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98-712: The Hikurangi Plateau covers approximately 400,000 km (150,000 sq mi) and reaches 2,500–3,000 m (8,200–9,800 ft) below sea level. Hikurangi Plateau is cut by the Hikurangi Channel, a 2000 km abyssal channel that starts at Kaikōura and runs along the Hikurangi Trough as far as the Māhia Peninsula before crossing the plateau and ending in the South-west Pacific abyssal plain. Two models have been proposed for

196-458: A channel-levee system as a single channel with a levee at each side. These levees are formed by the overspilling and flow stripping of turbidity currents . These are most likely to occur during sea level lowstands. A collection of these channels and levees along with overbank sediments form a channel-levee complex. They can be V or U in shape, have the presence or lack of depositional margins, highly sinuous or straight. Ian Kane advocates

294-404: 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

392-489: 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,

490-426: A channel-belt. The external levee forms during the evolution of a genetically related channel-belt (or slope valley, channel fairway) by flows that partially spill out of their confinement. External levees can confine adjacent channel belts to form levee-confined systems. External levees may be much less sinuous than the levees of an individual channel-levee system as they do not follow one particular channel but may be

588-533: 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

686-517: 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

784-609: A depth of 65 km (40 mi). With these missing portions of the plateau added to it, the Hikurangi Plateau originally must have covered 800,000 km (310,000 sq mi), an area similar to that of the Manihiki Plateau 3,000 km (1,900 mi) to the north. The Hikurangi Plateau first subducted beneath New Zealand around 100 Ma during the Gondwana collision and it is currently subducting

882-603: 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

980-578: A minimum average sinuosity of between 1.2 and 1.15. Difficulty with rigorous application of these values is that relatively straight channels may locally exceed them and some sinuous channels may display peak sinuosity values well in excess. The sinuosity of submarine channels is a characteristic instantly recognizable as being shared with fluvial systems. In recent years there are increasingly mixed opinions in academic literature as to how far they are analogous to each other with some feeling that such notions of similarity should not hold. The best description

1078-461: 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

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1176-415: A random wandering. In most cases, the wandering and changes in sinuosity is as a result of external forces. As a result of this, PJeff Peakall advocates the avoidance of the term meandering to describe this sinuosity, a phrase used to describe similar sinuosity observed in terrestrial fluvial systems. There seems to be a potential consensus that truly sinuous channel can be defined as one that displays

1274-406: A result of changes in seafloor topography due to salt/shale tectonics or fault movement. The other alternative they suggest is through undefined “depositional processes”. One potential process may be as a result of heterogeneous infilling of the older channel forming an offset conduit for later flows. Whatever the process this stacking plays an important role in aggradational systems and potentially

1372-482: A result of salt/shale tectonics, whether through diapirism or subsurface folding. Underwater channels can carry underwater waves . 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

1470-599: A second Late Cretaceous magmatic event contemporaneous with volcanism on New Zealand and associated with the final break-up of Gondwana. The Hikurangi Plateau has been partly subducted under the Chatham Rise , probably during the Cretaceous, and probably resulting in a slab more than 150 km (93 mi) long. The western margin of the plateau is actively subducting under the North Island of New Zealand to

1568-555: A second time as part of the convergence between the Pacific and Australian plates. These subducted parts are reaching 37–140 km (23–87 mi) into the mantle beneath the North Island and northern South Island . The extent of the Hikurangi Plateau slab suggests that it has played a significant role in the geology of New Zealand during the past 100 Ma. The Southern Alps in central South Island are being uplifted along

1666-401: A significant number of papers which take concepts even further. There are numerous terms that are used to describe the features contained in this study, including geo-body , channel complex , channel storey , channel complex set , and confined channel complex system . These cover single channels, a single channel and associated sediments or multiple channels grouped. Flood (2001) defines

1764-440: 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

1862-471: 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

1960-459: 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

2058-496: 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

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2156-517: 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

2254-414: Is believed to be somewhat rare in occurrence within turbidite systems. Vertical migration is exhibited in submarine channels systems in the form of channel stacking. As flows in channels subside, channels are infilled with sediment. When the flow is re-initiated, there is then a slight shift laterally in the flow thalweg causing a displaced incision. Mayall suggests that this vertical movement could be as

2352-440: 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,

2450-412: Is controlled by an unknown constant that could not be found experimentally. The morphology and topography of the slope that any turbidite channel crosses is inevitably going to affect the geometry of the channel. This can result in subtle changes in channel path to major diversions in channel flow. Topographic influences can come in the form of the surface expression of faults or changes in topography as

2548-554: 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

2646-494: Is most analogous with its terrestrial counterpart. It consists of erosion on the outerbank and deposition on the inner bank as a point bar. However, there are significant dissimilarities the biggest in that submarine channels can exhibit both lateral and vertical migration. Fluvial systems do not exhibit this vertical component. Lateral accretion packages are believed to form as a result of depositional rather than topographical forcing. This lateral migration only style of sinuosity

2744-662: 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

2842-411: Is one of the leading controls in the formation of levee confined complexes. In terms of sinuosity, Mayall shows that this vertical migration occurs on the outward sides of bends reinforcing any pre-existing curvature. Aggradational channels commonly form where the slope is “below grade.” This results in the deposition of broad, amalgamated and highly sand rich channels which are significantly affected by

2940-428: 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

3038-567: Is that the two are similar in some ways but more variable and complex in other. This applies to both the geometry of morphological features, the processes involved in forming them as well as the character of the deposits formed. Mike Mayall provides the best summary that discusses the causes of sinuosity. Factors involve: flow dynamics such as flow density and flow velocity; and the depth of the current relative to topography; and topographic and morphological controls such; shape channel cross section , slope topography, erosive base at flow onset and

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3136-433: 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

3234-408: 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

3332-747: 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

3430-721: The Cretaceous silent period (84–121 Ma) before colliding with Gondwana. This later model (which does not exclude its initiation from a mantle plume) is the only one consistent with the current best fit Pacific Plate reference frame tectonics model where the Osbourn Trough is modelled as a spreading centre between the Manihiki Plate and the Hikurangi Plate which later became fixed components of today's Pacific Plate. A 2010 study of isotopic data supported

3528-469: The Earth 's surface. They are among 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

3626-776: 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

3724-455: The asthenosphere (a layer of 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

3822-674: 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

3920-575: 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

4018-479: 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

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4116-420: 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

4214-401: 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

4312-474: The 7.8  M w 1931 Hawke's Bay earthquake . Abyssal channel Abyssal channels (also, deep-sea channels , underwater channels ) are channels in Earth's sea floor . They are formed by fast-flowing floods of turbid water caused by avalanches near the channel's head, with the sediment carried by the water causing a build-up of the surrounding abyssal plains . Submarine channels and

4410-732: 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

4508-762: 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

4606-620: 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

4704-409: 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

4802-436: 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

4900-519: 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

4998-478: 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

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5096-502: 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

5194-437: 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

5292-421: 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

5390-515: The confinement of the channel-belt. The flows which build internal levees may interact with the main confining surface, i.e., the external levees, and/or the channel-belt erosion surface , and are liable to erosion by the migration or avulsions of channel thalwegs , and the overbank passage of large flows not confined by the internal levees. As a consequence of lateral migration, internal levees may be better preserved on inner bends. Internal levees form only when confinement has been established, through

5488-476: The construction of external levees and/or the degradation and entrenchment of the composite erosion surface of the channel-belt, or confined within canyons . Internal levees may form distinct wedges of sediment where enough space is available; where space is limited, i.e., where overspill from underfit channels interacts with external levees or erosional confinement, overspill deposits may appear superficially similar to terrace deposits, which are widely identified in

5586-530: 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

5684-536: 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

5782-416: 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

5880-511: 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

5978-596: 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

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6076-495: 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

6174-541: 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

6272-436: The effects of both lateral stacking and lateral accretion. Compared to their terrestrial cousins, the scale of submarine systems observed in seismic sections, aerial photos and rock outcrops are in no way comparable. As expected with this significant difference in scale, the dynamics of turbid current flows within submarine channels are significantly different from fluvial systems. These differences in dynamics and scale are due to

6370-841: 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

6468-461: The formation of Hikurangi. It could be derived from the mantle plume that caused the break-up of Gondwana and the separation of Zealandia from Antarctica 107 Ma. Alternatively, it could have formed together with other Pacific plateaux around 120 Ma as part of the Ontong Java - Manihiki -Hikurangi mega-plateau, in which case Hikurangi must have drifted thousands of kilometres during

6566-641: 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

6664-710: 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

6762-567: 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

6860-427: The least understood sedimentary processes. The effect of Earth's rotation causes more sediment to build up on one side of the channel than on the other. What constitutes a channel is not straight forward. Different terms are used on a per study basis, all of which have similar but not quite interchangeable definitions. There have been efforts to produce an up-to-date, holistic view, but even since then there has been

6958-579: The mega-plateau or " Greater Ontong Java Event " model. The study added several basins as remains of this LIP event, including the north-west part of the Central Pacific, Nauru, East Mariana, and Lyra basins — submarine volcanism that must have covered 1% of Earth's surface and had a dramatic impact on life on Earth. The samples so far taken from the three plateaus are all consistent with ages of initial formation about 124 million years ago. There are, nevertheless, traces in seamounts on Hikurangi of

7056-435: 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

7154-406: The much lower density contrast between the flow and the host fluid is much lower in submarine channels than that of open channel flows with a free surface. This causes the flow to be significantly super-elevated about the channel margin causing overspill and building the levees. Lateral migration and accretion plays an important part in fluvial systems. It is the feature of submarine channels that

7252-448: The ocean floor. Often, they coalesce and overlap to form channel levee complexes which are the building blocks of many major submarine fans . This makes them one of several geological processes responsible for the transport of coarse-grained sediment into deep water, as well as being a chief conduit for the transfer of carbon from the continental shelf to the deeper parts of the continental margins. They do, however, remain one of

7350-422: 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

7448-415: 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

7546-612: 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

7644-596: 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

7742-587: 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

7840-555: The plate boundary there, a fault zone which parallels the western edge of the slab of the Hikurangi Plateau. The Australian and Pacific plates converge obliquely in the Tonga-Kermadec-Hikurangi subduction zone . The Hikurangi Plateau alters this subduction beneath North Island, at the Hikurangi subduction zone, where the buoyancy of the slab has resulted in the exposure of a forearc and hence earthquakes such as

7938-467: The product of overspill from one or more channels or channel-levee systems meandering within the wider channel-belt. The levee crest is the highest point of the external levee, and runs parallel to the course of the channel-belt, separating the external levees into outer external levees and inner external levees. Internal levees are constructional features fed by flows that partially spilled out of channelised confinement, but were largely unable to escape

8036-468: 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

8134-513: 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

8232-516: The slope morphology. The channel width versus slope relationship is control by the Froude number of flows along the channel. When Froude numbers are low (<1.0) channel widths remain constant, however when Froude number oscillate around unity, channel widths fall rapidly with channel-floor slope. This provides a mechanism for generating channel widths capable of maintaining near-critical flow by channel narrowing and enhanced sedimentation. This behavior

8330-423: 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

8428-458: 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

8526-454: 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

8624-465: The subsurface. Sinuosity in submarine channels is a feature regularly observed on seismic maps. It can vary between occasional low amplitude bends to highly sinuous, densely looping channels. Channel sinuosity results in significant migration lateral and affects continuity of facies associated with both channel sediments and surrounding deep water sediments. Although it is not always clear how these sinuosities evolve, they typically do not result from

8722-599: 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

8820-428: 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

8918-431: The turbidite systems which form them are responsible for the accumulation of most sandstone deposits found on continental slopes and have proven to be one of the most common types of hydrocarbon reservoirs found in these regions. Submarine channels and their flanking levees are commonly referred to as channel levee systems . They are significant geomorphological features that may run for thousands of kilometres across

9016-589: 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

9114-408: The use of the terms internal levee and external levee to avoid confusion in the literature concerning the use of "inner" and "outer" levees. To help encourage this unification of phrases into a clearer architectural hierarchy, this study will use Kane's nomenclature. External levees are a dominantly depositional body forming a constructional wedge of sediment that thins perpendicularly away from

9212-461: 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

9310-560: 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,

9408-656: 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

9506-722: 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

9604-412: 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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