Mariana Plate

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.[2]

Mariana Plate
The Mariana Plate
TypeMinor
Approximate area360,000 km2[1]
Movement1north-west
Speed139-51mm/year
FeaturesMariana Islands, Mariana Trench
1Relative to the African Plate
Cross section of mariana trench
Cross section across the Mariana Plate

Geological History

Subduction at the Mariana plate has been going on for over 50 million years.[3] Some theories of the origin of this microplate is that when the Pacific plate began to subduct beneath the Philippine plate the volcanism and spreading ridge started to make an arc. This geological activity caused the section of the Philippine plate to break off and become the Mariana microplate. The Mariana Islands consist of volcanoes that are active and dormant[4] and are made up of volcanic and sedimentary rocks from the Pleistocene.[5]

Defining Features

As the Pacific Plate subducts beneath the Mariana Plate, it creates a trench. This is the Mariana Trench, and it is the deepest trench in the world. Another result from this subduction are the Mariana Islands. These are formed from dehydration of the subducting, old oceanic crust creates melt, and the melt rises to the surface through a volcano. This volcanism has been occurring for almost 50 million years.[3] The rock type in the area is volcaniclastic sediments on top of igneous rocks. The source of these rocks are from crustal spreading.[6]

Just off the eastern coast of Mariana there are big seamounts made of serpentinized periodite.[7] They are formed from mud volcanism. The composition for the seamounts differ in the Izu-Ogasawara Trench and Mariana systems which indicates regional changes in geology.[3]

Tectonic Behavior

Eastern Convergent Boundary

Mariana Features
Mariana Plate Boundary. 1 is West Mariana Ridge, 2 is Mariana Trough, 3 is Mariana Arc, 4 is Mariana Fore-Arc, 5 is Mariana Trench

The tectonic plate is approximately 100 km thick and converging to the east at a rate of 50–80 mm/yr with the Pacific Plate subducting at 60–100 mm/yr [8] This eastern subduction is divided into the Mariana Trench, which forms the southeastern boundary, and the Izu-Ogasawara Trench the northeastern boundary. The Izu-Ogasawara Trench and Mariana subduction zones are traveling at different rates.[9] While the northern section of the Izu-Ogasawara Trench plate is subducting at 44 mm/yr, the southern section subducts at 14 mm/yr. The subducting Pacific Plate dips at about 10 degrees and directed 83 degrees west of north.[4] The northern subduction zone is expanding by rifting while the southern contains a strike slip fault.[7] Seismologists have been studying how the subducting slabs underneath the Mariana island arc are entering the lower mantle and being redirected horizontally, deflecting off the upper to lower mantle transition zone.[10][6]

Western Divergent Boundary

The Mariana Plate is also separating at a rate of 30 mm/yr from the Philippine Plate to the west. The Mariana Trough is located on the western side of the island arc along with the back arc basin. Around 3 Ma the basin began spreading at 4.7 cm/yr.[6] Due to the back arc spreading in the Marian Trough the islands are moving east while the Philippine Sea plate is staying almost stationary.[4]

Future of Plate

Since there is volcanism happening on the Mariana back arc ridge and basin, this system could continue to grow but combining the rate of separation from the Philippine plate along with the subduction destroying the Mariana plate it is possible this microplate could eventually dissipate. The rate of subduction is greater than the rate of uplift.[11] The collision of aseismic ridges and the axis of the trench explain how the plate curvature is evolving.[5]

See also

References

  1. ^ Alden, Andrew (28 February 2017). "Here Are the Sizes of Tectonic or Lithospheric Plates". ThoughtCo.com. Retrieved 9 July 2017.
  2. ^ "An updated digital model of plate boundaries: PB2002". peterbird.name. Retrieved 2018-06-02.
  3. ^ a b c Administration, US Department of Commerce, National Oceanic and Atmospheric. "Okeanos Explorer | Expeditions | NOAA Ship Okeanos Explorer: 2016 Deepwater Exploration of the Marianas: Background: The Geology of the Mariana Convergent Plate Region". oceanexplorer.noaa.gov. Retrieved 2018-05-30.
  4. ^ a b c Kato, Teruyuki; Beavan, John; Matsushima, Takeshi; Kotake, Yoshiko; Camacho, Juan T.; Nakao, Shigeru (2003). "Geodetic evidence of back-arc spreading in the Mariana Trough". Geophysical Research Letters. 30 (12). doi:10.1029/2002gl016757. ISSN 0094-8276.
  5. ^ a b "Marianas Plate". Tectonics of Asia. Retrieved 2018-05-30.
  6. ^ a b c "Marianas Plate". Tectonics of Asia. Retrieved 2018-06-01.
  7. ^ a b "1. Leg 195 Synthesis: Site 1200—Serpentinite Seamounts of the Izu-Bonin/Mariana Convergent Plate Margin (ODP Leg 125 and 195 Drilling Results)1". www-odp.tamu.edu. Retrieved 2018-05-30.
  8. ^ Gvirtzman, Zohar (2004). "Bathymetry of Mariana trench-arc system and formation of the Challenger Deep as a consequence of weak plate coupling" (PDF). Geological Survey of Israel, Jerusalem, Israel. 23.
  9. ^ Administration, US Department of Commerce, National Oceanic and Atmospheric. "Okeanos Explorer | Expeditions | NOAA Ship Okeanos Explorer: 2016 Deepwater Exploration of the Marianas: Background: The Geology of the Mariana Convergent Plate Region". oceanexplorer.noaa.gov. Retrieved 2018-06-02.
  10. ^ Van Der Hilst, Rob; Seno, Tetsuzo (1993-12-01). "Effects of relative plate motion on the deep structure and penetration depth of slabs below the Izu-Bonin and Mariana island arcs". Earth and Planetary Science Letters. 120 (3–4): 395–407. doi:10.1016/0012-821X(93)90253-6. ISSN 0012-821X.
  11. ^ Fryer, P.; Wheat, C. G.; Mottl, M. J. (1999). "Mariana blueschist mud volcanism: Implications for conditions within the subduction zone". Geology. 27 (2): 103. doi:10.1130/0091-7613(1999)027<0103:MBMVIF>2.3.CO;2. ISSN 0091-7613.
Convergent boundary

A convergent boundary is an area on Earth where two or more lithospheric plates collide. One plate eventually slides beneath the other causing a process known as subduction. The subduction zone can be defined by a plane where many earthquakes occur, called the Benioff Zone. These collisions happen on scales of millions to tens of millions of years and can lead to volcanism, earthquakes, orogenesis, destruction of lithosphere, and deformation. Convergent boundaries occur between oceanic-oceanic lithosphere, oceanic-continental lithosphere, and continental-continental lithosphere. The geologic features related to convergent boundaries vary depending on crust types.

Plate tectonics is driven by convection cells in the mantle. Convection cells are the result of heat generated by radioactive decay of elements in the mantle escaping to the surface and the return of cool materials from the surface to the mantle. These convection cells bring hot mantle material to the surface along spreading centers creating new crust. As this new crust is pushed away from the spreading center by the formation of newer crust, it cools, thins, and becomes denser. Subduction initiates when this dense crust converges with the less dense crust. The force of gravity helps drive the subducting slab into the mantle. Evidence supports that the force of gravity will increase plate velocity. As the relatively cool subducting slab sinks deeper into the mantle, it is heated causing dehydration of hydrous minerals. This releases water into the hotter asthenosphere, which leads to partial melting of asthenosphere and volcanism. Both dehydration and partial melting occurs along the 1000 °C isotherm, generally at depths of 65 – 130 km.Some lithospheric plates consist of both continental and oceanic lithosphere. In some instances, initial convergence with another plate will destroy oceanic lithosphere, leading to convergence of two continental plates. Neither continental plate will subduct. It is likely that the plate may break along the boundary of continental and oceanic crust. Seismic tomography reveals pieces of lithosphere that have broken off during convergence.

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.The tectonic plates continue to move today. The slowest spreading ridge is the Gakkel Ridge on the Arctic Ocean floor, which spreads at less than 2.5 cm/year (1 in/year), while the fastest, the East Pacific Rise near Easter Island, has a spreading rate of over 15 cm/year (6 in/year).

Guam

Guam ( (listen); Chamorro: Guåhån [ˈɡʷɑhɑn]) is an unincorporated and organized territory of the United States in Micronesia in the western Pacific Ocean. It is the westernmost point and territory of the United States, along with the Northern Mariana Islands. The capital city of Guam is Hagåtña and the most populous city is Dededo. The inhabitants of Guam are called Guamanians, and they are American citizens by birth. The indigenous Guamanians are the Chamorros, who are related to other Austronesian natives of Eastern Indonesia, the Philippines, and Taiwan. Guam has been a member of the Pacific Community since 1983.

In 2016, 162,742 people resided on Guam. Guam has an area of 210 square miles (540 km2; 130,000 acres) and a population density of 775 per square mile (299/km2). In Oceania, it is the largest and southernmost of the Mariana Islands and the largest island in Micronesia. Among its municipalities, Mongmong-Toto-Maite has the highest population density at 3,691 per square mile (1,425/km2), whereas Inarajan and Umatac have the lowest density at 119 per square mile (46/km2). The highest point is Mount Lamlam at 1,332 feet (406 m) above sea level. Since the 1960s, the economy has been supported by two industries: tourism and the United States Armed Forces.The indigenous Chamorros settled the island approximately 4,000 years ago. Portuguese explorer Ferdinand Magellan, while in the service of Spain, was the first European to visit the island, on March 6, 1521. Guam was colonized by Spain in 1668 with settlers, including Diego Luis de San Vitores, a Catholic Jesuit missionary. Between the 16th century and the 18th century, Guam was an important stopover for the Spanish Manila Galleons. During the Spanish–American War, the United States captured Guam on June 21, 1898. Under the Treaty of Paris, Spain ceded Guam to the United States on December 10, 1898. Guam is among the 17 non-self-governing territories listed by the United Nations.Before World War II, there were five American jurisdictions in the Pacific Ocean: Guam and Wake Island in Micronesia, American Samoa and Hawaii in Polynesia, and the Philippines.

On December 7, 1941, hours after the attack on Pearl Harbor, Guam was captured by the Japanese, who occupied the island for two and a half years. During the occupation, Guamanians were subjected to beheadings, forced labor, rape, and torture. American forces recaptured the island on July 21, 1944; Liberation Day commemorates the victory.An unofficial but frequently used territorial motto is "Where America's Day Begins", which refers to the island's proximity to the International Date Line.

How the Earth Was Made

How the Earth Was Made is a documentary television series produced by Pioneer Productions for the History channel. It began as a two-hour special exploring the geological history of Earth, airing on December 16, 2007. Focusing on different geologic features of the Earth, the series premiered on February 10, 2009, and the 13-episode first season concluded on May 5, 2009. The second season premiered on November 24, 2009, and concluded on March 2, 2010.

Izu–Bonin–Mariana Arc

The Izu–Bonin–Mariana (IBM) arc system is a tectonic-plate convergent boundary. The IBM arc system extends over 2800 km south from Tokyo, Japan, to beyond Guam, and includes the Izu Islands, Bonin Islands, and Mariana Islands; much more of the IBM arc system is submerged below sealevel. The IBM arc system lies along the eastern margin of the Philippine Sea Plate in the Western Pacific Ocean. It is the site of the deepest gash in Earth's solid surface, the Challenger Deep in the Mariana Trench.

The IBM arc system formed as a result of subduction of the western Pacific plate. The IBM arc system now subducts mid-Jurassic to Early Cretaceous lithosphere, with younger lithosphere in the north and older lithosphere in the south, including the oldest (~170 million years old, or Ma) oceanic crust. Subduction rates vary from ~2 cm (1 inch) per year in the south to 6 cm (~2.5 inches) in the north.

The volcanic islands that comprise these island arcs are thought to have been formed from the release of volatiles (steam from trapped water, and other gases) being released from the subducted plate, as it reached sufficient depth for the temperature to cause release of these materials. The associated trenches are formed as the oldest (most western) part of the Pacific plate crust increases in density with age, and because of this process finally reaches its lowest point just as it subducts under the crust to the west of it.

The IBM arc system is an excellent example of an intra-oceanic convergent margin (IOCM). IOCMs are built on oceanic crust and contrast fundamentally with island arc built on continental crust, such as Japan or the Andes. Because IOCM crust is thinner, denser, and more refractory than that beneath Andean-type margins, study of IOCM melts and fluids allows more confident assessment of mantle-to-crust fluxes and processes than is possible for Andean-type convergent margins. Because IOCMs are far removed from continents they are not affected by the large volume of alluvial and glacial sediments. The consequent thin sedimentary cover makes it much easier to study arc infrastructure and determine the mass and composition of subducted sediments. Active hydrothermal systems found on the submarine parts of IOCMs give us a chance to study how many of earth's important ore deposits formed.

List of tectonic plates

This is a list of tectonic plates on the Earth's surface. Tectonic plates are pieces of Earth's crust and uppermost mantle, together referred to as the lithosphere. The plates are around 100 km (62 mi) thick and consist of two principal types of material: oceanic crust (also called sima from silicon and magnesium) and continental crust (sial from silicon and aluminium). The composition of the two types of crust differs markedly, with mafic basaltic rocks dominating oceanic crust, while continental crust consists principally of lower-density felsic granitic rocks.

Mariana Islands

The Mariana Islands (; also the Marianas) are a crescent-shaped archipelago comprising the summits of fifteen mostly dormant volcanic mountains in the western North Pacific Ocean, between the 12th and 21st parallels north and along the 145th meridian east. They lie south-southeast of Japan, west-southwest of Hawaii, north of New Guinea and east of the Philippines, demarcating the Philippine Sea's eastern limit. They are found in the northern part of the western Oceanic sub-region of Micronesia, and are politically divided into two jurisdictions of the United States: the Commonwealth of the Northern Mariana Islands and, at the southern end of the chain, the territory of Guam. The islands were named after the influential Spanish queen Mariana of Austria following their colonization in the 17th century.

Spanish navigators were the first Europeans to arrive in the early 16th century and eventually Spain annexed and colonized the archipelago with the capital in Guam. These were the first islands Magellan found after crossing the Pacific and the fruits found here helped the crew fight scurvy. The indigenous inhabitants are the Chamorro people. Archaeologists in 2013 reported findings which indicated that the people who first settled the Marianas arrived there after making what may have been at the time the longest uninterrupted ocean voyage in human history. They further reported findings which suggested that Tinian is likely to have been the first island in Oceania to have been settled by humans.

Mariana Trench

The Mariana Trench or Marianas Trench is located in the western Pacific Ocean about 200 kilometres (124 mi) east of the Mariana Islands; it is the deepest trench in the world. It is a crescent-shaped trough in the Earth's crust averaging about 2,550 km (1,580 mi) long and 69 km (43 mi) wide. The maximum known depth is 10,984 metres (36,037 ft) (± 25 metres [82 ft]) at the southern end of a small slot-shaped valley in its floor known as the Challenger Deep. However, some unrepeated measurements place the deepest portion at 11,034 metres (36,201 ft). By comparison: if Mount Everest were placed into the trench at this point, its peak would still be over two kilometres (1.2 mi) under water.At the bottom of the trench the water column above exerts a pressure of 1,086 bars (15,750 psi), more than 1,000 times the standard atmospheric pressure at sea level. At this pressure, the density of water is increased by 4.96%, so that 95.27 of any unit of volume of water under the pressure of the Challenger Deep would contain the same mass as 100 of those units at the surface. The temperature at the bottom is 1 to 4 °C (34 to 39 °F).The trench is not the part of the seafloor closest to the center of the Earth. This is because the Earth is an oblate spheroid, not a perfect sphere; its radius is about 25 kilometres (16 mi) smaller at the poles than at the equator. As a result, parts of the Arctic Ocean seabed are at least 13 kilometres (8.1 mi) closer to the Earth's center than the Challenger Deep seafloor.

In 2009, the Marianas Trench was established as a United States National Monument. Xenophyophores have been found in the trench by Scripps Institution of Oceanography researchers at a record depth of 10.6 kilometres (6.6 mi) below the sea surface. Data has also suggested that microbial life forms thrive within the trench.

Micronesia

Micronesia ((UK: , US: ); from Greek: μικρός mikrós "small" and Greek: νῆσος nêsos "island") is a subregion of Oceania, composed of thousands of small islands in the western Pacific Ocean. It has a close shared cultural history with two other island regions: Polynesia to the east and Island Melanesia to the south; as well as the wider Austronesian peoples.

The region has a tropical marine climate and is part of the Oceania ecozone. There are five main archipelagos—the Caroline Islands, the Gilbert Islands, the Line Islands, the Mariana Islands, and the Marshall Islands—along with numerous outlying islands.

Politically, the islands of Micronesia are divided between six sovereign nations: the Caroline Islands are divided between the Republic of Palau and the Federated States of Micronesia, the latter often shortened to "FSM" or "Micronesia" and not to be confused with the overall region; the Gilbert Islands and the Line Islands comprise the Republic of Kiribati, except for three of the Line Islands that are United States territories (Palmyra Atoll being noteworthy as the only current incorporated U.S. Territory); the Mariana Islands are in union with the United States, divided between the U.S. Territory of Guam and the U.S. Commonwealth of the Northern Mariana Islands; Nauru is a fully sovereign nation, coextensive with the island of the same name; and the Republic of the Marshall Islands is coextensive with that island group. Also noteworthy is Wake Island, which is claimed by both the Republic of the Marshall Islands and the United States, the latter having actual possession under immediate administration of the United States Air Force.

Human settlement of Micronesia began several millennia ago. There are competing theories about the origin(s) and arrival of the first Micronesians. The earliest known contact with Europeans occurred in 1521, when Spanish ships landed in the Marianas. The term "Micronesia" is usually attributed to Jules Dumont d'Urville's use of it in 1832, but Domeny de Rienzi had used the term a year previously.

Oceanic trench

Oceanic trenches are topographic depressions of the sea floor, relatively narrow in width, but very long. These oceanographic features are the deepest parts of the ocean floor. Oceanic trenches are a distinctive morphological feature of convergent plate boundaries, along which lithospheric plates move towards each other at rates that vary from a few millimeters to over ten centimeters per year. A trench marks the position at which the flexed, subducting slab begins to descend beneath another lithospheric slab. Trenches are generally parallel to a volcanic island arc, and about 200 km (120 mi) from a volcanic arc. Oceanic trenches typically extend 3 to 4 km (1.9 to 2.5 mi) below the level of the surrounding oceanic floor. The greatest ocean depth measured is in the Challenger Deep of the Mariana Trench, at a depth of 11,034 m (36,201 ft) below sea level. Oceanic lithosphere moves into trenches at a global rate of about 3 km2/yr.

Outline of oceanography

The following outline is provided as an overview of and introduction to Oceanography.

Outline of plate tectonics

This is a list of articles related to plate tectonics and tectonic plates.

Philippine Sea Plate

The Philippine Sea Plate or the Philippine Plate is a tectonic plate comprising oceanic lithosphere that lies beneath the Philippine Sea, to the east of the Philippines. Most segments of the Philippines, including northern Luzon, are part of the Philippine Mobile Belt, which is geologically and tectonically separate from the Philippine Sea Plate.

Philippine Sea plate is bordered mostly by convergent boundaries:

To the north, the Philippine Sea Plate meets the Okhotsk Plate at the Nankai Trough. The Philippine Sea Plate, the Amurian Plate, and the Okhotsk Plate meet at Mount Fuji in Japan. The thickened crust of the Izu-Bonin-Mariana arc colliding with Japan constitutes the Izu Collision Zone.

To the east, Philippine Sea Plate meets the Pacific Plate, subducting at the Izu-Ogasawara Trench. The east of the plate includes the Izu-Ogasawara (Bonin) and the Mariana Islands, forming the Izu-Bonin-Mariana Arc system. There is also a divergent boundary between the Philippine Sea Plate and the small Mariana Plate which carries the Mariana Islands.

To the south, the Philippine Sea Plate is bounded by the Caroline Plate and Bird's Head Plate.

To the west, the Philippine Sea Plate subducts under the Philippine Mobile Belt at the Philippine Trench and the East Luzon Trench. (The adjacent rendition of Prof. Peter Bird's map is inaccurate in this respect.)

To the northwest, the Philippine Sea Plate meets Taiwan and the Nansei islands on the Okinawa Plate, and southern Japan on the Amurian Plate.

South Chamorro Seamount

South Chamorro Seamount is a large serpentinite mud volcano and seamount located in the Izu-Bonin-Mariana Arc, one of 16 such volcanoes in the arc. These seamounts are at their largest 50 km (31 mi) in diameter and 2.4 km (1.5 mi) in height. Studies of the seamount include dives by the submersible dives (DSV Shinkai, 1993 and 1997), drilling (Ocean Drilling Program, 2001) and (International Ocean Discovery Program, 2016-2017), and ROV dives (2003, 2009).The seamount and its nearby peers were created by the movement of crushed rock, resulting from plate movement, upwards through fissures in the Mariana Plate. South Chamorro is the farthest of the mud volcanoes from the trench, at a distance of 85 km (53 mi), resulting in high-temperature flows rich in sulfate and methane. The seamount suffered a major flank collapse on its southeastern side, over which the present summit was probably formed. The summit supports an ecosystem of mussels, gastropods, tube worms, and others, suggesting that it is an active seeping region.

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