Caspian Depression is a
low-lyingIn physical geography, a lowland is any broad expanse of land with a general low level. The term is thus applied to the landward portion of the upward slope from oceanic depths to continental highlands, to a region of depression in the interior of a mountainous region, to a plain of denudation, or...
flatlandFlatland: A Romance of Many Dimensions is an 1884 satirical novella by the English schoolmaster Edwin Abbott Abbott. Writing pseudonymously as "a square" , Abbott used the fictional two-dimensional world of Flatland to offer pointed observations on the social hierarchy of Victorian culture...
region encompassing the northern part of the
Caspian SeaThe 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 kilometres and a volume of 78,200 cubic kilometres...
, the largest enclosed
body of waterA body of water or waterbody is any significant accumulation of water, usually covering the Earth or another planet. The term body of water most often refers to large accumulations of water, such as oceans, seas, and lakes, but it may also include smaller pools of water such as ponds, puddles or...
on
EarthEarth is the third planet from the Sun. It is the fifth largest of the eight planets in the solar system, and the largest of the terrestrial planets in the Solar System in terms of diameter, mass and density...
.. It is part of the wider
Aral-Caspian DepressionThe Aral-Caspian Depression is a lowland depression straddling Europe and Asia around the Aral Sea and Northern Caspian Sea. Its parts belong to Azerbaijan, Russia, Kazakhstan, Uzbekistan, and Turkmenistan. The part within the Caspian drainage basin is called the Caspian Depression...
around the
AralThe Aral Sea is an endorheic basin in Central Asia; it lies between Kazakhstan in the north and Karakalpakstan, an autonomous region of Uzbekistan, in the south...
and Caspian seas. Other translations include
Pricaspian/Peri-Caspian Depression/Lowland.
The lowest point of the depression is 28m or 92 feet below sea level. The
depressionDepression in geology is a landform sunken or depressed below the surrounding area. Depressions may be formed by various mechanisms, and may be referred to by a variety of technical terms.*A basin may be any large sediment filled depression...
lies at the southern end of the
Ryn DesertThe Ryn Desert or Ryn-Peski Desert , is a desert in western Kazakhstan and southeastern Russian republic of Kalmykia, north of the Caspian Sea and southeast of the Volga Upland. The borders of the desert are very loosely defined...
, and is in both
KazakhstanKazakhstan , officially the Republic of Kazakhstan, is a country situated in Eurasia that is ranked as the ninth largest country in the world. It is also the world's largest landlocked country. Its territory of 2,727,300 km² is greater than Western Europe...
and
RussiaRussia , officially known as both Russia and the Russian Federation , is a country in northern Eurasia . It is a semi-presidential republic, comprising 83 federal subjects...
. Most of the Russian Republic of
KalmykiaThe Republic of Kalmykia is a federal subject of the Russian Federation . The direct romanization of the republic's Russian name is Respublika Kalmykiya, and that of the Kalmyk name is Xal'mg Tanghch. It is the only state in Europe where the dominant religion is Buddhism...
lies in the Caspian Depression. The
Volga RiverThe Volga is the largest river in Europe in terms of length, discharge, and watershed. It flows through western Russia, and is widely viewed as the national river of Russia. Out of the twenty largest cities of Russia, eleven, including its capital Moscow, are situated in the Volga's drainage basin...
and the
Ural RiverThe Ural , known as Yaik before 1775, is a river flowing through Russia and Kazakhstan. It arises in the southern Ural Mountains and ends at the Caspian Sea. Its total length is 1,511 mi...
flow into the Caspian Sea through this region. The deltas of the Ural and Volga Rivers are extensive wetlands.
The North Caspian depression is part of the
continentalContinental is the adjective form of continent. Continental may refer to:* Continental , an album by UK band Saint Etienne* Continental , a brand of dried and pre-packaged foods used by Unilever in Australia...
or
semi-aridA Semi-arid climate or steppe climate generally describes climatic regions that receive low annual rainfall . A more precise definition is given by the Köppen climate classification that treats steppe climates as intermediates between the desert climates and humid climates in ecological...
desert
biomeBiome are climatically and geographically defined areas of ecologically similar climatic conditions such as communities of plants, animals, and soil organisms, and are often referred to as ecosystems...
. The area receives 30 centimeters (12 in) of rain or less per year, on average, and less than 10% of the region is irrigated.
KaragiyeKaragiye is the lowest point in Kazakhstan. Also called the "Karagiye Depression", it lies at approximately 132 meters below sea level, and is the lowest point in the former USSR....
, the lowest point in Kazakhstan, is in the depression, at 132 meters (433 ft) below sea level.
Much of the Caspian Depression is below sea-level, consisting of large areas of marshlands in the eastern region. It is one of the largest flat lowland areas in
Central AsiaAsia is a region of Asia from the Caspian Sea in the west to central China in the east, and from southern Russia in the north to northern India in the south. It is also sometimes known as Middle Asia or Inner Asia, and is within the scope of the wider Eurasian continent.Various definitions of its...
, covering approximately 200,000 kilometers² (77,220 miles²). The area is very rich in underground oil and gas reserves, and oil and natural gas pipelines cross the depression from north to south and east to west. Many geologists believe the Caspian Sea and the depression were formed by tectonic forces. Some of them also believe that the North Caspian depression became separated from the open ocean in ancient times to form an enormous salt lake. Part of the ancient
Silk RoadThe Silk Road is an extensive interconnected network of trade routes across the Asian continent connecting East, South, and Western Asia with the Mediterranean world, as well as North and Northeast Africa and Europe...
ran through this region. The two largest cities in the depression are
AstrakhanAstrakhan is a major city in southern European Russia and the administrative center of Astrakhan Oblast. The city lies on the Volga River, close to where it discharges into the Caspian Sea. Population: 502,800 ; 504,501 ; 509,210 .-Medieval history:Astrakhan' is situated in the Volga Delta, rich...
in Russia, and
AtyrauAtyrau is a city in Kazakhstan, and the capital of Atyrau Province. It is located 2700 kilometers west of Almaty and 350 kilometers east of the Russian city of Astrakhan. Other transliterations include Aterau, Atirau, Atyraw, Atyraou, Atırav, Atıraw.Modern Atyrau is famous for its oil and fish...
in Kazakhstan. Today, the region is used mainly for livestock raising.
The depression is also noted for
salt domeA salt dome is a type of structural dome formed when a thick bed of evaporite minerals found at depth intrudes vertically into surrounding rock strata, forming a diapir....
s, particularly Volgograd salt, whose sizes increase dramatically as one travels from the
Ryn DesertThe Ryn Desert or Ryn-Peski Desert , is a desert in western Kazakhstan and southeastern Russian republic of Kalmykia, north of the Caspian Sea and southeast of the Volga Upland. The borders of the desert are very loosely defined...
toward the Caspian Sea. Russian satellite photos have revealed huge deposits of salt domes (about 1,200), in the Caspian Depression in western Kazakhstan. One dome, called the Chelkar Deposit, covers an area of 3,237 kilometers² (1,249 miles²) and is nearly 8 kilometers (4.9 miles) deep.
The southern region of the depression, or the north coast of the Caspian Sea, is characterized by large development of damp sites resulting from tidal phenomena. The depression is also home to a large number of
insectInsects are arthropods, having a hard exoskeleton, a three-part body , three pairs of jointed legs, compound eyes, and two antennae. They are the most diverse group of animals on the planet and include more than a million species that are already described. Insects represent more than half of all...
speciesIn biology, a species is:* a taxonomic rank or* a unit at that rank ....
, with several thousand different species likely living in the region around the Caspian Sea. Studies have shown that
water pollutionWater pollution is the contamination of water bodies such as lakes, rivers, oceans, and groundwater. All water pollution affects organisms and plants that live in these water bodies and in almost all cases the effect is damaging either to individual species and populations but also to the natural...
, mostly coming from the Volga River, poses a serious threat to the
biodiversityBiodiversity is the variation of life forms within a given ecosystem, biome, or for the entire Earth. Biodiversity is often used as a measure of the health of biological systems...
of the Caspian Depression. Water pollution is contributed mainly by
industrialAn industry is the manufacturing of a good or service within a category. Although industry is a broad term for any kind of economic production, in economics and urban planning industry is a synonym for the secondary sector, which is a type of economic activity involved in the manufacturing of raw...
, agricultural, and household discharges.