The Caspian Sea is inland and located in a vast continental depression on the border of Europe and Asia. The Caspian Sea has no connection with the ocean, which formally allows it to be called a lake, but it has all the features of the sea, since in past geological eras it had connections with the ocean.
The sea area is 386.4 thousand km2, the volume of water is 78 thousand m3.
The Caspian Sea has a vast drainage basin, with an area of about 3.5 million km2. The nature of the landscapes, climatic conditions and types of rivers are different. Despite its vastness, only 62.6% of its area is in waste areas; about 26.1% - for non-drainage. The area of the Caspian Sea itself is 11.3%. 130 rivers flow into it, but almost all of them are located in the north and west (and the eastern coast does not have a single river reaching the sea). The largest river in the Caspian basin is the Volga, which provides 78% of the river waters entering the sea (it should be noted that more than 25% of the Russian economy is located in the basin of this river, and this undoubtedly determines many other features of the waters of the Caspian Sea), as well as the Kura River , Zhaiyk (Ural), Terek, Sulak, Samur.
Physiographically and by nature, the sea is divided into three parts: northern, middle and southern. The conventional border between the northern and middle parts runs along the line Chechen Island–Cape Tyub-Karagan, and between the middle and southern parts along the line Zhiloy Island–Cape Kuuli.
The shelf of the Caspian Sea is on average limited to depths of about 100 m. The continental slope, which begins below the shelf edge, ends in the middle part at approximately 500–600 m depths, in the southern part, where it is very steep, at 700–750 m.
The northern part of the sea is shallow, its average depth is 5–6 m, the maximum depths of 15–20 m are located on the border with the middle part of the sea. The bottom topography is complicated by the presence of banks, islands, and grooves.
The middle part of the sea is an isolated basin, the region of maximum depths of which - Derbent - is shifted to the western shore. The average depth of this part of the sea is 190 m, the greatest is 788 m.
The southern part of the sea is separated from the middle by the Absheron threshold, which is a continuation. The depths above this underwater ridge do not exceed 180 m. The deepest part of the South Caspian depression with a maximum sea depth of 1025 m is located east of the Kura delta. Several underwater ridges up to 500 m high rise above the bottom of the basin.
The shores of the Caspian Sea are diverse. In the northern part of the sea they are quite indented. Here are the Kizlyarsky, Agrakhansky, Mangyshlaksky bays and many shallow bays. Notable peninsulas: Agrakhansky, Buzachi, Tyub-Karagan, Mangyshlak. Large islands in the northern part of the sea are Tyuleniy and Kulaly. In the deltas of the Volga and Ural rivers, the coastline is complicated by many islands and channels, often changing their position. Many small islands and banks are located on other parts of the coastline.
The middle part of the sea has a relatively flat coastline. The Absheron Peninsula is located on the western coast, on the border with the southern part of the sea. To the east of it there are islands and banks of the Absheron archipelago, of which the largest island is Zhiloy. The eastern coast of the Middle Caspian is more indented; the Kazakh Gulf with Kenderli Bay and several capes stand out here. The largest bay of this coast is.
South of the Absheron Peninsula are the islands of the Baku archipelago. The origin of these islands, as well as some banks off the eastern coast of the southern part of the sea, is associated with the activity of underwater mud volcanoes lying on the bottom of the sea. On the eastern shore there are large bays of Turkmenbashi and Turkmensky, and near it the island of Ogurchinsky.
One of the most striking phenomena of the Caspian Sea is the periodic variability of its level. In historical times, the Caspian Sea had a level lower than the World Ocean. Fluctuations in the level of the Caspian Sea are so great that for more than a century they have attracted the attention of not only scientists. Its peculiarity is that in the memory of mankind its level has always been below the level of the World Ocean. Since the beginning of instrumental observations (since 1830) of sea level, the amplitude of its fluctuations has been almost 4 m, from –25.3 m in the eighties of the 19th century. to –29 m in 1977. In the last century, the level of the Caspian Sea changed significantly twice. In 1929 it stood at about -26 m, and since it had been close to this level for almost a century, this level position was considered to be a long-term or secular average. In 1930 the level began to decline rapidly. By 1941 it had dropped by almost 2 m. This led to the drying out of vast coastal areas of the bottom. The decrease in level, with slight fluctuations (short-term slight rises in level in 1946–1948 and 1956–1958), continued until 1977 and reached a level of –29.02 m, i.e. the level reached its lowest position in history the last 200 years.
In 1978, contrary to all forecasts, sea level began to rise. As of 1994, the level of the Caspian Sea was at –26.5 m, that is, over 16 years the level rose by more than 2 m. The rate of this rise is 15 cm per year. The level increase in some years was higher, and in 1991 it reached 39 cm.
The general fluctuations in the level of the Caspian Sea are superimposed by its seasonal changes, the long-term average of which reaches 40 cm, as well as surge phenomena. The latter are especially pronounced in the Northern Caspian Sea. The northwestern coast is characterized by large surges created by prevailing storms from the eastern and southeastern directions, especially in the cold season. A number of large (more than 1.5–3 m) surges have been observed here over the past decades. A particularly large surge with catastrophic consequences was noted in 1952. Fluctuations in the level of the Caspian Sea cause great damage to the states surrounding its waters.
Climate. The Caspian Sea is located in temperate and subtropical climates. Climatic conditions change in the meridional direction, since the sea stretches from north to south for almost 1200 km.
Various circulation systems interact in the Caspian region, however, winds from eastern directions predominate throughout the year (influence of the Asian High). The position at fairly low latitudes provides a positive balance of heat influx, so the Caspian Sea serves as a source of heat and moisture for passing people most of the year. The average annual temperature in the northern part of the sea is 8–10°C, in the middle - 11–14°C, in the southern part - 15–17°C. However, in the northernmost areas of the sea, the average January temperature is from –7 to –10°C, and the minimum during invasions is up to –30°C, which determines the formation of ice cover. In summer, rather high temperatures dominate over the entire region under consideration - 24–26°C. Thus, the Northern Caspian is subject to the most dramatic temperature fluctuations.
The Caspian Sea is characterized by a very small amount of precipitation per year - only 180 mm, with most of it falling during the cold season of the year (from October to March). However, the Northern Caspian differs in this respect from the rest of the basin: here the average annual precipitation is lower (for the western part only 137 mm), and the seasonal distribution is more uniform (10–18 mm per month). In general, we can talk about proximity to arid ones.
Water temperature. The distinctive features of the Caspian Sea (large differences in depths in different parts of the sea, nature, isolation) have a certain influence on the formation of temperature conditions. In the shallow Northern Caspian Sea, the entire water column can be considered homogeneous (the same applies to shallow bays located in other parts of the sea). In the Middle and Southern Caspian Sea, surface and deep masses can be distinguished, separated by a transition layer. In the Northern Caspian and in the surface layers of the Middle and Southern Caspian, water temperatures vary over a wide range. In winter, temperatures vary from north to south from less than 2 to 10°C, the water temperature off the west coast is 1–2°C higher than that on the east, in the open sea the temperature is higher than at the coasts: by 2–3°C in the middle part and by 3–4°С in the southern part of the sea. In winter, the distribution of temperature with depth is more uniform, which is facilitated by winter vertical circulation. During moderate and severe winters in the northern part of the sea and shallow bays of the east coast, the water temperature drops to freezing temperature.
In summer, the temperature varies in space from 20 to 28°C. The highest temperatures are observed in the southern part of the sea; temperatures are also quite high in the well-warmed shallow Northern Caspian Sea. The zone where the lowest temperatures occur is adjacent to the east coast. This is explained by the rise of cold deep waters to the surface. Temperatures are also relatively low in the poorly heated deep-sea central part. In open areas of the sea, at the end of May–beginning of June, the formation of a temperature jump layer begins, which is most clearly expressed in August. Most often it is located between 20 and 30 m in the middle part of the sea and 30 and 40 m in the southern part. In the middle part of the sea, due to the surge off the eastern coast, the shock layer rises close to the surface. In the bottom layers of the sea, the temperature throughout the year is about 4.5°C in the middle part and 5.8–5.9°C in the southern part.
Salinity. Salinity values are determined by factors such as river runoff, water dynamics, including mainly wind and gradient currents, the resulting water exchange between the western and eastern parts of the Northern Caspian and between the Northern and Middle Caspian, bottom topography, which determines the location of waters with different, mainly along isobath, evaporation, providing a deficit of fresh water and an influx of saltier water. These factors collectively influence seasonal differences in salinity.
The Northern Caspian Sea can be considered as a constant mixing of river and Caspian waters. The most active mixing occurs in the western part, where both river and Central Caspian waters directly flow. Horizontal salinity gradients can reach 1‰ per 1 km.
The eastern part of the Northern Caspian is characterized by a more uniform salinity field, since most of the river and sea (Middle Caspian) waters enter this area of the sea in a transformed form.
Based on the values of horizontal salinity gradients, it is possible to distinguish in the western part of the Northern Caspian the river-sea contact zone with water salinity from 2 to 10‰, in the eastern part from 2 to 6‰.
Significant vertical salinity gradients in the Northern Caspian are formed as a result of the interaction of river and sea waters, with runoff playing a decisive role. The strengthening of vertical stratification is also facilitated by the unequal thermal state of the water layers, since the temperature of the surface desalinated waters coming from the seashore in summer is 10–15°C higher than the bottom waters.
In the deep-sea depressions of the Middle and Southern Caspian Sea, fluctuations in salinity in the upper layer are 1–1.5‰. The largest difference between the maximum and minimum salinity was noted in the area of the Absheron threshold, where it is 1.6‰ in the surface layer and 2.1‰ at a 5 m horizon.
The decrease in salinity along the western coast of the South Caspian Sea in the 0–20 m layer is caused by the flow of the Kura River. The influence of the Kura runoff decreases with depth; at horizons of 40–70 m, the range of salinity fluctuations is no more than 1.1‰. Along the entire western coast to the Absheron Peninsula there is a strip of desalinated water with a salinity of 10–12.5‰, coming from the Northern Caspian Sea.
In addition, in the Southern Caspian Sea, an increase in salinity occurs when salted waters are carried out from bays and gulfs on the eastern shelf under the influence of southeastern winds. Subsequently, these waters are transferred to the Middle Caspian Sea.
In the deep layers of the Middle and Southern Caspian Sea, the salinity is about 13‰. In the central part of the Middle Caspian, such salinity is observed at horizons below 100 m, and in the deep-water part of the Southern Caspian, the upper boundary of waters with high salinity drops to 250 m. Obviously, in these parts of the sea, vertical mixing of waters is difficult.
Surface water circulation. Currents in the sea are mainly wind-driven. In the western part of the Northern Caspian, currents of the western and eastern quarters are most often observed, in the eastern part - southwestern and southern ones. Currents caused by the runoff of the Volga and Ural rivers can be traced only within the estuary coastal area. The prevailing current speeds are 10–15 cm/s; in open areas of the Northern Caspian Sea, maximum speeds are about 30 cm/s.
In the coastal areas of the middle and southern parts of the sea, in accordance with the wind directions, currents in the northwestern, northern, southeastern and southern directions are observed; near the east coast, currents in the eastern direction often occur. Along the western coast of the middle part of the sea, the most stable currents are southeastern and southern. Current speeds are on average about 20–40 cm/s, with maximum speeds reaching 50–80 cm/s. Other types of currents also play a significant role in the circulation of sea waters: gradient, seiche, and inertial.
Ice formation. The Northern Caspian Sea is covered with ice every year in November, the area of the frozen part of the water area depends on the severity of the winter: in severe winters the entire Northern Caspian Sea is covered with ice, in mild winters the ice remains within 2–3 meter isobath. The appearance of ice in the middle and southern parts of the sea occurs in December-January. On the eastern coast the ice is of local origin, on the western coast it is most often brought from the northern part of the sea. In severe winters, shallow bays freeze off the eastern coast of the middle part of the sea, shores and fast ice form off the coast, and on the western coast, drifting ice spreads to the Absheron Peninsula in abnormally cold winters. The disappearance of ice cover is observed in the second half of February–March.
Oxygen content. The spatial distribution of dissolved oxygen in the Caspian Sea has a number of patterns.
The central part of the waters of the Northern Caspian Sea is characterized by a fairly uniform distribution of oxygen. An increased oxygen content is found in the areas near the Volga River near the mouth, while a decreased oxygen content is found in the southwestern part of the Northern Caspian Sea.
In the Middle and Southern Caspian Sea, the highest concentrations of oxygen are confined to shallow coastal areas and pre-estuary coastal areas of rivers, with the exception of the most polluted areas of the sea (Baku Bay, Sumgait region, etc.).
In the deep-water areas of the Caspian Sea, the main pattern remains the same throughout all seasons - a decrease in oxygen concentration with depth.
Thanks to autumn-winter cooling, the density of the North Caspian Sea waters increases to a value at which it becomes possible for North Caspian waters with a high oxygen content to flow along the continental slope to significant depths of the Caspian Sea.
The seasonal distribution of oxygen is mainly associated with the annual course and seasonal relationship of production-destruction processes occurring in the sea.
In spring, the production of oxygen during photosynthesis very significantly covers the decrease in oxygen caused by a decrease in its solubility with increasing water temperature in spring.
In the areas of the estuary coastal areas of rivers feeding the Caspian Sea, in the spring there is a sharp increase in the relative oxygen content, which in turn is an integral indicator of the intensification of the photosynthesis process and characterizes the degree of productivity of the mixing zones of sea and river waters.
In summer, due to significant warming and activation of photosynthesis processes, the leading factors in the formation of the oxygen regime are photosynthetic processes in surface waters, and biochemical oxygen consumption by bottom sediments in bottom waters.
Due to the high temperature of the waters, the stratification of the water column, the large influx of organic matter and its intense oxidation, oxygen is quickly consumed with minimal entry into the lower layers of the sea, resulting in the formation of an oxygen deficiency zone in the Northern Caspian Sea. Intense photosynthesis in the open waters of the deep-sea regions of the Middle and Southern Caspian Sea covers the upper 25-meter layer, where oxygen saturation is more than 120%.
In autumn, in the well-aerated shallow areas of the Northern, Middle and Southern Caspian Sea, the formation of oxygen fields is determined by the processes of water cooling and the less active, but still ongoing process of photosynthesis. The oxygen content is increasing.
The spatial distribution of nutrients in the Caspian Sea reveals the following patterns:
- increased concentrations of nutrients are characteristic of areas near the mouth of the coastal rivers that feed the sea and shallow areas of the sea subject to active anthropogenic influence (Baku Bay, Turkmenbashi Bay, water areas adjacent to Makhachkala, Fort Shevchenko, etc.);
- The Northern Caspian, which is a vast mixing zone of river and sea waters, is characterized by significant spatial gradients in the distribution of nutrients;
- in the Middle Caspian, the nature of the circulation contributes to the rise of deep waters with a high content of nutrients into the overlying layers of the sea;
- in the deep-water regions of the Middle and Southern Caspian Sea, the vertical distribution of nutrients depends on the intensity of the convective mixing process, and their content increases with depth.
The dynamics of nutrient concentrations throughout the year in the Caspian Sea are influenced by such factors as seasonal fluctuations in nutrient runoff into the sea, the seasonal ratio of production-destructive processes, the intensity of exchange between soil and water mass, ice conditions in winter in the Northern Caspian, winter processes vertical circulation in deep sea areas.
In winter, a significant area of the Northern Caspian Sea is covered with ice, but biochemical processes actively develop in subglacial water and in ice. The ice of the Northern Caspian, being a kind of accumulator of nutrients, transforms these substances entering the sea from and from the atmosphere.
As a result of the winter vertical circulation of water in the deep-water regions of the Middle and Southern Caspian Sea during the cold season, the active layer of the sea is enriched with nutrients due to their supply from the underlying layers.
Spring for the waters of the Northern Caspian Sea is characterized by a minimum content of phosphates, nitrites and silicon, which is explained by the spring outbreak of phytoplankton development (silicon is actively consumed by diatoms). High concentrations of ammonium and nitrate nitrogen, characteristic of the waters of a large area of the Northern Caspian Sea during floods, are due to intensive washing by river waters.
In the spring season, in the area of water exchange between the Northern and Middle Caspian Seas in the subsurface layer, with a maximum oxygen content, the phosphate content is minimal, which, in turn, indicates the activation of the photosynthesis process in this layer.
In the Southern Caspian, the distribution of nutrients in spring is basically similar to their distribution in the Middle Caspian.
In summer, a redistribution of various forms of biogenic compounds is detected in the waters of the Northern Caspian Sea. Here the content of ammonium nitrogen and nitrates decreases significantly, while at the same time there is a slight increase in the concentrations of phosphates and nitrites and a rather significant increase in the concentration of silicon. In the Middle and Southern Caspian Sea, the concentration of phosphates has decreased due to their consumption during photosynthesis and the difficulty of water exchange with the deep-sea accumulation zone.
In autumn in the Caspian Sea, due to the cessation of activity of some types of phytoplankton, the content of phosphates and nitrates increases, and the concentration of silicon decreases, as there is an autumn outbreak of the development of diatoms.
Oil has been extracted on the Caspian Sea shelf for more than 150 years.
Currently, large hydrocarbon reserves are being developed on the Russian shelf, the resources of which on the Dagestan shelf are estimated at 425 million tons in oil equivalent (of which 132 million tons of oil and 78 billion m3 of gas), on the shelf of the Northern Caspian Sea - at 1 billion tons of oil .
In total, about 2 billion tons of oil have already been produced in the Caspian Sea.
Losses of oil and its products during production, transportation and use reach 2% of the total volume.
The main sources of pollutants, including petroleum products, entering the Caspian Sea are removal with river runoff, discharge of untreated industrial and agricultural wastewater, municipal wastewater from cities and towns located on the coast, shipping, exploration and exploitation of oil and gas fields. located on the bottom of the sea, oil transportation by sea. Places where pollutants enter with river flow are 90% concentrated in the Northern Caspian, industrial ones are confined mainly to the area of the Absheron Peninsula, and increased oil pollution of the Southern Caspian is associated with oil production and oil exploration drilling, as well as with active volcanic activity (mud) in the area oil and gas bearing structures.
From the territory of Russia, about 55 thousand tons of petroleum products enter the Northern Caspian annually, including 35 thousand tons (65%) from the Volga River and 130 tons (2.5%) from the runoff of the Terek and Sulak rivers.
Thickening of the film on the water surface to 0.01 mm disrupts gas exchange processes and threatens the death of hydrobiota. The concentration of petroleum products is toxic to fish at 0.01 mg/l and to phytoplankton at 0.1 mg/l.
The development of oil and gas resources on the bottom of the Caspian Sea, the forecast reserves of which are estimated at 12–15 billion tons of standard fuel, will become the main factor in the anthropogenic load on the sea ecosystem in the coming decades.
Caspian autochthonous fauna. The total number of autochthons is 513 species or 43.8% of the entire fauna, which include herring, gobies, mollusks, etc.
Arctic species. The total number of the Arctic group is 14 species and subspecies, or only 1.2% of the entire Caspian fauna (mysids, sea cockroach, white fish, Caspian salmon, Caspian seal, etc.). The basis of the Arctic fauna are crustaceans (71.4%), which easily tolerate desalination and live at great depths of the Middle and Southern Caspian Sea (from 200 to 700 m), since the lowest water temperatures are maintained here throughout the year (4.9– 5.9°C).
Mediterranean species. These are 2 types of mollusks, needle fish, etc. At the beginning of the 20s of our century, the mollusk mytileaster entered here, later 2 types of shrimp (with mullet, during their acclimatization), 2 types of mullet and flounder. Some species entered the Caspian Sea after the opening of the Volga-Don Canal. Mediterranean species play a significant role in the food supply of fish in the Caspian Sea.
Freshwater fauna (228 species). This group includes anadromous and semi-anadromous fish (sturgeon, salmon, pike, catfish, carp, and also rotifers).
Marine species. These are ciliates (386 forms), 2 species of foraminifera. There are especially many endemics among higher crustaceans (31 species), gastropods (74 species and subspecies), bivalves (28 species and subspecies) and fish (63 species and subspecies). The abundance of endemics in the Caspian Sea makes it one of the most unique brackish bodies of water on the planet.
The Caspian Sea produces more than 80% of the world's sturgeon catches, the bulk of which occur in the Northern Caspian Sea.
To increase sturgeon catches, which sharply decreased during the years of falling sea levels, a set of measures is being implemented. Among them are a complete ban on sturgeon fishing in the sea and its regulation in rivers, and an increase in sturgeon factory farming.
The Caspian Sea is remarkable in that its western shore belongs to Europe, and its eastern shore is located in Asia. This is a huge body of salt water. It is called a sea, but, in fact, it is a lake, since it has no connection with the World Ocean. Therefore, it can be considered the largest lake in the world.
The area of the water giant is 371 thousand square meters. km. As for the depth, the northern part of the sea is quite shallow, and the southern part is deep. The average depth is 208 meters, but it does not give any idea of the thickness of the water mass. The entire reservoir is divided into three parts. These are the Northern, Middle and Southern Caspian. The northern one is a sea shelf. It accounts for only 1% of the total volume of water. This part ends behind the Kizlyar Bay near the island of Chechen. The average depth in these places is 5-6 meters.
In the Middle Caspian, the seabed noticeably decreases, and the average depth reaches 190 meters. The maximum is 788 meters. This part of the sea contains 33% of the total volume of water. And the South Caspian is considered the deepest. It absorbs 66% of the total water mass. The maximum depth is noted in the South Caspian depression. She is equal 1025 meters and is considered the official maximum depth of the sea today. The Middle and Southern Caspian Seas are approximately equal in area and occupy a total of 75% of the area of the entire reservoir.
The maximum length is 1030 km, and the corresponding width is 435 km. The minimum width is 195 km. The average figure corresponds to 317 km. That is, the reservoir has an impressive size and is rightfully called a sea. The length of the coastline together with the islands reaches almost 7 thousand km. As for the water level, it is 28 meters below the level of the World Ocean.
The most interesting thing is that the level of the Caspian Sea is subject to cyclicity. The water rises and falls. Water level measurements have been carried out since 1837. According to experts, over the last thousand years the level has fluctuated within 15 meters. This is a very large number. And they associate it with geological and anthropogenic (human impact on the environment) processes. However, it has been noted that since the beginning of the 21st century, the level of the huge reservoir has been steadily rising.
The Caspian Sea is surrounded by 5 countries. These are Russia, Kazakhstan, Turkmenistan, Iran and Azerbaijan. Moreover, Kazakhstan has the longest coastline. Russia is in 2nd place. But the length of the coastline of Azerbaijan reaches only 800 km, but in this place there is the largest port in the Caspian Sea. This is, of course, Baku. The city is home to 2 million people, and the population of the entire Absheron Peninsula is 2.5 million people.
"Oil Rocks" - a city in the sea
These are 200 platforms with a total length of 350 kilometers
Notable is the oil workers' village, which is called " Oil Rocks". It is located 42 km east of Absheron in the sea and is a creation of human hands. All residential and industrial buildings are built on metal overpasses. People service drilling rigs that pump oil from the bowels of the earth. Naturally, there are no permanent residents in this village.
In addition to Baku, there are other large cities along the shores of the salty reservoir. At the southern tip is the Iranian city of Anzali with a population of 111 thousand people. This is the largest Iranian port on the Caspian Sea. Kazakhstan owns the city of Aktau with a population of 178 thousand people. And in the northern part, directly on the Ural River, is the city of Atyrau. It is inhabited by 183 thousand people.
The Russian city of Astrakhan also has the status of a seaside city, although it is 60 km from the coast and is located in the Volga River delta. This is a regional center with a population of more than 500 thousand people. Directly on the seashore there are such Russian cities as Makhachkala, Kaspiysk, Derbent. The latter is one of the oldest cities in the world. People have been living in this place for more than 5 thousand years.
Many rivers flow into the Caspian Sea. There are about 130 of them. The largest of them are the Volga, Terek, Ural, Kura, Atrek, Emba, Sulak. It is rivers, not precipitation, that feed the huge reservoir. They give him up to 95% of water per year. The basin of the reservoir is 3.626 million square meters. km. These are all rivers with their tributaries flowing into the Caspian Sea. The territory is huge, it includes Kara-Bogaz-Gol Bay.
It would be more correct to call this bay a lagoon. It means a shallow body of water separated from the sea by a sandbar or reefs. There is such a spit in the Caspian Sea. And the strait through which water flows from the sea is 200 km wide. True, people, with their restless and ill-considered activities, almost destroyed Kara-Bogaz-Gol. They fenced off the lagoon with a dam, and its level dropped sharply. But after 12 years the mistake was corrected and the strait was restored.
The Caspian Sea has always been shipping is developed. In the Middle Ages, merchants brought exotic spices and snow leopard skins from Persia to Rus' by sea. Nowadays, the reservoir connects the cities located on its banks. Ferry crossings are practiced. There is a water connection with the Black and Baltic Seas through rivers and canals.
Caspian Sea on the map
The body of water is also important from the point of view fisheries, because sturgeon live in large numbers there and provide caviar. But today the number of sturgeon has decreased significantly. Environmentalists propose to ban the fishing of this valuable fish until the population recovers. But this issue has not yet been resolved. The number of tuna, bream, and pike perch also decreased. Here you need to take into account the fact that poaching is highly developed at sea. The reason for this is the difficult economic situation of the region.
And, of course, I need to say a few words about oil. The extraction of “black gold” at sea began in 1873. The areas adjacent to Baku have become a real gold mine. There were more than 2 thousand wells here, and oil production and refining was carried out on an industrial scale. At the beginning of the 20th century it was the center of the international oil industry. In 1920, Azerbaijan was captured by the Bolsheviks. Oil wells and factories were requisitioned. The entire oil industry came under the control of the USSR. In 1941, Azerbaijan supplied 72% of all oil produced in the socialist state.
In 1994, the “Contract of the Century” was signed. He marked the beginning of the international development of the Baku oil fields. The main Baku-Tbilisi-Ceyhan pipeline allows Azerbaijani oil to flow directly to the Mediterranean port of Ceyhan. It was put into operation in 2006. Today, oil reserves are estimated at 12 trillion. US dollars.
Thus, it is clear that the Caspian Sea is one of the most important economic regions of the world. The political situation in the Caspian region is quite complicated. For a long time, there have been disputes about the maritime borders between Azerbaijan, Turkmenistan and Iran. There were many inconsistencies and disagreements, which negatively affected the development of the region.
This came to an end on August 12, 2018. On this day, the states of the “Caspian Five” signed the Convention on the Legal Status of the Caspian Sea. This document delimited the bottom and subsoil, and each of the five countries (Russia, Kazakhstan, Iran, Turkmenistan, Azerbaijan) received its share in the Caspian basin. Rules for navigation, fishing, scientific research, and pipeline laying were also approved. The boundaries of territorial waters received state status.
Yuri Syromyatnikov
CASPIAN SEA (Caspian), the largest enclosed body of water on the globe, an 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 its size, unique 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 a total area of less than 2 thousand km 2. In the northern part there are numerous small islands adjacent to the Volga delta; larger ones are Kulaly, Morskoy, Tyuleniy, Chechen. Off the western coast is the Absheron archipelago, to the south lie the islands of the Baku archipelago, off the eastern coast is the narrow island of Ogurchinsky, stretched from north to south.
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. The southern shores are low. 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 north-eastern 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 Greater Caucasus fold system. 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 of the modern depression of the Caspian Sea, but also the 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, the southwestern and southern coasts lie within the subtropics, and on the east coast a desert climate prevails. In winter, 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. The average wind speed is about 6 m/s, in the central regions of the 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. The lowest average monthly air temperatures -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. The open sea receives an average of 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 of the 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. The rivers of the western coast - Kura, Samur, Sulak, Terek, etc. - provide up to 10% of the flow. Another approximately 5% of fresh water is brought to the South Caspian by rivers on 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. The disturbance develops mainly in the northwest 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. The average wave height of greatest frequency is 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 southward 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 water in deep-sea depressions, the temperature remains 4.5-5.5 °C all year round 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 of waters. Water transparency varies widely from 0.2 m in the mouth areas of large rivers 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). The average boundary of 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. The average ice thickness is from 30 cm at the southern border 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 the modern name of the Caspian Sea comes from the ancient Caspian tribes who inhabited the coastal areas 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. In 1807, a new map of the Caspian Sea was published, compiled taking into account the latest inventories. In 1837, systematic instrumental observations of sea level fluctuations began in Baku. In 1847, the first complete description of the Kara-Bogaz-Gol Bay was made. 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. Soviet geologists I. made 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. M. Gubkin, D. V. and V. D. Golubyatnikov, 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. The Caspian Marine Research Center (CaspMNRC), created in 1995 by decree of the Government of the 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 Scientific Research Institute of Marine Fisheries and Oceanography (CaspNIRO), modern name since 1965]. CaspNIRH is developing the foundations for the conservation and rational use of biological resources of the 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. The natural resources of the Caspian Sea are 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. Large 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).
The Caspian Lake is one of the most unique places on Earth. It keeps many secrets related to the history of the development of our planet.
Position on physical map
The Caspian Sea is an internal, drainless salt lake. The geographical location of the Caspian Lake is the continent of Eurasia at the junction of parts of the world (Europe and Asia).
The length of the lake shoreline ranges 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 cut by the channels of the Volga and Ural. The river delta is rich in islands. The surface of the water in these areas is covered with thickets. Large areas of land are swampy.
The eastern coast of the Caspian Sea adjoins the On the shores of the lake there are significant deposits of limestone. The western and part of the eastern coasts are characterized by a winding coastline.
The Caspian Lake is represented on the map by its considerable size. The entire territory adjacent to it was called the Caspian region.
Some characteristics
The Caspian Lake has no equal on Earth in terms of its area and volume of water. 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 the reservoirs, their area and volume of water, then the lake is comparable to the Yellow, Baltic and Black Seas. According to the same parameters, the Caspian Sea surpasses the Tyrrhenian, Aegean, Adriatic and other seas.
The volume of water available in the Caspian Lake is 44% of the supply of all lake waters on the planet.
Lake or sea?
Why is the Caspian Lake called a sea? Was it really the impressive size of the reservoir that became the reason for assigning such a “status”? More precisely, this became one of these reasons.
Others include the huge mass of water in the lake, the presence of large waves during stormy winds. All this is typical for real seas. It becomes clear why the Caspian Lake is called a sea.
But one of the main conditions that must exist in order for geographers to classify a body of water as a sea is not mentioned here. We are talking about a direct connection between the lake and the World Ocean. It is precisely this condition that the Caspian Sea does not meet.
Where the Caspian Lake is located, a depression was formed in the earth’s crust 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. The direct connection between the waters of the lake and the ocean ceased to exist approximately 6 thousand years ago. The conclusion from the above is that the Caspian Sea is a lake.
There is one more feature that distinguishes the Caspian Sea from the sea - the salinity of its water 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 “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 a sea. Now that man has built many canals, it has become a fact that the Volga connects the lake with the World Ocean.
History of the lake
The modern appearance and geographical position of the Caspian Lake are determined by continuous processes occurring on the surface of the Earth and in its depths. There were times when the Caspian was connected to the Sea of Azov, and through it to the Mediterranean and Black Sea. That is, tens of thousands of years ago the Caspian Lake was part of the World Ocean.
As a result of processes associated with the rise and fall of the earth's crust, mountains appeared that are located on the site of the modern Caucasus. They isolated a body of water that was part of a huge ancient ocean. 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 Kuma-Manych depression.
Periodically, the narrow strait was either dried up or filled with water again. This happened due to fluctuations in the level of the World Ocean and changes in the appearance of the land.
In a word, the origin of the Caspian Lake is closely connected with the general history of the formation of the Earth's surface.
The lake received its modern name because of the Caspian tribes that inhabited the eastern parts of the Caucasus and the steppe zones of the Caspian territories. Throughout the history of its existence, the lake has had 70 different names.
Territorial division of the lake-sea
The depth of the Caspian Lake is very different in different places. Based on this, the entire water area of the lake-sea was conditionally divided into three parts: the Northern, Middle and Southern Caspian.
Shallow water is the northern part of the lake. The average depth of these places is 4.4 meters. The highest level is 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-water part is occupied by lakes. The average depth here is 345 meters, and the greatest is 1026 meters.
Seasonal changes at sea
Due to the large extent of the reservoir from north to south, the climatic conditions on the coast of the lake are not the same. Seasonal changes in the areas adjacent to the reservoir also depend on this.
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 for 2-3 months of the year.
In summer, almost everywhere the Caspian Lake warms up to 25-30 degrees. Warm water, excellent sandy beaches, and sunny weather create excellent conditions for people to relax.
Caspian Sea on the political map of the world
There are five states on the shores of the Caspian Lake - Russia, Iran, Azerbaijan, Kazakhstan and Turkmenistan.
The western regions of the Northern and Middle Caspian Sea belong to the territory of Russia. Iran is located on the southern shores of the sea, it owns 15% of the entire coastline. The eastern coastline is shared by Kazakhstan and Turkmenistan. Azerbaijan is located in the southwestern territories of the Caspian region.
The issue of dividing the lake’s waters between the Caspian states has been the most pressing for many years. The heads of five states are trying to find a solution that would satisfy everyone's needs and requirements.
Natural resources of the lake
Since ancient times, the Caspian Sea has served as a water transport route for local residents.
The lake is famous for valuable fish species, in particular sturgeon. Their reserves account for up to 80% of the world's resources. The issue of preserving the sturgeon population is of international importance; it is being resolved at the level of the government of the Caspian states.
The Caspian seal is another mystery of the unique sea-lake. Scientists have still not 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, the Caspian Sea is home to 1,809 species of different groups of animals. There are 728 species of plants. Most of them are “indigenous inhabitants” of the lake. But there is a small group of plants that were brought here intentionally by humans.
Of the mineral resources, the main wealth of the Caspian Sea is oil and gas. Some information sources compare the oil reserves of the Caspian Lake fields with those of Kuwait. Industrial sea mining of black gold has been carried out on the lake since the end of the 19th century. The first well appeared on the Absheron shelf in 1820.
Today, governments unanimously believe that the region cannot be viewed only as a source of oil and gas, while leaving the ecology of the Caspian Sea without attention.
In addition to oil fields, in the Caspian region there are deposits of salt, stone, limestone, clay and sand. Their production 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 dating back to the 4th 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 suggest that the level was much lower than what exists now. The proof is provided by ancient architectural structures discovered on the seabed. The buildings date back to the 7th-13th centuries. Now the depth of their flooding ranges from 2 to 7 meters.
In 1930, the water level in the lake began to decline catastrophically. The process continued for almost fifty years. This caused great concern among people, since all economic activity in the Caspian region is adapted to the previously established water level.
From 1978 the level began to rise again. Today he has become more than 2 meters higher. This is also an undesirable phenomenon for people living on the coast of the lake-sea.
The main reason affecting fluctuations in the lake is climate change. This entails an increase in the volume of river water entering the Caspian Sea, 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 fluctuation in water level in the Caspian Lake. There are others, no less plausible.
Human activities and environmental issues
The area of the Caspian Lake's drainage basin is 10 times larger than the surface of the reservoir itself. Therefore, all changes occurring 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 environmental situation in the Caspian Lake region. For example, pollution of a reservoir with harmful and dangerous substances occurs along with the influx of fresh water. This is directly related to industrial production, mining and other human activities 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 the 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.
The Caspian Sea is the largest lake on planet Earth. It is called the sea because of its size and bed, which is built like an ocean basin. The area is 371,000 square meters, the depth is 1025 m. The list of rivers flowing into the Caspian Sea includes 130 names. The largest of them are: Volga, Terek, Samur, Sulak, Ural and others.
Caspian Sea
It took 10 million years before the Caspian Sea was formed. The reason for its formation is that the Sarmatian Sea, having lost contact with the World Ocean, was divided into two bodies of water, which were called the Black and Caspian Seas. Between the latter and the World Ocean there are thousands of kilometers of waterless route. It is located at the junction of two continents - Asia and Europe. Its length in the north-south direction is 1200 km, west-east - 195-435 km. The Caspian Sea is an internal endorheic basin of Eurasia.
Near the Caspian Sea, the water level is below the level of the World Ocean, and it is also subject to fluctuations. According to scientists, this is due to many factors: anthropogenic, geological, climatic. Currently, the average water level reaches 28 m.
The river network and wastewater are unevenly distributed along the coast. A few rivers flow into part of the sea from the northern side: Volga, Terek, Ural. From the west - Samur, Sulak, Kura. The east coast is characterized by the absence of permanent watercourses. Differences in space in the flow of water that rivers bring to the Caspian Sea are an important geographical feature of this reservoir.
Volga
This river is one of the largest in Europe. In Russia it ranks sixth in size. In terms of drainage area, it is second only to Siberian rivers flowing into the Caspian Sea, such as the Ob, Lena, Yenisei, and Irtysh. The source from which the Volga begins is taken to be a spring near the village of Volgoverkhovye, Tver Region, on the Valdai Hills. Now at the source there is a chapel that attracts the attention of tourists who are proud to step over the very beginning of the mighty Volga.
A small fast stream gradually gains strength and becomes a huge river. Its length is 3690 km. The source is 225 m above sea level. Among the rivers flowing into the Caspian Sea, the largest is the Volga. Its path runs through many regions of our country: Tver, Moscow, Nizhny Novgorod, Volgograd and others. The territories through which it flows are Tatarstan, Chuvashia, Kalmykia and Mari El. The Volga is the location of millionaire cities - Nizhny Novgorod, Samara, Kazan, Volgograd.
Volga Delta
The main channel of the river is divided into channels. A certain shape of the mouth is formed. It's called delta. Its beginning is the place where the Buzan branch separates from the Volga river bed. The delta is located 46 km north of the city of Astrakhan. It includes channels, branches, and small rivers. There are several main branches, but only Akhtuba is navigable. Among all the rivers of Europe, the Volga has the largest delta, which is a rich fishing region in this basin.
It lies 28 m lower than ocean level. The mouth of the Volga is the location of the southernmost Volga city of Astrakhan, which in the distant past was the capital of the Tatar Khanate. Later, at the beginning of the 18th century (1717), Peter 1 gave the city the status of “capital of the Astrakhan province.” During his reign, the city's main attraction, the Assumption Cathedral, was built. Its Kremlin is made of white stone brought from the capital of the Golden Horde, Saraya. The mouth is divided by branches, the largest of which are: Bolda, Bakhtemir, Buzan. Astrakhan is a southern city located on 11 islands. Today it is a city of shipbuilders, sailors and fishermen.
The Volga currently needs protection. For this purpose, a reserve was established in the place where the river flows into the sea. The delta of the Volga, the largest river flowing into the Caspian Sea, is replete with unique flora and fauna: sturgeon, lotuses, pelicans, flamingos and others. Immediately after the revolution of 1917, a law was passed on their protection by the state as part of the Astrakhan Nature Reserve.
Sulak River
It is located in Dagestan and flows through its territory. It is fed by the waters of melted snow that flow from the mountains, as well as by tributaries: Maly Sulak, Chvakhun-bak, Akh-su. Water also enters Sulak through a canal from the Aksai and Aktash rivers.
The source is formed by the confluence of two rivers that originate in the basins: Didoiskaya and Tushinskaya. The length of the Sulak River is 144 km. Its pool has a fairly large area - 15,200 square meters. It flows through a canyon with the same name as a river, then through the Akhetlinsky gorge and finally reaches the plane. Rounding the Agrakhan Bay from the south, Sulak flows into the sea.
The river provides Kaspiysk and Makhachkala with drinking water, and is home to hydroelectric power stations, the urban-type settlements of Sulak and Dubki, and the small town of Kizilyurt.
Samur
The river received this name not by chance. The name translated from the Caucasian language (one of them) means “middle”. Indeed, the waterway along the Samur River marks the border between the states of Russia and Azerbaijan.
The sources of the river are glaciers and springs originating in the spurs of the Caucasus Range on the northeastern side, not far from Guton Mountain. The height above sea level is 3200 m. Samur has a length of 213 km. The height at the headwaters and the mouth differs by three kilometers. The drainage basin has an area of almost five thousand square meters.
The places where the river flows are narrow gorges located between high mountains made of clayey shales and sandstones, which is why the water here is muddy. The Samur basin has 65 rivers. Their length reaches 10 km or more.
Samur: valley and its description
The valley of this river in Dagestan is the most densely populated area. Near the mouth is Derbent, the oldest city in the world. The banks of the Samur River are home to twenty or more species of relict flora. Endemic, endangered and rare species listed in the Red Book grow here.
In the river delta there is a relict forest, which is the only one in Russia. The liana forest is a fairy tale. Huge trees of the rarest and most common species grow here, intertwined with vines. The river is rich in valuable fish species: mullet, pike perch, pike, catfish and others.
Terek
The river received its name from the Karachay-Balkar peoples who lived along its banks. They called it “Terk Suu”, which means “swift water”. The Ingush and Chechens called it Lomeki - “mountain water”.
The beginning of the river is the territory of Georgia, the Zigla-Khokh glacier is a mountain located on the slope of the Caucasus ridge. It is located under glaciers all year round. One of them melts when sliding down. A small stream is formed, which is the source of the Terek. It is located at an altitude of 2713 m above sea level. The length of the river flowing into the Caspian Sea is 600 km. When it flows into the Caspian Sea, the Terek is divided into many branches, resulting in the formation of a vast delta, its area is 4000 square meters. In some places it is very swampy.
The riverbed in this place changed several times. The old branches have now been converted into canals. The middle of the last century (1957) was marked by the construction of the Kargaly hydroelectric complex. It is used to supply water to the canals.
How is the Terek replenished?
The river has a mixed supply, but for the upper reaches, water from melting glaciers plays an important role; they fill the river. In this regard, 70% of the flow occurs in spring and summer, that is, at this time the water level in the Terek is highest, and the lowest is in February. The river freezes if the winters are characterized by a harsh climate, but the ice cover is unstable.
The river is not clean and transparent. The turbidity of the water is high: 400-500 g/m3. Every year the Terek and its tributaries pollute the Caspian Sea, pouring into it from 9 to 26 million tons of various suspended matter. This is explained by the rocks that make up the shores, which are clayey.
Estuary Terek
The Sunzha is the largest tributary flowing into the Terek, the lower reaches of which are measured from this river. By this time, the Terek flows for a long time through the flat terrain, leaving the mountains located behind the Elkhotov Gate. The bottom here is made of sand and pebbles, the current slows down, and in some places stops altogether.
The mouth of the Terek River has an unusual appearance: the channel here is raised above the valley, in appearance it resembles a canal, which is fenced by a high embankment. The water level becomes higher than the land level. This phenomenon is due to natural causes. Since the Terek is a turbulent river, it brings sand and stones in large quantities from the Caucasus Range. Considering that the current in the lower reaches is weak, some of them settle here and do not reach the sea. For residents of this area, sediment is both a threat and a blessing. When they are washed away by water, floods of great destructive power occur, this is very bad. But in the absence of floods, the soils become fertile.
Ural River
In ancient times (until the second half of the 18th century) the river was called Yaik. It was renamed in the Russian way by decree of Catherine the Second in 1775. Just at this time, the Peasant War, the leader of which was Pugachev, was suppressed. The name has been preserved to this day in the Bashkir language, and is official in Kazakhstan. The Urals are the third longest in Europe; only the Volga and Danube are larger rivers.
The Urals originate in Russia, on the slope of the Round Hill of the Uraltau ridge. The source is a spring gushing out of the ground at an altitude of 637 m above sea level. At the beginning of its journey, the river flows in a north-south direction, but after encountering a plateau along the way, it makes a sharp turn and continues to flow in a north-west direction. However, beyond Orenburg its direction changes again to the southwest, which is considered the main one. Having overcome a winding path, the Urals flows into the Caspian Sea. The length of the river is 2428 km. The mouth is divided into branches and tends to become shallow.
The Ural is a river along which the natural water boundary between Europe and Asia passes, with the exception of the upper reaches. This is an inland European river, but its upper reaches east of the Ural Range are Asian territory.
The importance of the Caspian rivers
The rivers flowing into the Caspian Sea are of great importance. Their waters are used for human and animal consumption, domestic, agricultural and industrial needs. Hydroelectric power stations are built on rivers, the energy of which is in demand by people for various purposes. River basins are full of fish, algae, and shellfish. Even in ancient times, people chose river valleys for future settlements. And now cities and towns are being built on their banks. The rivers are plied by passenger and transport ships, performing important tasks for transporting passengers and cargo.
