Many people still wonder why it is called "black". The color of the sea depends on the weather. On cloudless days the sea is blue-green and when the sky is covered by heavy, dark clouds it is silvery gray or azure. But no one has ever seen it black.
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.
An unusual feature of the Black Sea is that oxygen is dissolved only in the upper levels of its waters, which alone can support a rich sea life as a result. Below a depth of 230–330 feet (70–100 m) at the centre and 330–500 feet (100–150 m) near the sea's margins, there is no oxygen because the sea is permeated by a high concentration of dissolved hydrogen sulfide, forming a saturated, “dead” zone inhabitable only by specially adapted bacteria. Despite this anomaly, the Black Sea's uppermost waters supported abundant sturgeon, mackerel, and anchovy until the late 20th century, when the runoff of industrial and municipal wastes into the Danube, Dnieper, and other feeder rivers caused increasing levels of pollution and consequent reductions in fish populations.
The Black Sea is connected to the distant waters of the Atlantic Ocean by the succession of the Bosporus (a strait at the Black Sea's southwestern corner), the Sea of Marmara, the Dardanelles, the Aegean Sea, and the Mediterranean Sea. The peninsula of Crimea extends into the sea from the north, and immediately to the east the narrow Kerch Strait opens onto the smaller Sea of Azov. The Black Sea's water-surface area is about 178,000 square miles (461,000 square km), and its maximum depth is more than 7,250 feet (2,210 m). The Black Sea has few coastal lowlands. The Danube, Dnieper, Dniester, and Don are the largest rivers emptying into the sea.
