The Black Sea

The Black Sea is a marginal sea located between Europe and Asia, east of the Balkans, south of the East European Plain, west of the Caucasus, and north of Anatolia. It is bordered 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 436,400 km2 (168,500 sq mi), has a maximum depth of 2,212 m (7,257 ft), and a volume of 547,000 km3 (131,000 cu mi).
Most of its coasts ascend rapidly.
These rises are the Pontic Mountains to the south, 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 1,175 km (730 mi). Important cities along the coast include (clockwise from the Bosporus) the northern suburbs of Istanbul, Burgas, Varna, Constanța, Odesa, Yevpatoria, Sevastopol, Yalta, Kerch, Novorossiysk, Sochi, Poti, Batumi, Rize, Trabzon, Ordu, Samsun and Zonguldak.
The Black Sea has a positive water balance, with an annual net outflow of 300 km3 (72 cu mi) per year through the Bosporus and the Dardanelles into the Aegean Sea. While the net flow of water through the Bosporus and Dardanelles (known collectively as the Turkish Straits) 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.…