Peculiarities of the relief of the territory of the West Siberian Plain. Rivers and lakes of the plain

The West Siberian Lowland is a single physical-geographical region, consisting of two flat bowl-shaped depressions, between which lie latitudinally elongated elevations (up to 175-200 m), united orographically into the Siberian ridges.

The lowland is delineated by natural boundaries on almost all sides. In the west it is clearly delimited by the eastern slopes of the Ural Mountains, in the north by the Kara Sea, in the east by the valley of the Yenisei River and the cliffs of the Central Siberian Plateau. Only in the south is the natural boundary less pronounced. Gradually rising, the plain here passes into the adjacent hills of the Turgai plateau and the Kazakh hillocks.

The West Siberian Lowland occupies about 2.25 million km 2 and has a length from north to south of 2500 km, and from east to west (in the southern widest part) 1500 km. The exceptionally flat relief of this territory is explained by the leveling of the complex folded foundation of the West Siberian Platform with a thick cover of Meso-Cenozoic sediments. During the Holocene, the territory experienced repeated subsidence and was an area of ​​accumulation of loose alluvial, lacustrine, and in the north - glacial and marine sediments, the thickness of which in the northern and central regions reaches 200-250 m. However, in the south the thickness of Quaternary sediments drops to 5-10 m and the modern relief clearly shows signs of the impact of neotectonic movements.

The peculiarity of the paleogeographical situation lies in the strong watering of the territory inherited from the Holocene and the presence at present of a huge number of residual reservoirs.

Large modern landforms Western Siberia represent morphostructures created by recent movements of the earth's crust. Positive morphostructures: hills, plateaus, ridges - have a more dissected topography and better drainage. Negative morphostructures are dominant for the relief of the territory - plains covered with a thickness of loose layered sediments, often gleyed to great depths. These properties impair the water permeability of the strata and inhibit groundwater flow.

The flatness of the territory determined the special nature of the hydrographic network: low water flow rates and significant tortuosity of the riverbeds. The rivers of Western Siberia have a mixed supply - snow, rain, ground, with a predominance of the first. All rivers are characterized by long spring floods, often turning into summer ones, which is explained by different times of river opening in different parts of the catchment areas. Flood waters, spreading over many kilometers, are an important factor in the extremely high water supply of watersheds, and rivers practically do not play their drainage role during this period.

Thus, the combination of physical and geographical factors that favorably influence the swamp formation process determined the intensity of the formation and accumulation of huge reserves of peat and its widespread distribution throughout the territory. West Siberian Plain peat deposits.

The vegetation cover of peat deposits in the West Siberian Lowland has not been studied in sufficient detail. The tree layer of forested peatlands here is much richer in species composition due to species characteristic of the taiga forests of Siberia, such as cedar, fir, and larch. Usually they, together with birch, spruce, and pine, make up the forest of swamps in various combinations and quantities. Almost pure stands of birch on peat bogs are quite common and, under appropriate conditions, are found in all peat-bog areas of the West Siberian Lowland. Pure thickets of willow are noted on the lowland peat bogs of the floodplains.

In the shrub layer of the vegetation cover of Western Siberian swamps, such a representative of the Siberian flora as Salix sibirica is found, but the European species Calluna vulgaris is not reflected in it. Representatives of the Siberian flora were also noted in the herbaceous layer: Carex wiluica, Cacalia hastata, Ligularia sibirica. Carex globularis, found in the European part of the Union as part of the vegetation of swampy spruce forests, in Western Siberia it has expanded its habitat and is found in large numbers on typical high-moor peat bogs. Sph. rubellum and Sph. cuspi datum - typical inhabitants of high peat bogs in the northwestern region of the European part of the Union - are rarely found in the moss cover of peat bogs of the West Siberian Lowland. But in much greater quantities and in more southern latitudes, Sph are distributed here in the moss cover of swamps. lindbergii and Sph. congstroemii, which are typical for peat bogs in the Arkhangelsk region and are rare in peat bogs in the middle zone. Sometimes, in the ridge-lake areas of the Vasyugan watershed peatlands, Cladonia and Cetraria form continuous patches, and up to 12 species of Cladonia are found in this regenerative complex.

Of the plant phytocenoses of the West Siberian Lowland, it is necessary to note the grass-sedge plant, which covers significant areas in the edge areas of the fields (in conditions of some soil salinity). It includes reed grass (Scolochloa festucacea), reed grass (Calamagrostis neglecta), Carex omskiana, C. appropinquata and C. orthostachys. Peat bogs are characterized by birch (up to 15-20 m in height) and conifers: spruce, cedar, pine, larch; in the undergrowth, along with willows (Salix sibirica, S. pentandra), black currant, rowan, bird cherry; in the shrub layer - bog myrtle, lingonberry, blueberry, cloudberry. The grass stand is rich in species and develops luxuriantly; it is dominated by C. caespitosa, other sedges include C. globularis, C. disperma, and taiga plants (Equisetum silvaticum, Cacalia hastata, Pyrola rolundifolia) also grow in the forbs along with marsh plants. Elements of taiga flora are also observed in the moss cover: on hummocks Sph. warnstorfii - Pleuroziumschreberi and Hylocomium splendens, in inter-tussock depressions - Thuidium recognitum, Helodium blandowii, on the slopes of hummocks - Climacium dendroides. In the depressions between hummocks in Sogras one can often observe efflorescence of iron.

Most often, sogras cover the edge areas of low-lying marshy swamps of terraces above the floodplain along the channels of the Ob, Irtysh, Chulym, Keti, and Tym rivers. From the outside they gradually turn into swampy forests, towards the center of the peat bog - into a forest complex phytocenosis.

In the West Siberian Plain, borrowings predominate in the Ishim peat-bog region between the Ishim and Tobol rivers in their middle reaches. Here they adjoin the lakes or surround them in a continuous ring. Huge areas are sometimes occupied by land in lowlands that are no longer connected with lakes, but bear the features of former channels between lakes.

Zaimishchno-ryam peatlands are often found in the eastern part of the South Barabinsk peat-bog region, where they are confined to lakes or flat depressions in which surface water stagnates for a long time. Among the fields there are scattered raised convex peat bogs, which occupy a small area compared to the fields. These are the well-known “ryams”. During the growing season, a variable water-mineral regime is created in the fields: in the spring and in the first half of summer they are flooded with fresh deluvial melt water, and often with river hollow water; in the second half of the growing season, loans dry up in a larger peripheral area, and favorable conditions for capillary rise of saline soil-groundwater to the surface and efflorescence of salts (Ca, Cl and SO 3) is usually observed on the surface.

The area of ​​the borrowing area can be divided into: a zone of constant moisture with relatively fresh waters (the central part of the borrowing area, the banks of lakes and river channels) and a zone of variable moisture, where both the degree of water content and the degree of mineralization of the feeding waters are variable (peripheral parts of the borrowings).

The central parts of the fields are covered with reed phytocenosis, in which the main background plants are reed, reed (Scolochloa festucacea), reed grass, sedge (C. caespitosa and C. wiluica). The phytocenosis includes Carex omskiana, C. buxbaumii, watchwort, and bedstraw (Galium uliginosum) as admixtures. Among the components of the reed phytocenosis, reed, reed grass, Carex caespitosa and C. buxbaumii are salt-tolerant plants.

In the zone of borrowings where constant moisture begins to give way to variable moisture, under conditions of some salinization of the substrate, a gradual thinning of reed thickets and the introduction of sedges (C. diandra, C. pseudocyperus), cattail and reed grass are observed. The sedge-reed phytocenosis is characterized by isolated scattered bushes of birch (B. pubescens) and willow (S. cinerea).

Along the periphery of the fields in the zone of variable moisture, reed grass (Scolochloa, festucacea), which in the conditions of Baraba is an indicator of mixed chloride-sulfate salinity, displaces reed grass from the plant cover, and here a grass-sedge phytocenosis arises mainly from reed grass, Carex omskiana, C. appropinquata and C. orthostachys with a small participation of the same reed grass.

The formation and development of ryams (oligotrophic pine-shrub-sphagnum islands) occurs in isolation from saline soils in both horizontal and vertical directions. Insulation in the horizontal direction is a deposit of loans; insulation in the vertical direction is a layer of reed peat with an average degree of decomposition of 22-23%, underlying the upper ryam deposit. The thickness of the reed peat is 0.5-1.5 m, the thickness of the upper deposit is 0.5-1 m. The upper deposit is composed of weakly decomposed fuscum peat with a degree of decomposition of 5-20%. The stump content of the sphagnum deposit is low and falls from upper layers to the lower ones.

The surface of the ryam is sharply convex with asymmetrical slopes. Under the tree layer of pine, a shrub layer and a moss cover of Sph are developed. fuscum with impurities Sph. angustifolium and Sph. magellanicum.

The largest ryams up to 1000-1500 hectares (Bolshoy Ubinsky and Nuskovsky) are found in the northern and middle parts of the forest-steppe zone. Usually the area of ​​ryams is 100-400 hectares, sometimes 4-5 hectares (small ryams of the Chulym region).

Peat deposits in Western Siberia are extremely diverse in terms of the conditions of formation and development, qualitative and quantitative indicators of the deposit, vegetation cover, distribution patterns and other factors, the changes of which can be traced to a fairly clear pattern, closely related to natural latitudinal zoning. According to this principle, 15 peat-bog areas have been identified in Western Siberia.

The far north of the West Siberian Lowland occupies area of ​​arctic mineral sedge bogs. It geographically corresponds to the West Siberian subzone of the Arctic tundra. The total swampiness of this territory is almost 50%, which is a consequence of the waterproof frozen layer located close to the surface, the excess of precipitation over evaporation and the flatness of the country. The thickness of the peat layer does not exceed several centimeters. Peatlands with deep deposits should be classified as relics of the Holocene climatic optimum. Polygonal and flat moss-sedge bogs are common here.

The wide distribution of eutrophic moss-sedge bogs with a flat surface (up to 20-25% of the total area) is noteworthy. Carex stans or Eriophorum angustifolium dominate here, with a moss carpet of Calliergon sarmentosum and Drepanocladus revolvens.

In river valleys among sedge bogs there are mounds covered with Sph. warnstorfii, Sph. lenense, Dicranum elongatum and lichens. Flowering plants include abundant thickets of Betula nana and Rubus chamaemorus.

Along the shores of bays and the Kara Sea there are coastal swamps that are flooded during surge winds sea ​​water. These are largely brackish marshes with grasses (Dupontia fisonera), sedges (Carex rariflora, etc.) and Stellaria humifusa.

Mossy tundras are especially characterized by the abundance of Eriophorum angustifolium on the moss cover of Aulacomnium turgidium, Camptothecium trichoides, Aulacomnium proliferum, Dicranum elongatum, and Ptilium ciliare. Sometimes the swampy tundra is dominated by sedges (Carex stans, Carex rotundata) with a similar composition of the moss cover and the participation of sphagnum mosses.

Located further south area of ​​flat-hilly bogs. This zone geographically corresponds to the tundra. The swampiness of the zone is high (about 50%).

Flat-hilly peatlands represent a mosaic complex of hillocks and hollows. The height of the mounds ranges from 30 to 50 cm, rarely reaching 70 cm. The area of ​​the mounds is up to several tens, less often hundreds of square meters. The shape of the mounds is lobed, round, oval, elongated or ridge-like; the tops of the mounds are occupied by lichens, mainly Cladonia milis and Cladonia rangiferina. Cetraria nivalis, C. cucullata, Cladonia amanrocraea are less common. The slopes of the hillocks are covered with green mosses. Aulacomnium turgidium, Polytrichum strictum, Dicranum elongatum are abundant. Among the flowering plants, the strongly oppressed Ledum palustre and Rubus chamaemorus grow in clusters. Between them are fragments of dicrane-lichen associations. The hollows are heavily watered with a continuous carpet of sphagnum mosses from Sph. lindbergii, Sph. balticum, Sph. subsecundum, Sph. Jensenii. Drepanocladus vernicosus is less common in hollows, Drepanocladus fluitans is common, Carex rotundata is common, Carex chordorrhiza is less common, Cephalozia fluitans sometimes grows. Along with swamps, wetlands are widespread, which are swampy shrub tundras with Betula papa and willows, sometimes with Ledum palustre, swampy moss tundras with Betula papa and Ledum palustre, hummocky tundras with Eriophorum vaginatum.

Area of ​​hummocky bogs occupies the northern part of the forest zone and the southern forest-tundra. The swampiness of the area is high. The mounds are found singly, but more often they are located in groups or ridges 1-2 km long, up to 200 m wide. Single mounds have a height of 2-2.5 m, soil mounds 3-5 m, ridge mounds reach a height of 8-10 m. Diameter the bases of the mounds are 30-80 m, the slopes are steep (10-20°). Inter-hill depressions are elongated, occupied by cotton grass-sphagnum and sedge-sphagnum oligotrophic or eutrophic hollows, sometimes with small lakes in the center. The surface of the largest mounds is broken by cracks up to 0.2-0.3 m deep. At the base of the mounds, sphagnum mosses grow and a layer of shrubs, mainly Betula papa, is developed. Higher up the slope, lichens predominate. They are also typical for flat peaks, often subject to wind erosion.

The hummocky peatlands are topped with peat up to 0.6 m thick, under which lies a highly ice-saturated mineral core consisting of ice and loamy, silty-loamy, less often sandy loam material. The mineral core, in addition to ice-cement and its individual crystals, contains numerous ice layers, the thickness of which reaches several tens of centimeters and usually increases downwards, the number of layers also decreases downwards.

North Ob peat-bog region It is a poorly drained lacustrine-alluvial plain composed of medium- and fine-grained sands with clearly defined horizontal layering.

The region is characterized by extremely high swampiness. Peat deposits occupy more than 80% of the territory; form complex systems, covering flat interfluves and high river terraces. Dominated by raised convex, heavily watered sphagnum peatlands with ridge-lake complexes on the flat tops and ridge-lake-hollow complexes on their slopes.

Areas with well-drained areas of peat bogs are insignificant and are confined to the territory with the highest surface elevations. Fuscum and pine-sphagnum phytocenoses with a large number of different lichens are widespread here.

Lowland peat deposits are located mainly on the first terraces above the floodplain of large rivers.

Deposits of high peat bogs are shallow, on average about 2 m. poorly decomposed fuscum, complex, and hollow types of structure predominate.

Kondinskaya peat-bog region It is a vast alluvial and lacustrine-alluvial plain composed of layered sandy and clayey deposits. For the left bank of the river. Konda and the right bank of its lower reaches are characterized by the presence of rugged topography. The region is characterized by extremely high water content. A significant part of the Kondinsk region is confined to an area of ​​intense tectonic subsidence and is therefore characterized by the predominance of accumulation processes and the dominance of poorly drained swamps. Only the western part of the region, where denudation processes predominate, is characterized by low swampiness. The river beds are weakly incised. In the spring, the hollow waters of these rivers overflow widely and do not enter the banks for a long time. Therefore, river valleys are swamped over a large area; Near-terrace swamps are heavily flooded during high water. For the river basin Konda is characterized by the predominance of upland ridge-lake, ridge-lake-hollow and ridge-hollow peat deposits.

Lowland, sedge, reed, reed, birch-reed peat bogs are confined to river beds.

Transitional sedge-sphagnum, woody-sphagnum and sphagnum bogs are found on low terraces and in places where they join into bog systems. There are also complexes formed along the lines of surface intra-fallow flow of swamp waters.

The gradual tectonic subsidence of the surface affects the extremely high water content of the territory, which contributes to the intensive development of regressive phenomena in the swamps, the destruction of the sphagnum turf of ridges, hollows, an increase in the area of ​​hollows due to the degradation of ridges, etc.

Among the swamps there are a huge number of lakes. Some of them are completely peated, but most have been preserved open mirror water among peaty shores.

In the river basin Kondy, the main type of peat deposit is raised, in which a complex type of structure predominates, which is due to the dominance of ridge-hollow complexes. Fuscum, Scheuchzeria-sphagnum and Magellanicum deposits are somewhat less common.

Transitional types of deposits make up peat bogs mainly on the second terrace of the river. Konda and its tributaries, and are also found along the edges of high-moor peat deposits, around mineral islands, or are confined to mesotrophic grass and moss swamps. The most common type of deposit is transitional swamp.

Low-lying deposits are found in river floodplains, forming narrow strips confined to overgrown rivers of high-moor swamps.

Analysis of spore-pollen diagrams dates the Kondin peatlands to the early Holocene. Peat bogs are of ancient Holocene age, the depth of which exceeds 6 m.

Middle Ob peat-bog region It is a lacustrine-alluvial and alluvial plain, composed on the surface mainly of cover deposits, underlying either lacustrine layered clays, or light loams, siltstone and sandy strata.

The territory is characterized by the development of progressive and predominant accumulation processes, which determines the predominant distribution of poorly drained swamps and constantly swampy forests. Only in the north of the region, where denudation processes predominate, are relatively drainable swamps found.

The region is characterized by the dominance of raised sphagnum bogs with ridge-lake-hollow and ridge-hollow complexes. The edges of swamps located at lower hypsometric levels (within the first floodplain terraces and floodplains of small lakes) are usually eutrophic or mesotrophic. The deposit of their central parts is represented by fuscum and complex types of structure and has a depth of 4-6 m.

Large peatlands on first-order watersheds are divided into three categories. On flat, level plateaus of watersheds, peatlands have a strongly convex surface with steep slopes and a flat central part. The difference in the levels of the center and edges is 4-6 m. The central main part of such peat bogs is represented by a fuscum deposit or a complex raised peat and bears lake-denudation or ridge-lake vegetation complexes on the surface, and ridge-hollow vegetation on the slopes.

On one-sidedly elevated watersheds with a gently concave asymmetrical surface, raised peat bogs give a drop in surface elevations from an elevated slope to a lower one.

The thickness of the peat layer also decreases in the same direction. The deepest part of such peatlands is usually represented by a fuscum type of structure with a ridge-lacustrine complex of vegetation on the surface. In the direction to the opposite slope of the watershed, the fallow becomes a complex upland with a ridge-hollow complex in the vegetation cover. The shallow peripheral area with a transitional swamp deposit bears the vegetation of sphagnum swamps on the surface.

On symmetrical watersheds with a flat plateau, sometimes raised peat bogs with a complex surface line are observed: two evenly raised caps are separated by a trough up to 2-3 m deep. Such peat bogs are composed mainly of raised fuscum or complex peats. On the gangs, the vegetation cover is represented by a ridge-lake complex, in the trough area - by sphagnum swamps, often giving rise to rivers. A. Ya. Bronzov explains the formation of such massifs by the mergers of two (sometimes several) peat bogs with separate pockets of swamping. In some cases, the formation of a deflection could occur during the breakthrough and outpouring of internal waters and partly the most liquefied and plastic peats from the peat bog, followed by subsidence of the peat deposit.

On second-order watersheds, peatlands occupy interfluves that have undergone significant dissection. The depth of the erosion incision here reaches 20-30 m. This is the nature of the watersheds between large rivers flowing approximately parallel to each other in their middle reaches.

In upland conditions, large peat deposits of the raised type with a predominance of fuscum deposits and with ridge-lake and ridge-hollow vegetation complexes on the surface are located on the watersheds of occurrence.

Basically, the Middle Ob region, as well as the Vasyugan region located to the south, are territories of almost continuous swamps. Swamps here completely cover the watersheds of the first and second orders, terraces and river floodplains. Peatlands predominate, the total area of ​​which is about 90%.

Tym-Vakh peat-bog region occupies the Tym-Vakh interfluve and is composed of lacustrine-alluvial deposits. Geographically, it is confined to the Middle Vakh Plain and is characterized by high swampiness, which drops sharply in the northeastern part, where surface elevations reach 140 m.

Poorly drained raised sphagnum bogs with ridge-hollow-lake and ridge-hollow complexes dominate the watersheds and fourth terraces. They are also found on low terraces and are confined to the hollows of ancient drainage, where accumulation processes dominate. The deposit is characterized by great homogeneity and is composed of complex raised, Scheuchzerian and fuscum peat.

The deposit of transitional swamps is represented by transitional swamps and forest-swamp types of structure. Lowland peatlands are rare and are confined mainly to floodplains and low terraces. The deposit of lowland bogs is composed of sedge peat.

Ket-Tym peat-bog region occupies the area between the Keti and Tym rivers and extends east to the Yenisei. The watershed of the Ob and Yenisei has a clearly defined slope here with an increase in surface elevations to the east. The interfluve is composed of lacustrine-alluvial and deluvial deposits and is divided by a highly developed hydrographic network into a large number of small interfluves.

Due to the fact that the region is located within the contour of positive structures, the dominance of denudation processes determines the spread of well-drained swamps here. Regressive phenomena are less pronounced, there is a tendency for ridges to transgress, or ridges and hollows are in a state of dynamic equilibrium. The surface of the interfluve plateau has a clearly defined grivny relief. In some places, the dissected relief is leveled by a peat deposit 2-6 m deep - fuscum - or a complex type of structure on ridges, and in depressions - a transitional swamp or mixed swamp deposit with a lower horizon of low-lying sedge peat 1.5 m thick. Some ridges are ridges, towering above the peat deposit, filling the depressions between the ridges by 2-10 m. The width of the ridges is up to 5 km. They are composed of sandy sediments and are usually overgrown with taiga forest of pine, fir, cedar, and birch. The peatlands of the inter-ridge depressions are represented by transitional swamp and mixed swamp types of structure. On the upper part of the slope of the watershed towards the floodplain in the lower reaches of the Keti and Tym rivers there are often small round peat bogs of suffosion depressions (from 10 to 100 ha, rarely more) with transitional and upland deposits, less often with lowland deposits.

The slopes of the watersheds are eroded, weakly dissected or almost undivided by terrace ledges, cloak-like covered with peat deposits, forming large peat bogs that stretch for long distances along the course of both rivers. Closer to the bottom of the watershed, these peatlands are composed of lowland deposits, higher up the slope - transitional, and in the upper sections of the slope - highland. On them, often in the upper part of the slope, rather large lakes with sapropel deposits at the base are scattered among the upper deposits.

In the upper reaches of the Keti and Tym rivers, the narrow terraces of both river valleys are covered with peat. Narrow peatlands stretched along rivers are often composed of transitional deposits. Raised, poorly watered pine-shrub-sphagnum bogs are confined here to the watershed plain. The ridge-hollow complex is developed in the central parts of the largest peat bogs.

Lowland and transitional swamps are widespread on the first and partially on the second terraces of the river. Obi. Especially a lot of mesotrophic and eutrophic sedge, sedge-sphagnum, sedge-hypnum, tree-sedge bogs are found on the right bank terraces of the river. Ob, between the Ketyu and Tym rivers. The average thickness of raised bogs is 3-5 m, lowland 2-4 m. Raised bogs are composed of fuscum, complex and Scheuchzerian-sphagnum types of structure. The deposit of mesotrophic swamps is represented by transitional swamp and forest-swamp types of structure. The deposit of lowland bogs is composed of sedge peat.

In the modern vegetation cover of bogs with a transitional deposit, one can observe an admixture of oligotrophic species, indicating the transition of peat formation to the oligotrophic type stage.

A special feature of the Ket-Tym region is the significant distribution of transitional and lowland peatlands compared to other peat-bog areas of the forest zone, where exclusively raised bogs are dominant.

Tavdinskaya peat-bog region It is a flat, sometimes gently undulating plain, composed of lacustrine-alluvial and alluvial sandy-loamy deposits.

Geographically, its central part is confined to the southern half of the Khanty-Mansi Lowland, where accumulation processes predominate and the greatest swampiness occurs. Its northwestern edge extends into the Tavdo-Kondinskaya Upland, and its southern edge into the Tobol-Ishim Plain. The swampiness of the area is high. A significant area is occupied by poorly drained lowland peat deposits, the deposits of which are composed mainly of sedge and sedge-hypnum types of structure with a small participation of deposits of the forest-bog and forest subtypes. The thickness of the deposits is small (2-4 m), peat deposits 5 m deep are occasionally found. On flat watersheds, small peat bogs with deposits 6-7 m thick are common, often folded almost to the mineral soil with fuscum peat of a low degree of decomposition. There are many lakes on the surface of peat deposits, which at one time served as centers for the formation of most peat deposits in the region.

Vasyugan peat-bog region is a vast, slightly elevated plain experiencing tectonic uplift. It is composed of alluvial and subaerial sandy-loamy deposits. In the north and east of the region, lacustrine-alluvial deposits are common; in the south, subaerial loess-like loams extend into its boundaries. The location of the area to the contours of positive structures determines the distribution of relatively drained swamps. Poorly drained swamps occupy the Demyan-Irtysh interfluve and depressions of the Ob-Irtysh watershed, where accumulation processes are developed.

In general, the region is characterized by high swampiness (up to 70%), especially its western part, where swampiness in some places reaches 80%.

Raised sphagnum bogs with ridge-hollow-lake and ridge-hollow complexes are confined to the flat tops of watersheds. The slopes are less swampy. From the periphery, watershed raised sphagnum bogs are bordered by transitional sphagnum, grass-sphagnum areas of bogs. The deposit of raised bogs is composed of fuscum, complex, hollow and Scheuchzerian types of peat. The stratigraphy of lowland and transitional bogs is dominated by sedge and woody-grass peat species.

In the middle part of the watersheds, low-lying slope deposits occur in very flat depressions. They are moistened by groundwater such as perched water from higher areas of watersheds. At the base of the peat bogs lie deoxidized silty calcareous loams, which enrich the deposit with a significant amount of mineral salts. The nature of the vegetation cover indicates that the hard-water regime currently exists. The peat deposit is represented by sedge-hypnum and hypnum types of structure. The thickness of the deposit is from 1.5 to 4.5 m.

Their areas are small, and they alternate with areas of sedge and swamp type of structure with a deposit depth of 1 to 3.5 m. The edges of lowland deposits of the swamp subtype are represented by lowland forest (pine, birch) and forest swamp, wood-sedge, wood-sphagnum, swamp forest types of structure with deposit thickness from 1 to 2.8 m.

The upland areas in the form of islands lie among the lowland deposits. Their peat layer is represented predominantly by the fuscum type of structure and reaches a thickness of 6 m. The world's largest watershed heterogeneous peat deposit, Vasyuganskoe, with an area of ​​over 5 million hectares, is located in the region. Lowland peatlands generally do not form large areas in the region and, in addition to the slopes of watersheds, occupy mainly elongated areas in river valleys.

On low terraces, heavily swamped, lowland sedge-hypnum bogs predominate; lowland and transitional woody-sphagnum, woody-herbaceous bogs develop in the near-terrace part. Floodplains are swamped mainly in the upper reaches of rivers, where lowland sedge, sedge-willow, tree-sedge and forest swamps are formed. In their vegetation cover under the canopy of birch, Carex caespitosa and C. wiluica form high hummocks; in the inter-tussock depressions there is a large amount of forbs.

Deposits of the transitional type are located either at the contact of upland deposits with swampy forests, or at the contact of upland and lowland areas. In both cases, these are most often heavily watered deposits with a thin peat layer (1.5-2 m) and a vegetation cover of herbaceous plants (Carex lasiocarpa, C. rostrata, Scheuchzeria palustris) and hydrophilic sphagnum mosses (Sph . obtusum, Sph. majus, Sph. fallax, Sph. jensenii), forming a smooth, semi-submerged carpet.

The thickness of the peat layer in floodplain peat bogs does not exceed 1.5-2 m. Their deposits of sedge, Scheuchzeria, wood-sedge or birch peat were in conditions of variable moisture with the participation of river waters, so its ash content is relatively increased.

The Vasyugan region is characterized by intensive peat accumulation. The average thickness of peat deposits is 4-5 m. Their age dates back to the early Holocene. The areas of swamps up to 8 m deep are of ancient Holocene age.

Ket-Chulym peat-bog region characterized by less peat compared to Ket-Tymskaya, which is explained in the geomorphological features of the region. The watershed Ket-Chulym plateau has a significantly greater degree of erosional dissection under the influence of the main water arteries. The rivers here cut deeply into the surface of the watersheds and have well-formed but narrow alluvial terraces. This caused a decrease in groundwater. Therefore, the total peat content in the Ket-Chulym region is reduced to 10%.

The relief of the watershed Ket-Chulym plateau is characterized by small saucer-shaped depressions of suffusion origin. They predetermine here basically

location and type of peat bogs. The most widespread in the peat bogs of suffosion depressions is the transitional swamp deposit with a total thickness of the peat layer from 1 to 4.5 m. Rare deposits are less common in them, mainly fuscum, complex and Scheuchzerian-sphagnum with a depth of up to 3-6 m. Flat suffosion depressions 1-2 m deep are occupied by cotton grass-sphagnum or magellanicum deposits. Lowland deposits in suffosion depressions are rare and are represented by forest, tree-sedge, multi-layer forest-fen and sedge types of structure. They fill the deepest basins, in which the thickness of the peat suite reaches 4-5 m.

In the Ket-Chulym region, a certain pattern is noted in the distribution of near-terrace peat deposits. In the middle part of the river. Ulu-Yul peatlands have small sizes and are located on sharply defined terraces. Downstream of the river, the terrace ledges are smoothed out, the surfaces of the terraces expand, and the area of ​​peat deposits increases. The latter acquire an elongated shape and are stretched parallel to the river. Near the mouth of the river. The Ulu-Yul terraces are even less pronounced and peat deposits merge with each other, covering the surface of several terraces.

On terraces and in the near-terrace parts of river valleys, peat bogs are smaller in area (in comparison with the peat bogs of the Ket-Tym region) and, without merging into large-scale massifs, on the terraces they form chains of isolated deep-lying peat deposits extended parallel to the river, often of lowland type with forest, wood-sedge or sedge deposit.

Tura-Ishim peat-bog region It is a lacustrine-alluvial plain composed of sandy-loamy deposits and is characterized by the predominance of denudation processes. The area is heavily swamped. Lowland swamps dominate: sedge, sedge-hypnum, birch-sedge. Raised pine-sphagnum bogs occupy small areas. The most waterlogged central parts of the interfluve are occupied by raised ridge-hollow bogs.

In general, this is an area of ​​high swampiness of weakly dissected gently flat wide river valleys with large lowland sedge-hypnum bogs at the bottoms of terraces and along their slopes and with medium-sized raised and transitional peat bogs on watersheds. The total swampiness of the region is up to 40%.

An example of a peat deposit of the first terraces above the floodplain is “Tarmanskoye”, located in the valley of the river. Tours. It stretches along the river for up to 80 km and adjoins the ledge of the main bank. Its deposit is almost entirely composed of sedge-hypnum and sedge peats, confirming the existence of ground nutrition.

The deposit includes within its boundaries a significant number of primary lakes of a rounded-elongated shape with an emerging orientation along the terrace. At the base of the lakes there are highly mineralized sapropels, which indicates forest-steppe conditions during the formation of the lakes. In the lower horizons of the deposit or on the edges of the deposit, high ash content of peats is observed as a result of clogging of the deposit with colluvial drifts.

North Baraba peat-bog region watershed sedge-hypnum bogs in the north borders on the Vasyugan peat-bog region, in the south on the South Barabinskaya region and is a gently undulating, weakly dissected plain. The region is composed of loess-like loams. There is little peat. It is dominated by small low-lying peatlands, such as borrowed areas, with an area of ​​10 to 100 hectares. The eastern margin, confined to the positive contours of the structures, is characterized by the development of relatively well-drained swamps. More than half of the peat area is lowland peat (54%) and approximately 27% is upland; The percentage of transitional peatlands here is relatively large (19%).

In the central part of the region there are many lakes, depressions and peat deposits. In the western part of the region, on the slopes of the Tara-Tartas interfluve, the main area of ​​sedge-hypnum bogs is concentrated. Hypnosis swamps develop in low-lying elements of the relief, mainly in places where hard-water groundwater flows emerge, along the slopes of watersheds or in the near-terrace parts of river valleys. Therefore, a slightly increased ash content (up to 8-12%) is characteristic of hypnotic peats and peat deposits. The ash content of some near-terrace hypnotic peat bogs averages 6-7%. The same percentages are used to measure the ash content of the sedge-hypnum peat bogs of the Tara-Tartas interfluve.

Towards the east, sedge-hypnum peat bogs give way to their leading position in the lowland type to forest-bog and forest deposits. The latter are located here along the edges of peat deposits, in the central areas of which, as well as in areas with a more elevated bottom topography, there are islands of upland deposits. Moreover, the fuscum fallow is usually peripheral in relation to the complex upland one, which is located in the center, carrying a ridge-lake complex of vegetation on the surface.

Despite the increased carbonate content of the underlying rocks, the relatively low occurrence of groundwater, recharge from atmospheric precipitation, as well as partial uplift of the territory create favorable conditions for the gradual transition of lowland swamps to the oligotrophic stage of development. In the river valleys directly adjacent to the river ridges, the richest in floristic composition are the woody and herbaceous swamps (sogr). In that part of the valley where anoxic groundwater flows and colluvial water does not penetrate, sedge-hypnum bogs are formed. In addition to typical mosses, there are sedge and sedge-grass bogs, and in the east there are reed bogs, characteristic of the grass bog zone.

In the riverine parts of watersheds, along the banks of the upper reaches of rivers, and in the depressions of terraces, transitional forest swamps are widespread. Watershed lowland sedge-hypnum and hypnum bogs usually have a simple structure and are composed of sedge-hypnum and sedge peat species. The presence of ryams (upland sphagnum islands) is a characteristic feature of the sedge-hypnum bogs of the North Barabinsk region. Hypnosis deposits are more typical for swamps on low terraces, where soluble calcium salts predominate in the water-mineral nutrition. In terms of high levels of decomposition and ash content, the deposit of bogs on watershed plains differs from the deposit of peat bogs on low terraces, which have a more complex stratigraphy. Here you can find grass-hypnum, cotton grass-sedge, reed-sedge, reed-sedge, sedge-sphagnum types of peat.

The bottom layers of the deposit are usually composed of reed or sedge-reed types of structure. Peat species of the woody group play a significant role in the structure of deposits of lowland near-terrace and floodplain-near-terrace bogs. Transitional forest swamps are widespread. They form in the interfluves, in the terraces above the floodplain and in the near-terrace parts. The deposits of these swamps are represented by transitional forest and forest-swamp types of structure.

In the ryams, the upper horizons of the deposit (up to 2-4 m) are represented by fuscum peat with separate layers of Magellanicum, Angustifolium, cotton grass-sphagnum, pine-cotton grass and pine-shrub types of peat. The bottom layers of the deposit are usually represented by peat of transitional and lowland types. The average depth of peat deposits on watersheds is 2-3 m; on low terraces the peat thickness increases to 5 m compared to the Vasyugan region. The beginning of the peat formation process dates back to the early Holocene.

Tobol-Ishim peat-bog region located west of the river. Irtysh and crosses the interfluve of Ishim and Tobol in the middle reaches. The surface of the territory is quite dissected and well drained. The swampiness of the region does not exceed 3%. It is dominated by small lowland swamps such as borrows with an area of ​​10 to 100 hectares. The location of the positive contours of the structures determines the development of predominantly well-drained peat deposits here.

The ridged nature of the relief, a poorly developed hydrographic network, a waterproof horizon located close to the surface, and slow runoff of surface waters led to the formation in the interridge spaces of a huge number of lakes, usually round or oval with shallow depths, a flat bottom and strong overgrowth. Lakes are often adjacent to or surrounded by small, shallow-lying sedge-reed bogs. During the period of snowmelt, the fields are filled with meltwater, turning into temporary shallow reservoirs, often interconnected, and then the flow through such a chain of lakes connected by the fields has the character of a river. There are very few isolated lakes. By chemical composition The waters of the lake, sometimes located in close proximity to one another, are distinguished by significant diversity. Salty, bitter and fresh lakes lie almost nearby.

Relatively larger fields, characteristic of the northern part of the region, surround lakes with fresh and brackish water. The thickness of the deposits of these fields is up to 1-1.5 m. It is composed of highly mineralized sedge, sedge-reed and reed peats with an average ash content of 20-30%. Their vegetation cover is dominated by reed, reed-sedge and sedge (C. caespitosa, C. omskiana) phytocenoses.

Smaller areas of borrowings are common in the southern part of the region around salt lakes. They are very shallow, composed of reed peat with a high degree of decomposition and high ash content. The reed association, and less often the sedge association, predominate in their vegetation cover.

In the sandy spaces of the Tobol region and in the northern part of the region on the right bank of Ishim, lowland peat bogs (sedge and sedge-hypnum) have separate areas (such as ryams) with high-lying deposits composed of fuscum peat of a low degree of decomposition, with a convex surface and secondary vegetation cover of pine trees. shrub phytocenosis that developed as a result of repeated fires.

In small basins of suffoses of ionic origin, shallow “split” peatlands of lowland type are found. They developed in solonetz microrelief depressions - “saucers”. Salinization and the subsequent process of swamping lead to the appearance of areas of swampy meadows with Carex intermedia, which are exclusively characteristic of this territory, which are subsequently covered with thickets of shrubs, mainly Salix sibirica, and a birch stand.

There are also treeless “spike” swamps with sedge hummocks on the surface, surrounded on the periphery by tall-trunked birch. They formed in deeper and more moist depressions with diverse wetland vegetation, greatly varying in composition in some cases: with hummocks of Carex omskiana, sometimes with Salix sibirica in the shrub layer. Such peat bogs are never covered over the entire area with birch; the deposits in them are tree-sedge.

South Baraba peat-bog region large borrow-ryam peatlands are composed of alluvial-lacustrine and loess-like deposits. Its soil cover is dominated by peat-bog soils, solonetzes and solonchaks (up to 60%); A smaller area is occupied by chernozems, podzolic soils, etc.

Soil salinization processes (including peat soils) are widespread in the region. Their mineralization naturally increases from north to south. The general calm relief of the region is complicated by low ridges elongated in the southwestern direction in combination with interridge depressions. The hydrographic network is quite dense. Both lakes and river beds are abundantly overgrown with aquatic and wetland vegetation and imperceptibly merge with wetlands. Very often the depressions between the ridges are completely swamped. Characteristic of the Baraba topography are suffusion depressions on various surface elements and a large number of lakes, different in size, origin and chemical composition of water.

The area's swampiness is approximately 33%. Lowland reed-sedge peatlands predominate here, constituting up to 85% of the total wetland area. The remaining 15% is distributed between the upper ryam deposits and the transition deposits of their peripheral areas.

Zaimishchno-ryam peatlands are most widespread in the eastern half of the region, their areas here reach several thousand hectares, and the area of ​​ryams - high, rising up to 8-10 m above the level of the ryam - up to a thousand hectares. Towards the west, the areas of borrowings decrease, ryams are less common, and their height decreases.

The emergence of high-lying ryam deposits among lowland deposits is associated with the feeding of ryam areas with fresh and slightly saline lake or surface stagnant waters. The lakes are still preserved as open reservoirs adjacent to the ryams; sometimes traces of them remain at the base of the ryam deposit in the form of a thin layer of sapropel.

The degree of decomposition of borrowed peats, as a rule, exceeds the species indicator (30-50%), the average ash content is 20%. The deposit of borrowings is composed of highly mineralized peats of the swamp group: reed, reed-sedge and grass (with a predominance of remains of light grass and reed grass in the fiber). The total thickness of the borrowing deposits reaches 1.5 m. In the vegetation cover, in the direction from the center to the periphery, reed, sedge-reed and sedge (or grass-sedge) phytocenoses are successively replaced. The latter borders on saline meadow vegetation. Areas fed by lake waters did not experience variability in moisture and salt conditions. Protected from the influence of saline groundwater by the surrounding low-lying deposits, they were overgrown with alloys of Sph. teres, the reservoirs passed into the peat bog stage; gradually, as the deposits grew, they came out of the influence of lake waters and continued to develop as atmospherically fed peat bogs. Dominance in these areas of Sph. fuscum maintains a regime of high humidity and low temperature in the deposit. Sph. fuscum created its own substrate and microclimate even in forest-steppe conditions and over thousands of years deposited powerful deposits of high-moor peat.

The modern vegetation cover of the ryams is secondary and arose under human influence. The degree of decomposition of the fuscum deposit is always reduced, which is facilitated, in addition to increased humidity and low temperature, apparently by its increased acidity, which inhibits microbiological processes. At the contact of the ryams and the dams themselves, there is usually a belt of transitional deposits with mesotrophic plant cover.

In addition to large ryam peat bogs, the South Barabinsk region is characterized by numerous small peat bogs in saucer-shaped depressions and depressions of suffusion origin along the interfluves and ridges.

Transitional and lowland forest swamps usually form a narrow belt around ryams or are confined to depressions of the mesorelief. In the latter case, forest swamps are genetically related to birch trees. Spike swamps dominated by Carex intermedia are typical of the southern part of the region. Birch-reed swamps here are confined to flat, highly mineralized lowlands and represent one of the initial phases of swamping. The total area of ​​the ryams is insignificant. They are found mainly in the northern half of the region.

According to the radiocarbon method, the absolute age of the ryam with a thickness of 3.1 m dates back to the Middle Holocene, and the borrows with a depth of 1.35 m - to the Late Holocene. The processes of swamping are facilitated by the gradual tectonic uplift of the area, which causes the disintegration of rivers and lakes into separate bodies of water.

East of the river The Yenisei within the Asian part of the Union is divided into seven large natural geographical areas.

Geological structure of Western Siberia

The base of the West Siberian Plain is a young plate of the same name. The plate in the east borders on the Siberian platform, from the south Paleozoic structures of Central Kazakhstan, Altai, and the Salair-Sayan region approach it, and in the west the border goes with the folded system of the Urals. Determining the northern border is difficult because it is covered by the waters of the Kara Sea. The base of the West Siberian plate is the Paleozoic basement, with an average depth of $7$ km. In the mountainous regions of the southeastern part, ancient Precambrian and Paleozoic rocks come to the surface, and within West Siberian their plains are hidden by a thick cover of sedimentary rocks.

The West Siberian plate began its formation in the Mesozoic era, in the Upper Jurassic period. At this time, the area between the Urals and the Siberian Platform subsided, resulting in a huge sedimentation basin. Marine transgressions more than once captured the West Siberian plate during its development. In the Lower Oligocene, the plate was freed from the sea and turned into a huge lacustrine-alluvial plain. A new uplift of the northern part of the plate occurs in the late Oligocene and Neogene, and in the Quaternary period of the Cenozoic era the plate descends again. The development of the plate occurs in such a way that it resembles the process of oceanization and the development of swamps.

The slab foundation is divided into two parts:

1. External side belt. It is represented by slopes of a folded mountain frame, descending towards the central part of the depression. The foundation is located at a depth of $2.5$ km. In the southwest of the Kustanai saddle it approaches the surface at only $300$-$400$ m.
2. Inner area. It is divided into two stages: the southern stage – the Middle Ob meganteclise with a basement depth of up to $4$ km and the northern stage – the Yamalo-Taz megasyneclise descended to a depth of up to $12$ km.

Between the sedimentary cover and the foundation of the plate lies a transitional complex, the age of which is Triassic-Lower Jurassic. The foundation underwent extension and, as a result, the formation of an intracontinental rift zone with a system of graben-like depressions occurred. The depressions were the site of accumulation of sedimentary-volcanogenic and sedimentary coal-bearing continental strata up to $5$ km thick. The transitional complex also contains igneous rocks, represented by basaltic lavas and tuffs.

The development of the intracontinental rift zone within Western Siberia did not lead to the formation of a new ocean. Almost continuous formation of the cover under conditions of plate subsidence took place in the Mesozoic and Cenozoic eras. It is composed of sandy-siltstone coastal-continental deposits and marine clayey and sandy-clayey strata. Their thickness reaches $4$ km in the southern part and $7$-$8$ km in the northern part. Numerous local structures are expressed in the sedimentary cover. These are mainly oil and gas reservoirs.

The general orographic features of Western Siberia were already formed by the end of the Neogene. The sea had a level lower than the modern one by $200$-$250$ m, and a significant part of the bottom of the Kara Sea was dry land. At the end of the Neogene, a general cooling of the climate and the development of Quaternary glaciation began.

Relief of Western Siberia

The development of the modern relief of Western Siberia was greatly influenced by the geological development of the territory, tectonic structure and exogenous relief-forming processes. The unevenness of the foundation was leveled out as a result of the accumulation of a thick layer of loose sediments. The periphery of the plain has a small amplitude of uplifts, reaching $100$-$150$ m. The central and northern parts of the plain are characterized by subsidence of $100$-$150$ m. However, a number of lowlands and hills can be distinguished. The plain is open to the north, towards the Kara Sea and has the shape of a stepped amphitheater.

There are three altitude levels on the territory of the West Siberian Plain:

1. Level one has a height of less than $100$ m and occupies half of the territory;
2. The second level is at an altitude of $100$-$150$ m;
3. The third level is located in the range of $150$-$200$ m with small areas from $250$-$300$ m.

The edges of the plain have a higher level and are represented by the North Sosvinskaya, Verkhnetazovskaya, Lower Yisei uplands, the Priobsky plateau, the Turinskaya, Ishimskaya, Kulundinskaya, Ketsko-Tymskaya plains. The northern and central parts of the plain are represented by areas below $100$ m. These are the lowest areas of the plain. The Nizhneobskaya, Nadymskaya, Purskaya, Tazovskaya, Kondinskaya lowlands have a height of less than $50$ m. In the inner parts of the plain there is a strip of clearly defined hills - Verkhnetazovskaya, Numto ridge, Belogorsk continent, Lyulimvor.

From an orographic point of view, the elevation of the plain along the edges and the descent of the surface of the plate towards the center are clearly visible. The interior regions of the plain, where thick Mesozoic deposits occur, are already losing the clarity of expression in the relief of large basement structures. The number of inversion structures is growing. The Vasyugan Plain, for example, is nothing more than an anteclise located within a syneclise. Within the inner zone, under the conditions of recent subsidence, the formation of accumulative and stratified-accumulative plains took place. They are composed of Neogene-Quaternary loose sediments.

The types of morphosculptures created by exogenous relief-forming processes are located on the plain in the direction from north to south. Off the coast of the Kara Sea there are sea plains. They were formed in post-glacial times after the retreat of the sea. Moraine and fluvio-glacial plains are located to the south. Here they are adjacent to glacial, lacustrine-alluvial plains.

Minerals of Western Siberia

The main wealth of the West Siberian Plain are hydrocarbons - oil and gas. Experts estimate the area of ​​promising oil and gas fields at $1.7 million sq km. Such large deposits as Samotlorskoye and Megionskoye, located in the Nizhnevartovsk region, are associated with the middle Ob region. Large deposits in the Surgut region - Ust-Balykskoye, Fedorovskoye, etc.

Natural gas in the Subpolar region - the Medvezhye, Urengoy fields, in the Arctic - Yamburgskoye, Ivankovskoye, etc. There is oil and gas in the Urals, and new promising fields have been discovered on the Yamal Peninsula. In general, more than $300 oil and gas deposits have been discovered on the plain.

In addition to hydrocarbons, large deposits are known in Western Siberia coal, the main reserves of which are located within Kuzbass. Kuznetsk coal reserves are estimated at $600 billion tons. Almost $30$% of these coals are coking. Greater thickness of coal seams and close location to the surface allow their development not only by mines, but also open method. Brown Kansk-Achinsk coals lie to the northeast of the Kuznetsk basin. In the largest Itat field, the thickness of the layers reaches $80$ meters, and the depth ranges from $10$ to $220$ meters. The cheapest coal in Russia is mined here. Anthracite coals are concentrated in the Gorlovka basin, located in the south of the Novosibirsk region. Brown coals of the Tyumen region have not yet been put into operation.

Of the fuel resources in the depths of the West Siberian Plain there is $50$% of all-Russian reserves peat.

Stands out for its reserves and ore base. Significant iron ore resources are concentrated in the Narym, Kolpashevo, and Yuzhno-Kolpashevo deposits. Brown iron ores occur here. Gornaya Shoria is characterized by magnesium ore deposits - Tashtagol and Sheregesh. In Altai there are the Inskoye and Beloretskoye fields. There are deposits of manganese ores and nephelines in the Kemerovo region. Place of Birth mercury in Altai.

The lakes of the Kulunda steppe contain reserves soda and salts.

Limestones in the Novosibirsk and Kemerovo regions.

Altai has significant reserves building materials .

In addition to minerals, Western Siberia is rich forest resources. Timber reserves account for $11$% of Russian reserves.

Note 1

Issues of protection and rational use of natural resources are also relevant for Western Siberia. Careless use of resources can ruin surrounding nature and lead to negative consequences.

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

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

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

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

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

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

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

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

Geological structure and history of development of the territory

Tazovsky Peninsula and Middle Ob in the section Nature of the World.

Many features of the nature of Western Siberia are determined by the nature of its geological structure and history of development. The entire territory of the country is located within the West Siberian epi-Hercynian plate, the foundation of which is composed of dislocated and metamorphosed Paleozoic sediments, similar in nature to similar rocks of the Urals, and in the south of the Kazakh hillocks. 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. However, even large ones structural elements appear in the modern relief less clearly than the tectonic structures of the Russian Platform. This is explained by the fact that the surface relief of Paleozoic rocks, descended to great depths, is leveled here by a cover of Meso-Cenozoic sediments, the thickness of which exceeds 1000 m, and in individual depressions and syneclises of the Paleozoic basement - 3000-6000 m.

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

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

Significant changes in the conditions for the accumulation of sediments occurred in the Neogene. Formations of rocks of Neogene age, outcropping mainly in the southern half of the plain, consist exclusively of continental lacustrine-fluvial deposits. They were formed in the conditions of a poorly dissected plain, first covered with rich subtropical vegetation, and later with broad-leaved deciduous forests of representatives of the Turgai flora (beech, walnut, hornbeam, lapina, etc.). In some places there were areas of savannah where giraffes, mastodons, hipparions, and camels lived at that time.

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

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

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

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

The last, Zyryansky, glaciation was preceded by regression of the boreal sea, caused by uplifts of the northern regions of the West Siberian Plain, the Urals and the Central Siberian Plateau; the amplitude of these uplifts was only a few tens of meters. At the maximum stage of development of the Zyryan glaciation, glaciers descended to the areas of the Yenisei Plain and the eastern foot of the Urals to approximately 66° N. sh., where a number of stadial terminal moraines were left. In the south of Western Siberia at this time, sandy-clayey Quaternary sediments were overwintering, aeolian landforms were forming, and loess-like loams were accumulating.

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. Thus, according to geologist V.N. Saksa and geomorphologist G.I. Lazukov, glaciation began here in the Lower Quaternary and consisted of four independent eras: Yarskaya, Samarovskaya, Tazovskaya and Zyryanskaya. Geologists S. A. Yakovlev and V. A. Zubakov even count six glaciations, attributing the beginning of the most ancient of them to the Pliocene.

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

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

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

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

Relief

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

Scheme of the main orographic elements of the West Siberian Plain

The differentiated subsidence of the West Siberian Plate in the Mesozoic and Cenozoic led to the predominance within its boundaries of processes of accumulation of loose sediments, the thick cover of which levels out the surface irregularities of the Hercynian basement. Therefore, the modern West Siberian Plain has a generally flat surface. However, it cannot be considered as a monotonous lowland, as was recently believed. In general, the territory of Western Siberia has a concave shape. Its lowest areas (50-100 m) are located mainly in the central ( Kondinskaya and Sredneobskaya lowlands) and northern ( Nizhneobskaya, Nadym and Pur lowlands) parts of the country. Along the western, southern and eastern outskirts there are low (up to 200-250 m) elevations: Severo-Sosvinskaya, Turinskaya, Ishimskaya, Priobskoye and Chulym-Yenisei plateaus, Ketsko-Tymskaya, Verkhnetazovskaya, Nizhneneiseyskaya. A clearly defined strip of hills forms in the inner part of the plain Sibirskie Uvaly(average height - 140-150 m), stretching from the west from the Ob to the east to the Yenisei, and parallel to them Vasyuganskaya plain.

Some orographic elements of the West Siberian Plain correspond to geological structures: for example, the Verkhnetazovskaya and Lyulimvor, A Barabinskaya and Kondinskaya the lowlands are confined to the syneclises of the slab foundation. 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 West Siberian Plain is usually divided into four large geomorphological regions: 1) marine accumulative plains in the north; 2) glacial and water-glacial plains; 3) periglacial, mainly lacustrine-alluvial plains; 4) southern non-glacial plains (Voskresensky, 1962).

The differences in the relief of these areas are explained by the history of their formation in Quaternary times, the nature and intensity of recent tectonic movements, and zonal differences in modern exogenous processes. In the tundra zone, relief forms are especially widely represented, the formation of which is associated with the harsh climate and widespread permafrost. Thermokarst basins, bulgunnyakhs, spotted and polygonal tundras are very common, and solifluction processes are developed. Typical of the southern steppe provinces are numerous closed basins of suffusion origin, occupied by salt marshes and lakes; The network of river valleys here is sparse, and erosional landforms in the interfluves are rare.

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

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

Climate

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

Western Siberia is a country with a fairly harsh continental climate. Its large extent from north to south causes a clearly expressed climate zonation and significant differences climatic conditions northern and southern parts of Western Siberia, associated with changes in the amount of solar radiation and the nature of the circulation of air masses, especially westerly transport flows. The southern provinces of the country, located inland, at a great distance from the oceans, are also characterized by a more continental climate.

During the cold period, two baric systems interact within the country: an area of ​​relatively high atmospheric pressure located over the southern part of the plain, and an area of ​​low pressure, which in the first half of winter stretches 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. They recur especially often in the first half of winter. Therefore, the weather in the coastal provinces is very unstable; on the coast of Yamal and the Gydan Peninsula they vouch strong winds, 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; there are few thaws here. Minimum temperatures throughout Western Siberia are almost the same. Even near the southern border of the country, in Barnaul, there are frosts down to -50 -52°, i.e. almost the same as in the far north, although the distance between these points is more than 2000 km. Spring is short, dry and relatively cold; April, even in the forest-swamp zone, is not yet quite a spring month.

In the warm season, low pressure sets over the country, and an area of ​​higher pressure forms over the Arctic Ocean. In connection with this summer, weak northern or northeastern winds predominate 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 40° 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. Even in September the weather is warm during the day, but November, even in the south, is already a real winter month with frosts down to -20 -35°.

Most of the precipitation falls in the summer and is brought by air masses coming from the west, from the Atlantic. From May to October, Western Siberia receives up to 70-80% of the annual precipitation. There are especially many of them in July and August, which is explained by 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 in different years. Even in the taiga, where these changes are less than in other zones, precipitation, for example, in Tomsk, falls from 339 mm in a dry year up to 769 mm in wet. Especially large ones are observed in the forest-steppe zone, where, with an average long-term precipitation amount of about 300-350 mm/year in wet years it falls up to 550-600 mm/year, and on dry days - only 170-180 mm/year.

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

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

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

The harsh climate of the northern regions of Western Siberia, where the heat entering the soil is not enough to maintain a positive temperature of the rocks, contributes to 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 power decreases, temperatures rise to?0.5 -1°, and the depth of summer thawing also increases, especially in areas composed of mineral rocks.

Water

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

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

The entire territory of the country is located within the large West Siberian artesian basin, in which hydrogeologists distinguish several second-order basins: Tobolsk, Irtysh, Kulunda-Barnaul, Chulym, Ob, etc. Due to the large thickness of the 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.

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

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

The surface of the West Siberian Plain is drained by many thousands of rivers, total length which exceeds 250 thousand. km. These rivers carry about 1,200 km 3 waters - 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 km 2. Some southern regions of the country with a total area of ​​more than 445 thousand. km 2 belong to territories of closed drainage and are distinguished by the abundance of closed 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 for 3000 km equals only 90 m, and its flow speed does not exceed 0.5 m/sec.

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

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

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

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

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

Along the eastern border of the West Siberian Plain flows Yenisei- the most abundant river in the Soviet Union. Its length is 4091 km(if we consider the Selenga River as the source, then 5940 km); The basin area is almost 2.6 million. km 2. Just like the Ob, the Yenisei basin is elongated in the meridional direction. All its large right tributaries flow through the territory of the Central Siberian Plateau. Only the shorter and shallower left tributaries of the Yenisei begin from the flat, swampy watersheds of the West Siberian Plain.

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

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

On the West Siberian Plain there are about one million lakes, the total area of ​​which is more than 100 thousand hectares. km 2. 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 forest-steppe and steppe regions of Western Siberia there are lakes that fill suffusion or tectonic basins.

Soils, vegetation and fauna

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

The flat terrain of Western Siberia contributes to pronounced 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. Geographical zoning thus resembles in general terms the zoning system of the Russian Plain. However, the zones of the West Siberian Plain also have a number of local specific features that significantly distinguish them from similar zones in Eastern Europe. Typical zonal landscapes are located here in 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. Thus, here, much more than on the Russian Plain, the role in the distribution of soils and plant cover is played by the nature and density of the relief, causing significant differences in the soil moisture regime.

Therefore, there are, as it were, two independent systems of latitudinal zoning in the country: the zoning of drained areas and the zoning of undrained interfluves. These differences are most clearly manifested in the nature of the soils. Thus, in drained areas of the forest-swamp zone, mainly strongly podzolized soils are formed under coniferous taiga and sod-podzolic soils under birch forests, and in neighboring undrained areas - thick podzols, swamp and meadow-swamp soils. The drained spaces of the forest-steppe zone are most often occupied by leached and degraded chernozems or dark gray podzolized soils under birch groves; in undrained areas they are replaced by marshy, saline or meadow-chernozemic soils. In the upland areas of the steppe zone, either ordinary chernozems, characterized by increased fatness, low thickness and tongue-like (heterogeneity) soil horizons, or chestnut soils predominate; in poorly drained areas, spots of malts and solodized solonetzes or solonetzic meadow-steppe soils are common among them.

Fragment of a section of the swampy taiga of Surgut Polesie (according to V. I. Orlov)

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

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

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

The increase in continental climate causes a relatively sharp transition, compared to the Russian 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 Russian Plain, and the main tree species found in it are birch and aspen.

The West Siberian Plain is entirely part of the transitional Euro-Siberian zoogeographical subregion of the Palearctic. There are 478 species of vertebrates known here, including 80 species of mammals. The country's fauna is young and in its composition differs little from the fauna of the Russian Plain. Only in the eastern half of the country are some eastern, Trans-Yenisei forms found: the Djungarian hamster (Phodopus sungorus), chipmunk (Eutamias sibiricus) etc. B last years the fauna of Western Siberia has been enriched by muskrats acclimatized here (Ondatra zibethica), brown hare (Lepus europaeus), American mink (Lutreola vison), teledut squirrel (Sciurus vulgaris exalbidus), and carp were introduced into its reservoirs (Cyprinus carpio) and bream (Abramis brama).

Natural resources

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

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

Pastures in the forest-swamp, forest-steppe and steppe zones are of high economic value, especially water meadows along the Ob, Irtysh, Yenisei and their large tributaries. The abundance of natural meadows here creates a solid base for further development livestock farming and significantly increasing its productivity. Reindeer reindeer pastures of the tundra and forest-tundra, which occupy more than 20 million hectares in Western Siberia, are important for the development of reindeer husbandry. ha; More than half a million domestic reindeer graze on them.

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

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

The waters of large Western Siberian rivers can also be used for irrigation and water supply of semi-desert and desert regions of Kazakhstan and Central Asia, which are already experiencing a significant lack of water resources. Currently, design organizations are developing the basic provisions and feasibility study for transferring part of the flow of Siberian rivers to the Aral Sea basin. According to preliminary studies, the implementation of the first stage of this project should ensure the annual transfer of 25 km 3 waters from Western Siberia to Central Asia. For this purpose, it is planned to create a large reservoir on the Irtysh, near Tobolsk. From it to the south along the Tobol valley and along the Turgai depression into the Syr Darya basin, the Ob-Caspian canal, more than 1500 long, will go to the reservoirs created there km. It is planned to lift water to the Tobol-Aral watershed by a system of powerful pumping stations.

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

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

Until quite recently, many geologists, based on the idea of ​​the uniformity of the thick strata of loose sediments composing the plain and the seeming simplicity of its tectonic structure, very cautiously assessed the possibility of discovering any valuable minerals in its depths. However, geological and geophysical research carried out in recent decades, accompanied by the drilling of deep wells, showed the fallacy of previous ideas about the country's poverty in mineral resources and made it possible to imagine in a completely new way the prospects for the use of its mineral resources.

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

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

Oil and gas fields of Western Siberia

The discovery of both oil and gas fields is of great importance for the development of the economy of Western Siberia and neighboring economic regions. Tyumen and Tomsk regions are turning into important areas of oil production, oil refining and chemical industry. Already in 1975, more than 145 million were mined here. T oil and tens of billions of cubic meters of gas. To deliver oil to areas of consumption and processing, the Ust-Balyk - Omsk oil pipelines (965 km), Shaim - Tyumen (436 km), Samotlor - Ust-Balyk - Kurgan - Ufa - Almetyevsk, through which oil gained access to the European part of the USSR - to the places of its greatest consumption. For the same purpose, the Tyumen-Surgut railway and gas pipelines were built, through which natural gas from Western Siberian fields goes to the Urals, as well as to the central and northwestern regions of the European part of the Soviet Union. In the last five-year period, the construction of the giant Siberia-Moscow supergas pipeline was completed (its length is more than 3000 km), through which gas from the Medvezhye field is supplied to Moscow. In the future, gas from Western Siberia will go through pipelines to Western European countries.

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

Geological research led to the discovery of the deposit and other minerals. In the southeast, in the Upper Cretaceous and Paleogene sandstones of the vicinity of Kolpashev and Bakchar, large deposits of oolitic iron ores were discovered. They lie relatively shallow (150-400 m), the iron content in them is up to 36-45%, and the predicted geological reserves of the West Siberian iron ore basin are estimated at 300-350 billion. T, including in the Bakcharskoye field alone - 40 billion. T. Hundreds of millions of tons of table salt and Glauber's salt, as well as tens of millions of tons of soda, are concentrated in numerous salt lakes in the south of Western Siberia. In addition, Western Siberia has enormous reserves of raw materials for the production of building materials (sand, clay, marls); Along its western and southern outskirts there are deposits of limestone, granite, and diabase.

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

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

The main directions of development of the national economy plan to continue the formation of the West Siberian territorial-production complex, to transform Western Siberia into the main base of the USSR for oil and gas production. In 1980, 300-310 million will be mined here. T oil and up to 125-155 billion. m 3 natural gas (about 30% of gas production in our country).

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

West Siberian Plain

The West Siberian Lowland is one of the largest lowland accumulative plains on the globe. It is located to the north of the hilly plain of Kazakhstan and the Altai mountains, between the Urals in the west and the Central Siberian Plateau in the east. Extent from north to south up to 2500 km, from W. to E. from 1000 to 1900 km; area about 2.6 million. km 2. The surface is flat, slightly dissected, with small amplitudes of heights. The heights of the lowlands of the northern and central regions do not exceed 50-150 m, low elevations (up to 220-300 m) are characteristic mainly of the western, southern and eastern outskirts of the plain. The strip of hills also forms the so-called. Siberian Uvaly, extending in the middle part of the West-North. R. from the Ob almost to the Yenisei. Everywhere, wide, flat spaces of interfluves with slight surface slopes predominate, heavily swamped and in places complicated by moraine hills and ridges (in the north) or low sandy ridges (mainly in the south). Significant areas are occupied by flat ancient lake basins - woodlands. River valleys form a relatively sparse network and in the upper reaches most often appear as shallow hollows with poorly defined slopes. Only a few of the largest rivers flow in well-developed, deep (up to 50-80 m) valleys, with a steep right bank and a system of terraces on the left bank.

Z.-S. R. formed within the epi-Hercynian West Siberian plate, the foundation of which is composed of intensely dislocated Paleozoic sediments. They are covered everywhere with a cover of loose marine and continental Meso-Cenozoic rocks (clays, sandstones, marls, etc.) with a total thickness of over 1000 m(in foundation depressions up to 3000-4000 m). The youngest anthropogenic deposits in the south are alluvial and lacustrine, often covered with loess and loess-like loams; in the north - glacial, marine and glacial-marine (thickness in places up to 200 m). In a cover of loose sediments Z.-S. R. contains horizons of groundwater - fresh and mineralized (including brines); there are also hot (up to 100-150 ° C) waters (see West Siberian artesian basin). In the depths of Z.-S. R. contains the richest industrial deposits of oil and natural gas (see West Siberian oil and gas basin).

The climate is continental and quite harsh. In winter, cold continental air masses of temperate latitudes predominate over the plain, and in the warm season, an area of ​​low pressure is formed and moist air masses from the North Atlantic often enter here. Average annual temperatures range from -10.5°C in the north to 1-2°C in the south, average temperatures in January range from -28 to -16°C, and in July from 4 to 22°C. The duration of the growing season in the extreme south reaches 175-180 days. The bulk of precipitation is brought by air masses from the west, mainly in July and August. Annual precipitation is from 200-250 mm in the tundra and steppe zones up to 500-600 mm in the forest area. Snow depth from 20-30 cm in the steppe up to 70-100 cm in the taiga of the Yenisei regions.

The plain territory drains more than 2000 rivers, the total length of which exceeds 250 thousand km. km. The largest of them are the Ob, Yenisei, and Irtysh. The main sources of river nutrition are melted snow waters and summer-autumn rains; up to 70-80% of the annual runoff occurs in spring and summer. There are many lakes, the largest are Chany, Ubinskoye, etc. Some of the lakes in the southern regions are filled with salty and bitter-salty water. Large rivers are important navigable and rafting routes connecting the southern regions with the northern ones; The Yenisei, Ob, Irtysh, Tom also have large reserves of hydropower resources.

Flat relief of the W.-N. river. causes a clearly pronounced latitudinal geographical zoning. A specific feature of most zones of Western Siberia is excessive ground moisture and, as a consequence, the widespread occurrence of swamp landscapes, which in the south are replaced by solonetzes and solonchaks. The north of the plain is a tundra zone, in which landscapes of arctic, moss, and lichen tundra are formed on tundra arctic and tundra gley soils, and in the south - shrub tundra. To the south there is a narrow strip of forest-tundra, where complex landscape complexes of shrub tundra, spruce-larch woodlands, sphagnum and lowland bogs are developed on peaty-gley, gley-podzolic and bog soils. Most of W.-S. R. refers to the forest (forest-swamp) zone, within which podzolic soils the predominant coniferous taiga consists of spruce, fir, cedar, pine, and Siberian larch; Only in the extreme southern zone are taiga massifs replaced by a strip of small-leaved forests of birch and aspen. The total forest area exceeds 60 million hectares. ha, timber reserves 9 billion m 3, and its annual growth is 100 million. m 3. The forest zone is distinguished by the widespread development of raised ridge-hollow sphagnum bogs, which in some places account for more than 50% of the area. Typical animals of the forest zone are: brown bear, lynx, wolverine, marten, otter, weasel, sable, elk, Siberian roe deer, squirrel, chipmunk, muskrat and other representatives of the fauna of the European-Siberian subregion of the Palearctic.

To the south of the subzone of small-leaved forests there is a forest-steppe zone, where leached and ordinary chernozems, meadow-chernozems, dark gray forest and swamp soils, solonetzes, and malt soils are formed under the not yet plowed herb meadows, birch-aspen copses (“spikes”) and grassy bogs. . The extreme southern part of the W.-N. r. It occupies a steppe zone, in the north of which, until recently, grass-feather grasses of various types predominated, and in the south, feather-grass-fescue steppes predominated. Now these steppes with their fertile chernozem and dark chestnut soils have been plowed and only areas with saline soils have retained their virgin character.

Lit.: West Siberian Lowland. Essay on Nature, M., 1963; Western Siberia, M., 1963.

N. I. Mikhashov.

Great Soviet Encyclopedia. - M.: Soviet Encyclopedia. 1969-1978 .

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

West Siberian Plain ... Wikipedia

Between the Urals in the west and the Central Siberian Plateau in the east. OK. 3 million km². The length from north to south is up to 2500 km, from west to east up to 1900 km. Height ranges from 50 to 150 m in the northern and central parts to 300 m in the western, southern and... ... Big Encyclopedic Dictionary

WEST SIBERIAN PLAIN, between the Urals in the west and the Central Siberian Plateau in the east. OK. 3 million km2. The length from north to south is up to 2500 km, from west to east up to 1900 km. Height from 50 to 150 m in the northern and central parts to 300 m in... ... Russian history

One of the largest on Earth. Occupies b. Part Zap. Siberia, stretching from the coast of the Kara Sea in the north to the Kazakh small hills in the south, from the Urals in the west to the Central Siberian Plateau in the east. OK. 3 million km². Wide flat or… Geographical encyclopedia

Between the Urals in the west and the Central Siberian Plateau in the east About 3 million km2. The length from north to south is up to 2500 km, from west to east up to 1900 km. Height from 50 to 150 m in the northern and central parts to 300 m in the western, southern and eastern parts.… … encyclopedic Dictionary

West Siberian Plain- West Siberian Plain, West Siberian Lowland. One of the largest low-lying accumulative plains in the world. It occupies most of Western Siberia, stretching from the coast of the Kara Sea in the north to the Kazakh small hills and ... Dictionary "Geography of Russia"

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

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

Relief

The surface is a low accumulative plain with a fairly uniform topography (more uniform than the relief of the East European Plain), the main elements of which are wide flat interfluves and river valleys; characteristic various shapes manifestations of permafrost (extended up to 59 ° N latitude), increased swampiness and developed (mainly in the south in loose rocks and soils) ancient and modern salt accumulation. In the north, in the area of ​​distribution of marine accumulative and moraine plains (Nadym and Pur lowlands), the general flatness of the territory is broken by moraine gently ridged and hilly-ridged (North-Sosvinskaya, Lyulimvor, Verkhne-, Srednetazovskaya, etc.) hills with a height of 200–300 m, whose southern border runs around 61–62°N. sh.; they are covered in a horseshoe shape from the south by flat-topped hills, including the Poluyskaya Upland, the Belogorsk Continent, the Tobolsk Continent, the Sibirskie Uvaly (245 m), etc. In the north, exogenous permafrost processes (thermoerosion, soil heaving, solifluction) are widespread, deflation is common on sandy surfaces, in swamps there is peat accumulation. On the Yamal, Tazovsky and Gydansky peninsulas, permafrost is widespread; The thickness of the frozen layer is very significant (up to 300–600 m).

To the south, the region of moraine relief is adjacent to flat lacustrine and lacustrine-alluvial lowlands, the lowest (40–80 m high) and the most swampy of which are the Kondinskaya lowland and the Middle Ob lowland with the Surgut lowland (height 105 m). This territory, not covered by Quaternary glaciation (south of the Ivdel-Ishim-Novosibirsk-Tomsk-Krasnoyarsk line), is a weakly dissected denudation plain, rising to 250 m to the west, to the foot of the Urals. In the area between the Tobol and Irtysh rivers there is a sloping, in some places with ragged ridges, lacustrine-alluvial Ishim Plain(120–220 m) with a thin cover of loess-like loams and loess overlying salt-bearing clays. Adjacent to it are alluvial Baraba Lowland, Vasyugan Plain and Kulunda Plain, where the processes of deflation and modern salt accumulation are developed. In the foothills of Altai there are the Priob Plateau and the Chulym Plain.

For geological structure and mineral resources, see Art. West Siberian Platform ,

Climate

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

Surface water

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

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

Types of landscapes

The uniformity of the relief of the vast West Siberian Plain determines a clearly defined latitudinal zonation of landscapes, although in comparison with the East European Plain natural areas here they are shifted to the north; landscape differences within the zones are less noticeable than on the East European Plain, and there is no zone of broad-leaved forests. Due to the poor drainage of the territory, hydromorphic complexes play a prominent role: swamps and swampy forests occupy about 128 million hectares here, and in the steppe and forest-steppe zones there are many solonetzes, solods and solonchaks.

On the Yamal, Tazovsky and Gydansky peninsulas, under conditions of continuous permafrost, landscapes of arctic and subarctic tundra with moss, lichen and shrub (dwarf birch, willow, alder) vegetation on gley soils, peat gley soils, peat podburs and turf soils were formed. Polygonal grass-hypnum bogs are widespread. The share of indigenous landscapes is extremely small. To the south, tundra landscapes and swamps (mostly flat-hilly) are combined with larch and spruce-larch woodlands on podzolic-gley and peat-podzolic-gley soils, forming a narrow zone of forest-tundra, transitional to the forest (forest-swamp) zone of the temperate zone, represented by the subzones northern, middle and southern taiga. What is common to all subzones is swampiness: over 50% of the northern taiga, about 70% - middle, about 50% - southern. The northern taiga is characterized by flat- and large-hilly raised bogs, the middle one - ridge-hollow and ridge-lake bogs, the southern one - hollow-ridge, pine-shrub-sphagnum, transitional sedge-sphagnum and lowland tree-sedge. The largest swamp massif - Vasyugan Plain. Forest complexes of different subzones are unique, formed on slopes with varying degrees of drainage.

Northern taiga forests on permafrost are represented by sparse, low-growing, heavily swampy, pine, pine-spruce and spruce-fir forests on gley-podzolic and podzolic-gley soils. Indigenous landscapes of the northern taiga occupy 11% of the plain's area. Indigenous landscapes in the middle taiga occupy 6% of the area of ​​the West Siberian Plain, in the southern - 4%. What is common to the forest landscapes of the middle and southern taiga is the wide distribution of lichen and dwarf-sphagnum pine forests on sandy and sandy loam ferruginous and illuvial-humus podzols. On loam soils in the middle taiga, along with extensive swamps, there are spruce-cedar forests with larch and birch forests on podzolic, podzolic-gley, peat-podzolic-gley and gley peat-podzols.

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

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

Environmental problems and protected natural areas

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

Numerous reserves, national and natural parks have been created to study and protect typical and rare natural landscapes. Among the largest reserves are: in the tundra - the Gydansky Reserve, in the northern taiga - the Verkhnetazovsky Reserve, in the middle taiga - the Yugansky Reserve and Malaya Sosva, etc. In the sub-taiga, the Pripyshminskie Bory National Park was created. Natural parks have also been organized: in the tundra - Oleniy Ruchi, in the north. taiga - Numto, Siberian Uvaly, in the middle taiga - Kondinsky lakes, in the forest-steppe - Bird Harbor.

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