Where is the West Siberian Plain located? Geographical position of the West Siberian Plain: description and features

The West Siberian Lowland is a single physical-geographical region consisting of two flat bowl-shaped depressions, between which there are elevations elongated in the latitudinal direction (up to 175-200 m), orographically combined into Siberian ridges.

Almost from all sides the lowland is outlined by natural boundaries. In the west it is distinctly 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 passes here into the adjoining uplands of the Turgai plateau and the Kazakh hills.

The West Siberian lowland occupies about 2.25 million km 2 and has a length of 2500 km from north to south, and 1500 km from east to west (in the widest southern part). The exceptionally flat relief of this territory is explained by the alignment of the complex-folded basement of the West Siberian Platform with a thick cover of Meso-Cenozoic deposits. 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 deposits, the thickness of which in the northern and central regions reaches 200-250 m. However, in the south, the thickness of Quaternary deposits drops to 5-10 m and in the modern relief, signs of the influence of neotectonic movements are clearly manifested.

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

Large modern landforms of Western Siberia are morphostructures created by the latest movements of the earth's crust. Positive morphostructures: uplands, plateaus, ridges - have a more dissected relief and better drainage. Dominant for the relief of the territory are negative morphostructures - plains covered with a thickness of loose layered deposits, often gleyed to a great depth. These properties worsen the water permeability of the strata and slow down the ground runoff.

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

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

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 the species characteristic of the taiga forests of Siberia, such as cedar, fir, and larch. Usually, together with birch, spruce, and pine, they make up the forest stand of swamps in various combinations and quantities. Almost pure plantations of birch on peatlands are quite frequent and, under appropriate conditions, are found in all peat-bog regions of the West Siberian Lowland. On the lowland peatlands of the floodplains, pure willow thickets are noted.

In the shrub layer of the vegetation cover of the West Siberian swamps, such a representative of the Siberian flora as Salix sibirica is found, but the European species is not reflected in it. Calluna vulgaris. Representatives of the Siberian flora were also noted in the grass 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, has expanded its habitat in Western Siberia and is found in large numbers on typical high-moor peat bogs. sp. rubellum and Sph. cuspi datum are typical inhabitants of raised peat bogs in the northwestern region of the European part of the Union; they are rarely found in the moss cover of peat bogs in the West Siberian Lowland. But in much greater numbers and in more southern latitudes, Sph. lindbergii and Sph. congstroemii, which are typical for the peatlands of the Arkhangelsk region and are rare in the peatlands of the middle belt. Sometimes Cladonia and Cetraria form continuous patches in the ridge-lake areas of the watershed peatlands of the Vasyugan region, 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 phytocenosis, which covers large areas in the marginal areas of the lands (under 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 in the tree layer by birch (up to 15–20 m high) and conifers: spruce, cedar, pine, larch; in the shrub layer - marsh myrtle, cranberries, blueberries, cloudberries. The herbage is rich in species and flourishes; C. caespitosa dominates in it, C. globularis, C. disperma are found among other sedges, and taiga plants (Equisetum silvaticum, Casalia hastata, Pyrola rolundifolia) grow in forbs along with marsh plants. Elements of the taiga flora are also noted in the moss cover: on hummocks of Sph. warnstorfii - Pleuroziumschreberi and Hylocomium splendens, in interhummock depressions - Thuidium recognitum, Helodium blandowii, on the slopes of hummocks - Climacium dendroides. Iron efflorescences can often be observed in the depressions between the bumps in the sogres.

Most often, the edge areas of low-lying marshy swamps of the floodplain terraces along the channels of the Ob, Irtysh, Chulym, Keti, and Tyma rivers are covered with sorams. 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 on the interfluve of the Ishim and Tobol in their middle reaches. Here they adjoin lakes or surround them with a continuous ring. Huge areas are sometimes occupied by borrowings in lowlands, no longer connected with lakes, but bearing the features of former channels between lakes.

Zaimishchno-ryam peatlands are often found in the eastern part of the South Baraba peat-bog region, where they are confined to lakes or flat depressions in which surface waters stagnate for a long time. Among the loans scattered raised raised peat bogs, occupying a small area compared to the loans. These are well-known "ryams". During the growing season, a variable water-mineral regime is created in the lands: in spring and in the first half of summer they are flooded with fresh deluvial meltwater, and often hollow rivers; in the second half of the growing season, the lands dry up over a larger peripheral area, and here favorable conditions arise for capillary rise to the surface of saline soil and ground waters, and salt efflorescences (Ca, Cl and SO 3) are usually observed on the surface.

The area of ​​the loan can be subdivided into: a zone of constant moistening with relatively fresh waters (the central part of the loan, shores of lakes and river channels) and a zone of variable moistening, where both the degree of watering and the degree of salinity of the feed waters are variable (peripheral parts of the loans).

The central parts of the lands are covered with reed phytocenosis, in which the main background plants are reed, reed (Scolochloa festucacea), reed grass, sedges (C. caespitosa and C. wiluica). As an admixture, the phytocenosis includes Carex omskiana, C. buxbaumii, watch, bedstraw (Galium uliginosum). 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, gradual thinning of reed beds and the introduction of sedges (C. diandra, C. pseudocyperus), cattail and reed grass are observed. The sedge-reed phytocenosis is characterized by scattered scattered birch (B. pubescens) and willow (S. cinerea) bushes.

Along the periphery of the borrowings in the zone of variable moisture, reedweed (Scolochloa, festucacea), which under the conditions of Baraba is an indicator of mixed chloride-sulphate salinization, displaces reed grass from the vegetation cover, and here a grass-sedge phytocenosis arises mainly from reedweed, Carex omskiana, C. appropinquata and C. orthostachys with a small contribution of the same reed.

The formation and development of ryams (oligotrophic pine-shrub-sphagnum islands) occurs in isolation from saline soils in both horizontal and vertical directions. Isolation in the horizontal direction is the deposit of loans; isolation 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 fallow is 0.5-1 m. The stumpiness of the sphagnum deposit is low and decreases from the upper layers to the lower ones.

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

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

The peat deposits of Western Siberia are extremely diverse in terms of the conditions of formation and development, the qualitative and quantitative indicators of the deposit, the vegetation cover, the nature of distribution and other factors, in the change of which there is a fairly clear pattern closely related to the natural latitudinal zonality. According to this principle, 15 peat-bog areas have been identified on the territory of Western Siberia.

The extreme 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 water-resistant 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 a few centimeters. Deeply deposited peatlands should be classified as relics of the Holocene climatic optimum. Polygonal and even moss-sedge bogs are common here.

Noteworthy is the wide distribution of eutrophic moss-sedge bogs with a flat surface (up to 20-25% of the total area). It is dominated by Carex stans or Eriophorum angustifolium with a mossy carpet of Calliergon sarmentosum and Drepanocladus revolvens.

In the river valleys among the sedge marshes there are mounds covered with Sph. warnstorfii, Sph. lenense, Dicranum elongatum and lichens. Of the flowering plants, thickets of Betula nana and Rubus chamaemorus are abundant.

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

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

South is located area of ​​flat 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 hillocks ranges from 30 to 50 cm, rarely reaches 70 cm. The area of ​​the hillocks 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. Less common are Cetraria nivalis, C. cucullata, Cladonia amanrocraea. The slopes of the mounds are covered with green mosses. Abundant are Aulacomnium turgidium, Polytrichum strictum, Dicranum elongatum. Of the flowering plants, strongly oppressed Ledum palustre and Rubus chamaemorus grow in clusters. Between them are fragments of dicrane-lichen associations. Hollows are heavily watered with a continuous carpet of sphagnum mosses from Sph. lindbergii, Sph. balticum, Sph. subsecundum, Sph. Jensenii. Less commonly, Drepanocladus vernicosus, Drepanocladus fluitans are found in the hollows; Along with marshes, swampy areas are widespread, which are swampy shrub tundra with Betula papa and willows, sometimes with Ledum palustre, swampy moss tundra with Betula papa and Ledum palustre, tussocky tundra with Eriophorum vaginatum.

Area of ​​large-hilly swamps occupies the northern part of the forest zone and the southern forest-tundra. The swampiness of the zone is high. The hillocks are found singly, but more often they are located in groups or ridges 1-2 km long, up to 200 m wide. Single hillocks have a height of 2-2.5 m, soil hillocks 3-5 m, hillocks of the ridges reach a height of 8-10 m. Diameter bases of mounds 30-80 m, steep slopes (10-20°). Elongated depressions between hillocks are occupied by cottongrass-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 is developed, mainly Betula papa. Higher up the slope, lichens predominate. They are also characteristic of flat tops, which are often subjected to wind erosion.

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

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

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

Areas with well-drained peatlands are insignificant and confined to the territory with the highest surface elevations. Fuscum and pine-sphagnum phytocenoses with a large number of various lichens are common here.

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

The deposits of raised peatlands are shallow, on average about 2 m. slightly decomposed fuscum, complex, hollow types of structure predominate.

Kondinsky peat-bog area It is a vast alluvial and lacustrine-alluvial plain composed of layered sandy and clay deposits. For the left bank of the river The presence of a ridged relief is characteristic of the Konda and the right bank of its lower reaches. The area is characterized by extremely high watering. A significant part of the Kondinsky region is confined to the area of ​​intense tectonic subsidence and, therefore, is 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 waterlogging. The riverbeds are slightly incised. In the spring, the hollow waters of these rivers overflow widely and do not enter the banks for a long time. Therefore, the river valleys are swampy for a long distance; near-terrace swamps are strongly flooded during floods. For the river basin Konda is characterized by the predominance of raised ridge-lake, ridge-lake-hollow and ridge-hollow peat deposits.

Lowland, sedge, reed, reed grass, birch-reed grass peatlands are confined to river beds.

Transitional sedge-sphagnum, tree-sphagnum and sphagnum bogs are found along low terraces and in places where they are articulated into bog systems. There are also complexes that form along the lines of the surface intrafallow runoff of swamp waters.

The gradual tectonic subsidence of the surface affects the extremely high watering of the territory, which contributes to the intensive development of regressive phenomena in the swamps, the destruction of the sphagnum sod 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 covered with peat, but most of them have preserved an open water surface among peaty shores.

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

Transitional types of deposits compose peat bogs mainly of the second terrace of the river. Konda and its tributaries, and also occur along the edges of upland peat deposits, around mineral islands, or are confined to mesotrophic grass and moss swamps. The most common type of deposit is transitional fens.

Low-lying deposits are found in floodplains, forming narrow strips confined to the overgrown rivers of raised bogs.

The analysis of spore-pollen diagrams dates the Konda peatlands to the Early Holocene. The peat bogs have an ancient Holocene age, the deposit depth of which exceeds 6 m.

Middle Ob peat-bog area It is a lacustrine-alluvial and alluvial plain composed from the surface mainly of cover deposits underlain by 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 drained swamps found.

The area is characterized by the dominance of raised sphagnum bogs with ridge-lake-hollow and ridge-hollow complexes. Marsh margins 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 the watersheds of the first order 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 peatlands is represented by a fuscum-deposit or complex upland 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 asymmetric surface, high-moor peatlands show a drop in surface marks 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 structure with a ridge-lake complex of vegetation on the surface. In the direction to the opposite slope of the watershed, the fallow passes into a complex upland one with a ridge-hollow complex in the vegetation cover. A shallow peripheral area with a transitional marsh deposit bears the vegetation of sphagnum marshes on the surface.

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

On watersheds of the second order, 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, on the watersheds of the occurrence, there are large peat deposits of the raised type with a predominance of fuscum deposits and with ridge-lake and ridge-hollow complexes of vegetation on the surface.

Basically, the Middle Ob region, as well as the Vasyugan region located to the south, are territories of almost continuous swampiness. The swamps here completely cover the watersheds of the first and second orders, terraces and floodplains. High-moor 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 watersheds and fourth terraces. They are also found on low terraces and are confined to the hollows of the ancient runoff, where accumulation processes predominate. The deposit is characterized by great homogeneity and is composed of complex high-moor, Scheuchzerian and Fuscum peat.

The deposit of transitional swamps is represented by transitional marshes and forest-marsh 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-Tymskaya peat-bog region occupies the interfluve of the Keti and Tym and extends east to the Yenisei. The watershed of the Ob and Yenisei has a clearly pronounced slope here with an increase in surface elevations to the east. The interfluves are composed of lacustrine-alluvial and deluvial deposits and are divided by a highly developed hydrographic network into a large number of small interfluves.

Due to the fact that the area is located within the contour of positive structures, the predominance of denudation processes causes the spread of well-drained swamps here. Regressive phenomena are less pronounced, there is a tendency for transgression of ridges, or ridges and hollows are in a state of dynamic equilibrium. The surface of the interfluve plateau has a clearly expressed crested 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 the ridges, and in depressions - a transitional marsh or mixed marsh deposit with a lower horizon of low-lying sedge peat 1.5 m thick. Some ridges are manes, towering above a peat deposit that fills depressions between ridges by 2-10 m. The width of ridges is up to 5 km. They are composed of sandy deposits and are usually overgrown with taiga forests of pine, fir, cedar, and birch. The peatlands of the depressions between ridges are represented by transitional marsh and mixed marsh types of structure. On the upper part of the slope of the watershed to the floodplain in the lower reaches of the Keti and Tyma rivers, there are frequent small rounded peatlands of suffusion depressions (from 10 to 100 ha, rarely more) with transitional and upland, less often with low-lying deposits.

The slopes of the watersheds are eroded, weakly dissected or almost undivided by ledges of terraces, covered with a cloak-like peat deposit, 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 a low-lying deposit, higher up the slope - transitional, and in the upper parts of the slope - upland. Rather large lakes with sapropel deposits at the base are scattered on them, more often in the upper part of the slope, among the upper deposits.

In the upper reaches of the Keti and Tyma rivers, narrow terraces of both river valleys are covered with peat. Narrow peatlands stretched along the rivers are more often composed of transitional deposits. Raised slightly 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 rivers Ketyu and Tym. The average thickness of raised bogs is 3-5 m, lowland 2-4 m. Raised bogs are composed of fuscum, complex and Scheuchzeria-sphagnum types of structure. The deposit of mesotrophic swamps is represented by transitional marsh and forest-marsh types of structure. The deposit of lowland bogs is composed of sedge peat.

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

A feature of the Ket-Tym region is the significant distribution of transitional and low-lying peatlands in comparison with other peat-bog areas of the forest zone, where the dominants are exclusively raised bogs.

Tavda peat-bog region It is a flat, in some places 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-Mansiysk lowland, where accumulation processes predominate and the greatest swampiness takes place. In the northwestern outskirts, it enters the limits of the Tavdo-Konda Upland, and in the south - the Tobol-Ishim Plain. The swampiness of the area is high. A significant area is occupied by poorly drained lowland peat deposits, the deposit of which is composed mainly of sedge and sedge-hypnum types of structure with a small participation of deposits of forest-marsh and forest subtypes. The thickness of the deposits is small (2-4 m), occasionally there are peat deposits with a depth of 5 m. On flat watersheds, small raised-type peat bogs are common with deposits 6-7 m thick, often composed almost to the mineral fuscum soil with peat of a low degree of decomposition. There are many lakes on the surface of peat deposits, which at one time served as the centers of formation of the majority of 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 widespread; in the south, subaerial loess-like loams enter its limits. The confinement of the area to the contours of positive structures determines the distribution of relatively drained swamps. Weakly drained swamps occupy the Demyan-Irtysh interfluve and depressions of the Ob-Irtysh watershed, where accumulation processes are developed.

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

Raised sphagnum bogs with ridge-hollow-lake and ridge-hollow complexes are confined to the flat tops of the 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-herbal 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 sections of the watersheds. At the base of the peat bogs lie deoxidized silty calcareous loams, enriching the deposit with a significant amount of mineral salts. The nature of the vegetation cover indicates that a hard water regime is currently taking place. The peatbog 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. types of structure with a deposit thickness of 1 to 2.8 m.

Upland areas in the form of islands lie among the low-lying deposits. Their peat stratum is represented mainly by the fuscum type of structure and reaches a thickness of 6 m. The world's largest watershed heterogeneous peat deposit "Vasyuganskoye" with an area of ​​over 5 million hectares is located in the region. Low-lying peatlands do not form at all in large areas and, in addition to the slopes of watersheds, occupy mainly elongated areas in river valleys.

Low-lying sedge-hypnum bogs predominate on low, heavily swamped terraces; low-lying and transitional woody-sphagnum, woody-herbaceous bogs develop in the terraced part. The floodplains are swamped mainly in the upper reaches of the rivers, where low-lying sedge, sedge-willow, tree-sedge and forest bogs are formed. In their canopy under birch canopy, Carex caespitosa and C. wiluica form high tussocks; in interstitial depressions a large number of forbs.

Transitional type deposits are located either at the contact of upland deposits with wetland 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 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 peatlands does not exceed 1.5-2 m. Their deposit of sedge, Scheuchzeria, wood-sedge or birch peat was in conditions of variable moisture with the participation of river waters, therefore its ash content is relatively increased.

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 have the Old Holocene age.

Ket-Chulym peat-bog region characterized by less peatiness compared to the Ket-Tymskaya, which finds its explanation in the geomorphological features of the area. The watershed Ket-Chulym plateau has a much 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 peatlands. The most widespread in peat bogs of suffusion depressions is the transitional marsh deposit with a total thickness of the peat layer from 1 to 4.5 m. Raised deposits are less common in them, mainly fuscum, complex and Scheuchzeria-sphagnum with a depth of up to 3-6 m. 1-2 m deep are occupied by cottongrass-sphagnum or Magellanicum-deposit. Lowland deposits in suffusion depressions are rare and are represented by forest, tree-sedge, multilayer forest-marsh and sedge types of structure. They fill the deepest hollows, in which the thickness of the peat suite reaches 4-5 m.

In the Ket-Chulym region, there is a certain regularity in the placement of near-terrace peat deposits. In the middle part of the river Ulu-Yul peatlands are small and located on sharply defined terraces. Downstream the river, the terrace ledges are smoothed out, the surfaces of the terraces are expanding, and the areas of peat deposits are also increasing. The latter acquire an elongated shape and are extended parallel to the river. Near the mouth of the river Ulu-Yul terraces are even weaker and peat deposits merge with each other, covering the surface of several terraces.

On terraces and in the terraced parts of river valleys, peat bogs are smaller in size (compared to the peat bogs of the Ket-Tym region) and, without merging into large massifs, form on the terraces chains of disconnected deep-lying peat deposits extended parallel to the river, often of a low-lying type with forest, tree-sedge or sedge deposit.

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

In general, this area is highly swampy, slightly dissected, gently flat, wide river valleys with large low-lying sedge-hypnum bogs at the foot of the terraces and along their slopes, and with medium-sized raised and transitional peat bogs on the watersheds. The total swampiness of the region is up to 40%.

An example of a peat deposit of the first floodplain terraces 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 bedrock bank. Its deposit is almost entirely composed of sedge-hypnum and sedge peat, confirming the existence of subsoil 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 the forest-steppe conditions during the formation of the lakes. In the lower horizons of the deposit or on the margins of the deposit, a high ash content of peat is observed as a result of clogging of the deposit with deluvial drifts.

North Baraba peat-bog area watershed sedge-hypnum bogs in the north borders on the Vasyugan peat-bog region, in the south on the South Baraba and is a gently undulating, slightly dissected plain. The region is composed of loess-like loams. The porosity is small. It is dominated by medium-sized low-lying peatlands of the type of borrowings with an area of ​​10 to 100 ha. 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 peaty area is low-lying peatlands (54%) and about 27% is raised; the percentage of transitional peatlands is relatively high here (19%).

There are many lakes, depressions and peat deposits in the central part of the region. In the western part of the region, on the slopes of the Tara-Tartas interfluve, the main area of ​​sedge-hypnum bogs is concentrated. Hypnum swamps develop in low relief elements, mainly in the places where ground hard water flows emerge, along the slopes of watersheds, or in the terraced parts of river valleys. Therefore, a slightly increased ash content (up to 8-12%) is inherent in hypnum peat and peat deposits. The ash content of some terraced hypnum peatlands averages 6-7%. The ash content of the sedge-hypnum peat bogs of the Tara-Tartas interfluve is also measured by the same percentage.

To the east, sedge-hypnum peatlands yield their leading position in the lowland type to forest-marsh and forest deposits. The latter are located here along the edges of peat deposits, on central sections which, as well as in areas with a more elevated bottom topography, there are islands of upper deposits. Moreover, the fuscum fallow is usually peripheral in relation to the complex upland, 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, feeding from atmospheric precipitation, and partial uplift of the territory create favorable conditions for the gradual transition of lowland bogs to the oligotrophic stage of development. In the river valleys immediately adjacent to the river ridges, the richest in floristic composition woody-grass bogs (sogry) are common. In that part of the valley where anoxic groundwater flows and deluvial waters do not penetrate, sedge-hypnum bogs are formed. In addition to typical moss, there are sedge and sedge-grass bogs, and in the east - reed bogs, characteristic of the grass bogs zone.

In the riverine parts of the watersheds, along the banks of the upper reaches of the rivers, in the depressions of the 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 (upper sphagnum islands) is a characteristic feature of the sedge-hypnum bogs of the North Baraba region. The hypnum deposit is more characteristic of swamps of low terraces, where soluble calcium salts predominate in water and mineral nutrition. The bog deposit of the watershed plains differs from the peat bog deposit of low terraces in terms of high rates of decomposition and ash content, which has a more complex stratigraphy. There are grass-hypnum, cottongrass-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 take a significant part in the structure of the deposit of lowland near-terrace and floodplain-terrace bogs. Transitional forest swamps are widespread. They are formed in the interfluves, in the terraces above the floodplains and in the terraced parts. The deposit of these swamps is represented by transitional forest and forest-marsh types of structure.

In the pits, 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 peat species. The bottom layers of the deposit are usually represented by peat of transitional and lowland types. The average depth of the peat deposit on the 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-forming 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 low-lying swamps of the type of borrowings with an area of ​​10 to 100 hectares. The confinement to the positive contours of the structures determines the development of predominantly well-drained peat deposits here.

The hryvnia nature of the relief, a poorly developed hydrographic network, a waterproof horizon close to the surface, and a slow runoff of surface waters led to the formation of a huge number of lakes, usually round or oval, with shallow depths, a flat bottom, and strong overgrowth in the spaces between the hryvnias. The lakes are often adjoined or surrounded by small-sized shallow sedge-reed bogs-bogs. During the period of snowmelt, the lakes are flooded with melt water, turning into temporary shallow water bodies, often connecting with each other, and then the flow along such a chain of lakes connected by lakes has the character of a river. There are very few isolated lakes. According to the chemical composition of the waters of the lakes, sometimes located in close proximity to one another, they are distinguished by considerable diversity. Nearby lie salty, bitter and fresh lakes.

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

Less large-sized 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, less often the sedge association, dominates in their vegetation cover.

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

In small basins of suffosis of ionic origin, there are shallow "chopping" peat bogs of the lowland type. They developed in solonetz microrelief depressions - "saucers". Salinization and the subsequent process of bogging leads to the appearance in them of areas that are exclusively characteristic of this area of ​​marshy meadows with Carex intermedia, which are subsequently covered with thickets of shrubs, mainly Salix sibirica, and birch stands.

There are also treeless "choppy" swamps with sedge hummocks on the surface, surrounded by tall birch along the periphery. They formed in deeper and more humid depressions with diverse wetland vegetation, which varies greatly in composition in some cases: with tussocks of Carex omskiana, sometimes with Salix sibirica in the shrub layer. Such peatlands are never covered by birch over the entire area; the deposit in them is tree-sedge.

South Baraba peat-bog region large peat-ryam bogs 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.

The processes of salinization of soils (including peat ones) are widely manifested 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 a southwestern direction in combination with depressions between ridges. 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, depressions between ridges are completely swamped. The relief of Baraba is characterized by suffusion depressions on various surface elements and a large number of lakes, different in size, origin and chemical composition of water.

The swampiness of the area is approximately 33%. Low-lying reed-sedge peatlands predominate here, accounting for up to 85% of the total wetland area. The remaining 15% is distributed between the upper deposits of the ryams and the transitional deposits of their peripheral areas.

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

The occurrence of high-lying deposits of ryams among the lowland deposits is associated with the feeding of ryam sites with fresh and slightly saline lacustrine 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 deposits in the form of a thin layer of sapropel.

The degree of decomposition of borrowing peat, as a rule, exceeds the species index (30-50%), the average ash content is 20%. The deposit of borrowings is composed of highly mineralized peats of the marsh group: reed, reed-sedge and herbaceous (with a predominance of remains of svetluka and reed grass in the fiber). The total thickness of the borrowing deposits reaches 1.5 m. In the vegetation cover, reed, sedge-reed and sedge (or grass-sedge) phytocenoses are successively replaced in the direction from the center to the periphery. The latter borders on solonchak meadow vegetation. The areas fed by lake waters did not feel any variability in moisture and salt regime. Protected from the influence of saline groundwater by the low-lying deposits surrounding them, they were overgrown with Sph. teres, water bodies passed into the stage of a peat bog, gradually, as the deposits increased, they got out of the influence of lake waters and continued to develop as peat bogs of atmospheric nutrition. The dominance of Sph. fuscum maintains in fallow mode high humidity and low temperature. sp. fuscum created its own substrate and microclimate even in forest-steppe conditions, and over the course of millennia it deposited powerful deposits of high-moor peat.

The modern vegetation cover of the ryams is secondary and arose under the influence of man. The degree of decomposition of the Fuscum deposit is always low, which, in addition to high humidity and low temperature, apparently contributes to its increased acidity, which inhibits microbiological processes. At the contact of the ryams and the borrowing proper, there is usually a belt of transitional fallow with a mesotrophic vegetation cover.

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

Transitional and lowland forest swamps usually form a narrow belt around ryams or are confined to mesorelief depressions. In the latter case, forest swamps are genetically related to birch groves. Kolochny bogs with a predominance of Carex intermedia are typical of the southern part of the region. Birch-reed bogs here are confined to flat, highly mineralized lowlands and represent one of the initial phases of bogging. 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 3.1 m thick ryam is dated to the Middle Holocene, and the 1.35 m deep deposits are dated to the Late Holocene. The swamping processes are promoted by the gradual tectonic uplift of the area, which causes the disintegration of rivers and lakes into separate reservoirs.

East of the river Yenisei within the Asian part of the Union, seven large natural geographical areas are distinguished.

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

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

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

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

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

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

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

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

Geological structure and history of the development of the territory

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

Relief

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

Scheme of the main orographic elements of the West Siberian Plain

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

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

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

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

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

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

Climate

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

Western Siberia is a country with a fairly severe continental climate. Its large extent from north to south causes a distinct climate zoning and significant differences climatic conditions northern and southern parts of Western Siberia, associated with a change in the amount of solar radiation and the nature of the circulation of air masses, especially western transport flows. The southern provinces of the country, located inland, on long distance from the oceans, are characterized, in addition, by a greater continental climate.

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

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

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

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

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

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

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

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

Water

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

Soils, vegetation and wildlife

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

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

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

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

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

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

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

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

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

Natural resources

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

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

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

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

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

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

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

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

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

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

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

Oil and gas fields of Western Siberia

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

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

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

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

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

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

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

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

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

Relief

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

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

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

Climate

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

surface water

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

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

Landscape types

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

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

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

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

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

Environmental issues and protected natural areas

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

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

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

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

Geological structure and history of development

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

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

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

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

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

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

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

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

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

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

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

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

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

Sources

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

Literature

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

1. Geographic location.

2. Geological structure and relief.

3. Climate.

4. Internal waters.

5. Soil and vegetation cover and fauna.

6. Natural areas.

Geographical position

The boundary of the West Siberian Plain is clearly expressed in the relief. Its boundaries in the West are the Ural Mountains, in the east the Yenisei Ridge and the Central Siberian Plateau. In the north, the plain is washed by the waters of the Kara Sea, the southern edge of the plain enters the territory of Kazakhstan, and the southeast borders on Altai. The area of ​​the plain is about 3 million km2. the length from north to south is almost 2500 km, from west to east 1500-1900 km. The southern part of the plain is the most mastered by man, its nature has been changed to some extent. The northern and central part of the plain began to be developed in the last 30-50 years in connection with the development of oil and gas.

Geological structure and relief

The geological structure of the plain is determined by its position on the Paleozoic West Siberian plate. The foundation of the slab is a huge depression with steep sides. It consists of the Baikal, Caledonian and Hercynian blocks, broken by deep faults. In the north, the foundation lies to a depth of 8-12 km. (Yamalo-Tazovskaya syneclise), in the middle part the depth is 3-4 km. (Sredneobskaya anteclise), to the south, the depth of occurrence decreases. The cover of the plate is represented by Mesozoic and Cenozoic deposits of continental and marine origin.

The territory of the West Siberian plate has repeatedly been subjected to transgressions. The glaciation of Western Siberia was repeated many times: Demyanskoe, Samarovskoe, Tazovskoe, Zyryanskoe and Sartanskoe. Glaciers moved from 2 centers: from the Polar Urals and the Putorana plateau. Unlike the Russian Plain, where melt water flowed south, in Western Siberia, which has a general slope to the north, these waters accumulated at the edge of the glacier, forming near-glacial reservoirs. In areas free of ice, there was a deep freezing of the soil.

The modern relief of the plain is due to geological structure and the influence of exogenous processes. The main orographic elements correspond to the tectonic structures of the plate, although the accumulation of Meso-Cenozoic strata has leveled the unevenness of the basement. The absolute heights of the plain are 100-150 meters, while within the plains alternating highlands and lowlands. The general slope of the plain is towards the north. Almost the entire northern half of the plain is less than 100 meters high. The marginal parts of the plain are raised up to 200-300 meters. These are the North Sosvinskaya, Verkhnetazovskaya, Lower Yenisei uplands, the Ob plateau, the Ishim and Kulunda plains. The Siberian Ridges are distinctly expressed in the middle part of the plain, extending from the Urals to the Yenisei near 63˚N, their average height is 100-150 meters. The lowest areas (50-100 m) are located in the northern parts of Western Siberia. These are Nizhneobskaya, Nadymskaya, Purskaya, Tazovskaya, Kondinskaya, Sredneobskaya lowlands. Western Siberia is characterized by: marine accumulative plains (on the Yamal and Gydan Peninsulas), glacial and water-glacial plains with moraine hills, ridges, etc. (central part of Western Siberia), alluvial lacustrine plains (valleys of large rivers), denudation plains (southern part of Western Siberia).

Climate

The climate of Western Siberia is continental, arctic and subarctic in the north and temperate in the rest of the territory. It is more severe than on the Russian Plain, but softer than in Eastern Siberia. Continentality increases towards the southeast of the plain. The radiation balance is from 15 to 40 kcal/cm2 per year. At the same time, in comparison with the Russian Plain, Western Siberia receives somewhat more solar radiation, due to the lower frequency of cyclones. The western transfer persists, but the influence of the Atlantic is noticeably weakened here. The flatness of the territory promotes deep meridional air exchange. In winter, the climate is formed under the influence of the spur of the Asian High, which stretches along the south of the plain and depression of low pressure over the northern peninsulas. This contributes to the removal of cold continental air from the Asian High to the plain. Winds are dominated by southerly directions. In general, January isotherms are submeridian, from -18˚-20˚С in the west to almost -30˚С in the Yenisei valley. The absolute minimum of Western Siberia is -55˚С. Snowstorms are typical in winter. During the cold period, 20-30% of precipitation falls. Snow cover is established in the north in September, in the south - in November and lasts from 9 months in the north to 5 months in the south. The thickness of the snow cover in the forest zone is 50-60 cm, in the tundra and steppe 40-30 cm. In summer over Western Siberia, the pressure gradually decreases to the southeast. Winds prevail in a northerly direction. At the same time, the role of western transfer is enhanced. July isotherms take latitudinal directions. In the north of Yamal, the average July temperature is +4˚С, near the Arctic Circle +14˚С, in the south of the plain +22˚С. Absolute maximum +45˚С (extreme south). The warm period accounts for 70-80% of precipitation, especially in July-August. Droughts are possible in the south. The largest amount of precipitation per year (550-600 mm) falls in the middle reaches of the Ob from the Urals to the Yenisei. To the north and south, the amount of precipitation decreases to 350 mm. The climate of Western Siberia contributes in many respects to the maintenance of permafrost. The northern and central parts of Siberia (more than 80% of its area) have a moisture coefficient greater than 1 (excessive moisture). Such conditions lead to the development of swamping of the territory. In the south, the coefficient is less than 1 (insufficient moisture).

Inland waters

Western Siberia is characterized by a huge accumulation of inland waters. Several thousand rivers flow on the plain, most of which belong to the Ob basin and, accordingly, the Kara Sea. Few rivers (Taz, Pur, Nadym, etc.) flow directly into the Kara Sea. In the south of the plain there are areas of internal (closed) runoff. All rivers of Western Siberia are characterized by small slopes, with a predominance of lateral erosion. The food of the rivers is mixed, with a predominance of snow, in addition, there is rain and swamp-soil. High water runs from April in the south to June in the north. The rise of water reaches a maximum of 12 meters on the Ob, and 18 meters on the Yenisei. A protracted flood is characteristic, despite the “friendly” spring. The rise is fast, but the fall is very slow. Freeze lasts up to 5 months in the south and up to 8 months in the north. Ice jams are typical. The largest rivers are the Ob and Yenisei. The length of the Ob from the source of the Irtysh is 5410 km, and the basin area is 3 million km2. If we consider the Ob from the confluence of the Biya and Katun rivers, then its length is 3650 km. In terms of water content, the Ob is second only to the Yenisei and the Lena. The Ob flows into the Ob Bay (estuary). The largest tributary is the Irtysh, and its tributaries are the Ishim, Tobol, Konda. The Ob also has tributaries - Chulym, Ket, Vasyugan, etc. The Yenisei is the most abundant river in Russia, its length is 4092 km, the basin area is 2.5 million km2. Only a small left-bank part of the basin lies on the territory of Western Siberia. There are about 1 million lakes on the plain. The lake content varies from 1% in the south to 3% in the north. In the Surgut Lowland it reaches 20%. In the south, the lakes are brackish. The largest lake is Chany. It is dry and salty. The maximum depth is 10 m. Swamps occupy about 30% of the territory of Western Siberia. In some places in the forest zone, swampiness reaches 80% (forested swamp zone). The development of swamps is facilitated by: flat relief, poor drainage, excessive moisture, prolonged floods and permafrost. The swamps are rich in peat. According to hydrogeological conditions, the plain is the West Siberian artesian basin.

Land cover and fauna

Soils are arranged as follows from north to south: tundra-gley, podzolic, sod-podzolic, chernozem and chestnut. At the same time, large areas due to waterlogging are occupied by semi-hydromorphic soils. Therefore, most soils, in contrast to their analogues on the Russian Plain, have signs of gleying. Solonetzes and solods are found in the south. The vegetation of Western Siberia is to some extent similar to the vegetation of the Russian Plain, but there are differences that are associated with the wide distribution of swamps, the severity of the climate and the peculiarities of the flora. Along with spruce and pine forests, fir, cedar and larch forests are widespread. In the forest-tundra, larch dominates, and not spruce, as on the Russian Plain. Small-leaved forests here are not only secondary, but also indigenous. Mixed forests here are represented by pine-birch. Large areas in Western Siberia are occupied by floodplain vegetation (more than 4% of the plain area), as well as swamp vegetation. The animal world has many similarities with the Russian Plain. In Western Siberia, there are about 500 species of vertebrates, including 80 species of mammals, 350 species of birds, 7 species of amphibians and about 60 species of fish. A certain zonality is observed in the distribution of animals, but along the ribbon forests along the rivers, forest animals penetrate far to the north and south, and inhabitants of polar water bodies are found on the lakes of the steppe zone.

natural areas

Natural areas on the plain extend latitudinally. Zoning is pronounced. Zones and subzones change gradually from north to south: tundra, forest-tundra, forests (forest-bogs), forest-steppe, steppe. Unlike the Russian Plain, there is no zone of mixed and broad-leaved forests, a zone of semi-deserts and deserts. The tundra stretches from the coast of the Kara Sea and almost to the Arctic Circle. The length from north to south is 500-600 km. The polar day and night last here for almost three months. Winter from October to mid-May. The average temperature is from -20˚C in the west to -30˚C in the east. Characterized by winds and blizzards. The snow cover lies for about 9 months. Summer lasts not much more than one month. The average August temperature is +5˚C, +10˚C (but sometimes the air can warm up to +25˚C). Precipitation per year is 200-300 mm, but most of it is in the warm period. Permafrost is ubiquitous, so the tundra is characterized by solifluction processes, thermokarst, polygons, peat mounds, etc. Lots of swamps and lakes. The soils are tundra-gley. Flora is not rich, only about 300 species higher plants. Vegetation is especially poor on the coast of the sea, where lichen arctic tundra from cladonia, etc. and lichens grow dwarf birch, willow, alder; in some places on the southern slopes and river valleys - buttercups, flames, crowberry, polar poppy, etc. Reindeer, wolves, arctic foxes, lemmings, voles, white partridges, snowy owls live in summer; many marsh and waterfowl (waders, sandpipers, ducks, geese, etc.).

The forest tundra stretches in a relatively narrow strip (50-200 km), expanding from the Urals to the Yenisei. It lies along the Arctic Circle and descends further south than on the Russian Plain. The climate is subarctic and more continental than in the tundra. And although the winter here is somewhat shorter, it is more severe. The average temperature in January is -25-30˚C, the absolute minimum is up to -60˚C. Summers are warmer and longer than in the tundra. The average July temperature is +12˚C+14˚C. Permafrost is everywhere. Therefore, again, the permafrost relief prevails, and erosion processes are limited. The zone is crossed by many rivers. The soils are gley-podzolic and permafrost-taiga. To the tundra vegetation here are added sparse forests of larch (their height is 6-8 meters). Dwarf birch is widespread, there are many swamps, and floodplain meadows in river valleys. The fauna is richer than in the tundra, along with representatives of the tundra fauna, there are also inhabitants of the taiga.

Forests (taiga) occupy the largest area of ​​Western Siberia. The length of this zone from north to south is 1100-1200 km, almost from the Arctic Circle to 56˚N. on South. Here, there is an almost equal ratio of forests on the podzolic soils of the taiga and peat-bog soils of sphagnum bogs. Therefore, the taiga of Western Siberia is often called the forest-bog zone. The climate is temperate continental. Continentality increases from west to east. The average January temperature varies from -18˚C in the southwest to -28˚C in the northeast. In winter, anticyclonic weather prevails. Cyclones often pass through the north of the taiga zone. The thickness of the snow cover is 60-100 cm. The summer is relatively long, the growing season is from 3 months. in the north up to 5 months. on South. The average July temperature is from +14˚C in the north to +19˚C in the south. More than half of all precipitation falls in summer. The moisture coefficient is greater than 1 everywhere. Permafrost is widespread in the north of the zone. Lots of swamps and rivers. Bogs of various types, but ridge-hollow peat bogs predominate, there are ridge-lake and swamp bogs. The swamps are confined to the lowest places with stagnant moisture. On the hills, ridges of interfluves, on the terraces of river valleys, coniferous forests of spruce, fir, and cedar grow. In some places there are pine, larch, birch, aspen. To the south of the taiga, 50-200 km wide, stretches a strip of small-leaved forests of birch and, to a lesser extent, aspen, on soddy-podzolic soils. The fauna is represented by Siberian species, but there are also "Europeans" (marten, European mink, otter). The most typical - Brown bear, wolverine, lynx, sable, chipmunk, squirrel, fox, wolf, water rat, elk, many birds whose life is associated with coniferous forest (nutcracker, smurf, kuksha, capercaillie, woodpeckers, owls, etc.), but songbirds little (hence the name "deaf taiga").

The forest-steppe stretches in a narrow strip (150-300 km) from the Urals to the Salair Ridge and Altai. The climate is temperate continental, with severe winters with little snow and hot dry summers. The average temperature in January is -17˚C-20˚C, and in July +18˚C+20˚C, (maximum +41˚C). Snow cover 30-40 cm, annual precipitation 400-450 mm. The moisture coefficient is less than 1. Suffosion processes are typical, there are lakes, some of which are saline. The forest-steppe is a combination of aspen-birch copses on gray forest soils and areas of meadow steppes on chernozems. The forest cover of the zone is from 25% in the north to 5% in the south. The steppes are mostly plowed up. The fauna is represented by forest and steppe species. In the steppes and floodplain meadows, rodents predominate - ground squirrels, hamsters, earth hare, voles, there is a hare. Foxes, wolves, weasels, ermines, polecats, white hare, roe deer, black grouses, partridges are found in the groves, in reservoirs there are a lot of fish.

The steppe zone occupies the extreme south of Western Siberia. Unlike the steppes of the Russian Plain, there are more lakes here, the climate is more continental (little precipitation, cold winters). The average temperature in January is -17˚C-19˚C, and in July +20˚C+22˚C. The annual rainfall is 350-400 mm, with 75% of precipitation falling in summer. Moisture coefficient from 0.7 in the north to 0.5 in the south of the zone. In summer, there are droughts and hot winds, which leads to dust storms. The rivers are transit, small rivers dry up in summer. There are many lakes, mostly of suffusion origin, almost all of them are salty. The soils are chernozem, dark chestnut in the south. There are salt marshes. The plowing of the steppes reaches 90%. Various feather grass, fescue, thyme, sagebrush, wormwood, iris, steppe onion, tulip, etc. grow in the preserved areas of the steppes. wet places there are shrubs of caragana, spirea, wild rose, honeysuckle, etc., along the river valleys pine forests come to the south. In the floodplains of the rivers there are swampy meadows. The fauna is represented by various rodents (ground squirrel, hamster, marmots, voles, pikas, etc.), predators include steppe polecat, corsac, wolf, weasel, birds - steppe eagle, buzzard, kestrel, larks; on the lakes - waterfowl. Four reserves have been created in Western Siberia: Malaya Sosva, Yugansky, Verkhne-Tazovsky, Gydansky.

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