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86-698: The Sohm Abyssal Plain is in the North Atlantic and has an area of around 900,000 square kilometres (350,000 sq mi). It is located off the coast of the Canadian Maritime provinces and New England in the United States . The region was named for Rudolf von Willemoes-Suhm , a German naturalist on the Challenger expedition in the late-19th Century. 34°N 55°W  /  34°N 55°W  / 34; -55 This article about

172-404: A supercritical fluid at such temperatures. At a barometric pressure of 218 atmospheres , the critical point of water is 375 °C. At a depth of 3,000 meters, the barometric pressure of sea water is more than 300 atmospheres (as salt water is denser than fresh water). At this depth and pressure, seawater becomes supercritical at a temperature of 407 °C ( see image ). However

258-482: A 2–3 cm specimen (still unclassified) of polychaete at the bottom of the Challenger Deep on 31 May 2009. There are more than 10,000 described species of polychaetes; they can be found in nearly every marine environment. Some species live in the coldest ocean temperatures of the hadal zone, while others can be found in the extremely hot waters adjacent to hydrothermal vents. Within the abyssal and hadal zones,

344-530: A contrasting degree of intra-trench endemism and inter-trench similarities at a higher taxonomic level. Only a relatively small number of fish species are known from the hadal zone, including certain grenadiers, cutthroat eels , pearlfish , cusk-eels , snailfish and eelpouts . Due to the extreme pressure, the theoretical maximum depth for vertebral fish may be about 8,000–8,500 m (26,200–27,900 ft), below which teleosts would be hyperosmotic , assuming trimethylamine N-oxide requirements follow

430-524: A cosmopolitan distribution. One example of this would be protozoan foraminiferans , certain species of which are distributed from the Arctic to the Antarctic. Other faunal groups, such as the polychaete worms and isopod crustaceans, appear to be endemic to certain specific plains and basins. Many apparently unique taxa of nematode worms have also been recently discovered on abyssal plains. This suggests that

516-510: A depth of 6,000 metres down to approximately 11,034 meters, at the very bottom of the Mariana Trench, the deepest point on planet Earth. Abyssal plains are typically in the abyssal zone, at depths from 3,000 to 6,000 metres. The table below illustrates the classification of oceanic zones: Oceanic crust, which forms the bedrock of abyssal plains, is continuously being created at mid-ocean ridges (a type of divergent boundary ) by

602-428: A depth of 90 m (300 ft), whilst pressure only doubles as an organism moves from 6,000 to 11,000 m (20,000 to 36,000 ft). Over a geological time scale , trenches can become accessible as previously stenobathic (limited to a narrow depth range) fauna evolve to become eurybathic (adapted to a wider range of depths), such as grenadiers and natantian prawns. Trench communities do, nevertheless, display

688-603: A hundred to a thousand years. The structure of abyssal ecosystems is strongly influenced by the rate of flux of food to the seafloor and the composition of the material that settles. Factors such as climate change , fishing practices , and ocean fertilization have a substantial effect on patterns of primary production in the euphotic zone . Animals absorb dissolved oxygen from the oxygen-poor waters. Much dissolved oxygen in abyssal plains came from polar regions that had melted long ago. Due to scarcity of oxygen, abyssal plains are inhospitable for organisms that would flourish in

774-456: A process known as decompression melting . Plume -related decompression melting of solid mantle is responsible for creating ocean islands like the Hawaiian islands , as well as the ocean crust at mid-ocean ridges. This phenomenon is also the most common explanation for flood basalts and oceanic plateaus (two types of large igneous provinces ). Decompression melting occurs when the upper mantle

860-528: A specific oceanic location or ocean current is a stub . You can help Misplaced Pages by expanding it . Abyssal plain An abyssal plain is an underwater plain on the deep ocean floor , usually found at depths between 3,000 and 6,000 metres (9,800 and 19,700 ft). Lying generally between the foot of a continental rise and a mid-ocean ridge , abyssal plains cover more than 50% of the Earth 's surface. They are among

946-440: Is partially melted into magma as it moves upwards under mid-ocean ridges. This upwelling magma then cools and solidifies by conduction and convection of heat to form new oceanic crust . Accretion occurs as mantle is added to the growing edges of a tectonic plate , usually associated with seafloor spreading . The age of oceanic crust is therefore a function of distance from the mid-ocean ridge. The youngest oceanic crust

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1032-608: Is 6,500 m (21,300 ft). Few unmanned submersibles are capable of descending to maximum hadal depths. The deepest diving unmanned submersibles have included the Kaikō (lost at sea in 2003), the ABISMO , the Nereus (lost at sea in 2014), and the Haidou-1 . On July 12, 2022, Dr. Dawn Wright , chief scientist of Esri , completed a scientific expedition to Challenger Deep. Dawn served as

1118-467: Is adequate light to support photosynthesis by phytoplankton and plants, is referred to as the euphotic zone (also referred to as the epipelagic zone , or surface zone ). The lower portion of the photic zone, where the light intensity is insufficient for photosynthesis, is called the dysphotic zone (dysphotic means "poorly lit" in Greek). The dysphotic zone is also referred to as the mesopelagic zone , or

1204-459: Is an error of about 22 meters at this depth). A rare but important terrain feature found in the bathyal, abyssal and hadal zones is the hydrothermal vent. In contrast to the approximately 2 °C ambient water temperature at these depths, water emerges from these vents at temperatures ranging from 60 °C up to as high as 464 °C. Due to the high barometric pressure at these depths, water may exist in either its liquid form or as

1290-496: Is at the mid-ocean ridges, and it becomes progressively older, cooler and denser as it migrates outwards from the mid-ocean ridges as part of the process called mantle convection . The lithosphere , which rides atop the asthenosphere , is divided into a number of tectonic plates that are continuously being created and consumed at their opposite plate boundaries . Oceanic crust and tectonic plates are formed and move apart at mid-ocean ridges. Abyssal hills are formed by stretching of

1376-513: Is being formed. Another unusual feature found in the abyssal and hadal zones is the cold seep , sometimes called a cold vent . This is an area of the seabed where seepage of hydrogen sulfide , methane and other hydrocarbon -rich fluid occurs, often in the form of a deep-sea brine pool . The first cold seeps were discovered in 1983, at a depth of 3200 meters in the Gulf of Mexico . Since then, cold seeps have been discovered in many other areas of

1462-440: Is considerably less than 1% of surface irradiance, extends from the base of the euphotic zone to about 1,000 metres. Extending from the bottom of the photic zone down to the seabed is the aphotic zone , a region of perpetual darkness. Since the average depth of the ocean is about 4,300 metres, the photic zone represents only a tiny fraction of the ocean's total volume. However, due to its capacity for photosynthesis,

1548-548: Is in the Japan Trench , at a depth of 7700 meters. Probably the most important ecological characteristic of abyssal ecosystems is energy limitation. Abyssal seafloor communities are considered to be food limited because benthic production depends on the input of detrital organic material produced in the euphotic zone, thousands of meters above. Most of the organic flux arrives as an attenuated rain of small particles (typically, only 0.5–2% of net primary production in

1634-649: Is named after HMS Challenger , whose researchers made the first recordings of its depth on 23 March 1875 at station 225 . The reported depth was 4,475 fathoms (8184 meters) based on two separate soundings. On 1 June 2009, sonar mapping of the Challenger Deep by the Simrad EM120 multibeam sonar bathymetry system aboard the R/V Kilo Moana indicated a maximum depth of 10971 meters (6.82 miles). The sonar system uses phase and amplitude bottom detection, with an accuracy of better than 0.2% of water depth (this

1720-428: Is projected to directly disrupt 300–800 km of seafloor per year and disturb the benthic fauna over an area 5–10 times that size due to redeposition of suspended sediments. Thus, over the 15-year projected duration of a single mining operation, nodule mining might severely damage abyssal seafloor communities over areas of 20,000 to 45,000 km (a zone at least the size of Massachusetts ). Limited knowledge of

1806-433: Is the bathyal zone , extending from a depth of 1,000 metres down to 3,000 metres, with water temperature decreasing from 12 °C (54 °F) to 4 °C (39 °F) as depth increases. Next is the abyssal zone , extending from a depth of 3,000 metres down to 6,000 metres. The final zone includes the deep oceanic trenches, and is known as the hadal zone . This, the deepest oceanic zone, extends from

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1892-408: Is the basic building block of organic matter . Photosynthesis in turn requires energy from sunlight to drive the chemical reactions that produce organic carbon. The stratum of the water column nearest the surface of the ocean ( sea level ) is referred to as the photic zone . The photic zone can be subdivided into two different vertical regions. The uppermost portion of the photic zone, where there

1978-711: The Asellota suborder of benthic isopods from the abyssal plains of the Angola Basin in the South Atlantic Ocean . In 2003, De Broyer et al. collected some 68,000 peracarid crustaceans from 62 species from baited traps deployed in the Weddell Sea , Scotia Sea , and off the South Shetland Islands . They found that about 98% of the specimens belonged to the amphipod superfamily Lysianassoidea , and 2% to

2064-795: The World Ocean , including the Monterey Submarine Canyon just off Monterey Bay , California, the Sea of Japan , off the Pacific coast of Costa Rica , off the Atlantic coast of Africa, off the coast of Alaska, and under an ice shelf in Antarctica . Though the plains were once assumed to be vast, desert -like habitats, research over the past decade or so shows that they teem with a wide variety of microbial life. However, ecosystem structure and function at

2150-483: The abyssal plains . Although they have evolved adaptations to high pressure and low temperatures such as lower metabolism, intra-cellular protein-stabilising osmolytes , and unsaturated fatty acids in cell membrane phospholipids , there is no consistent relationship between pressure and metabolic rate in these communities. Increased pressure can instead constrain the ontogenic or larval stages of organisms. Pressure increases ten-fold as an organism moves from sea level to

2236-674: The continental margins along submarine canyons into deeper water. The rest is composed chiefly of pelagic sediments . Metallic nodules are common in some areas of the plains, with varying concentrations of metals, including manganese , iron , nickel , cobalt , and copper . There are also amounts of carbon, nitrogen, phosphorus and silicon, due to material that comes down and decomposes. Owing in part to their vast size, abyssal plains are believed to be major reservoirs of biodiversity . They also exert significant influence upon ocean carbon cycling , dissolution of calcium carbonate , and atmospheric CO 2 concentrations over time scales of

2322-746: The fauna of the hadal zone can be broadly placed into two groups: the hadobenthic species (compare benthic ) living on or at the seabottom/sides of trenches, and the hadopelagic species (compare pelagic ) living in the open water. The deepest ocean trenches are considered the least explored and most extreme marine ecosystems . They are characterized by complete lack of sunlight, low temperatures, nutrient scarcity, and extremely high hydrostatic pressures. The major sources of nutrients and carbon are fallout from upper layers, drifts of fine sediment, and landslides. Most organisms are scavengers and detrivores . Over 400 species are currently known from hadal ecosystems, many of which possess physiological adaptations to

2408-567: The oil blowout involved in the Deepwater Horizon oil spill in the Gulf of Mexico originates from a wellhead only 1500 meters below the ocean surface, it nevertheless illustrates the kind of environmental disaster that can result from mishaps related to offshore drilling for oil and gas. Sediments of certain abyssal plains contain abundant mineral resources, notably polymetallic nodules . These potato-sized concretions of manganese, iron, nickel, cobalt, and copper, distributed on

2494-469: The taxonomy , biogeography and natural history of deep sea communities prevents accurate assessment of the risk of species extinctions from large-scale mining. Data acquired from the abyssal North Pacific and North Atlantic suggest that deep-sea ecosystems may be adversely affected by mining operations on decadal time scales. In 1978, a dredge aboard the Hughes Glomar Explorer , operated by

2580-420: The twilight zone . Its lowermost boundary is at a thermocline of 12 °C (54 °F), which, in the tropics generally lies between 200 and 1,000 metres. The euphotic zone is somewhat arbitrarily defined as extending from the surface to the depth where the light intensity is approximately 0.1–1% of surface sunlight irradiance , depending on season , latitude and degree of water turbidity . In

2666-401: The 432 organisms collected, the overwhelming majority of the sample consisted of simple, soft-shelled foraminifera, with others representing species of the complex, multi-chambered genera Leptohalysis and Reophax . Overall, 85% of the specimens consisted of soft-shelled allogromiids . This is unusual compared to samples of sediment-dwelling organisms from other deep-sea environments, where

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2752-475: The 46 individual hadal habitats worldwide is less than 0.25% of the world's seafloor , yet trenches account for over 40% of the ocean's depth range. Most hadal habitat is found in the Pacific Ocean , the deepest of the conventional oceanic divisions. Historically, the hadal zone was not recognized as distinct from the abyssal zone , although the deepest sections were sometimes called "ultra-abyssal". During

2838-704: The American mining consortium Ocean Minerals Company (OMCO), made a mining track at a depth of 5000 meters in the nodule fields of the CCFZ. In 2004, the French Research Institute for Exploitation of the Sea ( IFREMER ) conducted the Nodinaut expedition to this mining track (which is still visible on the seabed) to study the long-term effects of this physical disturbance on the sediment and its benthic fauna. Samples taken of

2924-734: The Pacific Ocean. Abyssal plains are typically covered by deep sea, but during parts of the Messinian salinity crisis much of the Mediterranean Sea 's abyssal plain was exposed to air as an empty deep hot dry salt-floored sink. The landmark scientific expedition (December 1872 – May 1876) of the British Royal Navy survey ship HMS Challenger yielded a tremendous amount of bathymetric data, much of which has been confirmed by subsequent researchers. Bathymetric data obtained during

3010-608: The Pacific nodule province that is currently under exploration for its mineral potential. Eight commercial contractors are currently licensed by the International Seabed Authority (an intergovernmental organization established to organize and control all mineral-related activities in the international seabed area beyond the limits of national jurisdiction ) to explore nodule resources and to test mining techniques in eight claim areas , each covering 150,000 km . When mining ultimately begins, each mining operation

3096-409: The abyssal plain, the lifeforms discovered in the Challenger Deep may represent independent taxa from those shallower ecosystems. This preponderance of soft-shelled organisms at the Challenger Deep may be a result of selection pressure. Millions of years ago, the Challenger Deep was shallower than it is now. Over the past six to nine million years, as the Challenger Deep grew to its present depth, many of

3182-436: The abyssal plain. Although genetic studies are lacking, at least six of these species are thought to be eurybathic (capable of living in a wide range of depths), having been reported as occurring from the sublittoral to abyssal depths. A large number of the polyplacophorans from great depths are herbivorous or xylophagous , which could explain the difference between the distribution of monoplacophorans and polyplacophorans in

3268-519: The areas around submarine hydrothermal vents and cold seeps have by far the greatest biomass and biodiversity per unit area. Fueled by the chemicals dissolved in the vent fluids, these areas are often home to large and diverse communities of thermophilic , halophilic and other extremophilic prokaryotic microorganisms (such as those of the sulfide-oxidizing genus Beggiatoa ), often arranged in large bacterial mats near cold seeps. In these locations, chemosynthetic archaea and bacteria typically form

3354-478: The base of the food chain. Although the process of chemosynthesis is entirely microbial, these chemosynthetic microorganisms often support vast ecosystems consisting of complex multicellular organisms through symbiosis . These communities are characterized by species such as vesicomyid clams , mytilid mussels , limpets , isopods, giant tube worms , soft corals , eelpouts , galatheid crabs , and alvinocarid shrimp . The deepest seep community discovered thus far

3440-494: The black smoker category, on the Mid-Atlantic Ridge near Ascension Island . They are presumed to have been active since an earthquake shook the region in 2002. These vents have been observed to vent phase-separated , vapor-type fluids. In 2008, sustained exit temperatures of up to 407 °C were recorded at one of these vents, with a peak recorded temperature of up to 464 °C. These thermodynamic conditions exceed

3526-437: The clearest ocean water, the euphotic zone may extend to a depth of about 150 metres, or rarely, up to 200 metres. Dissolved substances and solid particles absorb and scatter light, and in coastal regions the high concentration of these substances causes light to be attenuated rapidly with depth. In such areas the euphotic zone may be only a few tens of metres deep or less. The dysphotic zone, where light intensity

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3612-421: The concept of continental drift in the theory of plate tectonics. The flat appearance of mature abyssal plains results from the blanketing of this originally uneven surface of oceanic crust by fine-grained sediments, mainly clay and silt. Much of this sediment is deposited from turbidity currents that have been channeled from the continental margins along submarine canyons down into deeper water. The remainder of

3698-516: The course of the Challenger expedition enabled scientists to draw maps, which provided a rough outline of certain major submarine terrain features, such as the edge of the continental shelves and the Mid-Atlantic Ridge . This discontinuous set of data points was obtained by the simple technique of taking soundings by lowering long lines from the ship to the seabed. The Challenger expedition

3784-528: The course of time. Vent growths on the order of 30 cm (1 ft) per day have been recorded.[11] An April 2007 exploration of the deep-sea vents off the coast of Fiji found those vents to be a significant source of dissolved iron (see iron cycle). Hydrothermal vents in the deep ocean typically form along the mid-ocean ridges, such as the East Pacific Rise and the Mid-Atlantic Ridge. These are locations where two tectonic plates are diverging and new crust

3870-416: The critical point of seawater, and are the highest temperatures recorded to date from the seafloor. This is the first reported evidence for direct magmatic - hydrothermal interaction on a slow-spreading mid-ocean ridge. The initial stages of a vent chimney begin with the deposition of the mineral anhydrite. Sulfides of copper, iron, and zinc then precipitate in the chimney gaps, making it less porous over

3956-504: The deep ocean has fostered adaptive radiations . The taxonomic composition of the nematode fauna in the abyssal Pacific is similar, but not identical to, that of the North Atlantic. A list of some of the species that have been discovered or redescribed by CeDAMar can be found here . Eleven of the 31 described species of Monoplacophora (a class of mollusks ) live below 2000 meters. Of these 11 species, two live exclusively in

4042-592: The deep seafloor have historically been poorly studied because of the size and remoteness of the abyss. Recent oceanographic expeditions conducted by an international group of scientists from the Census of Diversity of Abyssal Marine Life (CeDAMar) have found an extremely high level of biodiversity on abyssal plains, with up to 2000 species of bacteria, 250 species of protozoans , and 500 species of invertebrates ( worms , crustaceans and molluscs ), typically found at single abyssal sites. New species make up more than 80% of

4128-521: The deepest dive record set by Piccard and Walsh. Cameron holds the record for the deepest solo dive. In June 2012, the Chinese manned submersible Jiaolong was able to reach 7,020 m (23,030 ft) deep in the Mariana Trench, making it the deepest diving manned research submersible. This range surpasses that of the previous record holder, the Japanese-made Shinkai , whose maximum depth

4214-671: The deepest known part of the ocean located in the Mariana Trench , was accomplished in 1960 by Jacques Piccard and Don Walsh . They reached a maximum depth of 10,911 metres (35,797 ft) in the bathyscaphe Trieste . James Cameron also reached the bottom of Mariana Trench in March 2012 using the Deepsea Challenger . The descent of the Deepsea Challenger reached a depth of 10,908 metres (35,787 ft), slightly less than

4300-495: The deepest living fish ever recorded. Other fish of the abyssal zone include the fishes of the family Ipnopidae , which includes the abyssal spiderfish ( Bathypterois longipes ), tripodfish ( Bathypterois grallator ), feeler fish ( Bathypterois longifilis ), and the black lizardfish ( Bathysauropsis gracilis ). Some members of this family have been recorded from depths of more than 6000 meters. CeDAMar scientists have demonstrated that some abyssal and hadal species have

4386-530: The development of sonar technology. Acoustic sounding equipment was developed which could be operated much more rapidly than the sounding lines, thus enabling the German Meteor expedition aboard the German research vessel Meteor (1925–27) to take frequent soundings on east-west Atlantic transects. Maps produced from these techniques show the major Atlantic basins, but the depth precision of these early instruments

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4472-475: The early 1950s, the Danish Galathea II and Soviet Vityaz expeditions separately discovered a distinct shift in the life at depths of 6,000–7,000 m (20,000–23,000 ft) not recognized by the broad definition of the abyssal zone. The term "hadal" was first proposed in 1956 by Anton Frederik Bruun to describe the parts of the ocean deeper than 6,000 m (20,000 ft), leaving abyssal for

4558-841: The euphotic zone), which decreases inversely with water depth. The small particle flux can be augmented by the fall of larger carcasses and downslope transport of organic material near continental margins. In addition to their high biodiversity, abyssal plains are of great current and future commercial and strategic interest. For example, they may be used for the legal and illegal disposal of large structures such as ships and oil rigs , radioactive waste and other hazardous waste , such as munitions . They may also be attractive sites for deep-sea fishing , and extraction of oil and gas and other minerals . Future deep-sea waste disposal activities that could be significant by 2025 include emplacement of sewage and sludge , carbon sequestration , and disposal of dredge spoils . As fish stocks dwindle in

4644-588: The extreme environmental conditions. There are high levels of endemism , and noteworthy examples of gigantism in amphipods , mysids , and isopods and dwarfism in nematodes , copepods , and kinorhynchs . Marine life decreases with depth, both in abundance and biomass , but there is a wide range of metazoan organisms in the hadal zone, mostly benthos , including fish , sea cucumber , bristle worms , bivalves , isopods , sea anemones , amphipods , copepods , decapod crustaceans and gastropods . Most of these trench communities probably originated from

4730-410: The flattest, smoothest, and least explored regions on Earth. Abyssal plains are key geologic elements of oceanic basins (the other elements being an elevated mid-ocean ridge and flanking abyssal hills ). The creation of the abyssal plain is the result of the spreading of the seafloor (plate tectonics) and the melting of the lower oceanic crust . Magma rises from above the asthenosphere (a layer of

4816-460: The hadal zone are certain bacteria that are able to metabolize hydrogen and methane released by rock and seawater reactions ( serpentinization ), or hydrogen sulfide released from cold seeps . Some of these bacteria are symbiotic , for example living inside the mantle of certain thyasirid and vesicomyid bivalves. Otherwise the first link in the hadal food web are heterotroph organisms that feed on marine snow , both fine particles and

4902-468: The hadal zone has gained widespread recognition and many continue to use the first proposed limit of 6,000 m (20,000 ft), it has been observed that 6,000–7,000 m (20,000–23,000 ft) represents a gradual transition between the abyssal and hadal zones, leading to the suggestion of placing the limit in the middle, at 6,500 m (21,300 ft). Among others, this intermediate limit has been adopted by UNESCO . Similar to other depth ranges,

4988-621: The hadal zone. The greatest number of monoplacophorans are from the eastern Pacific Ocean along the oceanic trenches. However, no abyssal monoplacophorans have yet been found in the Western Pacific and only one abyssal species has been identified in the Indian Ocean. Of the 922 known species of chitons (from the Polyplacophora class of mollusks), 22 species (2.4%) are reported to live below 2000 meters and two of them are restricted to

5074-710: The increase in salinity at this depth pushes the water closer to its critical point. Thus, water emerging from the hottest parts of some hydrothermal vents, black smokers and submarine volcanoes can be a supercritical fluid , possessing physical properties between those of a gas and those of a liquid . Sister Peak (Comfortless Cove Hydrothermal Field, 4°48′S 12°22′W  /  4.800°S 12.367°W  / -4.800; -12.367 , elevation −2996 m), Shrimp Farm and Mephisto (Red Lion Hydrothermal Field, 4°48′S 12°23′W  /  4.800°S 12.383°W  / -4.800; -12.383 , elevation −3047 m), are three hydrothermal vents of

5160-561: The isopod family Cirolanidae . Half of these species were collected from depths of greater than 1000 meters. In 2005, the Japan Agency for Marine-Earth Science and Technology (JAMSTEC) remotely operated vehicle, KAIKO , collected sediment core from the Challenger Deep. 432 living specimens of soft-walled foraminifera were identified in the sediment samples. Foraminifera are single-celled protists that construct shells. There are an estimated 4,000 species of living foraminifera. Out of

5246-435: The mid-oceanic ridges, is mostly basalt at shallow levels and has a rugged topography . The roughness of this topography is a function of the rate at which the mid-ocean ridge is spreading (the spreading rate). Magnitudes of spreading rates vary quite significantly. Typical values for fast-spreading ridges are greater than 100 mm/yr, while slow-spreading ridges are typically less than 20 mm/yr. Studies have shown that

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5332-401: The observed approximate linear relationship with depth. Some invertebrates do occur deeper, such as bigfin squid , certain polynoid worms, myriotrochid sea cucumbers, turrid snails and pardaliscid amphipods in excess of 10,000 m (33,000 ft). In addition, giant protists known as Xenophyophora ( foraminifera ) live at these depths. The only known primary producers in

5418-414: The occasional carcass. The hadal zone can reach far below 6,000 m (20,000 ft) deep; the deepest known extends to 10,911 m (35,797 ft). At such depths, the pressure in the hadal zone exceeds 1,100 standard atmospheres (110  MPa ; 16,000  psi ). Lack of light and extreme pressure makes this part of the ocean difficult to explore. The exploration of the hadal zone requires

5504-422: The oceanic lithosphere. Consumption or destruction of the oceanic lithosphere occurs at oceanic trenches (a type of convergent boundary , also known as a destructive plate boundary) by a process known as subduction . Oceanic trenches are found at places where the oceanic lithospheric slabs of two different plates meet, and the denser (older) slab begins to descend back into the mantle. At the consumption edge of

5590-415: The oxygen-enriched waters above. Deep sea coral reefs are mainly found in depths of 3,000 meters and deeper in the abyssal and hadal zones . Abyssal plains were not recognized as distinct physiographic features of the sea floor until the late 1940s and, until recently, none had been studied on a systematic basis. They are poorly preserved in the sedimentary record , because they tend to be consumed by

5676-432: The parts at 4,000–6,000 m (13,000–20,000 ft). The name refers to Hades , the ancient Greek god of the underworld . About 94% of the hadal zone is found in subduction trenches. Depths in excess of 6,000 m (20,000 ft) are generally in ocean trenches , but there are also trenches at shallower depths. These shallower trenches lack the distinct shift in lifeforms and are therefore not hadal. Although

5762-612: The percentage of organic-walled foraminifera ranges from 5% to 20% of the total. Small organisms with hard calciferous shells have trouble growing at extreme depths because the water at that depth is severely lacking in calcium carbonate. The giant (5–20 cm) foraminifera known as xenophyophores are only found at depths of 500-10,000 metres, where they can occur in great numbers and greatly increase animal diversity due to their bioturbation and provision of living habitat for small animals. While similar lifeforms have been known to exist in shallower oceanic trenches (>7,000 m) and on

5848-596: The photic zone has the greatest biodiversity and biomass of all oceanic zones. Nearly all primary production in the ocean occurs here. Life forms which inhabit the aphotic zone are often capable of movement upwards through the water column into the photic zone for feeding. Otherwise, they must rely on material sinking from above , or find another source of energy and nutrition, such as occurs in chemosynthetic archaea found near hydrothermal vents and cold seeps . The aphotic zone can be subdivided into three different vertical regions, based on depth and temperature. First

5934-580: The plate (the oceanic trench), the oceanic lithosphere has thermally contracted to become quite dense, and it sinks under its own weight in the process of subduction. The subduction process consumes older oceanic lithosphere, so oceanic crust is seldom more than 200 million years old. The overall process of repeated cycles of creation and destruction of oceanic crust is known as the Supercontinent cycle , first proposed by Canadian geophysicist and geologist John Tuzo Wilson . New oceanic crust, closest to

6020-501: The research vessel by a cable) or autonomous (freely moving). Cameras and manipulators on submersibles allow researchers to observe and take samples of sediment and organisms. Failures of submersibles under the immense pressure at hadal zone depths have occurred. HROV Nereus is thought to have imploded at a depth of 9,990 meters while exploring the Kermadec Trench in 2014. The first manned exploration to reach Challenger Deep ,

6106-463: The seafloor at depths of greater than 4000 meters, are of significant commercial interest. The area of maximum commercial interest for polymetallic nodule mining (called the Pacific nodule province ) lies in international waters of the Pacific Ocean, stretching from 118°–157°, and from 9°–16°N, an area of more than 3 million km . The abyssal Clarion-Clipperton Fracture Zone (CCFZ) is an area within

6192-513: The sediment comprises chiefly dust (clay particles) blown out to sea from land, and the remains of small marine plants and animals which sink from the upper layer of the ocean, known as pelagic sediments . The total sediment deposition rate in remote areas is estimated at two to three centimeters per thousand years. Sediment-covered abyssal plains are less common in the Pacific Ocean than in other major ocean basins because sediments from turbidity currents are trapped in oceanic trenches that border

6278-471: The slower the spreading rate, the rougher the new oceanic crust will be, and vice versa. It is thought this phenomenon is due to faulting at the mid-ocean ridge when the new oceanic crust was formed. These faults pervading the oceanic crust, along with their bounding abyssal hills, are the most common tectonic and topographic features on the surface of the Earth. The process of seafloor spreading helps to explain

6364-458: The species present in the sediment of that ancient biosphere were unable to adapt to the increasing water pressure and changing environment. Those species that were able to adapt may have been the ancestors of the organisms currently endemic to the Challenger Deep. Polychaetes occur throughout the Earth's oceans at all depths, from forms that live as plankton near the surface, to the deepest oceanic trenches. The robot ocean probe Nereus observed

6450-454: The subduction process. Due to darkness and a water pressure that can reach about 750 times atmospheric pressure (76 megapascal), abyssal plains are not well explored. The ocean can be conceptualized as zones , depending on depth, and presence or absence of sunlight . Nearly all life forms in the ocean depend on the photosynthetic activities of phytoplankton and other marine plants to convert carbon dioxide into organic carbon , which

6536-521: The summer of 1947 to identify and describe the first abyssal plain. This plain, south of Newfoundland , is now known as the Sohm Abyssal Plain . Following this discovery many other examples were found in all the oceans. The Challenger Deep is the deepest surveyed point of all of Earth's oceans; it is at the south end of the Mariana Trench near the Mariana Islands group. The depression

6622-531: The superficial sediment revealed that its physical and chemical properties had not shown any recovery since the disturbance made 26 years earlier. On the other hand, the biological activity measured in the track by instruments aboard the crewed submersible bathyscaphe Nautile did not differ from a nearby unperturbed site. This data suggests that the benthic fauna and nutrient fluxes at the water–sediment interface has fully recovered. Download coordinates as: Hadal zone The cumulative area occupied by

6708-428: The thousands of seafloor invertebrate species collected at any abyssal station, highlighting our heretofore poor understanding of abyssal diversity and evolution. Richer biodiversity is associated with areas of known phytodetritus input and higher organic carbon flux. Abyssobrotula galatheae , a species of cusk eel in the family Ophidiidae , is among the deepest-living species of fish. In 1970, one specimen

6794-423: The upper mantle ), and as this basaltic material reaches the surface at mid-ocean ridges, it forms new oceanic crust, which is constantly pulled sideways by spreading of the seafloor. Abyssal plains result from the blanketing of an originally uneven surface of oceanic crust by fine-grained sediments , mainly clay and silt . Much of this sediment is deposited by turbidity currents that have been channelled from

6880-589: The upper ocean, deep-sea fisheries are increasingly being targeted for exploitation. Because deep sea fish are long-lived and slow growing, these deep-sea fisheries are not thought to be sustainable in the long term given current management practices. Changes in primary production in the photic zone are expected to alter the standing stocks in the food-limited aphotic zone. Hydrocarbon exploration in deep water occasionally results in significant environmental degradation resulting mainly from accumulation of contaminated drill cuttings , but also from oil spills . While

6966-418: The use of instruments that are able to withstand pressures of up to a thousand or more atmospheres. A few haphazard and non-standard tools have been used to collect limited, but valuable, information about the basic biology of a few hadal organisms. Manned and unmanned submersibles , however, can be used to study the depths in greater detail. Unmanned robotic submersibles may be remotely operated (connected to

7052-456: The world's oceans. Peracarid crustaceans, including isopods, are known to form a significant part of the macrobenthic community that is responsible for scavenging on large food falls onto the sea floor. In 2000, scientists of the Diversity of the deep Atlantic benthos (DIVA 1) expedition (cruise M48/1 of the German research vessel RV Meteor III ) discovered and collected three new species of

7138-549: Was trawled from a depth of 8370 meters in the Puerto Rico Trench . The animal was dead, however, upon arrival at the surface. In 2008, the hadal snailfish ( Pseudoliparis amblystomopsis ) was observed and recorded at a depth of 7700 meters in the Japan Trench . In December 2014 a type of snailfish was filmed at a depth of 8145 meters, followed in May 2017 by another sailfish filmed at 8178 meters. These are, to date,

7224-636: Was followed by the 1879–1881 expedition of the Jeannette , led by United States Navy Lieutenant George Washington DeLong . The team sailed across the Chukchi Sea and recorded meteorological and astronomical data in addition to taking soundings of the seabed. The ship became trapped in the ice pack near Wrangel Island in September 1879, and was ultimately crushed and sunk in June 1881. The Jeannette expedition

7310-689: Was followed by the 1893–1896 Arctic expedition of Norwegian explorer Fridtjof Nansen aboard the Fram , which proved that the Arctic Ocean was a deep oceanic basin, uninterrupted by any significant land masses north of the Eurasian continent. Beginning in 1916, Canadian physicist Robert William Boyle and other scientists of the Anti-Submarine Detection Investigation Committee ( ASDIC ) undertook research which ultimately led to

7396-412: Was not sufficient to reveal the flat featureless abyssal plains. As technology improved, measurement of depth, latitude and longitude became more precise and it became possible to collect more or less continuous sets of data points. This allowed researchers to draw accurate and detailed maps of large areas of the ocean floor. Use of a continuously recording fathometer enabled Tolstoy & Ewing in

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