Black sea

Black Sea old map	Black sea satellite photo

Russian and Bulgarian CHERNOYE MORE, Ukrainian CHORNE MORE, Turkish KARADENZ, Romanian MAREA NEAGRA, large inland sea situated at the southeastern extremity of Europe. It is bordered by Ukraine to the north, Russia to the northeast, Georgia to the east, Turkey to the south, and Bulgaria and Romania to the west.

The roughly oval-shaped Black Sea occupies a large basin strategically situated at the southeastern extremity of Europe but connected to the distant waters of the Atlantic Ocean by the Bosporus (which emerges from the sea's southwestern corner), the Sea of Marmara, the Dardanelles, the Aegean Sea, and the Mediterranean Sea. The renowned Crimean Peninsula thrusts into the Black Sea from the north, and just to its east the narrow Kerch Strait links the sea to the smaller Sea of Azov. The Black Sea coastline is otherwise fairly regular. The maximum east-west extent of the sea is about 730 miles (1,175 kilometres), while the shortest distance between the tip of the Crimea and the Kerempe Burmi Cape to the south is about 160 miles. The surface area, excluding the Sea of Marmara but including the Sea of Azov, is about 178,000 square miles (461,000 square kilometres); the Black Sea proper occupies about 163,000 square miles (422,000 square kilometres). A maximum depth of more than 7,250 feet (2,210 metres) is reached in the south-central sector of the sea.
In ancient Greek myths, the sea--then on the fringe of the Mediterranean world--was named Pontus Axeinus, meaning "Inhospitable Sea." Later explorations made the region more familiar, and, as colonies were established along the shores of a sea the Greeks came to know as more hospitable and friendly, its name was changed to Pontus Euxinus, the opposite of the earlier designation. It was across its waters that Jason and the Argonauts set out, according to legend, to find the Golden Fleece in the land of Colchis, a kingdom at the sea's eastern tip (now Georgia). The Turks, when they came to control the lands beyond the sea's southern shores, encountered only the sudden storms whipped up on its waters and reverted to a designation reflecting the inhospitable aspect of what they now termed the Karadeniz, or Black Sea.

To scientists the Black Sea is a remarkable feature because its lower levels are, to all intents and purposes, almost biologically dead--not because of modern pollution but because of continued weak ventilation of the deep layers. To the nations of the region, the Black Sea has been of immense strategic importance over the centuries; the advent of more settled conditions has brought its economic importance to the fore.

History

The steppes to the north of the Black Sea suggested as the original homeland (Urheimat) of the speakers of the Proto-Indo-European language, (PIE) the progenitor of the Indo-European language family, by some scholars (see Kurgan; others move the heartland further east towards the Caspian Sea, yet others to Anatolia).

The name 'Black Sea' (initially Pontos Axeinos, "inhospitable sea", later renamed Pontos Euxeinos, "hospitable sea" to gain the sea's good favor) was coined by the Ancient Greek navigators, because of the unusual dark color, compared with the Mediterranean Sea. Visibility in the Black Sea is on average approximately 5 metres (15 feet), as compared to up to 35 metres (100 feet) in the Mediterranean. The land at the eastern end of the Black Sea, Colchis (now Georgia), marked for the Greeks an edge of the known world.

Geology

The Black Sea is the largest anoxic, or oxygen-free, marine system. This is a result of the great depth of the sea and the relatively high salinity (and therefore density) of the water at depth; freshwater and seawater mixing is limited to the uppermost 100 to 150 m, with the water below this interface (called the pycnocline) being exchanged only once every thousand years. There is therefore no significant gas exchange with the surface, and as a result decaying organic matter in the sediment consumes any available oxygen. In these anoxic conditions some extremophile microorganisms are able to use sulfate (SO42−) for oxidation of organic material, producing hydrogen sulfide (H2S) and carbon dioxide. This mix is extremely toxic (a lungful would be fatal to a human), resulting in a sea that has almost all of its ecology living in that top layer down to a depth of approximately 180 m (600 ft). The relative lack of micro-organisms and oxygen has allowed deep-sea expeditions to recover ancient (on the order of thousands of years) human artifacts, such as boat hulls and the remains of settlements.
The Bulgarian coastline of the Black Sea doesn't have many islands. Those that exist are mostly small, uninhabited and covered with algae.
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The Bulgarian coastline of the Black Sea doesn't have many islands. Those that exist are mostly small, uninhabited and covered with algae.
Large amounts of organic material reach the bottom of the sea and accumulate in the sediments in concentrations of up to 20%. These kinds of sediments are called sapropel.
While it is agreed that the Black Sea has been a sweetwater lake (at least in upper layers) with a considerably lower level during the last glaciation, its postglacial development into a marine sea is still a subject of intensive study and debate. There are catastrophic scenarios such as put forward by William Ryan and Walter Pitman as well as models emphasizing a more gradual transition to saline conditions and transgression in the Black Sea. They are based on different theories about the level the sweetwater lake had reached by the time the Mediterranean Sea was high enough to flow over the Dardanelles and the Bosphorus. On the other hand, a study of the sea floor on the Aegean side shows that in the 8th millennium BCE there was a large flow of fresh water out of the Black Sea (New Scientist, 4 May 2002, p. 13).

Bibliography



L.A. Zenkevich, "The Black Sea," in his Biology of the Seas of the U.S.S.R., chapter 9 (1963; originally published in Russian, 1963), is dated but still useful. More recent texts include Iu.I. Sorokin, Chernoe More: priroda, resursy (1982), on the nature and resources of the sea; A.I. Riabinin and V.N. Kravets, Sovremennoe sostoianie serovodorodnoi zony Chernogo Moria: 1960-1986 gody (1989), containing scholarship on the hydrogen sulfide content of the deep waters; Egon T. Degens and David A. Ross (eds.), The Black Sea--Geology, Chemistry, and Biology (1974); and D. Tolmazin, "Changing Coastal Oceanography of the Black Sea," Progress in Oceanography, 15(4):217-316 (1985).

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