TheMariana Trench is anoceanic trench located in the western Pacific Ocean, about 200 kilometres (124 mi) east of theMariana Islands; it is thedeepest oceanic trench on Earth. It is crescent-shaped and measures about 2,550 km (1,580 mi) in length and 69 km (43 mi) in width. The maximum known depth is 10,984 ± 25 metres (36,037 ± 82 ft; 6,006 ± 14 fathoms; 6.825 ± 0.016 mi) at the southern end of a small slot-shaped valley in its floor known as theChallenger Deep.[1] The deepest point of the trench is more than 2 km (1.2 mi) farther from sea level than the peak ofMount Everest.[a]
At the bottom of the trench at around 11,000 metres below the sea surface, thewater column above exerts a pressure of 1,086 bar (15,750 psi), approximately 1,071.8 times thestandard atmospheric pressure at sea level or eight tons per square inch.[4]
The Mariana Trench is named after the nearbyMariana Islands,[citation needed] which are named Las Marianas in honor of Spanish QueenMariana of Austria.[10] The islands are part of theisland arc that is formed on an over-riding plate, called the Mariana plate (also named for the islands), on the western side of the trench.[citation needed]
The Pacific plate is subducted beneath the Mariana plate, creating the Mariana trench, and (further on) the arc of the Mariana Islands, as water trapped in the plate is released and explodes upward to form island volcanoes and earthquakes.
The Mariana Trench is part of theIzu–Bonin–Marianasubduction system that forms theboundary between twotectonic plates. In this system, the western edge of one plate, thePacific plate, issubducted (i.e., thrust) beneath the smallerMariana plate that lies to the west. Crustal material at the western edge of the Pacific plate is some of the oldestoceanic crust on Earth (up to 170 million years old), and is, therefore, cooler and denser; hence its great height difference relative to the higher-riding (and younger) Mariana plate. The deepest area at the plate boundary is the Mariana Trench proper.[citation needed]
The trench was firstsounded during theChallenger expedition in 1875 using a weighted rope, which recorded a depth of 4,475fathoms (8,184 metres; 26,850 feet).[11][12] In 1877, a map was published calledTiefenkarte des Grossen Ozeans ("Depth map of the Great Ocean") by Petermann, which showed aChallenger Tief ("Challenger deep") at the location of that sounding. In 1899,USS Nero, a convertedcollier, recorded a depth of 5,269 fathoms (9,636 metres; 31,614 feet).[13]
In 1951, under Chief ScientistThomas Gaskell,Challenger II surveyed the trench usingecho sounding, a much more precise and vastly easier way to measure depth than the sounding equipment and drag lines used in the original expedition. During this survey, the deepest part of the trench was recorded when theChallenger II measured a depth of 5,960 fathoms (10,900 metres; 35,760 feet) at11°19′N142°15′E / 11.317°N 142.250°E /11.317; 142.250,[14] known as the Challenger Deep.[15]
In 1957, theSoviet vesselVityaz reported a depth of 11,034 m (36,201 ft; 6,033 fathoms) at a location dubbed theMariana Hollow.[16][better source needed]
In 1984, the Japanese survey vesselTakuyō (拓洋) collected data from the Mariana Trench using a narrow, multi-beam echo sounder; it reported a maximum depth of 10,924 metres (35,840 ft), also reported as 10,920 ± 10 m (35,827 ± 33 ft; 5,971.1 ± 5.5 fathoms).[17] Remotely Operated VehicleKAIKO reached the deepest area of the Mariana Trench and made the deepest diving record of 10,911 m (35,797 ft; 5,966 fathoms) on 24 March 1995.[18]
During surveys carried out between 1997 and 2001, a spot was found along the Mariana Trench that had a depth similar to the Challenger Deep, possibly even deeper. It was discovered while scientists from theHawaii Institute of Geophysics and Planetology were completing a survey aroundGuam; they used a sonar mapping system towed behind the research ship to conduct the survey. This new spot was named theHMRG (Hawaii Mapping Research Group) Deep, after the group of scientists who discovered it.[19]
On 1 June 2009, mapping aboard theRV Kilo Moana (mothership of the Nereus vehicle), indicated a spot with a depth of 10,971 m (35,994 ft; 5,999 fathoms). The sonar mapping of the Challenger Deep was possible by its Simrad EM120 sonar multibeam bathymetry system for deep water. The sonar system uses phase and amplitude bottom detection, with an accuracy of better than 0.2% of water depth across the entire swath (implying that the depth figure is accurate to ± 22 metres (72 ft; 12 fathoms)).[20][21]
In 2011, it was announced at theAmerican Geophysical Union Fall Meeting that a US Navy hydrographic ship equipped with amultibeam echosounder conducted a survey which mapped the entire trench to 100 m (330 ft; 55 fathoms) resolution.[2] The mapping revealed the existence of four rocky outcrops thought to be formerseamounts.[22]
As of 2022, 22 crewed descents and seven uncrewed descents have been achieved. The first was the crewed descent by Swiss-designed, Italian-built,United States Navy-ownedbathyscapheTrieste, which reached the bottom at 1:06 pm on 23 January 1960, withDon Walsh andJacques Piccard on board.[15][25] Iron shot was used forballast, with gasoline for buoyancy.[15] The onboard systems indicated a depth of 37,800 feet (11,521 m; 6,300 fathoms),[26] but this was later revised to 35,814 feet (10,916 m; 5,969 fathoms).[27] The depth was estimated from a conversion ofpressure measured and calculations based on thewater density from sea surface to seabed.[25]
This was followed by the uncrewedROVsKaikō in 1996 andNereus in 2009. The first three expeditions directly measured very similar depths of 10,902 to 10,916 m (35,768 to 35,814 ft; 5,961 to 5,969 fathoms).[28][29] The fourth was made by Canadian film directorJames Cameron on 26 March 2012. He reached the bottom of the Mariana Trench in the submersible vesselDeepsea Challenger, diving to a depth of 10,908 m (35,787 ft; 5,965 fathoms).[30][31][32]
In July 2015, members of the National Oceanic and Atmospheric Administration, Oregon State University, and the Coast Guard submerged ahydrophone into the deepest part of the Mariana Trench, the Challenger Deep, never having previously deployed one past a mile. The titanium-shelled hydrophone was designed to withstand the immense pressure 7 miles (37,000 ft; 6,200 fathoms; 11,000 m) under.[33] Although researchers were unable to retrieve the hydrophone until November, the data capacity was full within the first 23 days. After months of analyzing the sounds, the experts were surprised to pick up natural sounds likeearthquakes,typhoons,baleen whales, and machine-made sounds such as boats.[34]
Victor Vescovo achieved a new record descent to 10,928 m (35,853 ft; 5,976 fathoms) on 28 April 2019 using the DSVLimiting Factor, a Triton 36000/2 model manufactured by Florida-basedTriton Submarines. He dived four times between 28 April and 5 May 2019, becoming the first person to dive into Challenger Deep more than once. It was then reported on 13 May.[35][36][37]
On 8 May 2020, a joint project between the Russian shipbuilders, scientific teams of theRussian Academy of Sciences with the support of theRussian Foundation for Advanced Research Projects and thePacific Fleet submerged theautonomous underwater vehicleVityaz-D to the bottom of the Mariana Trench at a depth of 10,028 m (32,900 ft; 5,483 fathoms).Vityaz-D is the first underwater vehicle to operate autonomously at the extreme depths of the Mariana Trench. The duration of the mission, excluding diving and surfacing, was more than 3 hours.[38][39]
On 10 November 2020, the Chinese submersibleFendouzhe reached the bottom of the Mariana Trench at a depth of 10,909 m (35,791 ft; 5,965 fathoms).[40][41]
Life
The expedition conducted in 1960 claimed to have observed, with great surprise because of the high pressure, large creatures living at the bottom, such as aflatfish about 30 cm (12 in) long,[26] and shrimp.[42] According to Piccard, "The bottom appeared light and clear, a waste of firmdiatomaceous ooze".[26] Many marine biologists are now skeptical of the supposed sighting of the flatfish, and it is suggested that the creature may instead have been asea cucumber.[43][44] During the second expedition, the uncrewed vehicleKaikō collected mud samples from theseabed.[45] Tiny organisms were found to be living in those samples.[citation needed]
In July 2011, a research expedition deployed untethered landers, called drop cams, equipped with digital video cameras and lights to explore this deep-sea region. Among many other living organisms, some gigantic single-celled foraminiferans with a size of more than 10 cm (4 in), belonging to the class ofmonothalamea, were observed.[46] Monothalamea are noteworthy for their size, their extreme abundance on the seafloor, and their role as hosts for a variety of organisms.[citation needed]
In December 2014, a new species ofsnailfish was discovered at a depth of 8,145 m (26,722 ft; 4,454 fathoms), breaking the previous record for the deepest living fish seen on video.[47]
During the 2014 expedition, several new species were filmed, including hugeamphipods known as supergiants.Deep-sea gigantism is the process where species grow larger than their shallow-water relatives.[47]
In May 2017, an unidentified type of snailfish was filmed at a depth of 8,178 metres (26,800 ft).[48]
Pollution
In 2016, a research expedition looked at the chemical makeup of crustacean scavengers collected from the range of 7,841–10,250 m (25,725–33,629 ft; 4,288–5,605 fathoms) within the trench. Within these organisms, the researchers found extremely elevated concentrations ofPCBs, a chemical toxin banned in the 1970s for its environmental harm, concentrated at all depths within the sediment of the trench.[49] Further research has found that amphipods also ingestmicroplastics, with 100% of amphipods having at least one piece of synthetic material in their stomachs.[50][51]
In 2019, Victor Vescovo reported finding a plastic bag and candy wrappers at the bottom of the trench.[52] That year,Scientific American also reported thatcarbon-14 from nuclear bomb testing has been found in the bodies of aquatic animals found in the trench.[53]
Possible nuclear waste disposal site
Like other oceanic trenches, the Mariana Trench has been proposed as a site fornuclear waste disposal[54][55] in the hope that tectonic platesubduction occurring at the site might eventually push the nuclear waste deep into theEarth's mantle, the second layer of the Earth. In 1979 Japan planned to dump low-level nuclear wastes near Maug, in the Northern Marianas.[56] However, ocean dumping of nuclear waste is prohibited by international law.[54][55][57] Furthermore, plate subduction zones are associated with very largemegathrust earthquakes, the effects of which are unpredictable for the safety of long-term disposal of nuclear wastes within thehadopelagicecosystem.[55]
Mariana Trench Marine National Monument, United States national monument at the trench. This National Monument protects 246,610 square kilometres (95,216 mi2) of submerged lands and waters of the Mariana Archipelago. It includes some of the Mariana Trench, but not the deepest part, theChallenger Deep, which lies just outside the monument area.
^Mariana Trench is 10,994 m (36,070 ft; 6.831 mi) deep,[2] while Mount Everest is 8,848 m (29,029 ft; 5.498 mi) tall.[3] The difference is 2,146 m (7,041 ft; 1.333 mi), or at least no less than 2,104 m (6,903 ft; 1.307 mi), accounting for the combined 42 m (138 ft; 0.026 mi) uncertainty in the measurements.
^Glud, Ronnie; Wenzhöfer, Frank; Middleboe, Mathias; Oguri, Kazumasa; Turnewitsch, Robert; Canfield, Donald E.; Kitazato, Hiroshi (17 March 2013). "High rates of microbial carbon turnover in sediments in the deepest oceanic trench on Earth".Nature Geoscience.6 (4):284–288.Bibcode:2013NatGe...6..284G.doi:10.1038/ngeo1773.
^Cheng, Xiang; Liu, Liang (10 November 2020).""奋斗者"号载人潜水器突破万米海深 潜入全球最深海域" [The "Striver" manned submersible breaks through 10,000 meters and dives into the world's deepest waters].China Central Television. Retrieved11 November 2020.
^Jamieson, Alan J.; Malkocs, Tamas; Piertney, Stuart B.; Fujii, Toyonobu; Zhang, Zulin (13 February 2017). "Bioaccumulation of persistent organic pollutants in the deepest ocean fauna".Nature Ecology & Evolution.1 (3): 51.doi:10.1038/s41559-016-0051.hdl:2164/9142.ISSN2397-334X.PMID28812719.S2CID9192602.
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