The Black Sea is a marginal mediterranean sea of the Atlantic Ocean lying between Europe and Asia. It lies to the east of the Balkans in Southeast Europe, south of the East European Plain in Eastern Europe; and north and west of the South Caucasus and Anatolia in Western Asia. The Black Sea is supplied by major rivers, principally the Danube, Dnieper, and Don. The waters of many countries drain into the sea beyond the six that share its coast.
The Black Sea covers 436,400 km2 (168,500 sq mi) (not including the Sea of Azov), 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, bar 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 further north. The longest east–west extent is about 1,175 km (730 mi). Important cities along the coast include Istanbul, Odessa, Varna, Samsun, Sochi, Sevastopol, Constanța, Trabzon, Novorossiysk, Burgas, and Batumi.
The Black Sea is bordered by Bulgaria, Georgia, Romania, Russia, Turkey, and Ukraine. It 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, generally water is flowing in both directions simultaneously. Denser, more saline water from the Aegean flows into the Black Sea underneath the less dense, fresher outflowing water from 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.
The Black Sea ultimately drains into the Mediterranean Sea, via the Turkish Straits and the Aegean Sea. 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. To the north, the Black Sea is connected to the Sea of Azov by the Kerch Strait.
The water level has varied significantly over geological time. Due to these variations in the water level in the basin, the surrounding shelf and associated aprons have sometimes been dry land. At certain critical water levels, connections with surrounding water bodies can become established. It is through the most active of these connective routes, the Turkish Straits, that the Black Sea joins the world ocean. During geological periods when this hydrological link was not present, the Black Sea was an endorheic basin, operating independently of the global ocean system (similar to the Caspian Sea today). Currently, the Black Sea water level is relatively high; thus, water is being exchanged with the Mediterranean. The Black Sea undersea river is a current of particularly saline water flowing through the Bosporus Strait and along the seabed of the Black Sea, the first of its kind discovered.
Historical names and etymology
The principal Greek name Póntos Áxeinos is generally accepted to be a rendering of the Iranian word *axšaina- ("dark colored"). Ancient Greek voyagers adopted the name as Á-xe(i)nos, identified with the Greek word áxeinos (inhospitable). The name Πόντος Ἄξεινος Póntos Áxeinos (Inhospitable Sea), first attested in Pindar (c. 475 BC), was considered an ill omen and was euphemized to its opposite, Εὔξεινος Πόντος Eúxeinos Póntos (Hospitable Sea), also first attested in Pindar. This became the commonly used designation in Greek, although in mythological contexts the "true" name Póntos Áxeinos remained favored.
Strabo's Geographica (1.2.10) reports that in antiquity, the Black Sea was often simply called "the Sea" (ὁ πόντος ho Pontos). He thought that the sea was called the "Inhospitable Sea Πόντος Ἄξεινος Póntos Áxeinos by the inhabitants of the Pontus region of the southern shoreline before Greek colonization due to its difficult navigation and hostile barbarian natives (7.3.6), and that the name was changed to "hospitable" after the Milesians colonized the region, bringing it into the Greek world.
Popular supposition derives "Black Sea" from the dark color of the water or climatic conditions. Some scholars understand the name to be derived from a system of color symbolism representing the cardinal directions, with black or dark for north, red for south, white for west, and green or light blue for east. Hence "Black Sea" meant "Northern Sea". According to this scheme, the name could only have originated with a people living between the northern (black) and southern (red) seas: this points to the Achaemenids (550–330 BC).
In the Greater Bundahishn, a Middle Persian Zoroastrian scripture, the Black Sea is called Siyābun. In the tenth-century Persian geography book Hudud al-'Alam, the Black Sea is called Georgian Sea (daryā-yi Gurz). The Georgian Chronicles use the name zğua sperisa ზღუა სპერისა (Sea of Speri) after the Kartvelian tribe of Speris or Saspers. Other modern names such as Chyornoye more and Karadeniz originated in the 13th century. A 1570 map Asiae Nova Descriptio from Abraham Ortelius's Theatrum Orbis Terrarum labels the sea Mar Maggior (Great Sea), compare Latin mare major.
English writers of the 18th century often used Euxine Sea (/ˈjuːksɪn/ or /ˈjuːkˌsaɪn/). During the Ottoman Empire, it was called either Bahr-e Siyah or Karadeniz, both meaning "Black Sea" in Turkish, with the former consisting of Perso-Arabic loanwords.
The International Hydrographic Organization defines the limits of the Black Sea as follows:
On the Southwest. The Northeastern limit of the Sea of Marmara [A line joining Cape Rumili with Cape Anatoli (41°13'N)]. In the Kertch Strait. A line joining Cape Takil and Cape Panaghia (45°02'N).
The area surrounding the Black Sea is commonly referred to as the Black Sea Region. Its northern part lies within the Chernozem belt (black soil belt) which goes from eastern Croatia (Slavonia), along the Danube (northern Serbia, northern Bulgaria (Danubian Plain) and southern Romania (Wallachian Plain)) to northeast Ukraine and further across the Central Black Earth Region and southern Russia into Siberia.
The littoral zone of the Black Sea is often referred to as the Pontic littoral or Pontic zone.
The largest bays of the Black Sea are Karkinit Bay in Ukraine; the Gulf of Burgas in Bulgaria; Dnieprovski Bay and Dniestrovski Bay, both in Ukraine; and Sinop Bay and Samsun Bay, both in Turkey.