Cayman Trough

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Coordinates: 18°30′N83°0′W / 18.500°N 83.000°W / 18.500; -83.000

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False-color image of the Cayman Trough, created from digital databases of seafloor and land elevations. Cayman Trough.jpg
False-color image of the Cayman Trough, created from digital databases of seafloor and land elevations.
Mid-Cayman spreading centre as part of the trough, on the western edge of the Gonave Microplate. Gonave microplate.png
Mid-Cayman spreading centre as part of the trough, on the western edge of the Gonâve Microplate.

The Cayman Trough (also known as the Cayman Trench, Bartlett Deep and Bartlett Trough) is a complex transform fault zone pull-apart basin which contains a small spreading ridge, the Mid-Cayman Rise, on the floor of the western Caribbean Sea between Jamaica and the Cayman Islands. [1] It is the deepest point in the Caribbean Sea and forms part of the tectonic boundary between the North American Plate and the Caribbean Plate. It extends from the Windward Passage, going south of the Sierra Maestra of Cuba toward Guatemala. The transform continues onshore as the Motagua Fault, which cuts across Guatemala and extends offshore under the Pacific Ocean, where it intersects the Middle America Trench subduction zone.

Transform fault A plate boundary where the motion is predominantly horizontal

A transform fault or transform boundary is a plate boundary where the motion is predominantly horizontal. It ends abruptly and is connected to another transform, a spreading ridge, or a subduction zone.

In geology, a basin is a region where subsidence generates accommodation space for the deposition of sediments. A pull-apart basin is a structural basin where two overlapping faults or a fault bend creates an area of crustal extension undergoing tension, which causes the basin to sink down. Frequently, the basins are rhombic or sigmoidal in shape. Dimensionally, basins are limited to the distance between the faults and the length of overlap. Pull-apart basins are also referred to as overlapping-tension-zones (OTZ).

Divergent boundary Linear feature that exists between two tectonic plates that are moving away from each other

In plate tectonics, a divergent boundary or divergent plate boundary is a linear feature that exists between two tectonic plates that are moving away from each other. Divergent boundaries within continents initially produce rifts which eventually become rift valleys. Most active divergent plate boundaries occur between oceanic plates and exist as mid-oceanic ridges. Divergent boundaries also form volcanic islands which occur when the plates move apart to produce gaps which molten lava rises to fill.

The relatively narrow trough trends east-northeast to west-southwest and has a maximum depth of 7,686 metres (25,217 ft). Within the trough is a slowly spreading north-south ridge which may be the result of an offset or gap of approximately 420 kilometres (260 mi) along the main fault trace. The Cayman spreading ridge shows a long-term opening rate of 11–12 mm/yr. [2] The eastern section of the trough has been named the Gonâve Microplate. The Gonâve plate extends from the spreading ridge east to the island of Hispaniola. It is bounded on the north by the Oriente and Septentrional fault zones. On the south the Gonâve is bounded by the Walton fault zone, the Jamaica restraining bend and the Enriquillo-Plantain Garden fault zone. The two bounding strike slip fault zones are left lateral. The motion relative to the North American Plate is 11 mm/yr to the east and the motion relative to the Caribbean Plate is 8 mm/yr. [2] The western section of the trough is bounded to its south by the Swan Islands Transform Fault. [3]

Mid-ocean ridge An underwater mountain system formed by plate tectonic spreading

A mid-ocean ridge (MOR) is an underwater mountain system formed by plate tectonics. It consists of various mountains linked in chains, typically having a valley known as a rift running along its spine. This type of oceanic mountain ridge is characteristic of what is known as an 'oceanic spreading center', which is responsible for seafloor spreading. The production of new seafloor results from mantle upwelling in response to plate spreading; this isentropic upwelling solid mantle material eventually exceeds the solidus and melts. The buoyant melt rises as magma at a linear weakness in the oceanic crust, and emerges as lava, creating new crust upon cooling. A mid-ocean ridge demarcates the boundary between two tectonic plates, and consequently is termed a divergent plate boundary.

Gonâve Microplate Part of the boundary between the North American Plate and the Caribbean Plate

The Gonâve Microplate forms part of the boundary between the North American Plate and the Caribbean Plate. It is bounded to the west by the Cayman spreading center, to the north by the Septentrional-Oriente fault zone and to the south by the Walton fault zone and the Enriquillo-Plantain Garden fault zone. The existence of this microplate was first proposed in 1991. This has been confirmed by GPS measurements, which show that the overall displacement between the two main plates is split almost equally between the transform fault zones that bound the Gonâve microplate. The microplate is expected to eventually become accreted to the North American Plate.

Hispaniola island in the Caribbean

Hispaniola is an island in the Caribbean island group known as the Greater Antilles. It is the second largest island in the Caribbean after Cuba, and the most populous island in the Caribbean; it is also the eleventh most populous island in the world.

During the Eocene the trough was the site of a subduction zone which formed the volcanic arc of the Cayman Ridge and the Sierra Maestra volcanic terrain of Cuba to the north, as the northeastward-moving Caribbean Plate was subducted beneath the southwest-moving North American Plate, or as some researchers contend, beneath a plate fragment dubbed the East Cuban Microplate. [4]

The Eocene Epoch, lasting from 56 to 33.9 million years ago, is a major division of the geologic timescale and the second epoch of the Paleogene Period in the Cenozoic Era. The Eocene spans the time from the end of the Paleocene Epoch to the beginning of the Oligocene Epoch. The start of the Eocene is marked by a brief period in which the concentration of the carbon isotope 13C in the atmosphere was exceptionally low in comparison with the more common isotope 12C. The end is set at a major extinction event called the Grande Coupure or the Eocene–Oligocene extinction event, which may be related to the impact of one or more large bolides in Siberia and in what is now Chesapeake Bay. As with other geologic periods, the strata that define the start and end of the epoch are well identified, though their exact dates are slightly uncertain.

Volcanic arc A chain of volcanoes formed above a subducting plate

A volcanic arc is a chain of volcanoes formed above a subducting plate, positioned in an arc shape as seen from above. Offshore volcanoes form islands, resulting in a volcanic island arc. Generally, volcanic arcs result from the subduction of an oceanic tectonic plate under another tectonic plate, and often parallel an oceanic trench. The oceanic plate is saturated with water, and volatiles such as water drastically lower the melting point of the mantle. As the oceanic plate is subducted, it is subjected to greater and greater pressures with increasing depth. This pressure squeezes water out of the plate and introduces it to the mantle. Here the mantle melts and forms magma at depth under the overriding plate. The magma ascends to form an arc of volcanoes parallel to the subduction zone.

The Cayman Ridge is a submarine mountain range on the northern margin of the Cayman Trough in the Caribbean Sea. It extends from the Sierra Maestra in the east to the Misteriosa Bank in the west, a distance of about 1,500 km (930 mi). The Cayman Ridge also includes the Cayman Islands.

In 2010 a UK team from the National Oceanography Centre in Southampton (NOCS), equipped with an autonomously controlled robot submarine, began mapping the full extent of the trench and discovered black smokers on the ocean floor at a depth of 5 km (3.1 mi), the deepest yet found. [5] [6] [7] In January 2012, the researchers announced that water exits the vents at a temperature possibly exceeding 450 °C (842 °F), making them among the hottest known undersea vents. They also announced the discovery of new species, including an eyeless shrimp with a light-sensing organ on its back. [8]

The National Oceanography Centre (NOC) is a marine science research and technology institution based on two sites in Southampton and Liverpool, United Kingdom. It is the UK’s largest institution for integrated sea level science, coastal and deep ocean research and technology development.

Southampton City and unitary authority area in England

Southampton is the largest city in the ceremonial county of Hampshire, England. It is 70 miles (110 km) south-west of London and 15 miles (24 km) west north-west of Portsmouth. Southampton is a major port and the closest city to the New Forest. It lies at the northernmost point of Southampton Water at the confluence of the Rivers Test and Itchen, with the River Hamble joining to the south of the urban area. The city, which is a unitary authority, has an estimated population of 253,651. The city's name is sometimes abbreviated in writing to "So'ton" or "Soton", and a resident of Southampton is called a Sotonian.

Shrimp Decapod crustaceans

The term shrimp is used to refer to some decapod crustaceans, although the exact animals covered can vary. Used broadly, shrimp may cover any of the groups with elongated bodies and a primarily swimming mode of locomotion – most commonly Caridea and Dendrobranchiata. In some fields, however, the term is used more narrowly and may be restricted to Caridea, to smaller species of either group or to only the marine species. Under the broader definition, shrimp may be synonymous with prawn, covering stalk-eyed swimming crustaceans with long narrow muscular tails (abdomens), long whiskers (antennae), and slender legs. Any small crustacean which resembles a shrimp tends to be called one. They swim forward by paddling with swimmerets on the underside of their abdomens, although their escape response is typically repeated flicks with the tail driving them backwards very quickly. Crabs and lobsters have strong walking legs, whereas shrimp have thin, fragile legs which they use primarily for perching.

See also

Related Research Articles

Geography of the Cayman Islands

The Cayman Islands are a British dependency and island country. It is a three-island archipelago in the Caribbean Sea, consisting of Grand Cayman, Cayman Brac, and Little Cayman. Georgetown, the capital of the Cayman Islands is 438 km (272 mi) south of Havana, Cuba, and 504 km (313 mi) northwest of Kingston, Jamaica, northeast of Costa Rica, north of Panama and are between Cuba and Central America. Georgetown’s geographic coordinates are 19.300° north, 81.383° west.

North American Plate Large tectonic plate including most of North America, Greenland and a bit of Siberia

The North American Plate is a tectonic plate covering most of North America, Greenland, Cuba, the Bahamas, extreme northeastern Asia, and parts of Iceland and the Azores. It extends eastward to the Mid-Atlantic Ridge and westward to the Chersky Range in eastern Siberia. The plate includes both continental and oceanic crust. The interior of the main continental landmass includes an extensive granitic core called a craton. Along most of the edges of this craton are fragments of crustal material called terranes, accreted to the craton by tectonic actions over a long span of time. It is thought that much of North America west of the Rocky Mountains is composed of such terranes.

Cocos Plate A young oceanic tectonic plate beneath the Pacific Ocean off the west coast of Central America

The Cocos Plate is a young oceanic tectonic plate beneath the Pacific Ocean off the west coast of Central America, named for Cocos Island, which rides upon it. The Cocos Plate was created approximately 23 million years ago when the Farallon Plate broke into two pieces, which also created the Nazca Plate. The Cocos Plate also broke into two pieces, creating the small Rivera Plate. The Cocos Plate is bounded by several different plates. To the northeast it is bounded by the North American Plate and the Caribbean Plate. To the west it is bounded by the Pacific Plate and to the south by the Nazca Plate.

Puerto Rico Trench An oceanic trench on a transform boundary between the Caribbean and North American Plates

The Puerto Rico Trench is located on the boundary between the Caribbean Sea and the Atlantic Ocean. The oceanic trench is associated with a complex transition between the Lesser Antilles subduction zone to the south and the major transform fault zone or plate boundary, which extends west between Cuba and Hispaniola through the Cayman Trough to the coast of Central America. The trench is 800 kilometres (497 mi) long and has a maximum depth of 8,376 metres (27,480 ft) or 5.20 miles in the Brownson Deep, which is the deepest point in the Atlantic Ocean and the deepest point not in the Pacific Ocean. On December 19, 2018, its deepest point was identified by the DSSV Pressure Drop using a state-of-the-art Kongsberg EM124 multibeam sonar and then directly visited and its depth verified by the manned submersible DSV Limiting Factor.

Scotia Plate Minor oceanic tectonic plate between the South American and Antarctic Plates

The Scotia Plate is a tectonic plate on the edge of the South Atlantic and Southern Ocean. Thought to have formed during the early Eocene with the opening of the Drake Passage that separates South America from Antarctica, it is a minor plate whose movement is largely controlled by the two major plates that surround it: the South American plate and Antarctic plate.

Caribbean Plate A mostly oceanic tectonic plate including part of Central America and the Caribbean Sea

The Caribbean Plate is a mostly oceanic tectonic plate underlying Central America and the Caribbean Sea off the north coast of South America.

The Tonga Plate is a small southwest Pacific tectonic plate or microplate. It is centered at approximately 19° S. latitude and 173° E. longitude. The plate is an elongated plate oriented NNE - SSW and is a northward continuation of the Kermadec linear zone north of New Zealand. The plate is bounded on the east and north by the Pacific Plate, on the northwest by the Niuafo’ou Microplate, on the west and south by the Indo-Australian Plate. The Tonga plate is subducting the Pacific plate along the Tonga Trench. This subduction turns into a transform fault boundary north of Tonga. An active rift or spreading center separates the Tonga from the Australian plate and the Niuafo’ou microplate to the west. The Tonga plate is seismically very active and is rotating clockwise.

Geology of Puerto Rico

Puerto Rico is composed of Jurassic to Eocene volcanic and plutonic rocks, which are overlain by younger Oligocene to recent carbonates and other sedimentary rocks. Most of the caverns and karst topography on the island occurs in the northern Oligocene to recent carbonates. The oldest rocks are approximately 190 million years old (Jurassic) and are located at Sierra Bermeja in the southwest part of the island. These rocks may represent part of the oceanic crust and are believed to come from the Pacific Ocean realm.

Easter Plate is located to the west of Easter Island off the west coast of South America in the middle of the Pacific Ocean, bordering the Nazca plate to the east and the Pacific plate to the west. It was discovered from looking at earthquake distributions that were offset from the previously perceived Nazca-Pacific Divergent boundary. This young plate is 5.25 million years old and is considered a microplate because it is small with an area of approximately 160,000 km2. Seafloor spreading along the Easter microplate's borders have some of the highest global rates, ranging from 50 to 140 mm/yr.

South American–Antarctic Ridge Mid-ocean ridge in the South Atlantic between the South American Plate and the Antarctic Plate

The South American–Antarctic Ridge is the tectonic spreading center between the South American Plate and the Antarctic Plate. It runs along the sea-floor from the Bouvet Triple Junction in the South Atlantic Ocean south-westward to a major transform fault boundary east of the South Sandwich Islands. Near the Bouvet Triple Junction the spreading half rate is 9 mm/a (0.35 in/year), which is slow, and the SAAR has the rough topography characteristic of slow-spreading ridges.

Kermadec-Tonga subduction zone A convergent plate boundary that stretches from the North Island of New Zealand northward

The Kermadec-Tonga subduction zone is a convergent plate boundary that stretches from the North Island of New Zealand northward. The formation of the Kermadec and Tonga Plates started about 4–5 million years ago. Today, the eastern boundary of the Tonga Plate is one of the fastest subduction zones, with a rate up to 24 cm/yr. The trench formed between the Kermadec-Tonga and Pacific Plates is also home to the second deepest trench in the world, at about 10,800 m, as well as the longest chain of submerged volcanoes.

Juan Fernández Plate Very small tectonic plate in the southern Pacific Ocean

The Juan Fernandez Plate is a microplate in the Pacific Ocean. With a surface area of approximately 105 km2, the microplate is located between 32° and 35°S and 109° and 112°W. The plate is located at a triple junction between the Pacific Plate, Antarctic Plate, and Nazca Plate. Approximately 2000 km to the west of South America, it is, on average, 3000 meters deep with its shallowest point coming to approximately 1600 meters, and its deepest point reaching 4400 meters.

Mariana Plate A small tectonic plate west of the Mariana Trench

The Mariana Plate is a micro tectonic plate located west of the Mariana Trench which forms the basement of the Mariana Islands which form part of the Izu-Bonin-Mariana Arc. It is separated from the Philippine Sea Plate to the west by a divergent boundary with numerous transform fault offsets. The boundary between the Mariana and the Pacific Plate to the east is a subduction zone with the Pacific Plate subducting beneath the Mariana. This eastern subduction is divided into the Mariana Trench, which forms the southeastern boundary, and the Izu-Ogasawara Trench the northeastern boundary. The subduction plate motion is responsible for the shape of the Mariana plate and back arc.

Septentrional-Oriente fault zone

The Septentrional-Orient fault zone (SOFZ) is a system of coaxial left lateral-moving strike slip faults that runs along the northern side of the island of Hispaniola where Haiti and the Dominican Republic are located and continues along the south of Cuba along the northern margin of the Cayman Trough. The SOFZ shares approximately half of the relative motion between the North American and Caribbean tectonic plates with the Enriquillo-Plantain Garden fault zone and Walton fault zone which run along the southern side of Hispaniola and aong the southern margin of the Cayman Trough. Both fault zones terminate at the Mid-Cayman Rise to the west. Some researchers believe that the Enriquillo-Plantain Garden fault zone and the SOFZ bound a microplate, dubbed the Gonâve Microplate, a 190,000 km2 (73,000 sq mi) area of the northern Caribbean Plate that is in the process of shearing off the Caribbean Plate and accreting to the North America Plate.

The Geology of Jamaica is formed of rocks of Cretaceous to Neogene age. The basement consists of Cretaceous island arc and back-arc basin sequences that formed above a subduction zone. The cover is of mainly Eocene to Miocene shallow water limestones, that have been uplifted due to the presence of a restraining bend along the major strike-slip faults that bound the southern edge of the Gonâve Microplate to the north of the island.

Geology of the Pacific Ocean

The Pacific Ocean evolved in the Mesozoic from the Panthalassic Ocean, which had formed when Rodinia rifted apart around 750 Ma. The first ocean floor which is part of the current Pacific Plate began 160 Ma to the west of the central Pacific and subsequently developed into the largest oceanic plate on Earth.

Walton fault zone

The Walton fault zone is a major left lateral (sinistral) strike-slip fault, forming part of the southern boundary to the Cayman Trough. It extends from the Mid-Cayman Rise spreading center in the west to Jamaica in the east. It has a total length of about 360 km and is formed of several sub-parallel strands. Together with the Enriquillo-Plantain Garden fault zone it forms the southern boundary of the Gonâve Microplate. It is associated with only moderate earthquakes with magnitudes of less than 6.

Mid-Cayman Rise

The Mid-Cayman Rise or Mid-Cayman Spreading Center is a relatively short divergent plate boundary in the middle of the Cayman Trough. It forms part of a dominantly transform boundary that is part of the southern margin to the North American Plate. It developed during the Eocene when the northern part of the Caribbean Plate collided with the Bahamas Platform, forcing the southern boundary to propagate southwards. This boundary initially formed as two strike-slip faults with a large left-stepping offset between them, generating a pull-apart basin. Continuing movement on the boundary and extension within the pull-apart led to the formation of an area of oceanic crust containing a north-south trending spreading center that remains active to the present day. It is an ultra-slow spreading center with an opening rate of 15–17 mm per year.

References

  1. Einsele, Gerhard (2000). Sedimentary Basins: Evolution, Facies, and Sediment Budget (2nd ed.). Springer. p. 630. ISBN   978-3-540-66193-1.
  2. 1 2 DeMets, C.; Wiggins-Grandison, M. (2007). "Deformation of Jamaica and motion of the Gonâve microplate from GPS and seismic data". Geophys. J. Int. 168 (1): 375–6. Bibcode:2007GeoJI.168..362D. doi:10.1111/j.1365-246x.2006.03236.x.
  3. Rosencrantz M.; Mann P. (1991). "SeaMARC II mapping of transform faults in the Cayman Trough, Caribbean Sea". Geology. 19 (7): 690–691. Bibcode:1991Geo....19..690R. doi:10.1130/0091-7613(1991)019<0690:SIMOTF>2.3.CO;2.
  4. Sigurdsson, H, S. Kelley, R.M. Leckie, S. Carey, T. Bralower, and J. King (2000). "Chapter 20: History of circum-Caribbean explosive volcanism: 40Ar/39Ar dating of tephra layers". In Leckie, R.M., Sigurdsson, H., Acton, G.D., and Draper, G. Sci. Results. Proc. ODP. 165. College Station, Texas: Ocean Drilling Program. doi:10.2973/odp.proc.sr.165.2000. ISSN   1096-7451.CS1 maint: Uses authors parameter (link) CS1 maint: Uses editors parameter (link)
  5. Carpenter, Jennifer (August 9, 2008). "Sub to make deep Caribbean dive". BBC Science News. Retrieved August 9, 2008.
  6. "World's deepest undersea vents discovered". LiveScience.com. April 11, 2010. Retrieved April 12, 2010.
  7. "Latest news". RRS James Cook Voyage 44. Retrieved January 14, 2012.
  8. McGrath, Matt (January 12, 2012). "Cayman vents are world's hottest". BBC News. Retrieved January 14, 2012.

Further reading

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