The Black Sea (also known as the Euxine Sea) is an inland sea between southeastern Europe and Asia Minor. It is connected to the Mediterranean Sea by the Bosporus and the Sea of Marmara, and to the Sea of Azov by the Strait of Kerch.
There is a net inflow of seawater through the Bosporus, 200 km³ per year. There is an inflow of freshwater from the surrounding areas, especially central and middle-eastern Europe, totalling 320 km³ per year. The most important river entering the Black Sea is the Danube. The Black Sea has an area of [[1 E11 m�|422,000 km�]] and a maximum depth of 2210 m.
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 low salinity (and therefore density) of the water flowing into it from rivers and the Mediterranean; 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).
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 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 Ryan and 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.
In 1997, William Ryan and Walter Pitman from Columbia University published evidence that a massive flood through the Bosporus occurred about 5600 BC. Glacial meltwater had turned the Black and Caspian Seas into vast freshwater lakes, while sea levels remained lower. As the glaciers retreated, rivers emptying into the Black Sea reduced their volume and the water levels lowered. Then, about 5600 BC, as sea levels rose, the Mediterranean spilled over a rocky sill at the Bosphorus. The event flooded 60,000 mile² (155,000 km²) of land, and significantly expanded the Black Sea shoreline to the north and east. Ryan and Pitman wrote:
- "Ten cubic miles [42 km³] of water poured through each day, two hundred times what flows over Niagara Falls. ... The Bosporus flume roared and surged at full spate for at least three hundred days."
Although neolithic agriculture had by that time already reached the Pannonian plain, the authors link its spread with people displaced by the postulated flood. It has been suggested that the survivors' memory of this event was the source of the legend for Noah's Flood. Initial resistance came from those who looked for more detailed correlation with the Book of Genesis (see Noah's Ark and Mount Ararat) or preferred as prototype the similar marine ingression that formed the Persian Gulf in the lower Tigris and Euphrates valley.
Subsequent work by marine archeologist Robert Ballard has identified ancient shorelines, freshwater snail shells, drowned river valleys and tool-worked timbers in 300 feet (100 m) of water off the coast of modern Turkey.
The Black Sea region is thought to have been the original homeland (Urheimat) of "Proto-Indo-European", (PIE) the progenitor of the Indo-European language family, by some scholars. Others move the heartland further east towards the Caspian Sea.
The name (initially Pontus Euxinus) was coined by the Ancient Greek navigators, because of the unusual dark colour, compared with the Mediterranean Sea. Visibility in the Black Sea is on average approximately 15 feet (as compared to up to 100 feet (30 m) 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.
- William Ryan and Walter Pitman, Noah's Flood, 1999, ISBN 0684859203
- Neal Ascherson, Black Sea (Vintage 1996)
cs:Černé moře [[cy:Y M�r Du]] da:Sortehavet de:Schwarzes Meer et:Must meri es:Mar Negro eo:Nigra Maro fr:Mer Noire it:Mar Nero nl:Zwarte Zee ja:黒海 no:Svartehavet pl:Morze Czarne pt:Mar Negro ro:Marea Neagră ru:Чёрное море sl:Črno morje fi:Mustameri sv:Svarta havet tr:Karadeniz uk:Чорне море zh-tw:黑海