The Black Sea is not large (450,000 square kilometers). It is a landlocked sea, situated between Europe and Asia, and connected with the Mediterranean Sea by the narrow Straits of theBosphorus and the Dardanelles and the Sea of Marmora, which, geologically speaking, is a basin formed by subsidence. Great subsidences of the earth's surface created the deep basin of the Pontus. The Pontus was a part of the extensive upper Miocene and Sarmatian inland sea, which slightly flooded large districts of the present European continent as far as the Vienna basin. Toward the end of the tertiary period, this inland sea shrank and separated into single sea basins. The Pontian basin became connected with the Mediterranean Sea later, in the latter part of the diluvial period, by means of great subsidences of recent date.
The present morphology of the Pontus is in full accord with this genesis. The northern part, as far as the line of communication between the Balkan and Yaila Mountains, is a shallow sea of a depth of less than 200 meters; the so-called bay of Odessa is barely 50 meters deep; the Sea of Azof, projecting to the northeast, barely 15 meters. But just on the southern border of the line of plicated mountains, which is broken at this point, the bottom of the Black Sea declines rapidly to greater depths (1500 meters) until, declining more gradually now, it attains the depth of 2245 meters in the center of the oval-shaped main basin of the Pontus.
The salt content of the Black Sea is much smaller than that of the ocean, or even of the Mediterranean. The Sea is comparatively small, and receives a great deal of fresh water from the many and large rivers of the region which it drains, while the influx of salt water from the Mediterranean thru the shallow straits cannot be great. The salt content is on the average 1.8%; only at great depths does it reach 2.2%. The diluted surface layer shows barely 1.5% salt content; the Sea of Azof hardly 1%. The surface water, containing little salt but a great deal of air, cannot, because of the greater density of the lower layers of water, sink far, and this low degree of ventilation accounts for the fact that the waters of the Black Sea below a depth of 230 meters are saturated with sulphide of hydrogen, and thus preclude any possibility of organic deep-sea life.
Nevertheless, the Black Sea is notable for its beautiful blue-green color and the great transparency of its waters. A white disc, on being submerged, disappeared only at a depth of 77 meters.
The surface temperature of the Black Sea is subject to many fluctuations; from 27° C in midsummer to 5° C in winter. In severe winters the Sea is frozen over in the bay of Odessa for a short time; the Limans and the Sea of Azof regularly for from two to three months.
The Black Sea has been known since hoary antiquity as a dangerous, stormy sea. The waves, running as high as 10 meters, the short cross-waves caused by the proximity of the shores, the difficult approaches to the land, are still a great hindrance to navigation, especially in the winter time. Not without cause did the Greeks originally call it "the inhospitable sea," until the great number of flourishing Greek settlements on its shores led them to change its name to "hospitable sea." Despite this euphemistic name, however, "Pontus Euxeinos," the Black Sea has devoured many goods and lives, many Greek and Roman ships, many Turkish and Genoese galleys, many English and Russian steamers. And many a little Zaporog vessel sank in the dark waves of its native sea, "on white cliffs dashed to pieces," as is related in the old folk-epics; many a one was driven to far-off hostile Turkish shores, to the destruction of its crews.