This is how the Mediterranean Sea was formed, which then included the current Azov, Black and Caspian Seas. On the site of the modern Caspian, a huge Caspian lowland was formed, the surface of which was almost 30 meters below the water level in the World Ocean. When the next rise of land began to take place at the place of formation of the Caucasus Mountains, the Caspian Sea was finally cut off from the ocean, and in its place a closed drainless reservoir was formed, which today is considered the largest inland sea on the planet. However, some scientists call this sea a giant lake.
A feature of the Caspian Sea is the constant fluctuation of the level of salinity of its water. Even in different areas of this sea, the water has different salinity. This was the reason for the predominance of fish and crustaceans in the Caspian Sea, which more easily tolerate fluctuations in water salinity.
Since the Caspian is completely isolated from the ocean, its inhabitants are endermics, i.e. always live in its water area.
The fauna of the Caspian Sea can be conditionally divided into four groups.
The first group of animals includes the descendants of ancient organisms that inhabited Tethys about 70 million years ago. These animals include Caspian gobies (golovach, Knipovich, Berg, bubyr, pugolovka, Baer) and herring (Kessler, Brazhnikov, Volga, brazil, etc.), some mollusks and most crustaceans (long-sexed crayfish, orthemia crustacean, etc.). Some fish, mainly herring, periodically enter the rivers flowing into the Caspian to spawn, many never leave the sea. Gobies prefer to live in coastal waters, often found in estuaries.
The second group of animals of the Caspian Sea is represented by arctic species. penetrated into the Caspian Sea from the north in the postglacial period. These are such animals as the Caspian seal (Caspian seal), fish - Caspian trout, white salmon, nelma. Of the crustaceans, this group is represented by mysid crustaceans, similar to small shrimps, tiny sea cockroaches, and some others.
The third group of animals inhabiting the Caspian includes species that independently or with the help of humans migrated here from the Mediterranean Sea. These are molluscs mitisyaster and abra, crustaceans - amphipods, shrimp, Black Sea and Atlantic crabs and some types of fish: golden mullet (sharp nose), needle fish and Black Sea kalk (flounder).
And, finally, the fourth group - freshwater fish that penetrated into the Caspian Sea from fresh rivers and turned into marine or anadromous, i.e. periodically rising into the rivers. Some of the typically freshwater fish also occasionally enter the Caspian. Among the fish of the fourth group are catfish, pike perch, barbel, red-lipped asp, Caspian fish, Russian and Persian sturgeon, beluga, stellate sturgeon. It should be noted that the Caspian Sea basin is the main habitat of sturgeons on the planet. Almost 80% of all sturgeons in the world live here. Barbels and fish are also valuable commercial fish.
As for sharks and other fish that are predatory and dangerous to humans, they do not live in the Caspian Sea-Lake.
One of the brightest reservoirs in the world is the Caspian Lake, which is located at the junction of Asia and Europe, and its shores and waters belong to 5 countries. The Caspian is attractive and inexpensive place for rest and treatment. Beautiful nature and the early opening of the swimming seasons make the rest on the Caspian coast more tempting.
The Caspian Lake is the largest of all lakes on the planet. It is often referred to as the Caspian Sea because of its impressive size and slightly salty water. It is located at the crossroads of Asia and Europe on the territory of 5 countries: Turkmenistan, Kazakhstan, Russian Federation Azerbaijan and Iran.
Despite the fact that the tourist infrastructure is inferior to the Black Sea in terms of development, the Caspian coast is in demand among tourists. This is facilitated by the rapid warming up of the reservoir due to its shallow depth, often the swimming season can begin at the end of April and end in October. The average water temperature in summer is 20-22 °C.
Benefits of resting on the Caspian Lake:
- clean sea sand;
- picturesque nature;
- nautical salubrious climate;
- mineral springs;
- healing mud;
- the presence of sanatoriums of various orientations;
- excellent fishing, especially in Astrakhan;
- active entertainment for every taste (diving, rafting, windsurfing, etc.);
- low cost of housing and entertainment with a developed infrastructure;
- being on the territory of the Russian Federation, which saves a lot of time on paperwork;
- great service;
- warm water for six months;
- the opportunity to save more than one thousand rubles on vacation, housing and food without denying yourself anything.
You can get to the Caspian Sea in various ways, but you should decide in which coastal city area to plan your vacation.
In the Russian Federation, there are several resort towns on the Caspian Lake:
Astrakhan is very popular among fishermen and lovers active rest associated with water, because there are many rivers in its vicinity, and the Caspian Lake is within easy reach - an hour by car.
Ancient city Derbent also enjoys a special love among tourists, because it is surrounded by attractions such as picturesque mountains, there are ancient fossils and legendary caves, overgrown with legends, and other interesting places to visit.
Such Dagestan resort towns as Izberbash, Kaspiysk, Makhachkala and Kalmyk Lagan are not deprived of attention either. Many tourists come to the Caspian Lake and stay in Azerbaijani cities (Baku, Lankaran, Sumgayit), Turkmen resorts Turkmentbashi and Avaza, Kazakh Aktau and Atyrau.
The origin of the Caspian lake and its names
Over 5 million years ago, the ancient sea was divided into several smaller ones, including the Caspian and the Black Sea. After this separation, the reservoirs repeatedly merged into one and split up, but approximately 1.75-2 million years ago, the reservoir was finally cut off from the waters of the World Ocean.
The modern name of the Caspian Lake is new. And according to one of the hypotheses, it came from the name of the Caspian tribe, who lived in its southwest in the first millennium BC. 
Throughout the entire period of existence, the Caspian Lake had more than 70 different names among various peoples of the tribes, among which:
- Abeskunskoye - by the name of the island and the city, which were located before they were flooded by a reservoir in the XIV century in a low plain formed by the Kura Kura River.
- Saray.
- Khazar or Mazenderan - Iranian name in honor of the province of the same name of the country, located on the coast, is used in Iran to this day.
- Dzhurdzhansky (Hirkansky) - the ancient Greek name of the reservoir, came from the region of Hyrkania and the city of Gorgan, now belonging to Iran.
- Derbent - by the name of the ancient coastal town of the same name in Dagestan.
- Sihai.
- Khvaliyskoye is an ancient Russian name, derived from the name of the Khvalis people, who lived in the north of the Caspian Sea.
Study and development of the Caspian lake
Finds on the western coast of Dagestan indicate that people lived in this territory already 2 million ago. At the confluence of the river Darvagchay (Dagestan) excavated remains in sites older than 600 thousand years. Excavations on the southern coast point to human habitation in this area 75 thousand years ago. All these studies show that the climate and living conditions were suitable for humans.
The founder of geography and the writer Hecateus of Miletus (VI-V century BC) in his work "Description of the Earth" described the Caspian Sea as the Hyrcanian Sea. In the 5th century BC, an ancient Greek historian was one of the first to suggest that the Caspian is not connected with other seas or the ocean, although scientists of those times argued that the reservoir was the northern bay of the World Ocean, which washed all known lands.
Aristotle in the 4th century BC was sure that the Hyrcanian reservoir was connected with the Black Sea by groundwater. The study of the relationship of the Caspian Sea with other large water bodies was carried out by Macedonian during his travels. In 323 BC, he sent the sailor and geographer Patroclus to explore the shores of the Caspian Sea. 
The navigator reached the Kara-Bogaz Bay and considered it a river that connects the Caspian Lake with the ocean. The well-known ancient Greek geographer and historian Strabo in one of his 17 chronicles (books) "Geography" imagined the Caspian Lake stretched in an east-west direction.
Arab scientists of the 9th-13th centuries made a significant contribution to the exploration of the Caspian Sea, writing in their works information about coastal cities and states, islands, flowing rivers and oil, which was produced in Azerbaijan (Baku).
The expansion of the geography of trade relations made it possible for European, Persian and Turkish travelers to receive a lot of information about the Caspian Sea. And the eminent Marco Polo (XIII century) also described a huge pond.
A very detailed, although sometimes erroneous, map of the Caspian Sea was compiled in the 17th century by the famous German scientist and traveler Adam Olearius. Peter I repeatedly traveled towards the Caspian Lake, and on the basis of the data provided by him, Russian hydrographers compiled very detailed maps of the Caspian Sea.
Since the 17th century, surveys of the Caspian Sea and its coastal environs have become systematic and versatile. Peter the Great in 1714 sent an exploratory expedition led by Bekovich-Cherkassky. A few years later, the research was continued by Verdun and Soimonov, a little later by Tokmachev, Voinovich and other scientists.
IN early XIX century, instrumental survey of the coast was carried out by I.F. Kolodkin, after several decades, geographical survey was carried out by an expedition led by N.A. For half a century, starting from 1866, regular hydrological and hydrobiological expeditions were carried out under the command of N.M. Knipovich.
During the first years of Soviet rule, the Caspian was actively explored by geologists, mainly in search of oil deposits, studying the water balance and fluctuations in the water height in the lake.
History of the Caspian Lake
The Caspian lake is located on the site of one of the giant reservoirs of antiquity. The origin of the Caspian Lake is inextricably linked with ancient sea Tetris, which more than 50-55 million years ago united the Pacific and Atlantic Oceans, being on the territory of the present Caspian, Azov, Black and mediterranean seas.
After long, complex tectonic movements, Tetris was first cut off from Pacific Ocean, and a little later, the Atlantic.
About 5-6.5 million years ago, a giant reservoir broke into small basins, which included the Caspian and the Black Sea.
After that, they repeatedly united and moved apart.
1.8-2 million years ago, the Caspian Sea was finally cut off from the waters of the World Ocean, and it is this time that is considered the beginning of its origin.
Throughout its history, the lake has repeatedly changed its coastline until it acquired its current form.
Physical and geographical characteristics of the Caspian Lake
The water surface of the lake is noticeably lower than the level of the World Ocean and is -27.5 ... -28.5 m. The area of the Caspian varies depending on the level and water and is in the range of 380-390 km2, the total volume is 73.7-74.1 km3 .
The Caspian is territorially divided into several parts with their own characteristics:
- North Caspian- 24% of the total area of \u200b\u200bthe reservoir falls on it. This part is shallow, and its average depth does not exceed 6 m, the maximum reaches 25 m, the volume of water is less than 1%.
- Middle Caspian- 36% of the total area of the lake falls on it. This part of the lake is a kind of basin with a maximum depth of almost 800 m, and an average depth of 190 m. It contains a third of the total volume of water.
- South Caspian- occupies 40% of the total area of the lake and it accounts for the deepest part of the reservoir. It contains 2/3 of the volume of all water - 66%. The average depth is 340 m, and the deepest depression is 1025 m.
The length of the coastline almost reaches the mark of 7 thousand km. The maximum length of the lake slightly exceeds 1 thousand km, and the widest point is 435 km. The minimum width is considered to be a segment of 195 km. The average width is considered to be 317 km.
Depth map of the Caspian lake The coasts vary greatly in their landscape. north coast gently sloping and low, around it there is a semi-desert in the lowland, and a desert on a hill. The southern coastline is partly low and partly mountainous and consists of the Elbrus ridge. The mountains of the Caucasus come close to the western part.
The eastern line of the coast is a calcareous plateau of a desert and semi-desert type. The outlines of the coast change greatly depending on the water level, which fluctuates periodically.
Climate
The water temperature of the Caspian varies greatly depending on the latitude. This amplitude is most noticeable in winter, when the water under the ice in the northern part has a temperature of 0.-0.5 °C above zero, while in the south at this time it is 10-11 °C.
According to averaged data, the temperature in the western part of the lake is up to 2 °C higher than in the eastern one, and at a distance from the shore it rises by 2-4 °C compared to the coastal zone. In summer, the water in the lake warms up to 23-29 °C, and in shallow water in the northern part it can reach 34-40 °C. Below 100 m, the temperature stabilizes and is 4-7 °C.
The Caspian Lake is located three climatic zones: continental (north of the reservoir), temperate (middle) and subtropical (South Caspian). in winter average temperature ranges from -8 to -11 °С in the north and up to +8 to +11 °С in the south of the lake.
In summer Northern part warms up to 24-25 °С with a positive mark, in the south the temperature rises to 26-27 °С. The highest temperature of +44 °С was noted in the east of the reservoir. 
The average amount of precipitation per year is about 200 mm. And on dry east coast falls at least 90-100 mm, in the south-west these figures can reach 1700 mm. The average annual wind speed is in the range of 3-8 m/s, mainly winds from the north prevail. In autumn and winter, their speed increases and can reach 35-39 m/s.
When the thermometer shows large minus values in the northern part of the lake, south coast trees and flowers bloom. IN winter time the surface of the lake is unstable, storm winds prevail. In winter, only the northern shallow water freezes; in severe winter frosts, the Northern Caspian and coastal waters of the Middle Caspian are covered with ice.
Flora and fauna
The flora of the Caspian Sea and its coastal environs is more than 720 species of plants. The lake is dominated mainly by algae (diatoms, brown, etc.), from angiosperms - rupee and zoster. Most of the vegetation of the Caspian Lake comes from the Neogene period, but some got into the reservoir on the bottoms of ships or consciously, with the help of man.
Among the animal representatives of the Caspian Sea and its environs, there are more than 1800 species, of which more than 400 are vertebrates, and more than 90 species are fish (sturgeon, carp, bream, mullet, beluga, etc.). Mammals are represented only by the Caspian seal, which is the smallest of the seal family and lives exclusively in the Caspian Lake.
The largest flock of sturgeon in the world lives in the lake, and a lot of pike perch, carp and roach live in the waters of the sea. Up to 80% of the total world sturgeon catch and more than 90% of the world black caviar fishery falls on the Caspian Lake.
The main route of bird migration between Europe and Asia passes over the Caspian Sea (in spring - in a southerly direction, and in autumn - in a northerly direction). During seasonal flights, over 11.5 million birds fly over the lake, about 5 million individuals remain for the winter. More than 850 species of animals live in the lake itself, of which almost 80 are vertebrates. Of the plants in the lake, there are more than 500 species.
Islands
There are more than 50 islands of large and medium format in the Caspian Lake with with total area about 350 sq. km. 
| The state that owns the island | Island name |
| Azerbaijan | Jasper |
| Oil Stones | |
| Pelican | |
| Zenbil | |
| Sengi Mugan | |
| Boyuk Zira | |
| Baku archipelago | |
| Kichik Zira | |
| Kurinsky | |
| Chilov | |
| Ignat dasha | |
| Inner Stone | |
| Khyarya Zira | |
| Kara Su | |
| Dash Zira | |
| Novoivanovskiy | |
| Chikil | |
| Kurinskaya Spit | |
| Gil | |
| Babury | |
| Iran | Ashur-Ada |
| Kazakhstan | Seal Islands |
| Average | |
| Zyudev | |
| Konevsky Oseryodok | |
| Someonok | |
| Babiy | |
| somovy | |
| Turkmenistan | Ogurchinsky |
| Big Zyudostinskiy | |
| Marine Ivan-Karaul | |
| Net Banks | |
| Small Zyudostinskiy | |
| Birdie | |
| Egg | |
| Small Setnoy | |
| Jumpers | |
| Sandy | |
| Bazaar | |
| Konevsky | |
| Zelenenky | |
| Marine Biryuchok | |
| Batkachny | |
| nordic | |
| Small Pearl | |
| Big Setnoy | |
| pancakes | |
| Upper Oseredok | |
| Khokhlatsky | |
| Zyudev | |
| Lower | |
| Small | |
| Likhachev | |
| seals | |
| Seventh | |
| Sea Chapura | |
| Chechen |
Inflowing rivers
More than 130 rivers flow into the Caspian, of which 9 have a delta-shaped mouth. 95% of water enters the Caspian from rivers. Most of them flow into the lake in the northern and western parts of the reservoir; there are no rivers flowing into the east.
The largest and most significant rivers of the Caspian basin:
Approximately 88% of the total runoff falls on such rivers as the Volga, Terek, Ural and Emba, which flow into the north of the Caspian. 7% of the flow falls on such rivers as the Kura, Sulak, Samur and other smaller ones that flow into the western part of the Caspian. About 5% of the flow of the rivers Sefidrud, Kheraz and Gorgan falls into the Iranian part of the reservoir.
Ecological state
The state of the Caspian Lake and adjacent territories inspires fear among environmentalists.
The main causes of environmental problems are related to man and his activities:
- extraction and transportation of oil and gas products;
- intake of pollutants with runoff waters of rivers;
- poaching;
- waste from coastal cities;
- rapid jumps in the water level in the Caspian due to the irrigation of lands with the waters of the flowing rivers and the use of hydroelectric power stations.
How the Caspian Lake is used
The Caspian lake has been actively used by man for many centuries.
Main directions of economic activity:
Recreational resources of the Caspian Lake
The climate and nature of the Caspian coast with its clean sandy beaches, healing mud and healing springs provide great potential and excellent conditions for sanatorium treatment and tourist holiday.
The development of the resort and tourism infrastructure although it is noticeably inferior to the similar industry of the Black Sea coast, it is actively expanding and improving the quality of service. The most noticeable surge in development in recent years has been noted in the Republic of Dagestan, Iran, Turkmenistan and Azerbaijan. 
Rest on the coast of the Caspian Sea in the Russian Federation and former countries LPG is notable for its low cost and, on average, in terms of quality in some places is inferior to that in the Black Sea, but in actively developing areas the level is quite high.
Popular recreation areas with developed infrastructure:
- Baku;
- Amburan;
- Makhachkala;
- Bilgah;
- Derbent.
- Dial;
- Lankaran;
- Nardaran.
The development of the Turkmen resort and tourism industry is hampered by an internal policy that isolates the state from the majority of tourists. And in Iran, mass recreation is difficult due to strict Sharia law.
There are 3 protected areas on the coast:
The Caspian Lake is located at the crossroads of Europe and Asia and is the largest lake in the world.
About the reservoir there are many interesting facts:
- It is larger than Japan, but smaller than Germany in area.
- In terms of depth, the Caspian is in third place, second only to Tanganyika and Baikal.
- Every 2.5 centuries a complete renewal of the waters takes place.
- On the Iranian coast, albino beluga is caught, whose caviar is the most expensive in the world. It has a white tint and is packaged in unusual jars made of real gold.
- The largest beluga weighed over 1200 kg and was caught in the 1920s. XX century on the Russian coast. In its dimensions, it is comparable to a large shark.
- Throughout the history of the lake, he had more than 70 different names.
- Scientists are still debating whether to consider the Caspian Lake a sea, justifying this by the fact that its area exceeds the size of some seas, and the bottom was created according to the oceanic type. But at the same time, the reservoir is drainless and does not connect with the ocean and other seas.
- The smallest length of the coastline of the five countries belongs to the Russian Federation.
- More than 80% of the waters enter the lake from the river. Volga.
The Caspian lake is rich in flora and fauna, it is distinguished by warm waters and a long swimming season. It is best known for its depth and size, oil, gas and sturgeon production, the reserves of which exceed those known throughout the world.
The lake is 95% supplied with runoff water to rivers. On its coast there are many resorts and sanatoriums, whose attractiveness can be assessed, and affordable prices.
Article formatting: Mila Fridan
Video about the Caspian Sea
Film about the Caspian Sea:
The Caspian Sea is one of the most amazing enclosed bodies of water on Earth.
Over the centuries, the sea has changed more than 70 names. The modern came from the Caspians - the tribes inhabiting the central and southeastern part of Transcaucasia 2 thousand years BC.
Geography of the Caspian Sea
The Caspian Sea is located at the junction of Europe with Asia and geographic location is divided into the South, North and Middle Caspian. The middle and northern part of the sea belongs to Russia, the southern part to Iran, the eastern part to Turkmenistan and Kazakhstan, and the southwestern part to Azerbaijan. For many years, the Caspian states have been dividing the Caspian water area among themselves, and quite sharply at that.
Lake or sea?
In fact, the Caspian Sea is the world's largest lake, but it has a number of marine features. These include: a large body of water, strong storms with high waves, high and low tides. But the Caspian has no natural connection with the World Ocean, which makes it impossible to call it a sea. At the same time, thanks to the Volga and artificially created channels, such a connection appeared. The salinity of the Caspian Sea is 3 times lower than the usual sea level, which does not allow classifying the reservoir as a sea.
There were times when the Caspian Sea was indeed part of the World Ocean. Several tens of thousands of years ago, the Caspian was connected to the Sea of Azov, and through it to the Black and Mediterranean. As a result of long-term processes occurring in the earth's crust, the Caucasus Mountains formed, which isolated the reservoir. Communication between the Caspian and Black Seas for a long time was carried out through the strait (Kumo-Manych depression) and gradually ceased.
Physical quantities
Area, volume, depth
The area, volume and depth of the Caspian Sea are not constant and directly depend on the water level. On average, the area of \u200b\u200bthe reservoir is 371,000 km², the volume is 78,648 km³ (44% of all world lake water reserves).
(Depth of the Caspian Sea in comparison with lakes Baikal and Tanganyika)
The average depth of the Caspian is 208 m, the northern part of the sea is considered the shallowest. The maximum depth is 1025 m, noted in the South Caspian depression. In depth, the Caspian is second only to Baikal and Tanganyika.
The length of the lake from north to south is about 1200 km, from west to east an average of 315 km. The length of the coastline is 6600 km, with islands - about 7 thousand km.
coast
Basically, the coast of the Caspian Sea is low-lying and smooth. In the northern part, it is heavily indented by the river channels of the Urals and the Volga. The swampy local shores are located very low. The eastern shores are adjacent to semi-desert zones and deserts, covered with limestone deposits. The most winding coasts are in the west in the region of the Apsheron Peninsula, and in the east - in the area of the Kazakh Gulf and Kara-Bogaz-Gol.
sea water temperature
(The temperature of the Caspian Sea in different time of the year)
The average water temperature in the Caspian in winter ranges from 0 °C in the northern part to +10 °C in the south. In the waters of Iran, the temperature does not fall below +13 °C. With the onset of cold weather, the shallow northern part of the lake is covered with ice, which lasts for 2-3 months. The thickness of the ice cover is 25-60 cm, at especially low temperatures it can reach 130 cm. In late autumn and winter, drifting ice floes can be observed in the north.
In summer, the average surface water temperature in the sea is + 24 °C. Most of the sea warms up to +25 °C ... +30 °C. Warm water and beautiful sandy, occasionally shell and pebble beaches create excellent conditions for a full-fledged beach holiday. In the eastern part of the Caspian Sea, near the city of Begdash, anomalously low water temperatures persist in the summer months.
Nature of the Caspian Sea
Islands, peninsulas, bays, rivers
The Caspian Sea includes about 50 large and medium-sized islands, the total area of which is 350 km². The largest of them are: Ashur-Ada, Garasu, Gum, Dash and Boyuk-Zira. The largest peninsulas are: Agrakhansky, Absheronsky, Buzachi, Mangyshlak, Miankale and Tyub-Karagan.
(Tyuleniy Island in the Caspian Sea, part of the Dagestan Reserve)
The largest bays of the Caspian include: Agrakhan, Kazakh, Kizlyar, Dead Kultuk and Mangyshlak. In the east is salt Lake Kara-Bogaz-Gol, previously a lagoon connected to the sea by a strait. In 1980, a dam was built on it, through which water from the Caspian goes to Kara-Bogaz-Gol, where it then evaporates.
130 rivers flow into the Caspian Sea, located mainly in its northern part. The largest of them: Volga, Terek, Sulak, Samur and Ural. The average annual runoff of the Volga is 220 km³. 9 rivers have a delta-shaped mouth.
Flora and fauna
About 450 species of phytoplankton live in the Caspian Sea, including algae, aquatic and flowering plants. Of the 400 species of invertebrates, worms, crustaceans and mollusks predominate. There are a lot of small shrimp in the sea, which is an object of fishing.
More than 120 species of fish live in the Caspian and the delta. Fishing objects are sprat (“Kilkin fleet”), catfish, pike, bream, pike perch, kutum, mullet, vobla, rudd, herring, white salmon, goby, grass carp, burbot, asp. Stocks of sturgeon and salmon are currently depleted, however, the sea is the largest supplier of black caviar in the world.
Fishing in the Caspian Sea is allowed all year round except for the period from the end of April to the end of June. On the coast there are many fishing bases with all amenities. Fishing in the Caspian is a great pleasure. In any part of it, including in large cities, the catch is unusually rich.
The lake is famous for its large variety of waterfowl. Geese, ducks, loons, gulls, waders, sea eagles, geese, swans and many others come to the Caspian during migration or nesting. The largest number birds - more than 600 thousand individuals are observed in the mouths of the Volga and the Urals, in the bays of Turkmenbashi and Kyzylagach. During the hunting season, a huge number of fishermen come here not only from Russia, but also from countries near and far abroad.
The only mammal lives in the Caspian Sea. This is the Caspian seal or seal. Until recently, the seals swam close to the beaches, everyone could admire the amazing animal with round black eyes, the seals behaved very friendly. Now the seal is on the verge of extinction.
Cities on the Caspian Sea
Baku is the largest city on the coast of the Caspian Sea. The population of one of the most beautiful cities in the world is over 2.5 million people. Baku is spread out on the most picturesque Absheron peninsula and is surrounded on three sides by the waters of the warm and oil-rich Caspian Sea. Less big cities: the capital of Dagestan is Makhachkala, Kazakh Aktau, Turkmen Turkmenbashi and Iranian Bender-Anzeli.
(Baku Bay, Baku - a city on the Caspian Sea)
Interesting Facts
Scientists are still arguing about whether to call a reservoir a sea or a lake. The level of the Caspian Sea is gradually decreasing. The Volga delivers most of the water to the Caspian. 90% of black caviar is mined in the Caspian Sea. Among them, the most expensive is Almas beluga caviar ($2,000 per 100 g).
Companies from 21 countries are participating in the development of oil fields in the Caspian Sea. According to Russian estimates, hydrocarbon reserves in the sea amount to 12 billion tons. American scientists claim that one fifth of the world's hydrocarbon reserves are concentrated in the depths of the Caspian Sea. This is more than the combined reserves of such oil-producing countries as Kuwait and Iraq.
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 it had connections with the ocean in past geological epochs.
Today Russia has access only to the Northern Caspian and the Dagestan part west coast Middle Caspian. The waters of the Caspian Sea wash the shores of such countries as Azerbaijan, Iran, Turkmenistan, Kazakhstan.
The area of the sea 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 landscapes, climatic conditions and types of rivers are different. Despite the vastness of the drainage basin, only 62.6% of its area falls on waste areas; about 26.1% - for drainless. 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 at all). largest river the Caspian basin - the Volga, which provides 78% of the river water 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 hydrochemical and other features of the waters of the Caspian Sea), as well as the Kura River, Zhaiyk (Ural), Terek, Sulak, Samur.
In physical and geographical terms and according to the nature of the underwater relief, the sea is divided into three parts: northern, middle and southern. The conditional boundary between the northern and middle parts runs along the line of Chechen Island–Cape Tyub-Karagan, between the middle and southern parts - along the line of Zhiloy Island–Cape Kuuli.
The shelf of the Caspian Sea, on average, is limited to depths of about 100 m. The continental slope, which begins below the edge of the shelf, ends in the middle part at about 500–600 m, 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 relief is complicated by the presence of banks, islands, furrows.
The middle part of the sea is a separate basin, the region of maximum depths of which - the Derbent depression - is shifted to the western coast. 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 part by the Apsheron threshold, which is a continuation of the Greater Caucasus. Depths above this underwater ridge do not exceed 180 m. The deepest part of the South Caspian basin 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.
coast The Caspian Sea are diverse. In the northern part of the sea, they are quite strongly indented. Here are the bays of Kizlyar, Agrakhan, Mangyshlak and many shallow bays. Notable peninsulas: Agrakhansky, Buzachi, Tyub-Karagan, Mangyshlak. Large islands in the northern part of the sea are Tyuleniy, Kulaly. In the deltas of the Volga and Ural rivers coastline complicated by many islets and ducts, 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. On the western coast, on the border with the southern part of the sea, the Apsheron Peninsula is located. To the east of it, islands and banks of the Apsheron archipelago stand out, of which the largest is Zhiloy Island. The eastern shore of the Middle Caspian is more indented, the Kazakh Bay stands out here with the Kenderli Bay and several capes. The largest bay of this coast is Kara-Bogaz-Gol.
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 at the bottom of the sea. On the eastern shore are the large bays of Turkmenbashi and Turkmensky, and near it is 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 lower level 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 the sea level, the amplitude of its fluctuations has been almost 4 m, from -25.3 m in the eighties of the XIX century. to -29 m in 1977. In the last century, the level of the Caspian Sea has changed significantly twice. In 1929 it stood at a mark of about -26 m, and since it had been close to this mark for almost a century, this position of the level was considered as a long-term or secular average. In 1930, the level began to decline rapidly. Already by 1941, it had dropped by almost 2 m. This led to the drying up of vast coastal areas of the bottom. The decrease in the level, with its small fluctuations (short-term insignificant rises in the level in 1946-1948 and 1956-1958), continued until 1977 and reached the mark of -29.02 m, i.e., the level took the lowest position for last 200 years.
In 1978, contrary to all forecasts, the sea level began to rise. As of 1994, the level of the Caspian Sea was at -26.5 m, that is, in 16 years the level has risen by more than 2 m. The rate of this rise is 15 cm per year. The level increment 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 average long-term of which reaches 40 cm, as well as surge phenomena. The latter are especially pronounced in the Northern Caspian. The northwestern coast is characterized by large surges created by the prevailing, especially in the cold season, storms of eastern and southeastern directions. Over the past decades, a number of large (more than 1.5–3 m) surges have been observed here. 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 water area.
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Climate. The Caspian Sea is located in the temperate and subtropical climatic zones. Climatic conditions change in the meridional direction, since the sea stretches for almost 1200 km from north to south.
In the Caspian region, various systems of atmospheric circulation interact, however, during the year, easterly winds prevail (the influence of the Asian maximum). The position at rather low latitudes provides a positive balance of heat inflow, so the Caspian Sea serves as a source of heat and moisture for passing air masses for most of the year. The average annual air temperature in the northern part of the sea is 8–10°С, in the middle part - 11–14°С, in the southern part – 15–17°С. However, in the northernmost parts of the sea, the average January temperature is from –7 to –10°C, and the minimum temperature during arctic air intrusions is up to –30°C, which determines the formation of the ice cover. In summer, rather high temperatures dominate over the entire region under consideration - 24–26°С. Thus, the Northern Caspian is subject to the most sharp temperature fluctuations.
The Caspian Sea is characterized by a very small amount of precipitation per year - only 180 mm, and most of it falls on 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 less (only 137 mm for the western part), and the distribution over the seasons is more even (10–18 mm per month). In general, we can talk about proximity climatic conditions to the arid ones.
Water temperature. The distinctive features of the Caspian Sea (great differences in depths in different parts of the sea, the nature of the bottom relief, isolation) have a certain influence on the formation of temperature conditions. In the shallow North Caspian, the entire water column can be considered as homogeneous (the same applies to shallow bays located in other parts of the sea). In the Middle and South Caspian, surface and deep masses separated by a transitional layer can be distinguished. In the Northern Caspian and in the surface layers of the Middle and Southern Caspian, the water temperature varies over a wide range. In winter, temperatures vary from north to south from less than 2 to 10°С, the water temperature near the western coast is 1–2°С higher than near the eastern one, in the open sea the temperature is higher than near the coasts: by 2–3°С in the middle part and by 3–4°С in the southern part of the sea. In winter, the temperature distribution is more uniform with depth, which is facilitated by the winter vertical circulation. During moderate and severe winters in the northern part of the sea and shallow bays on the east coast, the water temperature drops to freezing.
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 North Caspian. The zone of distribution of the lowest temperatures is adjacent to the east coast. This is due to the rise of cold deep waters to the surface. Temperatures are also relatively low in the poorly heated deep-water central part. In the open areas of the sea, in late May–early June, the formation of a temperature jump layer begins, which is most clearly expressed in August. Most often, it is located between the horizons of 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 near the eastern coast, the shock layer rises close to the surface. In the bottom layers of the sea, the temperature during the year is about 4.5°C in the middle part and 5.8–5.9°C in the south.
Salinity. Salinity values are determined by such factors 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, the bottom topography, which determines the location of waters with different salinity, mainly along the isobaths, evaporation, which ensures the shortage of fresh water and the inflow of more saline ones. These factors collectively affect the seasonal differences in salinity.
The Northern Caspian can be considered as a reservoir of constant mixing of river and Caspian waters. The most active mixing occurs in the western part, where both river and Central Caspian waters directly enter. In this case, 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.
According to the values of horizontal salinity gradients, in the western part of the Northern Caspian, a river-sea contact zone can be distinguished 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, the runoff plays a decisive role in this case. The intensification 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 coast in summer is 10–15°C higher than that of the bottom ones.
In the deep basins of the Middle and South Caspian, salinity fluctuations in the upper layer are 1–1.5‰. The largest difference between the maximum and minimum salinity was noted in the area of the Apsheron threshold, where it is 1.6‰ in the surface layer and 2.1‰ at the 5 m horizon.
The decrease in salinity along the western coast of the South Caspian in the 0–20 m layer is caused by the runoff of the Kura River. The influence of the Kura runoff decreases with depth; at the 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 stretches a strip of desalinated water with a salinity of 10–12.5‰ coming from the Northern Caspian.
In addition, salinity increases in the South Caspian due to the removal of saline waters from bays and inlets on the eastern shelf under the action of southeasterly winds. In the future, these waters are transferred to the Middle Caspian.
In the deep layers of the Middle and South Caspian, 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 part of the South Caspian, the upper boundary of waters with increased salinity drops to 250 m. Obviously, vertical mixing of waters is difficult in these parts of the sea.
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 - southwestern and southern. The currents caused by the runoff of the Volga and Ural rivers can be traced only within the estuarine coast. The prevailing current velocities are 10–15 cm/s; in the open areas of the Northern Caspian, the maximum velocities are about 30 cm/s.
In the coastal areas of the middle and southern parts of the sea, currents of the northwestern, northern, southeastern and southern directions are observed in accordance with the wind directions; currents often occur off the eastern coast east direction. Along the western coast of the middle part of the sea, the most stable currents are southeast and south. Current velocities are on average about 20–40 cm/s, the maximum ones reach 50–80 cm/s. Other types of currents also play a significant role in the circulation of sea waters: gradient, seiche, inertial ones.
Ice formation. The Northern Caspian is covered with ice annually in November, the area of the freezing part of the water area depends on the severity of the winter: in severe winters, the entire Northern Caspian is covered with ice, in soft ice it stays within the 2–3 meter isobath. The appearance of ice in the middle and southern parts of the sea falls on December-January. Near the eastern coast, ice is of local origin, near the western coast - 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, coasts and landfast ice form off the coast, and drift ice spreads to the Absheron Peninsula in abnormally cold winters off the western coast. The disappearance of the ice cover is observed in the second half of February–March.
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Oxygen content. The spatial distribution of dissolved oxygen in the Caspian Sea has a number of regularities. central part The water area of the Northern Caspian is characterized by a fairly uniform distribution of oxygen. An increased oxygen content is found in the areas of the pre-estuary seashore of the Volga River, a lower one - in the southwestern part of the Northern Caspian. In the Middle and South Caspian, the highest oxygen concentrations are confined to coastal shallow areas and pre-estuary seashores of rivers, with the exception of the most polluted areas of the sea (Baku Bay, Sumgait region, etc.). In summer, due to significant warming of water masses and activation of photosynthesis processes, the leading factors in the formation of the oxygen regime in surface waters are photosynthetic processes, in near-bottom waters - biochemical oxygen consumption by bottom sediments. Thanks to high temperature waters, stratification of the water column, a large influx of organic matter and its intense oxidation, oxygen is quickly consumed with its minimal entry into the lower layers of the sea, as a result of which an oxygen deficiency zone is formed in the Northern Caspian. Intensive photosynthesis in the open waters of the deep-water regions of the Middle and South Caspian covers the upper 25-meter layer, where oxygen saturation is more than 120%. |
- 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 cyclonic nature of the circulation contributes to the upwelling of deep waters with a high content of nutrients into the overlying layers of the sea;
– in the deep water areas of the Middle and South Caspian, the vertical distribution of nutrients depends on the intensity of the process of convective mixing, and their content increases with depth.
On the dynamics of concentrations nutrients during the year in the Caspian Sea are influenced by such factors as seasonal fluctuations in the biogenic runoff in the sea, the seasonal ratio of production-destruction processes, the intensity of exchange between soil and water mass, ice conditions in winter in the Northern Caspian, the processes of winter vertical circulation in deep water areas seas.
In winter, a significant area of the Northern Caspian is covered with ice, but biochemical processes are actively developing in the under-ice water and ice. The ice of the Northern Caspian, being a kind of accumulator of biogenic substances, transforms these substances that enter the sea with river runoff and from the atmosphere.
As a result of the winter vertical circulation of waters in the deep-sea regions of the Middle and Southern Caspian in 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 North Caspian 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 ammonium and nitrate nitrogen, which are characteristic of the waters of a large area of the Northern Caspian during floods, are due to intensive washing by the river waters of the Volga delta.
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IN spring time year in the area of water exchange between the North and Middle Caspian in the subsurface layer, with the maximum oxygen content, the content of phosphates is minimal, which, in turn, indicates the activation of the photosynthesis process in this layer.
In the South Caspian, the distribution of nutrients in spring is basically similar to their distribution in the Middle Caspian.
IN summer time in the waters of the Northern Caspian, a redistribution of various forms of biogenic compounds is found. Here, the content of ammonium nitrogen and nitrates significantly decreases, 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 South Caspian, the concentration of phosphates has decreased due to their consumption in the process of photosynthesis and the difficulty of water exchange with the deep water accumulation zone.
In autumn, in the Caspian Sea, due to the cessation of the activity of some types of phytoplankton, the content of phosphates and nitrates increases, and the concentration of silicon decreases, as an autumn outbreak of diatoms occurs.
For more than 150 years, oil has been mined on the shelf of the Caspian Sea oil.
Currently, large reserves of hydrocarbons are being developed on the Russian shelf, the resources of which on the Dagestan shelf are estimated at 425 million tons of oil equivalent (of which 132 million tons of oil and 78 billion m3 of gas), on the shelf of the Northern Caspian - 1 billion tons of oil .
In total, about 2 billion tons of oil have already been produced in the Caspian.
Losses of oil and products of its processing during extraction, transportation and use reach 2% of the total volume.
Main sources of income pollutants, including oil products, into the Caspian Sea - this is the removal with river runoff, the discharge of untreated industrial and agricultural effluents, domestic wastewater from cities and towns located on the coast, shipping, exploration and exploitation of oil and gas fields located at the bottom of the sea, transportation of oil by sea. 90% of pollutants with river runoff are concentrated in the Northern Caspian, industrial effluents are confined mainly to the area of the Apsheron Peninsula, and increased oil pollution of the Southern Caspian is associated with oil production and oil exploration drilling, as well as active volcanic activity (mud volcanism) in the zone of oil and gas bearing structures.
From the territory of Russia, about 55 thousand tons of oil products enter the Northern Caspian every year, including 35 thousand tons (65%) from the Volga River and 130 tons (2.5%) from the Terek and Sulak rivers.
The thickening of the film on the water surface up to 0.01 mm disrupts the processes of gas exchange and threatens the death of hydrobiota. Toxic for fish is the concentration of oil products 0.01 mg/l, for phytoplankton - 0.1 mg/l.
The development of oil and gas resources of the bottom of the Caspian Sea, the estimated reserves of which are estimated at 12–15 billion tons of standard fuel, will become the main factor in the anthropogenic load on the ecosystem of the sea in the coming decades.
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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 views. The total number of the Arctic group is 14 species and subspecies, or only 1.2% of the entire fauna of the Caspian (mysids, sea cockroach, white salmon, Caspian salmon, Caspian seal, etc.). The basis of the Arctic fauna is crustaceans (71.4%), which easily tolerate desalination and live at great depths of the Middle and Southern Caspian (from 200 to 700 m), since the most low temperatures water (4.9–5.9°С).
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Mediterranean views. These are 2 types of mollusks, needle-fish, etc. At the beginning of the 20s of our century, the mollusk mitilyastra penetrated here, later 2 types of shrimp (with mullets, during their acclimatization), 2 types of mullet and flounder. Some Mediterranean species entered the Caspian after the opening of the Volga-Don Canal. Mediterranean species play a significant role in the fish food base of the Caspian Sea.
freshwater fauna(228 species). This group includes anadromous and semi-anadromous fish (sturgeon, salmon, pike, catfish, cyprinids, as well as rotifers).
Marine views. These are ciliates (386 forms), 2 species of foraminifera. There are especially many endemics among higher crustaceans (31 species), gastropod molluscs (74 species and subspecies), bivalve mollusks (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 water bodies on the planet.
The Caspian Sea provides more than 80% of the world's sturgeon catch, most of which falls on the North Caspian.
To increase the catches of sturgeon, which dropped sharply during the years of sea level drop, a set of measures is being implemented. Among them - a complete ban on sturgeon fishing in the sea and its regulation in rivers, an increase in the scale of factory breeding of sturgeons.
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Caspian Sea - the largest lake on Earth, drainless, located at the junction of Europe and Asia, called the sea because of its size, and also because its bed is composed of oceanic-type earth's crust. The water in the Caspian is salty - from 0.05 ‰ near the mouth of the Volga to 11-13 ‰ in the southeast. The water level is subject to fluctuations, according to 2009 data it was 27.16 m below sea level. The area of the Caspian Sea is currently approximately 371,000 km², the maximum depth is 1025 m.
Geographical position
The Caspian Sea is located at the junction of two parts of the Eurasian continent - Europe and Asia. The length of the Caspian Sea from north to south is approximately 1200 kilometers (36°34 "-47°13" N), from west to east - from 195 to 435 kilometers, on average 310-320 kilometers (46°-56° v. d.). The Caspian Sea is conditionally divided according to physical and geographical conditions into 3 parts - the Northern Caspian, the Middle Caspian and the Southern Caspian. The conditional border between the North and Middle Caspian runs along the line of about. Chechnya - Cape Tyub-Karagansky, between the Middle and South Caspian - along the line of about. Residential - Cape Gan-Gulu. The area of the Northern, Middle and Southern Caspian is 25, 36, 39 percent respectively.
The length of the coastline of the Caspian Sea is estimated at about 6500-6700 kilometers, with islands - up to 7000 kilometers. The shores of the Caspian Sea in most of its territory are low-lying and smooth. In the northern part, the coastline is indented by water channels and islands of the Volga and Ural deltas, the shores are low and swampy, and the water surface is covered with thickets in many places. On east coast limestone coasts adjoining semi-deserts and deserts predominate. The most winding coasts are on the west coast in the area of the Apsheron Peninsula and on the east coast in the area of the Kazakh Gulf and Kara-Bogaz-Gol. The territory adjacent to the Caspian Sea is called the Caspian Sea.
Peninsulas of the Caspian Sea
Large peninsulas of the Caspian Sea:
- Agrakhan Peninsula
- The Absheron Peninsula, located on the western coast of the Caspian Sea in the territory of Azerbaijan, at the northeastern end of the Greater Caucasus, the cities of Baku and Sumgayit are located on its territory
- Buzachi
- Mangyshlak, located on the eastern coast of the Caspian Sea, on the territory of Kazakhstan, on its territory is the city of Aktau
- Miankale
- Tyub-Karagan
Islands of the Caspian Sea
There are about 50 large and medium-sized islands in the Caspian Sea with a total area of approximately 350 square kilometers. The largest islands:
- Ashur-Ada
- Garasu
- Boyuk Zira
- Zyanbil
- Cure Dashi
- Hara Zira
- Ogurchinsky
- Sengi-Mugan
- seals
- Seal Islands
- Chechen
- Chygyl
Bays of the Caspian Sea
Large bays of the Caspian Sea:
- Agrakhan bay
- Kizlyar Bay
- Dead Kultuk (former Komsomolets, former Tsesarevich Bay)
- Kaydak
- Mangyshlak
- Kazakh
- Kenderly
- Turkmenbashi (bay) (former Krasnovodsk)
- Turkmen (bay)
- Gyzylagach (former bay named after Kirov)
- Astrakhan (bay)
- Hasan-kuli
- Gyzlar
- Hyrcanus (former Astarabad)
- Anzali (former Pahlavi)
- Kara-Bogaz-Gol
Rivers flowing into the Caspian Sea- 130 rivers flow into the Caspian Sea, of which 9 rivers have a mouth in the form of a delta. The major rivers flowing into the Caspian Sea are the Volga, Terek, Sulak, Samur (Russia), Ural, Emba (Kazakhstan), Kura (Azerbaijan), Atrek (Turkmenistan), Sefidrud (Iran) and others. The largest river flowing into the Caspian Sea is the Volga, its average annual runoff is 215-224 cubic kilometers. The Volga, Ural, Terek, Sulak and Emba provide up to 88-90% of the annual runoff to the Caspian Sea.
Physiography
Area, depth, volume of water- The area and volume of water in the Caspian Sea varies significantly depending on fluctuations in water levels. At a water level of -26.75 m, the area is approximately 371,000 square kilometers, the volume of water is 78,648 cubic kilometers, which is approximately 44% of the world's lake water reserves. The maximum depth of the Caspian Sea is in the South Caspian depression, 1025 meters from its surface level. In terms of maximum depth, the Caspian Sea is second only to Baikal (1620 m) and Tanganyika (1435 m). The average depth of the Caspian Sea, calculated from the bathygraphic curve, is 208 meters. At the same time, the northern part of the Caspian Sea is shallow, its maximum depth does not exceed 25 meters, and the average depth is 4 meters.
Water level fluctuations- The water level in the Caspian Sea is subject to significant fluctuations. According to modern science, over the past three thousand years, the magnitude of the change in the water level of the Caspian Sea has reached 15 meters. According to archeology and written sources, it is fixed high level Caspian Sea at the beginning of the XIV century. Instrumental measurement of the level of the Caspian Sea and systematic observations of its fluctuations have been carried out since 1837, during this time the highest water level was recorded in 1882 (−25.2 m), the lowest - in 1977 (−29.0 m), from In 1978, the water level rose and in 1995 it reached -26.7 m, since 1996 there has been a downward trend again. Scientists associate the causes of changes in the water level of the Caspian Sea with climatic, geological and anthropogenic factors. But in 2001, the sea level began to rise again, and reached -26.3 m.
Water temperature- water temperature is subject to significant latitudinal changes, most pronounced in winter, when the temperature changes from 0-0.5 °C at the ice edge in the north of the sea to 10-11 °C in the south, that is, the water temperature difference is about 10 ° C. For shallow water areas with depths less than 25 m, the annual amplitude can reach 25-26 °C. On average, the water temperature near the western coast is 1-2 °C higher than that of the eastern coast, and in the open sea the water temperature is 2-4 °C higher than near the coasts.
Water composition- the salt composition of the waters of the closed Caspian Sea differs from that of the ocean. There are significant differences in the ratios of the concentrations of salt-forming ions, especially for the waters of areas under the direct influence of continental runoff. The process of metamorphization of sea waters under the influence of continental runoff leads to a decrease in the relative content of chlorides in the total amount of salts in sea waters, an increase in the relative amount of carbonates, sulfates, and calcium, which are the main components in the chemical composition of river waters. The most conservative ions are potassium, sodium, chloride and magnesium. The least conservative are calcium and bicarbonate ion. In the Caspian Sea, the content of calcium and magnesium cations is almost two times higher than in the Sea of Azov, and sulfate anion is three times higher.
Bottom relief- the relief of the northern part of the Caspian Sea is a shallow wavy plain with banks and accumulative islands, the average depth of the Northern Caspian is 4-8 meters, the maximum does not exceed 25 meters. The Mangyshlak threshold separates the Northern Caspian from the Middle. The Middle Caspian is quite deep, the depth of water in the Derbent depression reaches 788 meters. The Apsheron threshold separates the Middle and South Caspian. The South Caspian is considered deep water, the depth of water in the South Caspian depression reaches 1025 meters from the surface of the Caspian Sea. Shell sands are widespread on the Caspian shelf, deep-water areas are covered with silty sediments, and in some areas there is an outcrop of bedrock.
Climate- The climate of the Caspian Sea is continental in the northern part, temperate in the middle part and subtropical in the southern part. In winter, the average monthly air temperature varies from -8…-10 in the northern part to +8…+10 in the southern part, in summer - from +24…+25 in the northern part to +26…+27 in the southern part. The maximum temperature of +44 degrees was recorded on the east coast. The average annual rainfall is 200 millimeters, ranging from 90-100 millimeters in the arid eastern part to 1,700 millimeters off the southwestern subtropical coast. Evaporation of water from the surface of the Caspian Sea is about 1000 millimeters per year, the most intense evaporation in the area of the Absheron Peninsula and in the eastern part of the South Caspian is up to 1400 millimeters per year. The average annual wind speed is 3-7 meters per second, northerly winds prevail in the wind rose. In the autumn and winter months, the winds increase, the wind speed often reaches 35-40 meters per second. The most windy areas are the Apsheron Peninsula, the environs of Makhachkala and Derbent, where the highest wave 11 meters high was also recorded.
currents- The circulation of waters in the Caspian Sea is connected with the runoff and winds. Since most of the water flow falls on the Northern Caspian, northern currents predominate. An intense northern current carries water from the Northern Caspian along the western coast to the Absheron Peninsula, where the current is divided into two branches, one of which moves further along the western coast, the other goes to the Eastern Caspian.
Economic development of the Caspian Sea
Mining of oil and gas-Many oil and gas fields are being developed in the Caspian Sea. The proven oil resources in the Caspian Sea are about 10 billion tons, the total resources of oil and gas condensate are estimated at 18-20 billion tons. Oil production in the Caspian Sea began in 1820, when the first oil well was drilled on the Absheron shelf near Baku. In the second half of the 19th century, oil production began on an industrial scale on the Absheron Peninsula, and then on other territories. In 1949, Oil Rocks for the first time began to extract oil from the bottom of the Caspian Sea. So, on August 24 of this year, the team of Mikhail Kaverochkin started drilling a well, which on November 7 of the same year gave the long-awaited oil. In addition to oil and gas production, salt, limestone, stone, sand, and clay are also mined on the coast of the Caspian Sea and the Caspian shelf.
Shipping- Shipping is developed in the Caspian Sea. On the Caspian Sea ferry crossings, in particular, Baku - Turkmenbashi, Baku - Aktau, Makhachkala - Aktau. The Caspian Sea has a navigable connection with Sea of Azov through the rivers Volga, Don and the Volga-Don Canal.
Fishing and seafood-fishing (sturgeon, bream, carp, pike perch, sprat), caviar production, as well as seal fishing. More than 90 percent of the world's sturgeon catch is carried out in the Caspian Sea. In addition to industrial production, illegal production of sturgeon and their caviar flourishes in the Caspian Sea.
Legal status of the Caspian Sea- after the collapse of the USSR, the division of the Caspian Sea has long been and still remains the subject of unsettled disagreements related to the division of the resources of the Caspian shelf - oil and gas, as well as biological resources. For a long time there were negotiations between littoral states on the status of the Caspian Sea - Azerbaijan, Kazakhstan and Turkmenistan insisted on dividing the Caspian along the median line, Iran - on dividing the Caspian along one fifth between all the Caspian states. The current legal regime of the Caspian is established by the Soviet-Iranian treaties of 1921 and 1940. These treaties provide for freedom of navigation throughout the sea, freedom of fishing, with the exception of ten-mile national fishing zones, and a ban on navigation in its waters of ships flying the flag of non-Caspian states. Negotiations on the legal status of the Caspian are currently ongoing.
