The Caspian Sea is the largest lake in the world, situated at the junction of Europe and Asia, called the sea due to the fact that its bed is made up of an oceanic crust. The Caspian Sea is a drainless lake, and the water in it 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, was 27,16 m below sea level.
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 about 1200 kilometers, from west to east - from 195 to 435 kilometers, an average of 310-320 kilometers. The Caspian Sea is conditionally divided into physical and geographical conditions on the 3 part - the Northern Caspian, the Middle Caspian and the Southern Caspian. The conditional boundary between the Northern and Middle Caspian passes along the line of Fr. Chechny - cape Tyub-Karagansky, between the Middle and South Caspian - along the line of Fr. Residential - Cape Gan-Gulu. The area of the Northern, Middle and Southern Caspian is 25, 36, 39 percent.
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 shoreline is cut by water channels and delta islands The Volga и The Urals, The banks are low and swampy, and the water surface is covered with thickets in many places. The eastern coast is dominated by limestone coasts adjacent to semi-deserts and deserts. The most meandering shores are on the west coast in the Absheron peninsula area 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 Prikaspiem.
The relief of the northern part of the Caspian Sea is a shallow undulating plain with banks and accumulative islands, the average depth of the Northern Caspian is 4-8 meters, the maximum does not exceed 25 meters. Mangyshlak threshold separates the Northern Caspian from the Middle. The Middle Caspian is deep enough, the depth of the water in the Derbent Basin reaches 788 meters. Absheron threshold divides the Middle and South Caspian. The Southern Caspian is considered deep-water, the depth of the water in the South Caspian basin reaches 1025 meters from the surface of the Caspian Sea. Shellfish sands are found on the Caspian shelf, deep-water areas are covered with muddy sediments, in some areas there is a bedrock outlet.Temperature conditions
The water temperature is subject to significant latitudinal changes, most pronounced in winter, when the temperature varies 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 areas with depths less than 25 m, the annual amplitude can reach 25-26 ° C. On average, the water temperature at the west coast is 1-2 ° C higher than in the east, and in the open sea the water temperature is higher than that of the coasts at 2-4 ° C.
The fauna of the Caspian Sea is represented by 1809 species, of which 415 refers to vertebrates. In the Caspian Sea 101 is registered as a fish species, most of the world's sturgeon stocks, as well as freshwater fish such as vobla, carp, and pike-perch are concentrated in it. The Caspian Sea is the habitat of such fish as carp, mullet, sprat, kutum, bream, salmon, perch, pike. In the Caspian Sea also lives a marine mammal - the Caspian seal.
The vegetation world of the Caspian Sea and its coast is represented by 728 species. Of the plants in the Caspian Sea, algae prevail - blue-green, diatom, red, brown, char, and others, from flowering - zoster and ruppy. By origin, the flora refers primarily to the Neogene age, but some plants were brought into the Caspian Sea by a person consciously or on the bottoms of ships.
In the Caspian Sea, many oil and gas fields are being developed. Proven oil resources in the Caspian Sea are about 10 billion tons, total oil and gas condensate resources 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. In the second half of the XIX century, oil production began in industrial volumes on the Apsheron Peninsula, and then in other territories. In addition to oil and gas production, salt, limestone, stone, sand, clay are also mined on the Caspian coast and the Caspian shelf.