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Black Sea
From Wikipedia, the free encyclopedia
Satellite view of the Black Sea, taken by NASA MODIS
Coordinates 35°E / 44°N 35°E / 44; 35Coordinates: 35°E / 44°N 35°E / 44; 35
Max. length 1,175 km (730 mi)
Surface area 436,400 km2 (168,500 sq mi)
Max. depth 2,206 m (7,238 ft)
Water volume 547,000 km3 (131,000 cu mi)
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The Black Sea is an inland sea bounded by Europe, Anatolia and the Caucasus and is ultimately connected to the Atlantic Ocean via the Mediterranean and Aegean Seas and various straits. The Bosphorus strait connects it to the Sea of Marmara, and the strait of the Dardanelles connects it to the Aegean Sea region of the Mediterranean. These waters separate eastern Europe and western Asia. The Black Sea also connects to the Sea of Azov by the Strait of Kerch.
The Black Sea has an area of 436,400 km2 (168,495.0 sq mi),[1] a maximum depth of 2,206 m (7,238 ft),[2] and a volume of 547,000 km³ (133,500 cu mi).[3] The Black Sea forms in an east-west trending elliptical depression which lies between Bulgaria, Georgia, Romania, Russia, Turkey, and Ukraine.[4] It is constrained by the Pontic Mountains to the south, the Caucasus Mountains to the east and features a wide shelf to the north-west. The longest east-west extent is about 1,175 km.
Important cities along the coast include Batumi, Burgas, Constanţa, Giresun, Istanbul, Kerch, Kherson, Mangalia, Năvodari, Novorossiysk, Odessa, Ordu, Poti, Rize, Samsun, Sevastopol, Sochi, Sukhumi, Trabzon, Varna, Yalta and Zonguldak.
The Black Sea has a positive water balance, which results in a net outflow of water 300 km³ per year through the Bosphorus and the Dardanelles into the Aegean Sea (part of the Mediterranean Sea). Mediterranean water flows into the Black Sea as part of a 2-way hydrological exchange. The Black Sea outflow is cooler and less saline , and therefore floats over the warm, more saline Mediterranean inflow. The Black Sea also receives river water from large Eurasian fluvial systems to the north of the Sea, of which the Don, Dnieper and Danube are the most significant.
In the past, the water level has varied significantly. Depending on the water level in the basin, varying surrounding shelf and associated aprons are aerially exposed. At certain critical depths, it is possible for connections with surrounding water bodies to become established. It is through the most active of these connective routes, the Turkish Straits, that the Black Sea joins the global ocean system. When this hydrological link is not present, the Black Sea is a lake, 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 Turkish Straits connect the Black and Aegean Seas and comprise the Bosphorus, the Sea of Marmara and the Dardanelles.
Extent
The International Hydrographic Organization defines the limits of the Black Sea as follows:[5]
On the Southwest. The Northeastern limit of the Sea of Marmara [A line joining Cape Rumili with Cape Anatoli (41°13'N)].
In the Kertch Strait. A line joining Cape Takil and Cape Panaghia (45°02'N).
Name
Modern names
Current names of the Sea are equivalents of the English name, "Black Sea", including Adyghe: (Хы ШIуцI), Greek Mavri Thalassa (Μαύρη Θάλασσα), Bulgarian Cherno more (Черно море), Georgian Shavi zghva (შავი ზღვა), Laz Ucha Zuğa, or simply Zuğa 'Sea', Romanian Marea Neagră, Russian Chornoye more (Чёрное море), Turkish Karadeniz, Ukrainian Chorne more (Чорне море), Ubykh [ʃʷad͡ʒa]. Such names have not yet been shown conclusively to predate the twelfth century, but there are indications that they may be considerably older.
The reason for this color term may be an ancient assignment of colors to the cardinal directions—black referring to the north, red referring to the south, and yellow to the east. Herodotus on one occasion uses Red Sea and Southern Sea interchangeably.[6] A somewhat similar view shows the Turkish name: 'Kara (Black)' and 'Ak (White)' are respectively used to denote 'North' and 'South' in Medieval Turkish, as in Akhun Empire, Akkoyunlu and Karakoyunlu Empires, and Akdeniz (lit., 'White Sea', referring to the Mediterranean which lies south of Anatolia[citation needed]). Another possible explanation comes from the colour of the Black Sea's deep waters. Being further north than the Mediterranean Sea and much less saline, the microalgae concentration is much richer, causing the dark colour. Visibility in the Black Sea is on average approximately five metres (5.5 yd), as compared to up to thirty-five metres (38 yd) in the Mediterranean.[citation needed]
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
Strabo's Geography (1.2.10) reports that in antiquity, the Black Sea was often just called "the Sea" (ho pontos). For the most part, Graeco-Roman tradition refers to the Black Sea as the 'Hospitable sea', Euxeinos Pontos (Εὔξεινος Πόντος). This is a euphemism replacing an earlier 'Inhospitable Sea', Pontos Axeinos, first attested in Pindar (early fifth century BCE,~475 BC). Strabo (7.3.6) thinks that the Black Sea was called "inhospitable" before Greek colonization because it was difficult to navigate, and because its shores were inhabited by savage tribes. The name was changed to "hospitable" after the Milesians had colonized southern shoreline, the Pontus, making it part of Greek civilization.
It is also possible that the name Axeinos arose by popular etymology from a Scythian Iranic axšaina- 'unlit,' 'dark'; the designation "Black Sea" may thus date from Antiquity.
One Bulgarian understanding of the name is that the sea used to be quite stormy. The Black Sea deluge theory is based on that idea.[citation needed]
In naval science, the Black Sea is thought to have received its name because of its hydrogen sulphide layer that begins about 200 metres below the surface, and supports a unique microbial population which produces black sediments probably due to anaerobic methane oxidation.[citation needed]
Geology and bathymetry
The geological origins of the basin can be traced back to 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 controversial.[7][8] 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 Crimea and Balkanides mountain ranges. The ongoing collision between the Eurasian and African plates and westward escape of the Anatolian block along the North Anatolian Fault and East Anatolian Faults dictates the current tectonic regime,[9] which features enhanced subsidence in the Black Sea basin and significant volcanic activity in the Anatolian region.[10] It is these geological mechanisms which, in the long term, have caused the periodic isolations of the Black Sea from the rest of the global ocean system.