The superimposed landforms of the East European Plain are associated with the distribution of Quaternary cover 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 emerged in its main outlines. Rivers, as the most sensitive reagent, with the location of their valleys reflected the features of the structure and lithology of the eroded substrate. The greatest influence on the formation and location of the river network was exerted by the reflected relief. The main rivers gravitated toward syneclises. During the development of river valleys, the location of watersheds was determined by the structure of the substrate. The positive elements of the structure prepared by denudation 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, limiting 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. For 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 hill. The main watershed of the East European Plain passes mainly within the Moscow syneclise, along its northern side. The watershed elevation is asymmetrical. 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 is generally characterized by inversion relief. The main watershed of the East European Plain is of erosional origin.
The Black Sea-Caspian watershed is asymmetrical, shifted far to the east, running along the crest of the heavily eroded Volga Upland along the steep right bank of the Volga.
The erosive 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-gully relief. By the beginning of glaciation, the relief of the East European Platform was highly dissected and had a greater amplitude of elevation fluctuations compared to modern times. The Black Sea coastline was located about 100 m below the modern one. In accordance with this position of the erosion base, the rivers deepened their valleys.
Sea levels fluctuated periodically throughout the Pleistocene. At its maximum it rose up to 40 m above its modern position. The territory of the East European Plain between the coastline and the glaciation front was the arena of humidnonival (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 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 highly controversial. In particular, the issue of the relationship between the transgression of the sea of the Black Sea-Caspian basin and the phases of glaciation remains controversial. Taking the Black and Caspian seas as closed, while 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 people are of the opinion that sea levels rose during the interglacial period.
In the Quaternary period, on the territory of the East European Plain, water-glacial sediments 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 waves of cooling first affected the high mountain areas. A further decrease in the snow line caused the sliding of glaciers into the foothills and the development of long-term snow cover on the plain. In Mindelian times, the ice sheet may have captured the northwest of the platform; to the south, it was 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 Dnieper valley, the glacier spread below Kanev. A moraine of Mindelian age was exposed here during the excavation of the Kanevskaya hydroelectric power station pit. During 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. The ice sheet covered most of the platform, but the end-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 along the Dnieper valley extended to Zolotonosha, where a moraine covered with a layer of medium loess was discovered in the quarries of a brick factory.
In the late Pleistocene, glaciation occupied the northwestern part of the East European Plain. Its retreat is associated with the formation of terminal moraines of the stages of the Würm glaciation: Polesie, or Kalinin, Valdai, or Ostashkov, and Baltic.
The boundaries of the stages of the Würm 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 advance of ice were the Black Sea-Baltic and Main watersheds, the Valdai Upland, the ledge of the Silurian plateau in the Baltic states, etc. The most significant of the superimposed moraine ridges were: the Belarusian, Smolensk-Moscow, Baltic, Bezhanitsky mountains, etc.
Throughout the entire territory of the glacial zone, the superimposed relief of the East European Plain is characterized by glacial forms. Large areas are covered by bottom moraine, among the hilly formations of which glacial lakes are often included. In the north-west, drumlin and kame landscapes are common.
Glacial-exaration forms of relief 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, developed by the movement of ice of the Dnieper glaciation). The water-glacial accumulative formations of the periglacial zone, which make up the loess and sandy plains, have the same enormous geomorphological significance as the glacial forms. Loess superimposed plains occupy large areas in the middle Dnieper region, the Black Sea lowland, and 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 periglacial regions of the East European Plain.
The formation of loess plains is associated with many questions of the geology of the Quaternary period, 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 the soil horizons buried in it, the qualitative features of the loess itself and loess rocks. The latter definition is still not specific enough 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 the geographical shell to the sedimentary strata of the earth's crust. Therefore, the qualitative features of the cover loess rocks, while preserving the main features of the material composition of the geological body, fully reflect the features of the geographical conditions of their formation. Of the latter, the most important factors are topography and climate.
The 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 cover deposits developed on it. The principle of stratigraphic subdivision of cover layers according to the geomorphological method is based on the fact that higher relief levels have a more ancient cover of sediments. This is convincingly seen in the example of sea and river terraces, as well as foothill steps, where in each area the highest terrace is composed of more ancient strata.
Climate features are reflected in the sources of material that feed the provinces in the composition, transport, sorting of the skeletal part of loess rocks, the conditions of their deposition and stratification. It is believed that the deposition of loess rocks is associated with 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 sediments. 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 extra-glacial relief. There are two main points of view about the transport and deposition of loess rocks in the East European Plain and Western countries. According to the first, the formation of loess is associated with wind activity in the glacial desert; according to another, loess rocks are a product of the deposition of melted glacial waters, which overflowed into the periglacial plains during the warm season. The conditions for the deposition of loess rocks were similar to the conditions of the floodplains of modern rivers. The author has consistently defended this point of view since 1946. No traces of intense aeolian activity in the Pleistocene in Europe have been established. The fact that European loess is not of aeolian origin 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 hidden. The presence of layering, however, can be traced in horizontal shear surfaces that cut off the well-known columnar structure characteristic of loess rocks.
Sedimentary layering in the loess was transformed by weathering, which followed accumulation during the cold, dry season and frosty, longer periods. Sedimentation layering in loess is especially deformed by soil formation and is masked by bands relatively enriched in humus, the number of which increases with increasing thickness of the loess layer, regardless of its age. Thus, in the section of loess rocks of a buried ravine near the village. Vyazovka (Luben district), in the river basin. Sult, in a 56.45-meter thick layer of loess-like loams, 13 such strips with a total thickness of about 22 m are distinguished. Some parts of the section are colored by 2-3 m of humus. These deposits are distinguished as fossil soils. The formation of buried soil horizons and parts of a single loess layer filled with organic matter 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 is no data for this.
To use buried soils for stratigraphic comparisons of extraglacial deposits of different phases of glaciation and on different elements of the relief, it is necessary to proceed from the actually existing pattern of loess distribution and its stratification. In the latter, the enrichment of the loess strata with humus, as a geological body transitional from the geographical shell to the earth's crust, is inevitable. This is what gave L. S. Berg and V. A. Obruchev grounds to consider the loess cover as soil. Fossil soils that stand out against the general background of loess do not witness interruptions in the accumulation of loess, but serve as an indicator of sedimentation conditions similar to the conditions 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 well as in other loess areas, the cover deposits are more enriched in humus than on the plains, their number of interlayers is greater, and their thickness is increased. The presence of humus in cover deposits can be considered as a characteristic feature of alluvial, proluvial and deluvial sedimentation and can be explained by the fact that sedimentation of the loess strata was accompanied by simultaneous weathering and soil formation, depending primarily on the variability of the degree of moisture. In most cases, the origin of humus bands in loess is not based on direct soil formation, but on the sorption of humic substances from groundwater solutions by loess rocks. Humusification and, in general, changes in the color of loess rocks are 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. An exception is not the horizons of buried soils covering higher areas, including the terraces of loess areas, processed by excavators, which is typical for the steppe zone. The latter circumstance can be used to correlate loess sections of similar geomorphological formations of river and sea terraces in a given area. On the territory of the East European Plain, several age-related 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 glaciations and are located naturally: they are associated with maximum glaciation, occupy more southern and extensive territories, younger loess accumulations move northward following the retreating glaciation front and have a blanket occurrence in the parts adjacent to it. 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 more ancient accumulations.
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, Smolensk region, Moscow region - near Vladimir on Klyazma;
middle loess- Late Riess - Pripyat, or Moscow, glaciation, includes one, two or three horizons of buried soils, distributed in the upper reaches of the Oka, Don, Desna, on the northern slopes of the 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, subloess 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 Anthropocene, distributed in the southern part of the East European Plain, but occupy a much larger area than brown subloess loams: there are no anteclises on the elevated parts.
Of the soils enclosed in loess, only the soil on freshwater moraine loams and ancient euxinian marine sediments can be considered reliably Mindel-ris, Nikulin. The buried soil on the Dnieper moraine may correspond to the Odintsovo (Dnieper-Pripyat, Moscow) interstadial.
In addition to loess smoothed spaces, eluvial-deluvial deposits also play a significant role in the geomorphology of the East European Plain, covering the slopes of the hills with a thick cloak. They are often represented by loess-like rocks, highly enriched with humus, forming many layers of buried soils. Colluvial areas soften the topography of hills and ledges of terraces, creating smooth transitions from watershed ridges to low-lying loess spaces. The arches of the anteclises 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. Thick layers of sand are of glacial, alluvial, lacustrine and marine origin. Subsequently reworked by the wind, they created a monotonous lumpy relief. Significant outwash fields are associated with belts of terminal moraines of different phases of glaciation. Fluvioglacial sands occupy large areas in Polesie, especially in the Pripyat and Teterev basins.
In river valleys, fluvioglacial sands transform into alluvial deposits of the first floodplain terraces. Sandy terraces are well defined along most rivers of the East European Plain.
Sands occupy vast areas in coastal areas. In the Baltics, dune landscapes are well expressed in the Kaliningrad region, on the Riga coastline, Sarema Island, etc. In the Black Sea region, dune sands are common on the embankments of estuaries, occupying a large area in the lower reaches of the Dnieper and Danube. Lumpy sands cover significant areas 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. The sands are almost devoid of plant cover and are characterized by a variety of elementary forms common to arid climate zones.
The formation of sedimentary and sedimentary-volcanogenic cover on the East European Platform began in the Precambrian. A high degree of planation of the crystalline basement had already taken place before the Krivoy Rog time. In the Proterozoic, a sedimentary-volcanogenic cover formed in the southern part of the platform, from which the remnant Ovruch ridge was preserved.
In the tectorogeny 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 from Riphean to Neogene age on the platform. Studying them is the task of historical geomorphology. Only the main points are noted here.
In the late Paleozoic, during the process of the Hercynian orogeny, the main features of the structure and orography of the East European Platform and the adjacent territories emerged. The Donetsk and Timan ridges stood out, monoclinal ridges took shape in the north-west of the country, the hills 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 southwest. In the early Mesozoic, vigorous leveling of the surface of the East European Plain took place. The landscapes of the country were dominated by denudation forms of relief, their relics being 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 went through a long stage of marine sedimentation.
The marine environment, gradually shrinking and retreating to the south, existed from Jurassic to Pliocene times. The most important stages of the marine development of the sedimentary cover of the platform in the post-Cretaceous period were the existence of the Eocene - Kyiv, Miocene - Sarmatian and Pliocene - Pontian basins. As a result of the retreat of the Meso-Cenozoic basins, accumulative plains and geomorphological levels emerged on the East European Platform, which were giant steps descending towards the Black Sea region.
Following the shift of the coastline, large 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 tectorogeny 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 took final shape, and the features of the reflected relief emerged.
In the Pleistocene, the structural-denudation surface of the East European Plain became the substrate for the formation of superimposed relief and gradually acquired its modern appearance.
In areas where rocks of the crystalline foundation of platforms come to the surface, for example in Ukraine - in the middle reaches of the Dnieper near the city of Dnepropetrovsk and Krivoy Rog, it is clear that these rocks are folded, broken by cracks and have the same structures as in the mountains. From this it was concluded that once upon a time, in the first stages of the formation of platforms, mountains existed in the place of modern plains. Then came long periods of quiet tectonic life, during which the mountains were almost completely destroyed by external forces of denudation. Mountain ranges and peaks were lowered and leveled. An almost plain was formed, which the American geologist and geographer William Davis, one of the founders of the science of geomorphology, proposed to call peneplain (“pene” - almost, “plain” - plain). The primary ancient peneplains gradually sank and were covered by the waters of the Paleozoic and Mesozoic seas. Sediment layers accumulated at the bottom of the seas. After the departure of the sea and the gentle general uplift of the platform, these sedimentary rocks formed a platform cover.
Simultaneously with the general weak tectonic uplifts and subsidences of the entire platform, its individual sections experienced local (local) movements up or down. It was these movements that formed the gentle uplifts and depressions in the surface of the foundation and in the modern topography - those hills and flat depressions that we have already talked about.
Local movements on the platforms continue today. Accurate measurements have shown that, for example, the Kursk region rises by 3.6 mm per year, and Krivoy Rog by 10 mm per year. The seeming inviolability and immobility of the surface of our planet is illusory. In fact, movements of different directions and different strengths, caused by not yet fully understood processes occurring in the bowels of the Earth, occur continuously throughout the entire history of the planet.
On the plains. where natural grassy vegetation is destroyed, under the influence of heavy rains or during rapid snow melting, jets of water collecting on the slopes erode them and form deep, rapidly growing ravines.
The surface exposed from under the waters of the departed sea is affected by exogenous forces - river erosion and accumulation, wind, gravitational shedding, collapse and sliding of collapsing rocks, and their dissolution by groundwater. As a result of the interaction of tectonic movements and exogenous processes, the hilly or flat, undulating or basin relief of the plains was formed. And the stronger the tectonic movements, the more strongly they are affected by exogenous processes. However, these processes depend not only on tectonic movements. Different parts of the earth's surface receive different amounts of solar heat. Some areas receive a lot of precipitation in the form of rain and snow, while others suffer from drought. Differences in climate also determine differences in the operation of exogenous processes.
In humid countries, the main work is done by water. After rains or snow melting, it is partially absorbed into the soil covered with forests and meadows, and partially flows down the slopes. Both soil and surface water collect in streams, which connect into small rivers and then into large water streams. Rivers flow, eroding their beds, washing away the banks, causing them to collapse and slide. A network of large and small river valleys appears. Valley relief is a distinctive feature of geomorphological landscapes in humid areas.
Where ravines are located close to each other, an impassable mixture of sharp and narrow ridges and “small gorges” is formed. This type of terrain is called badland or bad lands.
In forest-steppe and steppe areas there is less precipitation, and it falls very unevenly throughout the year. Rivers and valleys here no longer dissect the surface so densely. But where the natural grassy vegetation is destroyed, during rare but heavy rainfalls or during the spring rapid melting of snow, streams of water collecting on the slopes cut them and form deep, rapidly growing ravines.
In arid areas of semi-deserts and deserts, rain falls very rarely. The vegetation here is sparse and does not cover the soil with a protective carpet. The main acting force is the wind. It reigns in deserts everywhere, even in rare river beds that are dry most of the year.
The wind blows dust and grains of sand out of the soil. Black storms carry dust for many hundreds of kilometers. Falling to the ground when the wind subsides, this dust can form powerful layers of dusty deposits - the so-called loess.
Sand, carried by the wind in the air or rolled over a bare surface, accumulates in deserts, piling up moving dunes, dune chains and ridges. The pattern of the aeolian relief of sands, especially clearly visible on aerial photographs, is determined by the regime and strength of the winds and the obstacles encountered along their path - mountain ranges and ridges.
The climate of any region of the Earth did not remain the same. The causes of climate change on our planet are complex and not yet fully understood. Scientists associate these changes with cosmic phenomena, with changes in the position of the Earth's axis and migrations of the poles, with vertical and horizontal displacements of continents.
Lake Elk. Karelia. Such lakes are located in depressions of the moraine-glacial relief.
The Earth has experienced strong climate fluctuations in recent geological times, especially during the Quaternary period (Anthropocene). During this period, large glaciations arose in the polar regions of the globe. In Eurasia, glaciers gradually descended from the mountains of northern Scandinavia, the Urals, and Central Siberia. They connected with each other and formed vast ice sheets. In Europe, during the maximum glaciation (200-300 thousand years ago), the edge of the ice sheet, several hundred meters high, reached the northern foothills of the Alps and Carpathians, descended in tongues along the valleys of the Dnieper to Dnepropetrovsk and the Don to Kalach.
The ice in the ice sheet slowly spread from the center to the edges. On the elevations of the subglacial relief, glaciers tore off and smoothed rocks, turning out large boulders and blocks of rock. And now, especially in areas close to the centers of previous glaciations - in Scandinavia, on the Kola Peninsula, in Karelia, smoothed and scratched, and sometimes polished to a shine, granite rocks, the so-called sheep's foreheads, are perfectly preserved. By the location of scratches and marks on these rocks and glacial boulders, scientists determine the direction of movement of ancient, long-vanished glaciers.
Spotted tundra. It is flat, dry, clayey tundra with clay patches the size of a plate or wheel, usually completely devoid of vegetation. The patches are interspersed with dry, vegetated tundra or bordered by a border of plants.
Stones were frozen into the ice, and it carried them hundreds and thousands of kilometers, piling them up along the edges of the ice sheets in the form of ridges and hilly moraines. Streams of unfrozen water flowed in the cracks on the glaciers, inside and under them, saturated with sand, pebbles and gravel. Some cracks were completely clogged with sediment. And when the glaciers began to melt and retreat, sand and gravel masses were projected from cracks onto the surface freed from under the ice. Winding ridges formed. Such sand ridges up to 30-40 km long and from several meters to 2-3 km wide are often found in the Baltic states, near Leningrad, Karelia, and Finland. They are called azami (ridge in Swedish). Eskers, moraine ridges and hills, as well as kamas - rounded sandy mounds and drumlins - hills of a characteristic elongated shape - are typical witnesses to the relief-forming work of ancient cover glaciations that covered vast territories.
Residual glacial moraine, composed of loose loams with an accumulation of rock fragments.
Glaciers advanced and retreated several times in the northern regions of Europe, Asia, and North America. During these great Quaternary glaciations, air temperatures throughout the Earth decreased, especially strongly in the polar and temperate latitudes. In the vast areas of Europe, Siberia and North America, where glaciers did not penetrate, the soil froze to a depth of several hundred meters. Permafrost soils were formed, which remain to this day in Western and Eastern Siberia, the Far East, Canada, etc. In summer, the surface of the frozen ground thaws, the soil overflows with water, and many small lakes and swamps form. In winter, all this water freezes again. When freezing, as you know, water expands. Ice contained in soils breaks them apart with cracks. The network of these cracks often has a regular lattice (polygonal) pattern. The surface bulges and lumps form. Trees in such areas lean in different directions. When soil ice and permafrost melt, basins and depressions are formed - thermokarst relief. Permafrost heaving and thawing subsidence destroy buildings, roads, airfields, and people developing polar frozen regions have to devote a lot of effort to combat these harmful natural phenomena.
Relief of the East European PlainAlmost the entire length is dominated by gently sloping terrain. The East European Plain almost completely coincides with the East European Platform. This circumstance explains its flat terrain, as well as the absence or insignificance of manifestations of such natural phenomena as earthquakes and volcanism. Large hills and lowlands arose as a result of tectonic movements, including along faults. The height of some hills and plateaus reaches 600-1000 meters.
On the territory of the Russian Plain, platform deposits lie almost horizontally, but their thickness in some places exceeds 20 km. Where the folded foundation protrudes to the surface, hills and ridges are formed (for example, the Donetsk and Timan ridges). On average, the height of the Russian Plain is about 170 meters above sea level. The lowest areas are on the Caspian coast (its level is approximately 26 meters below the level of the World Ocean).
Relief of the West Siberian PlainThe differentiated subsidence of the West Siberian Plate in the Mesozoic and Cenozoic led to the predominance within its boundaries of processes of accumulation of loose sediments, the thick cover of which levels out the surface irregularities of the Hercynian basement. Therefore, the modern West Siberian Plain has a generally flat surface. However, it cannot be considered as a monotonous lowland, as was recently believed. In general, the territory of Western Siberia has a concave shape. Its lowest areas (50-100 m) are located mainly in the central (Kondinskaya and Sredneobskaya lowlands) and northern (Lower Obskaya, Nadymskaya and Purskaya lowlands) parts of the country. Along the western, southern and eastern outskirts stretch low (up to 200-250 m) hills: North Sosvinskaya, Turinskaya, Ishimskaya, Priobskoye and Chulym-Yenisei plateaus, Ketsko-Tymskaya, Verkhnetazovskaya, Nizhneeniseiskaya. A clearly defined strip of hills is formed in the inner part of the plain by the Siberian Uvals (average height - 140-150 m), stretching from the west from the Ob to the east to the Yenisei, and the Vasyugan Plain parallel to them.
Some orographic elements of the West Siberian Plain correspond to geological structures: gentle anticlinal uplifts correspond, for example, to the Verkhnetazovskaya and Lyulimvor hills, and the Barabinskaya and Kondinskaya lowlands are confined to syneclises of the base of the plate. However, in Western Siberia, discordant (inversion) morphostructures are also common. These include, for example, the Vasyugan Plain, which formed on the site of a gently sloping syneclise, and the Chulym-Yenisei Plateau, located in the zone of basement deflection.
The West Siberian Plain is usually divided into four large geomorphological regions: 1) marine accumulative plains in the north; 2) glacial and water-glacial plains; 3) periglacial, mainly lacustrine-alluvial plains; 4) southern non-glacial plains (Voskresensky, 1962).
The differences in the relief of these areas are explained by the history of their formation in Quaternary times, the nature and intensity of recent tectonic movements, and zonal differences in modern exogenous processes. In the tundra zone, relief forms are especially widely represented, the formation of which is associated with the harsh climate and widespread permafrost. Thermokarst depressions, bulgunnyakhs, spotted and polygonal tundras are very common, and solifluction processes are developed. Typical of the southern steppe provinces are numerous closed basins of suffusion origin, occupied by salt marshes and lakes; The network of river valleys here is sparse, and erosional landforms in the interfluves are rare.
The main elements of the relief of the West Siberian Plain are wide, flat interfluves and river valleys. Due to the fact that the interfluve spaces account for most of the country's area, they determine the general appearance of the plain's topography. In many places, the slopes of their surfaces are insignificant, the flow of precipitation, especially in the forest-swamp zone, is very difficult and the interfluves are heavily swamped. Large areas are occupied by swamps north of the Siberian Railway line, on the interfluves of the Ob and Irtysh, in the Vasyugan region and the Barabinsk forest-steppe. However, in some places the relief of the interfluves takes on the character of a wavy or hilly plain. Such areas are especially typical of some northern provinces of the plain, which were subject to Quaternary glaciations, which left here piles of stadial and bottom moraines. In the south - in Baraba, on the Ishim and Kulunda plains - the surface is often complicated by numerous low ridges stretching from northeast to southwest.
Another important element of the country's topography is river valleys. All of them were formed under conditions of slight surface slopes and slow and calm river flows. Due to differences in the intensity and nature of erosion, the appearance of the river valleys of Western Siberia is very diverse. There are also well-developed deep ones (up to 50-80 m) valleys of large rivers - the Ob, Irtysh and Yenisei - with a steep right bank and a system of low terraces on the left bank. In some places their width is several tens of kilometers, and the Ob valley in the lower reaches reaches even 100-120 km. The valleys of most small rivers are often just deep ditches with poorly defined slopes; During spring floods, water completely fills them and even floods neighboring valley areas.
The Russian Plain is one of the largest plains in the world by area. Among all the plains of our Motherland, only it opens to two oceans. Russia is located in the central and eastern parts of the plain. It extends from the coast of the Baltic Sea to the Ural Mountains, from the Barents and White Seas to the Azov and Caspian Seas.
The Russian Plain consists of hills with heights of 200-300 m above sea level and lowlands along which large rivers flow. The average height of the plain is 170 m, and the highest - 479 m - is on the Bugulma-Belebeevskaya Upland in the Ural part. The maximum elevation of the Timan Ridge is somewhat lower (471 m).
To the north of this strip, low plains predominate. Large rivers flow through this territory - Onega, Northern Dvina, Pechora with numerous high-water tributaries. The southern part of the Russian Plain is occupied by lowlands, of which only the Caspian is located on Russian territory.
The Russian Plain almost completely coincides with the East European Platform. This circumstance explains its flat terrain, as well as the absence or insignificance of manifestations of such natural phenomena as earthquakes and volcanism. Large hills and lowlands arose as a result of tectonic movements, including along faults. The height of some hills and plateaus reaches 600-1000 meters.
On the territory of the Russian Plain, platform deposits lie almost horizontally, but their thickness in some places exceeds 20 km. Where the folded foundation protrudes to the surface, hills and ridges are formed (for example, the Donetsk and Timan ridges). On average, the height of the Russian Plain is about 170 meters above sea level. The lowest areas are on the Caspian coast (its level is approximately 26 meters below the level of the World Ocean).
The formation of the relief of the Russian Plain is determined by its belonging to the Russian Platform plate and is characterized by a calm regime and low amplitude of recent tectonic movements. Erosion-denudation processes, Pleistocene glaciations and marine transgressions created the main relief features in the Late Cenozoic. The Russian Plain is divided into three provinces.
The North Russian province is distinguished by the widespread distribution of glacial and water-glacial landforms formed by the glacial covers of the Moscow and Valdai times. Stratified lowlands with remnant stratal monoclinal and ridge uplands predominate, with the orientation of relief forms in the northwestern and northeastern directions, emphasized by the pattern of the hydraulic network.
The Central Russian province is characterized by a natural combination of erosion-denudation layered and monoclinal-bedded uplands and lowlands, oriented in the meridional and sublatitudinal directions. Part of its vast territory was covered by the Dnieper and Moscow glaciers. Low-lying areas served as areas for the accumulation of aquatic and lacustrine-glacial sediments, and the relief of woodland, sometimes with significant aeolian reworking, with dune formations was formed on them. On elevated areas and sides of valleys, gullies and ravines are widely developed. Under the cover of loose sediments of Quaternary age, relics of the Neogene denudation-accumulative relief have been preserved. Leveled surfaces are preserved on the stratified hills, and in the east and southeast of the province there are marine deposits of ancient transgressions of the Caspian Sea.
The South Russian province includes the Stavropol strata-monoclinal flat-topped upland (up to 830 m), a group of island mountains (Neogene subextrusive bodies, the city of Beshtau - 1401 m, etc.) in the upper reaches of the Kuma River, delta plains of the Terek and Sulak rivers of the Caspian lowland, a terraced alluvial plain in lower reaches of the river Kuban. The relief of the Russian Plain has been significantly changed as a result of human economic activity.
Report: External processes shaping the relief and
Lesson topic: External processes that shape the relief and
associated natural phenomena
Lesson objectives: to develop knowledge about changes in landforms as a result of erosion,
weathering and other external relief-forming processes, their role
in shaping the appearance of the surface of our country.
Let students down
to the conclusion about the constant change and development of the relief under the influence of
only internal and external processes, but also human activities.
1. Repetition of the studied material.
What causes the Earth's surface to change?
2. What processes are called endogenous?
2.Which parts of the country experienced the most intense uplifts in the Neogene-Quaternary times?
3. Do they coincide with the areas where earthquakes occur?
Name the main active volcanoes in the country.
5. In which parts of the Krasnodar Territory are internal processes more likely to occur?
2. Studying new material.
The activity of any external factor consists of the process of destruction and demolition of rocks (denudation) and deposition of materials in depressions (accumulation).
This is preceded by weathering. There are two main types of deposition: physical and chemical, which results in the formation of loose deposits that are convenient for movement by water, ice, wind, etc.
As the teacher explains new material, the table is filled out
^ External processes
main types
Areas of distribution
The activity of an ancient glacier
^ Trogs, sheep's foreheads, curly rocks.
Moraine hills and ridges.
Introglacial plains
Karelia, Kola Peninsula
Valdai elevation, Smolensk-Moscow elevation.
^ Meshcherskaya lowland.
Activity of flowing waters
Erosion forms: ravines, gullies, river valleys
Central Russian, Privolzhskaya, etc.
almost everywhere
Eastern Transcaucasia, Baikal region, Wed.
^ Wind work
Aeolian forms: dunes,
deserts and semi-deserts of the Caspian lowland.
southern coast of the Baltic Sea
^ Groundwater
Karst (caves, mines, sinkholes, etc.)
Caucasus, Central Russian region, etc.
Tidal bore
abrasive
sea and lake coasts
^ Processes caused by gravity
landslides and screes
They predominate in the mountains, often on steep slopes of river valleys and ravines.
Middle reaches of the Volga River, Black Sea coast
^ Human activity
plowing of land, mining, construction, deforestation
in places of human habitation and extraction of natural resources.
Examples of certain types of external processes - pp. 44-45 Ermoshkina “Lessons of Geography”
INSTALLING NEW MATERIAL
1. Name the main types of exogenous processes.
2. Which of them are most developed in the Krasnodar region?
3. What anti-erosion measures do you know?
4. HOME TASK: prepare for a general lesson on the topic “Geological structure,
relief and mineral resources of Russia” pp. 19-44.
Relief of the East European (Russian) Plain
The East European (Russian) Plain is one of the largest plains in the world by area. Among all the plains of our Motherland, only it opens to two oceans. Russia is located in the central and eastern parts of the plain. It extends from the coast of the Baltic Sea to the Ural Mountains, from the Barents and White Seas to the Azov and Caspian Seas.
The East European Plain has the highest density of rural population, large cities and many small towns and urban-type settlements, and a variety of natural resources.
The plain has long been developed by man.
The justification for its determination to the rank of a physical-geographical country is the following features: 1) an elevated strata plain formed on the plate of the ancient East European Platform; 2) Atlantic-continental, predominantly moderate and insufficiently humid climate, formed largely under the influence of the Atlantic and Arctic oceans; 3) clearly defined natural zones, the structure of which was greatly influenced by the flat terrain and neighboring territories - Central Europe, Northern and Central Asia.
This led to the interpenetration of European and Asian species of plants and animals, as well as to a deviation from the latitudinal position of natural zones in the east to the north.
Relief and geological structure
The East European Elevated Plain consists of hills with heights of 200-300 m above sea level and lowlands along which large rivers flow.
The average height of the plain is 170 m, and the highest - 479 m - is on the Bugulminsko-Belebeevskaya Upland in the Ural part. The maximum elevation of the Timan Ridge is somewhat lower (471 m).
According to the characteristics of the orographic pattern within the East European Plain, three stripes are clearly distinguished: central, northern and southern. A strip of alternating large uplands and lowlands passes through the central part of the plain: the Central Russian, Volga, Bugulminsko-Belebeevskaya uplands and General Syrt are separated by the Oka-Don lowland and the Low Trans-Volga region, along which the Don and Volga rivers flow, carrying their waters to the south.
To the north of this strip, low plains predominate, on the surface of which smaller hills are scattered here and there in garlands and individually.
From west to east-northeast, the Smolensk-Moscow, Valdai Uplands and Northern Uvals stretch here, replacing each other. They mainly serve as watersheds between the Arctic, Atlantic and internal (drainless Aral-Caspian) basins. From the Northern Uvals the territory descends to the White and Barents Seas. This part of the Russian Plain A.A.
Borzov called it northern slope. Large rivers flow along it - Onega, Northern Dvina, Pechora with numerous high-water tributaries.
The southern part of the East European Plain is occupied by lowlands, of which only the Caspian is located on Russian territory.
Figure 1 – Geological profiles across the Russian Plain
The East European Plain has a typical platform topography, which is predetermined by the tectonic features of the platform: the heterogeneity of its structure (the presence of deep faults, ring structures, aulacogens, anteclises, syneclises and other smaller structures) with the unequal manifestation of recent tectonic movements.
Almost all large hills and lowlands of the plain are of tectonic origin, with a significant part inherited from the structure of the crystalline basement.
In the process of a long and complex development path, they formed as a single territory in morphostructural, orographic and genetic terms.
At the base of the East European Plain lie the Russian plate with a Precambrian crystalline foundation and in the south the northern edge of the Scythian plate with a Paleozoic folded foundation.
The boundary between the plates is not expressed in the relief. On the uneven surface of the Precambrian foundation of the Russian plate there are strata of Precambrian (Vendian, in places Riphean) and Phanerozoic sedimentary rocks with weakly disturbed occurrence. Their thickness is not the same and is due to the unevenness of the foundation topography (Fig. 1), which determines the main geostructures of the plate. These include syneclises - areas of deep foundation (Moscow, Pechora, Caspian, Glazov), anteclises - areas of shallow foundation (Voronezh, Volga-Ural), aulacogens - deep tectonic ditches, in the place of which syneclises subsequently arose (Kresttsovsky, Soligalichsky, Moskovsky, etc.), protrusions of the Baikal foundation - Timan.
The Moscow syneclise is one of the oldest and most complex internal structures of the Russian plate with a deep crystalline foundation.
It is based on the Central Russian and Moscow aulacogens, filled with thick Riphean strata, above which lies the sedimentary cover of the Vendian and Phanerozoic (from Cambrian to Cretaceous). In the Neogene-Quaternary time, it experienced uneven uplifts and is expressed in relief by fairly large elevations - Valdai, Smolensk-Moscow and lowlands - Upper Volga, North Dvina.
The Pechora syneclise is located wedge-shaped in the northeast of the Russian Plate, between the Timan Ridge and the Urals.
Its uneven block foundation is lowered to varying depths - up to 5000-6000 m in the east. The syneclise is filled with a thick layer of Paleozoic rocks, overlain by Meso-Cenozoic sediments. In its northeastern part there is the Usinsky (Bolshezemelsky) arch.
In the center of the Russian plate there are two large anteclises - the Voronezh and Volga-Urals, separated by the Pachelma aulacogen. The Voronezh anteclise gently descends to the north into the Moscow syneclise.
The surface of its basement is covered with thin sediments of the Ordovician, Devonian and Carboniferous. Carboniferous, Cretaceous and Paleogene rocks occur on the southern steep slope.
The Volga-Ural anteclise consists of large uplifts (vaults) and depressions (aulacogens), on the slopes of which flexures are located.
The thickness of the sedimentary cover here is at least 800 m within the highest arches (Tokmovsky).
The Caspian marginal syneclise is a vast area of deep (up to 18-20 km) subsidence of the crystalline basement and belongs to the structures of ancient origin; the syneclise is limited on almost all sides by flexures and faults and has angular outlines.
From the west it is framed by the Ergeninskaya and Volgograd flexures, from the north by the flexures of General Syrt. In places they are complicated by young faults.
In Neogene-Quaternary time, further subsidence (up to 500 m) and accumulation of a thick layer of marine and continental sediments occurred. These processes are combined with fluctuations in the level of the Caspian Sea.
The southern part of the East European Plain is located on the Scythian epi-Hercynian plate, lying between the southern edge of the Russian plate and the alpine folded structures of the Caucasus.
Tectonic movements of the Urals and the Caucasus led to some disruption of the occurrence of sedimentary deposits of plates.
This is expressed in the form of dome-shaped uplifts, significant swells (Oka-Tsniksky, Zhigulevsky, Vyatsky, etc.), individual flexural bends of layers, salt domes, which are clearly visible in the modern relief. Ancient and young deep faults, as well as ring structures, determined the block structure of plates, the direction of river valleys and the activity of neotectonic movements. The predominant direction of the faults is northwestern.
A brief description of the tectonics of the East European Plain and a comparison of the tectonic map with the hypsometric and neotectonic ones allows us to conclude that the modern relief, which has undergone a long and complex history, is in most cases inherited and dependent on the nature of the ancient structure and manifestations of neotectonic movements.
Neotectonic movements on the East European Plain manifested themselves with different intensity and direction: in most of the territory they are expressed by weak and moderate uplifts, weak mobility, and the Caspian and Pechora lowlands experience weak subsidence.
The development of the morphostructure of the northwestern plain is associated with the movements of the marginal part of the Baltic shield and the Moscow syneclise, therefore monoclinal (sloping) strata plains are developed here, expressed in orography in the form of hills (Valdai, Smolensk-Moscow, Belorussian, Northern Uvaly, etc.), and strata plains occupying a lower position (Verkhnevolzhskaya, Meshcherskaya).
The central part of the Russian Plain was influenced by intense uplifts of the Voronezh and Volga-Ural anteclises, as well as subsidence of neighboring aulacogens and troughs.
These processes contributed to the formation of layered, stepwise uplands (Central Russian and Volga) and the layered Oka-Don plain. The eastern part developed in connection with the movements of the Urals and the edge of the Russian plate, so a mosaic of morphostructures is observed here. In the north and south, accumulative lowlands of the marginal syneclises of the plate (Pechora and Caspian) are developed. Between them alternate stratified-tiered uplands (Bugulminsko-Belebeevskaya, Obshchiy Syrt), monoclinal-stratified uplands (Verkhnekamskaya) and the intraplatform folded Timan Ridge.
During the Quaternary, climate cooling in the northern hemisphere contributed to the spread of glaciation.
Glaciers had a significant impact on the formation of relief, Quaternary deposits, permafrost, as well as on changes in natural zones - their position, floristic composition, wildlife and the migration of plants and animals within the East European Plain.
There are three glaciations on the East European Plain: Oka, Dnieper with the Moscow stage and Valdai.
Glaciers and fluvioglacial waters created two types of plains - moraine and outwash. In the wide periglacial (pre-glacial) zone, permafrost processes dominated for a long time.
Snowfields had a particularly intense impact on the relief during the period of reduced glaciation.
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Compile a description of the relief and mineral resources of the Russian Plain according to the following plan: 1.
Make a description of the relief and mineral resources of the Russian Plain according to the following plan:
1. Where is the territory located?
2.
What tectonic structure is it associated with?
3. How old are the rocks that make up the territory and how are they deposited?
4. How did this affect the terrain?
5. How altitudes change across the territory
6. Where are the minimum and maximum heights and what are they?
7. What determines the current high altitude position of the territory
8. What external processes participated in the formation of the relief
9. What forms are created by each process and where they are placed, why
10.
What minerals and why are common on the plain, how are they located
1. Geographical location.
2. Geological structure and relief.
3. Climate.
4. Inland waters.
5. Soils, flora and fauna.
6. Natural areas and their anthropogenic changes.
Geographical position
The East European Plain is one of the largest plains in the world. The plain opens to the waters of two oceans and stretches from the Baltic Sea to the Ural Mountains and from the Barents and White Seas to the Azov, Black and Caspian Seas.
The plain lies on the ancient East European platform, its climate is predominantly temperate continental and natural zoning is clearly expressed on the plain.
Geological structure and relief
The East European Plain has a typical platform topography, which is predetermined by platform tectonics.
At its base lies the Russian plate with a Precambrian foundation and in the south the northern edge of the Scythian plate with a Paleozoic foundation. At the same time, the boundary between the plates is not expressed in the relief. On the uneven surface of the Precambrian basement lie strata of Phanerozoic sedimentary rocks. Their power is not the same and is due to the unevenness of the foundation. These include syneclises (areas of deep foundation) - Moscow, Pechersk, Caspian and anticlises (protrusions of the foundation) - Voronezh, Volga-Ural, as well as aulacogens (deep tectonic ditches, in place of which syneclises arose) and the Baikal ledge - Timan.
In general, the plain consists of hills with heights of 200-300m and lowlands. The average height of the Russian Plain is 170 m, and the highest, almost 480 m, is on the Bugulma-Belebeevskaya Upland in the Ural part. In the north of the plain there are the Northern Uvals, the Valdai and Smolensk-Moscow stratal uplands, and the Timan Ridge (Baikal folding).
In the center are the elevations: Central Russian, Privolzhskaya (stratal-tiered, stepped), Bugulminsko-Belebeevskaya, General Syrt and lowlands: Oksko-Donskaya and Zavolzhskaya (stratal).
In the south lies the accumulative Caspian Lowland. The formation of the plain's topography was also influenced by glaciation. There are three glaciations: Oka, Dnieper with the Moscow stage, Valdai. Glaciers and fluvioglacial waters created moraine landforms and outwash plains.
In the periglacial (pre-glacial) zone, cryogenic forms were formed (due to permafrost processes). The southern border of the maximum Dnieper glaciation crossed the Central Russian Upland in the Tula region, then descended along the Don valley to the mouth of the Khopra and Medveditsa rivers, crossed the Volga Upland, the Volga near the mouth of the Sura, then the upper reaches of the Vyatka and Kama and the Ural in the region of 60°N. Iron ore deposits (IOR) are concentrated in the foundation of the platform. The sedimentary cover is associated with reserves of coal (eastern part of Donbass, Pechersk and Moscow region basins), oil and gas (Ural-Volga and Timan-Pechersk basins), oil shale (northwestern and Middle Volga region), building materials (widespread), bauxite (Kola Peninsula), phosphorite (in a number of areas), salts (Caspian region).
Climate
The climate of the plain is influenced by its geographical location, the Atlantic and Arctic oceans.
Solar radiation varies dramatically with the seasons. In winter, more than 60% of radiation is reflected by snow cover. The western transport dominates over the Russian Plain all year. Atlantic air transforms as it moves east. During the cold period, many cyclones come from the Atlantic to the plain. In winter, they bring not only precipitation, but also warming. Mediterranean cyclones are especially warm when the temperature rises to +5˚ +7˚C. After cyclones from the North Atlantic, cold Arctic air penetrates into their rear part, causing sharp cold snaps all the way to the south.
Anticyclones provide frosty, clear weather in winter. During the warm period, cyclones mix to the north; the northwest of the plain is especially susceptible to their influence. Cyclones bring rain and coolness in the summer.
Hot and dry air forms in the cores of the spur of the Azores High, which often leads to droughts in the southeast of the plain. January isotherms in the northern half of the Russian Plain run submeridianally from -4˚C in the Kaliningrad region to -20˚C in the northeast of the plain. In the southern part, the isotherms deviate to the southeast, amounting to -5˚C in the lower reaches of the Volga.
In summer, isotherms run sublatitudinally: +8˚C in the north, +20˚C along the Voronezh-Cheboksary line and +24˚C in the south of the Caspian region. The distribution of precipitation depends on westerly transport and cyclonic activity. There are especially many of them moving in the zone 55˚-60˚N, this is the most humidified part of the Russian Plain (Valdai and Smolensk-Moscow Uplands): the annual precipitation here is from 800 mm in the west to 600 mm in the east.
Moreover, on the western slopes of the hills it falls 100-200 mm more than on the lowlands lying behind them. Maximum precipitation occurs in July (in the south in June).
In winter, snow cover forms. In the northeast of the plain, its height reaches 60-70 cm and it lies for up to 220 days a year (more than 7 months). In the south, the height of the snow cover is 10-20 cm, and the duration of occurrence is up to 2 months. The humidification coefficient varies from 0.3 in the Caspian lowland to 1.4 in the Pechersk lowland. In the north, the moisture is excessive, in the upper reaches of the Dniester, Don and Kama rivers it is sufficient and k≈1, in the south the moisture is insufficient.
In the north of the plain the climate is subarctic (the coast of the Arctic Ocean); in the rest of the territory the climate is temperate with varying degrees of continentality. At the same time, continentality increases towards the southeast
Inland waters
Surface waters are closely related to climate, topography, and geology. The direction of rivers (river flow) is predetermined by orography and geostructures. The flow from the Russian Plain occurs into the basins of the Arctic and Atlantic oceans and into the Caspian basin.
The main watershed passes through the Northern Uvals, Valdai, Central Russian and Volga Uplands. The largest is the Volga River (it is the largest in Europe), its length is more than 3530 km, and its basin area is 1360 thousand sq. km. The source lies on the Valdai Hills.
After the confluence of the Selizharovka River (from Lake Seliger), the valley widens noticeably. From the mouth of the Oka to Volgograd, the Volga flows with sharply asymmetrical slopes.
In the Caspian lowland, the Akhtuba branches are separated from the Volga and a wide strip of floodplain is formed. The Volga Delta begins 170 km from the Caspian coast. The main supply of the Volga is snow, so high water is observed from the beginning of April to the end of May. The height of the water rise is 5-10 m. 9 nature reserves have been created on the territory of the Volga basin. The Don has a length of 1870 km, the basin area is 422 thousand sq. km.
The source is from a ravine on the Central Russian Upland. It flows into the Taganrog Bay of the Sea of Azov. The food is mixed: 60% snow, more than 30% groundwater and almost 10% rain. Pechora has a length of 1810 km, begins in the Northern Urals and flows into the Barents Sea. The basin area is 322 thousand km2. The nature of the flow in the upper reaches is mountainous, the channel is rapid. In the middle and low reaches, the river flows through a moraine lowland and forms a wide floodplain, and at the mouth a sandy delta.
The diet is mixed: up to 55% comes from melted snow water, 25% from rainwater and 20% from groundwater. The Northern Dvina has a length of about 750 km, formed from the confluence of the Sukhona, Yuga and Vychegda rivers. Flows into the Dvina Bay. The basin area is almost 360 thousand sq. km. The floodplain is wide. At its confluence, the river forms a delta. Mixed food. The lakes on the Russian Plain differ primarily in the origin of the lake basins: 1) moraine lakes are distributed in the north of the plain in areas of glacial accumulation; 2) karst - in the basins of the Northern Dvina and Upper Volga rivers; 3) thermokarst - in the extreme northeast, in the permafrost zone; 4) floodplains (oxbow lakes) - in the floodplains of large and medium-sized rivers; 5) estuary lakes - in the Caspian lowland.
Groundwater is distributed throughout the Russian Plain. There are three artesian basins of the first order: Central Russian, East Russian and Caspian. Within their boundaries there are artesian basins of the second order: Moscow, Volga-Kama, Pre-Ural, etc. With depth, the chemical composition of water and water temperature changes.
Fresh waters lie at depths of no more than 250 m. Salinity and temperature increase with depth. At a depth of 2-3 km, the water temperature can reach 70˚C.
Soils, flora and fauna
Soils, like vegetation on the Russian Plain, have a zonal distribution. In the north of the plain there are tundra coarse humus gley soils, there are peat-gley soils, etc.
To the south, podzolic soils lie under forests. In the northern taiga they are gley-podzolic, in the middle - typical podzolic, and in the southern - soddy-podzolic soils, which are also typical for mixed forests. Gray forest soils form under broad-leaved forests and forest-steppe. In the steppes, the soils are chernozem (podzolized, typical, etc.). In the Caspian lowland, the soils are chestnut and brown desert, there are solonetzes and solonchaks.
The vegetation of the Russian Plain differs from the cover vegetation of other large regions of our country.
Broad-leaved forests are common on the Russian Plain and only here are semi-deserts. In general, the set of vegetation is very diverse, from tundra to desert. The tundra is dominated by mosses and lichens; to the south, the number of dwarf birch and willow increases.
The forest-tundra is dominated by spruce with an admixture of birch. In the taiga, spruce dominates, to the east there is an admixture of fir, and on the poorest soils - pine. Mixed forests include coniferous-deciduous species; in broad-leaved forests, where they are preserved, oak and linden dominate.
The same breeds are also typical for the forest-steppe. The steppe here occupies the largest area in Russia, where cereals predominate. The semi-desert is represented by cereal-wormwood and wormwood-hodgepodge communities.
In the fauna of the Russian Plain there are western and eastern species. The most widely represented are forest animals and, to a lesser extent, steppe animals. Western species gravitate towards mixed and deciduous forests (marten, black polecat, dormouse, mole, and some others).
Eastern species gravitate towards the taiga and forest-tundra (chipmunk, wolverine, Ob lemming, etc.). Rodents (gophers, marmots, voles, etc.) dominate in the steppes and semi-deserts; the saiga penetrates from the Asian steppes.
Natural areas
Natural zones on the East European Plain are especially clearly expressed.
From north to south they replace each other: tundra, forest-tundra, taiga, mixed and broad-leaved forests, forest-steppe, steppes, semi-deserts and deserts. The tundra occupies the coast of the Barents Sea, covers the entire Kanin Peninsula and further east, to the Polar Urals.
The European tundra is warmer and more humid than the Asian one, the climate is subarctic with marine features. The average January temperature varies from -10˚C near the Kanin Peninsula to -20˚C near the Yugorsky Peninsula. In summer about +5˚C. Precipitation 600-500 mm. The permafrost is thin, there are many swamps. On the coast there are typical tundras on tundra-gley soils, with a predominance of mosses and lichens; in addition, arctic bluegrass, pike, alpine cornflower, and sedges grow here; from bushes - wild rosemary, dryad (partridge grass), blueberry, cranberry.
To the south, shrubs of dwarf birch and willow appear. The forest-tundra extends south of the tundra in a narrow strip of 30-40 km. The forests here are sparse, the height is no more than 5-8 m, dominated by spruce with an admixture of birch and sometimes larch. Low places are occupied by swamps, thickets of small willows or birch berries. There are a lot of crowberries, blueberries, cranberries, blueberries, mosses and various taiga herbs.
Tall forests of spruce with an admixture of rowan (here its flowering occurs on July 5) and bird cherry (blooms by June 30) penetrate the river valleys. Typical animals in these zones are reindeer, arctic fox, polar wolf, lemming, mountain hare, ermine, and wolverine.
In summer there are many birds: eiders, geese, ducks, swans, snow bunting, white-tailed eagle, gyrfalcon, peregrine falcon; many blood-sucking insects. Rivers and lakes are rich in fish: salmon, whitefish, pike, burbot, perch, char, etc.
The taiga extends south of the forest-tundra, its southern border runs along the line St. Petersburg - Yaroslavl - Nizhny Novgorod - Kazan.
In the west and in the center, the taiga merges with mixed forests, and in the east with forest-steppe. The climate of the European taiga is moderate continental. Precipitation on the plains is about 600 mm, on the hills up to 800 mm. Excessive moisture. The growing season lasts from 2 months in the north and almost 4 months in the south of the zone.
The depth of soil freezing is from 120 cm in the north to 30-60 cm in the south. The soils are podzolic, in the north of the zone they are peat-gley. There are many rivers, lakes, and swamps in the taiga. The European taiga is characterized by dark coniferous taiga of European and Siberian spruce.
To the east fir is added, closer to the Urals cedar and larch. Pine forests form in swamps and sands.
In clearings and burnt areas there are birch and aspen, along the river valleys there is alder and willow. Typical animals are elk, reindeer, brown bear, wolverine, wolf, lynx, fox, mountain hare, squirrel, mink, otter, chipmunk. There are many birds: capercaillie, hazel grouse, owls, in swamps and reservoirs ptarmigan, snipe, woodcock, lapwing, geese, ducks, etc. Woodpeckers are common, especially three-toed and black, bullfinch, waxwing, bee-eater, kuksha, tits, crossbills, kinglets and others. Of reptiles and amphibians - viper, lizards, newts, toads.
In summer there are many blood-sucking insects. Mixed and, to the south, broad-leaved forests are located in the western part of the plain between the taiga and forest-steppe. The climate is moderate continental, but, unlike the taiga, softer and warmer. Winters are noticeably shorter and summers longer. The soils are soddy-podzolic and gray forest. Many rivers begin here: Volga, Dnieper, Western Dvina, etc.
There are many lakes, swamps and meadows. The boundary between forests is poorly defined. As you move east and north in mixed forests, the role of spruce and even fir increases, and the role of broad-leaved species decreases. There is linden and oak. Towards the southwest, maple, elm, and ash appear, and conifers disappear.
Pine forests are found only on poor soils. In these forests there is a well-developed undergrowth (hazel, honeysuckle, euonymus, etc.) and a herbaceous cover of honeysuckle, hoofed grass, chickweed, some grasses, and where conifers grow, there is sorrel, oxalis, ferns, mosses, etc.
Due to the economic development of these forests, the fauna has sharply declined. Elk and wild boar are found, red deer and roe deer have become very rare, and bison are found only in nature reserves. The bear and lynx have practically disappeared. Foxes, squirrels, dormouse, polecats, beavers, badgers, hedgehogs, and moles are still common; preserved marten, mink, forest cat, muskrat; muskrat, raccoon dog, and American mink are acclimatized.
Reptiles and amphibians include snakes, vipers, lizards, frogs, and toads. There are many birds, both resident and migratory. Woodpeckers, tits, nuthatch, blackbirds, jays, and owls are typical; finches, warblers, flycatchers, warblers, buntings, and waterfowl arrive in the summer. Black grouse, partridges, golden eagles, white-tailed eagle, etc. have become rare. Compared to the taiga, the number of invertebrates in the soil increases significantly. The forest-steppe zone extends south of the forests and reaches the Voronezh-Saratov-Samara line.
The climate is temperate continental with an increasing degree of continentality to the east, which affects the more depleted floristic composition in the east of the zone. Winter temperatures vary from -5˚C in the west to -15˚C in the east. The annual amount of precipitation decreases in the same direction.
Summer is very warm everywhere +20˚+22˚C. The moisture coefficient in the forest-steppe is about 1. Sometimes, especially in recent years, droughts occur in the summer. The relief of the zone is characterized by erosional dissection, which creates a certain diversity of soil cover.
The most typical gray forest soils are on loess-like loams. Leached chernozems are developed along the river terraces. The further south you go, the more leached and podzolized chernozems, and gray forest soils disappear.
Little natural vegetation has been preserved. Forests here are found only in small islands, mainly oak forests, where you can find maple, elm, and ash. Pine forests have been preserved on poor soils. Meadow herbs were preserved only on lands that were not suitable for plowing.
The fauna consists of forest and steppe fauna, but recently, due to human economic activity, the steppe fauna has become predominant.
The steppe zone extends from the southern border of the forest-steppe to the Kuma-Manych depression and the Caspian lowland in the south. The climate is moderate continental, but with a significant degree of continentalism. Summer is hot, average temperatures +22˚+23˚C. Winter temperatures vary from -4˚C in the Azov steppes, to -15˚C in the Volga steppes. Annual precipitation decreases from 500 mm in the west to 400 mm in the east. The humidification coefficient is less than 1, and droughts and hot winds are frequent in summer.
The northern steppes are less warm, but more humid than the southern ones. Therefore, the northern steppes have forbs and feather grasses on chernozem soils.
The southern steppes are dry on chestnut soils. They are characterized by solonetzity. In the floodplains of large rivers (Don, etc.) floodplain forests of poplar, willow, alder, oak, elm, etc. grow. Among the animals, rodents predominate: gophers, shrews, hamsters, field mice, etc.
Predators include ferrets, foxes, and weasels. Birds include larks, steppe eagle, harrier, corncrake, falcons, bustards, etc. There are snakes and lizards. Most of the northern steppes are now plowed. The semi-desert and desert zone within Russia is located in the southwestern part of the Caspian lowland. This zone adjoins the Caspian coast and borders the deserts of Kazakhstan. The climate is continental temperate. Precipitation is about 300 mm. Winter temperatures are negative -5˚-10˚C. The snow cover is thin, but remains for up to 60 days.
The soil freezes up to 80 cm. Summer is hot and long, average temperatures are +23˚+25˚C. The Volga flows through the zone, forming a vast delta. There are many lakes, but almost all of them are salty. The soils are light chestnut, in some places desert brown. The humus content does not exceed 1%. Salt marshes and solonetzes are widespread. The vegetation cover is dominated by white and black wormwood, fescue, thin-legged grass, and xerophytic feather grass; to the south the number of saltworts increases, tamarisk bushes appear; In spring, tulips, buttercups, and rhubarb bloom.
In the floodplain of the Volga - willow, white poplar, sedge, oak, aspen, etc. The fauna is represented mainly by rodents: jerboas, gophers, gerbils, many reptiles - snakes and lizards. Typical predators are the steppe ferret, corsac fox, and weasel. There are many birds in the Volga delta, especially during migration seasons. All natural zones of the Russian Plain have experienced anthropogenic impacts. The zones of forest-steppes and steppes, as well as mixed and deciduous forests, are especially strongly modified by humans.
It is located in western Russia from the borders with Ukraine and Belarus to the Urals. The plain is based on an ancient platform, so the topography of this natural area is generally flat. External destructive processes were of great importance in the formation of such a relief: the activity of wind, water, and 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 varying depths and comes to the surface only on the Kola Peninsula and Karelia. The Baltic Shield is formed here, with which the origin of the Khibiny on the Kola Peninsula is associated. In the rest of the territory, the foundation is covered by a sedimentary cover, varying in thickness. The origin of the elevations on the Russian Plain is explained by many reasons: the activity of the glacier, the deflection of the platform, and the raising of its foundation. The northern part of the plain was covered by an ancient glacier. The Russian Plain is almost entirely located within a temperate climate. Only the far north has a subarctic climate. Continentality on the plain increases to the east and especially to the southeast. Precipitation is brought by westerly winds (all year round) from the Atlantic. Compared to other large plains in our country, it receives the most rainfall. In the zone of maximum moisture there are the sources of large rivers of the Russian Plain: the Volga, Northern Dvina. The northwest of the plain is one of the lake regions of Russia. Along with large lakes - Ladoga, Onega, Chudskoye, Ilmensky - there are a lot of small lakes, mainly of glacial origin. In the south of the plain, where cyclones rarely pass, there is less precipitation. In summer there are often droughts and hot winds. All rivers of the Russian Plain are fed predominantly by snow and rain and spring floods. The rivers of the north of the plain are more abundant than those of the south. Groundwater plays a significant role in their nutrition. The southern rivers are low-water, and the share of groundwater 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 determine a clear change in natural zones within its borders from the north-west to the south-east from the tundra to the deserts of the temperate zone. The most complete set of natural zones can be seen here compared to other natural areas of the country. The Russian Plain has been inhabited and developed by people for a long time. 50% of Russia's population lives here. 40% of hayfields and 12% of pastures in Russia are also located here. In the depths of the plain there are deposits of iron (KMA, deposits of the Kola Peninsula), coal (Pechora basin), brown coal (Moscow basin), apatites of the Kola Peninsula, potassium 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 centuries, in many central and western regions the composition of the forest stand has been greatly changed. Many secondary small-leaved forests have 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, sunflowers, millet and other crops. There are large areas of arable land and forested areas. Rye and barley, potatoes and wheat, flax and oats are grown here.
Among exogenous factors, the most important is the energy of the Sun, which determines 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 arise. Climate changes caused the appearance of continental glaciations, eustatic drops in sea level, and transformed the nature of vegetation. The climate distribution exhibits latitudinal and vertical zoning. The latter is reflected in the relief. Climatic zonality is observed in the distribution of exogenous forms.
Based on their role in relief formation, nival, polar, humid and arid climates are distinguished. Antarctica, Greenland, the 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 developing intensively. The polar climate is typical for the north of Eurasia and North America, and the mountains of Central Asia. It is characterized by dryness, low winter temperatures, little snow, the development of a permafrost zone, and the predominance of physical weathering processes. The humid climate is common in the temperate latitudes of the northern and southern hemispheres, at the equator and monsoon regions. A lot of precipitation falls here, planar denudation and chemical weathering develop, and erosion and karst forms are formed. An arid climate is developed on the continents between 20 and 30 o N. and Yu. sh., in Central Asia and the Namib and Atacama deserts. It is characterized by low precipitation, high evaporation, the development of temperature weathering, wind activity, and the formation of rocky ledges. The latitudinal zonation of exogenous relief complicates relict relief- forms of the earth's surface formed under different conditions, in previous geological eras. For example, glacial landforms on the East European Plain.
Part II. Endogenous processes and relief
LECTURE 4. ROLE OF TECTONIC MOVEMENTS OF THE EARTH'S CRUST IN THE FORMATION OF RELIEF
There are two types of tectonic movements: vertical and horizontal. They occur both independently and in conjunction with each other. Tectonic movements manifest themselves 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 lithospheric plate tectonics. According to this concept, convection currents of heated mantle matter lead to the formation of large positive relief forms. In the axial parts of such arched uplifts, rifts are formed - negative graben-like landforms caused by faults. Examples include the East African, Baikal rifts, and the rift zone of the Mid-Atlantic Ridge. The influx of new portions of mantle material through cracks at the bottom of rifts causes spreading - the moving apart of lithospheric plates in the horizontal direction from the axial part of the rifts. Lithospheric plates are large rigid blocks of the Earth's lithosphere, separated by tectonic faults. Horizontal movements of lithospheric plates towards each other lead to their collision with each other. In the process of collision, subduction occurs—the pushing of one plate under another—or obduction—the pushing of plates onto one another. All these processes are accompanied by the formation of deep-sea trenches and island arcs (the Japanese Trench and the Japanese Islands); the emergence of large mountain systems such as 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 resulting deformations of the earth's crust find direct or inverse expression in the relief.
Vertical movements. They manifest themselves in the formation of folds , discontinuities, slopes. Elementary types of folds are anticlines and synclines. These structures can be expressed in relief in the form of direct and inverted relief. Small and simple in structure, anticlinal and synclinal folds form low ridges, hills and depressions in the relief. The developing syncline forms accumulative plains. Larger folded structures - anticlinoria - are represented in relief by large mountain ranges and depressions separating them (Fig.). For example, the anticlinorium of the Main and Side ranges of the Greater Caucasus, Kopetdag, etc. Synclinoria are expressed in relief by compensated depressions - plains filled in the upper part with Pleistocene and modern sediments. Even larger uplifts, consisting of several anticlinoria and synclinorium, are called megaanticlinoria. They form mega-forms of relief and have the appearance of a mountainous country, consisting of several ridges and depressions separating them. Megaanticlinoria include the mountain structures of the Greater and Lesser Caucasus.
The formation of folds occurs in geosynclinal areas. Folding is accompanied by faults and magmatism. These processes complicate the appearance of folds in the relief. When folded structures are exposed to external factors, a variety of structural-denudation relief appears.
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 ruptures, the following are distinguished: cracks penetrating to a relatively shallow depth; deep faults - more or less wide zones of highly fragmented rocks and ultra-deep faults, which have their roots in the mantle. Faults often exhibit faults and thrusts. In relief, these structures are usually expressed as a ledge. The height of the ledge can be used to 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. According to the nature of the structure, table and folded block mountains are distinguished. Table block mountains are composed of undisturbed rock layers, for example, the Table Jura in Africa. Folded block mountains are formed when folded structures rise along faults, for example, Altai, Tien Shan. Folded-block mountains consist of horst-anticlines - ridges and graben-synclines - depressions (Main and Side ridges of the Greater Caucasus). Under conditions of stretching and subsidence of arches along faults, graben-anticlines are formed. When blocks are uplifted along fractures in synclines, horst synclines are formed. Block mountains form in areas where folded areas are disturbed by subsequent tectonic movements along faults. Examples of block 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 the newest faults, zones of modern accumulation are developing - bands of clastic rocks, and river valleys are emerging. This is facilitated by the fracturing of rocks along fault zones and the accumulation of groundwater in them. Erosion forms formed along faults take their direction in plan. In river valleys, straight sections alternate with sharp bends at right and acute angles. Fracture zones can determine the lines of seas and oceans. For example, the Somali Peninsula, the Sinai Peninsula, the Red Sea. Along fault lines, outcrops of igneous rocks, hot and mineral springs, chains of volcanoes, esker and terminal moraine ridges, and earthquakes are often observed. Faults also play an important role within the rift zones of continents and oceans. The formation of the Baikal rift system, the East African system, and the arch of the Mid-Ocean Ridges is associated with them.
A significant role in the formation of the relief of the earth's surface is played by vertical oscillatory movements - constant reversible tectonic movements of different scales, areal distribution, different speeds, amplitudes and signs that do not create folded structures. Such movements are called epeirogenic. They create continents, control transgressions and regressions of the sea. Within platforms, their manifestation is associated with the formation of syneclises and anteclises, and in geosynclinal areas - uplifts and troughs, relief of folded-block and table mountains, faults, thrusts, horsts, folds and corresponding forms of relief. Vertical movements control the distribution of areas occupied by land and 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 breaks with a large horizontal component. According to the concept of global tectonics, they determine the horizontal movement of continents and the formation of oceans: the Atlantic and Indian. Displacements of 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 northeastern part of the Pacific Ocean. Shifts are revealed by the simultaneous displacement of positive forms (hills, mountain chains) and negative forms (river valleys) in one direction. Very large horizontal thrusts, in which the masses of the earth's crust move tens and hundreds of kilometers, are called overthrusts. The Alps and the Carpathians are gigantic mountains. 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 rift graben is the Red Sea Trench. Relative to the rift axis, its sides shift in different directions by several millimeters per year. Another form of horizontal tectonic movements are transform faults that cross the Mid-Ocean Ridges. The amplitude of horizontal displacement along them reaches several hundred kilometers.
The influence of recent and modern tectonic movements on the relief. The latest tectonic movements are movements that manifested themselves in the Neogene - Quaternary times. Their role is enormous in the deformation of the surface and the creation of positive, negative and relief forms of different orders and monoclines. For example, the southern part of the territory of Belarus at the end of Paleogene time was occupied by the sea. Now this former sea level lies on 80 – 100 m and above sea level. Areas with weakly expressed positive tectonic movements in the relief correspond to plains, low plateaus and plateaus: the East European Plain, the southern part of the West Siberian Plain, the Ustyurt Plateau. The areas with weakly expressed negative movements correspond to the basin of the Baltic Sea, the Caspian lowland, and the Polotsk lowland with thick layers of Neogene-Quaternary sediments. The Caucasus, Pamir, and Tien Shan mountains correspond to areas of intense positive tectonic movements.
Recent 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 relief and a straight relief is formed. In place of other structures, an inverted relief is formed. Relief forms that were formed as a result of endogenous processes and in the morphology of which geological structures are reflected, academician I. P. Gerasimov called morphostructures. Passive tectonic structures prepared by denudation are called lithomorphostructures.
Currently, the earth's crust is experiencing deformations of various types everywhere. Outgoing tectonic movements are experienced by the North Sea coast of Western Europe and the territory of the Netherlands, a third of which has fallen below sea level and is fenced off by dams. At the same time, Fennoscandia and northern North America are experiencing upward movements at a speed of up to 10 mm/year. Areas of alpine folding 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.
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; submerged marine coastal, glacial and karst forms; antecedent river valleys that arose as a result of the river cutting through a tectonic high; morphological appearance of erosion forms, etc.
Depending on the speed of tectonic and denudation processes, the relief can develop in two ways: an ascending type and a descending type. According to the first method, relief is formed if the tectonic uplift of the territory exceeds the intensity of denudation. In the case of upward 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 processes become more active. In river valleys, floodplains narrow or completely disappear, basement terraces and outcrops are formed on steep banks, and in river beds, rapids and ledges are formed. In the mountains, geological structures become clearly reflected in the relief, an alpine relief appears and layers of flysch clastic material accumulate in the foothills. The downward type of relief development appears if the rate of tectonic uplift of the territory is less than the value of denudation. In this case, the absolute and relative elevations of the relief decrease, the slopes decrease and flatten. River valleys expand and alluvium accumulates in them. In the mountains, the relief-forming role of snow and ice ceases, the structure of the relief is obscured, the peaks and crests of the ridges take on rounded outlines, and the size of the flysch decreases. These features 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 manifest themselves in historical and present times. Their existence is evidenced by historical and archaeological materials and repeated leveling data. 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 plants, etc.
LECTURE 5. MAGMATISM AND EARTHQUAKES AS RELIEF FORMATION FACTORS