is primarily due to the large extent of Siberia from north to south and therefore the unequal amount of incoming solar heat. Some southern regions of Siberia receive solar heat no less than the southern regions of Ukraine and the lower Volga region. It is a different matter in the north. As you know, about a quarter of Siberia lies north of the Arctic Circle. In winter, here for several weeks, and in the very north - for two or even three months, the sun does not rise above the horizon at all and there is a "dark time" of the polar night. At the end of January, the length of the day begins to increase rapidly, and at the end of May - beginning of June, a multi-week polar day begins. The huge disk of the sun makes a full circle during the day, not hiding behind the horizon.

Polar day and night are characterized by very small fluctuations in daily air temperatures. In winter, both "day" and "night" are almost equally cold. With the onset of summer, with round-the-clock lighting and a continuous influx of solar heat, the melting of the snow cover and the development of plants are very rapid here.

The climatic differences between the western and eastern regions of Siberia are also very significant. Climate Eastern Siberia in general, it is more continental than in the western part, to the plains of which air masses from the Atlantic Ocean often reach. True, when passing over Western Europe and the Russian Plain, they lose a lot of moisture, and in winter, in addition, they also become very cold. However, the masses of Atlantic air over the territory Western Siberia nevertheless, they are more humid than the continental air of Eastern Siberia. That is why more precipitation falls in the western part.

The difference in the climates of Western and Eastern Siberia is also explained by the different nature of their relief. In Eastern Siberia with its high mountain ranges and plateaus, separated by deep valleys, accumulation and stagnation of masses of heavier cold air occurs in the depressions. This phenomenon is especially pronounced in winter. At this time, in clear and frosty weather, a very large amount of heat is radiated from the surface. Heavy supercooled air flows into the hollows, where it is even more cooled. It is this circumstance that explains the extremely low temperatures winter months and the phenomenon of so-called inversions (Usually, with altitude, there is a gradual decrease in temperature, averaging about 0.5–0.6 ° for every 100 m rise. But there are times when the temperature rises to a certain height, and sometimes quite significantly. So, for example, at the Mangazeisky mine, located in the Verkhoyansk ridge, at an altitude of about 1,000 m average temperature in January it is –29 °; in Yakutsk, located at the foot of this ridge, –43 °, and in Verkhoyansk even –50 °. This phenomenon is called temperature inversion), which are especially characteristic of intermontane depressions in Eastern Siberia.

The relief also has a very significant effect on the distribution of precipitation. It is known, for example, that slopes facing humid winds receive significantly more precipitation than opposite slopes of the same ridge. So, in Western Altai at an altitude of 1200-1500 m, sometimes more than 1500 mm of precipitation falls per year (B last years Siberian hydrologists, according to data on the amount of water flowing into rivers, found that in some areas of the Western Altai and Kuznetsk Alatau, up to 1800 and even 2 thousand mm of precipitation fall per year, i.e. almost the same as in the humid subtropics Black Sea coast Caucasus), and at the same height in the depressions of the Eastern Altai only 200–300 mm. An equally striking example in this respect is the Khamar-Daban ridge. Its northwestern slopes facing Baikal receive up to 800–1000 mm of precipitation per year, and the thickness of the snow cover in winter here reaches 1.5–2 m. On the opposite, southeastern slope, less than 300 mm falls per year; Due to the lack of snow, it is not possible to ride a sleigh there every winter.

Many of the features of the Siberian climate noted by us are due to the distribution atmospheric pressure and the circulation of air masses over the territory of Siberia and neighboring countries. It is known that the land in the cold season cools faster and more intensely than the surface of the seas and oceans. For this reason, usually from the beginning of autumn, the air above it becomes colder and denser, and the so-called anticyclonic region of high atmospheric pressure gradually forms. The Asian mainland is one of the most significant and compact land masses in the world. Therefore, the process of the formation of increased pressure in winter in the center of the continent is extremely pronounced, and the atmospheric pressure here is much higher than on the seas surrounding the continent.

Already at the end of September, the atmospheric pressure over the territory of Northeast Siberia becomes relatively high, and by the end of autumn the area of ​​increased pressure gradually spreads to the whole of Eastern Siberia. The pressure is highest in Transbaikalia and the eastern part of Yakutia. In January, it reaches here on average 770–775 mm. Due to the emergence of an area of ​​high atmospheric pressure, the penetration of humid air masses from neighboring territories here stops. This circumstance explains the clear, almost cloudless, but very cold and dry weather prevailing in Eastern Siberia in winter. The winds at this time are very rare and differ in very little force.

Unlike Eastern Siberia, over the northern part of the West Siberian lowland and especially over the seas The Pacific the pressure in the cold season is lower and sometimes does not exceed 760 mm. Due to the large difference in atmospheric pressure, cold and dry air from the East Siberian high-pressure region spreads to the west and east. Its penetration causes a significant cooling in neighboring regions, which in the west extends even to the territory of the European part of the USSR.

In the warm season, when the land heats up more than the water surface, the picture of pressure distribution over Siberia changes dramatically. Already in April, the pressure over the mainland begins to drop rapidly and the Siberian anticyclone disappears. By the middle of summer, in North Asia, almost everywhere, air pressure becomes below normal and does not exceed 755–758 mm on average. In contrast to winter in the north, over the seas of the Arctic Ocean, and in the west - in the European part of the Union, the pressure at this time is somewhat higher. Therefore, in summer, air masses often come to Siberia either from the north (Arctic) or from the west (Atlantic). The former are most often cold and dry, while the latter are more humid and bring a significant part of summer precipitation.

The wind regime is also closely related to the seasonal distribution of pressure and air masses. The coldest months of the year (December, January and February) are characterized by relatively calm weather in almost the entire territory of Eastern Siberia. Windy days in winter are usually accompanied by a noticeable increase in temperature and little rainfall.

In Western Siberia, where areas with relatively high pressure are located in the south in winter, and an area of ​​low pressure is formed over the Kara Sea, southern winds prevail. They reach their greatest strength in the middle of winter. It was at this time that blizzards and blizzards rage in treeless areas in the south of Western Siberia and in the tundra zone on the shores of the Arctic Ocean. With a tremendous wind speed, sometimes reaching 30–40 m / s in the north, the swept-up snow and ice crystals fill the surface layers of air so much that nothing can be seen even at five paces; movement in a blizzard becomes almost impossible. It is especially dangerous to be caught in the tundra, far from settlements the so-called "dark blizzard". It begins suddenly and often does not subside for five to ten days, only at times weakening somewhat. During a strong blizzard, the air temperature almost always rises by 10–20 °.

Winds have a completely different character during the warm Siberian summer. At this time, the northwestern and north winds... The first of them are wet and bring a large amount of precipitation falling in the form of rains, and the relatively cold winds of the northern points cause a strong drop in temperature in summer, and sometimes they are accompanied by frosts in May, June and August.

Due to the significant diversity of the surface in some places of Siberia, especially in mountainous areas, local winds are also observed. In Altai, in the Sayan Mountains and the mountains of Northeastern Siberia, they often acquire the character of fen (Fen is a relatively warm and dry wind blowing from the slopes of the mountains into the valleys. It occurs when different pressure is established over the opposite slopes of the ridge, or when over The pressure on the ridge crest is higher than on its sides. Descending from the slopes, as a result of compression, the air heats up and becomes dry. In the mountains of Siberia, this phenomenon is most often observed in winter. 20 and even 40 °. So, for example, on the night of December 2 to 3, 1903, as a result of the hair dryer, the temperature in Verkhoyansk rose from -47 ° to -7 °. Hair dryers often cause thaws, and in spring - rapid melting of the snow cover). In the basin of Lake Baikal, which is surrounded on all sides by mountain ranges, very peculiar winds blow. Many of them are remarkable for their surprising consistency of direction. Such is, for example, the north-east wind “barguzin”, the south-west wind, or “kultuk”, and the north one, called by the local population “angara”, or “verkhovik”. The very strong Sarma wind blowing in autumn and winter in the middle part of the lake is especially famous. During the "sarma", a storm occurs on Lake Baikal, sometimes lasting for several days. On frosty days, wind-blown clouds of spray freeze in the air, and ships are often covered with a thick layer of ice. Sometimes, as a result of a storm caused by the "sarma", fishermen's boats perish on Lake Baikal.

In Siberia, the average annual temperatures are almost everywhere below 0 °. In some northern regions, they drop even below –15–18 ° (Novosibirsk Islands - 19 °, Sagastyr –17 °, Verkhoyansk –16 °). Only in the most southern parts West Siberian lowland, already within the northern regions of the Kazakh SSR, the average temperature of the year rises to 2-3 ° C.

The severity of the Siberian climate is primarily determined by the very low temperatures of winter and its long duration. Nowhere on the globe winters are never so cold, and only a few areas in central Antarctica or on the Greenland ice sheet can rival Siberia for the harshness of their winters. However, even there has not yet been observed such cold weather as occurs in January in Oymyakon or Verkhoyansk.

Even in the relatively “warm” winter southern and western regions of the West Siberian Lowland, the average January temperature does not exceed - 16–20 °. In Biysk and Barnaul, located almost at the same latitude with the capital of Ukraine, in January it is colder than in Kiev, by 10 °. On some days, temperatures of -45 ° can be everywhere in Siberia; 50-degree frosts were observed even in the south of Western Siberia - in Barnaul, Omsk, Novosibirsk.

Winter is especially cold in Eastern Siberia, over the territory of which, as we already know, an area of ​​high air pressure is located at this time. Throughout the winter, the weather is clear, cloudless and absolutely calm. In such weather conditions there is an extremely intense cooling of the surface, especially at night. Therefore, in winter, in most of the territory of Yakutia, temperatures are kept below -40 ° for a long time and there are no thaws. Particularly severe cold is in closed basins, in the region of Verkhoyansk and Oymyakon. The average temperature in January is lower here - 50 °, and on some days there are frosts even up to 70 °.

Winter in the eastern part of Siberia is on average twenty degrees colder than in the western one. Even the northernmost parts of Western Siberia, located on the coast of the Kara Sea, at this time sometimes turn out to be warmer than some areas of Eastern Siberia, which lie almost 2 thousand km south of them. For example, in Chita, the air temperature in January is much lower than on the banks of the Ob Bay.

Due to the constancy of the weather, the great dryness of the air, the abundance of clear, sometimes even sunny days and the absence of winds, low air temperatures in winter are tolerated by the local population relatively easily. A resident of Krasnoyarsk or Yakutsk considers an invigorating thirty-degree frost to be as common as a frost of 10 ° for a Leningrader. Getting off the train arriving from Moscow or Leningrad, in a large Siberian city you won't even feel right away that the temperature here is 20-25 ° lower. The bright sun, not like winter, floods the snow-covered surroundings with its rays, the air does not move, not a cloud in the sky. From the rooftops, sometimes at the beginning of March, drops begin, and a person who is not accustomed to the peculiarities of the Siberian climate looks with disbelief at the thermometer showing –15, or even –20 °.

Especially often clear and sunny days are observed in winter in Eastern Siberia. The number of sunny days and the duration of the hours of sunshine in many regions of Southern Transbaikalia are much greater than, for example, in Odessa or the Crimea.

As we have already said, summer in Siberia is warm, and in the south, in the steppe zone and in Transbaikalia, it is hot. The average temperature of the warmest month, July, even in the forest zone ranges from 10–12 ° at its extreme northern limit to 18–19 ° in the south. Even more high temperatures observed in steppe regions, where July is warmer than in Ukraine. Only in the north, in the coastal tundra and on the coast of the Arctic Ocean, July and August are cool, for example, in the area of ​​Cape Chelyuskin, the average July temperature is only + 2 °. True, on some, the warmest days, the temperature in the tundra can sometimes rise to 20-25 °. But in general, there are few such days in the north.

In early summer, even in the southernmost regions of Siberia, short-term night frosts are possible. In some areas, crops of grain crops and vegetables are often affected by them. The first autumn frosts usually occur at the end of August. Spring and autumn frosts noticeably shorten the duration of the frost-free period. In the north, this period is everywhere shorter than two months, in the taiga zone it lasts from 60 to 120–130 days, and only in the steppes from late May to mid-September frosts are usually not observed or are extremely rare.

Most of the precipitation that falls in Siberia in the form of rain and snow is brought air masses coming here from the west and northwest. Wet eastern winds from the seas of the Pacific Ocean, fenced off from the territory of Eastern Siberia by a strip of rather high mountain ranges, occasionally penetrate only into the eastern regions of Transbaikalia. Unlike the rest of Siberia, only here at the end of summer heavy rains fall, brought from the east by monsoon winds.

The amount of precipitation falling in Siberia generally decreases markedly towards the east. Even in the most rainfall-rich forest regions of Western Siberia, there are somewhat fewer of them than in the middle zone of the European part of the Soviet Union. Even less precipitation falls in Eastern Siberia, where in the taiga zone the population of some regions is forced to resort to artificial irrigation of their fields and hayfields (Central Yakutia).

The amount of precipitation also changes significantly in different geographic areas... Relatively few of them are obtained in the northernmost, tundra regions of Siberia. In the tundra of the West Siberian Lowland, no more than 250–300 mm falls annually, and in North-Eastern Siberia - 150–200 mm. Here, on the coast of the Chukchi and East Siberian Seas, as well as on the New Siberian Islands, there are places that receive less than 100 mm of precipitation per year, that is, less than some desert areas Central Asia and Kazakhstan. The forest-tundra regions of Western Siberia and the taiga of the Central Siberian plateau receive slightly more (from 300 to 400 mm) precipitation.

The greatest amount of precipitation in the plains falls on the taiga zone of Western Siberia. Within its limits, precipitation falls everywhere over 400 mm throughout the year, and in some places even more than 500 mm (Tomsk 565, Taiga 535 mm). A lot of precipitation (500-600 mm per year) also falls on the western slopes of the Central Siberian plateau - in the Putorana mountains and on the Yenisei ridge.

In the south, in the forest-steppe and steppe zones, the amount of precipitation decreases again, and in the driest areas in the middle reaches of the Irtysh and southern Transbaikalia, they are already less than 300 mm.

Everywhere in Siberia, precipitation falls mainly in the summer in the form of rains. The warm period of the year in some places accounts for up to 75–80% of the annual precipitation. The maximum amount of precipitation in most of Siberia falls in July and August. Only in the south, in the steppes of the West Siberian Lowland, June is usually the rainiest month.

The predominance of precipitation in the form of summer rains is generally favorable for the development of vegetation and agriculture. In most parts of Siberia, rains deliver moisture to plants just when they need it most. Due to the relatively low evaporation from the soil surface, this moisture is quite enough almost everywhere. However, some southern steppe regions of Siberia, where the maximum precipitation occurs in June and where strong winds in spring noticeably increase evaporation, sometimes suffer from drought. On the contrary, in areas where there is relatively a lot of summer rains, they sometimes make haymaking and harvesting more difficult. Summer precipitation falls mainly in the form of prolonged heavy rains, and only in the most eastern regions there are often heavy rainfalls. The maximum amount of precipitation falling per day usually does not exceed 30-50 mm. However, there are cases when up to 120-130 mm dropped out per day (Kamen-na-Obi, Babushkin). Heavy showers are especially typical for the eastern part of Transbaikalia, where they occur at the end of summer almost every year. These showers often cause significant summer flooding here.

Regarding the precipitation regime in many regions of Siberia, "year after year does not occur." This applies to both the annual amount of precipitation and the precipitation of the warm season. So, for example, in forest-steppe regions annual quantity precipitation can range from 600 mm in an exceptionally rainy year to 175 mm in a dry year with average annual number approx. 275 mm. The difference is also very large between the maximum and minimum precipitation in the summer months.

In winter, due to low air humidity and clear weather, the amount of precipitation is relatively small almost everywhere. In the tundra zone, as well as in Transbaikalia and Yakutia, for the entire cold period of the year, they fall no more than 50 mm; even in the most wet in winter the regions of the middle part of the West Siberian Lowland for the period with negative air temperatures account for only about one-fifth of the annual precipitation, that is, slightly more than 100 mm.

The entire territory of Siberia at the beginning of winter is covered with snow for a long time. First of all, it is installed in the extreme northern regions - on the New Siberian Islands and Severnaya Zemlya. Here the snow that fell at the end of August does not melt anymore. During September, snow cover appears everywhere on the coast of the Arctic Ocean, in the tundra zone, in the highlands in the east and south of Siberia, as well as in the northern and middle parts of the Central Siberian Plateau. At the end of October, snow already covers the whole of Siberia, with the exception of only some areas of Southern Transbaikalia.

The duration of the period with stable snow cover ranges from 300 days on the islands of the seas of the Arctic Ocean to 150–160 days in the south of Siberia. Only in areas with little snow in Transbaikalia and in the southwestern part of the West Siberian Lowland, the time during which the snow cover lies is somewhat shorter. However, even here it is held for more than four to five months.

In the middle and end of April, under the rays of the warming spring sun, all southern regions of Siberia are relatively quickly cleared of snow. In the taiga zone, the snow cover remains at the beginning of May, and in the tundra even in June. The latter, at the end of June and even in July, are freed from the seasonal snow of the coast and the islands of the Arctic Ocean.

Despite the very significant duration of the snow cover and the almost complete absence of thaws in the winter months, the thickness of the snow cover in Siberia is generally relatively small and in most regions ranges from 30 to 70 cm. However, in some places in the taiga zone in the east of the West Siberian Lowland and along the On the slopes of the Central Siberian Plateau, the thickness of the snow cover in March - early April reaches 100 and even 120 cm.

But the snow cover is especially thick in some areas in the mountainous regions of Siberia. Mild, fluffy snow covered in winter by strong mountain winds fills the upper reaches of river gorges, accumulates in crevices mountain peaks and on wooded slopes. Its thickness in such shelters in places reaches several meters. A lot of solar heat is needed in order to melt these many-meter snowwalls, and the high-mountain belt does not always receive the required amount of heat. In cooler summers, along the shaded depressions on the northern slopes and at the bottom of narrow valleys, even at the end of August one can often find significant fields of "flying" snow that did not have time to melt.

Of course, there are places in Siberia where very little snow falls, for example, in the southern foothills of Altai, in the Minusinsk Basin and in southern Transbaikalia. In a number of districts of the Chita region and the Buryat-Mongolian Autonomous Soviet Socialist Republic, the thickness of the snow cover does not exceed 10 cm, and in some areas it is only 2 cm. Here, far from every year, a sled path is established, and you can observe how in forty-degree frosts locals ride carts. It is not surprising that in March, when the sun begins to warm up like spring, you will not find snow anywhere in open places. The thin snow cover disappears here completely without a trace, without forming spring streams. The small thickness of the snow cover in Southern Transbaikalia and its early disappearance in the spring are explained by both an insignificant amount of winter precipitation and frequent strong winds, "Drying up" the snow.

Differences in snow depth have a marked effect on economic activity local population... So, in many areas of the forest belt of Western Siberia in winter, the population is forced to fight with heavy snow drifts on the roads, and in the steppes and forest-steppe, where there is little snow, it is necessary to resort to special measures to keep snow in the fields. Permafrost is common in areas where the thickness of the snow cover is low in winter and the summer is not very hot.

We got acquainted with the most characteristic features of the Siberian climate. There are few places on the globe that can compete with it in terms of such a distinct expression. continental climate... It is quite natural that the conditions of the continental climate give some specific features to the geographical landscapes of Siberia.

They affect primarily the nature of vegetation, soil formation and weathering processes. For example, in a continental climate with its very cold winters, broad-leaved trees are almost completely absent in Siberia, and conifers of the Siberian taiga dominate in the forest zone. On the other hand, a warm and not very humid summer is the reason for more significant than anywhere in the world, the movement of forests to the north, and in the mountains - high up. Forests on Taimyr, for example, cover almost up to 72 ° 30 "N. (On the Commander Islands, lying almost 2 thousand km to the south (54 ° N), there are no forests at all. Even on the mainland in the northern part Of the Far East the southern border of the tundra zone lies at about 60 ° N. sh.), and in Altai their upper border sometimes rises to 2300-2400 m.

The relatively warm summer is also one of the reasons for the more northerly position of the border of agriculture - in Siberia, vegetables are sometimes grown north of the 72nd parallel, and cereals - at the latitude of the Arctic Circle. The features of the continental climate are associated with the distribution within the taiga, often near the Arctic Circle, of significant islands of steppe vegetation on chernozem soils and even halophytes on salt marshes (Central Yakut lowland), and typical steppe grasses are found even in the mountains near Verkhoyansk.

Spring in areas with the most continental climate is passing rapidly. Sometimes its duration does not exceed three to four weeks. Under the warm rays of the sun, the snow cover is melting together, and the vegetation develops with cinematic speed. That is why, for example, many vegetables and even watermelons ripen in the vicinity of Yakutsk during a short but hot summer; the barley sown in May is harvested in mid-July, before the onset of frost. This time coincides with the harvesting of barley in the Kuban and northern regions of Central Asia.

The sharp temperature fluctuations characteristic of the Siberian climate are associated with the intense destruction of rocks, which occurs under the influence of physical weathering processes. Typical for areas with maritime climate the processes of chemical weathering are relatively poorly developed here.

The peculiarities of the continental climate also explain the very wide distribution of permafrost in Siberia. This very peculiar phenomenon was noticed in Siberia already by its first explorers - explorers. Taking out the soil during the construction of "forts" or digging a well, they in many places at a shallow depth, even on hot summer days, encountered solid frozen soil. This was so unusual even for the inhabitants of the northern regions of European Russia that the Yakut governors considered it necessary to specially "write off" this to the tsar himself. "And in the Yakutsk land, sir," they wrote, "according to the attitude of commercial and industrial service people, grain arable land is not to be desired - the land, sir, does not grow at all in the middle of summer."

Soviet scientists have studied this phenomenon in detail and in detail, which has received the name of perennial, or permafrost, permafrost. They established the boundaries of its distribution, showing on special maps areas where, at a more or less significant depth, there is a layer of soil or rock, in which negative temperatures persist continuously for many years.

It turned out that especially large areas are occupied by permafrost in the northern and eastern regions Siberia. The southern border of the distribution of permafrost in the west of Siberia begins south of the mouth of the Ob, goes from here to the east to the upper reaches of the river. Taz, then goes to the Yenisei approximately at the mouth of the Podkamennaya Tunguska, and then sharply turns southeast to the northern end of Lake Baikal. The northern regions of Transbaikalia and the entire territory of the Yakut ASSR also lie in the permafrost zone. Permafrost occurs sometimes and much to the south of this border, but already in the form of separate, sometimes, however, very large in area "islands" of permafrost soils among the areas where permafrost is absent in summer. The area of ​​distribution of this "island permafrost" includes the northern part of the taiga zone of Western Siberia, the southwest of Trans-Yenisei Siberia, the southern and southeastern regions of Transbaikalia.

A layer of permafrost soil is usually found at a certain depth, since even in the northernmost and coldest regions of Siberia in summer, the upper horizons of the soil thaw out and have positive temperature... This soil horizon thaws in warm weather is called the active layer. In various regions of Siberia, its thickness ranges from 10–20 cm (in the Far North and the islands of the Arctic Ocean) to several meters (near the southern limit of the permafrost). The thickness of the active layer is of great importance for the life of plants and animals, as well as for the formation of soil. Only in thawed ground do plant roots develop (In recent years, it has been proven that the roots of many plants also penetrate into frozen soil layers. (VP Dadykin. Features of the behavior of plants on cold soils, Moscow 1952), animals dig their holes, processes decay of organic matter.

The thickness of the permafrost layer is quite significant in some places. Its maximum thickness reaches several hundred meters (Nordvik 600 m, Ust-Port 325 m). But to the south, of course, it decreases. Already close southern border the spread of continuous permafrost, its thickness is 35-60 m, and on the "islands" of frozen soils found in the south of the Krasnoyarsk Territory, Irkutsk Region and the Buryat-Mongolian Autonomous Soviet Socialist Republic, it does not exceed 5-10 m.

Permafrost common in areas with a particularly harsh climate, with average annual temperature below –2 °. Its existence is possible only in places that are distinguished by very long and extremely cold winters, as well as short, usually not very warm summer, during which the soil already at a certain depth does not have time to thaw. Permafrost is especially widespread in those regions of Siberia where little snow falls in winter and its cover does not reach significant thickness, for example, in the southern regions of Transbaikalia.

However, it is not always possible to explain the reasons for the emergence and very high thickness of permafrost only by the conditions of the modern climate. Seasonal freezing does not extend to a depth of several hundred meters; it is difficult to explain only by this the finds in the frozen strata of well-preserved corpses of long-extinct animals (mammoth, rhinoceros). Moreover, in a number of regions of Siberia, even melting and retreating (degradation) of permafrost is currently observed. Therefore, there is reason to consider permafrost an ancient formation associated with the conditions of an even more severe climate, which was here during the periods of glaciation or in the late glacial time (Recently, in many regions of Siberia, facts have been established that speak of the possibility of not only preserving, Thus, in the lower reaches of the Yenisei, permafrost was found in young (post-glacial) river sediments, in the Tunkinskaya depression (Buryat-Mongolian ASSR), it was formed after the appearance of a man here, and in Eastern Yakutia, dumps of rock worked out by prospectors turn out to be firmly bound by permafrost).

Permafrost in the areas of its distribution has a great impact on all elements of geographic landscapes. It is possible to point out, for example, the specific character of the coast of the New Siberian Islands, composed of layers of fossil ice several tens of meters thick, the sinkhole (so-called "thermokarst") hollows of the lakes, widespread in the tundra zone and the Vilyui depression, and the hillocks characteristic of the northern part of Siberia with an ice core ("bulgunnyakhi"), etc.

Permafrost also largely determines the features of the regime of surface and groundwater... By preventing the penetration of water into the ground, it is the reason for the large swampiness of many flat areas of Siberia. In the spring, melt water quickly rolls down the frozen ground into the valleys and causes a high rise in the level in the rivers; in summer, water formed due to the slow thawing of the upper horizons of frozen soil serves as a source of water supply for watercourses. But in winter, when frosts freeze the moisture of the active layer, the flow of water almost stops and many small rivers freeze to the bottom. Permafrost is associated with the formation of river and ground ice, as well as the phenomena of swelling and cracking of the soil, etc.

Where the thickness of the soil thaws in summer is low, it is characterized by low temperature and high humidity, which slows down the processes of soil formation, since the decomposition of plant residues occurs extremely slowly under these conditions. Therefore, soils in permafrost areas are usually thin, contain a lot of undecomposed plant remains and are highly moistened. The hard surface of the upper permafrost horizon and low temperatures even in thawed ground limit the ability of plant roots to penetrate deep into the soil. Therefore, the roots here are most often forced to spread horizontally, and during strong winds the trees are often uprooted. This explains the large number of felled trunks that form "windfalls" known to every Siberian in the East Siberian taiga.