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89-647: Unrecognised states: The Black Sea is a marginal mediterranean sea lying between Europe and Asia , east of the Balkans , south of the East European Plain , west of the Caucasus , and north of Anatolia . It is bounded by Bulgaria , Georgia , Romania , Russia , Turkey , and Ukraine . The Black Sea is supplied by major rivers, principally the Danube , Dnieper and Dniester . Consequently, while six countries have

178-513: A halocline that stops at the Cold Intermediate Layer (CIL). This layer is composed of cool, salty surface waters, which are the result of localized atmospheric cooling and decreased fluvial input during the winter months. It is the remnant of the winter surface mixed layer. The base of the CIL is marked by a major pycnocline at about 100–200 metres (330–660 ft), and this density disparity

267-576: A coastline on the sea, its drainage basin includes parts of 24 countries in Europe. The Black Sea, not including the Sea of Azov , covers 436,400 km (168,500 sq mi), has a maximum depth of 2,212 m (7,257 ft), and a volume of 547,000 km (131,000 cu mi). Most of its coasts ascend rapidly. These rises are the Pontic Mountains to the south, bar the southwest-facing peninsulas,

356-709: A decrease in the flux of silicon associated with advection across isopycnal surfaces. This phenomenon demonstrates the potential for localized alterations in Black Sea nutrient-input to have basin-wide effects. Marginal sea There are several terms used for bulges of ocean that result from indentations of land, which overlap in definition, and which are not consistently differentiated: Many features could be considered to be more than one of these, and all of these terms are used in place names inconsistently; especially bays, gulfs, and bights, which can be very large or very small. This list includes large areas of water no matter

445-487: A globe-spanning mid-ocean ridge system, as well as undersea volcanoes , oceanic trenches , submarine canyons , oceanic plateaus and abyssal plains . The mass of the oceans is approximately 1.35 × 10   metric tons , or about 1/4400 of the total mass of the Earth. The oceans cover an area of 3.618 × 10  km with a mean depth of 3,682 m, resulting in an estimated volume of 1.332 × 10  km . Each region of

534-483: A marked vertical stratification and a warm, shallow mixed layer. Day length and insolation intensity also control the extent of the photic zone . Subsurface productivity is limited by nutrient availability, as the anoxic bottom waters act as a sink for reduced nitrate , in the form of ammonia . The benthic zone also plays an important role in Black Sea nutrient cycling, as chemosynthetic organisms and anoxic geochemical pathways recycle nutrients which can be upwelled to

623-501: A rate anywhere from 1 mm to 1 cm every 1000 years. Hydrogenous sediments are uncommon. They only occur with changes in oceanic conditions such as temperature and pressure. Rarer still are cosmogenous sediments. Hydrogenous sediments are formed from dissolved chemicals that precipitate from the ocean water, or along the mid-ocean ridges, they can form by metallic elements binding onto rocks that have water of more than 300 °C circulating around them. When these elements mix with

712-569: A strongly stratified vertical structure. Because of the extreme stratification, it is classified as a salt wedge estuary . Inflow from the Mediterranean Sea through the Bosporus and Dardanelles has a higher salinity and density than the outflow, creating the classic estuarine circulation. This means that the inflow of dense water from the Mediterranean occurs at the bottom of the basin while

801-431: A threat to health—and perhaps even life—for people living on the Black Sea coast. There have been isolated reports of flares on the Black Sea occurring during thunderstorms, possibly caused by lightning igniting combustible gas seeping up from the sea depths. The Black Sea supports an active and dynamic marine ecosystem, dominated by species suited to the brackish , nutrient-rich, conditions. As with all marine food webs,

890-514: A very thick convective bottom layer. 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 discovery of the river, announced on August 1, 2010, was made by scientists at the University of Leeds and is the first of its kind to be identified. The undersea river stems from salty water spilling through

979-490: A weaker mixed assemblage of community development below the seasonal thermocline during summer months, and surface-intensified autumn production. This pattern of productivity is augmented by an Emiliania huxleyi bloom during the late spring and summer months. Since the 1960s, rapid industrial expansion along the Black Sea coastline and the construction of a major dam on the Danube have significantly increased annual variability in

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1068-402: Is absorbed before it can reach deep ocean water, the energy source for deep benthic ecosystems is often organic matter from higher up in the water column that drifts down to the depths. This dead and decaying matter sustains the benthic food chain ; most organisms in the benthic zone are scavengers or detritivores . Seabed topography ( ocean topography or marine topography ) refers to

1157-434: Is a vertical coordinate used in geology, paleontology , oceanography , and petrology (see ocean drilling ). The acronym "mbsf" (meaning "meters below the seafloor") is a common convention used for depths below the seafloor. Sediments in the seabed vary in origin, from eroded land materials carried into the ocean by rivers or wind flow, waste and decompositions of sea creatures, and precipitation of chemicals within

1246-477: Is abundant in the deep sea around hydrothermal vents . Large deep sea communities of marine life have been discovered around black and white smokers – vents emitting chemicals toxic to humans and most vertebrates . This marine life receives its energy both from the extreme temperature difference (typically a drop of 150 degrees) and from chemosynthesis by bacteria . Brine pools are another seabed feature, usually connected to cold seeps . In shallow areas,

1335-580: Is controversial. Environmental advocacy groups such as Greenpeace and the Deep Sea Mining Campaign claimed that seabed mining has the potential to damage deep sea ecosystems and spread pollution from heavy metal-laden plumes. Critics have called for moratoria or permanent bans. Opposition campaigns enlisted the support of some industry figures, including firms reliant on the target metals. Individual countries with significant deposits within their exclusive economic zones (EEZ's) are exploring

1424-447: Is divided into layers or zones, each with typical features of salinity, pressure, temperature and marine life , according to their depth. Lying along the top of the abyssal plain is the abyssal zone , whose lower boundary lies at about 6,000 m (20,000 ft). The hadal zone – which includes the oceanic trenches, lies between 6,000 and 11,000 metres (20,000–36,000 ft) and is the deepest oceanic zone. Depth below seafloor

1513-718: Is divided into two depositional basins—the Western Black Sea and Eastern Black Sea—separated by the Mid-Black Sea High, which includes the Andrusov Ridge, Tetyaev High, and Archangelsky High, extending south from the Crimean Peninsula . The basin includes two distinct relict back-arc basins which were initiated by the splitting of an Albian volcanic arc and the subduction of both the Paleo - and Neo- Tethys oceans, but

1602-461: Is estimated that the global ocean floor holds more than 120 million tons of cobalt, five times the amount found in terrestrial reserves. As of July 2024 , only exploratory licenses have been issued, with no commercial-scale deep sea mining operations yet. The International Seabed Authority (ISA) regulates all mineral-related activities in international waters and has granted 31 exploration licenses so far: 19 for polymetallic nodules, mostly in

1691-700: 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

1780-414: Is not moving so quickly. This means that larger grains of sediment may come together in higher energy conditions and smaller grains in lower energy conditions. Benthos (from Ancient Greek βένθος ( bénthos )  'the depths [of the sea]'), also known as benthon, is the community of organisms that live on, in, or near the bottom of a sea, river , lake , or stream , also known as

1869-532: Is sometimes also considered a marginal sea of the Atlantic. (coast-wise from north to south) (from east to west) While all other seas in the world are defined at least in part by land boundaries, there is only one sea which is defined only by ocean currents: Entities called "seas" which are not divisions of the World Ocean are not included in this list. Excluded are: Seabed The seabed (also known as

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1958-579: Is subject to interannual variability. Outside of the Rim Current, numerous quasi-permanent coastal eddies are formed as a result of upwelling around the coastal apron and "wind curl" mechanisms. The intra-annual strength of these features is controlled by seasonal atmospheric and fluvial variations. During the spring, the Batumi eddy forms in the southeastern corner of the sea. Beneath the surface waters—from about 50 to 100 metres (160 to 330 ft)—there exists

2047-453: Is the major mechanism for isolation of the deep water. Below the pycnocline is the Deep Water mass, where salinity increases to 22.3 PSU and temperatures rise to around 8.9 °C (48.0 °F). The hydrochemical environment shifts from oxygenated to anoxic, as bacterial decomposition of sunken biomass utilizes all of the free oxygen. Weak geothermal heating and long residence time create

2136-480: Is the next most abundant material on the seafloor. Biogenous sediments are biologically produced by living creatures. Sediments made up of at least 30% biogenous material are called "oozes." There are two types of oozes: Calcareous oozes and Siliceous oozes. Plankton grow in ocean waters and create the materials that become oozes on the seabed. Calcareous oozes are predominantly composed of calcium shells found in phytoplankton such as coccolithophores and zooplankton like

2225-561: Is through their descriptive classification. These sediments vary in size, anywhere from 1/4096 of a mm to greater than 256 mm. The different types are: boulder, cobble, pebble, granule, sand, silt, and clay, each type becoming finer in grain. The grain size indicates the type of sediment and the environment in which it was created. Larger grains sink faster and can only be pushed by rapid flowing water (high energy environment) whereas small grains sink very slowly and can be suspended by slight water movement, accumulating in conditions where water

2314-568: The Bosporus ) Burgas , Varna , Constanța , Odesa , Sevastopol , Novorossiysk , Sochi , Poti , Batumi , Trabzon and Samsun . The Black Sea has a positive water balance , with an annual net outflow of 300 km (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

2403-712: 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 farther north. The longest east–west extent is about 1,175 km (730 mi). Important cities along the coast include (clockwise from

2492-881: 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. The largest rivers flowing into

2581-610: The Santonian . Since its initiation, compressional tectonic environments led to subsidence in the basin, interspersed with extensional phases resulting in large-scale volcanism and numerous orogenies , causing the uplift of the Greater Caucasus , Pontides , southern Crimean Peninsula and Balkanides mountain ranges. During the Messinian salinity crisis in the neighboring Mediterranean Sea , water levels fell but without drying up

2670-505: The Turkish Straits ) is out of the Black Sea, water generally flows in both directions simultaneously: Denser, more saline water from the Aegean flows into the Black Sea underneath the less dense, fresher water that flows out of 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

2759-437: The abyssal plain regions of the ocean are relatively flat and covered in many layers of sediments. Sediments in these flat areas come from various sources, including but not limited to: land erosion sediments from rivers, chemically precipitated sediments from hydrothermal vents, Microorganism activity, sea currents eroding the seabed and transporting sediments to the deeper ocean, and phytoplankton shell materials. Where

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2848-453: The benthic zone . This community lives in or near marine or freshwater sedimentary environments , from tidal pools along the foreshore , out to the continental shelf , and then down to the abyssal depths . Many organisms adapted to deep-water pressure cannot survive in the upper parts of the water column . The pressure difference can be very significant (approximately one atmosphere for every 10 metres of water depth). Because light

2937-402: The seafloor , sea floor , ocean floor , and ocean bottom ) is the bottom of the ocean . All floors of the ocean are known as 'seabeds'. The structure of the seabed of the global ocean is governed by plate tectonics . Most of the ocean is very deep, where the seabed is known as the abyssal plain . Seafloor spreading creates mid-ocean ridges along the center line of major ocean basins, where

3026-628: 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 ( / ˈ j uː k s ɪ n / or / ˈ j uː k ˌ s aɪ n / ). During the Ottoman Empire , it was called either Bahr-e Siyah ( Perso-Arabic ) or Karadeniz ( Ottoman Turkish ), both meaning "Black Sea". The International Hydrographic Organization defines

3115-570: The Black Sea Depression they are terrigenous non-carbonate silts , and at the foot of the continental slope turbidite sediments. The Black Sea is the world's largest body of water with a meromictic basin. The deep waters do not mix with the upper layers of water that receive oxygen from the atmosphere. As a result, over 90% of the deeper Black Sea volume is anoxic water. The Black Sea's circulation patterns are primarily controlled by basin topography and fluvial inputs, which result in

3204-487: The Black Sea are: These rivers and their tributaries comprise a 2-million km (0.77-million sq mi) Black Sea drainage basin that covers wholly or partially 24 countries: Unrecognised states: Some islands in the Black Sea belong to Bulgaria, Romania, Turkey, and Ukraine: Short-term climatic variation in the Black Sea region is significantly influenced by the operation of the North Atlantic oscillation ,

3293-584: The Black Sea features a range of trophic groups, with autotrophic algae, including diatoms and dinoflagellates , acting as primary producers. The fluvial systems draining Eurasia and central Europe introduce large volumes of sediment and dissolved nutrients into the Black Sea, but the distribution of these nutrients is controlled by the degree of physiochemical stratification, which is, in turn, dictated by seasonal physiographic development. During winter, strong wind promotes convective overturning and upwelling of nutrients, while high summer temperatures result in

3382-510: The Black Sea from the rest of the global ocean system. The large shelf to the north of the basin is up to 190 km (120 mi) wide and features a shallow apron with gradients between 1:40 and 1:1000. The southern edge around Turkey and the eastern edge around Georgia , however, are typified by a narrow shelf that rarely exceeds 20 km (12 mi) in width and a steep apron that is typically 1:40 gradient with numerous submarine canyons and channel extensions. The Euxine abyssal plain in

3471-469: 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 (both meaning Black Sea) originated during

3560-496: 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. Current names of

3649-516: The Bosporus Strait from the Mediterranean Sea into the Black Sea, where the water has a lower salt content. Because of the anoxic water at depth, organic matter, including anthropogenic artifacts such as boat hulls, are well preserved. During periods of high surface productivity, short-lived algal blooms form organic rich layers known as sapropels . Scientists have reported an annual phytoplankton bloom that can be seen in many NASA images of

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3738-481: The Bosporus is located at 36.5 m (120 ft) below present sea level (deepest spot of the shallowest cross-section in the Bosporus, located in front of Dolmabahçe Palace ) and has a wet section of around 38,000 m (410,000 sq ft). Inflow and outflow current speeds are averaged around 0.3 to 0.4 m/s (1.0 to 1.3 ft/s), but much higher speeds are found locally, inducing significant turbulence and vertical shear. This allows for turbulent mixing of

3827-779: The CCZ; 7 for polymetallic sulphides in mid-ocean ridges ; and 5 for cobalt-rich crusts in the Western Pacific Ocean . There is a push for deep sea mining to commence by 2025, when regulations by the ISA are expected to be completed. Deep sea mining is also possible in the exclusive economic zone (EEZ) of countries, such as Norway , where it has been approved. In 2022, the Cook Islands Seabed Minerals Authority (SBMA) granted three exploration licenses for cobalt-rich polymetallic nodules within their EEZ. Papua New Guinea

3916-562: The N:P:Si ratio in the basin. Coastal areas, accordingly, have seen an increase in the frequency of monospecific phytoplankton blooms, with diatom-bloom frequency increasing by a factor of 2.5 and non-diatom bloom frequency increasing by a factor of 6. The non-diatoms, such as the prymnesiophytes Emiliania huxleyi (coccolithophore), Chromulina sp., and the Euglenophyte Eutreptia lanowii , can out-compete diatom species because of

4005-463: The Rim Current. The Rim Current has a maximum velocity of about 50–100 cm/s (20–39 in/s). Within this feature, two smaller cyclonic gyres operate, occupying the eastern and western sectors of the basin. The Eastern and Western Gyres are well-organized systems in the winter but dissipate into a series of interconnected eddies in the summer and autumn. Mesoscale activity in the peripheral flow becomes more pronounced during these warmer seasons and

4094-462: The amount of cold air arriving from northern regions during winter. Other influencing factors include the regional topography , as depressions and storm systems arriving from the Mediterranean are funneled through the low land around the Bosporus, with the Pontic and Caucasus mountain ranges acting as waveguides, limiting the speed and paths of cyclones passing through the region. The Black Sea

4183-536: The amount of plastic thought – per Jambeck et al., 2015 – to currently enter the oceans annually. Deep sea mining is the extraction of minerals from the seabed of the deep sea . The main ores of commercial interest are polymetallic nodules , which are found at depths of 4–6 km (2.5–3.7 mi) primarily on the abyssal plain . The Clarion–Clipperton zone (CCZ) alone contains over 21 billion metric tons of these nodules, with minerals such as copper , nickel , and cobalt making up 2.5% of their weight. It

4272-485: The balance between sedimentary processes and hydrodynamics however, anthropogenic influences can impact the natural system more than any physical driver. Marine topographies include coastal and oceanic landforms ranging from coastal estuaries and shorelines to continental shelves and coral reefs . Further out in the open ocean, they include underwater and deep sea features such as ocean rises and seamounts . The submerged surface has mountainous features, including

4361-535: 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,

4450-518: The centre of the Black Sea reaches a maximum depth of 2,212 metres (7,257.22 feet) just south of Yalta on the Crimean Peninsula . The Paleo- Euxinian is described by the accumulation of eolian silt deposits (related to the Riss glaciation ) and the lowering of sea levels ( MIS 6, 8 and 10). The Karangat marine transgression occurred during the Eemian Interglacial (MIS 5e). This may have been

4539-636: The climatic mechanisms resulting from the interaction between the north Atlantic and mid-latitude air masses. While the exact mechanisms causing the North Atlantic Oscillation remain unclear, it is thought the climate conditions established in western Europe mediate the heat and precipitation fluxes reaching Central Europe and Eurasia, regulating the formation of winter cyclones , which are largely responsible for regional precipitation inputs and influence Mediterranean sea surface temperatures (SSTs). The relative strength of these systems also limits

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4628-450: The cold sea water they precipitate from the cooling water. Known as manganese nodules , they are composed of layers of different metals like manganese, iron, nickel, cobalt, and copper, and they are always found on the surface of the ocean floor. Cosmogenous sediments are the remains of space debris such as comets and asteroids, made up of silicates and various metals that have impacted the Earth. Another way that sediments are described

4717-509: The commonly used designation in Greek, although in mythological contexts the "true" name Póntos Áxeinos remained favoured. 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

4806-465: The continental slope and the abyssal plain usually has a more gradual descent, and is called the continental rise , which is caused by sediment cascading down the continental slope. The mid-ocean ridge , as its name implies, is a mountainous rise through the middle of all the oceans, between the continents. Typically a rift runs along the edge of this ridge. Along tectonic plate edges there are typically oceanic trenches – deep valleys, created by

4895-597: The deepest waters are collectively known, as a habitat for creatures, as the " benthos ". Most of the seabed throughout the world's oceans is covered in layers of marine sediments . Categorized by where the materials come from or composition, these sediments are classified as either: from land ( terrigenous ), from biological organisms (biogenous), from chemical reactions (hydrogenous), and from space (cosmogenous). Categorized by size, these sediments range from very small particles called clays and silts , known as mud, to larger particles from sand to boulders . Features of

4984-416: The foraminiferans. These calcareous oozes are never found deeper than about 4,000 to 5,000 meters because at further depths the calcium dissolves. Similarly, Siliceous oozes are dominated by the siliceous shells of phytoplankton like diatoms and zooplankton such as radiolarians. Depending on the productivity of these planktonic organisms, the shell material that collects when these organisms die may build up at

5073-502: The highest sea levels reached in the late Pleistocene . Based on this some scholars have suggested that the Crimean Peninsula was isolated from the mainland by a shallow strait during the Eemian Interglacial. The Neoeuxinian transgression began with an inflow of waters from the Caspian Sea . Neoeuxinian deposits are found in the Black Sea below −20 m (−66 ft) water depth in three layers. The upper layers correspond with

5162-516: The late 1980s. Additionally, an alien species—the warty comb jelly ( Mnemiopsis leidyi )—established itself in the basin, exploding from a few individuals to an estimated biomass of one billion metric tons. The change in species composition in Black Sea waters also has consequences for hydrochemistry, as calcium-producing coccolithophores influence salinity and pH, although these ramifications have yet to be fully quantified. In central Black Sea waters, silicon levels also reduced significantly, due to

5251-404: The limited availability of silicon, a necessary constituent of diatom frustules. As a consequence of these blooms, benthic macrophyte populations were deprived of light, while anoxia caused mass mortality in marine animals. Overfishing during the 1970s further compounded the decline in macrophytes, while the invasive ctenophore Mnemiopsis reduced the biomass of copepods and other zooplankton in

5340-676: 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

5429-444: The mantle circulation movement from the mid-ocean mountain ridge to the oceanic trench. Hotspot volcanic island ridges are created by volcanic activity, erupting periodically, as the tectonic plates pass over a hotspot. In areas with volcanic activity and in the oceanic trenches there are hydrothermal vents – releasing high pressure and extremely hot water and chemicals into the typically freezing water around it. Deep ocean water

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5518-448: The oceans have a common structure, created by common physical phenomena, mainly from tectonic movement, and sediment from various sources. The structure of the oceans, starting with the continents, begins usually with a continental shelf , continues to the continental slope – which is a steep descent into the ocean, until reaching the abyssal plain – a topographic plain , the beginning of the seabed, and its main area. The border between

5607-715: The others being the Red Sea , the White Sea and the Yellow Sea . The earliest known name of the Black Sea is the Sea of Zalpa, so called by both the Hattians and their conquerors, the Hittites . The Hattic city of Zalpa was "situated probably at or near the estuary of the Marrassantiya River, the modern Kızıl Irmak , on the Black Sea coast." The principal Greek name Póntos Áxeinos

5696-450: The outflow of fresher Black Sea surface-water into the Sea of Marmara occurs near the surface. According to Gregg (2002), the outflow is 16,000 cubic metres per second (570,000 cubic feet per second) or around 500 cubic kilometres per year (120 cubic miles per year), and the inflow is 11,000 m/s (390,000 cu ft/s) or around 350 km/a (84 cu mi/a). The following water budget can be estimated: The southern sill of

5785-501: The peak of the Khvalinian transgression, on the shelf shallow-water sands and coquina mixed with silty sands and brackish-water fauna, and inside the Black Sea Depression hydrotroilite silts. The middle layers on the shelf are sands with brackish-water mollusc shells. Of continental origin, the lower level on the shelf is mostly alluvial sands with pebbles, mixed with less common lacustrine silts and freshwater mollusc shells . Inside

5874-485: The photic zone, enhancing productivity. In total, the Black Sea's biodiversity contains around one-third of the Mediterranean's and is experiencing natural and artificial invasions or "Mediterranizations". The main phytoplankton groups present in the Black Sea are dinoflagellates , diatoms , coccolithophores and cyanobacteria . Generally, the annual cycle of phytoplankton development comprises significant diatom and dinoflagellate-dominated spring production, followed by

5963-662: The preservation of ancient shipwrecks which have been found in the Black Sea, which 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

6052-487: The region. As a result of these characteristics the Black Sea has gained interest from the field of marine archaeology , as ancient shipwrecks in excellent states of preservation have been discovered, such as the Byzantine wreck Sinop D , located in the anoxic layer off the coast of Sinop, Turkey . Modelling shows that, in the event of an asteroid impact on the Black Sea, the release of hydrogen sulfide clouds would pose

6141-462: The sea are usually equivalents of the English name "Black Sea", including these given in the countries bordering the sea: Such names have not yet been shown conclusively to predate the 13th century. In Greece , the historical name "Euxine Sea", which holds a different literal meaning (see below), is still widely used: The Black Sea is one of four seas named in English after common color terms –

6230-537: The sea water itself, including some from outer space. There are four basic types of sediment of the sea floor: Terrigenous sediment is the most abundant sediment found on the seafloor. Terrigenous sediments come from the continents. These materials are eroded from continents and transported by wind and water to the ocean. Fluvial sediments are transported from land by rivers and glaciers, such as clay, silt, mud, and glacial flour. Aeolian sediments are transported by wind, such as dust and volcanic ash. Biogenous sediment

6319-622: The sea. The collision between the Eurasian and African plates and the westward escape of the Anatolian block along the North Anatolian and East Anatolian faults dictates the current tectonic regime, which features enhanced subsidence in the Black Sea basin and significant volcanic activity in the Anatolian region. These geological mechanisms, in the long term, have caused the periodic isolations of

6408-482: The seabed , and these satellite-derived maps are used extensively in the study and exploration of the ocean floor. In 2020 scientists created what may be the first scientific estimate of how much microplastic currently resides in Earth's seafloor , after investigating six areas of ~3 km depth ~300 km off the Australian coast. They found the highly variable microplastic counts to be proportionate to plastic on

6497-468: The seabed are governed by the physics of sediment transport and by the biology of the creatures living in the seabed and in the ocean waters above. Physically, seabed sediments often come from the erosion of material on land and from other rarer sources, such as volcanic ash . Sea currents transport sediments, especially in shallow waters where tidal energy and wave energy cause resuspension of seabed sediments. Biologically, microorganisms living within

6586-440: The seabed can host sediments created by marine life such as corals, fish, algae, crabs, marine plants and other organisms. The seabed has been explored by submersibles such as Alvin and, to some extent, scuba divers with special equipment. Hydrothermal vents were discovered in 1977 by researchers using an underwater camera platform. In recent years satellite measurements of ocean surface topography show very clear maps of

6675-404: The seabed has typical features such as common sediment composition, typical topography, salinity of water layers above it, marine life, magnetic direction of rocks, and sedimentation . Some features of the seabed include flat abyssal plains , mid-ocean ridges , deep trenches , and hydrothermal vents . Seabed topography is flat where layers of sediments cover the tectonic features. For example,

6764-400: The seabed is slightly shallower than the surrounding abyssal plain. From the abyssal plain, the seabed slopes upward toward the continents and becomes, in order from deep to shallow, the continental rise , slope , and shelf . The depth within the seabed itself, such as the depth down through a sediment core , is known as the "depth below seafloor". The ecological environment of the seabed and

6853-501: The seabed sediments change seabed chemistry. Marine organisms create sediments, both within the seabed and in the water above. For example, phytoplankton with silicate or calcium carbonate shells grow in abundance in the upper ocean, and when they die, their shells sink to the seafloor to become seabed sediments. Human impacts on the seabed are diverse. Examples of human effects on the seabed include exploration, plastic pollution, and exploitation by mining and dredging operations. To map

6942-592: The seabed, ships use acoustic technology to map water depths throughout the world. Submersible vehicles help researchers study unique seabed ecosystems such as hydrothermal vents . Plastic pollution is a global phenomenon, and because the ocean is the ultimate destination for global waterways, much of the world's plastic ends up in the ocean and some sinks to the seabed. Exploitation of the seabed involves extracting valuable minerals from sulfide deposits via deep sea mining, as well as dredging sand from shallow environments for construction and beach nourishment . Most of

7031-411: The seafloor is actively spreading and sedimentation is relatively light, such as in the northern and eastern Atlantic Ocean , the original tectonic activity can be clearly seen as straight line "cracks" or "vents" thousands of kilometers long. These underwater mountain ranges are known as mid-ocean ridges . Other seabed environments include hydrothermal vents, cold seeps, and shallow areas. Marine life

7120-410: The shape of the land ( topography ) when it interfaces with the ocean. These shapes are obvious along coastlines, but they occur also in significant ways underwater. The effectiveness of marine habitats is partially defined by these shapes, including the way they interact with and shape ocean currents , and the way sunlight diminishes when these landforms occupy increasing depths. Tidal networks depend on

7209-491: The southern shoreline before Greek colonisation due to its difficult navigation and hostile barbarian natives (7.3.6), and that the name was changed to "hospitable" after the Milesians colonised 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 colour symbolism representing

7298-519: The subject. Some children's play songs include elements such as "There's a hole at the bottom of the sea", or "A sailor went to sea... but all that he could see was the bottom of the deep blue sea". On and under the seabed are archaeological sites of historic interest, such as shipwrecks and sunken towns. This underwater cultural heritage is protected by the UNESCO Convention on the Protection of

7387-412: The surface and the angle of the seafloor slope. By averaging the microplastic mass per cm , they estimated that Earth's seafloor contains ~14 million tons of microplastic – about double the amount they estimated based on data from earlier studies – despite calling both estimates "conservative" as coastal areas are known to contain much more microplastic pollution . These estimates are about one to two times

7476-464: The term used in the name. The largest terrestrial seas, in decreasing order of area, are: Seas may be considered marginal between ocean and land, or between oceans in which case they may be treated as marginal parts of either. There is no single ultimate authority on the matter. (clockwise from 180°) In addition to the marginal seas listed in the three subsections below, the Arctic Ocean itself

7565-651: The timings of these events remain uncertain. Arc volcanism and extension occurred as the Neo-Tethys Ocean subducted under the southern margin of Laurasia during the Mesozoic . Uplift and compressional deformation took place as the Neotethys continued to close. Seismic surveys indicate that rifting began in the Western Black Sea in the Barremian and Aptian followed by the formation of oceanic crust 20 million years later in

7654-406: The two layers. Surface water leaves the Black Sea with a salinity of 17 practical salinity units (PSU) and reaches the Mediterranean with a salinity of 34 PSU. Likewise, an inflow of the Mediterranean with salinity 38.5 PSU experiences a decrease to about 34 PSU. Mean surface circulation is cyclonic ; waters around the perimeter of the Black Sea circulate in a basin-wide shelfbreak gyre known as

7743-403: The water column. Related technologies include robotic mining machines, as surface ships, and offshore and onshore metal refineries. Wind farms, solar energy, electric vehicles , and battery technologies use many of the deep-sea metals. Electric vehicle batteries are the main driver of the critical metals demand that incentivizes deep sea mining. The environmental impact of deep sea mining

7832-452: 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,

7921-511: Was the first country to approve a deep sea mining permit for the Solwara 1 project, despite three independent reviews highlighting significant gaps and flaws in the environmental impact statement. The most common commercial model of deep sea mining proposed involves a caterpillar-track hydraulic collector and a riser lift system bringing the harvested ore to a production support vessel with dynamic positioning , and then depositing extra discharge down

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