Geography of the Volga region. Volga region composition of the Volga region state police district
Volga region
Upper Volga landscape
The relief is flat, dominated by lowlands and hilly plains. The climate is temperate continental and continental. Summer is warm, with an average monthly air temperature in July of +22° - +25°C; winter is quite cold, the average monthly air temperature in January and February is −10° - −15°С. The average annual precipitation in the north is 500-600 mm, in the south 200-300 mm. Natural zones: mixed forest (Tatarstan), forest-steppe (Samara, Penza, Ulyanovsk regions), steppe (Saratov and Volgograd regions), semi-deserts (Kalmykia, Astrakhan region). The southern part of the territory is characterized by dust storms and hot winds during the warm half of the year (from April to October).
Povolzhsky economic region
The territory area is 537.4 thousand km², the population is 17 million people, the population density is 25 people/km². The share of the population living in cities is 74%. The Volga economic region includes 94 cities, 3 million-plus cities, and 12 federal subjects. It borders in the north with the Volga-Vyatka region (Central Russia), in the south with the Caspian Sea, in the east with the Ural region and Kazakhstan, in the west with the Central Black Earth region and the North Caucasus. The economic axis is the Volga River.
Volga Federal District
Center - Nizhny Novgorod. The territory of the district makes up 6.08% of the territory of the Russian Federation. The population of the Volga Federal District as of January 1, 2008 is 30 million 241 thousand 581 people. (21.3% of the Russian population). The majority of the population consists of city dwellers. For example, in the Samara region this figure is more than 80%, which is generally slightly higher than the all-Russian figure (approximately 73%).
Notes
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2010.:Synonyms
See what "Volga region" is in other dictionaries: 1) the territory adjacent to the middle and lower reaches of the Volga and economically gravitating towards it. The elevated right bank (from the Volga region) and the low left bank (the so-called Trans-Volga region) are distinguished. 2) In natural terms, the Volga region is sometimes referred to as... ...
VOLGA REGION, territory along the middle and lower reaches of the Volga. Within the Volga region there are a relatively elevated right bank with the Volga Upland and a low-lying left bank, the so-called. Trans-Volga region. In natural terms, the Volga region is sometimes referred to as... ... Russian history
Noun, number of synonyms: 1 territory (20) ASIS Dictionary of Synonyms. V.N. Trishin. 2013… Synonym dictionary
Geogr. region in the bass R. Volga, subdivided into Verkh. (to Kazan), Avg. (Kazan - Saratov) and Nizhny. (below Saratov) Volga region. On the right bank there is the Privolzhskaya elevation, on the left bank there is a terraced lowland. Trans-Volga region. Dictionary of modern geographical... ... Geographical encyclopedia
1) the territory adjacent to the middle and lower reaches of the Volga and economically gravitating towards it. There are an elevated right bank (with the Volga Upland) and a low left bank (the so-called Trans-Volga region). 2) In natural relation to... ... encyclopedic Dictionary
The territory adjacent to the middle and lower reaches of the Volga or located close to it and economically gravitating towards it. Within the borders of P. there are a relatively elevated right bank with the Volga Upland (See Privolzhskaya ... ... Great Soviet Encyclopedia
Volga region- Pov Olga, I (to V olga) ... Russian spelling dictionary
Volga region- Volga region, territory along the middle and lower reaches of the Volga. Within the borders of P. there are a relatively elevated right bank from the Volga Upland and a low-lying left bank, the so-called Trans-Volga region. In natural terms, P. is sometimes also referred to as... Dictionary "Geography of Russia"
Volga region- VOLGA REGION, includes Tatar, Kalmyk AS, Ulyanovsk, Penza, Kuibyshev, Saratov, Volgograd (until 1961 Stalingrad), Astrakhan regions. In the pre-war years. The five-year plan (192940) created a powerful industrial base in Poland... Great Patriotic War 1941-1945: encyclopedia
Train No. 133A/133G “Volga Region” ... Wikipedia
Books
- Volga region in the 15th and 16th centuries, G.I. Peretyatkovich. Essays on the history of the region and its colonization. Research by G. Peretyatkovich. Reproduced in the original author's spelling of the 1877 edition (Moscow publishing house, typ. Grachev and...
The Volga region has favorable natural conditions for living and farming. The climate is temperate continental. The area is rich in land and water resources. However, in the lower Volga region there are droughts, accompanied by dry winds that are destructive to crops.
The relief of this area is varied. The western part (the right bank of the Volga) is elevated, hilly (the Volga Upland passes into low mountains). The eastern part (left bank) is a slightly hilly plain.
Natural and climatic conditions, terrain and the large extent of the region in the meridional direction determine the diversity of soils and vegetation. In the latitudinal direction from north to south, natural zones successively replace each other - forest, forest-steppe, steppe, then giving way to sultry semi-deserts.
The area is rich in mineral resources. They extract oil, gas, sulfur, table salt, and raw materials for the production of building materials. Until the discovery of oil fields in Western Siberia, the Volga region held first place in terms of oil reserves and production in the country. Currently, the region ranks second in the extraction of this type of raw material after West Siberia. The main oil resources are located in Tatarstan and the Samara region, and gas resources in the Saratov, Volgograd and Astrakhan regions.
Population. The population of the Volga region is 16.9 million people. The average population density is 30 people per 1 km2, but it is unevenly distributed. More than half of the population is in the Samara, Saratov regions and Tatarstan. In the Samara region, the population density is the highest - 61 people per 1 km2, and in Kalmykia - the minimum (4 people per 1 km2).
Russians predominate in the national structure of the population. Tatars and Kalmyks live compactly. The share of Chuvash and Mari among the residents of the region is noticeable. The population of the Republic of Tatarstan is 3.7 million people. (among them Russians - about 40%). About 320 thousand people live in Kalmykia. (the share of Russians is more than 30%).
The Volga region is an urbanized region. 73% of all residents live in cities and urban-type settlements. The overwhelming majority of the urban population is concentrated in regional centers, capitals of national republics and large industrial cities. Among them, the millionaire cities of Samara, Kazan, and Volgograd stand out.
Farming. In terms of the level of development of a number of industries, the region is not much inferior to highly industrialized regions, such as Central and Ural, and in some cases even surpasses them. This is one of the leading areas of the oil production, oil refining and petrochemical industries. The Volga region is the largest region of diversified agriculture. The region accounts for 20% of the gross grain harvest. The Volga economic region is distinguished by its great activity in foreign economic relations of Russia.
The main branches of industry specialization in the Volga region are oil and oil refining, gas and chemical, as well as electric power, complex mechanical engineering and the production of building materials.
The Volga region ranks second in Russia after the West Siberian economic region in oil and gas production. The amount of extracted fuel resources exceeds the needs of the region. The favorable transport and geographical position of the region led to the emergence of a whole system of main oil pipelines running both in the western and eastern directions, many of which are now of international importance.
The formation of a new oil base in Western Siberia changed the orientation of the main oil flows. Now the Volga region pipelines are “turned” entirely to the west.
The region's oil refineries (Syzran, Samara, Volgograd, Nizhnekamsk, Novokuibyshevsk, etc.) process not only their own oil, but also the oil of Western Siberia. Refineries and petrochemicals are closely related. Along with natural gas, associated gas is extracted and processed, which is used in the chemical industry.
The chemical industry of the Volga region is represented by mining chemistry (extraction of sulfur and table salt), chemistry of organic synthesis, and polymer production. The largest centers: Nizhnekamsk, Samara, Kazan, Syzran, Saratov, Volzhsky, Togliatti. In the industrial hubs of Samara - Togliatti, Saratov - Engels, Volgograd - Volzhsky, energy and petrochemical production cycles have developed. They are geographically close to the production of energy, petroleum products, alcohols, synthetic rubber, and plastics.
Rice. 1. Map of the Volga region ()
In the southeast of the European part of Russia, where the Volga flows, on both banks of the river there is one of the large economic regions of our country - Volga region(Fig. 1). River Volga(Fig. 2) serves as the main region-forming axis of the Volga region.
Rice. 2. Volga River ()
The territory includes two republics: Tatarstan, with its center in the city of Kazan, and Kalmykia, with its center in the city of Elista; six regions: Astrakhan, Volgograd, Saratov, Penza, Ulyanovsk and Samara. The core of the region is the Volga, which is the connecting link of the federal subjects that form this economic region. Area pulled out from north to south for about 1500 km and is located between two industrial cores: Central Russia and the Urals. In addition to this area borders with the Central Black Earth region, the North Caucasus, or the European south, the Ural, Volgo-Vyatka and Central regions.
Republic of Tatarstan
Tatarstan located in the center of the Russian Federation on the East European Plain, at the confluence of two largest rivers: the Volga and the Kama. Capital republic - Kazan (Fig. 3).
General square Tatarstan - over 67 thousand km 2. Length territory from north to south - 290 km, and from west to east - 460 km. Borders Tatarstan does not have any relations with foreign countries. Among the peoples inhabiting Tatarstan, the predominant population is population- Tatars (more than 53%), in second place are Russians (40%), and in third place are Chuvash (4%) (Fig. 4).
Rice. 4. Population of Tatarstan ()
Colors state flag republics mean: green - the greenery of spring, rebirth; white is the color of purity; red - maturity, energy, strength and life (Fig. 5).
Rice. 5. Flag of Tatarstan ()
Central image of the coat of arms Tatarstan - winged leopard (Fig. 6).
Rice. 6. Coat of arms of Tatarstan ()
In ancient times, this was the deity of fertility, the patron saint of children. In the coat of arms of the republic, the leopard is the patron saint of its people.
Volga region located on the East European Plain and the Caspian Lowland, its natural conditions are quite diverse and often favorable for agriculture (Fig. 7).
Rice. 7. Landscape of the Volga region ()
Territory The Volga region covers several physical-geographical zones: forest-steppe (northern part of the region), vast steppe spaces (latitude of Syzran and Samara), desert chain (southern part of the region). The Volga River and the Akhtuba River divide the region into two parts: the high right bank and the low left bank, the so-called. Trans-Volga region. On the left bank, next to the Volga, the terrain is low, the so-called. Low Volga region. To the east, the area begins to rise, forming the High Volga region, or Trans-Volga region, the southern part of which is called General Syrt. The right bank, right up to Volgograd, is occupied by the Volga Upland, the maximum height of which is 375 m above sea level. The hill is located in the Zhigulevsky Ridge opposite the city of Samara. It is characteristic of most of the Volga region that to this day a ravine-gully and river network has been formed here. In addition, the slope of the Volga Upland, located along the Volga and washed away by the river, is prone to landslides. On the territory of the Plain-Caspian Lowland, depressions and estuaries are formed into which melted spring waters flow. This makes it possible to form more fertile soils and cereal plants. The floodplain of the Volga-Akhtuba territory is also flooded during floods.
Volgaoriginates on the Valdai Hills at an altitude of 229 m above sea level, flows into to the Caspian Sea, mouth lies 28 m below sea level. The Volga is the world's largest river of internal flow, that is, one that does not flow into the World Ocean. It receives about 200 tributaries. Left tributaries- Oka, Sura, etc. - are more numerous and more water-rich than the right ones, such as Kama, Belaya, etc.
Rice. 8. Volga basin ()
Pool The Volga occupies about 1/3 of the European territory of Russia and extends from the Valdai and Central Russian Uplands in the west to the Urals in the east. Volga crosses several natural zones: forest, forest-steppe, steppe and semi-desert. The Volga is usually divided into three parts: Upper Volga (from the source to the mouth of the Oka), Middle Volga (from the confluence of the Oka to the mouth of the Kama) and Lower Volga (from the confluence of the Kama to the mouth). The great Russian river Volga inspired artists, writers, poets, and film directors (Fig. 9).
Rice. 9. I. Aivazovsky “Volga near the Zhiguli Mountains” ()
The largest, most pronounced and famous bend of the Volga River, located in the lower reaches of the Volga between the village of Usolye and the city of Syzran. Territory of Samara Luka named Luka, because here the Volga makes a bend, going around the Zhiguli Mountains (Fig. 10).
Rice. 10. Samara Luka ()
According to one of the legends, the Samara Luka was formed due to the fact that the Volga cheated, deceived: it deceived the Zhiguli and ran away to the Caspian Sea. The territory of Samarskaya Luka was divided into two parts: the National Park and the Zhigulevsky Nature Reserve. Talisman The national park chose the fox as the most common and typical animal of Samara Luka. In folklore, the fox is smart, beautiful, cunning, like the Volga, which is why it was chosen as a mascot (Fig. 11).
Her name was also Lukerya Patrikeevna.
Endemic plant species, i.e. plants that germinate only in this area are hawthorn (Fig. 12) and Tatarian bark (Fig. 13).
Rice. 12. Volga hawthorn ()
Rice. 13. Tatar barkweed ()
Most numerous animals- elk (Fig. 14), wild boar, pine marten, badger, mole rat, squirrel, fox and a small number of lynx.
average temperature January decreases to the east, and the average July temperature rises in the east and southeast. The Volga region is characterized by a pronounced continental climate type, and its continentality increases as it moves from the northwest to the southeast. In the south of the Volga region there is the driest climate zone in Europe. The Volga region is characterized by early spring and late autumn frosts. In winter, thaws sometimes occur. Droughts can form in summer and autumn, and during summer dry winds the plant cover dries up. Natural cover preserved in small areas of the region. These are forb-feather grass, fescue-feather grass and meadow steppes, solonets meadows, and in the coastal strip of the Caspian Sea - even desert landscapes.
Natural resources The Volga region is diverse. TO mineral resources include oil (Fig. 15) (Tatarstan and Samara region), gas (Astrakhan and Samara regions, Kalmykia), salt (Lake Baskunchak and Volgograd region), limestone, sand and other building materials (Volgograd and Saratov regions), there is a deposit of native sulfur (Samara region).
Rice. 15. Placement of oil and gas fields on the map of the Volga region ()
This region is quite developed agroclimatic resources, because it is warm, there are a variety of fertile soils and sufficient moisture. The region is rich and water resources. Thus, it can be said that due to the diversity of resources, various industries can be developed in the area.
Homework
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Bibliography
- Customs E.A. Geography of Russia: economy and regions: 9th grade, textbook for students of general education institutions. - M.: Ventana-Graf, 2011.
- Fromberg A.E. Economic and social geography. - 2011, 416 p.
- Atlas of economic geography, grade 9. - Bustard, 2012.
- Internet portal Komanda-k.ru ().
- Internet portal Tepka.ru ().
Composition: Astrakhan, Volgograd, Penza, Samara, Saratov, Ulyanovsk regions. Republics: Kalmykia and Tatarstan.
Area - 536.4 thousand km 2.
Population - 16 million 787 thousand people.
The region is located in a wide strip along the great Russian Volga River at the junction of the European and Asian parts of Russia.
The benefits of the economic-geographical position of the region are associated with the fact that the Volga region borders on the highly saturated Volga-Vyatka, Central Black Earth, Ural, and North Caucasus economic regions, as well as Kazakhstan.
A dense network of railways, roads and river routes ensures close economic ties between the Volga region and other regions. A significant volume of traffic occurs in the Volga-Kama basin, which is the “transport framework” of the region. Natural conditions favorable for the development of agriculture and rich mineral resources (oil, gas) create the basis for the development of the economic complex.
Natural conditions and resources
The Volga region has favorable living conditions for people, which has long attracted immigrants from other regions of Russia. The area is located within the ancient Russian platform and partly within the young plate, submerged to a considerable depth under the sedimentary cover. The relief of the lower eastern part is slightly undulating, the western part occupies a higher hypsometric position, and the remnant Volga Upland is located on its territory. The relief of the western part is hilly.
The main part of the territory is occupied by steppe and forest-steppe zones. In the north, mixed coniferous-deciduous and broad-leaved forests once grew; due to centuries of deforestation, they were almost not preserved in their natural form; in the south the steppe gives way to semi-desert.
The area has a variety of mineral resources. But the oil reserves, which made the Volga region one of the first in oil production, are severely depleted; oil production is declining. The main oil resources are concentrated in Tatarstan and the Samara region, gas - in the Saratov, Volgograd and Astrakhan regions.
There are also significant reserves of salt in lakes Baskunchak and Elton and various raw materials for the production of building materials.
Population
The modern population of the region was formed as a result of the centuries-old complex history of colonization of the region. The indigenous population is Chuvash, Mari, Mordovians. Then the Bulgars, Polovtsians, Mongols, and Nogais settled here. From the end of the 15th to the beginning of the 16th centuries, the conquest of the Volga region was one of the main goals of the Russian and then the Russian state. Many of the largest cities in the region (Volgograd, Samara, Saratov) arose as fortresses on the natural boundary (Volga), which protected Rus' from nomadic tribes.
The modern Volga region is one of the most densely populated regions of the Russian Federation. The average population density is 31 people. per 1 km 2, the Samara region is especially densely populated. Tatarstan, Saratov region.
The national structure today is dominated almost everywhere (except for Kalmykia and Tataria) by Russians. There is also a significant proportion of compactly living Tatars (16%), Chuvash and Mordovians (2 and 3%, respectively).
The level of urbanization of the Volga region is about 73%, with the population concentrated mainly in the capitals of national republics and in large industrial cities. The region has significant labor resources.
Its population is growing, mainly due to a significant influx of migrants.
The leading role belongs to mechanical engineering. In the structure of mechanical engineering, the automotive industry stands out first of all. The region produces 70% of passenger cars (Ulyanovsk, Tolyatti), 10% of freight cars (Naberezhnye Chelny) and a significant number of trolleybuses (Engels). It is planned to build a new automobile plant in Yelabuga together with foreign companies. The Volga region also specializes in instrument and machine tool manufacturing (Penza, Samara, Ulyanovsk, Saratov, Volzhsky, Kazan), aircraft manufacturing (Samara, Saratov, Kazan), (tractor building (Volgograd). All branches of the chemical industry are represented in the region. First of all, mining chemistry (extraction of sulfur - Samara region, salts - Lake Baskunchak), chemistry of organic synthesis, production of polymers. The chemical industry is developing on the basis of processing local and Western Siberian oil in Nizhnekamsk, Samara and other petrochemical complexes: Nizhnekamsk, Samara, Kazan. Syzran, Saratov, Volzhsky, Tolyatti.
A large gas-chemical complex is being created on the basis of the Astrakhan gas condensate field.
The fuel and energy complex is highly developed. The region is fully provided with its own fuel, and despite the fact that the Volga region's share in Russian oil production is falling, the region ranks second in the Russian Federation after the West Siberian economic region in oil and gas production.
About 10% of all-Russian electricity production is generated in the Volga region, part of it is transmitted via power lines to other regions of Russia. A cascade of 11 hydroelectric power stations with a total capacity of 13.5 million kW has been created on the Volga and Kama. But the reservoirs of these lowland hydroelectric power stations are very shallow, although they occupy huge areas, so the cost of electricity is very high. The environmental problems caused by the construction of hydroelectric power stations are enormous. Firstly, the great Russian Volga River no longer exists in its natural form - only a system of reservoirs. Secondly, such regulation of its flow led to a slowdown in the flow and, consequently, a decrease in the river’s ability to self-purify. And hundreds of thousands of tons of pollutants (nitrates, oil products, phenols, etc.) enter the Volga every year. A huge amount (up to 600 thousand tons) of suspended particles under conditions of altered flow contribute to its siltation and shallowing.
The rise in groundwater levels in the Volga basin has led to a catastrophic situation in the remains of the Volga forests, which are the natural protection of the Volga. Hydroelectric dams are an almost insurmountable obstacle for fish, including valuable sturgeon, whose unique herd, the largest in the world, is in danger of extinction. Thirdly, the flooding of fertile, once densely populated areas led to the loss of a significant land fund, the flooding of about 100 cities and towns, 2.5 thousand villages, thousands of historical and cultural monuments. Now the situation is only getting worse, because the old treatment plants (which filtered only about 40% of wastewater) are falling into disrepair, and there are not enough funds to repair them and build new ones. In addition, the unified system of regulation (management) of water management that existed within the USSR has been practically destroyed, and the Volga crosses the territories of many administrative-territorial units.
Therefore, the very existence of the Volga river system is under threat, and this can only be resolved through the combined efforts of all subjects of the Russian Federation located in the Volga basin.
Afro-industrial complex. In terms of agricultural land area (more than 40 million hectares), the Volga region leads among all economic regions of the country.
Up to 50% of the district's territory has been plowed. Here, 1/2 of the gross harvest of valuable durum wheat in Russia, a significant part of mustard, cereals (millet, buckwheat), and industrial crops (sugar beets, sunflowers) are grown. Meat and dairy farming has been developed. To the south of the latitude of Volgograd there are large sheep farms. In the area between the Volga and Akhtuba rivers, vegetables and melons and rice are grown.
Many areas of the Volga region are affected by soil erosion processes, which were the result of centuries-old agricultural load. This, as well as unstable weather conditions and droughts, require constant reclamation.
The developed transport network of the area largely determines its modern appearance. The Volga served as the area-forming artery of the region. The roads and railways crossing it, as well as the dense network of power lines and pipelines, are also of great importance. The Druzhba oil pipeline system is of international importance.
In the Volga region, the crystalline basement underlying the Russian Platform is greatly depressed. The depth of its immersion is not the same: under the Central Russian Upland it lies closer to the surface (200-500 m below sea level) than in the Low Volga region (2000-6000 m) and especially in the Caspian region (over 6000 m).
The elevated regions of the Volga region in their modern form were formed as a result of uplifts of the earth's crust that occurred at different times, but mainly in the Cenozoic, and the Low Trans-Volga region corresponds to the zone of young Tertiary subsidence. The Caspian lowland was also a depression in distant geological times.
Against the background of slow movements of the earth's crust, which created large features of ancient tectonics, movements subsequently occurred in the Volga region that formed individual swells, uplifts, troughs and other structures. They are partially buried under a layer of loose sediments, and partially expressed in relief. These shafts and elevations are of great importance for the search for oil and gas.
Under the weight of the overlying rocks, the underground salt layers begin to deform, and bumps and “wrinkles” appear on their surface - ridges separated by depressions. Growing mounds swell the surface of the overlying layers and bend them, which is often accompanied by collapse of the layers, their ruptures and deflections. In cases where oil-bearing deposits lie above salt layers, the mounds bring them closer to the surface, which facilitates the search for and production of oil.
The sedimentary rock strata that make up the Volga region were created over a long geological history, over many millions of years. In the depths of centuries, during the Devonian and Carboniferous periods, the sea was repeatedly replaced by swampy coastal land; During this time, sediments rich in combustible minerals accumulated. Chief among them are oil and gas, the abundant reserves of which gave the Volga region the glory of the Second Baku.
At the beginning of the next, Permian period, most of the Volga region was covered by the sea, the outlines of which often changed, and many salt lakes and semi-enclosed lagoons formed in the drying area. At this time, strata of dolomite and limestone with deposits of gypsum and rock salt were deposited here.
Throughout the Late Permian era, the sea gradually shrank and retreated to the south. In the end, it turned into a huge bitter-salty lake, which occupied the territory of the current Caspian depression. It deposited layers of rock salt of enormous thickness, which are of great industrial importance. Salt dome tectonics are associated with them. On the land bordering the Permian Sea, a layer of continental red sediments formed, making up most of the High Trans-Volga region, which geologists usually call the Permian Plateau.
In the subsequent Triassic period, most of the Volga region remained dry land, and in the Jurassic period the sea, gradually penetrating from the south, again flooded almost the entire territory, with the exception of the Permian plateau, and deposited a huge thickness of bluish, phosphorite-containing clays, oil shale, sandy clay rocks and limestones. The northern and western parts of Common Syrt after the Jurassic period finally became dry land, at the foot of which the waters of younger seas splashed.
In the Cretaceous period, ending the Mesozoic era, a vast warm sea flooded the surface of the Volga region and accumulated here powerful layers of interlayered marls, white chalk, sandstones, sands, phosphorites and all kinds of dark clays. The Serpentine Mountains near Volsk are composed of marls and chalk, which serve as the main raw materials for cement factories. Above the smooth surface of the Cretaceous sea in the areas of ancient uplifts - Don-Medveditsky, Saratov and others - rose islands, the surface of which expanded as the sea waters retreated to the south and east. Gradually, the land expanded in the north and west of the Volga Upland, which did not yet exist at that time.
In the first half of the next, Tertiary period, the sea again advances onto the land, but in the northern and western parts of the region, elevated spaces not occupied by the sea still remain. Sediments of the Paleogene sea - siliceous dark opoka clays, diatomites, tripoli, sandstones and sands are widely used as building materials.
Echoes of powerful mountain-building movements in the zone of Alpine folding are reflected in the Volga region in the form of uneven uplifts and subsidences of the earth's crust. At the same time, the main features of the modern relief are formed. First of all, the eastern strip of the Volga Upland and the northwestern part of General Syrt rose and dried, and in the middle of the Tertiary period (Miocene) they were completely freed from sea waters. Fresh flowing waters rushed into the deep depression of the ancient bed of the Volga, eroding it. At the same time, the watersheds of the Volga region were furrowed by a dense network of deeply incised ancient rivers, now dead and partially buried under a layer of young sediments.
In the Pliocene, the Caspian basin was completely separated from the Black Sea, and the size of the Caspian Sea approached modern ones. Later, as a result of uplifts of the earth's crust, the boundaries of the Caspian Sea were reduced so much that the delta of the ancient Volga reached the modern Absheron Peninsula. The Volga and other rivers that flowed into the ancient Caspian Sea accumulated here a thick layer of oil-rich sediments, which geologists call the productive formation.
The main event in the further geological history of the Volga region was the trough of the earth's crust, as a result of which the late Tertiary (late Pliocene) Akchagyl Sea invaded the low area of the Syrtov Trans-Volga region from the south. Its deep cold waters flooded the Caspian lowland, including the slopes of Ergeni, and the entire Low Volga region, right up to modern Kazan. In narrow bays along the valleys of ancient rivers, the sea protruded into the surrounding land and left a layer of blue-gray clay, the sandy layers of which contained salty waters and, in places, healing sulfur springs.
During the retreat of the Akchagyl Sea, ancient streams flowing into it from the north accumulated layers of sandy-loamy sediments in the south of the Volga Upland, on the site of modern Ergepey and in the Trans-Volga region.
The Akchagyl Sea was replaced by the Absheron Sea, the northern coast of which almost coincided with the borders of the modern Caspian Lowland. Then it too retreated.
During the Quaternary period, the Lower Volga region gradually acquired its modern appearance. The Caspian lowland and Ergeni, bordering it from the west, are isolated; the slopes of the Volga Upland and General Syrt are dissected by river valleys and furrows of temporary streams. The new network of Volga flows uses tectonic furrows and troughs, as well as the beds of ancient rivers.
In the valley of the ancient Volga, the bed of which continuously moved to the west during the Quaternary, layers of river sediment accumulated and wide terraces were formed. The formation of each of them is associated with major events: with the great glaciations of the north of the Russian Plain and with fluctuations in the level of the Caspian Sea.
Continental ice from the north did not penetrate into the Volga region. Only the “Don tongue” of the glacier, moving south along the Oka-Don Plain during the era of maximum “Dnieper” glaciation, reached the western slope of the Volga Upland, where moraine deposits were preserved in places along river valleys. But the melting of the edge of the glacier periodically increased the flow of water from the north, and due to the general humidification of the climate, the rivers became more abundant. In the northern part of the Volga region, ancient streams left powerful sand accumulations. This is the nature of the Sursky, Alatyr and other sands.