Black Sea

The Black Sea is a marginal sea lying between Europe and Asia, east of the Balkans, south of the East European Plain, west of the Caucasus, and north of Anatolia. It is bounded by Bulgaria, Georgia, Romania, Russia, Turkey, and Ukraine. The Black Sea is supplied by major rivers, principally the Danube, Dnieper and Dniester. Consequently, while six countries have a coastline on the sea, its drainage basin includes parts of 24 countries in Europe.
The Black Sea, not including the Sea of Azov, covers, has a maximum depth of, and a volume of.
Most of its coasts ascend rapidly.
These rises are the Pontic Mountains to the south, bar the southwest-facing peninsulas, the Caucasus Mountains to the east, and the Crimean Mountains to the mid-north.
In the west, the coast is generally small floodplains below foothills such as the Strandzha; Cape Emine, a dwindling of the east end of the Balkan Mountains; and the Dobruja Plateau considerably farther north. The longest east–west extent is about. Important cities along the coast include the northern suburbs of Istanbul, Burgas, Varna, Constanța, Odesa, Yalta, Kerch, Yevpatoria, Sevastopol, Novorossiysk, Sochi, Poti, Batumi, Rize, Trabzon, Ordu, Simferopol, Samsun and Zonguldak.
The Black Sea has a positive water balance, with an annual net outflow of per year through the Bosporus and the Dardanelles into the Aegean Sea. While the net flow of water through the Bosporus and Dardanelles is out of the Black Sea, water generally flows in both directions simultaneously: Denser, more saline water from the Aegean flows into the Black Sea underneath the less dense, fresher water that flows out of the Black Sea. This creates a significant and permanent layer of deep water that does not drain or mix and is therefore anoxic. This anoxic layer is responsible for the preservation of ancient shipwrecks which have been found in the Black Sea, which ultimately drains into the Atlantic Ocean, via the Turkish Straits and the Aegean Sea into the Mediterranean Sea, and from it to the Atlantic proper through the Strait of Gibraltar. The Bosporus strait connects it to the small Sea of Marmara which in turn is connected to the Aegean Sea via the strait of the Dardanelles. To the north, the Black Sea is connected to the Sea of Azov by the Kerch Strait.
The water level has varied significantly over geological time. Due to these variations in the water level in the basin, the surrounding shelf and associated aprons have sometimes been dry land. At certain critical water levels, connections with surrounding water bodies can become established. It is through the most active of these connective routes, the Turkish Straits, that the Black Sea joins the World Ocean. During geological periods when this hydrological link was not present, the Black Sea was an endorheic basin, operating independently of the global ocean system. Currently, the Black Sea water level is relatively high; thus, water is being exchanged with the Mediterranean. The Black Sea undersea river is a current of particularly saline water flowing through the Bosporus Strait and along the seabed of the Black Sea, the first of its kind discovered.

Name

Modern names

Current names of the sea are usually equivalents of the English name "Black Sea", including these given in the countries bordering the sea:

,
,
,
,
,
,
,
Laz and,, or simply ზუღა,,, "Sea"
,
,
,
,

Such names have not yet been shown conclusively to predate the 13thcentury.
In Greece, the historical name "Euxine Sea", which holds a different literal meaning, is still widely used:

, ; the name,, is used, but is much less common.

The Black Sea is one of four seas named in English after common color terms – the others being the Red Sea, the White Sea and the Yellow Sea.

Historical names and etymology

The earliest known name of the Black Sea is the Sea of Zalpa, so called by both the Hattians and their conquerors, the Hittites. The Hattic city of Zalpa was "situated probably at or near the estuary of the Marrassantiya River, the modern Kızıl Irmak, on the Black Sea coast."
The principal Greek name Póntos Áxeinos is generally accepted to be a rendering of the Iranian word *axšaina-. Ancient Greek voyagers adopted the name as Á-xenos, identified with the Greek word áxeinos. The name Πόντος Ἄξεινος , first attested in Pindar, was considered an ill omen and was euphemized to its opposite, Εὔξεινος Πόντος , also first attested in Pindar. This became the commonly used designation in Greek, although in mythological contexts the "true" name Póntos Áxeinos remained favored.
Strabo's Geographica reports that in antiquity, the Black Sea was often simply called "the Sea". He thought that the sea was called the "Inhospitable Sea" Πόντος Ἄξεινος by the inhabitants of the Pontus region of the southern shoreline before Greek colonization due to its difficult navigation and hostile barbarian natives, and that the name was changed to "hospitable" after the Milesians colonized the region, bringing it into the Greek world.
Popular supposition derives "Black Sea" from the dark color of the water or climatic conditions. Some scholars understand the name to be derived from a system of color symbolism representing the cardinal directions, with black or dark for north, red for south, white for west, and green or light blue for east. Hence, "Black Sea" meant "Northern Sea". According to this scheme, the name could only have originated with a people living between the northern and southern seas: this points to the Achaemenids. This interpretation, however, has been contested.
In the Greater Bundahishn, a Middle Persian Zoroastrian scripture, the Black Sea is called Siyābun. In the tenth-century Persian geography book Hudud al-'Alam, the Black Sea is called Georgian Sea. The Georgian Chronicles use the name zğua sperisa ზღუა სპერისა after the Kartvelian tribe of Speris or Saspers. Other modern names such as Chyornoye more and Karadeniz originated during the 13th century. A 1570 map Asiae Nova Descriptio from Abraham Ortelius's Theatrum Orbis Terrarum labels the sea Mar Maggior, compare Latin Mare major.
English writers of the 18th century often used Euxine Sea. During the Ottoman Empire, it was called either Bahr-i Siyah or Karadeniz, both meaning "Black Sea".

Geography

The International Hydrographic Organization defines the limits of the Black Sea as follows:
The area surrounding the Black Sea is commonly referred to as the Black Sea Region. Its northern part lies within the Chernozem belt which goes from eastern Croatia, along the Danube and southern Romania to northeast Ukraine and further across the Central Black Earth Region and southern Russia into Siberia.
The littoral zone of the Black Sea is often referred to as the Pontic littoral or Pontic zone.
The largest bays of the Black Sea are Karkinit Bay in Ukraine; the Gulf of Burgas in Bulgaria; Dnieprovska Gulf and Dniestrovsky Liman, both in Ukraine; and Sinop Bay and Samsun Bay, both in Turkey.

Coastline and exclusive economic zones

Drainage basin

The largest rivers flowing into the Black Sea are:

These rivers and their tributaries comprise a Black Sea drainage basin that covers wholly or partially 24 countries:

Unrecognized states:

Islands

Some islands in the Black Sea belong to Bulgaria, Romania, Turkey, and Ukraine:

St. Thomas Island – Bulgaria
St. Anastasia Island – Bulgaria
St. Cyricus Island – Bulgaria
St. Ivan Island – Bulgaria
St. Peter Island – Bulgaria
Sacalinu Mare Island – Romania
Sacalinu Mic Island – Romania
K Island – Romania and Ukraine
Utrish Island
Krupinin Island
Sudiuk Island
Kefken Island
Oreke Island
Giresun Island – Turkey
Dzharylhach Island – Ukraine
Zmiinyi Island – Ukraine
Climate

Short-term climatic variation in the Black Sea region is significantly influenced by the operation of the North Atlantic oscillation, the climatic mechanisms resulting from the interaction between the north Atlantic and mid-latitude air masses. While the exact mechanisms causing the North Atlantic Oscillation remain unclear, it is thought the climate conditions established in western Europe mediate the heat and precipitation fluxes reaching Central Europe and Eurasia, regulating the formation of winter cyclones, which are largely responsible for regional precipitation inputs and influence Mediterranean sea surface temperatures.
The relative strength of these systems also limits the amount of cold air arriving from northern regions during winter. Other influencing factors include the regional topography, as depressions and storm systems arriving from the Mediterranean are funneled through the low land around the Bosporus, with the Pontic and Caucasus mountain ranges acting as waveguides, limiting the speed and paths of cyclones passing through the region.

Geology and bathymetry

The Black Sea is divided into two depositional basins—the Western Black Sea and Eastern Black Sea—separated by the Mid-Black Sea High, which includes the Andrusov Ridge, Tetyaev High, and Archangelsky High, extending south from the Crimean Peninsula. The basin includes two distinct relict back-arc basins which were initiated by the splitting of an Albian volcanic arc and the subduction of both the Paleo- and Neo-Tethys oceans, but the timings of these events remain uncertain. Arc volcanism and extension occurred as the Neo-Tethys Ocean subducted under the southern margin of Laurasia during the Mesozoic. Uplift and compressional deformation took place as the Neotethys continued to close. Seismic surveys indicate that rifting began in the Western Black Sea in the Barremian and Aptian followed by the formation of oceanic crust 20million years later in the Santonian. Since its initiation, compressional tectonic environments led to subsidence in the basin, interspersed with extensional phases resulting in large-scale volcanism and numerous orogenies, causing the uplift of the Greater Caucasus, Pontides, southern Crimean Peninsula and Balkanides mountain ranges.
File:Yavuz-Sultan-Selim-Brücke.jpg|thumb|The Yavuz Sultan Selim Bridge in Istanbul, Turkey, crosses the Bosporus strait near its entrance to the Black Sea. Connecting Europe and Asia, it is one of the tallest suspension bridges in the world.
During the Messinian salinity crisis in the neighboring Mediterranean Sea, water levels fell but without drying up the sea. The collision between the Eurasian and African plates and the westward escape of the Anatolian block along the North Anatolian and East Anatolian faults dictates the current tectonic regime, which features enhanced subsidence in the Black Sea basin and significant volcanic activity in the Anatolian region. These geological mechanisms, in the long term, have caused the periodic isolations of the Black Sea from the rest of the global ocean system.
The large shelf to the north of the basin is up to wide and features a shallow apron with gradients between 1:40 and 1:1000. The southern edge around Turkey and the eastern edge around Georgia, however, are typified by a narrow shelf that rarely exceeds in width and a steep apron that is typically 1:40 gradient with numerous submarine canyons and channel extensions. The Euxine abyssal plain in the center of the Black Sea reaches a maximum depth of just south of Yalta on the Crimean Peninsula.