Black Sea
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Satellite view of the Black Sea, taken by NASA MODIS. |
The
Black Sea is an inland
sea between southeastern
Europe and
Anatolia that is actually a distant arm of the
Atlantic Ocean by way of the
Mediterranean Sea. It is connected to the Mediterranean by the
Bosphorus and the
Sea of Marmara, and to the
Sea of Azov by the
Strait of Kerch.
There is a net inflow of seawater through the Bosporus, 200 km³ per year. There is an inflow of freshwater from the surrounding areas, especially central and middle-eastern Europe, totalling 320 km³ per year. The most important river entering the Black Sea is the
Danube. The Black Sea has an area of
422,000 km² and a maximum depth of 2210 m.
Countries bordering on the Black Sea are
Turkey,
Bulgaria,
Romania,
Ukraine,
Russia, and
Georgia (including the breakaway region of
Abkhazia). The
Crimean
peninsula is a Ukrainian autonomous republic.
Important cities along the coast include:
Istanbul,
Burgas,
Varna,
Constanţa,
Yalta,
Odessa,
Sevastopol,
Kerch,
Novorossiysk,
Sochi,
Sukhumi,
Poti,
Batumi,
Trabzon,
Samsun.
Modern names of the Sea are universally translations of Μαύρη Θάλασσα "Black Sea",
Turkish Kara Deniz,
Russian Чёрное море,
Bulgarian Черно море, Cherno more,
Georgian შავი ზღვა, shavi zghva,
Ukrainian Chorne More,
Romanian Marea Neagră,
Laz Ucha Zuğa (or simple Zuğa "Sea"),
Ubykh . This type cannot be traced to an earlier date than the
13th century, but there are indications that it may be considerably older, cf. below.
Strabo (1.2.10) reports that in antiquity, the Black Sea was often just called "the Sea" (
pontos), just like
Homer was often simply called "the Poet". For the most part, Graeco-Roman tradition refers to the Black Sea as (
Euxeinos Pontos) "Hospitable sea". This is a
euphemism replacing an earlier
Pontos Axeinos "Inhospitable Sea", first attested in
Pindar (early 5th century BC). Strabo (7.3.6) thinks that the Black Sea was called "inhospitable" before Greek colonization because it was difficult to navigate, and because its shores were inhabited by savage tribes, and that the name was changed to "hospitable" after the
Milesians had colonized, as it were making it part of the Greek civilization. It is, however, likely that the name
Axeinos arose by
popular etymology from an Iranian
axšaina- meaning "dark"; the designation "Black Sea" would, after all, go back to Antiquity. The motive for the name may be an ancient assignment of colors to the direction of the compass, "black" referring to the north, and "red" referring to the south.
Herodotus on one occasion uses
Red Sea and "Southern Sea" interchangeably. Cf. Schmitt 1996.
Another possible explanation comes from the color of the Black Sea's deep waters. Being further north than the
Mediterranean Sea and much less saline, the
microalgae concentration is much more rich, hence the dark color.
One
Bulgarian understanding of the name is that the sea used to be quite stormy. Some sources stipulate that that goes back to the time of
Noah's Ark. The
Black Sea deluge theory is based on that idea.
The Black Sea forms in an enclosed basin, located between south-eastern Europe and
Asia Minor. The basin was formed during the
Miocene orogenies which uplifted the mountain ranges and divided the ancient
Tethys Ocean into several brackish basins, including the
Sarmatic Sea. The
Caspian,
Azov,
Aral and Black Seas are the remnants of this evaporated basin.
The basin is divided into two sub-basins by a convexity extending south from the
Crimean peninsula. The north-west of the basin is characterized by a relatively large shelf up to 190 km wide, which has a relatively shallow apron with gradients between 1:40 and 1:1000. The southern edge around
Turkey and the western edge around
Georgia however, are typified by a shelf that rarely exceeds 20km in width and an apron that is typically 1:40 gradient with numerous submarine canyons and channel extensions. The Euxine abyssal plain in the centre of the Black Sea reaches a maximum depth of 2,206m just south of
Yalta on the Crimean peninsula. The basin is connected to the
Mediterranean Sea via the Turkish Straits System (TSS) in the south-west, which includes the
Bosphorus and
Dardanelles straits and the
Sea of Marmara. The Black Sea is connected to the
Sea of Azov in the north-east via the
Kerch straits.
The Black Sea is the world's largest
meromictic basin, with 90% of its volume occupied by
anoxic waters. The current hydrochemical configuration is primarily controlled by basin topography and
fluvial inputs, which result in a strongly stratified vertical structure and a positive water balance. The upper layers are generally cooler, less dense and less salty that the deeper waters, as they are fed by large fluvial systems, whereas the deep waters originate from the warm, salty waters of the Mediterranean. This influx of dense water from Mediterranean is balanced by an outflow of fresher Black Sea surface-water into the Marmara Sea, maintaining the stratification and
salinity levels.
The surface water has an average salinity of 18-18.5 ppt and contains
oxygen and other nutrients required to sustain biotic activity. These waters circulate in a basin-wide anti-cyclonic shelfbreak
gyre known as the Rim Current which transports water round the perimeter of the Black Sea. Within this feature, two smaller cyclonic gyres operate, occupying the eastern and western sectors of the basin. Outside the Rim Current, numerous quasi-permanent coastal eddies are formed due to upwelling around the coastal apron and ‘wind curl' mechanisms. The intra-annual strength of these features is controlled by seasonal atmospheric and fluvial variations. Sea Surface Temperature of the surface waters varies seasonally from 8°C to 30°C.
Directly beneath the surface waters the Cold Intermediate Layer (CIL) is found. This layer is composed of cool, salty surface waters, which are the result of localised atmospheric cooling and decreased fluvial input during the winter months. The production of this water is focussed in the centre of the major gyres and on the NW shelf and as the water is not dense enough to penetrate the deep waters,
isopycnal advection occurs, dispersing the water across the entire basin. The base of the CIL is marked by a major
thermocline,
halocline and
pycnocline at ~100-200m and this density disparity is the major cause of deep-water isolation.
Below the pycnocline, salinity increases to 22-22.5 ppt and temperatures rise to ~8.5°C. The hydrochemical environment shifts from oxygenated to anoxic, as bacterial decomposition of sunken biomass utilises all of the free oxygen. Certain species of
extremophile bacteria are capable of using
sulfate (SO
42−) in the
oxidation of organic material, which leads to the creation of hydrogen sulphide (H
2S). This reacts with seawater to produce
sulfuric acid (H
2SO
4). This enables the precipitation of
sulfides such as iron-sulphides like
pyrite,
greigite and iron-monosulphide as well as the dissolution of carbonate matter such as
Calcium carbonate (CaCO
3) found in shells. Organic matter, including anthropogenic artefacts such as boat hulls, are well preserved. During periods of high surface productivity, short-lived algal blooms cause organic rich layer known as
sapropels to occur.
While it is agreed that the Black Sea has been a freshwater
lake (at least in upper layers) with a considerably lower level during the
last glaciation, its postglacial development into a marine sea is still a subject of intensive study and debate. There are catastrophic scenarios such as put forward by
William Ryan and
Walter Pitman as well as models emphasizing a more gradual transition to saline conditions and transgression in the Black Sea.
They are based on different theories about the level the freshwater lake had reached by the time the Mediterranean Sea was high enough to flow over the
Dardanelles and the
Bosporus. On the other hand, a study of the sea floor on the Aegean side shows that in the 8th millennium BCE there was a large flow of fresh water out of the Black Sea (
New Scientist,
4 May 2002, p. 13).
In a series of expeditions, a team of marine archeologists led by Robert Ballard identified what appeared to be ancient shorelines, freshwater snail shells, drowned river valleys, tool-worked timbers, and man-made structures in roughly 300 feet (100 m) of water off the Black Sea coast of modern
Turkey.
Radiocarbon dating of freshwater mollusk remains indicated an age of about 7,000 years.
In 1997, William Ryan and Walter Pitman from
Columbia University published a theory that a massive flood through the
Bosporus occurred in ancient times. They claim that the Black and
Caspian Seas were vast freshwater lakes, but that about
5600 BC, the
Mediterranean spilled over a rocky sill at the Bosporus, creating the current communication between the Black and Mediterranean Seas. Subsequent work has been done both to support and to discredit this theory, and it remains an active subject of debate among archaeologists. This has led some to associate this catastrophe with prehistoric
flood myths.
The steppes to the north of the Black Sea have been suggested as the original homeland (
Urheimat) of the speakers of the
Proto-Indo-European language, (PIE) the progenitor of the
Indo-European language family, by some scholars (see
Kurgan; others move the heartland further east towards the
Caspian Sea, yet others to
Anatolia).
The name 'Black Sea' (initially
Pontos Axeinos, "inhospitable sea", later renamed
Pontos Euxeinos, "hospitable sea" to gain the sea's god's favor) was coined by the
Ancient Greek navigators, because of the unusual dark color, compared with the
Mediterranean Sea. Visibility in the Black Sea is on average approximately 5 meters (15 feet), as compared to up to 35 meters (100 feet) in the Mediterranean. The water however is as blue as any other sea on bright, clear days. The land at the eastern end of the Black Sea,
Colchis (now
Georgia), marked for the Greeks an edge of the known world.
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Photo of the Black Sea near Sochi, taken in 1915. |
See also the
Balkans Regional organizations and
Post-Soviet Regional organizations*
Anoxic event*
Black Sea deluge theory*
Bulgarian Black Sea Coast*
Romanian Black Sea Coast*
Ancomah* Charles King,
The Black Sea: A History, 2004, ISBN 0199241619
* William Ryan and Walter Pitman,
Noah's Flood, 1999, ISBN 0684859203
* Neal Ascherson,
Black Sea (Vintage 1996), ISBN 0099593718
*
Özhan Öztürk. Karadeniz: Ansiklopedik Sözlük (Black Sea: Encyclopedic Dictionary). 2 Cilt (2 Volumes). Heyamola Publishing. Istanbul.2005 ISBN 975-6121-00-9.
* Rüdiger Schmitt, "Considerations on the Name of the Black Sea", in:
Hellas und der griechische Osten (Saarbrücken 1996), pp. 219-224
*
Black Sea Environment and Marine Life - Learning Pages*
The Center for Black Sea Archaeology*
The Black Sea Trade Project*
Ecology of Black Sea*
Earth from Space: Black Sea*
September 2006 Black Sea Symposium in Rize, Turkey*
Black Sea Photographs*
Rare Coins of the Northern Black Sea Area*
BLACKSEAFOR
