The East European Plain is part of the East European Platform. This is an ancient and stable block, bordering on the east, the platform is framed by the Urals. The tectonic structure of the East European Plain is such that in the south it is adjacent to the Mediterranean folded belt and the Scythian plate, which occupies the space of Ciscaucasia and Crimea. The border with it runs from the mouth of the Danube, along the Black and Azov Seas.
Tectonics
Older and harder Permian and Carboniferous limestones come to the surface on the banks of the Samarskaya Luka. Strong sandstones should also be distinguished among the deposits. The crystalline foundation of the Volga Upland is lowered to a great depth (about 800 meters).
The closer to the Oka-Don lowland, the more the surface decreases. The Volga slopes are steep and dissected by numerous ravines and gullies. Because of this, a very rugged terrain has formed here.
and the Oka-Don lowland
The common Syrt is another important part of the relief that distinguishes the East European Plain. Photos of this region on the border of Russia and Kazakhstan show an area of chernozem, chestnut soils and solonchaks, prevailing on watersheds and in river valleys. The common Syrt begins in the Trans-Volga region and extends 500 kilometers to the east. It is mainly located in the interfluve of the Big Irgiz and the Small Irgiz, adjoining the Southern Urals in the east.
Between the Volga and Central Russian uplands is the Oka-Don lowland. Its northern part is also known as Meshchera. The northern boundary of the lowland is the Oka. In the south, its natural boundary is the Kalach Upland. Main part lowlands - Oksko-Tsninsky shaft. It stretches through Morshansk, Kasimov and Kovrov. In the north, the surface of the Oka-Don lowland was formed from glacial deposits, and in the south, its basis is sands.
Valdai and Northern Uvaly
The vast East European Plain lies between the Atlantic and Arctic oceans. The basins of the rivers flowing into them begin on Her highest point- 346 meters. Valdai is located in the Smolensk, Tver and Novgorod regions. It is characterized by hilly, ridge and moraine relief. There are many swamps and lakes (including Seliger and Upper Volga lakes).
The northernmost part of the East European Plain is the Northern Ridges. They occupy the territory of the Republic of Komi, Kostroma, Kirov and Vologda regions. The upland, consisting of hills, gradually decreases in a northerly direction until it rests on the White and Barents Seas. Her maximum height- 293 meters. Northern Uvaly is the watershed of the Northern Dvina and Volga basins.
Black Sea lowland
In the southwest, the East European Plain ends with the Black Sea Lowland, located on the territory of Ukraine and Moldova. On the one hand, it is limited by the Danube Delta, and on the other, by the Kalminus River of Azov. The Black Sea lowland consists of Neogene and Paleogene deposits (clays, sands and limestones). They are covered with loams and loess.
The lowland is crossed by the valleys of several rivers: the Dniester, the Southern Bug and the Dnieper. Their banks are characterized by steepness and frequent landslides. On the sea coast many estuaries (Dniester, Dnieper, etc.). Another recognizable feature is the abundance of sandbars. The steppe landscape with dark chestnut and chernozem soils prevails in the Black Sea Lowland. This is the richest agricultural granary.
The superimposed landforms of the East European Plain are associated with the spread of cover Quaternary deposits and are mainly of glacial origin.
By the beginning of the Pleistocene, the East European Plain had a denudation surface, on which a hydrographic network loomed in its main features. Rivers, as the most sensitive reagent, reflected the features of the structure and lithology of the eroded substrate by the location of their valleys. Reflected relief had the greatest influence on the formation and location of the river network. The main rivers gravitated towards syneclises. During the development of river valleys, the location of watersheds was determined by the structure of the substrate. Denudated positive elements of the structure form the most elevated watershed parts of the East European Plain.
The Baltic-Caspian watershed acts as the Valdai Upland. It stretches along the monoclinal ridge of deposits of the Carboniferous system, which limits the Moscow syneclise from the west. The Baltic-Black Sea watershed stretches along the northwestern slope of the Belarusian anteclise and is roughly located along the foot of the northern slope of the monoclinal ridge of Cretaceous and, to the west, Jurassic deposits. In a significant part of the lower reaches, the Neman flows along this structure.
The White Sea-Caspian watershed stands out in the relief of the East European Plain as the Northern Uvaly Upland. The main watershed of the East European Plain runs mainly within the Moscow syneclise, along its northern side. The watershed upland is asymmetric. In the northern part, its surface lies at an altitude of 230-270 m, in the southern part - 280-300 m above sea level. The Moscow syneclise as a whole is characterized by an inversion relief. The main watershed of the East European Plain of erosional origin.
The Black Sea-Caspian watershed is asymmetric, displaced far to the east, and runs along the ridge of the highly eroded Volga Upland along the steep right bank of the Volga.
The erosional relief of the East European Plain developed towards the end of the Early Pleistocene. Its distribution expanded following the retreat of the seas of the Neogene period and, after the Kuyalnik time, ended with the formation of modern river basins and ancient valley-beam relief. By the beginning of the glaciation, the relief of the East European Platform was strongly dissected and had a large amplitude of elevation fluctuations compared to the modern one. The coastline of the Black Sea was located about 100 m below the modern one. In accordance with this position of the basis of erosion, the rivers deepened their valleys.
Sea levels fluctuated periodically throughout the Pleistocene. As much as possible, he rose up to 40 m above his current situation. The territory of the East European Plain between the coastline and the glaciation front was an arena of humid non-nival (periglacial) relief formation. It is well known that the boundaries of the distribution of the ice sheet in the Pleistocene also shifted significantly. This is reflected in the patterns of distribution of glacigenic landscapes, in the structure of the terraces of river valleys and the cover of Quaternary deposits developed on them. However, the synchronization of the main factors of Quaternary sedimentation and relief formation remains hotly debated. In particular, the question of the relationship between the transgression of the sea of the Black Sea-Caspian basin and the phases of glaciation remains controversial. Taking Black and Caspian Sea as closed, at that time internal basins, the level of which is determined by the runoff of melted glacial waters, their transgression can be attributed to the phases of glaciation and its retreat (Bondarchuk, 1961, 1965). Many are of the opinion that sea levels rise during the interglacial.
In the Quaternary period, on the territory of the East European Plain, glacial deposits accumulated mainly in the area of syneclises and river valleys. The formation of superimposed accumulative plains is associated with them.
Glacigenic superimposed forms. The Pleistocene glaciation of the East European Plain developed in waves - phases that lasted tens of thousands of years. The first cooling waves first covered the high-mountain regions. A further decrease in the snow line caused the glaciers to slide into the foothills and the development of a long-term snow cover on the plain. In the Mindel time, it is possible that the ice cover captured the north-west of the platform, to the south - it connected with the glaciation of the foothills of the Carpathians. Glaciers filled the Dniester and Dnieper valleys, as evidenced by powerful accumulations of fluvioglacial pebbles in the Dniester valley. In the valley of the Dnieper, the glacier spread below Kanev. A moraine of the Mindelian age was exposed here during the digging of the pit of the Kanev hydroelectric power station. In the era of the Dnieper (ris) glaciation on the territory of the East European Plain, the ice cover along the Dnieper valley slid down to Dnepropetrovsk. Ice sheet covered most platforms, but the finite moraine formations of this glaciation are almost unknown. In the retreat of the Dnieper glaciation, there was a stage when the edge of the glacier was located in the basin of the lower reaches of the Pripyat - the upper reaches of the Desna, known in the literature as the Pripyat, or Moscow, glaciation. The edge of the Pripyat glacier stretched along the Dnieper valley to Zolotonosha, where a moraine covered with a layer of medium loess was found in the quarries of a brick factory.
In the late Pleistocene, glaciation took northwestern part East European Plain. With its retreat, the formation of terminal moraines of the stages of the Wurm glaciation is associated: Polissya, or Kalinin, Valdai, or Ostashkov, and Baltic.
The boundaries of the stages of the Wurm glaciation and the location of the ridges of the terminal seas were determined by the structural reflected relief, and above all, by the position of the watersheds. The main obstacles to the advancement of ice were the Black Sea-Baltic and Main watersheds, the Valdai Upland, the ledge of the Silurian plateau in the Baltic, and others.
Throughout the glacial zone, the superimposed relief of the East European Plain is characterized by glacial forms. Large spaces covers the bottom moraine, among the hilly formations of which glacial lakes are often included. Drumlin and kame landscapes are widespread in its northwest.
Glacial-exaration landforms are noticeably expressed only on the surface of the Precambrian basement of the Baltic and Ukrainian crystalline shields (for example, the landscape of "ram's foreheads" west of Korosten, worked out by the movement of ice of the Dnieper glaciation). Equally of great geomorphological significance, as well as glacial forms, are the water-glacial accumulative formations of the periglacial zone that make up the loess and sandy plains. Loess superimposed plains occupy large areas in the middle Dnieper region, the Black Sea lowland, in the northern Ciscaucasia. Loess rocks cover significant areas in Belarus, the upper reaches of the Don, the Moscow region, the upper reaches of the Volga and other glacial regions of the East European Plain.
The formation of loess plains is associated with many issues of Quaternary geology, for which there are still no generally accepted solutions: the origin, age and patterns of distribution of loess rocks, the layering of loess and the stratigraphic significance of soil horizons buried in it, the qualitative features of loess proper and loess rocks. The latter definition is still not sufficiently specific and is most often replaced in descriptions by the concept of "loess-like loams", which is quite convenient for characterizing fine-earth cover formations.
Here, loess rocks are considered as geological layers, transitional from geographical envelope to sedimentary layers earth's crust. Therefore, the qualitative features of cover loess rocks, while preserving the main features of the material composition of the geological body, fully reflect the features geographical conditions their education. From the last the main factors topography and climate are considered.
Features of the relief as a foundation for subsequent accumulative superimposed forms have a double meaning. The first is that the accumulation of cover deposits, including loess rocks of the humid zone, is localized in depressions of the structural-tectonic and denudation relief; the second is that the age of the relief is the main criterion for determining the relative age of the overlying deposits developed on it. The principle of stratigraphic subdivision of cover layers according to the geomorphological method is based on the fact that higher levels of relief have an older cover of sediments. This is convincingly seen in the example of sea and river terraces, as well as foothill steps, where in each region the upper terrace is composed of older strata.
Climate features are reflected in the sources of material that feed the provinces in composition, transport, sorting of the skeletal part of loess rocks, conditions of their deposition and stratification. It is believed that the deposition of loess rocks is associated with the glaciation of the East European Plain. It is also generally accepted that the main source of mineral masses for the accumulation of loess rocks was glacial deposits. The cover of loess-like rocks always lies in the periglacial zone, external to the edge of a given glaciation, on flat depressions of the non-glacial relief. On the transport and deposits of loess rocks of the East European Plain and Western countries there are two main points of view. According to the first, the formation of loess is connected with the activity of the wind in the glacial desert; according to another, loess rocks are a product of the deposition of melted glacial waters, which in the warm season overflowed in the glacial plains. The conditions of deposition of loess rocks were similar to those of the floodplain of modern rivers. This point of view has been consistently defended by the author since 1946. No traces of intensive aeolian activity in the Pleistocene have been found on the territory of Europe. The fact that the European loess is not of eolian formation is also confirmed by the distribution of loess rocks occurring in syneclises and in areas gravitating towards river valleys.
The usual layering of loess deposits is not expressed or is hidden. The presence of layering, however, is traced in the horizontal shearing surfaces, cutting off the known columnar separation characteristic of loess rocks.
Sedimentary layering in the loess was transformed by weathering, which followed the accumulation in the cold dry season and frosty, more long periods. Sedimentary layering in loess is especially deformed by soil formation and masked by relatively humus-enriched bands, the number of which increases with increasing thickness of the loess layer, regardless of its age. So, in the section of loess rocks of the buried beam near the village. Vyazovka (Luben district), in the basin of the river. Soult, in the 56.45-meter thickness of loess-like loams, 13 such bands with a total thickness of about 22 m are distinguished. Some parts of the section are colored with humus by 2-3 m. These deposits are distinguished as fossil soils. The formation of buried soil horizons and organically shaded parts of a single loess stratum is mechanically associated with interglacial periods. Proponents of this interpretation of loess stratification admit 11 or more glaciations of the East European Plain in the Pleistocene, despite the fact that there are no data for this.
To use buried soils for stratigraphic comparisons of extraglacial deposits of various glaciation phases and different elements relief, it is necessary to proceed from the really existing pattern of loess distribution and its stratification. In the latter, the enrichment of the loess layer with humus, as a geological body, transitional from the geographic shell to the earth's crust, is inevitable. This is what gave grounds to L. S. Berg and V. A. Obruchev to consider the loess cover as soil. Stand out on general background Loess fossil soils do not witness breaks in the accumulation of loess, but serve as an indicator of sedimentation conditions similar to those of the modern floodplain. In loess rocks on the slopes of anteclises, as well as on slopes in general, in the southern part of the East European Plain, as, indeed, in other loess regions, the cover deposits are more enriched in humus than on the plains, the number of their interlayers is greater, and the thickness is increased. The presence of humus in the overlying sediments can be considered as feature alluvial, proluvial and deluvial sedimentation and explained by the fact that the sedimentation of the loess sequence was accompanied by simultaneous weathering and soil formation, which primarily depended on the variability of the degree of moisture. The basis of the origin of humus bands in loess in most cases is not direct soil formation, but the sorption of humic matter by loess rocks from groundwater solutions. Humusification and, in general, the change in color of loess rocks is associated with the position of the moisture level, as in the modern floodplain, or the changing position of groundwater horizons during the accumulation of loess. The horizons of buried soils covering more elevated areas, including the terraces of loess areas, reworked by excavations, which is typical of the steppe zone, are no exception. The latter circumstance can be used to correlate loess sections of similar geomorphological formations of river and sea terraces in the given area. On the territory of the East European Plain, several age generations of loess are distinguished, the formation and distribution of which is associated with certain phases of glaciation. Superimposed loess plains are adjacent to the boundaries of glaciation and are arranged regularly: they are associated with maximum glaciation, occupy more southern and vast territories, younger loess accumulations move north following the retreating glaciation front and have a cover occurrence in adjacent parts. Within the basins of the main rivers, loess is located on terraces and has a valley distribution. Thus, stratigraphic loess horizons cover a certain area, but are adjacent to older accumulations.
The available data make it possible to identify loess strata of different ages in the loess cover of the East European Plain:
young loess- wurm, includes one or two buried soils, common in Belarus, the Smolensk region, the Moscow region - near Vladimir on the Klyazma;
medium loess- late riss - Pripyat, or Moscow, glaciation, includes one or two or three horizons of buried soils, distributed in the upper reaches of the Oka, Don, Desna, on northern slopes Central Russian Upland and on the high terrace of the Dnieper;
ancient loess- riss - maximum, or Dnieper, glaciation, includes five to six or more horizons of buried soils, covers the entire southwestern part of the East European Plain in the basin of the Lower Danube, Dniester, Dnieper, Donets, Kuban and the entire Black Sea region;
brown, or chocolate, loamy loams- almonds, include one or two horizons of red-brown loams, distributed in the southern part of the European territory of the USSR: red-brown clays- Late Pliocene - Early Anthropogenic, common in the southern part of the East European Plain, but occupy significantly large area than brown underloess loams: there are no anteclises on the elevated parts.
Of the soils contained in the loess, only the soil on freshwater submorainic loams and ancient Euxinian marine sediments can be reliably Mindel-Riss, Nikulin. The buried soil on the Dnieper moraine may correspond to the Odintsovo (Dnieper-Pripyat, Moscow) interstadial.
In addition to flattened loess spaces, eluvial-deluvial deposits also play a significant role in the geomorphology of the East European Plain, covering the slopes of uplands like a thick cloak. They are often represented by loess-like rocks, strongly enriched in humus, which form many interlayers of buried soils. Deluvial areas soften the relief of hills and ledges of terraces, create smooth transitions from watershed ridges to loess lowlands. The anteclise vaults are mostly devoid of any cover of loose formations on the weathered bedrock exposed there.
sandy plains. Among the superimposed landforms in the landscapes of the East European Plain, sand formations occupy a significant place. Powerful strata of sands are of glacial, alluvial, lacustrine and marine origin. Subsequently reworked by the wind, they created a monotonous bumpy relief. Significant outwash fields are associated with belts of terminal moraines different phases glaciation. Fluvioglacial sands occupy large areas in Polissya, especially in the Pripyat and Teterev basins.
In river valleys, fluvioglacial sands pass into alluvial deposits of the first floodplain terraces. Sandy terraces are well expressed along most of the rivers of the East European Plain.
Sands occupy vast areas in coastal areas. In the Baltics, dune landscapes are well expressed in Kaliningrad region, on the Riga coast, Sarema Island, etc. In the Black Sea region, dune sands are common on the bays of estuaries, occupy a large area in the lower reaches of the Dnieper and Danube. Considerable areas are covered by hilly sands in the Caspian lowland. Their largest arenas are concentrated in the lower reaches of the Terek and Kuma, in the lower reaches of the Volga, between the Volga and the Urals. Sands are almost devoid of vegetation and are characterized by a variety of elementary forms common to arid climate zones.
The formation of sedimentary and sedimentary-volcanic cover on the East European platform began in the Precambrian. High degree The planning of the crystalline basement already took place before the Krivoy Rog time. In the Proterozoic, a sedimentary-volcanogenic cover was formed in the southern part of the platform, from which the remnant Ovruch Ridge has been preserved.
In the tectoorogeny of the post-Cambrian sedimentary complex of the East European Platform, a number of stages in the formation of structural relief and its denudation processing are distinguished. Traces of this development are expressed in the presence of numerous surfaces of stratigraphic unconformity and the distribution of sedimentary strata on the platform from the Riphean to the Neogene age. The study of them is the task of historical geomorphology. Only the main points are noted here.
In the Late Paleozoic, during the Hercynian orogeny, the main features of the structure and orography of the East European Platform and adjacent territories emerged. The Donetsk and Timan ridges stood out, monoclinal ridges took shape in the north-west of the country, the elevations represented the Volga region, the High Trans-Volga region, the Ukrainian crystalline shield, the Voronezh anteclise, etc. The Ural Mountains rose in the east of the country, and the European Hercynides stretched in the south-west. In the early Mesozoic, there was a vigorous leveling of the surface of the East European Plain. The landscapes of the country were dominated by denudation landforms, their relics are the ancient valleys of the North. Dvina, Sukhona, etc.
At the end of the Middle and at the beginning of the Late Mesozoic, the central and southern parts of the East European Platform underwent a long stage of marine sedimentation.
The marine environment, gradually shrinking and receding to the south, existed from the Jurassic to the Pliocene. The most important stages maritime development The sedimentary cover of the platform in the post-Cretaceous time was the existence of the Eocene - Kyiv, Miocene - Sarmatian and Pliocene - Pontic basins. As a result of the retreat of the Meso-Cenozoic basins, accumulative plains and geomorphological levels arose on the East European Platform, which are giant steps descending towards the Black Sea.
Following the displacement of the coastline, significant areas of the East European Plain entered a new stage of continental development. In the Cenozoic, erosional relief formed in most of the country.
The first half of the Cenozoic in the history of tectoorogeny of the sedimentary crust in the adjacent mobile zone in the East European Platform ended with the formation of the Crimean Carpathian Mountains and the Caucasus. At the same time, the systems of river valleys finally took shape, the features of the reflected relief loomed.
In the Pleistocene, the structural-denudation surface of the East European Plain became a substrate for the formation of a superimposed relief, gradually acquiring a modern look.
Among exogenous factors, the most important is the energy of the Sun, which determines the climate. Climatic conditions determine the manifestation of the most important exogenous processes - weathering, the activity of ice, wind, water flows, their intensity and expression in the relief. In different climatic conditions different forms of relief appear. Climate change caused the appearance of continental glaciations, eustatic drops in sea level, and transformed the nature of vegetation. In the distribution of climate, latitudinal and vertical zonality is observed. The latter is reflected in the relief. Climatic zoning is observed in the distribution of exogenous forms.
According to the role in relief formation, nival, polar, humid and arid climates are distinguished. Antarctica, Greenland, islands of the Arctic Ocean and mountain peaks have a nival climate. Here precipitation falls in solid form and glaciers form. The main factors in the formation of relief are snow and glaciers. The processes of physical weathering and processes caused by the existence of permafrost are intensively developing. The polar climate is typical for the north of Eurasia and North America, mountains of Central Asia. It is distinguished by dryness, low winter temperatures, little snow, the development of the permafrost zone, and the predominance of physical weathering processes. Humid climate is common in temperate latitudes of the northern and southern hemispheres, on the equator and monsoon regions. A lot of precipitation falls here, planar denudation, chemical weathering develops, erosional and karst forms are formed. The arid climate is developed on the continents between 20 and 30 o C. and yu. sh., in Central Asia and the Namib and Atacama deserts. It is characterized by a low amount of precipitation, high evaporation, the development of temperature weathering, wind activity, and preporation of rocky ledges. The latitudinal zonality of the exogenous relief is complicated by relic relief- forms of the earth's surface, formed in other conditions, in previous geological epochs. For example, glacial landforms on the East European Plain.
Part II. Endogenous processes and relief
LECTURE 4. THE ROLE OF TECTONIC MOVEMENTS OF THE EARTH'S CRUST IN FORMATION OF THE RELIEF
There are two types of tectonic movements: vertical and horizontal. They occur both independently and in interconnection with each other. Tectonic movements are manifested in the movement of blocks of the earth's surface in vertical and horizontal directions, in the formation of folds and faults.
The mechanism of tectonic movements of the earth's crust is explained by the concept of tectonics lithospheric plates. According to this concept, convection currents of heated mantle matter lead to the formation of large positive landforms. In the axial parts of such arched uplifts, rifts are formed - negative graben-like landforms caused by faults. As an example, we can name the East African, Baikal rifts, the rift zone of the Mid-Atlantic Ridge. The inflow of new portions of mantle matter through cracks at the bottom of the rifts causes spreading - the pushing apart of lithospheric plates in the horizontal direction from the axial part of the rifts. Lithospheric plates are called large rigid blocks of the Earth's lithosphere, separated by tectonic ruptures. Horizontal movements of lithospheric plates towards each other lead to their collision with each other. In the process of collision, subduction occurs - the subduction of one plate under the other or obduction - the thrust of the plates one on top of the other. All these processes are accompanied by the formation of deep-sea trenches and island arcs (Japan Trench and the Japanese Islands); major mountain systems like the Andes Himalayas; the collapse of rocks into folds, the emergence of numerous faults, intrusive and effusive bodies. Various types of tectonic movements and the deformations of the earth's crust caused by them find direct or inversion expression in the relief.
Vertical movements. They appear in the formation of folds , discontinuities, slopes. The elementary types of folds are anticlines and synclines. These structures can be expressed in relief in the form of direct and inversion relief. Small and simple anticlinal and synclinal folds form low ridges, uplands and depressions in the relief. The developing syncline forms accumulative plains. Larger folded structures - anticlinoria are represented in the relief by large mountain ranges and depressions separating them (Fig.). For example, the anticlinorium of the Main and Lateral Ranges of the Greater Caucasus, Kopetdag, etc. Synclinoria are expressed in the relief by compensated depressions - plains filled in the upper part with Pleistocene and modern deposits. Even larger uplifts, consisting of several anticlinoria and synclinoria, are called megaanticlinoria. They form megaforms of relief and have the appearance of a mountainous country, consisting of several ridges and depressions separating them. Megaanticlinoria include mountain structures of the Greater and Lesser Caucasus.
Folding occurs in geosynclinal regions. Folding is accompanied by faults and magmatism. These processes complicate the manifestation of folds in the relief. Under the influence of external factors on folded structures, a diverse structural-denudation relief arises.
Faults are tectonic discontinuities in rocks. They are often accompanied by the movement of broken blocks of geological bodies relative to each other. Among the breaks, the following are distinguished: cracks penetrating to a relatively shallow depth; deep faults - more or less wide zones of highly fragmented rocks and super-deep faults, which are rooted in the mantle. Faults and overthrusts often appear along the faults. In the relief, these structures are usually expressed as a ledge. By the height of the ledge, one can judge the magnitude of the vertical displacement of the blocks. With a system of faults and thrusts, a stepped relief is formed, which consists of steps - blocks displaced in one direction. If the blocks are displaced in different directions, then in the relief they appear in the form of blocky mountains. By the nature of the structure, table and folded blocky mountains stand out. Table blocky mountains are composed of undisturbed rock layers, for example, Table Jura in Africa. Folded blocky mountains are formed when folded structures rise along the breaks, for example, Altai, Tien Shan. Folded-blocky mountains consist of horst anticlines - ridges and graben-synclines - depressions (Main and Lateral ridges of the Greater Caucasus). Under conditions of stretching and subsidence of domes, graben anticlines are formed along normal faults. When blocks are uplifted along faults, horst-synclines are laid in the syncline. Blocky mountains are formed in the distribution areas of folded areas, disturbed by subsequent tectonic movements along faults. Examples of blocky mountains are the mountains of Transbaikalia, the Great Basin of North America, and horsts are the Harz, Black Forest and Vosges
Along the lines of recent ruptures, zones of modern accumulation develop - bands of clastic rocks, river valleys are born. This is facilitated by the fracturing of rocks along the zones of disturbances, the accumulation of groundwater. Erosion forms along the faults take their direction in plan. In river valleys, straight sections alternate with sharp bends under straight and sharp corners. Fault zones can define the lines of seas and oceans. For example, the Somali Peninsula, the Sinai Peninsula, the Red Sea. Exits are often observed along fault lines igneous rocks, hot and mineral springs, chains of volcanoes, esker and terminal moraine ridges, earthquakes. Faults also play an important role within the rift zones of continents and oceans. They are associated with the formation of the Baikal rift system, the East African system, and the crest of the Mid-Ocean Ridges.
A significant role in the formation of the relief of the earth's surface is vertical oscillatory movements - constant reversible tectonic movements of different scales, areal distribution, different velocities, amplitudes and signs that do not create folded structures. Such movements are called epeirogenic. They create the continents, manage the transgressions and regressions of the sea. Within kplatforms, their manifestation is associated with the formation of syneclises and anteclises, and in geosynclinal areas - uplifts and troughs, the relief of fold-block and table mountains, normal faults, overthrusts, horsts, folds and corresponding landforms. Vertical movements control the distribution of areas occupied by land and by the sea, determine the configuration of continents and oceans and the location of areas of predominance of denudation and accumulative relief.
Horizontal tectonic movements manifest themselves in the horizontal movement of the earth's plates, in the formation of folds, as well as gaps with a large horizontal component. According to the concept of global tectonics, they determine the horizontal movement of the continents and the formation of the oceans: the Atlantic, the Indian. The displacements of the blocks of the earth's crust relative to each other in the horizontal direction are called shifts. Shifts can reach an amplitude of more than a thousand kilometers, such as the Mendocino fault in the northeast Pacific Ocean. Shifts are revealed by the simultaneous shift of positive forms (hills, mountain ranges) and negative forms(river valleys) in one direction. Very large horizontal thrusts, in which the masses of the earth's crust move for tens and hundreds of kilometers, are called shariazhs. Giant caricatures are the Alps and the Carpathians. Their roots are located hundreds of kilometers to the south. Horizontal movements lead to the formation of horsts and grabens. An example of a giant young expanding graben-rift is the Red Sea depression. Relative to the axis of the rift, its sides are displaced in different directions by several millimeters per year. Another form of horizontal tectonic movement is the transform faults that cross the mid-ocean ridges. The amplitude of the horizontal displacement along them reaches several hundred kilometers.
Influence of the latest and modern tectonic movements on the relief. The latest tectonic movements are movements that manifested themselves in the Neogene - Quaternary time. Their role is enormous in the deformation of the day surface and the creation of positive, negative and relief forms of various orders and monoclines. So, for example, the southern part of the territory of Belarus at the end of the Paleogene time was occupied by the sea. Now this former sea level lies on 80 - 100 m and above sea level. Plains, low plateaus and plateaus correspond to areas with weakly pronounced positive tectonic movements in the relief: East European Plain, southern part West Siberian Plain, Ustyurt Plateau. Areas with weakly pronounced negative movements correspond to the basin of the Baltic Sea, the Caspian lowland, the Polotsk lowland with thick strata of Neogene-Quaternary deposits. The areas of intense positive tectonic movements correspond to the mountains of the Caucasus, Pamir, Tien Shan.
The latest tectonic movements control the location of areas with a predominance of denudation and accumulative relief. They influence the intensity of manifestation of exogenous processes and the expression of geological structures in the relief. Some neotectonic structures are directly expressed in the relief and a direct relief is formed. In place of other structures, an inverted relief is formed. Landforms that were formed as a result of endogenous processes and whose morphology reflects geological structures, academician I.P. Gerasimov called morphostructures. Passive tectonic structures, prepared by denudation, are called lithomorphostructures.
At present, the earth's crust everywhere is experiencing deformations of a different nature. Outgoing tectonic movements are experienced by the North Sea coast of Western Europe and the territory of the Netherlands, a third of which has sunk below sea level and is fenced off by dams. At the same time, Fennoscandia and northern North America are experiencing upward movements at a rate of up to 10 mm/year. Alpine folding areas are also experiencing modern uplift: the Alps, the Himalayas, and the Pamirs. The amplitude of the uplift of these mountains during the Neogene - Quaternary time was several kilometers.
The geomorphological signs of neotectonic movements are: the presence of sea and river terraces not associated with climate change; deformations of the longitudinal profile of river valleys and terraces; abnormally occurring coral reefs; flooded marine coastal, glacial and karst forms; antecedent river valleys resulting from the sawing of a tectonic rise by the river; morphological appearance of erosional forms, etc.
Depending on the speed of tectonic and denudation processes, the relief can develop in two ways: ascending and descending. According to the first method, the relief is formed if the tectonic uplift of the territory exceeds the intensity of denudation. In the case of an ascending development of the relief, its absolute and relative heights increase, deep erosion intensifies, river valleys take the form of gorges, gorges and canyons, and landslide-scree processes become more active. In river valleys, floodplains narrow or completely disappear, socle terraces and outcrops form on steep banks, and in riverbeds - rapids and ledges. In the mountains, geological structures acquire a clear reflection in the relief, an alpine relief appears, and strata of flysch clastic material accumulate in the foothills. The descending type of relief development is manifested if the rate of tectonic uplift of the territory is less than the denudation value. In this case, the absolute and relative relief marks decrease, the slopes decrease and flatten. River valleys are expanding, alluvium is accumulating in them. In the mountains, the relief-forming role of snow and ice ceases, the structure of the relief is obscured, the peaks and ridges of the ridges take on rounded outlines, and the size of flysch decreases. These signs are important for paleogeographic and paleotectonic reconstructions, determining the nature of tectonic movements and the location of demolition areas, establishing the age of manifestation of tectonic movements and the formation of denudation relief.
Modern tectonic movements are manifested in historical and present times. Their existence is evidenced by historical and archaeological materials, data of repeated leveling. Often they will inherit the nature of the development of neotectonic movements. It is important to take modern movements into account in engineering and geological surveys during the construction of canals, oil and gas pipelines, railways, nuclear power plant, etc.
LECTURE 5 MAGMATISM AND EARTHQUAKES AS FACTORS OF RELIEF FORMATION
It is located in the west of Russia from the borders with Ukraine and Belarus to the Urals. The plain is based on an ancient platform, so the relief of this natural area is generally flat. Great importance in the formation of such a relief had external destructive processes: the activity of wind, water, glacier. The average height of the Russian Plain ranges from 100 to 200 m above sea level. The foundation of the Russian platform lies at various depths and comes to the surface only on the Kola Peninsula and in Karelia. Here the Baltic Shield is formed, with which the origin of the Khibiny on the Kola Peninsula is connected. In the rest of the territory, the foundation is covered by a sedimentary cover of different thicknesses. The origin of the heights on the Russian Plain is explained by many reasons: the activity of the glacier, the deflection of the platform, the uplift of its foundation. The northern part of the plain was covered by an ancient glacier. The Russian Plain is almost entirely located within the temperate climate. Only the far north is in the subarctic climate. Continentality on the plain increases towards the east and especially towards the southeast. Precipitation is brought by westerly winds (all year round) from the Atlantic. Compared to others large plains our country she receives the largest number precipitation. In the zone of maximum moisture are the sources of large rivers of the Russian Plain: the Volga, the Northern Dvina. The northwest of the plain is one of the lake regions of Russia. Along with large lakes - Ladoga, Onega, Chudsky, Ilmensky - there are a lot of small lakes, mainly of glacial origin. In the south of the plain, where cyclones are rare, precipitation is less. In summer, there are often droughts and dry winds. All rivers of the Russian Plain are fed mainly by snow and rain and spring floods. The rivers of the north of the plain are more abundant than those of the south. play a significant role in their diet ground water. Southern rivers are shallow, the share of groundwater nutrition in them is sharply reduced. All rivers of the Russian Plain are rich in energy resources. The features of the relief and climate of the Russian Plain cause a clear change natural areas within its limits from northwest to southeast from tundra to deserts temperate zone. The most complete set of natural zones can be traced here in comparison with other natural regions of the country. The Russian Plain has been inhabited and mastered by man for a long time. 50% of the population of Russia lives here. 40% of hayfields and 12% of Russia's pastures are also located here. In the bowels of the plain there are iron deposits (KMA, deposits Kola Peninsula), hard coal(Pechora basin), brown coal(Podmoskovskiy basin), apatites of the Kola Peninsula, potash salts and rock salts, phosphates, oil (Volga-Ural basin). Timber is being harvested in the forests of the Russian Plain. Since forests have been cut down for more than one century, in many central and western regions The composition of the forest stand has changed significantly. Many secondary small-leaved forests appeared. The main areas of the most fertile soils - chernozems - are concentrated on the Russian Plain. They are almost completely open. They grow wheat, corn, sunflower, millet and other crops. The areas of arable lands are also large in forest zones. Rye and barley, potatoes and wheat, flax and oats are grown here.
Most of European territory Russia, as well as some neighboring countries, is located on the continental part of the earth's crust, which is called the East European Platform. The landform here is predominantly flat, although there are exceptions, which we will discuss below. This platform is one of the oldest geological formations on earth. Let's take a closer look at what the relief of the East European Platform is, what minerals lie in it, and also how the process of its formation took place.
Territorial location
First of all, let's find out exactly where this geological formation is located.
The East European ancient platform, or, as it is also called, the Russian platform, is located on the territory geographical areas Eastern and Northern Europe. It occupies most of the European part of Russia, as well as the territories of the following neighboring states: Ukraine, Belarus, Latvia, Lithuania, Estonia, Moldova, Finland, Sweden, partly Poland, Romania, Kazakhstan and Norway.
In the northwest, the East European ancient platform extends to the formations of the Caledonian folding in Norway, in the east it is limited by the Ural Mountains, in the north by the Arctic Ocean, and in the south by the Black and Caspian Seas, as well as the foothills of the Carpathians, Crimea and the Caucasus (Scythian plate).
The total area of the platform is about 5500 thousand square meters. km.
History of formation
The tectonic landforms of the East European Platform are among the oldest geological formations in the world. This is due to the fact that the platform arose in Precambrian times.
Before the formation of a single world territory, the Russian platform was separate continent- Baltic. After the collapse of Pangea, the platform became part of Laurasia, and after the separation of the latter, it became part of Eurasia, where it is still located.
Throughout this time, the formation was covered with sedimentary rocks, which thus formed the relief of the East European Platform.
Platform Composition
As with all ancient platforms, the East European one is based on a crystalline foundation. Over the course of millions of years, a layer of sedimentary rocks was created on top of it. However, in some places the foundation comes to the surface, forming crystalline shields.
There are two such shields on the specified territory (in the south - the Ukrainian shield, in the north-west - the Baltic shield), which is shown on tectonic map platforms.
the East European Plain
What surface does the East European platform have? The landform here is predominantly hilly and flat. It is characterized by an alternation of low elevations (200-300 m) and lowlands. At the same time, the average plain, which is called the East European, is 170 m.
The East European (or Russian) Plain is largest facility flat type in Europe and one of the largest in the world. Its area occupies most of the territory of the Russian platform and is about 4,000 thousand square meters. km. It extends from the Baltic Sea and Finland inclusive in the west to Ural mountains in the east for 2500 km, and from the seas of the Northern Arctic Ocean in the north (Barents and White) to the Black, Caspian and Azov seas in the south at 2700 km. At the same time, it is part of an even larger object, which is commonly called the Great European Plain, stretching from the Atlantic coast and the Pyrenees in France to the Ural Mountains. As stated above, average height The Russian plain is 170 meters, but its highest point reaches 479 meters above sea level. It is located in the Russian Federation on the Bugulma-Belebeevsky Upland, which is in the foothills of the Ural Mountains.
In addition, on the territory of the Ukrainian Shield, which is also located on the Russian Plain, there are uplifts, which are a form of outcropping of crystalline rocks of the base of the platform. These include, for example, the Azov Upland, the highest point of which (Belmak-Mogila) is 324 meters above sea level.
The basis of the Russian Plain is the East European platform, which is very ancient. This is the reason for the flat character of the area.
Other relief objects
But the Russian Plain is not the only geographical feature, which contains the East European platform. The landform here also takes on other forms. This is especially true at the boundaries of the platform.
For example, in the extreme northwest of the platform on the territory of Norway, Sweden and Finland, there is the Baltic Crystalline Shield. Here, in the south of Sweden, the Central Swedish Lowland is located. Its length from north to south and from west to east is 200 km and 500 km, respectively. The height above sea level here does not exceed 200 m.
But in the north of Sweden and Finland, the Norland plateau is located. Its maximum height is 800 meters above sea level.
A small section of Norway, which includes the East European platform, is also characterized by a hill. The relief here acquires a mountainous character. Yes, this is not surprising, since the hill gradually in the west turns into real mountains, called Scandinavian. But these mountains are already derivatives that are not directly related to the platform described in this review, which is shown on the tectonic map.
Rivers
Now let's take a look at the main reservoirs that are located on the territory of the platform we are studying. After all, they are also relief-forming factors.
The largest river of the East European Platform and Europe as a whole is the Volga. Its length is 3530 km, and the basin area is 1.36 million square meters. km. This river flows from north to south, while on the surrounding lands forming the corresponding floodplain landforms in Russia. The Volga flows into the Caspian Sea.
Another major river of the Russian platform is the Dnieper. Its length is 2287 km. It, like the Volga, flows from north to south, but, unlike its longer sister, it does not flow into the Caspian Sea, but into the Black Sea. The river flows through the territory of three states at once: Russia, Belarus and Ukraine. At the same time, about half of its length falls on Ukraine.
To other big and wide famous rivers The Russian platform should include the Don (1870 km), the Dniester (1352 km), the Southern Bug (806 km), the Neva (74 km), Seversky Donets(1053 km), tributaries of the Volga Oka (1499 km) and Kamu (2030 km).
In addition, in the southwestern part of the platform, the Danube River flows into the Black Sea. The length of this great river is 2960 km, but almost completely it flows beyond the boundaries of the platform we are studying, and only the mouth of the Danube is located on its territory.
lakes
There are on the territory of the Russian platform and the lake. The largest of them are located in Europe's largest freshwater lake Ladoga (area 17.9 thousand square kilometers) and Lake Onega (9.7 thousand square kilometers).
In addition, the Caspian Sea is located in the south of the Russian platform, which, in fact, is salt lake. This is the largest body of water in the world that does not have access to the oceans. Its area is 371.0 thousand square meters. km.
Minerals
Now let's study the minerals of the East European Platform. The bowels of this territory are very rich in gifts. So, in the east of Ukraine and the south-west of Russia there is one of the world's largest coal basins - Donbass.
The Krivoy Rog iron ore and Nikopol manganese basins are also located on the territory of Ukraine. These deposits are associated with the outcrop of the Ukrainian shield. Even larger reserves of iron are located on the territory of the Kursk magnetic anomaly in Russia. True, the shield did not come out there, but it got very close to the surface.
In the region of the Caspian basin, as well as in Tatarstan, there are quite large deposits of oil. They are also found on the territory of the southern oil and gas region in Ukraine.
Apatite mining on an industrial scale has been established on the territory of the Kola Peninsula.
Actually, these are the main minerals of the East European platform.
Soils of the Russian platform
Are the soils of the East European Platform fertile? Yes, this region has some of the most fertile soils in the world. Especially valuable types of soils are located in the south and in the center of Ukraine, as well as in the black earth region of Russia. They are called blacks. These are the most fertile soils in the world.
The fertility of forest soils, in particular gray ones, which are located north of the chernozems, is much lower.
General characteristics of the platform
The forms are quite varied. Among them special place occupy the plains. It is the East European platform that forms the largest flat complex in Europe. Only on its periphery can one find relatively high uplands. This is due to the antiquity of this platform, on which mountain-forming processes have not been going on for a long time, and weathering has smoothed out the hills that existed here millions of years ago.
Nature endowed the region with huge reserves of minerals. Particularly noteworthy are the deposits of coal and iron ore, in terms of which the Russian Platform is one of the world leaders. There are also reserves of oil and some other minerals.
This is the general description of the East European Platform, its relief, minerals stored in the bowels, as well as geographical features this locality. Of course, this is a fertile land that provides its inhabitants with everything necessary resources, which at correct use will be the key to prosperity.
