West Siberian Plain: location and extent. Features of the relief of Western Siberia

The West Siberian Plain is one of the largest accumulative low-lying plains in the world. It stretches from the shores of the Kara Sea to the steppes of Kazakhstan and from the Urals in the west to the Central Siberian Plateau in the east. The plain has the shape of a trapezoid tapering to the north: the distance from its southern border to the northern reaches almost 2500 km, width - from 800 to 1900 km, and the area is only slightly less than 3 million sq. km 2 .

There are no other such vast plains in the Soviet Union, with such a poorly broken relief and such small fluctuations in relative heights. The comparative uniformity of the relief determines the distinct zonality of the landscapes of Western Siberia - from tundra in the north to steppe in the south. Due to the poor drainage of the territory within its boundaries, hydromorphic complexes play a very prominent role: swamps and swampy forests occupy here a total of about 128 million hectares. ha, and in the steppe and forest-steppe zones there are many solonetzes, solods and solonchaks.

The geographical position of the West Siberian Plain determines the transitional nature of its climate between the temperate continental climate of the Russian Plain and the sharply continental climate of Central Siberia. Therefore, the landscapes of the country are distinguished by a number of peculiar features: the natural zones here are somewhat shifted to the north compared to the Russian Plain, there is no zone of broad-leaved forests, and landscape differences within the zones are less noticeable than on the Russian Plain.

The West Siberian Plain is the most inhabited and developed (especially in the south) part of Siberia. Within its boundaries are the Tyumen, Kurgan, Omsk, Novosibirsk, Tomsk and North Kazakhstan regions, a significant part of the Altai Territory, Kustanai, Kokchetav and Pavlodar regions, as well as some eastern regions of the Sverdlovsk and Chelyabinsk regions and the western regions of the Krasnoyarsk Territory.

The acquaintance of Russians with Western Siberia took place for the first time, probably, as early as the 11th century, when the Novgorodians visited the lower reaches of the Ob. Ermak's campaign (1581-1584) opens a brilliant period of the Great Russian geographical discoveries in Siberia and the development of its territory.

However, the scientific study of the nature of the country began only in the 18th century, when detachments of the Great Northern expedition and then academic expeditions were sent here. In the 19th century Russian scientists and engineers are studying the conditions of navigation on the Ob, Yenisei and the Kara Sea, the geological and geographical features of the route of the Siberian railway that was being designed at that time, salt deposits in the steppe zone. A significant contribution to the knowledge of the West Siberian taiga and steppes was made by studies of soil-botanical expeditions of the Migration Administration, undertaken in 1908-1914. in order to study the conditions for the agricultural development of plots allocated for the resettlement of peasants from European Russia.

The study of the nature and natural resources of Western Siberia acquired a completely different scope after the Great October Revolution. In the research that was necessary for the development of the productive forces, no longer individual specialists or small detachments took part, but hundreds of large complex expeditions and many scientific institutes created in various cities of Western Siberia. Detailed and versatile studies were carried out here by the USSR Academy of Sciences (Kulunda, Baraba, Gydan and other expeditions) and its Siberian branch, the West Siberian Geological Administration, geological institutes, expeditions of the Ministry of Agriculture, Hydroproject and other organizations.

As a result of these studies, ideas about the country's relief have changed significantly, detailed soil maps of many regions of Western Siberia have been compiled, and measures have been developed for the rational use of saline soils and the famous West Siberian chernozems. Forest typological studies of Siberian geobotanists and the study of peat bogs and tundra pastures were of great practical importance. But especially significant results were brought by the work of geologists. Deep drilling and special geophysical studies have shown that the bowels of many regions of Western Siberia contain the richest deposits of natural gas, large reserves of iron ore, brown coal and many other minerals, which already serve as a solid base for the development of industry in Western Siberia.

Geological structure and history of the development of the territory

Taz Peninsula and the Middle Ob in the section Nature of the world.

Many features of the nature of Western Siberia are due to the nature of its geological structure and history of development. The entire territory of the country is located within the West Siberian epihercynian plate, the foundation of which is composed of dislocated and metamorphosed Paleozoic deposits, similar in nature to those of the Urals, and in the south of the Kazakh hillock. The formation of the main folded structures of the basement of Western Siberia, which have a predominantly meridional direction, refers to the era of the Hercynian orogeny.

The tectonic structure of the West Siberian plate is rather heterogeneous. However, even its large structural elements appear in the modern relief less distinctly than the tectonic structures of the Russian Platform. This is explained by the fact that the topography of the surface of the Paleozoic rocks, subsided to a great depth, is leveled here by the cover of the Meso-Cenozoic deposits, the thickness of which exceeds 1000 m, and in separate depressions and syneclises of the Paleozoic basement - 3000-6000 m.

The Mesozoic formations of Western Siberia are represented by marine and continental sandy-argillaceous deposits. Their total capacity in some areas reaches 2500-4000 m. The alternation of marine and continental facies indicates the tectonic mobility of the territory and repeated changes in the conditions and regime of sedimentation on the West Siberian Plate that sank at the beginning of the Mesozoic.

Paleogene deposits are predominantly marine and consist of gray clays, mudstones, glauconite sandstones, opokas, and diatomites. They accumulated at the bottom of the Paleogene Sea, which, through the depression of the Turgai Strait, connected the Arctic basin with the seas that were then located on the territory of Central Asia. This sea left Western Siberia in the middle of the Oligocene, and therefore the Upper Paleogene deposits are already represented here by sandy-clayey continental facies.

Significant changes in the conditions of accumulation of sedimentary deposits occurred in the Neogene. The suites of Neogene rocks, which come to the surface mainly in the southern half of the plain, consist exclusively of continental lacustrine-river deposits. They formed in the conditions of a poorly dissected plain, first covered with rich subtropical vegetation, and later with broad-leaved deciduous forests from representatives of the Turgai flora (beech, walnut, hornbeam, lapina, etc.). In some places there were areas of savannas, where giraffes, mastodons, hipparions, and camels lived at that time.

The events of the Quaternary period had a particularly great influence on the formation of the landscapes of Western Siberia. During this time, the territory of the country experienced repeated subsidence and was still an area of predominantly accumulation of loose alluvial, lacustrine, and in the north - marine and glacial deposits. The thickness of the Quaternary cover in the northern and central regions reaches 200-250 m. However, in the south it noticeably decreases (in some places up to 5-10 m), and in the modern relief, the effects of differentiated neotectonic movements are clearly expressed, as a result of which swell-like uplifts arose, often coinciding with the positive structures of the Mesozoic cover of sedimentary deposits.

Lower Quaternary deposits are represented in the north of the plain by alluvial sands filling buried valleys. The sole of alluvium is located in them sometimes at 200-210 m below the current level of the Kara Sea. Above them in the north, pre-glacial clays and loams with fossil remains of the tundra flora usually occur, which indicates a noticeable cooling of Western Siberia that had already begun at that time. However, dark coniferous forests with an admixture of birch and alder prevailed in the southern regions of the country.

The Middle Quaternary time in the northern half of the plain was an epoch of marine transgressions and repeated glaciations. The most significant of them was Samarovskoye, the deposits of which compose the interfluves of the territory lying between 58-60 ° and 63-64 ° N. sh. According to currently prevailing views, the cover of the Samara glacier, even in the extreme northern regions of the lowland, was not continuous. The composition of boulders shows that its sources of food were glaciers descending from the Urals to the Ob valley, and in the east - glaciers of the Taimyr mountain ranges and the Central Siberian Plateau. However, even during the period of maximum development of glaciation in the West Siberian Plain, the Ural and Siberian ice sheets did not merge with one another, and the rivers of the southern regions, although they encountered a barrier formed by ice, found their way north in the gap between them.

Along with typical glacial rocks, the composition of the sediments of the Samarovo stratum also includes marine and glacial-marine clays and loams formed at the bottom of the sea advancing from the north. Therefore, the typical moraine relief forms are less distinct here than on the Russian Plain. On the lacustrine and fluvioglacial plains adjacent to the southern edge of the glaciers, then forest-tundra landscapes prevailed, and in the extreme south of the country loess-like loams were formed, in which pollen of steppe plants (wormwood, kermek) is found. Marine transgression continued in the post-Samarovo time, the deposits of which are represented in the north of Western Siberia by Messov sands and clays of the Sanchugov Formation. In the northeastern part of the plain, moraines and glacial-marine loams of the younger Taz glaciation are common. The interglacial epoch, which began after the retreat of the ice sheet, was marked in the north by the spread of the Kazantsevo marine transgression, whose deposits in the lower reaches of the Yenisei and Ob contain the remains of a more heat-loving marine fauna than currently living in the Kara Sea.

The last, Zyryansk, glaciation was preceded by a regression of the boreal sea, caused by uplifts in the northern regions of the West Siberian Plain, the Urals, and the Central Siberian Plateau; the amplitude of these uplifts was only a few tens of meters. During the maximum stage of development of the Zyryansk glaciation, glaciers descended into the regions of the Yenisei Plain and the eastern foot of the Urals to approximately 66 ° N. sh., where a number of stadial terminal moraines were left. In the south of Western Siberia, sandy-argillaceous Quaternary sediments were being blown over at that time, eolian landforms were forming, and loess-like loams were accumulating.

Some researchers of the northern regions of the country draw a more complex picture of the events of the Quaternary glaciation in Western Siberia. Thus, according to the geologist V.N. Saks and geomorphologist G.I. Lazukov, glaciation began here as early as the Lower Quaternary and consisted of four independent epochs: Yarskaya, Samarovo, Taz and Zyryanskaya. Geologists S. A. Yakovlev and V. A. Zubakov even count six glaciations, referring the beginning of the most ancient of them to the Pliocene.

On the other hand, there are supporters of a one-time glaciation of Western Siberia. Geographer A. I. Popov, for example, considers the deposits of the glaciation era of the northern half of the country as a single water-glacial complex consisting of marine and glacial-marine clays, loams and sands containing inclusions of boulder material. In his opinion, there were no extensive ice sheets on the territory of Western Siberia, since typical moraines are found only in the extreme western (at the foot of the Urals) and eastern (near the ledge of the Central Siberian Plateau) regions. The middle part of the northern half of the plain during the epoch of glaciation was covered by the waters of marine transgression; the boulders enclosed in its deposits are brought here by icebergs that have come off the edge of the glaciers that descended from the Central Siberian Plateau. Only one Quaternary glaciation of Western Siberia is recognized by the geologist V. I. Gromov.

At the end of the Zyryansk glaciation, the northern coastal regions of the West Siberian Plain again sank. The subsided areas were flooded by the waters of the Kara Sea and covered with marine sediments that make up post-glacial marine terraces, the highest of which rises 50-60 m above the modern level of the Kara Sea. Then, after the regression of the sea, a new incision of rivers began in the southern half of the plain. Due to the small slopes of the channel in most of the river valleys of Western Siberia, lateral erosion prevailed, the deepening of the valleys proceeded slowly, therefore they usually have a considerable width, but a small depth. In poorly drained interfluve spaces, the reworking of the ice age relief continued: in the north, it consisted in leveling the surface under the influence of solifluction processes; in the southern, non-glacial provinces, where more atmospheric precipitation fell, the processes of deluvial washout played a particularly prominent role in the transformation of the relief.

Paleobotanical materials suggest that after the glaciation there was a period with a slightly drier and warmer climate than now. This is confirmed, in particular, by the finds of stumps and tree trunks in the deposits of the tundra regions of Yamal and the Gydan Peninsula at 300-400 km to the north of the modern border of woody vegetation and the wide development of the tundra zone of relict large-hilly peatlands in the south.

Currently, in the territory of the West Siberian Plain, there is a slow shift of the boundaries of geographical zones to the south. Forests in many places advance on the forest-steppe, forest-steppe elements penetrate into the steppe zone, and the tundra is slowly replacing woody vegetation near the northern limit of sparse forests. True, in the south of the country, man intervenes in the natural course of this process: cutting down forests, he not only stops their natural advance on the steppe, but also contributes to the displacement of the southern border of forests to the north.

Relief

See photos of the nature of the West Siberian Plain: the Taz Peninsula and the Middle Ob in the Nature of the World section.

Scheme of the main orographic elements of the West Siberian Plain

Differentiated subsidence of the West Siberian Plate in the Mesozoic and Cenozoic determined the predominance of accumulation processes of loose deposits within it, the thick cover of which levels the unevenness of the surface of the Hercynian basement. Therefore, the modern West Siberian Plain is characterized by a generally flat surface. However, it cannot be considered as a monotonous lowland, as it was considered until recently. In general, the territory of Western Siberia has a concave shape. Its lowest parts (50-100 m) are located mainly in the central ( Kondinskaya and Sredneobskaya lowlands) and northern ( Nizhneobskaya, Nadymskaya and Purskaya lowlands) parts of the country. Along the western, southern and eastern outskirts stretch low (up to 200-250 m) hills: Severo-Sosvinskaya, Turin, Ishimskaya, Priobskoe and Chulym-Yenisei plateau, Ketsko-Tymskaya, Verkhnetazovskaya, Lower Yenisei. A distinct strip of hills form in the inner part of the plain Siberian Ridges(average height - 140-150 m), stretching from the west from the Ob to the east to the Yenisei, and parallel to them Vasyuganskaya plain.

Some orographic elements of the West Siberian Plain correspond to geological structures: gently sloping anticlinal uplifts correspond, for example, to the Verkhnetazovsky and lulimvor, a Barabinskaya and Kondinskaya the lowlands are confined to the syneclises of the slab basement. However, discordant (inversion) morphostructures are also not uncommon in Western Siberia. These include, for example, the Vasyugan Plain, which formed on the site of a gently sloping syneclise, and the Chulym-Yenisei Plateau, located in the basement trough zone.

The West Siberian Plain is usually divided into four large geomorphological regions: 1) marine accumulative plains in the north; 2) glacial and water-glacial plains; 3) near-glacial, mainly lacustrine-alluvial, plains; 4) southern non-glacial plains (Voskresensky, 1962).

Differences in the relief of these areas are explained by the history of their formation in the Quaternary, the nature and intensity of the latest tectonic movements, and zonal differences in modern exogenous processes. In the tundra zone, relief forms are especially widely represented, the formation of which is associated with a harsh climate and the widespread distribution of permafrost. Thermokarst basins, bulgunnyakhs, spotted and polygonal tundras are quite common, and solifluction processes are developed. The southern steppe provinces are characterized by numerous closed basins of suffusion origin, occupied by salt marshes and lakes; the network of river valleys here is not dense, and erosional landforms in the interfluves are rare.

The main elements of the relief of the West Siberian Plain are wide flat interfluves and river valleys. Due to the fact that the interfluve spaces account for a large part of the country's area, they determine the general appearance of the relief of the plain. In many places, the slopes of their surface are insignificant, the runoff of precipitation, especially in the forest-bog zone, is very difficult, and the interfluves are heavily swamped. Large areas are occupied by swamps to the north of the line of the Siberian railway, on the interfluve of the Ob and Irtysh, in the Vasyugan region and the Baraba forest-steppe. However, in some places the relief of the interfluves takes on the character of a wavy or hilly plain. Such areas are especially typical of certain northern provinces of the plain, which were subjected to Quaternary glaciations, which left here a heap of stadial and bottom moraines. In the south - in Baraba, on the Ishim and Kulunda plains - the surface is often complicated by numerous low ridges stretching from the northeast to the southwest.

Another important element of the country's relief is the river valleys. All of them were formed in conditions of small slopes of the surface, slow and calm flow of rivers. Due to differences in the intensity and nature of erosion, the appearance of the river valleys of Western Siberia is very diverse. There are also well-developed deep (up to 50-80 m) valleys of large rivers - the Ob, Irtysh and Yenisei - with a steep right bank and a system of low terraces on the left bank. In places, their width is several tens of kilometers, and the Ob valley in the lower reaches even 100-120 km. The valleys of most small rivers are often only deep ditches with poorly defined slopes; during spring floods, water completely fills them and floods even neighboring valley areas.

Climate

See photos of the nature of the West Siberian Plain: the Taz Peninsula and the Middle Ob in the Nature of the World section.

Western Siberia is a country with a fairly severe continental climate. Its large length from north to south determines the distinct zonality of the climate and significant differences in the climatic conditions of the northern and southern parts of Western Siberia, associated with a change in the amount of solar radiation and the nature of the circulation of air masses, especially western transport flows. The southern provinces of the country, located inland, at a great distance from the oceans, are also characterized by a more continental climate.

During the cold period, two baric systems interact within the country: an area of relatively high atmospheric pressure located above the southern part of the plain, an area of low pressure, which in the first half of winter stretches in the form of a hollow of the Icelandic baric minimum over the Kara Sea and northern peninsulas. In winter, masses of continental air of temperate latitudes predominate, which come from Eastern Siberia or are formed on the spot as a result of air cooling over the territory of the plain.

Cyclones often pass in the border zone of areas of high and low pressure. Especially often they are repeated in the first half of winter. Therefore, the weather in the maritime provinces is very unstable; on the coast of Yamal and the Gydan Peninsula, strong winds are guaranteed, the speed of which reaches 35-40 m/s. The temperature here is even somewhat higher than in the neighboring forest-tundra provinces located between 66 and 69°N. sh. Further south, however, winter temperatures gradually rise again. In general, winter is characterized by stable low temperatures, there are few thaws here. The minimum temperatures throughout Western Siberia are almost the same. Even near the southern border of the country, in Barnaul, there are frosts down to -50 -52 °, i.e., almost the same as in the far north, although the distance between these points is more than 2000 km. Spring is short, dry and comparatively cold; April, even in the forest-marsh zone, is not yet quite a spring month.

In the warm season, low pressure sets in over the country, and an area of higher pressure forms over the Arctic Ocean. In connection with this summer, weak northerly or northeasterly winds predominate, and the role of western air transport noticeably increases. In May, there is a rapid increase in temperatures, but often, with the intrusions of arctic air masses, there are returns of cold weather and frosts. The warmest month is July, the average temperature of which is from 3.6° on Bely Island to 21-22° in the Pavlodar region. The absolute maximum temperature is from 21° in the north (Bely Island) to 40° in the extreme southern regions (Rubtsovsk). High summer temperatures in the southern half of Western Siberia are explained by the inflow of heated continental air here from the south - from Kazakhstan and Central Asia. Autumn comes late. Even in September, the weather is warm during the day, but November, even in the south, is already a real winter month with frosts up to -20 -35 °.

Most of the precipitation falls in the summer and is brought by air masses coming from the west, from the Atlantic. From May to October, Western Siberia receives up to 70-80% of the annual precipitation. There are especially many of them in July and August, which is explained by intensive activity on the Arctic and polar fronts. The amount of winter precipitation is relatively low and ranges from 5 to 20-30 mm/month. In the south, in some winter months, snow sometimes does not fall at all. Significant fluctuations in the amount of precipitation in different years are characteristic. Even in the taiga, where these changes are less than in other zones, precipitation, for example, in Tomsk, falls from 339 mm in a dry year up to 769 mm into wet. Especially large differences are observed in the forest-steppe zone, where, with an average long-term precipitation of about 300-350 mm/year in wet years falls up to 550-600 mm/year, and in dry - only 170-180 mm/year.

There are also significant zonal differences in evaporation values, which depend on the amount of precipitation, air temperature, and the evaporative properties of the underlying surface. Moisture evaporates most of all in the rainy-rich southern half of the forest-bog zone (350-400 mm/year). In the north, in the coastal tundra, where the air humidity is relatively high in summer, the amount of evaporation does not exceed 150-200 mm/year. It is approximately the same in the south of the steppe zone (200-250 mm), which is already explained by the low amount of precipitation falling in the steppes. However, evaporation here reaches 650-700 mm, therefore, in some months (especially in May), the amount of evaporating moisture can exceed the amount of precipitation by 2-3 times. In this case, the lack of atmospheric precipitation is compensated by the reserves of moisture in the soil accumulated due to autumn rains and melting snow cover.

The extreme southern regions of Western Siberia are characterized by droughts, which occur mainly in May and June. They are observed on average every three to four years during periods with anticyclonic circulation and increased frequency of arctic air intrusions. The dry air coming from the Arctic, when passing over Western Siberia, is warmed up and enriched with moisture, but its heating is more intense, so the air is more and more removed from the state of saturation. In this regard, evaporation increases, which leads to drought. In some cases, the cause of droughts is also the inflow of dry and warm air masses from the south - from Kazakhstan and Central Asia.

In winter, the territory of Western Siberia is covered with snow for a long time, the duration of which in the northern regions reaches 240-270 days, and in the south - 160-170 days. Due to the fact that the period of precipitation in solid form lasts more than half a year, and thaws begin no earlier than March, the thickness of the snow cover in the tundra and steppe zones in February is 20-40 cm, in the swampy zone - from 50-60 cm in the west up to 70-100 cm in the eastern Yenisei regions. In treeless - tundra and steppe - provinces, where strong winds and blizzards occur in winter, snow is distributed very unevenly, as the winds blow it from elevated relief elements into depressions, where powerful snowdrifts form.

The harsh climate of the northern regions of Western Siberia, where the heat entering the soil is not enough to maintain a positive temperature of the rocks, contributes to the freezing of soils and the widespread permafrost. On the Yamal, Tazovsky and Gydansky peninsulas, permafrost is found everywhere. In these areas of its continuous (confluent) distribution, the thickness of the frozen layer is very significant (up to 300-600 m), and its temperatures are low (on the watershed spaces - 4, -9 °, in the valleys -2, -8 °). Further south, within the limits of the northern taiga up to a latitude of about 64°, permafrost occurs already in the form of isolated islands interspersed with taliks. Its power decreases, temperatures rise to? 0.5 -1 °, and the depth of summer thawing also increases, especially in areas composed of mineral rocks.

Water

See photos of the nature of the West Siberian Plain: the Taz Peninsula and the Middle Ob in the Nature of the World section.

Western Siberia is rich in underground and surface waters; in the north, its coast is washed by the waters of the Kara Sea.

The entire territory of the country is located within the large West Siberian artesian basin, in which hydrogeologists distinguish several basins of the second order: Tobolsk, Irtysh, Kulunda-Barnaul, Chulym, Ob, etc. Due to the large thickness of the cover of loose deposits, consisting of alternating permeable ( sands, sandstones) and water-resistant rocks, artesian basins are characterized by a significant number of aquifers associated with formations of various ages - Jurassic, Cretaceous, Paleogene and Quaternary. The groundwater quality of these horizons is very different. In most cases, artesian waters of deep horizons are more mineralized than those lying closer to the surface.

In some aquifers of the Ob and Irtysh artesian basins at a depth of 1000-3000 m there are hot salty waters, most often of chloride calcium-sodium composition. Their temperature is from 40 to 120°C, the daily flow rate of wells reaches 1-1.5 thousand tons per day. m 3, and total stocks - 65,000 km 3; such pressure water can be used for heating cities, greenhouses and greenhouses.

Groundwater in arid steppe and forest-steppe regions of Western Siberia is of great importance for water supply. In many areas of the Kulunda steppe, deep tubular wells were built to extract them. Quaternary groundwater is also used; however, in the southern regions, due to climatic conditions, poor drainage of the surface and slow circulation, they are often highly saline.

The surface of the West Siberian Plain is drained by many thousands of rivers, the total length of which exceeds 250 thousand km. km. These rivers carry out into the Kara Sea annually about 1200 km 3 water - 5 times more than the Volga. The density of the river network is not very high and varies in different places depending on the relief and climatic features: in the Tavda basin it reaches 350 km, and in the Baraba forest-steppe - only 29 km per 1000 km 2. Some southern regions of the country with a total area of more than 445,000 sq. km 2 belong to the territories of closed flow and are distinguished by an abundance of endorheic lakes.

The main sources of food for most rivers are melted snow water and summer-autumn rains. In accordance with the nature of food sources, the runoff is seasonally uneven: approximately 70-80% of its annual amount occurs in spring and summer. Especially a lot of water flows down during the spring flood, when the level of large rivers rises by 7-12 m(in the lower reaches of the Yenisei even up to 15-18 m). For a long time (in the south - five, and in the north - eight months) the West Siberian rivers are ice-bound. Therefore, the winter months account for no more than 10% of the annual runoff.

The rivers of Western Siberia, including the largest ones - the Ob, Irtysh and Yenisei, are characterized by slight slopes and low flow rates. So, for example, the fall of the Ob channel in the section from Novosibirsk to the mouth over 3000 km equals only 90 m, and its flow rate does not exceed 0.5 m/s.

The most important water artery of Western Siberia is the river Ob with its large left tributary the Irtysh. The Ob is one of the greatest rivers in the world. The area of its basin is almost 3 million hectares. km 2 and the length is 3676 km. The Ob basin is located within several geographical zones; in each of them, the nature and density of the river network are different. So, in the south, in the forest-steppe zone, the Ob receives relatively few tributaries, but in the taiga zone their number noticeably increases.

Below the confluence of the Irtysh, the Ob turns into a powerful stream up to 3-4 km. Near the mouth, the width of the river in places reaches 10 km, and depth - up to 40 m. This is one of the most abundant rivers in Siberia; it brings an average of 414 km 3 water.

The Ob is a typical flat river. The slopes of its channel are small: the fall in the upper part is usually 8-10 cm, and below the mouth of the Irtysh does not exceed 2-3 cm for 1 km currents. During spring and summer, the runoff of the Ob near Novosibirsk is 78% per annum; Near the mouth (near Salekhard), the seasonal distribution of runoff is as follows: winter - 8.4%, spring - 14.6, summer - 56 and autumn - 21%.

Six rivers of the Ob basin (Irtysh, Chulym, Ishim, Tobol, Ket and Konda) have a length of more than 1000 km; the length of even some second-order tributaries sometimes exceeds 500 km.

The largest of the tributaries - Irtysh, whose length is 4248 km. Its origins lie outside the Soviet Union, in the mountains of the Mongolian Altai. For a significant part of its turning, the Irtysh crosses the steppes of Northern Kazakhstan and has almost no tributaries right up to Omsk. Only in the lower reaches, already within the taiga, several large rivers flow into it: Ishim, Tobol, etc. The entire length of the Irtysh is navigable, but in the upper reaches in summer, during a period of low water level, navigation is difficult due to numerous riffles.

Along the eastern border of the West Siberian Plain flows Yenisei- the most abundant river in the Soviet Union. Her length is 4091 km(if we consider the Selenga River as the source, then 5940 km); the basin area is almost 2.6 million sq. km 2. Like the Ob, the Yenisei basin is elongated in the meridional direction. All its major right tributaries flow through the territory of the Central Siberian Plateau. From the flat swampy watersheds of the West Siberian Plain, only the shorter and less watery left tributaries of the Yenisei begin.

The Yenisei originates in the mountains of the Tuva ASSR. In the upper and middle reaches, where the river crosses the spurs of the Sayan Mountains and the Central Siberian Plateau, composed of bedrock, rapids (Kazachinsky, Osinovsky, etc.) occur in its channel. After the confluence of the Lower Tunguska, the current becomes calmer and slower, and sandy islands appear in the channel, breaking the river into channels. The Yenisei flows into the wide Yenisei Bay of the Kara Sea; its width near the mouth, located near the Brekhov Islands, reaches 20 km.

The Yenisei is characterized by large fluctuations in expenditure by season. Its minimum winter consumption near the mouth is about 2500 m 3 /sec, the maximum during the flood period exceeds 132 thousand km. m 3 /sec with an annual average of about 19,800 m 3 /sec. During the year, the river brings to its mouth more than 623 km 3 water. In the lower reaches, the depth of the Yenisei is very significant (in places 50 m). This makes it possible for sea vessels to rise up the river by more than 700 km and reach Igarka.

There are about one million lakes on the West Siberian Plain, the total area of which is more than 100 thousand hectares. km 2. According to the origin of the basins, they are divided into several groups: occupying the primary irregularities of the flat relief; thermokarst; moraine-glacial; lakes of river valleys, which in turn are divided into floodplain and oxbow lakes. Peculiar lakes - "fogs" - are found in the Ural part of the plain. They are located in wide valleys, flood in the spring, sharply reducing their size in the summer, and by autumn, many disappear altogether. In the forest-steppe and steppe regions of Western Siberia there are lakes that fill suffusion or tectonic basins.

Soils, vegetation and wildlife

See photos of the nature of the West Siberian Plain: the Taz Peninsula and the Middle Ob in the Nature of the World section.

The plain relief of Western Siberia contributes to a pronounced zonality in the distribution of soils and vegetation. Within the country there are tundra, forest-tundra, forest-bog, forest-steppe and steppe zones gradually replacing one another. Geographical zonality thus resembles, in general terms, the system of zoning of the Russian Plain. However, the zones of the West Siberian Plain also have a number of local specific features that noticeably distinguish them from similar zones in Eastern Europe. Typical zonal landscapes are located here on dissected and better drained upland and riverine areas. In poorly drained interfluve spaces, the runoff from which is difficult, and the soils are usually highly moistened, marsh landscapes prevail in the northern provinces, and landscapes formed under the influence of saline groundwater in the south. Thus, the nature and density of relief dissection play a much greater role here than on the Russian Plain in the distribution of soils and vegetation cover, causing significant differences in the regime of soil moisture.

Therefore, there are, as it were, two independent systems of latitudinal zonality in the country: the zonality of drained areas and the zonality of undrained interfluves. These differences are most clearly manifested in the nature of the soils. So, in the drained areas of the forest-bog zone, mainly strongly podzolized soils under coniferous taiga and soddy-podzolic soils under birch forests are formed, and in neighboring undrained places - powerful podzols, marsh and meadow-bog soils. The drained spaces of the forest-steppe zone are mostly occupied by leached and degraded chernozems or dark gray podzolized soils under birch groves; in undrained areas, they are replaced by marsh, saline or meadow-chernozem soils. In the upland areas of the steppe zone, either ordinary chernozems, which are characterized by increased obesity, low thickness, and linguality (heterogeneity) of soil horizons, or chestnut soils predominate; in poorly drained areas, they usually include spots of solods and solodized solonetzes or solonetsous meadow-steppe soils.

Fragment of a section of swampy taiga in Surgut Polissya (according to V. I. Orlov)

There are some other features that distinguish the zones of Western Siberia from the zones of the Russian Plain. In the tundra zone, which extends much further north than on the Russian Plain, large areas are occupied by arctic tundra, which are absent in the mainland regions of the European part of the Union. The woody vegetation of the forest-tundra is represented mainly by Siberian larch, and not by spruce, as in the regions lying west of the Urals.

In the forest-bog zone, 60% of the area of which is occupied by swamps and poorly drained swampy forests 1, pine forests occupy 24.5% of the forested area, and birch forests (22.6%), mainly secondary ones, predominate. Smaller areas are covered with damp dark coniferous cedar taiga (Pinus sibirica), fir (Abies sibirica) and ate (Picea obovata). Broad-leaved species (with the exception of linden, occasionally found in the southern regions) are absent in the forests of Western Siberia, and therefore there is no zone of broad-leaved forests here.

1 It is for this reason that the zone in Western Siberia is called the forest-bog zone.

An increase in the continentality of the climate causes a relatively sharp transition, compared to the Russian Plain, from forest-bog landscapes to dry steppe spaces in the southern regions of the West Siberian Plain. Therefore, the width of the forest-steppe zone in Western Siberia is much less than on the Russian Plain, and of the tree species it contains mainly birch and aspen.

The West Siberian Plain is wholly part of the transitional Eurosiberian zoogeographic subregion of the Palearctic. 478 species of vertebrates are known here, of which 80 species are mammals. The fauna of the country is young and in its composition differs little from the fauna of the Russian Plain. Only in the eastern half of the country are some eastern, trans-Yenisei forms found: the Dzungarian hamster (Phodopus sungorus), chipmunk (Eutamias sibiricus) and others. In recent years, the fauna of Western Siberia has been enriched by muskrats acclimatized here (Ondatra zibethica), hare-hare (Lepus europaeus), American mink (Lutreola vison), teleutka squirrel (Sciurus vulgaris exalbidus), and carp were introduced into its reservoirs (Cyprinus carpio) and bream (Abramis brama).

Natural resources

See photos of the nature of the West Siberian Plain: the Taz Peninsula and the Middle Ob in the Nature of the World section.

The natural wealth of Western Siberia has long served as the basis for the development of various sectors of the economy. There are tens of millions of hectares of good arable land here. Particularly valuable are the lands of the steppe and forest-steppe zones with their climate favorable for agriculture and highly fertile chernozems, gray forest and non-saline chestnut soils, which occupy more than 10% of the country's area. Due to the flatness of the relief, the development of the lands of the southern part of Western Siberia does not require large capital expenditures. For this reason, they were one of the priority areas for the development of virgin and fallow lands; in recent years, more than 15 million hectares have been involved in crop rotation. ha new lands, the production of grain and industrial crops (sugar beet, sunflower, etc.) increased. The lands located to the north, even in the southern taiga zone, are still underused and are a good reserve for development in the coming years. However, this will require much greater expenditures of labor and funds for draining, uprooting and clearing land from shrubs.

The pastures of the forest-bog, forest-steppe and steppe zones are of high economic value, especially water meadows along the valleys of the Ob, Irtysh, Yenisei and their large tributaries. The abundance of natural meadows here creates a solid base for the further development of animal husbandry and a significant increase in its productivity. Moss pastures of the tundra and forest-tundra, occupying more than 20 million hectares in Western Siberia, are of great importance for the development of reindeer breeding. ha; more than half a million domestic deer graze on them.

A significant part of the plain is occupied by forests - birch, pine, cedar, fir, spruce and larch. The total forested area in Western Siberia exceeds 80 million hectares. ha; timber reserves of about 10 billion m 3, and its annual growth is over 10 million tons. m 3 . The most valuable forest areas are located here, which provide wood for various sectors of the national economy. The forests along the valleys of the Ob, the lower reaches of the Irtysh and some of their navigable or raftable tributaries are currently most widely used. But many forests, including especially valuable massifs of condo pine, located between the Urals and the Ob, are still poorly developed.

Dozens of large rivers of Western Siberia and hundreds of their tributaries serve as important shipping routes connecting the southern regions with the far north. The total length of navigable rivers exceeds 25,000 km. km. Approximately the same is the length of the rivers along which timber is rafted. The full-flowing rivers of the country (Yenisei, Ob, Irtysh, Tom, etc.) have large energy resources; if fully utilized, they could generate more than $200 billion. kWh electricity per year. The first large Novosibirsk hydroelectric power station on the Ob River with a capacity of 400,000 kWh. kW entered service in 1959; above it, a reservoir with an area of 1070 km 2. In the future, it is planned to build a hydroelectric power station on the Yenisei (Osinovskaya, Igarskaya), in the upper reaches of the Ob (Kamenskaya, Baturinskaya), on the Tom (Tomskaya).

The waters of the large West Siberian rivers can also be used for irrigation and watering of the semi-desert and desert regions of Kazakhstan and Central Asia, which are already experiencing a significant shortage of water resources. Currently, design organizations are developing the main provisions and a feasibility study for the transfer of part of the flow of Siberian rivers to the Aral Sea basin. According to preliminary studies, the implementation of the first stage of this project should provide an annual transfer of 25 km 3 waters from Western Siberia to Central Asia. To this end, on the Irtysh, near Tobolsk, it is planned to create a large reservoir. From it, to the south along the Tobol valley and along the Turgai depression into the Syrdarya basin, the Ob-Caspian canal, more than 1500 meters long, will go to the reservoirs created there. km. The rise of water to the Tobol-Aral watershed is supposed to be carried out by a system of powerful pumping stations.

At the next stages of the project, the volume of water transferred annually can be increased to 60-80 km 3 . Since the waters of the Irtysh and Tobol will no longer be enough for this, the work of the second stage involves the construction of dams and reservoirs on the upper Ob, and possibly on the Chulym and Yenisei.

Naturally, the withdrawal of tens of cubic kilometers of water from the Ob and Irtysh should affect the regime of these rivers in their middle and lower reaches, as well as changes in the landscapes of the territories adjacent to the projected reservoirs and transfer channels. Forecasting the nature of these changes now occupies a prominent place in the scientific research of Siberian geographers.

Quite recently, many geologists, based on the idea of the uniformity of the thick strata of loose deposits that make up the plain and the apparent simplicity of its tectonic structure, very carefully assessed the possibility of discovering any valuable minerals in its depths. However, the geological and geophysical studies carried out in recent decades, accompanied by the drilling of deep wells, have shown the erroneousness of previous ideas about the poverty of the country in minerals and made it possible to imagine the prospects for the use of its mineral resources in a completely new way.

As a result of these studies, more than 120 oil fields have already been discovered in the strata of the Mesozoic (mainly Jurassic and Lower Cretaceous) deposits of the central regions of Western Siberia. The main oil-bearing areas are located in the Middle Ob region - in Nizhnevartovsk (including the Samotlor field, which can produce oil up to 100-120 million tons). t/year), Surgut (Ust-Balykskoe, Zapadno-Surgutskoe, etc.) and Yuzhno-Balyksky (Mamontovskoe, Pravdinskoe, etc.) districts. In addition, there are deposits in the Shaim region, in the Ural part of the plain.

In recent years, in the north of Western Siberia - in the lower reaches of the Ob, Taz and Yamal - the largest deposits of natural gas have also been discovered. The potential reserves of some of them (Urengoy, Medvezhye, Zapolyarny) amount to several trillion cubic meters; gas production at each can reach 75-100 billion cubic meters. m 3 per year. In general, the predicted gas reserves in the depths of Western Siberia are estimated at 40-50 trillion. m 3 , including categories A + B + C 1 - more than 10 trillion. m 3 .

Oil and gas fields of Western Siberia

The discovery of both oil and gas fields is of great importance for the development of the economy of Western Siberia and neighboring economic regions. The Tyumen and Tomsk regions are turning into important regions for the oil-producing, oil-refining and chemical industries. Already in 1975, more than 145 million tons of oil were mined here. t oil and tens of billions of cubic meters of gas. Oil pipelines Ust-Balyk - Omsk (965 km), Shaim - Tyumen (436 km), Samotlor - Ust-Balyk - Kurgan - Ufa - Almetyevsk, through which oil got access to the European part of the USSR - to the places of its greatest consumption. For the same purpose, the Tyumen-Surgut railway and gas pipelines were built, through which natural gas from West Siberian deposits goes to the Urals, as well as to the central and northwestern regions of the European part of the Soviet Union. In the last five-year plan, the construction of the giant supergas pipeline Siberia - Moscow (its length is more than 3,000 km) was completed. km), through which gas from the Medvezhye field is supplied to Moscow. In the future, gas from Western Siberia will go through pipelines to the countries of Western Europe.

Brown coal deposits have also become known, confined to the Mesozoic and Neogene deposits of the marginal regions of the plain (North-Sosva, Yenisei-Chulym and Ob-Irtysh basins). Western Siberia also has colossal peat reserves. In its peatlands, the total area of which exceeds 36.5 million hectares. ha, concluded a little less than 90 billion. t air-dry peat. This is almost 60% of all peat resources of the USSR.

Geological research led to the discovery of the deposit and other minerals. In the southeast, in the Upper Cretaceous and Paleogene sandstones of the vicinity of Kolpashev and Bakchar, large deposits of oolitic iron ores have been discovered. They lie relatively shallow (150-400 m), the iron content in them is up to 36-45%, and the predicted geological reserves of the West Siberian iron ore basin are estimated at 300-350 billion tons. t, including in one Bakcharskoye field - 40 billion cubic meters. t. Numerous salt lakes in the south of Western Siberia contain hundreds of millions of tons of common and Glauber's salt, as well as tens of millions of tons of soda. In addition, Western Siberia has huge reserves of raw materials for the production of building materials (sand, clay, marls); on its western and southern outskirts there are deposits of limestones, granites, diabases.

Western Siberia is one of the most important economic and geographical regions of the USSR. About 14 million people live on its territory (the average population density is 5 people per 1 km 2) (1976). In cities and workers' settlements there are machine-building, oil refineries and chemical plants, enterprises of the timber, light and food industries. Various branches of agriculture are of great importance in the economy of Western Siberia. It produces about 20% of the commercial grain of the USSR, a significant amount of various industrial crops, a lot of butter, meat and wool.

The decisions of the 25th Congress of the CPSU outlined further gigantic growth in the economy of Western Siberia and a significant increase in its importance in the economy of our country. In the coming years, it is planned to create new energy bases within its borders based on the use of cheap coal deposits and hydropower resources of the Yenisei and Ob, develop the oil and gas industry, and create new centers of mechanical engineering and chemistry.

The main directions of development of the national economy plan to continue the formation of the West Siberian territorial production complex, to turn Western Siberia into the USSR's main oil and gas production base. In 1980, 300-310 million tons will be produced here. t oil and up to 125-155 billion m 3 natural gas (about 30% of gas production in our country).

It is planned to continue the construction of the Tomsk petrochemical complex, put into operation the first stage of the Achinsk oil refinery, expand the construction of the Tobolsk petrochemical complex, build plants for processing petroleum gas, a system of powerful pipelines for transporting oil and gas from the northwestern regions of Western Siberia to the European part of the USSR and to oil refineries in the eastern regions of the country, as well as the Surgut-Nizhnevartovsk railway and to begin construction of the Surgut-Urengoi railway. The tasks of the five-year plan provide for accelerating the exploration of oil, natural gas and condensate fields in the Middle Ob and in the north of the Tyumen region. The harvesting of timber, the production of grain and livestock products will also increase substantially. In the southern regions of the country, it is planned to carry out a number of major land reclamation measures - to irrigate and water large areas of the Kulunda and Irtysh lands, to begin construction of the second stage of the Aley system and the Charysh group water pipeline, and to build drainage systems in Baraba.

West Siberian Plain(West Siberian lowland) - one of the largest accumulative lowland plains of the globe. It stretches from the shores of the Kara Sea to the steppes of Kazakhstan and from the Urals in the west to the Central Siberian Plateau in the east. The plain has the shape of a trapezoid narrowing to the north: the distance from its southern border to the northern reaches almost 2500 km, the width is from 800 to 1900 km, and the area is only slightly less than 3 million km 2. It occupies the entire western part of Siberia from the Ural Mountains in the west to the Central Siberian Plateau in the east; the regions of Russia and Kazakhstan are located on it. The geographical position of the West Siberian Plain determines the transitional nature of its climate between the temperate continental climate of the Russian Plain and the sharply continental climate of Central Siberia. Therefore, the landscapes of the country are distinguished by a number of peculiar features: the natural zones here are somewhat shifted to the north compared to the Russian Plain, there is no zone of broad-leaved forests, and landscape differences within the zones are less noticeable than on the Russian Plain.

Geological structure and history of development

The West Siberian Plain is located within the epihercynian West Siberian Plate, the basement of which is composed of intensely dislocated and metamorphosed Paleozoic deposits, similar in nature to those of the Urals, and in the south of the Kazakh uplands. The formation of the main folded structures of the basement of Western Siberia, which have a predominantly meridional direction, refers to the era of the Hercynian orogeny. They are everywhere covered with a cover of loose marine and continental Meso-Cenozoic rocks (clays, sandstones, marls, and the like) with a total thickness of more than 1000 m (in the basement depressions up to 3000-4000 m). The youngest, anthropogenic deposits in the south are alluvial and lacustrine, often covered with loess and loess-like loams; in the north - glacial, sea and ice-sea (thickness in places up to 4070 m).

The tectonic structure of the West Siberian plate is rather heterogeneous. However, even its large structural elements appear in the modern relief less distinctly than the tectonic structures of the Russian platform. This is explained by the fact that the relief of the surface of the Paleozoic rocks, lowered to a great depth, is leveled here by the cover of Meso-Cenozoic deposits, the thickness of which exceeds 1000 m, and in individual depressions and syneclises of the Paleozoic basement - 3000-6000 m.

The events of the Quaternary period had a particularly great influence on the formation of the landscapes of Western Siberia. During this time, the territory of the country experienced repeated subsidence and was still an area of predominantly accumulation of loose alluvial, lacustrine, and in the north - marine and glacial deposits. The thickness of the Quaternary cover reaches 200-250 m in the northern and central regions. However, in the south it noticeably decreases (in some places up to 5-10 m), and in the modern relief the effects of differentiated neotectonic movements are clearly expressed, as a result of which swell-like uplifts arose, often coinciding with positive structures of the Mesozoic sedimentary cover.

Lower Quaternary deposits are represented in the north of the plain by alluvial sands that fill buried valleys. The base of the alluvium is sometimes located in them 200-210 m below the modern level of the Kara Sea. Above them in the north, pre-glacial clays and loams with fossil remains of the tundra flora usually occur, which indicates a noticeable cooling of Western Siberia that had already begun at that time. However, in the southern regions of the country, dark coniferous forests with an admixture of birch and alder prevailed.

Along with typical glacial rocks, the composition of the sediments of the Samarovo stratum also includes marine and glacial-marine clays and loams formed at the bottom of the sea advancing from the north. Therefore, the typical moraine relief forms are less distinct here than on the Russian Plain. On the lacustrine and fluvioglacial plains adjacent to the southern edge of the glaciers, forest-tundra landscapes then prevailed, and in the extreme south of the country loess-like loams were formed, in which pollen of steppe plants (wormwood, kermek) is found. Marine transgression continued in the post-Samarovo time, the deposits of which are represented in the north of Western Siberia by Messov sands and clays of the Sanchugov Formation. In the northeastern part of the plain, moraines and glacial-marine loams of the younger Taz glaciation are common. The interglacial epoch, which began after the retreat of the ice sheet, was marked in the north by the spread of the Kazantsevo marine transgression, whose deposits in the lower reaches of the Yenisei and Ob contain the remains of a more heat-loving marine fauna than currently living in the Kara Sea.

The last, Zyryansk, glaciation was preceded by a regression of the boreal sea, caused by uplifts in the northern regions of the West Siberian Plain, the Urals, and the Central Siberian Plateau; the amplitude of these uplifts was only a few tens of meters. During the maximum stage of development of the Zyryansk glaciation, glaciers descended into the regions of the Yenisei Plain and the eastern foot of the Urals to approximately 66 ° N. sh., where a number of stadial terminal moraines were left. In the south of Western Siberia, sandy-argillaceous Quaternary deposits were blown over at that time, eolian landforms were formed, and loess-like loams were accumulating.

Some researchers of the northern regions of the country draw a more complex picture of the events of the Quaternary glaciation in Western Siberia. So, according to the geologist V.N. Saks and geomorphologist G.I. Lazukov, glaciation began here as early as the Lower Quaternary and consisted of four independent epochs: Yarskaya, Samarovo, Tazovskaya and Zyryanskaya. Geologists S.A. Yakovlev and V.A. Zubakov even counts six glaciations, referring the beginning of the most ancient of them to the Pliocene.

On the other hand, there are supporters of a one-time glaciation of Western Siberia. Geographer A.I. Popov, for example, considers the deposits of the glacial period of the northern half of the country as a single water-glacial complex consisting of marine and glacial-marine clays, loams and sands containing inclusions of boulder material. In his opinion, there were no extensive ice sheets on the territory of Western Siberia, since typical moraines are found only in the extreme western (at the foot of the Urals) and eastern (near the ledge of the Central Siberian Plateau) regions. The middle part of the northern half of the plain during the epoch of glaciation was covered by the waters of marine transgression; the boulders enclosed in its deposits are brought here by icebergs that have come off the edge of the glaciers that descended from the Central Siberian Plateau. Only one Quaternary glaciation of Western Siberia is recognized by the geologist V.I. Gromov.

At the end of the Zyryansk glaciation, the northern coastal regions of the West Siberian Plain again sank. The subsided areas were flooded by the waters of the Kara Sea and covered with marine sediments that form post-glacial marine terraces, the highest of which rises 50-60 m above the modern level of the Kara Sea. Then, after the regression of the sea, a new incision of rivers began in the southern half of the plain. Due to the small slopes of the channel in most of the river valleys of Western Siberia, lateral erosion prevailed, the deepening of the valleys proceeded slowly, therefore they usually have a considerable width, but a small depth. In poorly drained interfluve spaces, the reworking of the ice age relief continued: in the north, it consisted in leveling the surface under the influence of solifluction processes; in the southern, non-glacial provinces, where more precipitation fell, the processes of deluvial washout played a particularly important role in the transformation of the relief.

Paleobotanical materials suggest that after the glaciation there was a period with a slightly drier and warmer climate than now. This is confirmed, in particular, by the findings of stumps and tree trunks in the deposits of the tundra regions of Yamal and the Gydan Peninsula at a distance of 300-400 km. to the north of the modern border of woody vegetation and the wide development of the tundra zone of relict large-hilly peatlands in the south.

Sources

Gvozdetsky N.A., Mikhailov N.I. Physical geography of the USSR. Ed. 3rd. M., "Thought", 1978.

Literature

West Siberian lowland. Essay on nature, M., 1963; Western Siberia, M., 1963.
Davydova M.I., Rakovskaya E.M., Tushinsky G.K. Physical geography of the USSR. T. 1. M., Education, 1989.

The West Siberian Plain, which occupies about 3 million sq. km 2, is one of the greatest plains of the globe: in size it can only be compared with the Amazonian lowland.

The boundaries of the lowland are clearly defined natural boundaries: in the north - the coastline of the Kara Sea, in the south - the Turgai Tableland, the foothills of the Kazakh hills, Altai, Salair and Kuznetsk Alatau, in the west - the eastern foothills of the Urals, in the east - the valley of the river. Yenisei. The orographic boundaries of the lowland coincide with the geological ones, which are considered to be outcrops in some places along the edges of the lowland of dislocated Paleozoic and older rocks, for example, in the south, near the Kazakh hills. In the Turgai trough, which connects the West Siberian lowland with the plains of Central Asia, the boundary is drawn along the Kustanai swell, where the pre-Mesozoic basement lies at a depth of 50-150 m from the surface. The length of the plain from north to south - 2500 km. The largest width - 1500 km- it reaches in the southern part. In the north of the lowland, the distance between the western and eastern points is about 900-950 km. Almost the entire territory of the lowland is located within the RSFSR - the Yamalo-Nenets and Khanty-Mansiysk national districts, in the regions - Kurgan, Sverdlovsk, Tyumen, Omsk, Novosibirsk, Tomsk, Kemerovo; in the regions - Altai and Krasnoyarsk. The southern part belongs to the Kazakh SSR - to the regions of the Virgin Territory - Kustanai, North Kazakhstan, Kokchetav, Tselinograd, Pavlodar and Semipalatinsk.

Relief and geological structure. The relief of the West Siberian Plain is characterized by complexity and diversity. Over a long distance, the fluctuations in altitude are insignificant. Maximum marks (250-300 m) concentrated in the western part of the plain - in the Urals. The southern and eastern parts of the plain are also elevated compared to the central one. In the south, heights reach 200-300 m. In the central part of the plain, the absolute marks on the watersheds are about 50-150 m, and in the valleys - less than 50 m; For example, in the river valley Ob, at the mouth of the river. Wah, altitude 35 m, and near the city of Khanty-Mansiysk - 19m.

On the peninsulas, the surface rises: absolute marks on the Gydan Peninsula reach 150-183 m, and on Tazovsky - about 100m.

In general orographic terms, the West Siberian Plain has a concave shape with raised edges and a lowered central part. Along its outskirts there are hills, plateaus and sloping plains, descending towards its central parts. Among them, the largest are: the North Sosva, Tobolsk-Tavda, Ishim, Ishim-Irtysh and Pavlodar sloping plains, Vasyugan, Ob and Chulym-Yenisei plateaus, Vakh-Ket and Srednetazovsky uplands, etc.

To the north of the latitudinal current of the Ob, from the Urals to the Yenisei, one hill after another extends, forming a single orographic axis of the West Siberian Plain - the Siberian Uvals, along which the Ob-Taz and Ob-Pursky watersheds pass. All large lowlands are concentrated in the central parts of the plain - Khanty-Mansiysk, Surgut woodland, Sredneobskaya, Purskaya, Khetskaya, Ust-Obskaya, Barabinskaya and Kulundinskaya.

The flatness of the territory was created by a long geological history in the pre-Quaternary time. The entire West Siberian Plain is located in the area of Paleozoic folding and represents in tectonic terms the West Siberian plate of the Ural-Siberian epi-Hercynian platform. The folded structures that were on the site of the West Siberian Plain, as a result of tectonic movements, sank to different depths either at the end of the Paleozoic, or at the very beginning of the Mesozoic (in the Triassic).

Deep boreholes in various parts of the plain penetrated Cenozoic and Mesozoic rocks and reached the surface of the slab basement at various depths: at the Makushkino railway station (half the distance between Kurgan and Petropavlovsk) - at a depth of 693 m(550 m from sea level), at 70 km east of Petropavlovsk - at 920 m(745 m from sea level), and in the city of Turgay - by 325 m. In the region of the eastern slope of the Severo-Sosvinsky arch, the Paleozoic basement was lowered to a depth of 1700-2200 m, and in the central part of the Khanty-Mansiysk depression - 3500-3700 m.

The subsided sections of the foundation formed syneclises and troughs. In some of them, the thickness of Mesozoic and Cenozoic loose deposits reaches more than 3000m 3.

In the north of the West Siberian Plate, in the interfluve of the rivers of the lower Ob and Taz, the Ob-Taz syneclise stands out, and in the south, along the course of the middle Irtysh, the Irtysh syneclise and in the region of Kulunda Lake, the Kulunda depression. In the north, plates in syneclises, according to the latest data,

the foundation goes to a depth of 6000 m, and in places - by 10,000 m. In anteclises, the foundation lies at a depth of 3000-4000 m from the surface.

According to the geological structure, the basement of the West Siberian Plate is apparently heterogeneous. It is assumed that it consists of folded structures of the Hercynian, Caledonian, Baikal and older ages.

Some large geological structures of the West Siberian Plate - syneclises and anteclises - in the relief of the plain correspond to elevated and low-lying areas. For example, the syneclise lowlands: the Baraba lowland corresponds to the Omsk depression, the Khanty-Mansiysk lowland was formed on the site of the Khanty-Mansiysk depression. Examples of anteclise elevations are: Lyulinvor and Verkhnetazovskaya. In the marginal parts of the West Siberian Plate, sloping plains correspond to monoclinal morphological structures, in which the general lowering of the topographic surface follows the subsidence of the basement into plate syneclises. Such morphostructures include the Pavlodar, Tobolsk-Tavda sloping plains, etc.

During the Mesozoic, the entire territory was a mobile land area, which experienced only epeirogenic fluctuations with a general tendency to subside, as a result of which the continental regime was replaced by a marine one. Thick layers of sediments accumulated in the sea basins. It is known that in the Upper Jurassic the sea occupied the entire northern part of the plain. In the Cretaceous period, many parts of the plains turned into dry land. This is evidenced by findings of the weathering crust and continental deposits.

The Upper Cretaceous sea was replaced by the Tertiary. The deposits of the Paleogene seas smoothed out the pre-Tertiary relief and created the ideal flatness of the West Siberian Plain. The sea reached its maximum development in the Eocene era: at that time it covered almost the entire area of the West Siberian Plain and the connection of the sea basins of the Aral-Caspian depression with the West Siberian Plain was carried out through the Turgai Strait. During the entire Paleogene, there was a gradual subsidence of the plate, which reached its greatest depth in the eastern regions. This is evidenced by the thickness and nature of the Paleogene deposits increasing to the east: in the west, in the Cis-Urals, near the Kazakh uplands, sands, conglomerates and pebbles predominate. Here they are highly elevated and come to the surface or lie at shallow depths. Their thickness in the west reaches 40-100 m. To the east and north, sediments subside under Neogene and Quaternary deposits. So, for example, in the Omsk region, Paleogene deposits were discovered by boreholes at a depth of more than 300 m from the surface, and even deeper they lie to the north of the station. Tatar. Here they become thinner (clays, flasks). At the confluence of the river Irtysh in the river. Ob and north along the river. The Ob Paleogene layers rise again and emerge along the river valleys in natural outcrops.

After a long maritime regime, the primary accumulative plain rose by the beginning of the Neogene, and a continental regime was established on it. Judging by the nature of the occurrence of the Paleogene deposits, it can be said that the primary accumulative marine plain had a bowl-shaped relief structure: it was all lowered most in the central part. This structure of the surface to the beginning of the Neogene predetermined mainly the modern features of the relief of the West Siberian Plain. The land was covered during this period by numerous lakes and lush subtropical vegetation. This is evidenced by the wide distribution of exclusively continental deposits, consisting of pebbles, sand, sandy loam, loams and clays of lacustrine and river origin. The best sections of these deposits are known along the Irtysh, Tavda, Tura, and Tobol rivers. Remains of flora (marsh cypress, sequoia, magnolia, linden, walnut) and fauna (giraffes, camels, mastodons) are well preserved in the deposits, which indicates warmer climatic conditions in the Neogene compared to modern ones.

In the Quaternary period, a cooling of the climate occurred, which led to the development of an ice sheet in the northern half of the plain. The West Siberian Plain has experienced three ice sheets (Samarovskoe, Tazovskoe and Zyryanskoe). Glaciers descended to the plain from two centers: from the mountains of Novaya Zemlya, the Polar Urals and from the mountains of Byrranga and Putorana. The existence of two centers of glaciation in the West Siberian Plain is proved by the distribution of boulders. Boulder glacial deposits cover vast expanses of the plain. However, in the western part of the plain - along the lower reaches of the Irtysh and Ob rivers - boulders consist mainly of Ural rocks (granites, granodiorites), and in the eastern part - along the valleys of the Vakha, Ob, Bolshoi Yugan and Salym rivers, fragments of traps predominate in the interfluves of the Gydan Peninsula, brought from the northeast from the Taimyr center. The ice cover descended during the Samarovsk glaciation along the leveled surface to the south, to approximately 58 ° N. sh.

The southern edge of the glacier stopped the flow of pre-glacial rivers that directed their waters to the Kara Sea basin. Part of the river waters apparently reached the Kara Sea. At the southern edge of the glacier, lake basins arose, powerful fluvioglacial flows formed, flowing southwest, towards the Turgai Strait.

In the south of the West Siberian Plain, from the foothills of the Urals to the Irtysh, and in some places further to the east (Prichulym plateau), loess-like loams are common; they lie on the surface of interfluve plateaus, overlapping their bedrocks. It is assumed that the formation of loess-like loams is associated with eolian or eluvial processes, and possibly these are deltaic and coastal deposits of ancient seas.

In the interglacial periods, the northern part of the West Siberian Lowland was flooded with waters of boreal transgression, which penetrated along the valleys of large rivers - the Ob, Tazu, Puru, Yenisei, and others. Yenisei - up to 63 ° N. sh. The central part of the Gydan Peninsula was an island in the marine boreal basin.

The boreal sea was much warmer than the modern one, as evidenced by marine sediments formed by fine sandy loams and loams with the inclusion of heat-loving mollusks. They lie at an altitude of 85-95 m above present sea level.

The last glaciation in Western Siberia did not have a cover character. Glaciers descending from the Urals, Taimyr and the Norilsk Mountains ended not far from their centers. This is indicated by the location of their terminal moraines and the absence of moraine deposits of the last glaciation in the northern part of the West Siberian Plain. So, for example, marine

deposits of boreal transgression in the north of the lowland are nowhere covered by moraine.

In the distribution of various genetic types of relief over the territory, a successive change is observed when moving from north to south, which makes it possible to distinguish geomorphological zones.

1. The zone of the Pre-Karsky marine stepped accumulative plains occupies the entire coastal strip of the Kara Sea, extending deep into the interior of the mainland along the Ob, Taz and Yenisei bays. The plain is composed of marine clays and sands during the boreal transgression; it rises to a height of 80 m. Toward the coastline, the heights decrease, forming several sea terraces.

2. The zone of the Ob-Yenisei accumulative hilly and plane-undulating water-glacial plains is located between 70 and 57 ° N. t., from the Urals to the Yenisei. On the Gydan and Yamal peninsulas, it occupies inland areas, extending north of 70 ° N. sh., and in the Cis-Urals it descends south of 60 ° N. sh., in the basin of the river. Tavda. In the central regions, up to the southern boundary of the Samarovsk glaciation, this territory was covered with ice sheets. It is composed of boulder clays, boulder sands, and loams.

Prevailing heights above sea level - 100-200 m. The surface of the plain is flat-undulating, with moraine hills 30-40 m, with ridges and shallow lacustrine depressions, ridged relief and ancient runoff hollows. Large areas are occupied by outwash lowlands. Especially many lakes are found among the vast interfluve swamps of the Ob-Taz plain.

3. The zone of near-glacial water-accumulation plains is located south of the boundary of maximum glaciation and extends from the river. Tavda, south of the latitudinal segment of the Irtysh valley, to the river. Yenisei.

4. The zone of non-glacial flat and wavy-ravine erosion-accumulative plains includes the Ishim Plain, located in the basin of the river. Ishim, Baraba and Kulunda steppes. The main landforms were created by powerful water flows, which formed wide hollows of the ancient runoff in a southwestern direction, filled with alluvial deposits. The watershed near-glacial regions have a ridged relief. Manes height 5-10 m elongated mainly in the same direction as the hollows of the ancient runoff. They are especially pronounced in the Kulunda and Baraba steppes.

5. The zone of foothill denudation plains adjoins the mountain structures of the Urals, the Salair Ridge and the Kuznetsk Alatau. Piedmont plains are the most elevated parts of the territory of the West Siberian Plain; they are composed of deposits of the Mesozoic and Tertiary ages and are overlain by Quaternary loess-like eluvial-deluvial loams. The surfaces of the plains are dissected by wide erosional valleys. The watershed areas are flat, with closed basins, depressions, some of them contain lakes.

Thus, on the territory of the West Siberian Plain, geomorphological zoning is clearly revealed, which is due to the history of the development of the entire territory, especially during the Ice Age. Geomorphological zoning is predetermined by the activity of glaciers, Quaternary tectonic movements, and boreal transgression.

When comparing the geomorphological zones of the West Siberian and Russian plains, a general pattern is revealed, namely: both here and there

narrow strips of sea plains, an area of glacial drift (located in the northwest and northeast), zones of glacial accumulation, stripes of woodlands and non-glacial zones are clearly visible. But on the Russian Plain, the non-glacial zone ends with sea plains, and on the West Siberian Plain, with a zone of foothill plains.

The valleys of the Ob and Irtysh rivers, reaching a width of 80-120 km, pass through all these geomorphological zones. Valleys cut through Quaternary and Tertiary deposits to a depth of 60-80 m. The floodplains of these rivers are 20-40 km have numerous meandering channels, oxbow lakes, coastal ridges. Terraces rise above the floodplains. Everywhere in the valleys there are two terraces of the accumulative-erosion type with a height of 10-15 and about 40 m. In the foothills, the valleys narrow, the number of terraces increases to six, their height increases to 120 m. The valleys have an asymmetric structure. On steep slopes, ravines and landslides are developed.

Minerals are concentrated in the primary and Quaternary deposits of the plain. In the Jurassic deposits there are deposits of coal explored in the southwestern part of the plain and in the Turgai plain. Brown coal deposits have been discovered in the Middle Ob basin. The Sredneobsky basin includes the Tomskoye, Prichulymskoye, Narymskoye and Tymskoye deposits. The Cretaceous deposits of the plain contain phosphorites and bauxites discovered in the northern part of the Turgai trough. Iron ore deposits have recently been discovered among the Cretaceous deposits in the south of the West Siberian Plain and in the northwestern part of the Turgai Trough, represented by oolitic iron ore. In recent years, on the territory of the West Siberian Plain, deep drilling has revealed iron ore deposits on the left bank of the Ob, from the city of Kolpashevo to the village. Narym, and, moreover, in the basins of the Vasyugan, Keti and Tyma rivers. Iron ores contain iron - from 30 to 45%. Deposits of iron ores have been discovered in the Kulunda steppe (the region of Lake Kuchu k, Kulunda station, Klyuchi), they contain up to 22% iron. Large gas fields are known in the Tyumen region (Berezovskoye and Punginskoye). At the end of 1959, from a borehole laid on the bank of the river. Konda (near the village of Shaim), the first commercial oil in Western Siberia was obtained. In March 1961, a well was blocked in the center of the West Siberian Lowland, in the middle reaches of the river. Ob, near the village of Megion. Commercial oil is concentrated in the Lower Cretaceous deposits. Oil and gas fields are confined to the Jurassic and Cretaceous rocks. The Paleogene deposits of the southern part of the lowland and the Turgai trough have deposits of oolitic iron ores, lignites, and bauxites. Building materials are widespread throughout the territory - sands and clays of marine and continental origin (Mesozoic and Quaternary), peat bogs. The peat reserves are huge. The total volume of explored peatlands is more than 400 million hectares. m 2 air-dry peat. The average thickness of peat layers is 2.5-3 m. In some hollows of ancient runoff (Tym-Paiduginskaya and others), the thickness of peat layers reaches 5 - 6 m, In the lakes of the southern part there are large reserves of salts (table salt, mirabilite, soda).

Climate. The climate of the West Siberian Plain is formed as a result of the interaction of a number of factors, namely:

1) geographical location. The main part of the surface is located in temperate latitudes, and the peninsulas are located beyond the Arctic Circle.

The entire plain is thousands of kilometers away from the Pacific and Atlantic oceans. The large extent of the territory from north to south predetermines different amounts of total radiation, which significantly affects the distribution of air and ground temperatures. The total radiation increases when moving from north to south from 60 to 110 kcal / cm 2 per year and is distributed almost zonally. It reaches its greatest value at all latitudes in July (in Salekhard - 15.8 kcal / cm 2, in Pavlodar -16.7 kcal / cm 2). In addition, the position of the territory in temperate latitudes determines the inflow

air masses from the Atlantic Ocean under the influence of west-east transfer. The significant remoteness of the West Siberian Plain from the Atlantic and Pacific Oceans creates conditions above its surface for the formation of a continental climate;

2) pressure distribution. Areas of high (Asian anticyclone and Voeikov axis) and low pressure (over the Kara Sea and Central Asia) determine the strength of the wind, its direction and movement;

3) the relief of the marshy and concave plain, open to the Arctic Ocean, does not prevent the intrusion of cold arctic air masses. They freely penetrate to Kazakhstan, changing during their movement. The flatness of the territory contributes to the penetration of continental tropical air far to the north. Thus, meridional air circulation also occurs. The Ural Mountains have a significant impact on the amount and distribution of precipitation in the plain, since a significant part of it falls on the western slopes of the Urals? and the western air masses come to the West Siberian Plain already drier;

4) the properties of the underlying surface - a large forest cover, waterlogging and a significant number of lakes - have a significant impact on the distribution of a number of meteorological elements.

In winter, the entire area is very cold. To the east of the West Siberian Plain, a stable region of the Asian High is being formed. Its spur is the Voeikov axis, which stretches across the southern part of the plain from November to March. Above the Kara Sea, a depression of low pressure of the Icelandic Low extends: the pressure decreases from south to north - towards the Kara Sea. Therefore, south, southwest and southeast winds prevail.

Winter is characterized by stable negative temperatures. Absolute minima reach from -45 to -54°. January isotherms in the northern part of the plain have a meridional direction, but south of the Arctic Circle (about 63-65 Q With. sh.) - southeast.

The isotherm is -15° in the south, and -30° in the northeast. The western part of the plain is warmer than the eastern part by 10°. This is explained by the fact that the western parts of the territory are under the influence of western air masses, while in the east the territory is cooled by the action of the Asian anticyclone.

Snow cover in the north appears in the first decade of October and stays on the peninsulas for about 240-260 days. At the end of November, almost the entire territory is covered with snow. In the south, snow lasts up to 160 days and usually melts at the end of April, and in the north - at the end of June (20/VI).

In summer, over the whole of Asia, as well as over the territory of the West Siberian Plain, the pressure is lowered, therefore Arctic air freely penetrates into its territory. When moving south, it warms up and is additionally moistened due to local evaporation. But the air warms up faster than it gets humidified, which causes a decrease in its relative humidity. The warmer western air masses arriving on the West Siberian Plain are more transformed along the way than the Arctic ones. Intensive transformation of both Arctic and Atlantic air masses leads to the fact that the territory of the lowland is filled with dry continental temperate air, which has a high temperature. Cyclonic activity develops most intensively in the northern part of the plain, due to the intensification of temperature differences between the cold arctic and warm continental air, i.e., on the arctic front line. In the middle and southern parts of the plain, cyclonic activity is weakened, but cyclones still penetrate here from the European territory of the USSR.

The average July isotherms run almost in the latitudinal direction. In the far north, through about. Bely, the isotherm + 5 ° passes, the isotherm + 15 ° goes south of the Arctic Circle, the isotherm + 20, + 22 ° stretches through the steppe regions with a deviation to the southeast - towards Altai. The absolute maximum in the north reaches +27°, and in the south +41°. Thus, when moving from north to south, changes in summer temperatures are more significant compared to winter ones. The growing season, due to the temperature regime, also changes when moving from north to south: in the north it reaches 100 days, and in the south - 175 days.

Precipitation is distributed unevenly over the territory and over the seasons. Most rainfall - 400 to 500 mm- drops out in the middle strip of the plain. To the north and south, the amount of precipitation decreases markedly (up to 257 mm - on Dixon Island and 207 mm- in Semipalatinsk). The greatest amount of precipitation falls throughout the plain from May to October. But the maximum precipitation gradually passes from south to north: in June it is in the steppe, in July - in the taiga, in August - in the tundra. Showers are observed during the passage of a cold front and during thermal convection.

In the middle and southern stripes of the plain, thunderstorms occur from May to August. So, for example, in the Baraba and Kulunda steppes, it is observed during the warm period from 15 to 20 days with thunderstorms. In Tobolsk, Tomsk, Tselinograd it was noted in July up to 7-8 days with thunderstorms. During thunderstorms, squalls, heavy showers, and hail are frequent.

The West Siberian Plain is crossed by three climatic zones: arctic, subarctic and temperate.

Rivers and lakes. The rivers of the West Siberian Plain belong to the basins of the Ob, Taz, Pur and Yenisei. The Ob basin covers an area of about 3 million sq. km 2 and is one of the greatest river basins in the USSR.

Large rivers - the Ob, Irtysh, Ishim, Tobol - flow through several geographical zones, which determines the diversity of morphological and hydrological features of individual sections of the rivers and their valleys. All rivers of the West Siberian Plain are typically flat. They have small slopes: the average slope of the river. Ob - 0.000042, r. Irtysh from Omsk to the mouth - 0.000022.

The rivers flowing into the Ob and Irtysh have a flow velocity of 0.1-0.3 in the summer within the taiga region. m/s, and in the spring flood - 1.0 m/sec. All rivers flow in loose, mainly in Quaternary sediments, have a large sinuosity of the channel, wide valleys with well-defined floodplains and terraces.

The largest rivers - the Ob, Irtysh, Tobol - and many of their tributaries begin in the mountains. Therefore, they bring a large amount of detrital material to the West Siberian Plain and their hydrological regime depends in part on the melting of snow and ice in the mountains. The main course of the lowland rivers is directed to the north-north-west. The peculiarities of the ice regime are associated with this: on all rivers, ice formation begins in the lower reaches and

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gradually moves upstream. In the north, freeze-up lasts 219 days, and in the south - 162 days. The spring ice drift begins in the upper parts of the basins and gradually passes to the mouths of the rivers, as a result of which powerful ice jams form on large rivers and the water level in the rivers rises sharply. This creates strong floods and leads to vigorous development of lateral erosion in the valleys.

In the south, the rivers break up in April - May, in the north - from mid-May to mid-June. The duration of the spring ice drift is usually up to 25 days, but can reach up to 40 days. This is due to the following reasons: in the territory located in the lower reaches of the rivers, spring comes later; the ice on the rivers in the lower reaches reaches a large thickness, and therefore a large amount of heat is spent on its melting.

Rivers freeze from north to south in a much shorter period of time, about 10-15 days. The average duration of the navigation period in the upper reaches is 180-190 days (near Novosibirsk - 185 days, in the lower reaches - 155 days).

West Siberian rivers are fed mainly by snow, but, in addition, rain and soil. All rivers have a spring flood, and it can last quite a long time. The spring flood gradually turns into a summer flood, which depends on rains and groundwater.

River Ob. The Ob begins near the city of Biysk at the confluence of the Biya and Katun rivers. The length of the Ob, counting from the confluence of these rivers, is 3680 km, and if we take the source of the river as the beginning of the Ob. Katun, then its length will be 4345 km. The length of the Ob-Irtysh system from the sources of the Irtysh to the Kara Sea (including the Gulf of Ob) - 6370 km. According to the water content of the river The Ob occupies the third place among the rivers of the USSR, yielding the first two places to the Yenisei and Lena. Its average annual water consumption is 12,500 m 3 / sec.

The largest tributaries of the The Ob receives from the left (the Irtysh River with the Ishim and Tobol rivers), the right tributaries are much shorter, so the configuration of the river basin has an asymmetric shape: the right-bank part of the basin makes up 33% of the catchment area, and the left-bank part - 67%.

According to hydrographic and hydrological conditions and morphology of the valley of the river. The Ob is subdivided into three parts: The Upper Ob - from the confluence of the Biya and Katun rivers to the mouth of the river. Tom, Middle Ob - from the mouth of the river. Tom to the mouth of the river. Irtysh and Lower Ob - from the mouth of the river. Irtysh to the Gulf of Ob. The Upper Ob flows in the hilly foothills of the steppe Altai. The main tributaries of the Upper Ob are: on the right - the river. Chumysh and r. Inya, flowing through the Kuznetsk basin, on the left - the Charysh and Alei rivers, flowing from Altai.

The middle Ob flows through the marshy taiga plains, crossing the Vasyuganye-marshy plains. This area is characterized by excessive moisture, slight slopes of the surface and a dense network of slowly flowing rivers. In the middle reaches of the river The Ob receives many tributaries from both sides. The Lower Ob flows in a wide valley through the northern part of the taiga and forest-tundra.

Irtysh River - the largest tributary Obi. Its length is 4422 km, pool area - 1 595 680 km 2. The sources of the Irtysh are located at the edge of the glaciers and mountains of the Mongolian Altai.

The largest tributaries of the Irtysh on the right are the rivers Bukhtarma, Om, Tara, Demyanka, and on the left - Ishim, Tobol, Konda. The Irtysh flows through the steppe, forest-steppe and taiga zones. It receives large tributaries in the taiga zone, and the most stormy - from the Altai mountains; in the steppe - from

Semipalatinsk to Omsk, i.e. at a distance of over 1000 km, The Irtysh has almost no tributaries.

The narrowest section of the river valley. Irtysh - from the mouth of Bukhtarma to the city of Ust-Kamenogorsk. Here the river flows in a mountain gorge. Near the city of Semipalatinsk The Irtysh enters the West Siberian Plain and is already a typically flat river with a wide valley - up to 10-20 km width, and at the mouth - up to 30-35 km. The river bed is divided into branches by numerous sandy islands; the slopes of the channel are insignificant, the banks are composed of sandy-argillaceous deposits. Throughout the river The right side of the Irtysh is the highest bank.

Lakes. There are many lakes on the West Siberian Plain. They are found in all natural zones of the plain and are distributed both in river valleys and on watersheds. A large number of lakes is due to the flatness and poor drainage of the territory; activity of the ice cap and its melt waters; permafrost-failure phenomena; river activities; suffusion processes occurring in loose deposits of the southern part of the lowland; destruction of peatlands.

According to the origin of the basins, the lakes of the West Siberian Plain are divided into the following types: 1) lacustrine basins that have inherited the deepened sections of the hollows of the ancient runoff. Their formation is associated with the activity of water flows in the marginal zones of ancient glaciations and in the areas of flow of dammed waters of the Ob and Yenisei rivers during ice sheets. Lakes of this type are located in ancient runoff hollows. They are predominantly elongated or oval in shape and insignificant (0.4-0.8 m) depth: however, sometimes they reach a depth of 25 m; 2) lacustrine basins of depressions between ridges of outwash plains, most common in the south in the forest-steppe and steppe; 3) oxbow lakes of modern and ancient river valleys. The formation of such lakes is associated with abrupt changes in river channels in accumulative deposits. Their shapes and sizes are very diverse; 4) lake basins caused by thermokarst. They are common in the north of the plain in permafrost conditions and are found on all elements of the relief. Their sizes are varied, but not more than 2-3 km in diameter, depth - up to 10-15 m; 5) moraine lake basins formed in depressions of moraine deposits, especially in the marginal parts of ice sheets. An example of such lakes is the northern group of lakes on the Yenisei-Taz interfluve within the Siberian Uvals. In the south of the forest zone, ancient moraine lakes already have a transitional stage; 6) sory lakes formed in depressions in the mouth parts of tributaries in the lower reaches of the Ob and Irtysh rivers. During floods and spring floods, depressions are filled with water, forming huge reservoirs with an area of several hundred square kilometers and a depth of 1-3 m, and in channels - 5-10 m. In summer, they gradually discharge water into the channels of the main river, and in the middle of summer, and sometimes by the end of it, flat areas covered with silt remain in place of the reservoirs. Lakes - sors - favorite places for feeding many species of fish, as they quickly heat up and are rich in food; 7) secondary lakes, the basins of which are formed due to the destruction of peat bogs. They are common in swamp forests on flat watersheds and river terraces. Their sizes reach from several square meters to several square kilometers at a depth of 1.5-2 m. There are no fish in them; 8) suffusion lake basins, common in the southern regions of the lowland. In loose deposits, from which silt particles are washed out under the action of groundwater, soil subsidence occurs. Depressions, funnels, saucers are formed on the surface. The emergence of the basins of many saline and bitter-salty lakes is apparently associated with suffusion processes.

Ground water. According to hydrogeological conditions, the West Siberian Plain is a huge artesian basin, which is called the West Siberian. The ground waters of Western Siberia are characterized by various conditions of occurrence, chemistry and regime. They lie at different depths in primary pre-Mesozoic, Meso-Cenozoic and Quaternary deposits. Aquifers are sands - marine and continental (alluvial and outwash), sandstones, loams, sandy loams, flasks, dense fractured rocks of a folded foundation.

The main areas of modern nutrition of the artesian basin are located in the southeast and south (Chulyshman, Irtysh and Tobolsk basins). The movement of water occurs from the southeast and south to north.

The groundwater of the foundation is concentrated in the cracks in the rocks. They are distributed in its peripheral part to a depth of approximately 200-300 m and at this depth they overflow into the loose strata of the Meso-Cenozoic. This is confirmed by the almost complete absence of water in deep wells in the central part of the basin.

In the Quaternary deposits, the waters are mostly free-flowing, except for those areas where they are concentrated in intermorainic fluvioglacial deposits and among the loamy strata of the Ob plateau.

In the Irtysh and Tobolsk artesian basins, the waters of the Quaternary deposits are fresh, saline, and brine in composition. In the rest of the West Siberian basin, the waters of the Quaternary deposits are fresh hydrocarbonate with a mineralization rarely exceeding 0.5g/l.

The rivers and lakes of the West Siberian Plain are widely used in the national economy. In flat wetlands, rivers are the most important means of communication. The Ob River and its major tributaries - the Irtysh, Tobol, Vasyugan, Parabel, Ket, Chulym, Tom, Charysh and others - are used for regular navigation. The total length of shipping routes within the West Siberian Plain is more than 20,000 km. The Ob River connects the Northern Sea Route with the railways of Siberia and Central Asia. The significant branching of the river systems of the West Siberian Plain makes it possible to use the tributaries of the Ob and Irtysh to transport goods from west to east and back over long distances. The most significant drawback of the Ob basin as a transport route is its isolation from neighboring river basins, despite the fact that the upper reaches of many tributaries of the river. The Obs come close to neighboring river basins; so, for example, the right tributaries of the Ob - the Ket and Vakh rivers - come close to the left tributaries of the river. Yenisei; left tributaries of the river. Ob and tributaries of the river. Tobol close to the river basin. Ural and to the river basin. Kama.

The rivers of the West Siberian Plain have huge energy resources: the Ob annually discharges 394 billion tons of electricity. m 3 waters in the Kara Sea. This corresponds approximately to the amount of water in 14 rivers such as the Don. On the Ob, above the city of Novosibirsk, the Novosibirsk hydroelectric power station was built. On the river Irtysh built a cascade of energy nodes. Rocky narrow valley Irtysh from the mouth of the river. Bukhtarma to the city of Ust-Kamenogorsk is the most favorable for the construction of hydroelectric power stations. Ust-Kamenogorsk HPP and Bukhtarma HPP were built.

Ichthyofauna of the river. Both are varied. In some parts of the river, various fish are of commercial importance. In the upper reaches, before the confluence of the river. Chulym, commercial fish are found: from sturgeons - sturgeon, sterlet; from salmon - nelma, cheese, muksun. Along the tributaries they catch Siberian roach (from cyprinids), crucian carp, pike, perch, burbot. In the middle reaches of the river Ob, where in winter the deadly phenomena are strongly developed, fish demanding oxygen leave. Fishes that live in rivers all the time are of commercial importance - roach (chebak), dace, ide, crucian carp, pike, perch. In summer, on the way to spawning or feeding, they come here: sturgeon, nelma, cheese, muksun. In the lower reaches of the river - up to the Gulf of Ob - there are: sturgeon, nelma, cheese, pizhyan, muksun, etc.

In the southern part of the West Siberian Plain there are many mineral lakes with large amounts of salt, soda, mirabilite and other chemical products.

Lakes are the most important source of water supply in many arid regions of the West Siberian Plain. But sharp fluctuations in the level of lakes, especially those with poor groundwater, affect their mineralization: in autumn, the volume of water in lakes usually decreases sharply, the water becomes bitter-salty and, therefore, cannot be used for drinking. In order to reduce evaporation and maintain a sufficient volume of water in lakes, they resort to embankment of lake basins, afforestation, snow retention in watersheds,

increasing catchment areas under favorable topographical conditions by connecting several isolated catchment basins.

Many lakes, especially Chany, Sartlan, Ubinskoye and others, are of fishing importance. In the lakes are found: perch, Siberian roach, pike, crucian carp, Balkhash carp, bream are bred. In the reed and sedge thickets of lakes from spring to autumn, a large number of waterfowl find refuge.

On the lakes of Baraba, large numbers of geese and ducks are harvested annually. In 1935, the muskrat was released into the lakes of the western part of Baraba. She acclimatized and settled widely.

geographic zones. On the vast West Siberian Plain, the latitudinal zonality of all components of nature that were formed in the post-glacial period, namely, climate, soils, vegetation, waters, and wildlife, is extremely clearly manifested. Their combination, interconnection and interdependence create latitudinal geographical zones: tundra and forest-tundra, taiga, forest-steppe and steppe.

The natural zones of the West Siberian Plain but the area occupied are unequal (see Table 26).

The table shows that the dominant position is occupied by the forest zone, and the smallest area is occupied by the forest tundra.

The natural zones of the West Siberian Plain are part of the geographical zones stretching across the entire territory of the Soviet Union from west to east, and retain their common features. But due to the local West Siberian natural conditions (plains, widely developed clay-sand deposits with a horizontal occurrence, a climate with transitional features between the moderately continental Russian Plain and continental Siberia, severe swampiness, a special history of the development of the territory in pre-glacial and glacial times, etc.) zones of the West Siberian lowland have their own characteristics. So, for example, the subzone of mixed forests of the Russian Plain extends eastward only to the Urals. The oak forest-steppe of the Russian Plain does not cross the Urals. The West Siberian region is characterized by aspen-birch forest-steppe.

Tundra and forest tundra. From the shores of the Kara Sea and almost to the Arctic Circle, between the eastern slope of the Urals and the lower reaches of the river. Yenisei, tundra and forest-tundra stretch. They occupy all the northern peninsulas (Yamal, Tazovsky and Gydansky) and a narrow strip of the mainland part of the plain.

The southern border of the tundra near the Ob and Taz bays runs approximately at 67°N. sh.; R. It crosses the Yenisei to the north of the city of Dudinka. The forest-tundra stretches in a narrow strip: in the region of the Gulf of Ob, its southern border goes south of the Arctic Circle, and to the east of the Gulf of Ob, along the Arctic Circle; behind the river valley The Taza border runs north of the Arctic Circle.

The main rocks that make up the peninsulas and the islands adjacent to them - Bely, Sibiryakova, Oleniy and others - are Quaternary - glacial and marine. They lie on the uneven surface of the pre-Quaternary relief and consist of clay and sand with occasional boulders. The thickness of these deposits in depressions of the ancient relief reaches 70-80 m, and sometimes more.

A marine primary plain stretches along the coast with a width of 20-100 km. It is a series of sea terraces with different heights. There is an increase in the heights of the terraces to the south, which is apparently due to Quaternary uplifts. The surface of the terraces is flat, with scattered saucer-shaped lakes with a depth of 3-4 m. On the surface of sea terraces there are dunes 7-8 m, blowing pits. The formation of eolian forms is favored by: 1) the presence of loose sea sands not fixed by vegetation; 2) low moisture content of sands in spring and summer; 3) strong wind activity.

The inner parts of the peninsulas have a hilly moraine surface with numerous small lakes.

The formation of the modern relief of the peninsulas is greatly influenced by permafrost. The thickness of the active layer in many areas reaches only 0.5-0.3 m. Therefore, erosional activity, especially deep, is weakened. Erosive activity is hindered by prolonged drizzling rains and numerous lakes, which act as flow regulators throughout the warm season. Therefore, floods on the rivers do not occur. However, erosion activity is currently one of the main factors transforming the original relief of the moraine-hilly and marine plains: wide river valleys, many meanders, young ravines along ledges of terraces, valleys and lake basins. Slopes change as a result of deluvial washout, solifluction and landslides.

In areas of permafrost development, thermokarst phenomena are common, as a result of which sinkholes, funnels, saucers, and lakes are formed. The emergence of thermokarst forms is still taking place; this is evidenced by trunks and stumps immersed in lakes, flooded trees and shrubs, cracks in the ground. Spotted tundras form on even flat watersheds or on slightly sloping slopes. Spots devoid of vegetation reach in diameter from 1-2 to 30-50 m.

The harsh climate of the tundra is due to its northern position, the influence of the cold Kara Sea and the entire Arctic basin, as well as the lively cyclonic activity and cooling in the winter period of the neighboring territory - the region of the Asian anticyclone.

Winter in the West Siberian tundra is more severe than in Europe, but less frosty than east of the river. Yenisei. Average January temperatures are -20-30°. Winter types of weather prevail from mid-October to early May. The average monthly wind speed in the tundra is -7-9 m/s, maximum - 40 m/s, that at low temperatures, sometimes reaching -52 °, creates a great severity of the weather. The snow cover lies for about 9 months (from half of October to half of June). Under the action of strong winds, snow is blown and therefore its thickness is uneven. The weather depends on the frequent passage of cyclones and on the intrusions of arctic air masses from the Kara Sea and polar continental air masses from Central Siberia.

In summer, Arctic air invades the entire territory, but the process of its transformation is still weakly expressed. Summer in the tundra is cool, with frosts and snowfalls. The average July temperature is about +4, +10°; maximum +20, +22° (Tombey), to the south it reaches +26, +30° (New Port); the temperature in summer drops to -3, -6°. In the forest-tundra, the average July temperatures are +12, +14°. The sum of temperatures above 10° on the southern border of the tundra is 700-750°.

Annual rainfall - from 230 mm in the northern part up to 300 mm in southern part. The maximum precipitation falls in summer, mainly in the form of long-term drizzling rains; showers with thunderstorms are rare. Due to the lack of heat, frequent precipitation, low evaporation and the presence of permafrost in some places, the soil is heavily swamped, and the relative humidity of the air is very high. Evaporation on the coast - 150 mm, and on the southern border of the forest-tundra about 250 mm. The tundra and forest-tundra zone is characterized by an excessively humid climate.

Groundwater is shallow, which contributes to the waterlogging of the territory and the poor development of soil aeration. For most of the year, groundwater is frozen.

Soil formation occurs in the parent rocks of the Quaternary age - clayey-sandy deposits of glacial and marine origin. Soils are formed under conditions of low air and soil temperatures, low rainfall, insignificant drainage of the territory and lack of oxygen. All these conditions lead to the development of soils of the gley-bog type. However, the combination of local components of nature creates diversity in the formation of the soil cover. The most common are tundra gley and peat-bog soils, which form under conditions of strong moisture. On the sands, where there is no permafrost or it lies at great depths, there is no waterlogging and weakly podzolic soils develop. In the forest-tundra, the process of formation of podzolic soils is more pronounced: they are formed not only on sands, but also on loams. Therefore, the main types of forest-tundra soils are gley-podzolic.

When moving from north to south within the tundra, there is a change in climate, soil formation and vegetation cover.

BN Gorodkov identified the following subzones of the tundra: 1) the arctic tundra; 2) typical tundra; 3) southern tundra; 4) forest tundra.

The Arctic tundra occupies the northern parts of the Yamal and Gydan Peninsulas. The arctic tundra is dominated by patchy tundra. Its vegetation is very sparse and settles only in hollows and cracks surrounding bare patches of soil. Sphagnum mosses and shrubs are completely absent in the vegetation cover. The latter occasionally come from the south along the river valleys. The species composition is poor; the most typical species are: foxtail( Alopecurus alpinus), sedge ( carex rigida), moss ( Polytrichum strictum), sorrel ( Oxyria digyna), meadow grass ( Deschampsia arctica).

Typical tundra occupies the middle and southern parts of the Yamal and Gydan peninsulas and the northern part of the Tazovsky. The southern border of the tundra passes north of the Arctic Circle. The vegetation of a typical tundra is varied. Mosses, lichens, forbs and shrubs are widespread: they are found not only along river valleys, but also on watersheds.

The vegetation of a typical tundra forms three tiers: the upper one is shrubby, consisting of birch( Betuladad), wild rosemary ( Ledumpalustre), shrub willow( Salix glauca, S. pulchra), blueberries ( Vaccinium uliginosum); medium - herbaceous - from sedges(Ca rex rigida), dropsy ( Empetrum nigrum), cranberries ( Oxycoccos microcarpa O. palustris), partridge grass (Dryas octopetala), bluegrass (Roa arctica), cotton grass ( Eriophorum vaginatum). Sedges predominate among other plants; the lower tier - lshpaynikovo-moss. It consists of lichens: alectoria( Alectoria), cetraria ( Cetraria), reindeer moss ( Cladonia rangiferina), mosses - hypnum and sphagnum( Sphagnum lenense).

Typical tundra is different in some areas: moss tundra is formed on moist clay soils. Lichen tundra develops on elevated loamy and sandy areas. In places of strong wind activity, there are small areas of patchy clay tundra. In spring and summer, moss tundras are good grazing grounds for deer, which feed on cotton grass, shrub leaves, and various grasses. In the ravines, on the slopes of the southern exposure, tundra meadows develop, consisting of forbs. The meadows are used as summer pastures for deer.

Riverside thickets of willow bushes move north along the river valleys. Compared to other plant groups, shrubs develop under conditions of less waterlogging, thicker snow cover, and faster and deeper thawing of the active soil layer.

In the south of the typical tundra, shrubs begin to predominate in the vegetation cover. They form dense thickets of birch and willow up to 1.5-3 m not only along river valleys, but also on watersheds, among moss and lichen tundra. The wide development of shrub groups in the more southern parts of the tundra is explained by the weakened activity of the wind in winter, thicker snow cover and more precipitation.

The tundra is gradually replaced by the forest tundra. In the northern part of the forest-tundra, small areas of light forests and crooked forests appear, which increase in the south and pass into the taiga. In the forest-tundra, trees grow at some distance from each other; between them are areas of shrub, moss, lichen, and sometimes spotted tundra. The most favorable areas for woody vegetation are sandy areas, protected from wind activity and well warmed up. The forests consist of larch and spruce. Under the forest canopy, dwarf birch and shrub alder are often found. The ground cover consists of sphagnum mosses that form peat bogs with a hilly surface. In dry sandy places, where there is a fairly thick snow cover, the soil is covered with lichens, mainly reindeer moss. The main soil types are gley-podzolic.

The slopes of river valleys and terraces are covered in summer with juicy variegated meadows, consisting of buttercup, wisps, valerian and berries. The meadows are an excellent pasture for deer in summer and autumn, and a habitat for many animals and birds.

For the tundra of the West Siberian Plain, the most typical of the animal world is the domestic reindeer. He gets his food all year round: reindeer moss, or reindeer moss, berries, mushrooms, leaves and grass. Large reindeer-breeding state farms and collective farms have been set up in the tundra, provided with pastures and veterinary and zootechnical stations. The enemies of reindeer herds are wolves that live in the forest-tundra and tundra.

The polar fox, or polar fox, lives in the tundra and forest-tundra. It feeds on a variety of foods, but the main food is lemmings, or lemmings. In spring, it destroys bird nests, eating eggs and young chicks.

Lemming is a small tundra rodent. It feeds on the bark of willows and dwarf birches, plant foliage. It serves as food for many mammals and raptors. In the tundra of Western Siberia, there are two types of lemmings: Ob and hoofed.

Along the river valleys of the forest-tundra, in forests and thickets of bushes, there are forest animals: squirrel, hare, fox, wolverine, which penetrate far to the north - into the tundra.

There are especially many waterfowl in the tundra, of which geese, ducks, swans, and loons are the most typical of its landscape. The white partridge lives in the tundra all year round. The white owl in the tundra is a diurnal bird.

In winter, the tundra is poor in birds: few of them remain to live in difficult climatic conditions. Geese, ducks, swans, the red-throated goose fly south, nesting only in the tundra and forest-tundra, from the river. Ob to river Yenisei. The peregrine falcon is also a migratory bird, which feeds on waterfowl. Migratory birds spend no more than 2-4.5 months a year in the north.

For about 9 months the tundra is covered with snow. The thickness of the snow cover in some places reaches 90-100 cm. Arctic fox, ptarmigan, and lemmings burrow into loose, fine snow. Compacted snow contributes to the easy movement of tundra animals: for example, the arctic fox walks freely on the crust. In the white partridge, the claws lengthen and the fingers by autumn are covered with a dense cover of dense flexible feathers, forming a wide elastic surface. Because of this, the increased supporting surface of the paw allows it to run through the snow without sinking deep. With loose deep snow, the white partridge plunges into it up to the abdomen and can only wander around the bushes with great difficulty. Territories with little snow are the most favorable for deer, as they freely get reindeer moss from under the snow.

The most important economic problem in the development of the tundra is the development of vegetable growing. To do this, it is necessary to improve the soil by draining it, improving aeration, lowering the level of permafrost, protecting soil from freezing by accumulating snow in the fields, and introducing manure into the soil. Frost-resistant crops can grow in the tundra.

Forest zone. Most of the area of the West Siberian Plain is covered with forests - taiga. The southern border of the forest zone approximately coincides with the parallel of 56°N. sh.

The relief of the taiga zone was created by the accumulative activity of continental glaciation, melted glacial and surface waters. The southern boundaries of the distribution of ice sheets passed within the forest zone. Therefore, to the north of them, the dominant type of relief is accumulative glacial plains, altered by the activity of melted glacial waters of the retreating maximum glacier and partially melted glacial waters of the last glaciations.

The area of glacial plains is about 1/4 of the area of the entire West Siberian Plain. The surface is composed of Quaternary deposits - glacial, water-glacial, alluvial, lacustrine. Their power reaches sometimes more than 100m.

The forest zone is included in the West Siberian continental climatic region. Continental temperate air dominates all year round.

The winter type of weather is predominantly anticyclonic and is associated with the Asian anticyclone, but passing cyclones create unstable weather. Winters are long, with strong winds, frequent snowstorms and rare thaws. Average January temperature: -15° in the southwest and -26° in the east and northeast. Frosts reach -60° in some areas. With the arrival of a cyclone, temperatures can change dramatically. Snow cover lasts about 150 days in the south of the zone and 200 days in the northeast. The height of the snow cover by the end of February reaches 20-30 cm in the south and 80 cm in the north-east. Snow cover lies from mid-October to mid-May.

In summer, air from the north flows into the forest zone of the West Siberian Plain. On the way to the south, it transforms and, therefore, in the northern regions it is still quite humid, while in the southern regions it warms up and moves further and further away from the saturation point. Summer throughout the territory is relatively short, but warm. Average July temperatures are +17.8° (Tobolsk), +20.4° (Tselinograd) and +19° (Novosibirsk).

The amount of precipitation - 400-500 mm, maximum - in the summer. Over the entire territory, at the same latitudes, more precipitation falls in the European part of the Soviet Union than in Western Siberia.

Long winters with low temperatures in the northern part of the plain contribute to the existence of permafrost, the southern border runs from west to east approximately within 61-62 ° N. sh. Under the channels, the roof of frozen soil is much lower than on the watersheds, and under the Ob and Yenisei rivers, it was not found at all.

Groundwater is fresh and occurs close to the surface (at a depth of 3-5 to 12-15 m). Extensive sphagnum swamps are developed on the watersheds. The rivers have slight slopes, flow slowly in wide, strongly meandering channels. This is associated with weak mineralization of river waters (50-150 mg/l) and poor aeration of stagnant waters. There are dams in the rivers. The essence of the deadly phenomena is as follows: groundwater and swamp water, containing a small amount of oxygen and a lot of organic substances, enters the Ob and its tributaries. With the formation of ice on the rivers, the access of oxygen from the air stops, and the swamp water continues to flow into the rivers and absorb oxygen. This leads to oxygen deficiency and causes mass death of fish. The Zamora zone occupies an area of about 1,060,000 km 2. To the north, the dead zone advances to the lower reaches of the river. Ob and extends even to the Gulf of Ob.

Soils. The formation of soils occurs in a flat, heavily swampy terrain, covered with taiga vegetation. The parent rocks are diverse: glacial, fluvioglacial, lacustrine and eluvial-deluvial consist of sandy, sandy-argillaceous and boulderless deposits, as well as loess-like loams. The forest zone of the plain is characterized by podzolic, podzolic-bog and peat-bog soils.

Vegetation. Within the forest zone, when moving from north to south, the following subzones are distinguished.

1. Subzone of pre-tundra larch woodlands. This subzone stretches in a narrow strip from the Cis-Urals to the river. Yenisei, expanding in the east.

The strip of light forest consists of Siberian larch( Larix sibirica) spruce ( Picea obovata) and cedar ( Pinus sibirica), especially in the southern part of the subzone, but spruce is more common in the west than in the east. The forests are sparse, treeless areas are occupied by small swamps and tundra formations.

2. The subzone of the northern taiga is characterized by an open forest stand and a wide distribution of flat-hummocky sphagnum bogs. Forests consist of larch with an admixture of spruce, birch, and cedar. In the northern part of the subzone, in some places they are clean, without impurities. Larch forests are widespread along the sands, and to the south, pine forests settle on the sands along river valleys and watersheds. The ground cover of forests is formed by lichens and mosses. Of the shrubs and herbs are typical: bearberry, shiksha, lingonberry, sedge (Carex globularis ) , horsetail ( Equisetum sylvaticum, E. pratense); the undergrowth consists of dwarf birch, rosemary and blueberry. These forests occupy large areas closer to the Yenisei and Ob rivers. Swamps dominate in the middle part of the northern taiga.

3. Middle taiga subzone. Dark coniferous forests are formed by spruce and cedar with an admixture of larch and fir( Abies sibirica). Larch is found throughout the zone, but in small areas. Birch is more widespread than in the northern taiga, which often grows together with aspen, forming birch-aspen forests. The dark coniferous taiga is characterized by great closeness and gloominess. Dark coniferous forests are unevenly distributed within the subzone. The most significant arrays are concentrated in the middle and eastern parts. To the west of the Ob and Irtysh rivers, pine forests with sphagnum bogs predominate. Spruce and cedar forests are found mainly in river valleys. They have a diverse grass cover and dense thickets of bushes from Siberian svidina (Cornus tatarica ) , bird cherry, viburnum, honeysuckle ( Lonicera altaica).

4. Southern taiga. For the southern taiga, the dominant species is fir; birch and aspen forests are widespread. In the west, in the southern taiga forests, there is a linden( Tilia sibirica) with a herbal companion - sleepweed( Aegopodium podagraria). The middle and southern taiga are distinguished under the name Urmano-marshy.

5. The subzone of deciduous forests is formed mainly by downy birch( Betula pubescens) and warty (AT. verrucosa) and aspen ( Populus tremula), alternating with grass and sphagnum bogs, with meadows and pine forests. Spruce and fir enter the subzone of deciduous forests. Birch and aspen forests are confined to soddy-podzolic soils, leached chernozems and solods.

Pine forests grow on the sands; they occupy the largest area in the river basin. Tobol.

The subzone of deciduous forests gradually turns into forest-steppe. In the west (west of the Ishim River), the forest-steppe is more forested than in the east. This is apparently due to the high salinity of the soils of its central and eastern parts.

The fauna of the West Siberian taiga has many common species with the European taiga. Everywhere in the taiga live: brown bear, lynx, wolverine, squirrel, ermine. Of the birds - capercaillie, black grouse. The distribution of many animal species is limited to the Ob and Yenisei valleys. For example, the roller, the European hedgehog do not penetrate east further than the river. Obi; beyond the Yenisei, the great snipe and the corncrake do not pass from the birds.

Riverside taiga and secondary aspen-birch forests are rich in animals. Typical inhabitants of these forests are elk, white hare, ermine, Siberian weasel. Previously, the beaver was found in large numbers in Western Siberia, but at present it has been preserved only along the left tributaries of the Ob. A beaver reserve was organized here along the rivers Konda and Malaya Sosva. Muskrat (musk rat) is successfully bred in reservoirs. American mink was released in many places in the West Siberian taiga.

Birds nest in the taiga. Cedar forests are a favorite place for nutcrackers; in the larch forests, the Siberian crossbill is more common; in the spruce forests, the three-toed woodpecker taps. There are few songbirds in the taiga, so it is often said that the taiga is silent. The most diverse bird kingdom is on birch-aspen burnt areas and on the banks of rivers; here you can meet waxwing, finches, long-tailed bullfinch, rubythroat nightingale. On reservoirs - geese, ducks, sandpipers; in the moss swamps far to the south, almost to the forest-steppe, the white partridge comes. Some birds arrive in the West Siberian taiga from the southeast. Many of them winter in China, Indochina, on the Sunda Islands. Long-tailed bullfinch, rubythroat nightingale, etc. fly there for the winter.

Commercial value are: squirrel, fox, ermine, weasels. Of the birds - hazel grouse, black grouse, capercaillie and white partridge.

Forest-steppe and steppe The West Siberian Plain was formed in special physical and geographical conditions, namely: on a flat, poorly drained terrain, on saline parent rocks, at a considerable distance from the oceans, with a more continental climate. Therefore, their appearance differs sharply from the forest-steppe and steppe of the Russian Plain.

The West Siberian forest-steppe stretches in a narrow strip from the Urals to the foothills of the Salair Ridge and Altai.

This is the southern part of the marine Tertiary plain, covered with loose Quaternary deposits, ancient alluvial and fluvioglacial.

sands, deluvial loess-like loams, loess and modern lacustrine and alluvial sands and clays.

Bedrocks - tertiary clays, sands, loams - are exposed by river valleys and come out in natural outcrops in bedrock banks or at the base of terraces in the western, southern and southeastern parts of the steppe zone, where tertiary rocks are elevated and form plateaus or inclined plains.

The modern relief of the forest-steppe and steppe was greatly influenced by ancient streams, which formed wide ravines of runoff crossing the Ob plateau, the Kulunda, Baraba lowlands and other territories. Ancient hollows are directed from the northeast to the southwest. The bottoms of the hollows are flat, composed of loose deposits. The interfluves between the hollows of the runoff are elongated in the same direction as the hollows, and are called "manes". Modern rivers flow through the hollows, which flow either into the Ob and Irtysh or into lakes, or are lost in the steppe. All these landforms are clearly visible from an airplane, especially in early spring, when snow spots still remain in them, and the watershed spaces have already been freed from snow. One of the features of the steppe and forest-steppe zones of Western Siberia is the abundance of lake basins. They are common on flat watersheds and in river valleys. The largest of them are the lakes of the Baraba steppe, where the largest shallow lake is located. Chany and Ubinskoye lake. Of the lakes of the Kulunda steppe, the largest is Kulunda. The lakes of the Ishim steppe are mostly shallow. The large lakes are Selettengiz. There are many small lakes on the Ishim-Irtysh sloping plain and the Ishim Upland.

Thousands of lakes occupy depressions in ancient hollows; they are the remains of former river channels. The shores of such lakes are low, often swampy or overgrown with pine forests. The lakes are fed by melt and rain water formed as a result of surface runoff. For many reservoirs, especially large ones, ground feeding is also essential.

Lakes periodically change their level, and, consequently, their outlines and their water supply: they dry up, then refill with water 1 . The change in the level of lakes is associated with fluctuations in climatic conditions: with the ratio of precipitation and evaporation. Some influence on the change in the level of lakes is also exerted by human activity during the construction of dams, laying ditches, burning birch chops, and mowing reed beds along the banks. So, for example, in the Baraba, Kulunda and Ishim steppes, after fires, new lakes arose up to 1.5-2 m. After mowing the coastal thickets of reeds and reeds, some of the freshwater lakes in the Kulunda steppe turned into saline ones, since in winter snowdrifts stopped accumulating on them, which led to a sharp reduction in one of their most important sources of nutrition.

Over the past 250 years (with XVII to the middle XXc.) seven complete cycles of fluctuations in the levels of steppe lakes have been established, usually lasting from 20 to 47 years. Based on the analysis of atmospheric precipitation and temperature regime, cycles of high and low activity of precipitation, warm and cold periods were revealed.

Thus, the dependence of fluctuations in the level of lakes on fluctuations in atmospheric precipitation and air temperature is outlined.

It is assumed that fluctuations in the levels of individual lakes are associated with neotectonic movements. Fluctuations in the levels of the lakes of the Chany group were repeatedly recorded.

The steppe and forest-steppe are dominated by lakes containing brackish water (Chany, Ubinskoye, and others). Lakes are divided according to their chemical composition into three types: hydrocarbonate (soda), chloride (actually salty) and sulfate (bitter-salty). In terms of reserves of salt, soda and mirabilite, the lakes of Western Siberia occupy one of the first places in the USSR. Kulunda lakes are especially rich in salts.

The climate of the forest-steppe and steppe of the West Siberian Plain differs from the climate of the forest-steppe and steppe of the Russian Plain by greater continentality, manifested in an increase in the annual amplitude of air temperature and in a decrease in the amount of precipitation and the number of days with precipitation.

Winter is long and cold: the average January temperature in the forest-steppe drops to -17, -20°, sometimes frosts reach -50°; in the steppes, the average January temperatures are -15, -16°, frosts also reach -45, -50°

The least amount of precipitation falls in winter. The first half of winter is characterized by snowfalls and strong winds, the speed of which in the open steppes reaches 15 m/sec. The second half of winter is dry, with weakened wind activity. The snow cover has a small (40-30 cm) power and is unevenly distributed over the surface of the forest-steppe and steppe.

In the spring, insolation and air temperature increase rapidly. The snow cover melts in April. Snow melts very quickly, in the steppe - sometimes in one week.

The average air temperature in the steppe in May reaches + 15°, and the highest - up to + 35°. However, in the first half of May there are severe frosts and snow storms. After the snow melts, the temperature rises very quickly: already in the first decade of May, the average daily temperature exceeds +10°C.

In the formation of dry spring weather, dry winds are of great importance, which are most frequent in May. During dry winds, the temperature

air reaches +30°, relative humidity below 15%. Dry winds are formed during the southern winds that occur on the western outskirts of the Siberian anticyclones.

Summer in the forest-steppe and steppe is hot and dry with frequent winds and dry weather types. In the forest-steppe, the average temperature is about +19°, in the steppe it rises to 22-24°. Relative humidity reaches 45-55% in the steppe, and up to 65-70% in the forest-steppe.

Droughts and dry winds are more common in the first half of summer. During summer dry winds, the air temperature can rise to +35, +40°, and the relative humidity reaches about 20%. Droughts and dry winds are caused by the penetration and intensive heating of the Arctic air masses and the intrusion of hot and dry air from Central Asia. Every year, especially in dry years, dust storms occur in the steppes from April to October. Most of them are in May and early June. More than half of the annual precipitation falls during the summer.

The first half of autumn is often warm. In September the air temperature can reach +30°; however, there are also frosts. A rapid drop in temperature is observed from October to November. Precipitation intensifies in October. Moisture accumulates in the soil in autumn, as evaporation is negligible at this time. In the northern part of the steppe, snow cover appears at the end of October. From November, persistent frosts set in.

The history of the formation of the forest-steppe and steppe of the West Siberian Plain in the Tertiary and Quaternary periods differed sharply from the history of the formation of the steppe and forest-steppe of the Russian Plain. Therefore, the modern appearance of the forest-steppe and steppe of Western Siberia has its own characteristics, which are most clearly manifested in the relief, soils and vegetation. The modern continental climate contributes to the development of the more arid steppes of the West Siberian Plain compared to the East European Plain and enhances their differences.

The forest-steppe and steppe of the West Siberian Plain is dominated by primary flat, poorly drained plains covered with extensive swamps, numerous fresh and salt lakes, saucers, wide hollows and manes.

The ravine-gully network is less developed than on the Russian Plain. However, the manifestation of ravine activity is observed in all natural zones of the West Siberian Plain, and especially on the sloping plains and plateaus adjacent to the Urals and Altai, and along the valleys of the Ob and Irtysh rivers. In the steppes, nivation ravines are widely developed, the formation of which is due to the accumulation of snow under the action of strong winds near various natural barriers, especially in gullies and ravines. Soil-forming processes occur in a geologically young, poorly drained area with saline soil, under conditions of insufficient moisture. The zonal soils of the forest-steppe of Western Siberia are meadow-chernozem, leached and podzolized chernozems.

Solonchaks, solonetzes and solods are widespread; their formation is associated with shallow groundwater, soil salinity, and increased evaporation. They are confined to depressions. Due to the increase in humidity, the process of soil leaching increased, which led to the destruction of solonetzes and the emergence of solods.

In the steppe zone, southern and ordinary chernozems are developed, which gradually turn into dark chestnut soils with a humus horizon of up to 50 m and with a humus content in the range of 3-4%. Dark chestnut soils have weak signs of alkalinity, an insignificant depth of effervescence and a large amount of gypsum at a depth of 1m.

The forest-steppe of the West Siberian Plain is called the birch forest-steppe. From the northern part of the forest-steppe, the forest cover of the territory is about 45-60%. Isolated birch forests are called birch groves. The pegs consist of downy birch with an admixture of aspen, warty birch and willow in the undergrowth. The grass cover in the pegs is formed by steppe and forest species. Bone is typical of the forest( Rubus saxatilis), bought ( Polygonatum officinale) ; from shrubs - currant ( Ribes nigrum). Of the conifers in the forest-steppe, pine is common. Pine forests occupy sandy and sandy loamy areas and go along the floodplain terraces of the valleys to the south to the steppe zone. Under the canopy of pines, taiga plant groups are moving south - satellites of pines: sphagnum bogs, on which wintergreens, lingonberries, blueberries, cranberries, sundews, cotton grass, sedges and orchids grow. On the most elevated, dry places, white moss forests with a ground cover of reindeer lichen (moss moss) are developed. The soil cover of pine forests is very diverse and consists of podzols, dark-colored solod peaty soils and solonchaks. But at the same time, steppe species (fescue and steppe timothy grass) are common in the grass cover of southern pine forests.

The steppe areas have a dense herbaceous cover, consisting of typical meadow rhizomatous grasses: reed grass, meadow bluegrass, steppe timothy grass. From legumes are often found: clover and peas, and from Compositae - meadowsweet( Filipendula hexapetala), solonchak forms appear on solonchaks.

When moving south, the grass cover of the steppes thins out, the species composition changes - steppe species begin to predominate, while meadow and forest species are noticeably reduced. Sod xerophytes predominate among cereals: fescue( Festuca sulcata) and thin-legged ( Koeleria gracilis), feather grasses appear( Stipa rubens, St. capillata). Of the herbs, alfalfa is the most typical( Medicago falcata) and sainfoin ( Onobrychis arenaria). Salt marsh plants begin to meet more often: licorice, saltwort, large plantain, astragalus. There are fewer birch groves, and the forest cover of the territory is only 20-45%.

In the West Siberian forest-steppe, as already noted, swampy areas, which are called borrowings, are widespread. Zaimishchas are covered with marsh vegetation: sedge, reeds, reeds, cattails. They occupy low interfluve spaces and are the final stage of overgrowing water bodies. Loans are especially plentiful in the Baraba steppe. In addition, in the West Siberian forest-steppe, moss-sphagnum bogs are common, overgrown with a rare, oppressed pine. They are called ryams. Pine forests, occupants and ryams in the conditions of the modern dry climate should be considered intrazonal plant groups, possibly formed during the Ice Age.

The steppes occupy the extreme south of the West Siberian Plain. Within the steppe zone of Western Siberia, two subzones are distinguished: the northern - feather grass-forb chernozem steppe and the southern - feather grass-fescue chestnut steppe. The composition of the northern steppes is dominated by xerophytic narrow-leaved grasses: reddish feather grass( Stipa rubens), hairy, fescue, thin-legged, desert sheep ( Auenastrum desertorum), timothy. Forbs are less abundant than in the steppes of the forest-steppe, and consist of yellow alfalfa, bedstraw, speedwell, sleep-grass, cinquefoil, wormwood.

In terms of species composition and aspect, the West Siberian steppes differ from the colorful European steppes of this subzone. In the Siberian steppes there are no sage, raven, blush, clovers( Trifolium montanum T. alpestre), but xerophytic forbs predominate.

Sod grasses dominate in the southern steppes of the West Siberian Plain: fescue, thin-legged and hairy feather grass. Abundant rhizomatous steppe sedge( Carex sypina). Of the forbs, xerophytic species predominate, for example: wormwood ( Artemisia glauca, Alatifolia), onion ( Allium lineare) , Adonis ( Adonis wolgensis), gerbils ( Arenaria graminifolia); many Siberian forms that do not enter the European steppe: iris ( Iris scariosa), goniolimon ( Goniolimon speciogum) and etc.

The grass cover is sparse, and the turfiness of the steppes reaches 60-40%. On the shores of lakes, on salt licks, solonetsous species grow, for example, sea wormwood. In depressions with close occurrence of groundwater and along the shores of salt lakes, solonchaks with typical halophyte vegetation predominate: soleros, solonchak barley, licorice.

In the steppes along the river valleys, hollows of the ancient runoff, ravines there are thickets of willow, birch, along the sands - patches of pine forests (green mosses, lingonberries and white mosses with a large number of steppe species). So, for example, in the valley of the river. On the sandy right-bank terrace of the Irtysh, extensive pine forests stretch from the city of Semipalatinsk to the city of Pavlodar.

The floodplains of large rivers are covered with meadow vegetation, which forms a dense succulent herbage of wheatgrass, steppe alfalfa, water-loving; closer to the water, marsh associations of reeds and sedges dominate. Wet floodplain meadows are an example of a sharp contrast with dry feather-grass-fescue steppes, which quickly burn out in summer.

The northern and southern steppes are used as pastures and hayfields. Most of their territory is plowed up.

The most significant natural difficulties for agriculture in the steppe zone of the West Siberian Plain are the dryness of its climate and the penetration of dry winds.

Forest plantations and belt pine forests contribute to an increase in the yield of grain crops, since the humidity of the air and soil increases near them, and the amount of precipitation increases compared to the treeless steppe. In ribbon pine forests and forest belts, in addition to the main species, pine, pedunculate oak, small-leaved linden, Amur larch, Amur velvet, and in the undergrowth - Amur acacia and bird cherry Maak are planted.

The fauna of the forest-steppe is more diverse than the fauna of the steppe, since the latter is characterized by the uniformity of ecological conditions over vast areas. The fauna of the forest-steppe includes forest and steppe species. Along the pegs and ribbon forests, the northern (taiga) elements penetrate to the south even into the feather grass-fescue steppes, and along the meadow-steppe areas, the steppe elements enter the northern part of the forest-steppe; for example, in the Kulunda pine forests live along with steppe species - garden oatmeal, field pipit, upland jerboa - taiga animal species: squirrel, flying squirrel, capercaillie.

In the forest-steppe and steppe there are animals that live in the tundra. They are relics of the Ice Age. The white partridge is found even in the steppes of Kazakhstan up to 50.5 ° N. sh., its nesting sites are known on the lake. Vats. It never penetrates as far to the south as in the West Siberian steppes. On the lakes of the forest-steppe and the steppe, there is a gull-gull, typical of the tundra zone of Taimyr.

The fauna of the forest-steppe and steppe has many similarities in terms of the composition of the fauna and its origin with the fauna of the European steppe and forest-steppe, but the geographical features of the West Siberian Plain predetermined its difference from neighboring territories.

Of the mammals in the forest-steppe and steppe, there are many rodents: voles, steppe pied, earth hare - the largest of the jerboas ( Allactaga gaculus); Djungarian hamster, red-cheeked ground squirrel are often found ( Citellus erythrogenus). The steppe is characterized by a small, or gray, ground squirrel, marmot (baybak).

Of the carnivores in the steppe and forest-steppe live: wolf, fox, steppe polecat. A small fox, a corsac fox, comes into the steppe from the south. In the forests of the forest-steppe, typical taiga species are found: Siberian weasel, weasel, ermine.

AT XIV- XIXcenturies in the steppes of the West Siberian Plain there were such animals that are currently distributed only in the forest zone. For example, in the valleys of the Tobol, Ishim and Irtysh rivers, south of the city of Petropavlovsk and Lake. Chany, there was a beaver, and a bear was found near the city of Kustanai and between the cities of Petropavlovsk and Tselinograd.

Among the birds of the forest-steppe there are many European forms (common bunting, oriole, chaffinch). In the steppe areas, the common and Siberian larks are numerous, and the little bustard and bustard are occasionally found. In the southern steppes there are more of them: there are four species of larks (the small, or gray, lark penetrates from the desert into the steppe). Demoiselle crane and steppe eagle are found. Black grouse, gray and white partridge are the subject of winter fishing.

The fauna of insects is abundant, consisting of small locust grasshoppers, which sometimes damage crops, and “gnats” - mosquitoes, midges, horseflies.

There are four physical-geographic regions on the West Siberian Plain. Their occurrence is due to the history of the development of the territory in the Quaternary period and modern geographical zonality. Physical-geographical regions are located in the following order when moving from north to south: 1. Marine and moraine plains of the tundra and forest-tundra zones. 2. Moraine and outwash plains of the forest zone. 3. Alluvial-lacustrine and alluvial plains of the forest and forest-steppe zones. 4. The area of lacustrine-alluvial and erosion plains with a cover of loess-like rocks of the forest-steppe and steppe zones. Each of these areas has internal morphological, climatic and soil-vegetative differences, and therefore is divided into physiographic regions.

The West Siberian Plain belongs to the accumulative type and is one of the largest low-lying plains on the planet. Geographically, it belongs to the West Siberian plate. On its territory there are regions of the Russian Federation and the northern part of Kazakhstan. The tectonic structure of the West Siberian Plain is ambiguous and diverse.

Russia is located on the territory of Eurasia, the largest continent on the planet, which includes two parts of the world - Europe and Asia. The tectonic structure of the Ural Mountains separates the cardinal points. The map makes it possible to visually see the geological structure of the country. Tectonic zoning divides the territory of Russia into such geological elements as platforms and folded areas. The geological structure is directly related to the topography of the surface. Tectonic structures and landforms depend on which area they belong to.

Within Russia, several geological regions are distinguished. The tectonic structures of Russia are represented by platforms, folded belts and mountain systems. On the territory of the country, almost all areas have undergone folding processes.

The main platforms within the territory of the country are East European, Siberian, West Siberian, Pechora and Scythian. They, in turn, are divided into plateaus, lowlands and plains.

Relief of Western Siberia

The territory of Western Siberia gradually plunges from south to north. The relief of the territory is represented by a wide variety of its forms and is complex in origin. One of the important relief criteria is the difference in absolute elevations. On the West Siberian Plain, the difference in absolute marks is tens of meters.

The flat terrain and slight elevation changes are due to the small amplitude of plate movement. On the periphery of the plain, the maximum amplitude of uplifts reaches 100-150 meters. In the central and northern parts, the amplitude of subsidence is 100-150 meters. The tectonic structure of the Central Siberian Plateau and the West Siberian Plain was relatively calm in the Late Cenozoic.

The geographical structure of the West Siberian Plain

Geographically, in the north, the plain borders on the Kara Sea, in the south, the border runs along the north of Kazakhstan and captures a small part of it, in the west it is controlled by the Ural Mountains, in the east - by the Central Siberian Plateau. From north to south, the length of the plain is about 2500 km, the length from west to east varies from 800 to 1900 km. The area of the plain is about 3 million km2.

The relief of the plain is monotonous, almost even, occasionally the height of the relief reaches 100 meters above sea level. In its western, southern and northern parts, the height can reach up to 300 meters. The lowering of the territory occurs from south to north. In general, the tectonic structure of the West Siberian Plain is reflected in the terrain.

The main rivers flow through the territory of the plain - the Yenisei, the Ob, the Irtysh, there are lakes and swamps. The climate is continental.

Geological structure of the West Siberian Plain

The location of the West Siberian Plain is confined to the epihercynian plate of the same name. The basement rocks are highly dislocated and belong to the Paleozoic period of time. They are covered with a layer of marine and continental Mesozoic-Cenozoic deposits (sandstones, clays, etc.) more than 1000 meters thick. In the depressions of the foundation, this thickness reaches up to 3000-4000 meters. In the southern part of the plain, the youngest are observed - alluvial-lacustrine deposits, in the northern part there are more mature - glacial-marine deposits.

The tectonic structure of the West Siberian Plain includes a basement and a cover.

The foundation of the slab has the form of a depression with steep sides from the east and northeast and gentle sides from the south and west. The basement blocks belong to the pre-Paleozoic, Baikal, Caledonian and Hercynian times. The foundation is dissected by deep faults of different ages. The largest faults of submeridional strike are East Zauralsky and Omsk-Pursky. The map of tectonic structures shows that the basement surface of the slab has an Outer marginal belt and an Inner region. The entire surface of the foundation is complicated by a system of uplifts and depressions.

The cover is interbedded with coastal-continental and marine deposits with a thickness of 3000-4000 meters in the south and 7000-8000 meters in the north.

Central Siberian Plateau

The Central Siberian Plateau is located in the north of Eurasia. It is located between the West Siberian Plain in the west, the Central Yakut Plain in the east, the North Siberian Lowland in the north, the Baikal region, Transbaikalia and the Eastern Sayan Mountains in the south.

The tectonic structure of the Central Siberian Plateau is confined to the Siberian Platform. The composition of its sedimentary rocks corresponds to the period of the Paleozoic and Mesozoic. Characteristic rocks for it are bedded intrusions, which consist of traps and basalt covers.

The relief of the plateau consists of wide plateaus and ridges, at the same time there are valleys with steep slopes. The average height of the difference in the relief is 500-700 meters, but there are parts of the plateau, where the absolute mark rises above 1000 meters, such areas include the Angara-Lena plateau. One of the highest parts of the territory is the Putorana Plateau, its height is 1701 meters above sea level.

median ridge

The main watershed range of Kamchatka is a mountain range consisting of systems of peaks and passes. The ridge stretches from north to south and its length is 1200 km. A large number of passes are concentrated in its northern part, the central part represents large distances between the peaks, in the south there is a strong dissection of the massif, and the asymmetry of the slopes characterize the Sredinny Range. The tectonic structure is reflected in the relief. It consists of volcanoes, lava plateaus, mountain ranges, peaks covered with glaciers.

The ridge is complicated by structures of the lower order, the most striking of them are the Malkinsky, Kozyrevsky, Bystrinsky ridges.

The highest point belongs to and is 3621 meters. Some volcanoes, such as Khuvkhoytun, Alnay, Shishel, Ostraya Sopka, exceed the mark of 2500 meters.

Ural mountains

The Ural Mountains are a mountain system that is located between the East European and West Siberian plains. Its length is more than 2000 km, the width varies from 40 to 150 km.

The tectonic structure of the Ural Mountains belongs to the ancient folded system. In the Paleozoic, there was a geosyncline and the sea splashed. Starting from the Paleozoic, the formation of the mountain system of the Urals takes place. The main formation of folds occurred in the Hercynian period.

Intensive folding took place on the eastern slope of the Urals, which was accompanied by deep faults and the release of intrusions, the dimensions of which reached about 120 km in length and 60 km in width. The folds here are compressed, overturned, complicated by overthrusts.

Folding was less intense on the western slope. The folds here are simple, without overthrusts. There are no intrusions.

Pressure from the east was created by a tectonic structure - the Russian platform, the foundation of which prevented the formation of folding. Gradually, folded mountains appeared on the site of the Ural geosyncline.

In tectonic terms, the entire Urals is a complex complex of anticlinoria and synclinoria, separated by deep faults.

The relief of the Urals is asymmetrical from east to west. The eastern slope drops steeply towards the West Siberian Plain. The gentle western slope smoothly passes into the East European Plain. The asymmetry was caused by the activity of the tectonic structure of the West Siberian Plain.

Baltic shield

It belongs to the northwest of the East European Platform, is the largest protrusion of its basement and is elevated above sea level. In the northwest, the border runs with the folded structures of Caledonia-Scandinavia. In the south and southeast, the rocks of the shield submerge under the cover of sedimentary rocks of the East European Plate.

Geographically, the shield is tied to the southeastern part of the Scandinavian Peninsula, to the Kola Peninsula and Karelia.

The structure of the shield involves three segments, different in age - South Scandinavian (western), Central and Kola-Karelian (eastern). The South Scandinavian sector is tied to the south of Sweden and Norway. The Murmansk block stands out in its composition.

The central sector is located in Finland and Sweden. It includes the Central Kola block and is located in the central part of the Kola Peninsula.

The Kola-Karelian sector is located on the territory of Russia. It belongs to the most ancient formation structures. In the structure of the Kola-Karelian sector, several tectonic elements are distinguished: Murmansk, Central Kola, Belomorian, Karelian, they are separated from each other by deep faults.

Kola Peninsula

It is tectonically tied to the northeastern part of the Baltic crystalline shield, composed of rocks of ancient origin - granites and gneisses.

The relief of the peninsula adopted the features of the crystalline shield and reflects traces of faults and cracks. The appearance of the peninsula was influenced by glaciers, which smoothed the tops of the mountains.

The peninsula is divided into western and eastern parts according to the nature of the relief. The relief of the eastern part is not as complex as the western one. The mountains of the Kola Peninsula are in the form of pillars - on the tops of the mountains there are flat plateaus with steep slopes, at the bottom there are lowlands. The plateau is cut by deep valleys and gorges. The Lovozero tundra and the Khibiny are located in the western part, the tectonic structure of the latter belongs to mountain ranges.

Khibiny

Geographically, the Khibiny are assigned to the central part of the Kola Peninsula, they are a large mountain range. The geological age of the massif exceeds 350 Ma. Mountain Khibiny is a tectonic structure, which is an intrusive body (solidified magma) of complex structure and composition. From a geological point of view, an intrusion is not an erupted volcano. The massif continues to rise even now, the change is 1-2 cm per year. More than 500 types of minerals are found in the intrusive massif.

Not a single glacier has been found in the Khibiny, but traces of ancient ice are found. The peaks of the massif are plateau-like, the slopes are steep with a large number of snowfields, avalanches are active, and there are many mountain lakes. The Khibiny are relatively low mountains. The highest elevation above sea level belongs to Mount Yudychvumchorr and corresponds to 1200.6 m.

WESTERN SIBERIAN PLAIN, The West Siberian Lowland, one of the largest plains in the world (the third largest after the Amazonian and East European plains), in northern Asia, in Russia and Kazakhstan. It occupies the whole of Western Siberia, stretching from the coast of the Arctic Ocean in the north to the Turgai plateau and the Kazakh uplands in the south, from the Urals in the west to the Central Siberian plateau in the east. The length from north to south is up to 2500 km, from west to east from 900 km in (north) to 2000 (in south). The area is about 3 million km 2, including 2.6 million km 2 in Russia. The prevailing heights do not exceed 150 m. The lowest parts of the plain (50–100 m) are located mainly in its central (Kondinskaya and Sredneobskaya lowlands) and northern (Nizhneobskaya, Nadymskaya and Purskaya lowlands) parts. The highest point of the West Siberian Plain - up to 317 m - is located on the Priobsky Plateau.

At the base of the West Siberian Plain lies West Siberian Platform. To the east it borders on Siberian platform, in the south - with Paleozoic structures of Central Kazakhstan, the Altai-Sayan region, in the west - with the folded system of the Urals.

Relief

The surface is a low accumulative plain with a rather uniform relief (more uniform than that of the East European Plain), the main elements of which are wide flat interfluves and river valleys; various forms of manifestation of permafrost (common to 59 ° N), increased waterlogging, and developed (mainly in the south in loose rocks and soils) ancient and modern salt accumulation are characteristic. In the north, in the area of distribution of marine accumulative and moraine plains (Nadymskaya and Purskaya lowlands), the general flatness of the territory is disturbed by moraine gently sloping and hilly-sloping (North Sosvinskaya, Lyulimvor, Verkhne-, Srednetazovsky, etc.) uplands 200–300 m high, the southern boundary of which runs around 61–62 ° N. sh.; they are horseshoe-shaped covered from the south by flat-topped uplands, among which are the Poluyskaya Upland, Belogorsky Mainland, Tobolsky Mainland, Siberian Uvaly (245 m), etc. Permafrost exogenous processes (thermal erosion, heaving of soils, solifluction) are widespread in the north, deflation is common on sandy surfaces, in swamps - peat accumulation. Permafrost is ubiquitous on the Yamal, Tazovsky, and Gydansky peninsulas; the thickness of the frozen layer is very significant (up to 300–600 m).

To the south, the area of moraine relief is adjoined by flat lacustrine and lacustrine-alluvial lowlands, the lowest (40–80 m high) and swampy of which are the Konda lowland and the Sredneobskaya lowland with the Surgut lowland (105 m high). This territory, not covered by Quaternary glaciation (to the south of the line Ivdel - Ishim - Novosibirsk - Tomsk - Krasnoyarsk), is a poorly dissected denudation plain, rising up to 250 m to the west, to the foothills of the Urals. In the interfluve of the Tobol and the Irtysh, there is an inclined, in places with ridges, lacustrine-alluvial Ishim Plain(120–220 m) with a thin cover of loess-like loams and loess occurring on salt-bearing clays. It is adjacent to alluvial Baraba lowland, Vasyugan Plain and Kulunda Plain, where the processes of deflation and modern salt accumulation are developed. In the foothills of Altai - the Ob plateau and the Chulym plain.

On the geological structure and minerals, see Art. West Siberian Platform ,

Climate

The West Siberian Plain is dominated by a harsh continental climate. The significant length of the territory from north to south determines the well-defined latitudinal zonality of the climate and noticeable differences in the climatic conditions of the northern and southern parts of the plain. The nature of the climate is significantly influenced by the Arctic Ocean, as well as the flat relief, which contributes to the unhindered exchange of air masses between north and south. Winter in the polar latitudes is severe and lasts up to 8 months (the polar night lasts almost 3 months); the average January temperature is from -23 to -30 °C. In the central part of the plain, winter lasts almost 7 months; the average January temperature is from -20 to -22 °C. In the southern part of the plain, where the influence of the Asian anticyclone is increasing, at the same average monthly temperatures, winter is shorter - 5–6 months. Minimum air temperature -56 °C. The duration of snow cover in the northern regions reaches 240–270 days, and in the southern regions - 160–170 days. The thickness of the snow cover in the tundra and steppe zones is 20–40 cm; in the forest zone, from 50–60 cm in the west to 70–100 cm in the east. In summer, the western transfer of Atlantic air masses predominates with intrusions of cold Arctic air in the north, and dry warm air masses from Kazakhstan and Central Asia in the south. In the north of the plain, summer, which occurs under polar day conditions, is short, cool, and humid; in the central part - moderately warm and humid, in the south - arid and dry with dry winds and dust storms. The average July temperature rises from 5°C in the Far North to 21–22°C in the south. The duration of the growing season in the south is 175–180 days. Atmospheric precipitation falls mainly in summer (from May to October - up to 80% of precipitation). Most precipitation - up to 600 mm per year - falls in the forest zone; the wettest are the Kondinskaya and Sredneobskaya lowlands. To the north and south, in the tundra and steppe zone, the annual precipitation gradually decreases to 250 mm.

surface water

On the territory of the West Siberian Plain, more than 2,000 rivers flow, belonging to the basin of the Arctic Ocean. Their total flow is about 1200 km 3 of water per year; up to 80% of the annual runoff occurs in spring and summer. The largest rivers - the Ob, Yenisei, Irtysh, Taz and their tributaries - flow in well developed deep (up to 50–80 m) valleys with a steep right bank and a system of low terraces on the left bank. The feeding of the rivers is mixed (snow and rain), the spring flood is extended, the low water is long summer-autumn and winter. All rivers are characterized by slight slopes and low flow rates. The ice cover on the rivers lasts up to 8 months in the north, up to 5 months in the south. Large rivers are navigable, are important rafting and transportation routes, and, in addition, have large reserves of hydropower resources.

There are about 1 million lakes on the West Siberian Plain, the total area of which is more than 100 thousand km2. The largest lakes are Chany, Ubinskoye, Kulundinskoye, and others. Lakes of thermokarst and moraine-glacial origin are widespread in the north. There are many small lakes in suffusion depressions (less than 1 km 2): on the interfluve of the Tobol and Irtysh - more than 1500, on the Baraba lowland - 2500, among them there are many fresh, salty and bitter-salty ones; there are self-sustaining lakes. The West Siberian Plain is distinguished by a record number of swamps per unit area (the area of the wetland is about 800 thousand km 2).

Landscape types

The uniformity of the relief of the vast West Siberian Plain determines the clearly pronounced latitudinal zonality of landscapes, although, compared with the East European Plain, the natural zones here are shifted to the north; landscape differences within the zones are less noticeable than on the East European Plain, and the zone of broad-leaved forests is absent. Due to the poor drainage of the territory, hydromorphic complexes play a prominent role: swamps and swampy forests occupy about 128 million hectares here, and in the steppe and forest-steppe zones there are many solonetzes, solods and solonchaks.

On the Yamal, Tazovsky and Gydansky peninsulas, in conditions of continuous permafrost, landscapes of arctic and subarctic tundra with moss, lichen and shrub (dwarf birch, willow, alder) vegetation have formed on gleyzems, peat-gleyzems, peat-podburs and soddy soils. Polygonal grass-hypnum swamps are widespread. The share of primary landscapes is extremely insignificant. To the south, tundra landscapes and swamps (mostly flat-hummocky) are combined with larch and spruce-larch light forests on podzolic-gley and peat-podzolic-gley soils, forming a narrow forest-tundra zone, transitional to the forest (forest-bog) zone of the temperate zone, represented by subzones of the northern, middle and southern taiga. Swampiness is common to all subzones: over 50% of the area of the northern taiga, about 70% of the middle taiga, and about 50% of the southern taiga. The northern taiga is characterized by flat and large-hummocky raised bogs, the middle taiga is characterized by ridge-hollow and ridge-lake bogs, the southern taiga is characterized by ridge-hollow, pine-shrub-sphagnum, transitional sedge-sphagnum and lowland tree-sedge bogs. The largest swamp Vasyugan Plain. The forest complexes of different subzones, formed on slopes with different degrees of drainage, are peculiar.

Northern taiga forests on permafrost are represented by sparse, low-growing, heavily waterlogged, pine, pine-spruce and spruce-fir forests on gley-podzolic and podzolic-gley soils. The indigenous landscapes of the northern taiga occupy 11% of the plain area. Indigenous landscapes in the middle taiga occupy 6% of the area of the West Siberian Plain, in the southern - 4%. Common to the forest landscapes of the middle and southern taiga is the wide distribution of lichen and shrub-sphagnum pine forests on sandy and sandy loamy illuvial-ferruginous and illuvial-humus podzols. On loams in the middle taiga, along with extensive swamps, spruce-cedar forests with larch and birch forests are developed on podzolic, podzolic-gley, peat-podzolic-gley and gley peat-podzols.

In the southern taiga subzone on loams - spruce-fir and fir-cedar (including urman - dense dark coniferous forests with a predominance of fir) small-grass forests and birch forests with aspen on sod-podzolic and sod-podzolic-gley (including with a second humus horizon) and peat-podzolic-gley soils.

The subtaiga zone is represented by park pine, birch and birch-aspen forests on gray, gray gley and soddy-podzolic soils (including those with a second humus horizon) in combination with steppe meadows on cryptogley chernozems, solonetsous in places. Indigenous forest and meadow landscapes are practically not preserved. Boggy forests turn into lowland sedge-hypnum (with ryams) and sedge-reed bogs (about 40% of the zone). For the forest-steppe landscapes of sloping plains with loess-like and loess covers on salt-bearing tertiary clays, birch and aspen-birch groves on gray soils and malts are typical in combination with forb-grass steppe meadows on leached and cryptogleyed chernozems, to the south - with meadow steppes on ordinary chernozems, in places solonetzic and saline. On the sands are pine forests. Up to 20% of the zone is occupied by eutrophic reed-sedge bogs. In the steppe zone, the primary landscapes have not been preserved; in the past, these were forb-feather grass steppe meadows on ordinary and southern chernozems, saline in places, and in drier southern regions - fescue-feather grass steppes on chestnut and cryptogley soils, gley solonetzes and solonchaks.

Environmental issues and protected natural areas

In areas of oil production due to pipeline breaks, water and soil are polluted with oil and oil products. In forestry areas - overcutting, waterlogging, the spread of silkworms, fires. In agricultural landscapes, there is an acute problem of lack of fresh water, secondary salinization of soils, destruction of soil structure and loss of soil fertility during plowing, drought and dust storms. In the north, there is degradation of reindeer pastures, in particular due to overgrazing, which leads to a sharp reduction in their biodiversity. No less important is the problem of preserving hunting grounds and habitats of fauna.

Numerous reserves, national and natural parks have been created to study and protect typical and rare natural landscapes. Among the largest reserves: in the tundra - the Gydansky reserve, in the northern taiga - the Verkhnetazovsky reserve, in the middle taiga - the Yugansky reserve and Malaya Sosva, etc. The national park Pripyshminsky Bory was created in the subtaiga. Natural parks are also organized: in the tundra - Deer streams, in the north. taiga - Numto, Siberian Ridges, in the middle taiga - Kondinsky lakes, in the forest-steppe - Bird's harbor.

The first acquaintance of Russians with Western Siberia took place, probably, as early as the 11th century, when the Novgorodians visited the lower reaches of the Ob River. With the campaign of Yermak (1582–85), a period of discoveries began in Siberia and the development of its territory.