Black Sea | Location, Region, Map, Countries, & Facts - Britannica

Physiography

The coastline of the Black Sea is only mildly indented, except for the northwestern and northern shores, which are low and furrowed by numerous ravines, valleys, and rivers, the mouths of which are often impeded by sandy spits. The mountains of southern Crimea form the only precipitous cliff areas. In the east and south, the coasts are steep and mountainous. Spurs of the Greater and Lesser Caucasus ranges, separated by the Kolkhida lowland, confine the Black Sea in the east, while the Pontic Mountains run along the southern coast. Near the Bosporus outlet, the shoreline relief is moderate though still steep. Farther north, in the Burgaski Bay area, low mountains emerge where the Balkan Mountains of Bulgaria extend eastward. Continuing northward along the western shore, a flatter plateau region gives way to the great Danube River delta, which thrusts its mass out into the sea.

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The Black Sea contains only a few small islands, the largest being Zmiyinyy (Fidonisi) of Ukraine, east of the Danube delta, and Berezan at the mouth of the Dniester River estuary. The submarine relief may be visualized as a series of concentric and occasionally asymmetrical rings. Beyond the shoreline a shallow shelf zone occupies about one-fourth of the entire area. It is broadest in the west and at the head of Kerch Strait but elsewhere forms a rim about 6 to 7 miles (10 to 11 km) wide, and the depth of the edge is usually less than 360 feet (110 metres). The shelf gives way at its edge to a slope, which is broken by submarine valleys and is steep in its upper parts. Between the port cities of Sinop and Samsun (Turkey), the coastline is paralleled by a rugged range of underwater mountains extending for nearly 100 miles (160 km). The hollow forming the basin’s core covers about a third of the total area and is a completely featureless flat plain, with depths increasing evenly toward the centre to a little more than 7,200 feet (2,200 metres), with the axis of maximum depth displaced toward the Turkish coast.