The deepest point of the Caspian Sea. The largest islands Why is the Caspian called a lake
Caspian Sea The Caspian Sea (Greek Káspion pélagos, Latin Caspium Mare), the world's largest enclosed body of water in the USSR (RSFSR, Kazakh SSR, Turkmen SSR, Azerbaijan SSR) and Iran. It is often regarded as the greatest lake on Earth, which is inaccurate, because in terms of its size, the nature of the processes, and the history of its development, the sea is a sea. It received its name from the ancient tribes of the Caspians (See Caspians), who lived in the eastern part of the Caucasus. Other historical names -
Hyrcanian, Khvalynsk (Khvalissk), Khazar - also by the names of the ancient peoples who lived on its shores. Physico-geographical essay. General information. K. m. elongated from north to south by almost 1200 km, average width 320 km, the length of the coastline is about 7 thousand km. km(Of which more than 6,000 km within the USSR). The area is about 371 thousand sq. km 2; level at 28.5 m below the level of the World Ocean (1969). Maximum depth 1025 m. In 1929, before a significant decrease in the level of the K. m., its area was 422 thousand square meters. km 2. The largest bays are: in the north - Kizlyarsky, Komsomolets; in the east - Mangyshlaksky, Kenderli, Kazakhsky, Kara-Bogaz-Gol, Krasnovodsky; in the west - Agrakhansky, Baku Bay; in the south - shallow lagoons. There are up to 50 islands, mostly small ones (the total area is about 350 km 2),
the most significant are Kulaly, Tyuleniy, Chechen, Artem, Zhiloy, Ogurchinsky. The most significant rivers flow into the northern part of the sea - the Volga, Emba, Ural, Terek, the total annual flow of which is about 88% of the total river water flow into the Caspian. On west coast fall into major rivers Sulak, Samur, Kura and a number of smaller ones (about 7% of the runoff). The remaining 5% of the runoff is provided by the rivers of the Iranian coast (Gorgan, Heraz, Sefidrud). On the east coast, including the coast of Kara-Bogaz-Gol, there is not a single permanent watercourse. Shores. The shores of the northern part of the Caspian are low-lying and very sloping, characterized by a wide development of droughts formed as a result of surge phenomena; deltaic shores are also developed here (deltas of the Volga, Ural, Terek). In general, the coasts of the northern part are intensively growing, which is facilitated by a drop in sea level, the rapid growth of deltas, and an abundant supply of terrigenous material. Western coasts of K. m. also for the most part accumulative (numerous bay bars, spits), separate areas on the coasts of Dagestan and Absheron Peninsula- abrasive. On the eastern coast of the sea, abrasion shores, worked out in limestone, which form the adjacent semi-desert and desert plateaus, predominate. There are also accumulative forms: the Karabogaz bay separating from the sea the largest bay of the Caspian - Kara-Bogaz-Gol, the Krasnovodskaya and Kenderli spits. To the south of the Krasnovodsk Peninsula, accumulative shores predominate. Relief. According to the nature of the relief and hydrological features, the Caspian Sea is usually subdivided into the Northern Caspian, the Middle Caspian, and the Southern Caspian. Northern Caspian (area about 80 thousand sq. km 2) -
the shallowest part of the sea with depths 4-8 m.
The bottom relief is a slightly wavy accumulative plain with a series of banks and accumulative islands, the so-called Mangyshlak threshold, which separates the Northern Caspian from the Middle. Within the Middle Caspian (an area of about 138 thousand sq. km 2) stand out: Derbent depression (maximum depth 788 m),
shelf and continental slope, complicated by underwater landslides and canyons; on the northern, rather gentle slope, relics of ancient river valleys were found. In the south, the basin of the Middle Caspian is separated from the basin of the South Caspian by the Apsheron threshold, on which a number of banks and islands are located. The basin of the South Caspian (the greatest depth is 1025 m), which is about 1/3 of the area of the sea, has a narrow shelf off the western and southern (Iranian) coasts, east coast the shelf is much wider. The bottom of the depression is a flat abyssal plain. In the northern part of the basin, there are several underwater ridges with northwestern and southeastern strikes. Geological structure and minerals. The northern part of the Caspian sea is the margin of the Caspian syneclise of the East European platform; The Mangyshlak threshold is structurally connected with the Hercynian buried shaft of Karpinsky on the western coast of the sea and with the mountains of Mangyshlak on the east. The bottom of the Middle Caspian has a heterogeneous structure. Its eastern part is a submerged section of the epihercynian Turan platform; The Derbent depression, as well as the western sections of the shelf and the continental slope - the marginal foredeep of the geosyncline Greater Caucasus. The Apsheron Sill corresponds to one of the branches of the newest structures formed on the subsidence of the folded formations of the Greater Caucasus and connecting them with the folded structures of the Kopetdag. The Southern Caspian is characterized by the suboceanic structure of the earth's crust; there is no granite layer here. Under the sedimentary layer up to 25 km(which obviously indicates the great antiquity of the South Caspian depression) there is a basalt layer up to 15 km.
Up to the Upper Miocene, the Caspian as a marine basin in its geological history was closely connected with the Black Sea. After the Upper Miocene folding, this connection was interrupted, and the K. m. turned into a closed reservoir. Communication with the ocean resumed in the Upper Pliocene, in the Akchagyl age. In the Anthropogene, due to the alternation of glacial and postglacial epochs on the East European Plain, the Caspian Sea repeatedly experienced transgressions (Baku, Khazar, Khvalyn) and regressions, traces of which are preserved in the form of terraces on the sea coast and in the stratigraphy of the ancient Caspian deposits. On the shelf, terrigenous-shell sands, shells, and oolitic sands are common; deep-water areas of the bottom are covered with silty and silty sediments with a high content of calcium carbonate. In some areas of the bottom, Neogene bedrocks are exposed. At the bottom of the sea there are rich deposits of oil and gas. Oil and gas are the Apsheron threshold, the Dagestan and Turkmen regions of the sea. Promising for oil and gas are the areas of the seabed adjacent to Mangyshlak, as well as the Mangyshlak threshold. The Kara-Bogaz-Gol Bay is the largest deposit of chemical raw materials (in particular, mirabilite). Climate. The main baric centers that determine atmospheric circulation in the region of the Caspian Sea are the spur of the Asian maximum in winter and the spurs of the Azores maximum and South Asian minimum in summer. Characteristic features of the climate are: significant continentality, the predominance of anticyclonic weather conditions, dry winds, severe frosty winters (especially in the northern part), sharp temperature changes throughout the year, and poor precipitation (excluding the southwestern part of the reservoir). At atmospheric fronts, cyclonic activity is developing, which is also an important element of climate and weather in the Caspian. In the northern and middle parts of the Caspian Sea, easterly winds prevail from October to April, and northwestern winds prevail from May to September; in the southern part of the sea, the monsoon character of the winds is most pronounced. The region of the Absheron Peninsula (Baku north blowing mainly in autumn), the east coast of the middle part and northwestern region northern part; storms are frequent here, in which the wind speed reaches more than 24 m/sec.
The average long-term air temperature of the warm months (July-August) over the entire sea is 24-26 °C, the absolute maximum (up to 44 °C) is noted on the east coast. In the winter months, the temperature varies from -10 °C in the north to 12 °C in the south. An average of 200 mm precipitation per year, on the west coast - up to 400 mm,
in the arid east - 90-100 mm,
in the subtropical southwestern part of the coast - before 1700 mm. Evaporation from most of the sea surface is very high - up to 1000 mm in year; in the eastern part of the South Caspian and in the area of the Apsheron Peninsula - up to 1400 mm in year. hydrological regime. The cyclonic circulation of waters dominates in the sea, mainly due to river runoff and prevailing winds. Masses of water move from north to south along the western coast of the sea to the Apsheron Peninsula, where the current divides: one branch continues along the western coast, the other crosses the K. m. in the region of the Apsheron threshold and at east coast connects with waters moving northward along the eastern coast from the southern Caspian. In the South Caspian, cyclonic circulation is also observed, but less clearly expressed, and between Baku and the mouth of the river. Chickens complicated by local anticyclone circulation. Unstable wind currents of various directions prevail in the Northern Caspian. Their speed is usually 10-15 cm/sec, at strong winds coinciding with the direction of the currents, the speed can reach 30-40 and even 100 cm/sec. The frequent recurrence of moderate and strong winds causes a large number of days with significant waves. Maximum observed wave height up to 11 m- in the area of the Apsheron threshold. The water temperature in summer on the surface averages 24-26°C, in the south - up to 29°C, in the Krasnovodsk Bay - up to 32°C. Near the eastern shores in July and August the temperature sometimes drops to 10-12 °C. This phenomenon is associated with the driving effect of winds and the rise of deep waters. In winter, there are significant temperature contrasts: negative temperatures (up to -0.5°C) in the north, 3–7°C in the Middle Caspian, and 8–10°C in the South. The northern part of the sea usually freezes for 2-3 months., the ice thickness reaches 2 m. In the Middle Caspian harsh winters some shallow bays freeze. There are frequent cases of intense breaking of ice by the wind and their drift from the North Caspian to the south along the western coast. In some years, floating ice reaches the area of the Apsheron Peninsula and can cause significant damage to hydraulic structures in the sea. The average salinity of the waters is 12.7-12.8 ‰, the maximum (not counting the Kara-Bogaz-Gol Bay) near the eastern shores is up to 13.2 ‰, the minimum is in the northwest. - 1-2 ‰. Fluctuations in salinity over the area of the sea, along the vertical, and over time are insignificant, and only in the north are they more noticeable in connection with fluctuations in the flow of the Volga. The composition of salts differs from the usual oceanic salts in a high content of sulfates, calcium and magnesium carbonates and, accordingly, a lower content of chlorides, which is due to the influence of river runoff. Vertical mixing of waters in winter time covers the entire water column in the North Caspian and layer 200-300 m in deep-water areas, in summer and autumn it is limited to the upper layer 15-30 m. In these seasons, at the lower boundary of the upper well-heated and mixed layer (15-30 m) an intense layer of temperature jump (several degrees per meter) is formed, which prevents the spread of heat into the deep layers of the sea. Level fluctuations. Short-term non-periodic fluctuations in the level of K. m. m or downgrade to 2 m. Seishi are observed with a period of 10 min to 12 h with amplitude up to 0.7 m. There are small seasonal fluctuations in the level (about 30 cm). The level of K. m. is subject to significant long-term and secular fluctuations, determined mainly by changes in its water balance. According to geological, archaeological, historical and geomorphological data, it has been established that a high level of K. m. (up to a mark of 22 m) was noted 4-6 thousand years ago, at the beginning of AD. e. and at the beginning of the 19th century. (New Caspian transgression). It is also known that in the 7-11 centuries. n. e. was low (perhaps 2-4 m below modern). The last major decline in the level occurred since 1929 (when the level was around 26 m) until 1956-57. Now the level fluctuates within several cm around 28.5 m. In addition to climatic changes, which led to a decrease in river runoff in the Caspian Sea and an increase in evaporation from its surface, the reasons for the last drop in the level were also hydraulic engineering construction on the Volga (creation of large artificial reservoirs) and the use of river water for irrigation of arid lands and for production needs. The runoff of the K. m. in the Kara-Bogaz-Gol Bay also negatively affects the water balance, the level of which is 4 m below the level of the Caspian Sea. In general, the components of the water balance for 1970: income - precipitation 66.8 km 3, river flow 266.4 km 3, underground inflow 5 km 3, consumption - evaporation 357.3 km 3, drain to Kara-Bogaz-Gol 4 km 3 , sea water intake 1 km 3 . The excess of the expenditure over the inflow of water causes an average annual decrease in the level (for the period 1966-67) by 7 cm. To prevent a further drop in sea level (by 2000, a level decrease of 2 m) a number of measures are being developed. There is a project to transfer the flow of the northern rivers - Vychegda and Pechora - in the Volga basin, which will give the Volga and K. m. about 32 km 3 water per year; developed (1972) a project for regulating the flow Caspian waters to the Kara-Bogaz-Gol Bay. The flora and fauna of the K. m. are rather poor in species composition, but significant in biomass. More than 500 species of plants and 854 species of fish and animals, diverse in their origin, live in the Caspian Sea. Blue-green and diatom (rhizosolinae, etc.) algae predominate among the plants in the sea. Among recent invaders there are many red and brown algae. Of the flowering plants, zostera and ruppia are the most common. Chara algae provide the largest biomass (up to 30 kg for 1 m 3 bottoms). By origin, the fauna is mainly of the Neogene age, which has experienced great changes due to frequent and significant fluctuations in salinity. This group includes fish - sturgeons, herring, sprats, gobies, puplovki, from mollusks - zebra mussels and cockles, from other invertebrates - gammarids, polychaetes, sponges, one type of jellyfish. In addition, 15 species of invaders from the Arctic and Mediterranean basins live here. A noticeable group is represented by organisms of freshwater origin (from fish - pike perch). In general, a high degree of endemism is characteristic. Some organisms have migrated to the K. m. quite recently or as a result of entering on the bottoms sea vessels(mainly various foulers, such as mytilaster, rhizosalina algae, balanus, and crabs), or by conscious acclimatization by humans (for example, from fish - mullet, from invertebrates - nereis, syndesmia). Research History. Documentary evidence of the acquaintance of Russians with the K. m. and their voyages on it dates back to the 9th-10th centuries. (Arabic, Armenian, Iranian ancient manuscripts). Regular exploration of the Caspian Sea was begun by Peter I, on whose initiative an expedition was organized in 1714–15 under the leadership of A. Bekovich-Cherkassky, who explored, in particular, the eastern coast of the Caspian Sea. In the 20s. 18th century hydrographic studies of the sea were started by I.F. Soymonov; in the second half of the 18th century. they were continued by I. V. Tokmachev, M. I. Voinovich, at the beginning of the 19th century. - Kolodkin, who for the first time performed instrumental compass survey of the coast. In the middle of the 19th century a detailed instrumental hydrographic survey of the rock was carried out under the direction of N. A. Ivashintsev. The maps created as a result of these surveys served as the basis for subsequent editions of nautical charts for the Caspian until the 1930s. 20th century In the study of natural conditions K. m. in the 19th century. scientists made a great contribution - P. S. Pallas, S. G. Gmelin, G. S. Karelin, K. M. Baer, G. V. Abikh, O. A. Grim, N. I. Andrusov, I. B. . Spindler. In 1897 the Astrakhan Research Station (now the Caspian Institute of Fisheries) was founded. 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. These works were continued after 1917 by the Caspian Expedition created under the Academy of Sciences of the USSR, also led by Knipovich. In the first decades after the October Revolution, studies of owls played an outstanding role in the study of the geological structure and oil content of the Apsheron Peninsula and the geological history of the Caspian Sea. geologists I. M. Gubkin, D. V. and V. D. Golubyatnikov, P. A. Pravoslavlev, V. P. Baturin, S. A. Kovalevsky. B. A. Appolov, V. V. Valedinsky, K. P. Voskresensky, and L. S. Berg made a significant contribution to the study of the water balance and fluctuations in the level of the sea level at that time. After the Great Patriotic War From 1941 to 1945, systematic diversified studies were launched on the sea, aimed at studying the hydrometeorological regime, biological conditions, and the geological structure of the sea [Moscow State University, the Institute of Geography of the Academy of Sciences of the Azerbaijan SSR, the State Oceanographic Institute, and the Observatory of the Hydrometeorological Service. institutes of geology and development of fossil fuels (IGIRGI) and physics of the Earth of the Academy of Sciences of the USSR, the Laboratory of Aeromethods and the All-Russian Research Institute of Geophysics of the Ministry of Geology of the USSR, the Caspian Institute of Sturgeon Fisheries and other scientific institutions of the Republican Academy of Sciences and ministries]. Economic and geographical outline. The Caspian Sea has long been famous as an area for the production of valuable varieties of fish, especially sturgeon (82% of the world catch), herring, and freshwater fish (bream, pike perch, roach, and carp). As a result of the fall in sea level (which resulted in the disappearance of valuable spawning grounds), regulation of the flow of the Volga, Kura and Araks rivers, which worsened the breeding conditions for anadromous and semi-anadromous fish, etc. the number and catch of primarily valuable varieties of fish (herring, sturgeon) have declined sharply. In 1936, the gross catch of fish was about 500,000 tonnes. T, in 1956 - 461 thousand. T(respectively, the catch of sturgeon - 21.5 and 15.0, roach - 197 and 18, pike perch - 55 and 8.4 thousand tons). T). A relatively small reduction in the gross catch is due to a sharp increase in the production of low-value fish, mainly kilka. In connection with the decrease in the number of sturgeons, work is underway to breed and restore valuable fish species. In 1924, oil production began for the first time in Ilyich Bay (Baku region), but production increased especially after the Great Patriotic War of 1941-45. Oil is extracted offshore from overpasses (Oil Rocks) and artificial islands. The main regions are Priapsheronsky, Sangachalsky near the western coast, Chelekensky - near the east. Offshore oil fields provide more than 50% of all oil produced in the Azerbaijan SSR. Of great economic importance is the extraction of sodium sulfate, mirabilite and epsomite in the Kara-Bogaz-Gol region. The ever-increasing need for fresh water has led to the appearance of seawater desalination plants in the sea. the largest of them (by receiving fresh water for industrial and domestic needs in the adjacent desert and semi-desert regions) are being built (1972) in the years. Shevchenko and Krasnovodsk. The metropolitan area is of great transport importance both for internal transportation and for external communications. The main cargoes transported across the Caspian are oil, timber, grain, cotton, rice, sulfate. Major ports- Astrakhan, Baku, Makhachkala, Krasnovodsk, Shevchenko - are also connected by regular flights passenger ships. Sea railways run between Baku and Krasnovodsk. ferries. A ferry service between Makhachkala and Shevchenko is being designed (1972). In Iran, the main ports are Pahlavi and Bandar Shah. Lit.: Fluctuations in the level of the Caspian Sea, M., 1956; Fedorov P.V., Stratigraphy of Quaternary deposits and the history of the development of the Caspian Sea, M., 1957; Geological structure of the underwater slope of the Caspian Sea, M., 1962; Materials of the All-Union Conference on the Problem of the Caspian Sea, Baku, 1963; Zenkevich L. A., Biology of the Seas of the USSR, M., 1963; Leontiev O. K., Khalilov A. I., Natural conditions for the formation of the shores of the Caspian Sea, Baku, 1965; Pakhomova A. S., Zatuchnaya B. M., Hydrochemistry of the Caspian Sea, Leningrad, 1966; Geology of oil and gas fields of Azerbaijan, M., 1966; Caspian Sea, M., 1969; Complex studies of the Caspian Sea. Sat. st., c. 1, M., 1970; Gul K. K., Lappalainen T. N., Polushkin V. A., Caspian Sea, Moscow, 1970; Gul K. K., Zhilo P. V., Zhirnov V. M., Bibliographic annotated guide to the Caspian Sea. Baku, 1970. K. K. Gul, O. K. Leontiev.
Big soviet encyclopedia. - M.: Soviet Encyclopedia. 1969-1978 .
Synonyms:See what the "Caspian Sea" is in other dictionaries:
Drainage, washes the shores of Russia (Dagestan, Kalmykia, Astrakhan region) and Azerbaijan, Iran, Kazakhstan, Turkmenistan. The earliest mention of the Caspian Sea is found in Assyrian. cuneiform inscriptions (VIII VII centuries BC), where it ... ... Geographic Encyclopedia
CASPIAN SEA, the world's largest endorheic lake. The area is 376 thousand km2. Lies 27.9 m below sea level (1986). From 1929 to 1977 there was a drop in the level, from 1978 a rise began. In the North Caspian the depth is 5-8 m, in the Middle Caspian up to 788 m... Modern Encyclopedia
The Caspian Sea is the largest drainless lake on the planet. This body of water is called the sea for its huge size, brackish water and sea-like regime. The level of the Caspian Sea-lake lies much lower than the level of the World Ocean. At the beginning of 2000, he had a mark of about - 27 abs. m. At this level, the area of the Caspian Sea is ~ 393 thousand km2 and the volume of water is 78,600 km3. The average and maximum depths are 208 and 1025 m, respectively.
The Caspian Sea is elongated from south to north (Fig. 1). The Caspian washes the shores of Russia, Kazakhstan, Turkmenistan, Azerbaijan and Iran. The reservoir is rich in fish, its bottom and banks are rich in oil and gas. The Caspian Sea is quite well studied, but many mysteries remain in its regime. The most characteristic feature of the reservoir is the instability of the level with sharp drops and rises. The last rise in the level of the Caspian took place before our eyes from 1978 to 1995. It gave rise to many rumors and speculation. Numerous publications appeared in the press, which spoke about catastrophic floods and ecological catastrophe. It was often written that the rise in the level of the Caspian Sea led to the flooding of almost the entire Volga delta. What is true in the statements made? What is the reason for such behavior of the Caspian Sea?
WHAT HAPPENED TO THE CASPIAN IN THE 20TH CENTURY
Systematic observations over the level of the Caspian Sea were started in 1837. In the second half of the 19th century, the average annual values of the Caspian Sea level were in the range of marks from -26 to -25.5 abs. m and showed a slight downward trend. This trend continued into the 20th century (Fig. 2). In the period from 1929 to 1941, the sea level dropped sharply (by almost 2 m - from - 25.88 to - 27.84 abs. m). In subsequent years, the level continued to fall and, having decreased by approximately 1.2 m, reached in 1977 the lowest mark for the observation period - 29.01 abs. m. Then the sea level began to rise rapidly and, having risen by 2.35 m by 1995, reached a mark of 26.66 abs. m. In the next four years, the average sea level decreased by almost 30 cm. Its average marks were 26.80 in 1996, 26.95 in 1997, 26.94 in 1998 and 27.00 abs. m in 1999.
The decrease in sea level in the years 1930-1970 led to the shallowing of coastal waters, the extension of the coastline towards the sea, and the formation of wide beaches. The latter was perhaps the only positive consequence of the level drop. There were many more negative consequences. With a decrease in the level, the areas of forage land for fish stocks in the northern Caspian have decreased. The shallow estuarine coast of the Volga began to quickly overgrow with aquatic vegetation, which worsened the conditions for the passage of fish to spawn in the Volga. Catches of fish, especially valuable species such as sturgeon and sterlet, have sharply decreased. Shipping began to suffer damage due to the fact that the depths in the approach channels decreased, especially near the Volga delta.
The rise in the level from 1978 to 1995 was not only unexpected, but also led to even greater negative consequences. After all, both the economy and the population coastal areas already adjusted to the low level.
Many sectors of the economy began to suffer damage. Significant territories turned out to be in the zone of flooding and flooding, especially in the northern (flat) part of Dagestan, in Kalmykia and Astrakhan region. The cities of Derbent, Kaspiysk, Makhachkala, Sulak, Caspian (Lagan) and dozens of other smaller settlements suffered from the level rise. Significant areas of agricultural land have been flooded and flooded. Roads and power lines, engineering structures of industrial enterprises and public utilities are being destroyed. A threatening situation has developed with fish-breeding enterprises. Abrasion processes in the coastal zone and the effect of sea water surges have intensified. IN last years flora and fauna of the seaside and coastal zone the Volga delta suffered significant damage.
In connection with the increase in depth in the shallow waters of the Northern Caspian and the reduction in the areas occupied in these places by aquatic vegetation, the conditions for the reproduction of stocks of anadromous and semi-anadromous fish and the conditions for their migration to the delta for spawning have somewhat improved. However, the predominance of negative consequences from the rising sea level made us speak of an ecological catastrophe. The development of measures to protect national economic objects and settlements from the advancing sea began.
HOW UNUSUAL IS CURRENT CASPIAN BEHAVIOR?
Research into the life history of the Caspian Sea can help answer this question. Of course, there are no direct observations of the past regime of the Caspian Sea, but there are archaeological, cartographic and other evidence for historical time and the results of paleogeographic studies covering a longer period.
It is proved that during the Pleistocene (the last 700-500 thousand years) the level of the Caspian Sea underwent large-scale fluctuations in the range of about 200 m: from -140 to + 50 abs. m. In this period of time in the history of the Caspian, four stages are distinguished: Baku, Khazar, Khvalyn and New Caspian (Fig. 3). Each stage included several transgressions and regressions. The Baku transgression occurred 400-500 thousand years ago, the sea level rose to 5 abs. m. During the Khazar stage, there were two transgressions: the early Khazar (250-300 thousand years ago, the maximum level is 10 abs. m) and the late Khazar (100-200 thousand years ago, the highest level is 15 abs. m). The Khvalyn stage in the history of the Caspian included two transgressions: the largest for the Pleistocene period, the early Khvalyn (40-70 thousand years ago, the maximum level is 47 abs. m, which is 74 m higher than the modern one) and the late Khvalyn (10-20 thousand years ago, the rise level up to 0 abs. m). These transgressions were separated by a deep Enotaevskaya regression (22-17 thousand years ago), when the sea level dropped to -64 abs. m and was 37 m lower than the modern one.
Rice. 4. Fluctuations in the level of the Caspian Sea over the past 10 thousand years. P is the natural range of fluctuations in the level of the Caspian Sea under climatic conditions characteristic of the subatlantic epoch of the Holocene (risk zone). I-IV - stages of the New Caspian transgression; M - Mangyshlak, D - Derbent regression
Significant fluctuations in the level of the Caspian also occurred during the New Caspian stage of its history, which coincided with the Holocene (the last 10 thousand years). After the Mangyshlak regression (10 thousand years ago, a level decrease to -50 abs. m), five stages of the New Caspian transgression were noted, separated by small regressions (Fig. 4). Following sea level fluctuations, its transgressions and regressions, the outline of the reservoir also changed (Fig. 5).
Over the historical time (2000 years), the range of changes in the average level of the Caspian Sea was 7 m - from - 32 to - 25 abs. m (see Fig. 4). The minimum level in the last 2000 years was during the Derbent regression (VI-VII centuries AD), when it decreased to - 32 abs. m. During the time that has passed since the Derbent regression, the average sea level has changed in an even narrower range - from -30 to -25 abs. m. This range of level changes is called the risk zone.
Thus, the level of the Caspian has experienced fluctuations before, and in the past they were more significant than in the 20th century. Such periodic fluctuations are a normal manifestation of the unstable state of a closed reservoir with variable conditions at the outer boundaries. Therefore, there is nothing unusual in the lowering and rising of the level of the Caspian Sea.
Fluctuations in the level of the Caspian Sea in the past, apparently, did not lead to the irreversible degradation of its biota. Of course, sharp drops in sea level created temporary unfavorable conditions, for example, for fish stocks. However, with the rise in the level, the situation corrected itself. The natural conditions of the coastal zone (vegetation, benthic animals, fish) experience periodic changes along with fluctuations in sea level and, apparently, have a certain margin of stability and resistance to external influences. After all, the most valuable sturgeon herd has always been in the Caspian basin, regardless of fluctuations in sea level, quickly overcoming the temporary deterioration of living conditions.
Rumors that rising sea levels have caused flooding throughout the Volga Delta have not been confirmed. Moreover, it turned out that the increase in water levels, even in the lower part of the delta, is inadequate to the magnitude of the sea level rise. The increase in the water level in the lower part of the delta during the low water period did not exceed 0.2-0.3 m, and almost did not manifest itself during the flood. At the maximum level of the Caspian Sea in 1995, the backwater from the sea extended along the deepest branch of the Bakhtemir delta by no more than 90 km, and along other branches by no more than 30 km. Therefore, only islands on the seashore and a narrow coastal strip of the delta were flooded. Flooding in the upper and middle parts of the delta was associated with high floods in 1991 and 1995 (which is normal for the Volga delta) and with the unsatisfactory condition of protective dams. The reason for the weak effect of sea level rise on the regime of the Volga delta is the presence of a huge shallow coastal zone, which dampens the effect of the sea on the delta.
With regard to the negative impact of sea level rise on the economy and life of the population in the coastal zone, the following should be recalled. At the end of the last century, the sea level was higher than at present, and this was not perceived as an ecological disaster. And before the level was even higher. Meanwhile, Astrakhan has been known since the middle of the 13th century, and Sarai-Batu, the capital of the Golden Horde, was located here in the 13th - mid-16th centuries. These and many other settlements on the Caspian coast did not suffer from high level standing, since they were located on elevated places and during abnormal flood levels or surges, people temporarily moved from low places to higher ones.
Why, then, are the consequences of a rise in sea level even to smaller levels now perceived as a catastrophe? The cause of the enormous damage that National economy, is not a level rise, but a thoughtless and short-sighted development of a strip of land within the mentioned risk zone, released (as it turned out, temporarily!) From under the sea level after 1929, that is, when the level drops below the mark - 26 abs. m. The buildings erected in the risk zone, of course, turned out to be flooded and partially destroyed. Now, when the territory developed and polluted by man is flooded, a dangerous ecological situation is really created, the source of which is not natural processes, but unreasonable economic activity.
ABOUT THE REASONS FOR THE CASPIAN LEVEL FLUCTUATIONS
Considering the issue of the causes of fluctuations in the level of the Caspian Sea, it is necessary to pay attention to the confrontation in this area of two concepts: geological and climatic. Significant contradictions in these approaches were revealed, for example, at the international conference "Caspian-95".
According to the geological concept, two groups of processes are attributed to the causes of changes in the level of the Caspian Sea. The processes of the first group, according to geologists, lead to a change in the volume of the Caspian depression and, as a result, to changes in sea level. These processes include vertical and horizontal tectonic movements of the earth's crust, accumulation bottom sediments and seismic events. The second group includes processes that, as geologists believe, affect the underground runoff into the sea, either increasing it or decreasing it. Such processes are called periodic extrusion or absorption of water, which saturate bottom sediments under the influence of changing tectonic stresses (changes in periods of compression and tension), as well as technogenic destabilization of the subsoil due to oil and gas production or underground nuclear explosions. It is impossible to deny the fundamental possibility of the influence of geological processes on the morphology and morphometry of the Caspian depression and underground runoff. However, at present, the quantitative relationship of geological factors with fluctuations in the level of the Caspian Sea has not been proven.
There is no doubt that tectonic movements played a decisive role in the initial stages of the formation of the Caspian basin. However, if we take into account that the Caspian Sea basin is located within a geologically heterogeneous territory, which results in a periodic rather than linear nature of tectonic movements with repeated sign changes, then one should hardly expect a noticeable change in the capacity of the basin. Not in favor of the tectonic hypothesis is the fact that the coastlines of the New Caspian transgressions in all sections of the Caspian coast (with the exception of certain areas within the Apsheron archipelago) are at the same level.
There are no grounds to consider the change in the capacity of its basin due to the accumulation of precipitation as the reason for fluctuations in the level of the Caspian Sea. The rate of filling the basin with bottom sediments, among which the main role is played by river discharges, is estimated, according to modern data, at a value of about 1 mm/year or less, which is two orders of magnitude less than the currently observed changes in sea level. Seismic deformations, which are noted only near the epicenter and attenuate at close distances from it, cannot have any significant effect on the volume of the Caspian Basin.
With regard to periodic large-scale unloading groundwater to the Caspian, its mechanism is still unclear. At the same time, this hypothesis is contradicted, according to E.G. Maev, firstly, the undisturbed stratification of interstitial waters, indicating the absence of noticeable migrations of waters through the thickness of bottom sediments, and secondly, the absence of proven powerful hydrological, hydrochemical and sedimentation anomalies in the sea, which should have accompanied a large-scale discharge of groundwater capable of affect changes in water levels.
The main evidence of the insignificant role of geological factors at present is the convincing quantitative confirmation of the plausibility of the second, climatic, or rather, water-balance concept of Caspian level fluctuations.
CHANGES IN THE COMPONENTS OF THE CASPIAN WATER BALANCE AS THE MAIN CAUSE OF ITS LEVEL FLUCTUATIONS
For the first time, fluctuations in the level of the Caspian Sea were explained by changes in climatic conditions (more specifically, river runoff, evaporation and precipitation on the sea surface) by E.Kh. Lenz (1836) and A.I. Voeikov (1884). Later, the leading role of changes in the components of the water balance in sea level fluctuations was again and again proved by hydrologists, oceanologists, physicogeographers and geomorphologists.
The key to most of the studies mentioned is the compilation of the water balance equation and the analysis of its components. The meaning of this equation is as follows: the change in the volume of water in the sea is the difference between the incoming (river and underground runoff, atmospheric precipitation on the sea surface) and outgoing (evaporation from the sea surface and outflow of water into the Kara-Bogaz-Gol Bay) components of the water balance. The change in the level of the Caspian is the quotient of dividing the change in the volume of its waters by the area of the sea. The analysis showed that the leading role in the water balance of the sea belongs to the ratio of the flow of the Volga, Ural, Terek, Sulak, Samur, Kura rivers and visible or effective evaporation, the difference between evaporation and atmospheric precipitation on the sea surface. An analysis of the components of the water balance revealed that the largest contribution (up to 72% of the dispersion) to the level variability comes from the inflow of river waters, and more specifically, the runoff formation zone in the Volga basin. As for the reasons for the change in the flow of the Volga itself, they are associated, as many researchers believe, with the variability of atmospheric precipitation (mainly winter) in the river basin. And the mode of precipitation, in turn, is determined by the circulation of the atmosphere. It has long been proven that the latitudinal type of atmospheric circulation contributes to an increase in precipitation in the Volga basin, while the meridional type contributes to a decrease.
V.N. Malinin found that the root cause of moisture in the Volga basin must be sought in North Atlantic specifically in the Norwegian Sea. It is there that the increase in evaporation from the sea surface leads to an increase in the amount of moisture transferred to the continent, and, accordingly, to an increase in atmospheric precipitation in the Volga basin. The latest data on the water balance of the Caspian Sea, received by the staff of the State Oceanographic Institute R.E. Nikonova and V.N. Bortnik, are given with the author's clarifications in Table. 1. These data convincingly prove that the main reasons for both the rapid drop in sea level in the 1930s and the sharp rise in 1978-1995 were changes in river flow, as well as apparent evaporation.
Keeping in mind that river runoff is one of the main factors affecting the water balance and, as a result, the level of the Caspian Sea (and the Volga runoff provides at least 80% of the total river runoff to the sea and about 70% of the incoming part of the Caspian water balance), it would be interesting to find a connection between sea level and the flow of one Volga, measured most accurately. Direct correlation of these quantities does not give satisfactory results.
However, the relationship between the sea level and the Volga runoff is well traced if the river runoff is not taken into account for each year, but the ordinates of the difference integral runoff curve are taken, that is, the sequential sum of the normalized deviations of the annual runoff values from the long-term average value (norm). Even a visual comparison of the course of the average annual levels of the Caspian Sea and the difference integral curve of the Volga runoff (see Fig. 2) makes it possible to reveal their similarity.
For the entire 98-year period of observations of the Volga runoff (the village of Verkhneye Lebyazhye at the head of the delta) and the sea level (Makhachkala), the correlation coefficient of the relationship between the sea level and the ordinates of the difference integral runoff curve was 0.73. If we discard years with small level changes (1900-1928), then the correlation coefficient increases to 0.85. If for analysis we take a period with a rapid decline (1929-1941) and a rise in the level (1978-1995), then the overall correlation coefficient will be 0.987, and separately for both periods 0.990 and 0.979, respectively.
The presented calculation results fully confirm the conclusion that during periods of a sharp decrease or rise in sea level, the levels themselves are closely related to the runoff (more precisely, to the sum of its annual deviations from the norm).
A special task is to assess the role of anthropogenic factors in fluctuations in the level of the Caspian Sea, and above all, the reduction in river flow due to its irretrievable losses for filling reservoirs, evaporation from the surface of artificial reservoirs, and water withdrawal for irrigation. It is believed that since the 1940s, irretrievable water consumption has been steadily increasing, which has led to a reduction in the inflow of river waters to the Caspian Sea and an additional decrease in its level compared to the natural one. According to V.N. Malinin, by the end of the 1980s, the difference between the actual sea level and the restored (natural) level reached almost 1.5 m. about 26 km3/year). If it were not for the withdrawal of river runoff, then the rise in sea level would have begun not at the end of the 70s, but at the end of the 50s.
The increase in water consumption in the Caspian basin by 2000 was predicted first to 65 km3/year, and then to 55 km3/year (36 of them were in the Volga). Such an increase in irretrievable losses of river runoff should have lowered the level of the Caspian by more than 0.5 m by 2000. In connection with the assessment of the impact of irreversible water consumption on the level of the Caspian, we note the following. First, estimates of water withdrawal volumes and evaporation losses from the surface of reservoirs in the Volga basin found in the literature seem to be significantly overestimated. Secondly, forecasts of water consumption growth turned out to be erroneous. The forecasts included the rate of development of water-consuming sectors of the economy (especially irrigation), which not only turned out to be unrealistic, but also gave way to a decline in production in recent years. In fact, as A.E. Asarin (1997), by 1990 water consumption in the Caspian basin was about 40 km3/year, and has now decreased to 30-35 km3/year (in the Volga basin to 24 km3/year). Therefore, the "anthropogenic" difference between the natural and actual sea levels is currently not as large as predicted.
ON POSSIBLE FLUCTUATIONS OF THE CASPIAN LEVEL IN THE FUTURE
The author does not set himself the goal of analyzing in detail the numerous forecasts of fluctuations in the level of the Caspian Sea (this is an independent and difficult task). The main conclusion from the assessment of the results of forecasting fluctuations in the level of the Caspian can be drawn as follows. Although the forecasts were based on completely different approaches (both deterministic and probabilistic), there was not a single reliable forecast. The main difficulty in using deterministic forecasts based on the sea water balance equation is the lack of development of the theory and practice of ultra-long-term forecasts of climate change over large areas.
When the sea level decreased in the 30-70s, most researchers predicted its further fall. In the last two decades, when sea level rise began, most forecasts predicted an almost linear and even accelerating rise in level to -25 and even -20 abs. m and above at the beginning of the XXI century. In this case, three factors were not taken into account. First, the periodic nature of fluctuations in the level of all endorheic reservoirs. The instability of the Caspian level and its periodic nature are confirmed by the analysis of its current and past fluctuations. Secondly, at sea level close to - 26 abs. m, the flooding of large sor bays on the northeastern coast of the Caspian Sea - Dead Kultuk and Kaydak, as well as low-lying areas in other places of the coast, dried up at a low standing level, will begin. This would lead to an increase in the area of shallow waters and, as a consequence, an increase in evaporation (up to 10 km3/year). With a higher sea level, the outflow of water to Kara-Bogaz-Gol will increase. All this should stabilize or at least slow down the level growth. Thirdly, level fluctuations under the conditions of the modern climatic epoch (the last 2000 years), as shown above, are limited by the risk zone (from -30 to -25 abs. m). Taking into account the anthropogenic decrease in runoff, the level is unlikely to exceed the mark of 26-26.5 abs. m.
The decrease in average annual levels in the last four years by a total of 0.34 m, possibly indicates that in 1995 the level reached its maximum (-26.66 abs. m), and a change in the trend of the Caspian level. In any case, the prediction that sea level is unlikely to exceed 26 abs. m, apparently justified.
In the 20th century, the level of the Caspian Sea changed within 3.5 m, first dropping and then rising sharply. Such behavior of the Caspian Sea is the normal state of a closed reservoir as an open dynamic system with variable conditions at its inlet.
Each combination of incoming (river runoff, precipitation on the sea surface) and outgoing (evaporation from the surface of the reservoir, outflow to the Kara-Bogaz-Gol Bay) components of the Caspian water balance corresponds to its own level of equilibrium. Since the components of the water balance of the sea also change under the influence of climatic conditions, the level of the reservoir fluctuates, trying to reach an equilibrium state, but never reaches it. Ultimately, the trend of changing the level of the Caspian in given time depends on the ratio of precipitation minus evaporation in the watershed (in the basins of the rivers that feed it) and evaporation minus precipitation over the reservoir itself. There is really nothing unusual about the recent rise of the Caspian Sea level by 2.3 m. Such level changes have occurred many times in the past and did not cause irreparable damage. natural wealth Caspian. The current rise in sea level has become a catastrophe for the economy of the coastal zone only because of the unreasonable development of this risk zone by man.
Vadim Nikolaevich Mikhailov, Doctor of Geographical Sciences, Professor of the Department of Terrestrial Hydrology of the Faculty of Geography of Moscow State University, Honored Worker of Science of the Russian Federation, full member of the Academy of Water Management Sciences. Area of scientific interests - hydrology and water resources, interaction of rivers and seas, deltas and estuaries, hydroecology. Author and co-author of about 250 scientific papers, including 11 monographs, two textbooks, four scientific and methodological manuals.
The Caspian Sea is the most big lake our planet, which is located in a depression on the earth's surface (the so-called Aral-Caspian lowland) on the territory of Russia, Turkmenistan, Kazakhstan, Azerbaijan and Iran. Although they consider it as a lake, because it is not connected with the World Ocean, but by the nature of the formation processes and the history of origin, in terms of its size, the Caspian Sea is a sea.
The area of the Caspian Sea is about 371 thousand km2. The sea, stretched from north to south, has a length of about 1200 km and an average width of 320 km. The length of the coastline is about 7 thousand km. The Caspian Sea is located 28.5 m below the level of the World Ocean and its greatest depth is 1025 m. There are about 50 islands in the Caspian Sea, mostly small in area. Large islands include such islands as Tyuleniy, Kulaly, Zhiloy, Chechen, Artem, Ogurchinsky. There are also many bays in the sea, for example: Kizlyarsky, Komsomolets, Kazakh, Agrakhansky, etc.
The Caspian Sea is fed by more than 130 rivers. The largest amount of water (about 88% of the total flow) is brought by the Ural, Volga, Terek, Emba rivers, which flow into the northern part of the sea. About 7% of the runoff is provided by the large rivers Kura, Samur, Sulak and small rivers flowing into the sea on the western coast. To the south Iranian coast the Heraz, Gorgan, Sefidrud rivers flow, which bring only 5% of the flow. IN eastern part no river flows into the sea. The water in the Caspian Sea is salty, its salinity ranges from 0.3‰ to 13‰.
The shores of the Caspian Sea
The shores have a different landscape. The shores of the northern part of the sea are low and gentle, surrounded by low semi-desert and somewhat elevated desert. In the south, the shores are partially low-lying, they are bordered by a coastal lowland of a small area, behind which the Elburs ridge runs along the coast, which in some places comes close to the coast. In the west, the ridges of the Greater Caucasus approach the coast. In the east there is an abrasion coast, worked out in limestones, semi-desert and desert plateaus approach it. The coastline is very variable due to periodic fluctuations in water levels.
The climate of the Caspian Sea is different:
Continental in the north;
Moderate in the middle
Subtropical in the south.
At the same time, severe frosts and snowstorms are raging on the northern coast, and fruit trees and magnolias bloom on the southern coast. In winter, strong storm winds rage on the sea.
Large cities and ports are located on the coast of the Caspian Sea: Baku, Lankaran, Turkmenbashi, Lagan, Makhachkala, Kaspiysk, Izberbash, Astrakhan, etc. 
The fauna of the Caspian Sea is represented by 1809 animal species. More than 70 species of fish are found in the sea, including: herring, gobies, stellate sturgeon, sturgeon, beluga, white salmon, sterlet, pike perch, carp, bream, vobla, etc. Of the marine mammals in the lake, only the world's smallest Caspian seal is found, which not found in other seas. The Caspian lies on the main bird migration route between Asia, Europe and the Middle East. Every year, about 12 million birds fly over the Caspian during their migration period, and another 5 million usually winter here.
Vegetable world
The flora of the Caspian Sea and its coast is 728 species. Basically, algae inhabit the sea: diatoms, blue-green, red, char, brown and others, from flowering ones - rupee and zoster.
The Caspian Sea is rich in natural resources, many oil and gas fields are being developed in it, in addition, limestone, salt, sand, stone and clay are also mined here. The Caspian Sea is connected by the Volga-Don Canal with Sea of Azov, shipping is well developed. A lot of different fish are caught in the reservoir, including more than 90% of the world's sturgeon catch.
The Caspian Sea is also a recreation area, on its shores there are rest houses, tourist bases and sanatoriums.
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The Caspian Sea is located in different geographical zones. It plays a big role in world history, is an important economic region and source of resources. The Caspian Sea is a unique body of water.
Short description
This sea has big sizes. The bottom is covered with oceanic bark. These factors make it possible to classify it as a sea.
It is a closed reservoir, has no drains and is not connected with the waters of the oceans. Therefore, it can also be attributed to the category of lakes. In this case, it will be the largest lake on the planet.
The approximate area of the Caspian Sea is about 370 thousand square kilometers. The volume of the sea changes depending on the various fluctuations in the water level. The average value is 80 thousand cubic kilometers. The depth differs in its parts: the southern one has great depth than the north. The average depth is 208 meters, the highest value in the southern part exceeds 1000 meters.
The Caspian Sea plays an important role in the development of trade relations between the countries. The resources mined in it, as well as other trade items, were transported to different countries since the development of navigation at sea. Since the Middle Ages, merchants have delivered exotic goods, spices and furs. Today, in addition to transporting resources, ferries between cities are carried out by sea. The Caspian Sea is also connected by a navigable canal through the rivers with the Sea of Azov.
Geographic characteristics
The Caspian Sea is located between two continents - Europe and Asia. Washes the territory of several countries. These are Russia, Kazakhstan, Iran, Turkmenistan and Azerbaijan.
It has more than 50 islands, both large and small in size. For example, the islands of Ashur-Ada, Tyuleniy, Chigil, Gum, Zenbil. As well as the peninsulas, the most significant - Absheron, Mangyshlak, Agrakhan and others.
The Caspian Sea receives the main influx of water resources from the rivers flowing into it. In total, there are 130 tributaries of this reservoir. The largest is the Volga River, which brings the bulk of the water. The Kheras, Ural, Terek, Astarchay, Kura, Sulak and many others rivers also flow into it.
The waters of this sea form many bays. Among the largest are: Agrakhansky, Kizlyarsky, Turkmenbashi, Girkan Bay. In the eastern part there is a bay-lake called Kara-Bogaz-Gol. It communicates with the sea by a small strait.
Climate
The climate is characterized by the geographical location of the sea, therefore it has several types: from continental in the northern region to subtropical in the south. This affects the air and water temperatures, which have great contrasts depending on the part of the sea, especially in the cold season.
in winter average temperature air in the northern region is about -10 degrees, water reaches a value of -1 degree.
In the southern region, the temperature of air and water in winter warms up to an average of +10 degrees.
During the summer, the air temperature in northern zone reaches +25 degrees. Much hotter in the south. The maximum recorded value here is + 44 degrees.
Resources
The natural resources of the Caspian Sea contain large reserves of various deposits.
One of the most valuable resources of the Caspian Sea is oil. Mining has been carried out since about 1820. Springs were opened on the territory of the seabed and its coast. By the beginning of the new century, the Caspian was at the forefront in obtaining this valuable product. During this time, thousands of wells were opened, which made it possible to extract oil on a huge industrial scale.
The Caspian Sea and the territory adjacent to it also have rich deposits of natural gas, mineral salts, sand, lime, several types of natural clay and rocks.
Inhabitants and fisheries
The biological resources of the Caspian Sea are very diverse and highly productive. It contains more than 1500 species of inhabitants, rich in commercial fish species. Population depends on climatic conditions in different parts of the sea.
In the northern part of the sea, pike perch, bream, catfish, asp, pike and other species are more common. Gobies, mullet, bream, herring live in the western and eastern. Southern waters are rich various representatives. One of the many are sturgeons. According to their content, this sea occupies a leading place among other reservoirs.
Among the wide variety, tuna, beluga, stellate sturgeon, sprat and many others are also caught. In addition, there are mollusks, crayfish, echinoderms and jellyfish.
The mammal Caspian seal lives in the Caspian Sea, or This animal is unique and lives only in these waters.
The sea is also characterized by a high content of various algae, for example, blue-green, red, brown; sea grass and phytoplankton.
Ecology
The extraction and transportation of oil has a huge negative impact on the ecological situation of the sea. The ingress of oil products into water is almost inevitable. Oil stains cause irreparable damage to marine habitats.
The main inflow of water resources to the Caspian Sea is provided by rivers. Unfortunately, most of them have a high level of pollution, which degrades the quality of the water in the sea.
Industrial and domestic effluents from the surrounding cities are poured into the sea in large quantities, which also damages the environment.
Poaching causes great damage to the marine habitat. Sturgeon species are the main target for illegal catching. This significantly reduces the number of sturgeon and threatens the entire population of this type.
The above information will help to assess the resources of the Caspian Sea, to briefly study the characteristics and ecological situation of this unique reservoir.
Caspian lake is one of the most unique places on the ground. It keeps many secrets connected with the history of the development of our planet.
Position on the physical map
The Caspian is an internal drainless salt lake. The geographical position of the Caspian Lake is the continent of Eurasia at the junction of parts of the world (Europe and Asia).
The length of the lakeshore line is from 6500 km to 6700 km. Taking into account the islands, the length increases to 7000 km.
The coastal areas of the Caspian Lake are mostly low-lying. Their northern part is indented by the channels of the Volga and the Urals. The river delta is rich in islands. The surface of the water in these areas is covered with thickets. Swampiness of large areas of land is noted.
The eastern coast of the Caspian adjoins to the lake. There are significant limestone deposits on the shores of the lake. The western and part of the eastern coast is characterized by a winding coastline.
The Caspian lake on the map is represented by a significant size. The entire territory adjacent to it was called the Caspian Sea.
Some characteristics
The Caspian Lake in terms of its area and the volume of water in it has no equal on Earth. It stretches from north to south for 1049 kilometers, and its longest length from west to east is 435 kilometers.
If we take into account the depth of reservoirs, their area and volume of water, then the lake is commensurate with the Yellow, Baltic and Black Seas. By the same parameters, the Caspian surpasses the Tyrrhenian, Aegean, Adriatic and other seas.
The volume of water available in the Caspian Lake is 44% of the reserve of all lake waters of the planet.
Lake or sea?
Why is the Caspian lake called the sea? Is it really the impressive size of the reservoir that caused the assignment of such a “status”? More precisely, this was one of those reasons.
Others include a huge mass of water in the lake, the presence of a large wave during storm winds. All this is typical for real seas. It becomes clear why the Caspian Lake is called the sea.
But here one of the main conditions is not named, which must necessarily exist so that geographers can classify a reservoir as a sea. We are talking about the direct connection of the lake with the oceans. The Caspian does not meet this condition.
Where the Caspian Lake is located, a deepening in the earth's crust was formed several tens of thousands of years ago. Today it is filled with the waters of the Caspian Sea. According to scientists, at the end of the 20th century, the water level in the Caspian Sea was 28 meters below the level of the World Ocean. direct connection the waters of the lake and the ocean ceased to exist approximately 6 millennia ago. The conclusion from the above is that the Caspian Sea is a lake.
There is another feature that distinguishes the Caspian Sea from the sea - the salinity of the water in it is almost 3 times lower than the salinity of the World Ocean. The explanation for this is that about 130 large and small rivers carry fresh water to the Caspian Sea. The Volga makes the most significant contribution to this work - it is she who “gives” up to 80% of all water to the lake.
The river played another important role in the life of the Caspian Sea. It is she who will help find the answer to the question of why the Caspian Lake is called the sea. Now that many channels have been built by man, it has become a fact that the Volga connects the lake with the oceans.
The history of the lake
modern look and geographical position The Caspian lake is caused by continuous processes occurring on the surface of the Earth and in its bowels. There were times when the Caspian was connected with the Sea of Azov, and through it with the Mediterranean and Black. That is, tens of thousands of years ago, the Caspian Lake was part of the World Ocean.
As a result of the processes associated with the uplift and lowering of the earth's crust, mountains appeared on the site of the modern Caucasus. They isolated a body of water that was part of a vast ancient ocean. More than one tens of thousands of years passed before the basins of the Black and Caspian Seas separated. But for a long time, the connection between their waters was carried out through the strait, which was on the site of the Kumo-Manych depression.
Periodically, the narrow strait was either drained or refilled with water. This was due to fluctuations in the level of the oceans and changes in the appearance of the land.
In a word, the origin of the Caspian Lake is closely connected with common history formation of the earth's surface.
Own modern name the lake received because of the tribes of the Caspians, who inhabited the eastern parts of the Caucasus and the steppe zones of the Caspian territories. Over the entire history of its existence, the lake had 70 different names.
Territorial division of the lake-sea
The depth of the Caspian Lake in its different places is very different. Based on this, the entire water area of the lake-sea was conditionally divided into three parts: the Northern Caspian, the Middle and the Southern.
Shallow is Northern part lakes. Average depth of these places is 4.4 meters. The highest indicator is a mark of 27 meters. And on 20% of the entire area of the Northern Caspian, the depth is only about a meter. It is clear that this part of the lake is of little use for navigation.
The Middle Caspian has the greatest depth of 788 meters. The deep part occupies lakes. The average depth here is 345 meters, and the greatest is 1026 meters.
Seasonal changes at sea
Due to the large length of the reservoir from north to south climatic conditions on the coast of the lake are not the same. It also depends on seasonal changes in areas adjacent to water bodies.
In winter, on the southern coast of the lake in Iran, the water temperature does not drop below 13 degrees. During the same period, in the northern part of the lake off the coast of Russia, the water temperature does not exceed 0 degrees. The Northern Caspian is covered with ice during 2-3 months of the year.
In summer, almost everywhere the Caspian Lake warms up to 25-30 degrees. warm water, excellent sandy beaches, sunny weather create excellent conditions for people to relax.
Caspian on the political map of the world
Five states are located on the shores of the Caspian Lake - Russia, Iran, Azerbaijan, Kazakhstan and Turkmenistan.
The territory of Russia includes the western regions of the Northern and Middle Caspian. Iran is located on the southern shores of the sea, it owns 15% of the entire length of the coastline. The eastern coastline is shared by Kazakhstan and Turkmenistan. Azerbaijan is located in the southwestern territories of the Caspian Sea.
The issue of dividing the water area of the lake between the Caspian states has been the most acute for many years. The heads of the five states are trying to find a solution that would satisfy the needs and requirements of everyone.
The natural wealth of the lake
Caspian from ancient times for local residents served as a waterway.
The lake is famous for its valuable species of fish, in particular sturgeon. Their reserves account for up to 80% of the world's resources. The issue of conservation of the sturgeon population has international importance, it is decided at the level of the government of the Caspian states.
The Caspian seal is another mystery of the unique sea-lake. Scientists have not yet fully unraveled the mystery of the appearance of this animal in the waters of the Caspian Sea, as well as other species of animals of northern latitudes.
In total, 1809 species live in the Caspian Sea various groups animals. There are 728 species of plants. Most of them are the "indigenous inhabitants" of the lake. But there is a small group of plants that were deliberately brought here by man.
Of the minerals, the main wealth of the Caspian is oil and gas. Some information sources compare the oil reserves of the Caspian Lake fields with Kuwait. Industrial marine mining of black gold has been carried out on the lake since the end of the 19th century. The first well appeared on the Apsheron shelf in 1820.
Today, the governments unanimously believe that the region cannot be considered only as a source of oil and gas, while leaving the Caspian ecology unattended.
In addition to oil fields, there are deposits of salt, stone, limestone, clay and sand on the territory of the Caspian Sea. Their extraction also could not but affect the ecological situation of the region.
Sea level fluctuations
The water level in the Caspian Lake is not constant. This is evidenced by evidence relating to the IV century BC. The ancient Greeks, who explored the sea, discovered a large bay at the confluence of the Volga. The existence of a shallow strait between the Caspian and the Sea of Azov was also discovered by them.
There are other data on the water level in the Caspian Lake. The facts show that the level was much lower than it is now. Ancient evidence is architectural structures found on seabed. The buildings date back to the 7th-13th centuries. Now the depth of their flooding is from 2 to 7 meters.
In 1930, the water level in the lake began to decline catastrophically. The process went on for almost fifty years. This caused great concern among people, since all the economic activities of the Caspian region are adapted to the previously established water level.
Since 1978 the level has started to rise again. Today it has become more than 2 meters taller. This is also an undesirable phenomenon for people living on the coast of the lake-sea.
Climate change is said to be the main reason for fluctuations in the lake. This entails an increase in the volume of river water entering the Caspian, the amount of precipitation, and a decrease in the intensity of water evaporation.
However, it cannot be said that this is the only opinion that explains the fluctuations in the water level in the Caspian Lake. There are others, no less plausible.
Human activities and environmental issues
The area of the catchment basin of the Caspian Lake is 10 times larger than the surface of the water area of the reservoir itself. Therefore, all the changes taking place in such a vast territory in one way or another affect the ecology of the Caspian Sea.
Human activity plays an important role in changing the ecological situation in the area of the Caspian Lake. For example, pollution of a reservoir with harmful and hazardous substances occurs along with the influx of fresh water. It is directly related to industrial production, mining and other economic activity people in the watershed.
The state of the environment of the Caspian Sea and adjacent territories is of general concern to the governments of the countries located here. Therefore, the discussion of measures aimed at preserving unique lake, its flora and fauna, has become traditional.
Each state has an understanding that only through joint efforts can the ecology of the Caspian Sea be improved.
