The rugged coastline of the Caspian Sea. The largest lake in the world is the Caspian Sea. Sea water temperature

The Caspian Sea is simultaneously considered as closed lake, and a full-fledged sea. The reasons for this confusion are brackish waters and a hydrological regime similar to the sea.

The Caspian Sea is located on the border of Asia and Europe. Its area is about 370 thousand km 2, its maximum depth is just over one kilometer. The Caspian Sea is conventionally divided into three almost equal parts: Southern (39% of the area), Middle (36%) and Northern (25%).

The sea washes simultaneously the Russian, Kazakh, Azerbaijani, Turkmen and Iranian shores.

Shore of the Caspian Sea(Caspian Sea) has a length of approximately 7 thousand kilometers, if you count it together with the islands. In the north, the low seashore is covered with swamps and thickets, and has multiple water channels. The eastern and western coasts of the Caspian Sea have a winding shape; in some places the shores are covered with limestone.

There are many islands in the Caspian Sea: Dash-Zira, Kur Dashi, Dzhambaisky, Boyuk-Zira, Gum, Chigil, Here-Zira, Zenbil, Ogurchinsky, Tyuleniy, Ashur-Ada, etc. Peninsulas: Mangyshlak, Tyub-Karagan, Absheron and Miankale. Their total area is approximately 400 km 2.

Flows into the Caspian Sea more than a hundred different rivers, the most significant are the Ural, Terek, Volga, Atrek, Emba, Samur. Almost all of them provide 85–95% of their annual flow to the sea.

The largest bays of the Caspian Sea: Kaydak, Agrakhansky, Kazakh, Dead Kultuk, Turkmenbashi, Mangyshlaksky, Gyzlar, Girkan, Kaydak.

Climate of the Caspian Sea

The Caspian Sea is located in three climatic zones: subtropical climate in the south, continental in the north and temperate in the middle. in winter average temperature varies from -10 to +10 degrees, in summer the air warms up to about +25 degrees. During the year, precipitation ranges from 110 mm in the east to 1500 mm in the west.

average speed wind - 3-7 m/s, but in autumn and winter it often increases to 35 m/s. The most windy areas are the coastal areas of Makhachkala, Derbent and the Absheron Peninsula.

Water temperature in the Caspian Sea fluctuates from zero to +10 degrees in winter, and from 23 to 28 degrees in the summer months. In some coastal shallow waters the water can warm up to 35-40 degrees.

Only the northern part of the sea is subject to freezing, but in especially cold winters the coastal zones of the middle part are added to it. Ice cover appears in November and disappears only in March.

Problems of the Caspian region

Water pollution is one of the main environmental problems Caspian Sea. Oil production, various harmful substances from flowing rivers, waste from nearby cities - all this negatively affects the condition of sea water. Additional troubles are created by poachers, whose actions reduce the number of fish of certain species found in the Caspian Sea.

Rising sea levels are also causing serious financial harm to all Caspian countries.

According to conservative estimates, restoring destroyed buildings and taking comprehensive measures to protect the coast from flooding costs tens of millions of dollars.

Cities and resorts on the Caspian Sea

The most big city and the port washed by the waters of the Caspian Sea is Baku. Among the others settlements Azerbaijan, located in close proximity to the sea, are Sumgait and Lankaran. On the eastern shores is the city of Turkmenbashi, and about ten kilometers from it by the sea is the large Turkmen resort of Avaza.

From the Russian side to seashore The following cities are located: Makhachkala, Izberbash, Derbent, Lagan and Kaspiysk. Astrakhan is often called a port city, although it is located approximately 65 kilometers from northern shores Caspian Sea.

Astrakhan

There are no beach holidays in this region: along the sea coast there are only continuous reed thickets. However, tourists go to Astrakhan not for lounging on the beach, but for fishing and various types active rest: diving, catamaran riding, jet skiing, etc. In July and August, excursion ships ply along the Caspian Sea.

Dagestan

For a classic seaside holiday, it’s better to go to Makhachkala, Kaspiysk or Izberbash - that’s where not only good sandy beaches, but also decent recreation centers. The range of entertainment on the seashore on the Dagestan side is quite wide: swimming, healing mud springs, windsurfing, kiting, rock climbing and paragliding.

The only disadvantage of this direction is the underdeveloped infrastructure.

In addition, among some Russian tourists There is an opinion that Dagestan is far from the most peaceful territory that is part of the North Caucasus Federal District.

Kazakhstan

A much calmer environment can be found in the Kazakh resorts of Kuryk, Atyrau and Aktau. The last one is the most popular tourist city Kazakhstan: there are many good entertainment venues and well-maintained beaches. In summer, the temperature here is very high, reaching up to +40 degrees during the daytime, and dropping only to +30 at night.

Disadvantages of Kazakhstan tourist country— the same poor infrastructure and rudimentary transport links between regions.

Azerbaijan

The most the best places Baku, Nabran, Lankaran and other Azerbaijani resorts are considered for holidays on the Caspian coast. Fortunately, everything is fine with the infrastructure in this country: for example, several modern comfortable hotels with swimming pools and beaches have been built in the Absheron Peninsula area.

However, in order to enjoy a holiday on the Caspian Sea in Azerbaijan, you need to spend a lot of money. In addition, you can only get to Baku quickly enough by plane - trains rarely run, and the journey from Russia itself takes two to three days.

Tourists should not forget that Dagestan and Azerbaijan are Islamic countries, so all “non-believers” need to adapt their usual behavior to local customs.

Subject to simple rules nothing will spoil your holiday on the Caspian Sea.

Not all of the countries located on the shores of the Caspian Sea can be listed.

Countries on the Caspian Sea

Caspian Sea is the largest inland body of water on our planet by area. It also has no churn. The Caspian Sea is classified in different ways: as the world's largest lake and as a full-fledged sea. Its surface area is 371,000 km 2 (143,200 mi 2) and its volume is 78,200 km 3. Maximum depth 1025 m. Sea salinity is about 1.2% (12 g/l). The water level in the sea constantly fluctuates due to tectonic movements and high air temperatures. Today it is 28 m below sea level.

Even the ancient inhabitants who inhabited the coast of the Caspian Sea perceived it as a real ocean. It seemed to them limitless and very large. The word "Caspian" comes from the language of these peoples.

What countries are located on the shores of the Caspian Sea?

Sea waters wash the shores of 5 coastal states. This:

Russia. The coastal zone covers Kalmykia, Dagestan and the Astrakhan region in the northwest and west. The length of the coastline is 695 km.
Kazakhstan. The coastal zone covers the east, north and northeast of the state. The length of the coastline is 2320 km.
Turkmenistan. The coastal zone covers the southeast of the country. The length of the coastline is 1200 km.
Iran. The coastal zone covers the southern part of the state. The length of the coastline is 724 km.
Azerbaijan. The coastal zone covers the southwest of the country. The length of the coastline is 955 km.

In addition, this body of water is the main object of the International Society, since it has huge reserves of natural gas and oil. The Caspian Sea is only 700 miles long, but it contains six basins with hydrocarbon reserves. Most of of which has not been mastered by humans.

CASPIAN SEA (Caspian), the largest on globe closed reservoir, endorheic brackish lake. Located on the southern border of Asia and Europe, it washes the shores of Russia, Kazakhstan, Turkmenistan, Iran and Azerbaijan. Due to the size, originality natural conditions and the complexity of hydrological processes, the Caspian Sea is usually classified as a closed inland sea.

The Caspian Sea is located in a vast area of internal drainage and occupies a deep tectonic depression. The water level in the sea is about 27 m below the level of the World Ocean, the area is about 390 thousand km 2, the volume is about 78 thousand km 3. The greatest depth is 1025 m. With a width of 200 to 400 km, the sea extends along the meridian for 1030 km.

The largest bays: in the east - Mangyshlaksky, Kara-Bogaz-Gol, Turkmenbashi (Krasnovodsky), Turkmensky; in the west - Kizlyarsky, Agrakhansky, Kizilagaj, Baku Bay; in the south there are shallow lagoons. There are many islands in the Caspian Sea, but almost all of them are small, with total area less than 2 thousand km 2. In the northern part there are numerous small islands adjacent to the Volga delta; larger ones - Kulaly, Morskoy, Tyuleniy, Chechen. Off the western shores are the Absheron archipelago, to the south lie the islands of the Baku archipelago, east coast- a narrow island, stretched from north to south, Ogurchinsky.

The northern shores of the Caspian Sea are low-lying and very sloping, characterized by the widespread development of drying areas formed as a result of surge phenomena; deltaic shores are also developed here (deltas of the Volga, Ural, Terek) with an abundant supply of terrigenous material; the Volga delta with extensive reed thickets stands out. The western shores are abrasive, south of the Absheron Peninsula, mostly accumulative deltaic type with numerous bay bars and spits. Southern Shores low-lying. The eastern shores are mostly deserted and low-lying, composed of sand.

Relief and geological structure of the bottom.

The Caspian Sea is located in a zone of increased seismic activity. In the city of Krasnovodsk (now Turkmenbashi) in 1895, a powerful earthquake measuring 8.2 on the Richter scale occurred. On the islands and coast of the southern part of the sea, eruptions of mud volcanoes are often observed, leading to the formation of new shoals, banks and small islands, which are eroded by waves and appear again.

Based on the peculiarities of physical-geographical conditions and the nature of the bottom topography in the Caspian Sea, it is customary to distinguish the Northern, Middle and Southern Caspian Seas. The Northern Caspian Sea is distinguished by exceptionally shallow waters, located entirely within the shelf with average depths of 4-5 m. Even small changes in the level here on low-lying coasts lead to significant fluctuations in the area of the water surface, therefore the boundaries of the sea in the northeastern part are shown with a dotted line on small-scale maps. The greatest depths (about 20 m) are observed only near the conventional border with the Middle Caspian, which is drawn along a line connecting the island of Chechen (north of the Agrakhan Peninsula) with Cape Tyub-Karagan on the Mangyshlak Peninsula. The Derbent depression (maximum depth 788 m) stands out in the bottom topography of the Middle Caspian Sea. The border between the Middle and Southern Caspian Sea passes over the Absheron threshold with depths of up to 180 m along the line from Chilov Island (east of the Absheron Peninsula) to Cape Kuuli (Turkmenistan). The Southern Caspian basin is the most extensive area of the sea with the greatest depths; almost 2/3 of the waters of the Caspian Sea are concentrated here, 1/3 is in the Middle Caspian, and less than 1% of the Caspian waters are located in the Northern Caspian due to shallow depths. In general, the topography of the Caspian Sea bottom is dominated by shelf areas (the entire northern part and a wide strip along the eastern coast of the sea). The continental slope is most pronounced on the western slope of the Derbent Basin and almost along the entire perimeter of the South Caspian Basin. On the shelf, terrigenous-shelly sands, shell, and oolitic sands are common; deep-sea areas of the bottom are covered with siltstone and silty sediments with a high content of calcium carbonate. In some areas of the bottom, bedrock of Neogene age is exposed. Mirabilite accumulates in the Kara-Bogaz-Gol Bay.

Tectonically, within the Northern Caspian Sea, the southern part of the Caspian syneclise of the Eastern European Platform is distinguished, which in the south is framed by the Astrakhan-Aktobe zone, composed of Devonian-Lower Permian carbonate rocks that lie on a volcanic base and contain large deposits of oil and natural combustible gas. From the southwest, Paleozoic folded formations of the Donetsk-Caspian zone (or Karpinsky ridge) are thrust onto the syneclise, which is a protrusion of the foundation of the young Scythian (in the west) and Turanian (in the east) platforms, which are separated at the bottom of the Caspian Sea by the Agrakhan-Gurievsky fault (left shear) of northeastern strike. The Middle Caspian mainly belongs to the Turanian platform, and its southwestern margin (including the Derbent depression) is a continuation of the Terek-Caspian foredeep of the fold system Greater Caucasus. The sedimentary cover of the platform and trough, composed of Jurassic and younger sediments, contains deposits of oil and combustible gas in local uplifts. The Absheron threshold, separating the Middle Caspian from the South, is a connecting link of the Cenozoic folded systems of the Greater Caucasus and Kopetdag. The South Caspian basin of the Caspian Sea with crust of oceanic or transitional type is filled with a thick (over 25 km) complex of Cenozoic sediments. Numerous large hydrocarbon deposits are concentrated in the South Caspian Basin.

Until the end of the Miocene, the Caspian Sea was a marginal sea of the ancient Tethys Ocean (from the Oligocene - the relict oceanic basin of the Paratethys). By the beginning of the Pliocene, it lost contact with the Black Sea. The Northern and Middle Caspian Seas were drained, and the paleo-Volga valley stretched through them, the delta of which was located in the Absheron Peninsula region. Delta sediments have become the main reservoir of oil and natural combustible gas deposits in Azerbaijan and Turkmenistan. In the late Pliocene, in connection with the Akchagyl transgression, the area of the Caspian Sea greatly increased and the connection with the World Ocean was temporarily resumed. The waters of the sea covered not only the bottom modern depression Caspian Sea, but also adjacent territories. In Quaternary time, transgressions (Apsheron, Baku, Khazar, Khvalyn) alternated with regressions. The southern half of the Caspian Sea is located in a zone of increased seismic activity.

Climate. The Caspian Sea, strongly elongated from north to south, is located within several climatic zones. In the northern part the climate is temperate continental, on the west coast it is warm temperate, southwestern and south coast lie within the subtropics; the east coast is dominated by a desert climate. IN winter time over the Northern and Middle Caspian, the weather is formed under the influence of Arctic continental and sea air, and the Southern Caspian is often under the influence of southern cyclones. The weather in the west is unstable and rainy, in the east it is dry. In summer, the western and northwestern regions are influenced by the spurs of the Azores atmospheric maximum, and the southeastern ones are influenced by the Iran-Afghan minimum, which together creates dry, stable warm weather. Over the sea, winds prevail in the northern and northwestern (up to 40%) and southeastern (about 35%) directions. Average wind speed is about 6 m/s, in central regions sea up to 7 m/s, in the area of the Absheron Peninsula - 8-9 m/s. Northern storm “Baku Nords” reach speeds of 20-25 m/s. Lowest average monthly temperatures Air temperatures of -10 °C are observed in January - February in the northeastern regions (in the most severe winters they reach -30 °C), in the southern regions 8-12 °C. In July - August, average monthly temperatures over the entire sea area are 25-26 °C, with a maximum of 44 °C on the east coast. The distribution of atmospheric precipitation is very uneven - from 100 mm per year on the eastern shores to 1700 mm in Lankaran. On average, the open sea receives about 200 mm of precipitation per year.

Hydrological regime. Changes in the water balance of an enclosed sea greatly influence changes in the volume of water and corresponding fluctuations in level. Average long-term components of the water balance of the Caspian Sea for the 1900-90s (km 3 /cm layer): river runoff 300/77, precipitation 77/20, underground runoff 4/1, evaporation 377/97, runoff to Kara-Bogaz- Gol 13/3, which forms a negative water balance of 9 km 3, or 3 cm of layer, per year. According to paleogeographic data, over the past 2000 years, the range of fluctuations in the level of the Caspian Sea has reached at least 7 m. Since the beginning of the 20th century, level fluctuations have shown a steady downward trend, as a result of which over 75 years the level dropped by 3.2 m and in 1977 reached -29 m (lowest position in the last 500 years). The sea surface area has decreased by more than 40 thousand km 2, which exceeds the area Sea of Azov. Since 1978, a rapid rise in level began, and by 1996 a mark of about -27 m relative to the level of the World Ocean was reached. In the modern era, fluctuations in the level of the Caspian Sea are determined mainly by fluctuations in climatic characteristics. Seasonal fluctuations in the level of the Caspian Sea are associated with the unevenness of river flow (primarily the Volga runoff), therefore the lowest level is observed in winter, the highest in summer. Short-term sharp changes in level are associated with surge phenomena; they are most pronounced in shallow northern areas and during storm surges can reach 3-4 m. Such surges cause flooding of large coastal areas of land. In the Middle and Southern Caspian Sea, surge fluctuations in level average 10-30 cm, under storm conditions - up to 1.5 m. The frequency of surges, depending on the region, is from one to 5 times a month, lasting up to one day. In the Caspian Sea, as in any closed body of water, seiche level fluctuations are observed in the form of standing waves with periods of 4-9 hours (wind) and 12 hours (tidal). The magnitude of seiche vibrations usually does not exceed 20-30 cm.

River flow in the Caspian Sea is distributed extremely unevenly. More than 130 rivers flow into the sea, which on average bring about 290 km 3 of fresh water per year. Up to 85% of the river flow falls on the Volga and the Urals and enters the shallow Northern Caspian Sea. Rivers west coast- Kura, Samur, Sulak, Terek, etc. - provide up to 10% of the flow. About 5% more fresh water brought to the South Caspian by rivers of the Iranian coast. The eastern desert shores are completely deprived of constant fresh flow.

The average speed of wind currents is 15-20 cm/s, the highest - up to 70 cm/s. In the Northern Caspian Sea, the prevailing winds create a flow directed along the northwestern coast to the southwest. In the Middle Caspian, this current merges with the western branch of the local cyclonic circulation and continues to move along the western coast. Near the Absheron Peninsula the current bifurcates. Its part in the open sea flows into the cyclonic circulation of the Middle Caspian, and the coastal part goes around the shores of the Southern Caspian and turns north, joining the coastal current that goes around the entire eastern coast. The average state of movement of Caspian surface waters is often disturbed due to variability in wind conditions and other factors. Thus, in the northeastern shallow area, a local anticyclonic gyre may arise. Two anticyclonic eddies are often observed in the Southern Caspian Sea. In the Middle Caspian in the warm season, stable northwest winds create southerly transport along the eastern coast. In light winds and during calm weather, currents may have other directions.

Wind waves develop very strongly, since the prevailing winds have a long acceleration length. Unrest develops mainly in the northwestern and southeast directions. Strong storms are observed in the open waters of the Middle Caspian Sea, in the areas of Makhachkala, the Absheron Peninsula and the Mangyshlak Peninsula. Average height waves of greatest frequency are 1-1.5 m, at wind speeds of more than 15 m/s it increases to 2-3 m. The highest wave heights are recorded during strong storms in the area of the Neftyanye Kamni hydrometeorological station: annually 7-8 m, in some cases up to 10 m .

The water temperature on the sea surface in January - February in the Northern Caspian Sea is close to freezing temperature (about -0.2 - -0.3 °C) and gradually increases in south direction up to 11 °C off the coast of Iran. In summer, surface waters warm up to 23-28 °C everywhere, except for the eastern shelf of the Middle Caspian Sea, where in July - August seasonal coastal upwelling develops and the surface water temperature drops to 12-17 °C. In winter, due to intense convective mixing, the water temperature changes little with depth. In summer, under the upper heated layer at horizons of 20-30 m, a seasonal thermocline (a layer of sharp temperature changes) is formed, separating deep cold waters from warm surface ones. In the bottom layers of waters of deep-sea depressions all year round The temperature remains 4.5-5.5 °C in the Middle Caspian and 5.8-6.5 °C in the Southern Caspian. Salinity in the Caspian Sea is almost 3 times lower than in open areas of the World Ocean, averaging 12.8-12.9‰. It should be especially emphasized that the salt composition of Caspian water is not completely identical to the composition of ocean waters, which is explained by the isolation of the sea from the ocean. The waters of the Caspian Sea are poorer in sodium salts and chlorides, but richer in carbonates and sulfates of calcium and magnesium due to the unique composition of salts entering the sea with river and underground runoff. The highest salinity variability is observed in the Northern Caspian, where in the estuarine areas of the Volga and Ural the water is fresh (less than 1‰), and as we move south, the salt content increases to 10-11‰ at the border with the Middle Caspian. The greatest horizontal salinity gradients are characteristic of the frontal zone between sea and river waters. The differences in salinity between the Middle and Southern Caspian Seas are small; salinity increases slightly from northwest to southeast, reaching 13.6‰ in the Turkmen Gulf (in Kara-Bogaz-Gol up to 300‰). Vertical changes in salinity are small and rarely exceed 0.3‰, which indicates good vertical mixing water Water transparency varies widely from 0.2 m in estuarine areas large rivers up to 15-17 m in the central regions of the sea.

According to the ice regime, the Caspian Sea is classified as a partially frozen sea. Ice conditions are observed annually only in the northern regions. The Northern Caspian is completely covered by sea ice, the Middle Caspian is partially covered (only in severe winters). Middle border sea ice runs along an arc convex to the north, from the Agrakhan Peninsula in the west to the Tyub-Karagan Peninsula in the east. Ice formation usually begins in mid-November in the extreme northeast and gradually spreads to the southwest. In January, the entire Northern Caspian Sea is covered with ice, mostly fast ice (immobile). Drifting ice borders the fast ice with a strip 20-30 km wide. Average ice thickness from 30 cm southern border up to 60 cm in the northeastern regions of the Northern Caspian Sea, in hummocky accumulations - up to 1.5 m. The destruction of the ice cover begins in the 2nd half of February. In severe winters, drifting ice is carried south, along the western coast, sometimes to the Absheron Peninsula. At the beginning of April, the sea is completely free of ice cover.

History of the study. It is believed that modern name The Caspian Sea comes from the ancient Caspian tribes who inhabited the coastal regions in the 1st millennium BC; other historical names: Hyrkan (Irkan), Persian, Khazar, Khvalyn (Khvalis), Khorezm, Derbent. The first mention of the existence of the Caspian Sea dates back to the 5th century BC. Herodotus was one of the first to claim that this body of water is isolated, that is, it is a lake. In the works of Arab scientists of the Middle Ages there is information that in the 13th-16th centuries the Amu Darya partially flowed into this sea through one of its branches. The well-known numerous ancient Greek, Arabic, European, including Russian, maps of the Caspian Sea until the beginning of the 18th century did not reflect reality and were actually arbitrary drawings. By order of Tsar Peter I, in 1714-15, an expedition was organized under the leadership of A. Bekovich-Cherkassky, who explored the Caspian Sea, in particular its eastern shores. The first map, on which the contours of the coasts are close to modern ones, was compiled in 1720 using astronomical definitions by Russian military hydrographers F.I. Soimonov and K. Verdun. In 1731, Soimonov published the first atlas, and soon the first printed sailing guide of the Caspian Sea. A new edition of maps of the Caspian Sea with corrections and additions was carried out by Admiral A.I. Nagaev in 1760. The first information on the geology and biology of the Caspian Sea was published by S. G. Gmelin and P. S. Pallas. Hydrographic research in the 2nd half of the 18th century was continued by I.V. Tokmachev, M.I. Voinovich, and at the beginning of the 19th century by A.E. Kolodkin, who for the first time carried out instrumental compass surveying of the coast. Published in 1807 new map Caspian Sea, compiled taking into account the latest inventories. In 1837, systematic instrumental observations of sea level fluctuations began in Baku. The first was completed in 1847 Full description Gulf of Kara-Bogaz-Gol. In 1878, a General Map of the Caspian Sea was published, which reflected the results of the latest astronomical observations, hydrographic surveys and depth measurements. In 1866, 1904, 1912-13, 1914-15, under the leadership of N. M. Knipovich, expeditionary research was carried out on the hydrology and hydrobiology of the Caspian Sea; in 1934, the Commission for the Comprehensive Study of the Caspian Sea was created at the USSR Academy of Sciences. A great contribution to the study of the geological structure and oil content of the Absheron Peninsula and the geological history of the Caspian Sea was made by Soviet geologists I. M. Gubkin, D. V. and V. D. Golubyatnikovs, P. A. Pravoslavlev, V. P. Baturin, S. A . Kovalevsky; in the study of water balance and sea level fluctuations - B. A. Appolov, V. V. Valedinsky, K. P. Voskresensky, L.S. Berg. After the Great Patriotic War, systematic, comprehensive research was launched in the Caspian Sea, aimed at studying the hydrometeorological regime, biological conditions and geological structure of the sea.

In the 21st century in Russia, two large scientific centers are engaged in solving the problems of the Caspian Sea. Caspian Marine Research Center (CaspMNRC), created in 1995 by government decree Russian Federation, conducts research work in hydrometeorology, oceanography and ecology. The Caspian Research Institute of Fisheries (CaspNIRKH) traces its history back to the Astrakhan Research Station [established in 1897, since 1930 the Volga-Caspian Scientific Fisheries Station, since 1948 the Caspian Branch of the All-Russian Research Institute of Fisheries and Oceanography, since 1954 the Caspian Research Institute of Marine Fisheries and Oceanography (CaspNIRO), modern name since 1965]. CaspNIRH is developing the fundamentals of conservation and rational use biological resources Caspian Sea. It consists of 18 laboratories and scientific departments - in Astrakhan, Volgograd and Makhachkala. It has a scientific fleet of more than 20 vessels.

Economic use. Natural resources The Caspian Sea is rich and varied. Significant hydrocarbon reserves are being actively developed by Russian, Kazakh, Azerbaijani and Turkmen oil and gas companies. There are huge reserves of mineral self-sedimented salts in the Kara-Bogaz-Gol Bay. The Caspian region is also known as a massive habitat for waterfowl and semi-aquatic birds. About 6 million migratory birds migrate across the Caspian Sea every year. In this regard, the Volga delta, Kyzylagaj, Northern Cheleken and Turkmenbashi bays are recognized as sites of international rank within the framework of the Ramsar Convention. The mouth areas of many rivers flowing into the sea have unique types of vegetation. The fauna of the Caspian Sea is represented by 1800 species of animals, of which 415 are vertebrate species. More than 100 species of fish live in the sea and river mouths. Marine species are of commercial importance - herring, sprat, gobies, sturgeon; freshwater - carp, perch; Arctic “invaders” - salmon, white fish. Major ports: Astrakhan, Makhachkala in Russia; Aktau, Atyrau in Kazakhstan; Turkmenbashi in Turkmenistan; Bender-Torkemen, Bender-Anzeli in Iran; Baku in Azerbaijan.

Ecological state. The Caspian Sea is under powerful anthropogenic influence due to the intensive development of hydrocarbon deposits and the active development of fishing. In the 1980s, the Caspian Sea provided up to 80% of the world's sturgeon catch. Predatory fishing in recent decades, poaching and a sharp deterioration of the environmental situation have brought many valuable fish species to the brink of extinction. The living conditions of not only fish, but also birds and sea animals (Caspian seal) have deteriorated. Countries washed by the waters of the Caspian Sea are faced with the problem of creating a set of international measures to prevent pollution of the aquatic environment and developing the most effective environmental strategy for the near future. A stable ecological state is observed only in parts of the sea remote from the coast.

Lit.: Caspian Sea. M., 1969; Comprehensive studies of the Caspian Sea. M., 1970. Issue. 1; Gul K.K., Lappalainen T.N., Polushkin V.A. Caspian Sea. M., 1970; Zalogin B.S., Kosarev A.N. Seas. M., 1999; International tectonic map of the Caspian Sea and its frame / Ed. V. E. Khain, N. A. Bogdanov. M., 2003; Zonn I. S. Caspian Encyclopedia. M., 2004.

M. G. Deev; V. E. Khain (geological structure of the bottom).

Looking through ancient maps, I constantly paid attention to how cartographers of that time depicted the Caspian Sea. On early maps it has an oval shape, slightly elongated in latitude, in contrast to its modern appearance, where the waters of the Caspian Sea extend from north to south.

Photos are clickable:

Caspian Sea on the map in modern form

And the size of the Caspian Sea is completely different. The pool area is larger than the modern one.
Let's look at some ancient maps and see for ourselves.

Here the Caspian Sea already has slightly different outlines, but it is still far from modern

All these maps show that the Caspian Sea has a system of deep rivers flowing into it along its entire perimeter. Now, the main river flowing into the Caspian Sea is the Volga. With so many rivers in the past, this must be a densely populated, fertile region. The ancient cartographers could not have made such a mistake in the geometric shapes of the reservoir and in the number of rivers flowing into it.
I note that not a single map has an image, not even a hint, of Lake Baikal (this will be useful to us later).
Not on the maps Aral Sea– it is absorbed by the Caspian, it is one basin.
It is known that the Aral Sea is rapidly drying up, simply catastrophically quickly. About 25 years ago, the USSR even had projects to save this sea by diverting Siberian rivers. Coastline The Aral Sea literally before our eyes, over the years, went beyond the horizon.

The official reason for such a catastrophic decrease in the water level in the Aral Lake-Sea is the huge withdrawal of water from the Amu Darya and Syr Darya rivers for irrigation of cotton fields.
More details

Yes, this process takes place. But not that much. It seems to me that we have witnessed climate change that began long before excessive economic activity people in this region. Many deserts in this region, steppes are the bottom of the ancient Caspian Sea. But not all. Below I will try to explain why.

In the meantime, I’ll add information from official science confirming changes in the shape and area of the Caspian basin:

The Russian scientist - academician P. S. Pallas, having visited the low-lying flat shores of the Northern Caspian Sea, wrote that the Caspian steppes are still in such a state as if they had recently emerged from under the water. This thought comes by itself if you look at these leveled vast spaces, at this sandy-clay soil mixed with sea shells, and at countless salt marshes. What kind of sea could flood these steppes if not the adjacent Caspian Sea?

Pallas also found traces of a higher sea level on small hills scattered across the Caspian lowland like islands in the sea. He discovered ledges, or terraces, on the slopes of these hills. They could only be produced sea waves, operating for a long time.

Soviet scientists found that on the shores of the Caspian Sea, especially on the eastern ones (Mangyshlak and others), three coastal terraces are found at an altitude of 26, 16 and 11 m above the modern level of the Caspian Sea. They belong to the last stage of the Khvalynsk Sea, that is, to the period 10 - 20 thousand years ago. On the other hand, there is reliable information about underwater terraces at depths of 4, 8, 12 and 16 - 20 m below the modern level.

At a depth of 16 - 20 m, there is a sharp bend in the transverse profile of the underwater slope or, in other words, a flooded terrace. The period of such low sea level dates back to the post-Khvalyn time. Later, during the New Caspian period, which began 3 - 3.5 thousand years ago, the level of the Caspian Sea generally increased, reaching a maximum in 1805.

It turns out that in relatively recent geological times the level of the Caspian Sea experienced significant fluctuations with an amplitude reaching approximately 40 meters.

A large number of coastal ledges - terraces could have formed only during transgressions (the advance of the sea onto the land) and regressions (the retreat of the sea). During transgression, the sea level remained at a certain height for a long time, and the sea surf had time to process the shores, creating beaches and coastal ramparts.

Those. scientists do not deny that even in a very recent era by geological standards, the Caspian Sea was different.

Let’s read what some figures of the past wrote about the Caspian Sea:

The first information about the Caspian Sea and its shores was found in the writings of ancient Greek and Roman scientists. However, this information, which they received from merchants, participants in wars, and seafarers, was not accurate and often contradicted each other. For example, Strabo believed that the Syr Darya flows simultaneously in two branches into the Caspian Sea and the Aral Sea. In the general geography of Claudius Ptolemy, which was a reference book for travelers until the 17th century, the Aral Sea is not mentioned at all.

The ancient maps of ancient geographers have also reached us. Distances between geographical points were then determined by the speed and time of movement of caravans and ships, and the direction of the journey - by the stars.

Herodotus (who lived around 484-425 BC) was the first to define the Caspian Sea as a sea isolated from the ocean with a width-to-length ratio of 1:6, which is very close to reality. Aristotle (384-322 BC) confirmed the conclusion of Herodotus. However, many of their contemporaries considered the Caspian Sea to be the northern bay of the ocean, which, according to their ideas, surrounded the entire then-known earth.

Ptolemy (90-168 AD), like Herodotus, considered the Caspian Sea closed, but depicted it incorrectly, in a shape approaching a circle.

Later, in 900-1200. AD Arab scientists, following Ptolemy, imagined the Caspian Sea as closed and round. You can go around the Caspian (Khazar) Sea, returning to the place from where you set off, and not encounter any obstacles except the rivers flowing into the sea, Istakhari wrote. The same was confirmed in 1280 by Marco Polo, the famous Venetian traveler who visited China. As we will see below, an incorrect idea about the shape of the Caspian Sea persisted in the Western scientific world until the beginning of the 18th century, until it was refuted by Russian hydrographers.
Source: http://stepnoy-sledopyt.narod.ru/geologia/kmore/geol.htm (B.A. Shlyamin. Caspian Sea. 1954. Geographgiz. 128 p.)

From all this, we can conclude that climatic conditions in this region were different, this indirectly proves this map of Africa:

The climate was different not only in Central Asia, but also in the largest desert on the planet - the Sahara. See a huge river crossing modern desert Africa from east to west and emptying into the Atlantic. In addition, a huge number of rivers flow into the Mediterranean Sea and the Atlantic - this indicates abundant rainfall in this region, and at least savannah vegetation. The Arabian Peninsula, too, is full of rivers and vegetation.
And this is the climate of the not so distant past, the past when people were making maps in full force.

What could have happened that changed Central Asia and northern Africa beyond recognition? Where did so much sand come from in the Karakum Desert and Sahara?

I will put forward a version based on these cards, which at first glance may not be clear:

It can be seen that the Black Sea and the Caspian Sea are connected into one basin and a huge water area flows into them from the northeast and in the center - a huge river flowing from somewhere in the north. There is a message from Persian Gulf.

Scientists also confirm these data:

It turned out that over a very long time, measured in millions of years, the Mediterranean, Black, Azov and Caspian Sea constituted a huge sea pool, connected to the World Ocean. This pool repeatedly changed its outline, area, depth, was split into separate parts and restored again.

The stages of development of this basin in historical sequence received various, purely conventional, names: the Miocene basin, or the sea that existed in the Miocene time, several million years ago, the Sarmatian, Meotic, Pontic, Akchagyl, Apsheron and the Khvalyn sea, which is closest to our time.

In dry and hot climates, a large amount of sea water evaporates, water molecules pass into the air. So, every year such a thing is carried away from the surface of the Caspian Sea great amount water particles that together they would fill a bowl with a volume of several hundred cubic kilometers. This amount of water could fill ten such reservoirs as Kuibyshevskoye.

But can water from the surface of the sea get into the bottom layers of the Caspian Sea, to a depth of 900-980 meters?

This is possible provided that the density of the surface layers of water is greater than the density of the bottom layers.

It is known that the density of sea water depends on salinity and temperature. The more salts the water contains, the denser it is, and therefore heavier. Water with high temperature less dense than cold water. Only at low temperatures (about 0-4° Celsius) is the opposite relationship given, when water, heating up, becomes more dense.

High salinity of the surface layers of the sea is created in the hot season, when the water evaporates strongly, but the salt remains in the sea. At this time, the salinity of surface waters turns out to be no less, and even slightly greater than the salinity of deep and near-bottom layers.

The temperature of surface waters in the warm season is the same everywhere, about 25-28°, that is, five times higher than at a depth of 150-200 meters. With the onset of the cold season, the temperature of the surface layers decreases and during a certain period it turns out to be 5-6° above zero.

The temperature of the bottom and deep (deeper than 150-200 m) layers of the Caspian Sea is the same (5-6°), practically unchanged throughout the year.

Under these conditions, it is possible for denser surface cold and highly saline water to sink into the bottom layers.

Only in the southern regions of the Caspian Sea the surface water temperature, as a rule, does not drop to 5-6° even in winter. And, although the descent of surface water into depth cannot directly occur in these areas, water that has descended from the surface to more depth is brought here by deep currents. northern parts seas.

A similar phenomenon is observed in the eastern part of the border zone between the Middle and Southern Caspian Seas, where cooled surface waters descend along the southern slope of the border underwater threshold and then follow a deep current into the southern regions of the sea.

This widespread mixing of surface and deep waters is confirmed by the fact that oxygen was found at all depths of the Caspian Sea.

Oxygen can only reach depths with the surface layers of water, where it comes directly from the atmosphere or as a result of photosynthesis.

If there were no continuous supply of oxygen to the bottom layers, it would quickly be absorbed by animal organisms there or spent on the oxidation of soil organic matter. Instead of oxygen, the bottom layers would be saturated with hydrogen sulfide, which is what is observed in the Black Sea. The vertical circulation in it is so weak that oxygen in sufficient quantities does not reach the depth, where hydrogen sulfide is formed.

Although oxygen has been found at all depths of the Caspian Sea, it is not in the same quantity in different seasons of the year.

The water column is richest in oxygen in winter. The harsher the winter, that is, the lower the surface temperature, the more intense the aeration process occurs, which reaches the deepest parts of the sea. Conversely, several warm winters in a row can cause the appearance of hydrogen sulfide in the bottom layers and even the complete disappearance of oxygen. But such phenomena are temporary and disappear during the first more or less severe winter.

The upper water column to a depth of 100-150 meters is especially rich in dissolved oxygen. Here the oxygen content ranges from 5 to 10 cubic meters. cm in liter. At depths of 150-450 m, there is much less oxygen - from 5 to 2 cubic meters. cm in liter.

Below 450 m there is very little oxygen and life is represented very sparsely - several species of worms and mollusks, small crustaceans.

Mixing of water masses is also caused by surge phenomena and waves.

Waves, currents, winter vertical circulation, surges, surges act constantly and are important factors mixing water It is not surprising, therefore, that no matter where we take a water sample in the Caspian Sea, everywhere chemical composition hers will be permanent. If there were no mixing of waters, all living organisms at great depths would die out. Life would only be possible in the photosynthetic zone.

Where the waters mix well and this process occurs quickly, for example in shallow areas of the seas and oceans, life is richer.

The constancy of the salt composition of the water of the Caspian Sea is a general property of the waters of the World Ocean. But this does not mean that the chemical composition of the Caspian Sea is the same as in the ocean or in any sea connected to the ocean. Consider a table showing the salt content in the waters of the ocean, the Caspian Sea and the Volga.

	Carbonates (CaCO 3)	Sulfates CaSO 4, MgSO 4	Chlorides NaCl, KCl, MgCl 2	Average water salinity ‰
Ocean	0,21	10,34	89,45
Caspian Sea	1,24	30,54	67,90	12,9
Volga river	57,2	33,4

The table shows that ocean water has very little in common with river water in terms of salt composition. In terms of salt composition, the Caspian Sea occupies an intermediate position between the river and the ocean, which is explained by the great influence of river flow on the chemical composition of Caspian water. The ratio of salts dissolved in the water of the Aral Sea is closer to the salt composition river water. This is understandable, since the ratio of the volume of river flow to the volume of water in the Aral Sea is much greater than for the Caspian Sea. A large number of sulphate salts in the Caspian Sea gives its water a bitter-salty taste, distinguishing it from the waters of the oceans and seas connected to them

The salinity of the Caspian Sea continuously increases towards the south. In the pre-estuary space of the Volga, a kilogram of water contains hundredths of a gram of salts. In the eastern regions of the Southern and Middle Caspian Sea, salinity reaches 13-14‰

Salt concentration in Caspian water small. So, in this water you can dissolve almost twenty times more salts than are present in it.

B.A. Shlyamin. Caspian Sea. 1954

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