|
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.
The Black Sea is a residual basin of the ancient
Tethys Sea; its present form probably emerged about 58 million years
ago when structural upheavals in Anatolia split off the Caspian
basin from the Mediterranean. The newly formed Black Sea basin gradually
became isolated from the ocean, its salinity was reduced, and it
was slowly separated from the Caspian region. The salinity of the
Black Sea is almost half that of the world's oceans.
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 230330
feet (70100 m) at the centre and 330500 feet (100150
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 roughly oval-shaped Black Sea occupies a large
basin strategically situated at the southeastern extremity of Europe
but connected to the distant waters of the Atlantic Ocean by the
Bosporus (which emerges from the sea's southwestern corner), the
Sea of Marmara, the Dardanelles, the Aegean Sea, and the Mediterranean
Sea. The renowned Crimean Peninsula thrusts into the Black Sea from
the north, and just to its east the narrow Kerch Strait links the
sea to the smaller Sea of Azov. The Black Sea coastline is otherwise
fairly regular. The maximum east-west extent of the sea is about
730 miles (1,175 kilometres), while the shortest distance between
the tip of the Crimea and the Kerempe Burmi Cape to the south is
about 160 miles. The surface area, excluding the Sea of Marmara
but including the Sea of Azov, is about 178,000 square miles (461,000
square kilometres); the Black Sea proper occupies about 163,000
square miles (422,000 square kilometres). A maximum depth of more
than 7,250 feet (2,210 metres) is reached in the south-central sector
of the sea.
In ancient Greek myths, the seathen on the
fringe of the Mediterranean worldwas 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.
To scientists the Black Sea is a remarkable feature
because its lower levels are, to all intents and purposes, almost
biologically deadnot because of modern pollution but because
of continued weak ventilation of the deep layers. To the nations
of the region, the Black Sea has been of immense strategic importance
over the centuries; the advent of more settled conditions has brought
its economic importance to the fore. |