Absolute height of the West Siberian lowland. West Siberian Plain

The authors of all physical-geographical zoning schemes highlight Western Siberia with an area of ​​about 3 million sq. km. the same. Its boundaries coincide with the contours of the EpiPaleozoic West Siberian Plate. The geomorphological boundaries are also clearly expressed, coinciding mainly with the 200 m isohypsum, and in the north - with the coastline of the bays (lips) of the Kara Sea. Only the borders with the North Siberian and Turan plains are drawn.

Geological development and structure. In the Precambrian, the small West Siberian Platform and the foundation of the western part of the Siberian Platform were formed (approximately up to the line coinciding with the bed of the Taz River). The Ural geosyncline formed between the East European and West Siberian platforms, and the Yenisei geosyncline formed between the Siberian platforms. During their evolution in the Paleozoic, folded structures were formed along the outskirts of the West Siberian Platform: Baikalides west of the Yenisei Ridge, Salairids north of the Kuznetsk Alatau, Caledonides north of the western part of the Kazakh hills. These disparate structures were united by Hercynian folded areas, which also directly merged with the Hercynides of the Urals, Western (Rudny) Altai and the eastern part of the Kazakh hillocks. Thus, the nature of the West Siberian plate can be understood in two ways. Considering the “patchwork” nature of its foundation, it is often called heterogeneous, but since most of it was formed in the Paleozoic, the plate is considered Epipaleozoic. Noting the decisive role of the Hercynian folding, the slab is laid epihercynian.

Along with the long processes of formation of the foundation, in the Paleozoic (as well as the Triassic and Early Jurassic) the cover was created for just as long. In this regard, Paleozoic-Early Jurassic strata deposited on top of folded structures are usually classified into a special, “intermediate” or “transitional” floor (or complex), which geologists attribute either to the foundation or to the cover. It is believed that the present cover was formed only in the Meso-Cenozoic (starting from the mid-Jurassic period). The deposits of the cover overlapped the border zones of neighboring folded structures (the Siberian Platform, the Salairides of the Kuznetsk Alatau, the Caledonides and Hercynides of the Rudny Altai, Kazakhstan, and the Urals) and noticeably expanded the territory of the West Siberian Plate.

Crystalline folded foundation The plate consists of ancient (Precambrian and Paleozoic) metamorphic (schists, gneisses, granite gneisses, marbles), volcanic and sedimentary rocks. All of them are crushed into complex folds, broken into blocks by faults, and broken through by intrusions of acidic (granitoids) and basic (gabbroids) composition. The surface relief of the foundation is very complex. If you mentally remove the deposits of the cover, a sharply dissected surface of the mountain structure will be exposed with height amplitudes of 1.5 km in the peripheral parts and significantly larger ones in the north of the axial zone. The depths of the foundation naturally increase towards the axial zone and within this zone in the northern direction - from –3 to –8...-10 km, according to some data and more. The ancient West Siberian platform is fragmented into many blocks, most of which are deeply depressed, and some (for example, the Berezovsky block) are relatively elevated and can be traced on the surface (the Berezovsky Upland with maximum absolute heights of over 200 m). The margins of the West Siberian plate correspond to the slopes of neighboring folded structures, which are a kind of “shields”. In the internal parts of the plate there are syneclises (Omsk, Khanty-Mansiysk, Tazovsk and others), separated uplifts ( Vasyuganskoye) and vaults(Surgutsky, Nizhnevartovsky, etc.). Within the Kemerovo region there is part Teguldet depression with depths up to –2.5 km, strongly reminiscent of the Minusinsk depression.

“Intermediate floor consists of weakly dislocated and weakly metamorphosed strata of Paleozoic rocks overlying the basement of pre-Hercynian age (they are absent within the Hercynian structures), as well as trap rocks of the Triassic and coal-bearing terrigenous rocks of the Early Jurassic. At the end of the Permian and Triassic, a vast zone of lithospheric extension arose in Siberia. It covered the Tunguska syneclise of the Siberian Platform and submeridionally oriented zones between the Urals and the Irtysh and Poluy rivers, as well as between 74 and 84 degrees East. Many alternating grabens and horsts arose, linearly elongated in the submeridional direction (“key structure”). Trap magmatism covered almost the entire West Siberian plate (and the neighboring Tunguska syneclise). In recent decades, forecasts have been made regarding the high degree of oil and gas content of the “intermediate” floor.

Case composed of horizontally lying strata of Meso-Cenozoic sandy-clayey rocks. They have a variegated facial composition. Almost until the end of the Paleogene, marine conditions prevailed in the north; to the south they were replaced by lagoonal conditions and in the extreme south by continental ones. From the middle of the Oligocene, the continental regime spread everywhere. Sedimentation conditions changed directionally. The warm and humid climate persisted until the end of the Paleogene, and luxuriant vegetation existed. During the Neogene, the climate became noticeably cooler and drier. A huge mass of organic matter accumulated in the Jurassic and, to a lesser extent, Cretaceous strata. Organic matter dispersed in sandy-clayey material sank into the depths of the earth's crust, where it was exposed to high temperatures and petrostatic pressure, stimulating the polymerization of hydrocarbon molecules. At relatively shallow depths (up to about 2 km), long hydrocarbon chains arose, which led to the emergence of oil. At great depths, on the contrary, only gaseous hydrocarbons were formed. Therefore, the main oil fields gravitate to the southern part of the West Siberian Plate with relatively low cover thicknesses, and gas fields - to the northern regions with maximum basement depths.

Hydrocarbons dispersed in the form of an insignificant impurity slowly float to the earth's surface, most often reach the atmosphere and are destroyed. The preservation and concentration of hydrocarbons in large deposits is facilitated by the existence of reservoirs (sand and other rocks with a certain porosity) and seals (clayey, impermeable rocks).

Minerals. In the conditions of the cover of the West Siberian plate composed of sedimentary rocks, only exogenous deposits are common. Sedimentary fossils dominate, and among them are caustobiolites (oil from the southern part of the plain; the largest field is Samotlor; gas from the northern part - Urengoy in the Pur river basin, Yamburg on the Tazovsky Peninsula, Arctic on Yamal; brown coal - Kansk-Achinsk basin; peat, brown iron ore – Bakchar; evaporites of Kulunda and Baraba).

Relief. Orography and morphometry. The West Siberian Plain is considered an “ideal” low-lying plain: its absolute heights are almost everywhere below 200 m. This level is exceeded only by tiny sections of the North Sosvinskaya Upland (including the Berezovskaya Upland), the Belogorsk Continent (the right bank of the Ob River north of the mouth of the Irtysh), and the eastern section of the Siberian Uvaly ; more extensive hills are located in the foothills of Altai, the Kazakh hills, and the Urals. For a long time, on hypsometric maps, the West Siberian Plain was painted a uniform green color. A detailed study revealed, however, that the orography of the region is no less complex than within the East European Plain. Plains with heights of more than 100 m (“highlands”) and less than 100 m (lowlands) are clearly distinguished. The most famous “hills” are: Sibirskie Uvaly, Nizhneeniseiskaya, Vasyuganskaya, Barabinskaya, Kulundinskaya, (Pri) Chulymskaya; lowlands: Surgut Polesie, Kondinskaya, Severayamalskaya, Ust-Obskaya.

Morphostructure. The morphostructure of the accumulative plain clearly predominates. Only along the outskirts, especially in the southwest, south, southeast, are there denudation plains, including inclined stratal plains.

Main events of the Pleistocene. The entire territory of Western Siberia was affected to some extent glaciation on natural conditions, including morphosculpture. The ice came from the Ural-Novaya Zemlya and Taimyr-Putorana centers, which were significantly smaller than the Kola-Scandinavian center. Three glaciation epochs are most recognized: the maximum Samarova (first half of the Middle Pleistocene), Tazovsky (second half of the Middle Pleistocene), Zyryanovsky (Upper Pleistocene). Synchronously with the glacials appeared boreal transgressions, covering much larger areas than in the northeast of European Russia. At least in the northern part of Western Siberia, the glaciers were shelf glaciers and “floated”, carrying moraine material with ice. A similar picture is still observed today in the Kara Sea, which is a natural continuation of the West Siberian Plain. Land cover glaciers operated south of the Siberian Uvaly.

As now, the largest rivers flowed in accordance with the slope of the surface to the north, i.e. towards the glacier. The glacial tongue acted as a dam, to the south of which periglacial lakes (Purovskoye, Mansiyskoye, etc.) were formed, into which the melt waters of the glacier also flowed. This explains the significantly greater role of aquiglacial deposits than in Eastern Europe, and among them, outwash sands and plains.

Excessive flow of water into the periglacial lakes overwhelmed them, leading to the “splashing out” of water both to the north (which led to the formation of underwater drainage troughs, for example, the St. Anna Trench) and to the south, into the extra-glacial lakes of Western Siberia (Ishimskaya, Kulundinskaya and Barabinskaya plains). Lake and river accumulation took place here intensively. But these reservoirs also overflowed, excess water flowed through the Turgai Strait into the lakes and seas of the Black Sea-Balkhash system.

In the extreme south of Western Siberia, fine silty material was transported to the far margins of the periglacial zone mainly by flowing waters, rarely by wind. Accumulating in an arid climate, it created layers of loess-like, cover loam and loess. Thus, we can distinguish a number of zones of relict relief formation of the West Siberian Plain, successively replacing each other in a southern direction: a. boreal-marine accumulation (Yamal, territories adjacent to the Ob, Taz and Gydan bays from the south and east); b. glacial accumulation (peripheral areas of the Subpolar Urals and Putorana); V. water-glacial accumulation (mainly glacial-lacustrine - up to the parallel of the Irtysh mouth); g. terminal moraines of the Samarovo glacier (up to 59 degrees N), overlain by water-glacial deposits of the Tazovsky and Zyryanovsky glaciers; d. glacial-lacustrine accumulation; e. river and “normal” lake accumulation; and. loess formation.

Zoning of modern relief formation and types of morphosculpture. The Pleistocene relief is intensively reworked by modern agents. In the southern direction the following zones are distinguished: a. marine relief; b. cryogenic morphosculpture; V. fluvial morphosculpture, arid relief formation.

The extremely rugged coastline and low-lying flat topography of coastal areas significantly increases the area marine relief formation. The littoral zone, flooded by the sea at high tides and released at low tides, is very wide. A certain role is played by the surge of water onto flat coastal areas by the wind and the impact of the sea on the supralittoral zone, which lies above the littoral zone. Especially stand out laid down up to several kilometers wide, thermal abrasion dynamically developing shores and low but vast sea terraces.

Cryogenic The relief is widespread in the north, from the tundra to the northern subzone of the taiga inclusive. Polygonal soils, hydrolaccoliths, and heaving mounds are especially widely developed. The most significant role is played fluvial processes and forms: valley-watershed relief; in the southern regions of Western Siberia, ravines are developed in a cloak of loess-like loams and other rocks. Large ravines exist, for example, in the city limits and in the vicinity of the city of Novosibirsk. In the steppe zone it appears arid relief formation(steppe suffusion-subsidence and deflationary saucers, less often primitive accumulative sand forms).

Since relict and modern landforms overlap each other, it is necessary to identify a number of “total” geomorphological zones.

Climate The West Siberian Plain is continental (with a continentality index of 51 - 70%). It occupies a natural place in the series of increasing degrees of continentality in the eastern direction: transitional from oceanic to continental (Fennoscandia) – moderate continental (Russian Plain) – continental (Western Siberia). The most important reason for this pattern is the weakening of the climate-forming role of the Atlantic in the direction of the western transport of air masses and the gradually intensifying processes of their transformation. The essence of these processes boils down to the following: an increase in the severity of winters at almost identical summer temperatures and the resulting increase in the amplitudes of air temperature fluctuations; a decrease in precipitation and a clearer expression of the continental precipitation regime (summer maximum and winter minimum).

As in the Urals (and for the same reasons, see the corresponding section of the manual), cyclonic weather prevails in the northern part of the plain throughout the year, and anticyclonic weather prevails in the southern part. In addition, the enormous size of the territory determines the zonality of other climatic characteristics. Heat supply indicators change greatly, especially in the warm part of the year. As on the Russian Plain (see the corresponding section), there is a thickening of summer isotherms in the northern part (from 3 degrees on the Arctic coast to 16 degrees at the 64th parallel) and their thinning (up to 20 degrees at the 53rd parallel) in the southern part of the West Siberian Plain. The same can be said about the distribution of precipitation (350 mm on the coast of the Kara Sea - 500-650 mm in the middle zone - 300-250 mm in the south) and moisture (from a sharp excess - dryness indices 0.3 - in the tundra to an optimum - close to 1 in the forest-steppes - and a slight deficiency - up to 2 - in the steppe zone). In accordance with the listed patterns, the degree of continental climate of the plain increases in the southern direction.

The large extent of the plain from west to east also has an effect. The decrease in average January temperatures in this direction in the northern part of the West Siberian Plain (from –20 to –30 degrees) has already been mentioned. In the middle zone of the region, a very significant decrease in the amount of precipitation in the western part due to the influence of the barrier role of the Urals and their increase in the eastern part - in front of the barrier of the Central Siberian Plateau. In the same direction, the degree of continentality and climate severity increases.

Western Siberia exhibits typical Siberian climate features. These include, first of all, the general severity of winters or at least their individual time periods: average January temperatures are in the range of -18...-30 degrees; on the Russian Plain only the extreme northeast approaches such temperatures. A Siberian weather feature is the widespread occurrence of temperature inversions, despite the flatness of the region's topography. This is facilitated partly by the specificity of air masses overcoming the barrier of the Urals (see the corresponding section), partly by the abundance of flat orographic basins. The climate of Western Siberia is characterized by instability of weather during the transitional seasons of the year and a high probability of frost at this time.

It should be noted that there are sharp differences in the weather of the European part and Siberia. With increased cyclonic activity west of the Urals in Siberia, there is a high probability of anticyclone dominance; in summer there is a predominance of cool, rainy weather on the Russian Plain and hot, dry weather in Siberia; The mild, snowy winters of the Russian Plain correspond to the frosty, low-snow winters in Siberia. The reverse weather relationship occurs with a diametrically opposite change in the characteristics of the pressure field of the Russian Plain and Siberia.

Inland waters. Rivers, related mainly to the Kara Sea basin (basins of the Ob, Pura, Taz, Nadym, Messoyakha and a number of small rivers), are predominantly snow-fed and belong to the West Siberian type of intra-annual flow regime. It is characterized by a flood extended over time (over 2 months), but the excess of water consumption during the flood period over the annual average is small (4–5 times). The reason for this is the natural regulation of flow: excess water during floods is absorbed by very capacious floodplains and swamps. Accordingly, the summer low-water period is relatively weakly expressed, since the summer runoff is replenished from water “saved” during the flood. But the winter low-water period is characterized by very low costs, since there is only one greatly weakened power source left - groundwater. During this period, the oxygen content in rivers catastrophically decreases: it is spent on oxidation processes of organic substances contained in the water and does not penetrate well under the ice. Fish accumulate in pools, form dense mass aggregations, and are in a sleepy state.

The groundwater form a single system - the West Siberian hydrogeological basin (see its description in the general review). Their characteristics are subject to zonal distribution. In the polar and subpolar parts of the plain, groundwater lies almost on the surface, it is cold and practically does not contain mineral (gyrocarbonates, silica) impurities. In this zone, the formation of groundwater is strongly influenced by permafrost; in the northern half of Yamal and Gydan it is continuous, and to the south it is island-like. In the middle zone, as you move south, the depths, temperature and degree of mineralization of waters consistently increase. Calcium compounds appear in the solutions, then sulfates (gypsum, mirabilite), Na and K chlorides. Finally, in the extreme south of the plain, sulfates and chlorides play a leading role, so the water acquires a bitter and salty taste.

Swamps in conditions of flat, low-lying terrain, which greatly impedes the drainage of soils and soils, they become one of the leading components of landscapes. The areas of swamps and the degree of swampiness are very large (50 - 80%). Many researchers consider swamps to be aggressive PTCs, capable not only of self-preservation, but also of constant expansion at the expense of forest landscapes. This becomes possible due to the directional increase in the degree of hydromorphism of forest PTCs due to the accumulation of water (excess moisture, poor drainage) and organic matter (peat). This process is irreversible, at least in the modern era.

Zoning is observed in the distribution of bogs. Tundra swamps develop on permafrost and polygonal soils; they are frozen and contain mainly mineral substances. Within the forest-tundra and forest zone, raised oligotrophic bogs with a convex surface and a predominance of sphagnum and sedges predominate in the vegetation. In the subtaiga zone, in raised and mesotrophic transitional bogs, often hummocky, with a flat surface, green mosses and marsh grasses are mixed with sphagnum and sedges. In more southern areas, the predominance passes to lowland hummocky eutrophic bogs with a concave surface and rich vegetation.

Lakes. In the northern third of the West Siberian Plain, myriads of small thermokarst lakes (Yambuto, Neito, Yaroto, etc.) are scattered. There are very numerous small lakes of various origins in the middle zone (Piltanlor, Samotlor, Cantlor, etc.). Finally, the largest and relatively small relict lakes, often salty, are located in the south, within the Barabinskaya, Kulundinskaya, Priishimskaya and other plains (Chany, Ubinskoye, Seletyteniz, Kyzylkak, etc.). They are complemented by small saucer-shaped lakes of suffusion-subsidence genesis.

Latitudinal zonation structure. The flatness of the surface of Western Siberia determines the ideal manifestation of the latitudinal zonality of the distribution of most components of nature. However, the dominance of hydromorphic intrazonal landscapes (swamps, floodplains, riverine spaces), on the contrary, makes it difficult to identify zones.

Zonal spectrum, due to the large extent of the plain along the meridian, it is extensive: three tundra subzones, two forest-tundra subzones, northern, middle and southern taiga, sub-taiga, two forest-steppe subzones, two steppe subzones. This speaks in favor of recognition complexity of the structure zonality.

Outlines (“geometry”) of zones. In Western Siberia, the forest zone has been narrowed. Its northern border is shifted to the south, especially in comparison with Central Siberia. Usually there are two reasons for this shift - geological-geomorphological (poor drainage of the surface, which does not create conditions for the development of the root system of trees) and climatic (insufficient heat supply and sharply excessive moisture in the summer). The southern borders of the taiga and subtaiga, on the contrary, are shifted to the north under the influence of insufficient moisture for tree vegetation. The forest-steppe and steppe zones are also shifted to the north for the same reason.

Qualitative specificity of the Western Siberian provinces zones. Tundra. North of the 72nd parallel there is a subzone of arctic tundra with scanty soil and plant cover confined to frost cracks (mosses, lichens, cotton grass, partridge grass on gleyed arctic-tundra soils). Between the 72nd and 70th parallels there is a subzone of moss-lichen tundra with an admixture of wild rosemary, cranberries, blueberries and other shrubs, as well as cotton grass. The shrub tundra subzone is dominated by shrub birch, willow, and alder on tundra-gley soils. In general, the zone is called meadow-tundra; Swamps and thermokarst lakes play a significant role. Tundra fauna with ungulate and Ob lemmings is typical.

Forest-tundra stretches in a narrow (50 - 150 km) intermittent strip in the west of the plain to the south, in the east north of the Arctic Circle. Against the background of the southern tundra there are open spaces and woodlands of Siberian larch and spruce on gley-podzolic soils.

Taiga (forest-swamp zone). The predominant dark coniferous taiga consists of spruce Picea obovata, fir Abies sibirica, cedar Pinus sibirica; there is an admixture of Siberian larch Larix sibirica, and pine forests form extensive areas, especially in the western part of the plain. The degree of swampiness reaches its maximum. The soils are podzolic, often swampy and gleyed.

IN northern subzone(up to 63 - 61 degrees N in the south) forests are depressed and sparse. Mosses and sphagnum grow under their canopy; shrubs play a lesser role. Continuous permafrost is almost ubiquitous. Significant areas are occupied by swamps and meadows. Dark-coniferous and light-coniferous taiga play almost the same role. Middle taiga subzone reaches 58 - 59 degrees north latitude in the south. It is clearly dominated by dark coniferous taiga. Forests of good quality, with a developed shrub layer. Permafrost is insular. The swamps reach their maximum extent. Southern subzone It is distinguished by a more elevated and dissected relief. There is no permafrost. The southern border of the taiga approximately coincides with the 56th parallel. Spruce-fir forests dominate with a significant admixture of small-leaved species, pine and cedar. Birch forms large tracts - belniki or white taiga. In it, trees transmit more light, which favors the development of the herbaceous layer. Soddy-podzolic soils predominate. The swampiness is great, especially in Vasyugan. The southern taiga subzone extends into the Kemerovo region in two sections.

Subtaiga zone of small-leaved West Siberian forests stretches in a narrow strip from the Middle Urals to the Kemerovo region, within which it occupies the interfluve of the Yaya and Kiya rivers. Most often birch forests are identified (warty birch, downy birch, Krylova and others), less often aspen-birch forests on gray forest and soddy-podzolic soils.

Forest-steppe forms a relatively narrow strip stretching from the Southern and Middle Urals in the west to the foothills of Altai, Salair and the Chulyma River in the east; The eastern section of the zone is called the Mariinskaya forest-steppe and is located within the Kemerovo region. Woodlands (splitting trees) of warty birch or birch and aspen grow on gray forest, often solodized or podzolized soils. They alternate with meadow steppes or steppe meadows of mesophilic grasses (meadow bluegrass, reed grass, steppe timothy), rich forbs and legumes (china, clover, mouse peas) on leached and podzolized chernozems. Northern and southern subzones are distinguished with forest cover of 20–25% and 4–5%, respectively (theoretically, more or less 50%). The average plowed area of ​​the zone is 40%, pastures and hayfields occupy 30% of the total area.

Steppe the southern edge of the West Siberian Plain reaches in the east to the foothills of Altai; to the east, in the pre-Salair part of the Kemerovo region, there is a small isolated “island” of the zone, called the “steppe core” of the Kuznetsk basin. Strictly speaking, it belongs to the Altai-Sayan mountainous country, but differs little from the Western Siberian steppes. In the northern subzone, forb-grass steppes grow on ordinary chernozems. The southern subzone of feather grass-fescue (grass) steppes develops on southern low-humus chernozems and dark chestnut soils. Halophytes grow (or even dominate) on solodized soils and solonetzes. There are practically no areas of natural virgin steppes.

Physico-geographical zoning. The ideally expressed flatness of the territory makes Western Siberia a standard for the physiographic zoning of plains. In all variants of the zoning scheme of the USSR and Russia, this physical-geographical country stands out equally, which indicates the objectivity of its selection. Morphostructural (predominance of the accumulative plain), geostructural (unified geostructure of the young plate), macroclimatic (dominance of continental climate) criteria for the isolation of a physical-geographical country are understood in the same way by all authors of zoning schemes. The specificity of the structure of the latitudinal zonation of the West Siberian Plain is unique, individual and sharply contrasts with the dominance of the altitudinal zonation of neighboring mountainous countries (Urals, Kazakh small hills, Altai, Kuznetsk Alatau) and the combination of altitudinal and zonal patterns in Central Siberia.

Units second rank – physical-geographical region- are allocated according to the zonal criterion. Each region represents a segment of a complex zone within Western Siberia. The identification of such zones can be carried out with varying degrees of generalization, which leads to discrepancies in their number. This manual recommends the identification of three zones and their corresponding areas, listed in the following text.

A. The area of ​​marine and moraine plains of the tundra and forest-tundra zones.

B. The area of ​​moraine and outwash plains of the forest zone.

B. The area of ​​accumulative and denudation plains of the forest-steppe and steppe zones.

In all areas, using genetic criteria, physical geographical provinces– units third rank. The essence of the criterion is revealed in the relevant sections of the general review and when highlighting the problem of zoning the Russian Plain (see book 1 of this manual).

The West Siberian Plain is characterized by a harsh, fairly continental climate. The West Siberian Plain is the most populated and developed (especially in the south) part of Siberia. High summer temperatures in the southern half of Western Siberia are explained by the arrival of heated continental air from the south - from Kazakhstan and Central Asia. Autumn comes late.

The relief of the plain is largely determined by its geological structure. At the base of the West Siberian Plain lies the Epihercynian West Siberian Plate, the foundation of which is composed of intensely dislocated Paleozoic sediments. At the end of the Lower Oligocene, the sea left the West Siberian plate, and it turned into a huge lacustrine-alluvial plain.

Its large extent from north to south determines a clearly defined climate zonation and significant differences in climatic conditions in the northern and southern parts of Western Siberia. The continental climate of Western Siberia is also significantly influenced by the proximity of the Arctic Ocean. Cyclones often pass through the border zone of areas of high and low pressure. In the warm season, low pressure is established over Western Siberia, and an area of ​​higher pressure forms over the Arctic Ocean.

Most of the precipitation falls in the summer and is brought by air masses coming from the west, from the Atlantic. There are especially many of them in July and August, which is explained by intense activity on the Arctic and polar fronts.

The extreme southern regions of Western Siberia are characterized by droughts, occurring mainly in May and June. The harsh climate of the northern regions of Western Siberia contributes to soil freezing and widespread permafrost.

The rivers of Western Siberia, including the largest ones - the Ob, Irtysh and Yenisei, are characterized by slight slopes and low flow speeds. Peculiar lakes - “fogs” - are found in the Ural part of the plain. A large area is occupied by the tundra zone, which is explained by the northern position of the West Siberian Plain. To the south is the forest-tundra zone. The forest-swamp zone occupies about 60% of the territory of the West Siberian Plain.

Therefore, the width of the forest-steppe zone in Western Siberia is much smaller than on the East European Plain, and the main tree species found in it are birch and aspen. In the extreme southern part of the West Siberian Lowland there is a steppe zone, which is mostly plowed.

See what the “West Siberian Plain” is in other dictionaries:

The geographical position of the West Siberian Plain determines the transitional nature of its climate between the moderate continental climate of the Russian Plain and the sharply continental climate of Central Siberia. The study of the nature and natural resources of Western Siberia acquired a completely different scope after the Great October Revolution.

Many features of the nature of Western Siberia are determined by the nature of its geological structure and history of development. The formation of the main folded structures of the basement of Western Siberia, which have a predominantly meridional direction, dates back to the era of the Hercynian orogeny. The tectonic structure of the West Siberian plate is quite heterogeneous. Mesozoic formations of Western Siberia are represented by marine and continental sandy-clayey deposits.

Flora of the West Siberian Plain

Formations of rocks of Neogene age, outcropping mainly in the southern half of the plain, consist exclusively of continental lacustrine-fluvial deposits. The events of the Quaternary period had a particularly great influence on the formation of the landscapes of Western Siberia. Lower Quaternary sediments are represented in the north of the plain by alluvial sands filling buried valleys.

Some researchers of the northern regions of the country paint a more complex picture of the events of the Quaternary glaciation era in Western Siberia. On the other hand, there are supporters of a one-time glaciation of Western Siberia.

At the end of the Zyryan glaciation, the northern coastal regions of the West Siberian Plain subsided again. In the tundra zone, relief forms are especially widely represented, the formation of which is associated with the harsh climate and widespread permafrost.

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 most of the country's area, they determine the general appearance of the plain's topography.

In connection with this summer, weak northern or northeastern winds predominate and the role of westerly air transport noticeably increases. 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 zone of basement deflection.

West Siberian Plain in, West Siberian Plain

West Siberian Plain- a plain in northern Asia, occupies the entire western part of Siberia from the Ural Mountains in the west to the Central Siberian Plateau in the east. In the north it is limited by the coast of the Kara Sea, in the south it extends to the Kazakh small hills, in the southeast the West Siberian Plain, gradually rising, gives way to the foothills of Altai, Salair, Kuznetsk Alatau and Mountain Shoria. 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, the width is from 800 to 1900 km, and the area is only slightly less than 3 million km².

The West Siberian Plain is the most populated and developed (especially in the south) part of Siberia. within its boundaries are the Tyumen, Kurgan, Omsk, Novosibirsk and Tomsk regions, the eastern regions of the Sverdlovsk and Chelyabinsk regions, a significant part of the Altai Territory, the western regions of the Krasnoyarsk Territory (about 1/7 of the area of ​​Russia), as well as the northern and northeastern regions of Kazakhstan.

• 1 Relief and geological structure
• 2 Climate
• 3 Hydrography
• 4 Natural areas
• 5 Gallery
• 6 See also
• 7 Notes
• 8 Links

Relief and geological structure

The surface of the West Siberian Lowland is flat with a fairly insignificant difference in elevation. However, the relief of the plain is quite diverse. The lowest areas of the plain (50-100 m) are located mainly in the central (Kondinskaya and Sredneobskaya lowlands) and northern (Lower Obskaya, Nadymskaya and Purskaya lowlands) parts. Along the western, southern and eastern outskirts stretch low (up to 200-250 m) hills: the North Sosvinskaya and Turinskaya, Ishimskaya plains, the Priobskoye and Chulym-Yenisei plateaus, the Ketsko-Tymskaya, Verkhnetazovskaya and Lower Yenisei uplands. A clearly defined strip of hills is formed in the inner part of the plain by the Siberian Uvals (average height - 140-150 m), stretching from the west from the Ob to the east to the Yenisei, and the Vasyugan Plain parallel to them.

The relief of the plain is largely determined by its geological structure. At the base of the West Siberian Plain lies the epi-Hercynian West Siberian Plate, the foundation of which is composed of intensely dislocated Paleozoic sediments. The formation of the West Siberian plate began in the Upper Jurassic, when, as a result of breaking off, destruction and degeneration, a huge area between the Urals and the Siberian platform subsided, and a huge sedimentation basin arose. During its development, the West Siberian Plate was repeatedly captured by marine transgressions. At the end of the Lower Oligocene, the sea left the West Siberian plate, and it turned into a huge lacustrine-alluvial plain. In the middle and late Oligocene and Neogene, the northern part of the plate experienced uplift, which gave way to subsidence in Quaternary time. The general course of development of the plate with the subsidence of colossal spaces resembles an incomplete process of oceanization. This feature of the slab is emphasized by the phenomenal development of wetlands.

The foundation of the West Siberian Plate is covered with a cover of loose marine and continental Mesozoic-Cenozoic rocks (clays, sandstones, marls, etc.) with a total thickness of over 1000 m (in the depressions of the foundation 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, marine and glacial-marine (thickness in places up to 200 m). In the northern part of the West Siberian plate (the most submerged) there are the Nadym-Taz and Yamalo-Gydan syneclises, separated by a narrow sublatitudinal Messoyakha megaswell. in the central part of the West Siberian plate there are several anteclises, syneclises and narrow deep trenches elongated in the longitudinal direction: the Khanty-Mansi syneclise, the Khantei anteclise (with the Surgut and Nizhnevartovsk arches), the Pursky trench (over the southern part of the Koltogorsk-Urengoy rift), the Ket-Vakh anteclise and Khudoseisky trench with Chulym syneclise. To the south of the Ket-Vakh and Khantei anteclises there are the latitudinally elongated Middle Irtysh and Kulunda syneclises.

Individual geological structures, despite the thick layer of sediments, are reflected in the relief of the plain: for example, the Verkhnetazovskaya and Lyulimvor hills correspond to gentle anticlinal uplifts, and the Barabinskaya and Kondinskaya lowlands are confined to the syneclises of the foundation of the plate. However, in Western Siberia, discordant (inversion) morphostructures are also common. 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 zone of basement deflection.

The mantle of loose sediment contains horizons of groundwater - fresh and mineralized (including brine), and hot (up to 100-150°C) water is also found. There are industrial deposits of oil and natural gas (West Siberian oil and gas basin). in the Khanty-Mansi syneclise, Krasnoselsky, Salym and Surgut regions, in the layers of the Bazhenov formation at a depth of 2 km there are the largest shale oil reserves in Russia.

Climate

The West Siberian Plain is characterized by a harsh, fairly continental climate. Its large extent from north to south causes a clearly defined climate zonation and significant differences in climatic conditions in the northern and southern parts of Western Siberia. The continental climate of Western Siberia is also significantly influenced by the proximity of the Arctic Ocean. The flat terrain facilitates the exchange of air masses between its northern and southern regions.

During the cold period, within the plain, there is an interaction between an area of ​​relatively high atmospheric pressure located over the southern part of the plain and an area of ​​low pressure, which in the first half of winter extends in the form of a trough of the Icelandic baric minimum over the Kara Sea and the northern peninsulas. In winter, continental air masses of temperate latitudes predominate, which come from Eastern Siberia or are formed locally as a result of cooling of the air over the plain.

Cyclones often pass through the border zone of areas of high and low pressure. Therefore, in winter the weather in the coastal provinces is very unstable; On the coast of Yamal and the Gydan Peninsula, strong winds occur, the speed of which reaches 35-40 m/sec. The temperature here is even slightly higher than in neighboring forest-tundra provinces, located between 66 and 69° N. w. However, further south, winter temperatures gradually rise again. In general, winter is characterized by stable low temperatures and few thaws. 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°. Spring is short, dry and relatively cold; April, even in the forest-swamp zone, is not yet quite a spring month.

In the warm season, low pressure is established over Western Siberia, and an area of ​​higher pressure forms over the Arctic Ocean. Due to this summer, weak northern or northeastern winds prevail and the role of westerly air transport noticeably increases. In May there is a rapid increase in temperatures, but often, when arctic air masses invade, there are returns of cold weather and frosts. The warmest month is July, the average temperature of which ranges 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 44° in the extreme southern regions (Rubtsovsk). High summer temperatures in the southern half of Western Siberia are explained by the arrival of heated continental air from the south - from Kazakhstan and Central Asia. Autumn comes late.

Most of the precipitation falls in the summer and is brought by air masses coming from the west, from the Atlantic. the period 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 intense activity on the Arctic and polar fronts. The amount of winter precipitation is relatively small and ranges from 5 to 20-30 mm/month. In the south, during some winter months there is sometimes no snow at all. There are significant fluctuations in precipitation between years. Thus, in the forest-steppe zone, where with an average long-term precipitation of about 300-350 mm/year, up to 550-600 mm/year falls in wet years, and only 170-180 mm/year in dry years. The extreme southern regions of Western Siberia are characterized by droughts, occurring mainly in May and June.

The duration of snow cover in the northern regions reaches 240-270 days, and in the south - 160-170 days. The thickness of the snow cover in the tundra and steppe zones in February is 20-40 cm, in the forest-swamp zone - from 50-60 cm in the west to 70-100 cm in the eastern Yenisei regions.

The harsh climate of the northern regions of Western Siberia contributes to soil freezing and widespread permafrost. On the Yamal, Tazovsky and Gydansky peninsulas, permafrost is found everywhere. In these areas of continuous (merged) distribution, the thickness of the frozen layer is very significant (up to 300-600 m), and its temperatures are low (in watershed areas - 4, -9°, in valleys -2, -8°). To the south, within the northern taiga to a latitude of approximately 64°, permafrost occurs in the form of isolated islands interspersed with taliks. Its thickness decreases, temperatures rise to 0.5 -1°, and the depth of summer thawing also increases, especially in areas composed of mineral rocks.

Hydrography

The territory of the plain 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 and other connections with a large cover of loose sediments, consisting of alternating water-permeable (sands, sandstones) and water-resistant rocks, artesian basins are characterized by a significant number of aquifers confined to formations of various ages - Jurassic, Cretaceous, Paleogene and Quaternary. The quality of groundwater in these horizons is very different. In most cases, artesian waters of deep horizons are more mineralized than those lying closer to the surface.

More than 2,000 rivers flow through the territory of the West Siberian Plain, the total length of which exceeds 250 thousand km. These rivers carry about 1,200 km³ of water into the Kara Sea annually - 5 times more than the Volga. The density of the river network is not very large and varies in different places depending on the topography and climatic features: in the Tavda basin it reaches 350 km, and in the Barabinsk forest-steppe - only 29 km per 1000 km². Some southern regions of the country with a total area of ​​more than 445 thousand km² belong to areas of closed drainage and are distinguished by an abundance of drainless lakes.

The main sources of nutrition for most rivers are melted snow waters and summer-autumn rains. In accordance with the nature of the food sources, the runoff is uneven over the seasons: 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), Western Siberian rivers are frozen. Therefore, no more than 10% of the annual runoff occurs in the winter months.

The rivers of Western Siberia, including the largest ones - the Ob, Irtysh and Yenisei, are characterized by slight slopes and low flow speeds. For example, the fall of the Ob riverbed in the area from Novosibirsk to the mouth over a distance of 3000 km is only 90 m, and its flow speed does not exceed 0.5 m/sec.

On the West Siberian Plain there are about one million lakes, the total area of ​​which is more than 100 thousand km². Based on the origin of the basins, they are divided into several groups: those occupying the primary unevenness of the flat terrain; 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, overflow in the spring, sharply reducing their size in the summer, and by autumn many disappear altogether. In the southern regions, lakes are often filled with salt water. The West Siberian Lowland holds the world record for the number of swamps per unit area (the area of ​​the wetland is about 800 thousand square kilometers). The reasons for this phenomenon are the following factors: excess moisture, flat topography, permafrost and the ability of peat, which is available here in large quantities, to retain a significant amount of water.

Natural areas

The large extent from north to south contributes to a pronounced latitudinal zonality in the distribution of soils and vegetation cover. Within the country there are gradually replacing one another tundra, forest-tundra, forest-swamp, forest-steppe and steppe zones. In all zones, lakes and swamps occupy fairly large areas. Typical zonal landscapes are located on dissected and better drained upland and riverine areas. In poorly drained interfluve spaces, where drainage is difficult and the soils are usually highly moist, swamp landscapes predominate in the northern provinces, and landscapes formed under the influence of saline groundwater in the south.

A large area is occupied by the tundra zone, which is explained by the northern position of the West Siberian Plain. To the south is the forest-tundra zone. The forest-swamp zone occupies about 60% of the territory of the West Siberian Plain. There are no broad-leaved and coniferous-deciduous forests here. The strip of coniferous forests is followed by a narrow zone of small-leaved (mainly birch) forests. The increase in climate continentality causes a relatively sharp transition, compared to the East European Plain, from forest-swamp 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 smaller than on the East European Plain, and the main tree species found in it are birch and aspen. In the extreme southern part of the West Siberian Lowland there is a steppe zone, which is mostly plowed. The flat landscape of the southern regions of Western Siberia adds variety to the manes - sandy ridges 3-10 meters in height (sometimes up to 30 meters), covered with pine forest.

Gallery

Windmills on the Siberian Plain
(S. M. Prokudin-Gorsky, 1912)

Village in Tomsk region

Landscape of the West Siberian Plain

Tom's floodplain

Mariinsky forest-steppes

see also

• West Siberian subtaiga

Notes

1. 1 2 3 Western Siberia: a brief physical and geographical overview
2. 1 2 3 4 5 6 7 8 9 10 11 12 13
3. Russia. Encyclopedia Britannica. Retrieved June 24, 2013. Archived from the original on August 22, 2011.
4. 1 2 3 4 Western Siberia
5. 1 2
6. Milanovsky E.E. Geology of Russia and neighboring countries (Northern Eurasia) - M.: Moscow State University Publishing House, 1996. - 448 p. ISBN 6-211-03387-6
7. About the Bazhenov Formation “Expert” No. 12 (746)
8. 1 2 West Siberian Plain: General characteristics
9. 1 2 Western Siberia

Links

• West Siberian Plain - article from the Great Soviet Encyclopedia
• West Siberian Plain in the book: N. A. Gvozdetsky, N. I. Mikhailov. Physical geography of the USSR. M., 1978.
• Kröner, A. (2015) The Central Asian Orogenic Belt.

West Siberian Plain, West Siberian Plain in, West Siberian Plain grain, West Siberian Plain on, West Siberian Plain definition, West Siberian Plain coloring, West Siberian Plain photo, West Siberian Plain this, West Siberian flat

West Siberian Plain Information About

The Russian Federation has one of the largest plains in area located on the surface of the globe. In the north, its border is the Kara Sea. In the south it extends to the space of the Kazakh fine sand. The eastern part is the Central Siberian Plateau. The border in the west becomes ancient. The total area of ​​this flat space is almost 3 million kilometers.

In contact with

Relief features

The territory where the West Siberian Plain is located was formed a long time ago and has successfully survived all tectonic shocks.

It is strictly limited by officially recognized coordinates of the extreme points:

• on the mainland part of the space the extreme eastern point becomes Cape Dezhnev, 169°42′ W. d.;
• in the north, Cape Chelyuskin (Russia), 77°43′ N becomes such a point. sh.;
• coordinates 60° 00′ N. w. 100° 00′ E. d.

Hills

The altitude above sea level of the space under consideration is characterized by minimal differences.

It is shaped like a shallow dish. Elevation differences vary from 50 (minimum) to more than 100 meters in low areas, the prevailing heights up to 200-250 meters located on the southern, western and eastern outskirts. On the northern outskirts, the landscape rise is about 100-150 meters.

This is due to the location of the plain in the space of the Epihercynian plate, the basis of which is the foundation created by the overlay of Paleozoic sediments. This plate began to form in the Upper Jurassic period, the so-called Upper Jurassic.

During the formation of the surface layer of the planet, the flat terrain sank, turned into a lowland and became a sedimentation basin. The site is located on an area located between the Urals and the Siberian platform.

Average values

This space is one of the largest low-lying areas on the planet, a type of accumulative plain, and has an average height of 200 meters. Low-lying areas are located in the central part of the area, in the northern areas, on the borders of the Kara Sea. Almost half space is located at an altitude below 100 meters above sea level. This ancient section of the earth’s space also has its own “elevations,” smoothed out over billions of years since its creation. For example, the North Sosvinskaya Upland (290 meters). The Verkhnetazovskaya Upland rises to 285 meters.

Low places

The surface has a concave shape with minimal heights in the central part. The average minimum height is 100 meters. Counting is carried out according to tradition from sea level.

Fully justifies the name “plain”. The height differences in the colossal space are minimal.

This feature also shapes the continental climate. Frosts in some areas can reach up to -50 degrees Celsius. Such indicators are noted, for example, in Barnaul.

In absolute terms, this territory is also not distinguished by large numbers. The absolute height here is only 290 meters. Parameters were recorded on the North Sosvenskaya Upland. In most of the plain the figure is 100-150 meters.

This geographical object occupies 1/7 of the Russian Federation. The plain extends from the Kara Sea in the north to the Kazakh steppes in the south. In the west it is limited by the Ural Mountains. The size is almost 3 million kilometers.

Characteristic

The general characteristics are based on the process of formation of the plain during the most ancient stages of the development of the planet and the long-term leveling of the surface during the passage of glacial masses. This explains the monotony of the smoothed relief. Due to this, the space is strictly zoned. The north is distinguished by tundra and the south - steppe landscapes. The soil is minimally drained. Most of it is occupied by swampy forests and swamps. Such hydromorphic complexes occupy a lot of space, about 128 million hectares. The south of the plain is characterized by a large number of spaces such as various types of solods, solonetzes and large-sized solonchaks.

Note! The climate of the plain, due to its large area, ranges from moderately continental on the Russian Plain to sharply continental. Central Siberia is distinguished by this indicator.

For a long time, people have lived on the West Siberian Plain. Already in the 11th century, Novgorodians came here. Then they reached the lower reaches of the Ob. The period of opening up space for the Russian state is associated with the legendary campaigns of Ermak from 1581 to 1584. It was at this time that many discoveries of lands were made in Siberia. The study of nature was carried out and described in the 18th century during the Great Northern and Academic Expeditions. Development in these areas continued in the following decades. It was related:

• with the resettlement of the peasantry from Central Russia in the 19th century;
• planning the construction of the Siberian Railway

Detailed soil and geographical maps of the land were compiled. Active development of the territories continued in the years after the change of state power in 1917 and beyond.

As a result, today it has become inhabited and mastered by people. Here are located such large regions of Russia as Pavlodar, Kustanai, Kokchetav regions, Altai Territory, western regions of the Krasnoyarsk Territory, eastern territories Sverdlovsk and Chelyabinsk regions.

About 150 years ago, the role of Siberia as a kind of bridge between the European part of Russia and its eastern part was finally formed. In our time, the role of this territory as an economic bridge, especially with the construction of the Baikal-Amur Mainline, has finally taken shape, using all types of transport for development.

Note! The active development of territories is largely due to large volumes of deposits: natural gas, oil, brown coal, iron ore and many others.

The successful development of the territory was facilitated by a large number of large, mostly navigable, especially such giants as Ob, Irtysh, Yenisei. Nowadays, rivers are convenient transport routes and are used to generate energy to ensure a high level of quality of life for the population of the regions.

Age indicator

The basis of the smooth and level flat surface east of the Ural Mountains is a plate formed during the Paleozoic period. According to the parameters of the formation of the planet’s surface, this plate is quite young. Over millions of years of formation, the surface of the plate was covered with Mesozoic and Cenozoic sediments.

According to their characteristics, they belong to the type of sea and sand- clay deposits. Layer thickness is up to 1000 meters. In the southern part, deposits in the form of loess reach a thickness of 200 meters, formed due to the presence of lacustrine sediment formation areas in these areas.

The West Siberian Plain, which occupies about 3 million. km 2, is one of the greatest plains on 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 Table Country, 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 the outcrops of dislocated Paleozoic and older rocks in some places along the edges of the lowland, 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 border is drawn along the Kustanai swell, where the pre-Mesozoic foundation lies at a depth of 50-150 m from the surface. The length of the plain from north to south is 2500 km. Maximum 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-Mansi 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 Tselinny 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, fluctuations in heights are insignificant. Maximum marks (250-300 m) concentrated in the western part of the plain - in the pre-Ural region. 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, absolute elevations on 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 elevations on the Gydan Peninsula reach 150-183 m, and on Tazovskam - 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: North Sosvinskaya, Tobolsk-Tavdinskaya, Ishimskaya, Ishimskaya-Irtyshskaya and Pavlodarskaya inclined plains, Vasyuganskaya, Priobskoe and Chulym-Yenisei plateaus, Vakh-Ketskaya and Srednetazovskaya uplands, etc.

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

The flatness of the territory was created by a long geological history in pre-Quaternary times. The entire West Siberian Plain is located in the area of ​​Paleozoic folding and tectonically represents 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 areas of the plain passed through Cenozoic and Mesozoic rocks and reached the surface of the slab foundation 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), 70 km east of Petropavlovsk - at 920 m(745 m from sea level), and in Turgay - at 325 m. In the area of ​​the eastern slope of the North Sosvinsky arch, the Paleozoic foundation is lowered to a depth of 1700-2200 m, and in the central part of the Khanty-Mansi depression - 3500-3700 m.

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

In the north of the West Siberian plate, in the interfluve of the lower Ob and Taz rivers, the Ob-Taz syneclise stands out, and in the south, along the course of the middle Irtysh, there is the Irtysh syneclise and in the area of ​​the Kulundinsky lake - the Kulundinsky depression. In the north, slabs in syneclises, according to the latest data,

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

In terms of geological structure, the foundation of the West Siberian Plate is apparently heterogeneous. It is believed that it consists of folded structures of the Hercynian, Caledonian, Baikal and more ancient ages.

Some large geological structures of the West Siberian plate - syneclises and anteclises - correspond to elevated and lowland areas in the relief of the plain. For example, lowlands-syneclises: the Baraba lowland corresponds to the Omsk depression, the Khanty-Mansi lowland formed on the site of the Khanty-Mansi depression. Examples of anteclise hills 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 lowering of the basement into syneclises of the plate. Such morphostructures include the Pavlodar, Tobolsk-Tavdinsk inclined plains, etc.

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

The Upper Cretaceous sea gave way to the Tertiary. Sediments 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 between the sea basins of the Aral-Caspian Basin and the West Siberian Plain was carried out through the Turgai Strait. Throughout the Paleogene, there was a gradual subsidence of the plate, reaching its greatest depth in the eastern regions. This is evidenced by the increasing thickness and character of Paleogene deposits to the east: in the west, in the Cis-Urals, near the Kazakh hillocks, sands, conglomerates and pebbles predominate. Here they are highly elevated and reach the surface or lie at shallow depths. Their power reaches 40-100 in the west m. To the east and north, sediments descend beneath Neogene and Quaternary sediments. For example, in the Omsk region, Paleogene deposits were discovered by drilling wells at a depth of more than 300 m from the surface, and even deeper they lie north of the station. Tatarskaya. Here they become thinner (clays, flasks). At the confluence of the river Irtysh in the river Ob and further north along the river. Ob Paleogene layers rise again and emerge along river valleys in natural outcrops.

After a long marine regime, the primary accumulative plain uplifted by the beginning of the Neogene, and a continental regime was established on it. Judging by the nature of the occurrence of Paleogene sediments, we can say that the primary accumulative marine plain had a bowl-shaped relief structure: it was all most depressed in the central part. This surface structure at the beginning of the Neogene largely predetermined the modern features of the relief of the West Siberian Plain. During this period, the land was covered with 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 from the Irtysh, Tavda, Tura and Tobol rivers. The sediments contain well-preserved remains of flora (swamp cypress, sequoia, magnolia, linden, walnut) and fauna (giraffes, camels, mastodons), 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 experienced three glaciations (Samarovsky, Tazovsky and Zyryansky). Glaciers descended onto 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 glaciation centers in the West Siberian Plain is proven by the distribution of boulders. Glacial boulder deposits cover vast areas of the plain. However, in the western part of the plain - along the lower reaches of the Irtysh and Ob rivers - the 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; in the interfluves of the Gydan Peninsula, trap fragments predominate, brought from the northeast from the Taimyr center. The ice sheet descended during the Samarovsky glaciation along a leveled surface to the south, to approximately 58° N. w.

The southern edge of the glacier stopped the flow of pre-glacial rivers that directed their waters into the Kara Sea basin. Some of the river water apparently reached the Kara Sea. Lake basins arose at the southern edge of the glacier, and 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, overlying their bedrock. It is assumed that the formation of loess-like loams is associated with aeolian or eluvial processes, and perhaps these are deltaic and coastal deposits of ancient seas.

During interglacial periods, the northern part of the West Siberian Lowland was flooded by the waters of the boreal transgression, which penetrated through the valleys of large rivers - the Ob, Taz, Pura, Yenisei, etc. Sea waters entered the furthest south along the river valley. Yenisei - up to 63° N. w. The central part of the Gydan Peninsula was an island in the marine boreal basin.

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

The last glaciation in Western Siberia did not have a cover character. Glaciers descending from the Urals, Taimyr and 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. For example, sea

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

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

1. The zone of the Prikar 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 was 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 marine terraces.

2. The zone of the Ob-Yenisei accumulative hilly and flat-undulating water-glacial plains is located between 70 and 57° N. t., from the Urals to the Yenisei. On the Gydansky and Yamal peninsulas it occupies internal areas, extending north of 70° N. sh., and in the Cis-Ural region it descends south of 60° N. sh., in the river basin Tavdy. In the central regions, up to the southern border of the Samarov glaciation, this territory was covered with glaciers. It is composed of boulder clays, boulder sands, and loams.

Prevailing altitudes above sea level - 100-200 m. The surface of the plain is flat-undulating, with moraine hills 30-40 m high. m, with ridges and shallow lake depressions, rugged topography and ancient drainage hollows. Large areas are occupied by outwash lowlands. There are especially many lakes found among the vast interfluve swamps of the Ob-Tazov Plain.

3. The zone of periglacial water-accumulative 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-gully erosion-accumulative plains includes the Priishimskaya Plain, located in the river basin. Ishim, Baraba and Kulunda steppes. The main landforms were created by powerful water flows, which formed wide hollows of ancient flow of the south-west direction, filled with alluvial deposits. Watershed periglacial areas have a rugged topography. Manes height 5-10 m are elongated mainly in the same direction as the ancient drainage basins. They are expressed especially clearly in the Kulundinskaya and Barabinskaya steppes.

5. The zone of piedmont denudation plains is adjacent to the mountain structures of the Urals, Salair Ridge and Kuznetsk Alatau. The foothill plains are the most elevated areas of the West Siberian Plain; they are composed of sediments of 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 and depressions, some of which contain lakes.

Thus, on the territory of the West Siberian Plain, geomorphological zoning is clearly visible, which is determined by 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 here

Narrow strips of sea plains, an area of ​​glacial demolition (located in the northwest and northeast), zones of glacial accumulation, stripes of woodlands and non-glacial zones clearly emerge. But on the Russian Plain the non-glacial zone ends with marine plains, and on the West Siberian Plain it ends with a zone of foothill plains.

The valleys of the Ob and Irtysh rivers, reaching a width of 80-120 km, pass through all the indicated geomorphological zones. Valleys cut through Quaternary and Tertiary sediments to a depth of 60-80 m. The floodplains of these rivers are 20-40 wide km have numerous meandering channels, oxbow lakes, and coastal ramparts. Terraces rise above the floodplains. Everywhere in the valleys there are two terraces of accumulative-erosive 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 asymmetrical structure. On steep slopes there are ravines and landslides.

Minerals are concentrated in the primary and quaternary sediments of the plain. In Jurassic deposits there are coal deposits that have been studied in the southwestern part of the plain and in the Turgai Plain. Brown coal deposits were discovered in the Middle Ob basin. The Middle Ob basin includes the Tomskoye, Prichulymskoye, Narymskoye and Tymskoye fields. Phosphorites and bauxites, discovered in the northern part of the Turgai trough, are concentrated in the Cretaceous deposits of the plain. Iron ore deposits, represented by oolitic iron ores, were recently discovered among the Cretaceous deposits in the south of the West Siberian Plain and in the northwestern part of the Turgai trough. 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, in addition, in the basins of the Vasyugan, Keti and Tym rivers. Iron ores contain iron - from 30 to 45%. Iron ore deposits were discovered in the Kulundinskaya steppe (area 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 industrial oil in Western Siberia was obtained. In March 1961, a well clogged in the center of the West Siberian Lowland, in the middle reaches of the river. Ob, near the village of Megion. Industrial oil is concentrated in Lower Cretaceous sediments. Oil and gas fields are confined to Jurassic and Cretaceous rocks. 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), and peat bogs. Peat reserves are huge. The total volume of explored peatlands is more than 400 million. m 2 air-dry peat. The average thickness of peat layers is 2.5-3 m. In some ancient drainage depressions (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. 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 flow

air masses from the Atlantic Ocean under the influence of west-east transport. The considerable distance 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 topography of the swampy and concave plain, open to the Arctic Ocean, does not prevent the invasion of cold Arctic air masses. They freely penetrate to Kazakhstan, changing as they move. The flatness of the territory allows continental tropical air to penetrate far to the north. Thus, meridional air circulation occurs. Do the Ural Mountains have a significant influence 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 western air masses arrive on the West Siberian Plain drier;

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

In winter, the entire area gets very cold. To the east of the West Siberian Plain, a stable region of the Asian High is formed. Its spur is the Voeikov axis, which extends across the southern part of the plain from November to March. A trough of low pressure of the Icelandic low stretches over the Kara Sea: the pressure decreases from south to north - towards the Kara Sea. Therefore, southern, southwestern and southeastern winds predominate.

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

In the south there is an isotherm of -15°, and in the northeast -30°. The western part of the plain is warmer than the eastern 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 under the influence of the Asian anticyclone.

Snow cover in the north appears in the first ten days of October and lasts on the peninsulas for approximately 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 disappears at the end of April, and in the north - at the end of June (20/VI).

In summer, over all of Asia, as well as over the territory of the West Siberian Plain, the pressure is reduced, so Arctic air freely penetrates its territory. When moving south, it warms up and is additionally moistened due to local evaporation. But the air warms up faster than it is humidified, which causes a decrease in its relative humidity. Warmer western air masses arriving on the West Siberian Plain are transformed along the way more than the Arctic ones. Intensive transformation of both Arctic and Atlantic air masses leads to the fact that the lowland area is filled with dry continental temperate air with a high temperature. Cyclonic activity develops most intensively in the northern part of the plain, due to increasing temperature differences between 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.

Average July isotherms run almost in the latitudinal direction. In the far north, across the island. Bely, the isotherm is +5°, to the south of the Arctic Circle there is an isotherm of +15°, through the steppe regions it stretches with a deviation to the southeast - to Altai - the isotherm is +20, +22°. 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 temperature conditions, 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 across the territory and seasons. Highest rainfall - from 400 to 500 mm- falls in the middle zone of the plain. To the north and south the amount of precipitation decreases noticeably (up to 257 mm - on Dikson Island and 207 mm- in Semipalatinsk). The greatest amount of precipitation falls throughout the plain from May to October. But the maximum precipitation gradually moves from south to north: in June it is in the steppe, in July in the taiga, in August in the tundra. Showers occur during the passage of a cold front and during thermal convection.

In the middle and southern zones of the plain, thunderstorms occur from May to August. For example, in the Barabinskaya and Kulundinskaya steppes, during the warm period, from 15 to 20 days with thunderstorms are observed. In Tobolsk, Tomsk, and Tselinograd, up to 7-8 days with thunderstorms were recorded in July. During thunderstorms, squalls, heavy downpours, and hail are common.

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, Pura and Yenisei. The Ob basin covers an area of ​​about 3 million km. km 2 and is one of the largest river basins in the USSR.

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

The rivers flowing into the Ob and Irtysh have flow rates of 0.1-0.3 in the taiga region in summer m/sec, and in spring flood - 1.0 m/sec. All rivers flow in loose, mainly Quaternary sediments, have a large tortuosity 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 clastic material to the West Siberian Plain and their hydrological regime partly depends on the melting of snow and ice in the mountains. The main flow of the lowland rivers is directed to the north-northwest. This is related to the peculiarities of the ice regime: on all rivers, freeze-up begins in the lower reaches and

(to view the picture in full size, click on it)

gradually moves upstream. In the north, ice cover lasts 219 days, and in the south - 162 days. Spring ice drift begins in the upper parts of the basins and gradually moves to the mouths of 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, rivers open in April - May, in the north - from mid-May to mid-June. The duration of spring ice drift is usually up to 25 days, but can reach up to 40 days. This is explained by the following reasons: in areas located in the lower reaches of rivers, spring comes later; The ice on the rivers in the lower reaches reaches great 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 (at Novosibirsk - 185 days, in the lower reaches - 155 days).

West Siberian rivers are predominantly fed by snow, but also by rain and groundwater. All rivers have spring floods, and they can last for quite a long time. The spring flood gradually turns into a summer flood, which depends on rain and ground nutrition.

River Ob. The Ob begins near the city of Biysk from 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 Ob Bay) - 6370 km. According to the water content of the river. The Ob ranks third among the rivers of the USSR, losing 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 river. 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 asymmetrical shape: the right bank part of the basin makes up 33% of the catchment area, and the left bank - 67%.

According to the hydrographic and hydrological conditions and morphology of the river valley. The Ob is divided into three parts: 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 Ob Bay. The Upper Ob flows in the hilly foothills of the Altai steppe. 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 are the rivers Charysh and Alei, flowing from Altai.

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

Irtysh River - largest tributary of the river 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 of the elephant 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 turbulent ones - 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 through a mountain gorge. Near the city of Semipalatinsk r. The Irtysh overlooks 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 channel slopes are insignificant, the banks are composed of sandy-clayey deposits. All along the river. The highest bank of the Irtysh is the right one.

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. The large number of lakes is due to the flatness and poor drainage of the territory; the activity of the cover glacier and its melt waters; permafrost-sinkhole phenomena; river activities; suffusion processes occurring in loose sediments of the southern part of the lowland; destruction of peat bogs.

Based on the origin of the basins, the lakes of the West Siberian Plain are divided into the following types: 1) lacustrine basins, which inherited the overdeepened areas of the ancient runoff depressions. 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 cover glaciations. Lakes of this type are located in ancient drainage depressions. They have a predominantly elongated or oval shape and insignificant (0.4-0.8 m) depth: however sometimes they reach a depth of 25 m; 2) lake basins of inter-ridge depressions 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 sharp 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 vary, but no 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-Tazovsky interfluve within the Siberian Uvaly. In the south of the forest zone, ancient moraine lakes are already in a transitional stage; 6) sor lakes formed in the depressions of the mouths of tributaries in the lower reaches of the Ob and Irtysh rivers. During spills and floods in the spring, 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 riverbeds - 5-10 m. In the summer, they gradually discharge water into the beds of the main river, and in the middle of summer, and sometimes towards the end of it, flat areas covered with silt remain in place of the reservoirs. Sora lakes are favorite feeding grounds for many species of fish, as they heat up quickly and are rich in food; 7) secondary lakes, the basins of which are formed due to the destruction of peatlands. They are common in swampy 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) suffosion lake basins, common in the southern regions of the lowland. In loose sediments, from which dust particles are washed out under the influence of groundwater, soil subsidence occurs. Depressions, funnels, and saucers form on the surface. The emergence of basins of many salty and bitter-salty lakes is apparently associated with suffusion processes.

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

The main areas of modern feeding 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 the north.

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

In Quaternary deposits, water is mostly free-flowing, with the exception of those areas where it is concentrated in intermoraine fluvioglacial deposits and among the loamy strata of the Ob Plateau.

In the Irtysh and Tobolsk artesian basins, the waters of Quaternary sediments are fresh, salty and brine in composition. In the rest of the West Siberian basin, the waters of Quaternary sediments 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 lowland wetlands, rivers are the most important means of communication. The Ob River and its large tributaries - 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 disadvantage 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 Ob approaches close to neighboring river basins; 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. Tobola comes close to the river basin. Ural and to the river basin Kama.

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

Ichthyofauna of the river Obi is varied. In certain sections of the river, various fish are of commercial importance. In the upper reaches, before the river flows into it. Chulym, there are commercial fish: sturgeon - sturgeon, sterlet; from salmon - nelma, cheese, muksun. Along the tributaries they catch Siberian roach (of the cyprinids), crucian carp, pike, perch, and burbot. In the middle reaches of the river. The Ob River, where morbidity is highly developed in winter, fish that require oxygen, leave. Fishes that live in rivers permanently are of commercial importance - roach (chebak), dace, ide, crucian carp, pike, perch. In the summer, on the way to spawning or feeding, sturgeon, nelma, cheese, and muksun come here. In the lower reaches of the river - up to the Gulf of Ob - there are: sturgeon, nelma, cheese, pyzhyan, 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 weak ground nutrition, affect their mineralization: in the fall, the volume of water in lakes usually decreases sharply, the water becomes bitterly salty and, therefore, cannot be used for drinking. To reduce evaporation and maintain a sufficient volume of water in lakes, they resort to diking lake basins, afforestation, snow retention in catchment areas,

increasing drainage areas under favorable topographic conditions by connecting several isolated drainage basins.

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

Large numbers of geese and ducks are caught annually on the Baraby lakes. In 1935, a muskrat was released into the lakes of western Baraba. It acclimatized and spread widely.

Geographical zones. On the vast West Siberian Plain, the latitudinal zonation of all components of nature that were formed in post-glacial times, namely climate, soils, vegetation, water, and fauna, 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 are unequal in area (see Table 26).

The table shows that the dominant position is occupied by the forest zone, and the smallest area is occupied by 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 thanks to the local Western Siberian natural conditions (flatness, widely developed clay-sandy deposits with horizontal occurrence, a climate with transitional features between the temperate continental Russian Plain and continental Siberia, severe swampiness, the 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. For example, the subzone of mixed forests of the Russian Plain extends east only to the Urals. The oak forest-steppe of the Russian Plain does not cross the Urals. West Siberian 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 extend. 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 at approximately 67° N. sh.; R. It crosses the Yenisei north of the town of Dudinka. The forest-tundra stretches in a narrow strip: in the area of ​​the Ob Bay, its southern border goes south of the Arctic Circle, and to the east of the Ob Bay, along the Arctic Circle; beyond the river valley The Taz border runs north of the Arctic Circle.

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

Along the coast stretches a primary marine plain 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 caused by Quaternary uplifts. The surface of the terraces is flat, with scattered saucer-shaped lakes 3-4 deep m. On the surface of the sea terraces there are dunes 7-8 high m, blowing basins. The formation of aeolian forms is favored by: 1) the presence of loose sea sands not fixed by vegetation; 2) poor sand moisture in spring and summer; 3) strong wind activity.

The interior 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, erosion activity, especially deep-seated, is weakened. Erosion activity is prevented by continuous drizzling rains and numerous lakes, which regulate runoff throughout the warm season. Therefore, floods do not occur on rivers. However, erosion activity is currently one of the main factors transforming the original relief of the moraine-hilly and marine plain: wide river valleys, many meanders, young ravines along the ledges of terraces, valleys and lake basins. Slope changes occur as a result of colluvial erosion, solifluction and landslides.

In areas where permafrost develops, thermokarst phenomena are common, resulting in the formation of sinkholes, sinkholes, saucers, and lakes. The emergence of thermokarst forms continues to occur today; This is evidenced by trunks and stumps immersed in lakes, flooded trees and shrubs, and cracks in the ground. Spotted tundras form on smooth, flat watersheds or on slightly inclined slopes. Spots devoid of vegetation reach a 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 vigorous cyclonic activity and cooling in winter of the neighboring territory - the region of the Asian anticyclone.

Winter in the Western Siberian tundra is more severe than in Europe, but less frosty than east of the river. Yenisei. Average January temperatures are -20-30°. Winter weather types prevail from mid-October to early May. Average monthly wind speed in the tundra -7-9 m/sec, maximum - 40 m/sec, which at low temperatures, sometimes reaching -52°, creates greater harshness of the weather. Snow cover lasts for about 9 months (from half of October to half of June). Under the influence of strong winds, the 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 ones from Central Siberia.

In summer, arctic air invades the entire territory, but the process of its transformation is still poorly 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 precipitation - from 230 mm in the northern part up to 300 mm in southern part. Maximum precipitation falls in the summer, mainly in the form of long-term drizzling rains; showers with thunderstorms are rare. Due to the lack of heat, frequent precipitation, weak evaporation and the presence of permafrost in places, the soil is very swampy and the relative humidity is very high. Evaporation on the coast - 150 mm, and on the southern border of the forest-tundra there are about 250 mm. The tundra and forest-tundra zone is characterized by an excessively humid climate.

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

Soil formation occurs in Quaternary parent rocks - clay-sandy deposits of glacial and marine origin. Soils are formed under conditions of low air and soil temperatures, low precipitation, insignificant drainage of the territory and lack of oxygen. All these conditions lead to the development of gley-bog type soils. However, the combination of local natural components creates diversity in the formation of soil cover. The most common are tundra gley and peat-bog soils, which form under conditions of high moisture. On sands where there is no permafrost or where it lies at great depths, there is no swamping and weakly podzolic soils develop. In the forest-tundra, the process of formation of podzolic soils is more pronounced: they form 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, changes in climate, soil formation and vegetation cover are observed.

B. N. Gorodkov identified the following subzones of the tundra: 1) 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 spotted tundra. Its vegetation is very sparse and settles only in hollows and cracks surrounding bare patches of soil. The vegetation cover is completely free of sphagnum mosses and shrubs. The latter occasionally enter from the south along river valleys. The species composition is poor; the most typical species are: foxtail( Alopecurus alpinus), sedge ( Carex rigida), moss ( Polytrichum strictum), sorrel ( Oxyria digyna), meadowweed ( Deschampsia arctica).

Typical tundra occupies the middle and southern parts of the Yamal and Gydansky peninsulas and the northern part of the Tazovsky. The southern border of the tundra lies north of the Arctic Circle. The vegetation of a typical tundra is varied. Mosses, lichens, herbs 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), bush willow( Salix glauca, S. pulchra), blueberries ( Vaccinium uliginosum); medium - herbaceous - sedge(Sa 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 is lushpaynikovo-moss. It consists of lichens: alectoria( Alectoria), cetraria ( Cetraria), reindeer moss ( Cladonia rangiferina), mosses - hypnum and sphagnum( Sphagnum lenense).

Typical tundra varies in individual areas: moss tundra forms on moist clay soils. Lichen tundra develops in elevated loamy and sandy areas. In areas of strong wind activity there are small areas of patchy clay tundra. In spring and summer, moss tundras provide good grazing land for deer, which eat cotton grass, shrub foliage, and various grasses. In the ravines, on the slopes of southern exposure, tundra meadows consisting of forbs develop. The meadows are used as summer pastures for deer.

Riverine thickets of willow bushes are moving north along river valleys. Compared to other plant groups, shrubs develop in conditions of less swampiness, thicker snow cover and faster and deeper thawing of the active soil layer.

In the south of the typical tundra, shrubs begin to dominate 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 tundras. The widespread development of shrub groups in the more southern parts of the tundra is explained by weakened wind activity in winter, thicker snow cover and more precipitation.

The tundra is gradually replaced by forest-tundra. In the northern part of the forest-tundra, small areas of open forest and crooked forest appear, which increase to the south and turn 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 the wind and well heated. The forests consist of larch and spruce. Dwarf birch and scrub alder are common under the forest canopy. The ground cover consists of sphagnum mosses, forming peat bogs with a lumpy surface. In dry sandy places, where there is a fairly thick snow cover, the soil is covered with lichens, mainly reindeer moss. The main types of soils are gleyic-podzolic.

The slopes of river valleys and terraces in summer are covered with lush, variegated meadows consisting of buttercups, fireweeds, 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 animal species is the domestic reindeer. He gets his food all year round: moss, or reindeer moss, berries, mushrooms, leaves and grass. Large reindeer herding state and collective farms have been created 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 arctic 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 the 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, and the foliage of plants. It itself serves as food for many mammals and bird predators. In the tundra of Western Siberia, two types of lemmings are found: Ob and ungulate.

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

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

In winter, the tundra is poor in birds: few of them remain to live in harsh climatic conditions. To the south, geese, ducks, swans, and the red-breasted goose fly away, nesting only in the tundra and forest-tundra, from the river. Ob to the river Yenisei. The peregrine falcon is also a migratory bird and 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, white partridge, and lemming burrow into the loose, fine snow. Compacted snow facilitates easy movement of tundra animals: for example, the arctic fox walks freely on the crust. In the partridge, the claws lengthen and by autumn the fingers are covered with a thick 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 deeply. When there is loose, deep snow, the white partridge sinks into it up to its belly and can only wander around the bushes with great difficulty. Areas with little snow are most favorable for deer, as they can easily reach 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 the soil from freezing by accumulating snow in the fields, and adding manure to 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. w.

The relief of the taiga zone was created by the accumulative activity of continental glaciation, glacial melt 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, modified by the activity of melted glacial waters of the retreating maximum glacier and partially melted glacial waters of the last glaciations.

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

The forest zone is part of the West Siberian continental climatic region. Continental temperate air dominates over the entire territory all year round.

Winter 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 for 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 lasts from mid-October to mid-May.

In summer, air flows into the forest zone of the West Siberian Plain from the north. 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 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).

Amount of precipitation - 400-500 mm, maximum - in summer. Over the entire territory at the same latitudes in the European part of the Soviet Union, more precipitation falls 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 within approximately 61-62° N. w. Under the riverbeds, the top of the frozen soil is much lower than on the watersheds, and under the Ob and Yenisei rivers it is not found at all.

Groundwater is fresh and lies close to the surface (at a depth of 3-5 to 12-15 m). Extensive sphagnum bogs have developed along the watersheds. The rivers have slight slopes and flow slowly in wide, strongly meandering channels. This is associated with the weak mineralization of river waters (50-150 mg/l) and poor aeration of stagnant waters. Deadlocks form in rivers. The essence of the death phenomena comes down to the following: groundwater and swamp water containing a small amount of oxygen and a lot of organic substances enter the Ob and its tributaries. With the formation of ice on rivers, the supply of oxygen from the air stops, but swamp water continues to flow into the rivers and absorb oxygen. This leads to oxygen deficiency and causes massive fish deaths. The overseas zone occupies an area of ​​about 1,060,000 in the basin of the Ob and Irtysh rivers. km 2. To the north, the overseas zone advances to the lower reaches of the river. Ob and even extends to the Gulf of Ob.

Soils. Soil formation occurs in conditions of flat, heavily swampy terrain, covered with taiga vegetation. The parent rocks are diverse: glacial, fluvioglacial, lacustrine and eluvial-deluvial consist of sandy, sandy-clayey and boulder-free sediments, as well as loess-like loams. The forest zone of the plain is characterized by podzolic, podzolic-swamp and peat-swamp soils.

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

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

The strip of woodland consists of Siberian larch( Larix sibirica) with a touch of 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. Forests are sparse, treeless areas are occupied by small swamps and tundra formations.

2. The northern taiga subzone is characterized by an open forest stand and a wide distribution of flat-hilly sphagnum bogs. The forests consist of larch with some spruce, birch, and cedar. In the northern part of the subzone, in some places they are clean, without impurities. Larch forests are spread over 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. Typical shrubs and herbs include: bearberry, crowberry, lingonberry, sedge (Carex globularis ) , horsetails ( Equisetum sylvaticum, E. pratense); the undergrowth consists of birchberry, wild rosemary and blueberry. These forests occupy large areas closer to the Yenisei and Ob rivers. The middle part of the northern taiga is dominated by swamps.

3. Subzone of the middle taiga. 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 density and gloominess. Dark coniferous forests are distributed unevenly within the subzone. The most significant massifs are concentrated in the middle and eastern parts. To the west of the Ob and Irtysh rivers, pine forests with sphagnum bogs predominate. Forests of spruce and cedar are found mainly in river valleys. They have varied grass cover and dense thickets of Siberian pigweed shrubs (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, linden is found( Tilia sibirica) with herbal companion - whine( Aegopodium podagraria). The middle and southern taiga is classified as urman-marshy taiga.

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

Pine forests grow on the sands; They occupy the largest area in the river basin. Tobola.

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

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

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

Birds nest in the taiga. Cedar forests are a favorite place for nutcrackers; The Siberian crossbill is more common in larch forests; the three-toed woodpecker taps in spruce forests. There are few songbirds in the taiga, so they often say: the taiga is silent. The most diverse bird kingdom is found in birch-aspen burnt areas and on river banks; Here you can find waxwings, finch, long-tailed bullfinch, and ruby-throated nightingale. On reservoirs - geese, ducks, waders; A white partridge wanders through the moss swamps far to the south, almost to the forest-steppe. Some birds fly to the West Siberian taiga from the southeast. Many of them winter in China, Indochina, and the Sunda Islands. The long-tailed bullfinch, ruby-throated nightingale, etc. fly there for the winter.

Of commercial importance are: squirrel, fox, ermine, and weasel. Birds include 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 topography, on saline parent rocks, at a considerable distance from the oceans, in a more continental climate. Therefore, their appearance is sharply different 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 sediments, ancient alluvial and fluvioglacial

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

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

The modern relief of the forest-steppe and steppe was greatly influenced by ancient streams, which formed wide runoff depressions crossing the Priobskoe plateau, the Kulunda, Barabinskaya lowlands and other territories. The ancient hollows are directed from northeast to southwest. The bottoms of the hollows are flat, composed of loose sediments. The interfluves between the runoff depressions are elongated in the same direction as the depressions 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 they still have patches of snow and the watershed areas are already free of snow. One of the features of the steppe and forest-steppe zones of Western Siberia should be considered the abundance of lake basins. They are common on flat watersheds and river valleys. The largest of them are the lakes of the Barabinsk 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 small. The largest lakes include Seletytengiz. There are many small lakes on the Ishim-Irtysh inclined plain and the Ishim Upland.

Thousands of lakes occupy depressions in ancient hollows; they represent 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 rainwater formed as a result of surface runoff. For many reservoirs, especially large ones, ground nutrition is also essential.

Lakes periodically change their level, and therefore their outline and their water supply: they either dry out or fill up again with water 1 . Changes in lake levels are associated with fluctuations in climatic conditions: with the ratio of precipitation and evaporation. Human activity also has some influence on changes in lake levels: building dams, laying ditches, burning birch stakes, and mowing reed thickets along the banks. For example, in the Barabinskaya, Kulundinskaya and Ishimskaya steppes, after fires, new lakes with a depth of up to 1.5-2 m. After mowing down the coastal thickets of reeds and reeds, some of the fresh lakes in the Kulunda steppe turned into salt lakes, since snowdrifts stopped accumulating on them in winter, which led to a sharp reduction in one of the most important sources of their nutrition.

Over the past 250 years (since 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 precipitation and temperature conditions, cycles of high and low precipitation activity, warm and cold periods were identified.

Thus, the dependence of lake level fluctuations on fluctuations in 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 lakes in the Chany group have been repeatedly recorded.

The steppe and forest-steppe are dominated by lakes containing brackish water (Chany, Ubinskoye, etc.). Lakes are divided according to their chemical composition into three types: hydrocarbonate (soda), chloride (actually salty) and sulfate (bitterly salty). In terms of reserves of salt, soda and mirabilite, the lakes of Western Siberia occupy one of the first places in the USSR. The 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 being more continental, manifested in an increase in the annual amplitude of air temperature and 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°

Winter sees the least amount of precipitation. 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 is small (40-30 cm) power and is distributed unevenly over the surface of the forest-steppe and steppe.

In 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 reaches + 15° in May, 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 ten days of May the average daily temperature exceeds +10°.

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

air reaches +30°, relative humidity below 15%. Dry winds are formed during southern winds that arise on the western edge 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 65-70% in the forest-steppe.

Droughts and hot winds occur more often 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 hot winds are caused by the penetration and intense heating of Arctic air masses and the invasion of hot and dry air from Central Asia. Every year, especially in dry years, dust storms occur in the steppes from April to October. Their greatest number occurs in May and early June. More than half of the annual precipitation falls in 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. In October, precipitation increases. Moisture accumulates in the soil in autumn, since evaporation is insignificant at this time. In the northern part of the steppe, snow cover appears at the end of October. Stable frosts set in from November.

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 drier 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 are dominated by primary flat, poorly drained plains, covered with extensive swamps, numerous fresh and salt lakes, saucers, wide hollows and ridges.

The gully-gully network is less developed than on the Russian Plain. However, the manifestation of gully activity is observed in all natural zones of the West Siberian Plain, and especially on sloping plains and plateaus adjacent to the Urals and Altai, and along the valleys of the Ob and Irtysh rivers. In the steppes, nivation gullies are widely developed, the formation of which is caused by the accumulation of snow under the influence 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, in conditions of insufficient moisture. The zonal soils of the forest-steppe of Western Siberia are meadow-chernozem, leached and podzolized chernozems.

Salt marshes, 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 appearance of malts.

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

The forest-steppe of the West Siberian Plain is called birch forest-steppe. In the northern part of the forest-steppe, the forest cover of the territory is about 45-60%. Isolated forests of birch are called birch tufts. The tufts consist of downy birch with an admixture of aspen, warty birch and willow in the undergrowth. The grass cover in the groves is formed by steppe and forest species. Of the forests, stoneweed is typical( Rubus saxatilis), purchased ( Polygonatum officinale) ; from bushes - currants ( Ribes nigrum). Pine is the most common coniferous species in the forest-steppe. Pine forests occupy sandy and sandy loam areas and extend along the floodplain terraces of valleys south to the steppe zone. Under the pine canopy, taiga plant groups move to the south - the pine's companions: sphagnum bogs, on which grow: wintergreen, lingonberries, blueberries, cranberries, sundews, cotton grass, sedges and orchids. In 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 solodized peaty soils and solonchaks. But at the same time, steppe species (fescue and steppe timothy) are common in the grass cover of southern pine forests.

Steppe areas have a dense herbaceous cover, consisting of typical meadow rhizomatous grasses: reed grass, meadow grass, steppe timothy. The most common legumes are clover and peas, and the asteraceae are meadowsweet.( Filipendula hexapetala), Solonchak forms appear on salt marshes.

When moving south, the grass cover of the steppes thins, the species composition changes - steppe species begin to predominate, and meadow and forest species are noticeably reduced. Among the cereals, turf xerophytes predominate: fescue( Festuca sulcata) and thin-legged ( Koeleria gracilis), feather grasses appear( Stipa rubens, St. capillata). Of the forbs, the most typical are alfalfa( Medicago falcata) and sainfoin ( Onobrychis arenaria). Salt marsh plants are beginning to be found more often: licorice, solyanka, large plantain, astragalus. There are fewer birch trees, and the area's forest cover is only 20-45%.

In the Western Siberian forest-steppe, as already noted, wetlands called borrow areas are widespread. The lands are covered with marsh vegetation: sedge, reeds, reeds, cattails. They occupy low interfluve spaces and are the final stage of overgrowing reservoirs. Loans are especially abundant in the Barabinsk steppe. In addition, moss-sphagnum swamps overgrown with rare, oppressed pine are common in the Western Siberian forest-steppe. They are called ryams. Pine forests, fields and ryams in the modern dry climate should be considered intrazonal plant groups that 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 sheep, fescue, thin-legged sheep, desert sheep ( Auenastrum desertorum), timothy grass Forbs are less abundant than in the forest-steppe steppes and consist of yellow alfalfa, bedstraw, speedwell, sleep grass, cinquefoil, and wormwood.

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

The southern steppes of the West Siberian Plain are dominated by turf grasses: fescue, tonkonogo and feather grass. Abundant rhizomatous steppe sedge( Carex sypina). Among the herbs, xerophytic species predominate, for example: wormwood ( Artemisia glauca, Alatifolia), onion ( Allium lineare) , Adonis ( Adonis wolgensis), gerbils ( Arenaria graminifolia); many Siberian forms that do not extend into the European steppe: iris ( Iris scariosa), goniolimon ( Goniolimon speciogum) and etc.

The grass cover is sparse, and the turf cover of the steppes reaches 60-40%. Along the shores of lakes, on salt licks, solonetzic species, such as sea wormwood, grow. In depressions with close groundwater and along the shores of salt lakes, salt marshes with typical halophytic vegetation predominate: saltwort, saltmarsh barley, licorice.

In the steppes, along river valleys, hollows of ancient drainage, and logs, there are thickets of willow and birch; along the sands there are patches of pine forests (green moss, lingonberry and white moss with a large number of steppe species). So, for example, in the river valley. Irtysh on the sandy right-bank terrace, vast 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 thick, lush grass stand of wheatgrass, steppe alfalfa, and water-grass; Closer to the water, marsh associations of reeds and sedges dominate. Wet floodplain meadows are an example of a sharp contrast with the dry feather grass-fescue steppes, which quickly burn out in the summer.

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

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

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 forest-steppe fauna includes forest and steppe species. Along the groves and ribbon pine forests, 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 Kulundinsky pine forests, along with steppe species - garden bunting, field pipit, woolly jerboa - taiga species of animals live: squirrel, flying squirrel, capercaillie.

Animals living in the tundra are found in the forest-steppe and steppe. They belong to the 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. Chans. Nowhere does it penetrate as far to the south as in the Western Siberian steppes. The laughing gull, typical of the tundra zone of Taimyr, is found on lakes in the forest-steppe and steppe.

The fauna of the forest-steppe and steppe has many similarities in 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, ground hare - the largest of the jerboas ( Allactaga gaculus); Djungarian hamster and red-cheeked ground squirrel are often found ( Citellus erythrogenus). The steppe is characterized by the small or gray ground squirrel and marmot (baibak).

The following predators live in the steppe and forest-steppe: wolf, fox, steppe ferret. A small fox - a corsac - comes into the steppe from the south. Typical taiga species are found in the forests of the forest-steppe: weasel, weasel, and ermine.

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

Among the birds of the forest-steppe there are many European forms (common bunting, oriole, chaffinch). In the steppe areas, common and Siberian larks are numerous, and little bustards and bustards are occasionally found. In the southern steppes there are more of them: larks - four species (the small or gray lark penetrates from the desert into the steppe). Demoiselle crane and steppe eagle are also found. Grouse, gray and white partridges serve as winter fishery items.

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

There are four physical-geographical 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 zoning. Physiographic 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 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-plant differences, and is therefore divided into physical-geographical regions.