A positive water budget pushes Black Sea water into the Aegean
The Black Sea sits between Europe and Asia, bordered by Bulgaria, Georgia, Romania, Russia, Turkey, and Ukraine. Without Azov it covers about 436,400 square kilometres, reaches 2,212 metres deep, and holds roughly 547,000 cubic kilometres—fed by great rivers yet exporting a net 300 cubic kilometres yearly through the Turkish Straits.
Wedged between the Balkans, the steppe plains to its north, the Caucasus and Anatolia, the sea stretches about 1,175 kilometres from west to east. Mountains ring much of it: the Pontic range to the south, the Caucasus to the east and the Crimean Mountains in the middle north, while the western shore is mostly small floodplains below hills such as the Strandzha and the Dobruja Plateau. The Danube, Dnieper and Dniester are its chief feeders, and although only six countries touch the coast, its drainage basin of some 2 million square kilometres reaches into 24. Coastal cities run from Istanbul's northern suburbs through Varna, Constanța, Odesa, Sevastopol, Sochi, Batumi and Trabzon to Samsun.
Its two-way plumbing is unusual. Lighter, fresher surface water streams out through the Turkish Straits while denser, saltier Aegean water slides in underneath, and a saline current running through the Bosporus and along the seabed was the first undersea river ever found. The heavy bottom layer never mixes or drains, so it holds no oxygen, which is why ancient shipwrecks survive remarkably intact down there. Over geological time the level has risen and fallen enough to expose the shelves as dry land, and whenever the link to the Mediterranean was cut the sea became a closed basin like today's Caspian. At present the level is high, so exchange continues.
The oldest known name is the Sea of Zalpa, used by the Hattians and Hittites after a city near the mouth of the Kızıl Irmak. Greeks adopted an Iranian word meaning dark as Áxeinos, which sounded like their word for inhospitable. Pindar, around 475 BC, is the first to record both that name and its lucky opposite, Eúxeinos, hospitable. Strabo thought the change came after Milesian colonists settled the coast.
Why black? Some point to dark water or grim weather; others to a Turkic scheme in which black meant north, making it simply the Northern Sea, an idea that is contested. Medieval writers called it the Georgian Sea, the Russian Sea or the Great Sea, and the modern Chyornoye more and Karadeniz date from the thirteenth century.
Source: Black Sea
