Caspian Sea

The Caspian Sea is the largest enclosed body of water on Earth by area, variously classed as the world's largest lake or a full-fledged sea. It has a surface area of 371,000 square kilometers (143,244 sq mi) and a volume of 78,200 cubic kilometers (18,761 cu mi).It is an endorheic body of water (has no outflows), and lies between the southern areas of the Russian Federation and northern Iran. It has a maximum depth of about 1025 meters (3,363 ft).
It was perceived as a sea by its ancient coastal inhabitants because it is salty and seemed boundless. It has a salinity of approximately 1.2%, about a third the salinity of most seawater. According to Strabo, it is named after an ancient people called Caspians.
Like the Black Sea and the Mediterranean, the Caspian Sea is a remnant of the Tethys Ocean. It became landlocked about 5.5 million years ago due to continental drift. The Caspian owes what reduced salinity it has to its origins as a remnant of the World Ocean. During warm and dry climatic periods, the landlocked sea has all but dried up, depositing evaporitic sediments like halite that became covered by wind-blown deposits and were sealed off as an evaporite sink when cool, wet climates refilled the basin.Due to the inflow of fresh water, the Caspian Sea is a fresh-water lake in its northern portions. It is more saline on the Iranian shore, where the catchment basin contributes little flow. Currently, the mean salinity of the Caspian is three times less than the Earth's oceans. The largely dried-up Garabogazköl embayment routinely exceeds oceanic salinity.
The Caspian Sea is the largest inland body of water in the world and accounts for 40 to 44 percent of the total lacustrine waters of the world. The coastlines of the Caspian are shared by Azerbaijan, Iran, Kazakhstan, Russia, and Turkmenistan. The Caspian is divided into three distinct physical regions: Northern, Middle, and Southern Caspian. The North-Middle boundary is the Mangyshlak threshold, which runs through Chechen Island and Cape Tiub-Karagan. The Middle-South boundary is the Apsheron threshold, which runs through Zhiloi Island and Cape Kuuli.
Over 130 rivers provide inflow to the Caspian, with the Volga River being the largest. The Caspian also has several small islands; they are primarily located in the North and have a collective land area of roughly 2000 square kilometers.
The Caspian Sea holds great numbers of sturgeon, which yield eggs that are processed into caviar. In recent years overfishing has threatened the sturgeon population to the point that environmentalists advocate banning sturgeon fishing completely until the population recovers. However, the high price of sturgeon caviar allows fisherman to afford bribes to ensure the authorities look the other way, making regulations in many locations ineffective.Caviar harvesting further endangers the fish stocks, since it targets reproductive females.
Map of the Caspian Sea, yellow shading indicates Caspian drainage basin.The Caspian seal, (Phoca caspica, Pusa caspica in some sources) which is endemic to the Caspian Sea, is one of very few seal species that live in inland waters (see also Baikal seal). The area has given its name to several species of birds, including the Caspian gull and the Caspian tern. There are several species and subspecies of fish endemic to the Caspian Sea, including the Kktum (also known as Caspian white fish), Caspian roach, Caspian bream (some report that the Bream occurring in the Aral Sea is the same subspecies), and a Caspian "salmon" (a subspecies of trout, Salmo trutta caspiensis). The "Caspian salmon" is critically endangered.
The Caspian has characteristics common to both seas and lakes. It is often listed as the world's largest lake, though it is not a freshwater lake. The Caspian became landlocked about 5.5 million years ago due to plate tectonics.[citation needed] The Volga River (about 80% of the inflow) and the Ural River discharge into the Caspian Sea, but it has no natural outflow other than by evaporation. Thus the Caspian ecosystem is a closed basin, with its own sea level history that is independent of the eustatic level of the world's oceans. The level of the Caspian has fallen and risen, often rapidly, many times over the centuries. Some Russian historians claim that a medieval rising of the Caspian caused the coastal towns of Khazaria, such as Atil, to flood. In 2004, the water level was -28 metres, or 28 metres (92 ft) below sea level.
Over the centuries, Caspian Sea levels have changed in synchronicity with the estimated discharge of the Volga, which in turn depends on rainfall levels in its vast catchment basin. Precipitation is related to variations in the amount of North Atlantic depressions that reach the interior, and they in turn are affected by cycles of the North Atlantic Oscillation. Thus levels in the Caspian sea relate to atmospheric conditions in the North Atlantic thousands of miles to the north and west. These factors make the Caspian Sea a valuable place to study the causes and effects of global climate change.
The last short-term sea-level cycle started with a sea-level fall of 3 m from 1929 to 1977, followed by a rise of 3 m from 1977 until 1995. Since then smaller oscillations have taken place.