Nazca Plate

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Nazca Plate
NazcaPlate.png
Type Minor
Approximate area15,600,000 km2 [1]
Movement1north-east
Speed140-53mm/year
Features Pacific Ocean
1Relative to the African Plate

The Nazca Plate, or Nasca Plate [2] , named after the Nazca region of southern Peru, is an oceanic tectonic plate in the eastern Pacific Ocean basin off the west coast of South America. The ongoing subduction, along the Peru–Chile Trench, of the Nazca Plate under the South American Plate is largely responsible for the Andean orogeny. The Nazca Plate is bounded on the west by the Pacific Plate and to the south by the Antarctic Plate through the East Pacific Rise and the Chile Rise respectively. The movement of the Nazca Plate over several hotspots has created some volcanic islands as well as east-west running seamount chains that subduct under South America. Nazca is a relatively young plate both in terms of the age of its rocks and its existence as an independent plate having been formed from the break-up of the Farallon Plate about 23 million years ago. The oldest rocks of the plate are about 50 million years old. [3]

Contents

Boundaries

East Pacific and Chile Rise

A triple junction, the Chile Triple Junction, [4] occurs on the seafloor of the Pacific Ocean off Taitao and Tres Montes Peninsula at the southern coast of Chile. Here three tectonic plates meet: the Nazca Plate, the South American Plate, and the Antarctic Plate.

Peru–Chile Trench

The eastern margin is a convergent boundary subduction zone under the South American Plate and the Andes Mountains, forming the Peru–Chile Trench. The southern side is a divergent boundary with the Antarctic Plate, the Chile Rise, where seafloor spreading permits magma to rise. The western side is a divergent boundary with the Pacific Plate, forming the East Pacific Rise. The northern side is a divergent boundary with the Cocos Plate, the Galapagos Rise.

The subduction of the Nazca plate under southern Chile has a history of producing massive earthquakes, including the largest ever recorded on earth, the moment magnitude 9.5 1960 Valdivia earthquake.

Intraplate features

Hotspots

A second triple junction occurs at the northwest corner of the plate where the Nazca, Cocos, and Pacific Plates all join off the coast of Colombia. Yet another triple junction occurs at the southwest corner at the intersection of the Nazca, Pacific, and Antarctic Plates off the coast of southern Chile. At each of these triple junctions an anomalous microplate exists, the Galapagos Microplate at the northern junction and the Juan Fernandez Microplate at the southern junction. The Easter Island Microplate is a third microplate that is located just north of the Juan Fernandez Microplate and lies just west of Easter Island.

Aseismic ridges

The Carnegie Ridge is a 1,350-km-long and up to 300-km-wide feature on the ocean floor of the northern Nazca Plate that includes the Galápagos archipelago at its western end. It is being subducted under South America with the rest of the Nazca Plate.

Fracture zones

The Darwin Gap is the area between the Nazca Plate and the coast of Chile, where Charles Darwin experienced the earthquake of 1835. It is expected that this area will be the epicenter of a major quake in the near future. [5]

Plate motion

The absolute motion of the Nazca Plate has been calibrated at 3.7 cm/yr east motion (88°), one of the fastest absolute motions of any tectonic plate. The subducting Nazca Plate, which exhibits unusual flat-slab subduction, is tearing as well as deforming as it is subducted (Barzangi and Isacks). The subduction has formed, and continues to form, the volcanic Andes Mountain Range. Deformation of the Nazca Plate even affects the geography of Bolivia, far to the east (Tinker et al.). The 1994 Bolivia earthquake occurred on the Nazca Plate; this had a magnitude of 8.2 , which at that time was the strongest instrumentally recorded earthquake occurring deeper than 300 km.

Aside from the Juan Fernández Islands, this area has very few other islands that are affected by the earthquakes that are a result of complicated movements at these junctions.

Geologic history

The precursor of both the Nazca Plate and the Cocos Plate (to its north) was the Farallon Plate, which split in the late Oligocene, about 22.8 Mya, a date arrived at by interpreting magnetic anomalies. Subduction under the South American continent began about 140 Mya, although the formation of the high parts of the Central Andes and the Bolivian orocline did not occur until 45 Mya. It has been suggested that the mountains were forced up by the subduction of the older and heavier parts of the plate, which sank more quickly into the mantle. [6]

See also

Related Research Articles

Antarctic Plate A tectonic plate containing the continent of Antarctica and extending outward under the surrounding oceans

The Antarctic Plate is a tectonic plate containing the continent of Antarctica, the Kerguelen Plateau and extending outward under the surrounding oceans. After breakup from Gondwana, the Antarctic plate began moving the continent of Antarctica south to its present isolated location causing the continent to develop a much colder climate. The Antarctic Plate is bounded almost entirely by extensional mid-ocean ridge systems. The adjoining plates are the Nazca Plate, the South American Plate, the African Plate, the Somali Plate, the Indo-Australian Plate, the Pacific Plate, and, across a transform boundary, the Scotia Plate.

Cocos Plate 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.

The Peru–Chile Trench, also known as the Atacama Trench, is an oceanic trench in the eastern Pacific Ocean, about 160 kilometres (100 mi) off the coast of Peru and Chile. It reaches a maximum depth of 8,065 m (26,460 ft) below sea level in Richards Deep and is approximately 5,900 km (3,700 mi) long; its mean width is 64 km (40 mi) and it covers an expanse of some 590,000 km2 (230,000 sq mi).

East Pacific Rise A mid-oceanic ridge at a divergent tectonic plate boundary on the floor of the Pacific Ocean

The East Pacific Rise is a mid-oceanic ridge, a divergent tectonic plate boundary located along the floor of the Pacific Ocean. It separates the Pacific Plate to the west from the North American Plate, the Rivera Plate, the Cocos Plate, the Nazca Plate, and the Antarctic Plate. It runs south from the Gulf of California in the Salton Sea basin in Southern California to a point near 55° S, 130° W, where it joins the Pacific-Antarctic Ridge trending west-southwest towards Antarctica, near New Zealand. Much of the rise lies about 3200 km (2000 mi) off the South American coast and rises about 1,800–2,700 m (6,000–9,000 ft) above the surrounding seafloor.

Triple junction The point where the boundaries of three tectonic plates meet

A triple junction is the point where the boundaries of three tectonic plates meet. At the triple junction each of the three boundaries will be one of 3 types - a ridge (R), trench (T) or transform fault (F) - and triple junctions can be described according to the types of plate margin that meet at them. Of the many possible types of triple junction only a few are stable through time. The meeting of 4 or more plates is also theoretically possible but junctions will only exist instantaneously.

Carnegie Ridge An aseismic ridge on the Nazca Plate that is being subducted beneath the South American Plate

The Carnegie Ridge is an aseismic ridge on the Nazca Plate that is being subducted beneath the South American Plate. The ridge is thought to be a result of the passage of the Nazca Plate over the Galapagos hotspot. It is named for the research vessel Carnegie, which discovered it in 1929.

Chile Rise An oceanic ridge at the tectonic divergent plate boundary between the Nazca and Antarctic plates

The Chile Rise or Chile Ridge is an oceanic ridge, a tectonic divergent plate boundary between the Nazca and Antarctic plates. Its eastern end is the Chile Triple Junction where the Chile Rise is being subducted below the South American Plate in the Peru–Chile Trench. It runs westward to a triple point south of the Juan Fernández Microplate where it intersects the East Pacific Rise.

Galápagos Microplate A very small tectonic plate at the Galapagos Triple Junction

The Galapagos Microplate (GMP) is a geological feature of the oceanic crust located at 1°50' N, offshore of the west coast of Colombia. The GMP is collocated with the Galapagos Triple Junction, which is an atypical ridge-ridge-ridge triple junction. At the Galapagos Triple Junction, the Pacific Plate, Cocos Plate, and Nazca Plate meet incompletely, forming two counter-rotating microplates at the junction of the Cocos-Nazca, Pacific-Cocos, and Pacific-Nazca spreading ridges.

Andean Volcanic Belt Volcanic belt in South America

The Andean Volcanic Belt is a major volcanic belt along the Andean cordillera in Argentina, Bolivia, Chile, Colombia, Ecuador, and Peru. It is formed as a result of subduction of the Nazca Plate and Antarctic Plate underneath the South American Plate. The belt is subdivided into four main volcanic zones that are separated from each other by volcanic gaps. The volcanoes of the belt are diverse in terms of activity style, products, and morphology. While some differences can be explained by which volcanic zone a volcano belongs to, there are significant differences within volcanic zones and even between neighboring volcanoes. Despite being a type location for calc-alkalic and subduction volcanism, the Andean Volcanic Belt has a broad range of volcano-tectonic settings, as it has rift systems and extensional zones, transpressional faults, subduction of mid-ocean ridges and seamount chains as well as a large range of crustal thicknesses and magma ascent paths and different amounts of crustal assimilations.

Galápagos hotspot

The Galápagos hotspot is a volcanic hotspot in the East Pacific Ocean responsible for the creation of the Galapagos Islands as well as three major aseismic ridge systems, Carnegie, Cocos and Malpelo which are on two tectonic plates. The hotspot is located near the Equator on the Nazca Plate not far from the divergent plate boundary with the Cocos Plate. The tectonic setting of the hotspot is complicated by the Galapagos Triple Junction of the Nazca and Cocos plates with the Pacific Plate. The movement of the plates over the hotspot is determined not solely by the spreading along the ridge but also by the relative motion between the Pacific Plate and the Cocos and Nazca Plates.

Geology of Chile

The geology of Chile is a characterized by processes linked to subduction such as volcanism, earthquakes and orogeny. The buildings blocks of Chile's geology assembled during the Paleozoic Era. Chile was by then the southwestern margin of the supercontinent Gondwana. In the Jurassic Gondwana begun to split and the ongoing period of crustal deformation and mountain building known as the Andean orogeny begun. In the Late Cenozoic Chile definitely separated from Antarctica, the Andes expienced a great rise accomplained by a cooling climate and the onset of glaciations.

Macquarie Triple Junction Place where the Indo-Australian Plate, Pacific Plate, and Antarctic Plate meet

The Macquarie Triple Junction is a geologically active tectonic boundary located at 61°30′S161°0′E at which the Indo-Australian Plate, Pacific Plate, and Antarctic Plate collide and interact. The term Triple Junction is given to particular tectonic boundaries at which three separate tectonic plates meet at a specific, singular location. The Macquarie Triple Junction is located on the seafloor of the southern region of the Pacific Ocean, just south of New Zealand. This tectonic boundary was named in respect to the nearby Macquarie Island, which is located southeast of New Zealand.

The Chile Triple Junction is a geologic triple junction located on the seafloor of the Pacific Ocean off Taitao and Tres Montes Peninsula on the southern coast of Chile. Here three tectonic plates meet: the South American Plate, the Nazca Plate, and the Antarctic Plate. This triple junction is unusual in that it consists of a mid-oceanic ridge, the Chile Rise, being subducted under the South American Plate at the Peru–Chile Trench.

Pacific-Farallon Ridge A spreading ridge during the late Cretaceous that separated the Pacific Plate to the west and the Farallon Plate to the east

The Pacific-Farallon Ridge was a spreading ridge during the late Cretaceous that extended 10,000 km in length and separated the Pacific Plate to the west and the Farallon Plate to the east. It ran south from the Pacific-Farallon-Kula triple junction at 51°N to the Pacific-Farallon-Antarctic triple junction at 43°S. As the Farallon Plate subducted obliquely under the North American Plate, the Pacific-Farallon Ridge approached and eventually made contact with the North American Plate about 30 million years ago. On average, this ridge had an equatorial spreading rate of 13.5 cm per year until its eventual collision with the North American Plate. In present day, the Pacific-Farallon Ridge no longer formally exists since the Farallon Plate has been broken up or subducted beneath the North American Plate, and the ridge has segmented, having been mostly subducted as well. The most notable remnant of the Pacific-Farallon Ridge is the 4000 km Pacific-Nazca segment of the East Pacific Rise.

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.

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

Andean orogeny Ongoing mountain-forming process in South America

The Andean orogeny is an ongoing process of orogeny that began in the Early Jurassic and is responsible for the rise of the Andes mountains. The orogeny is driven by a reactivation of a long-lived subduction system along the western margin of South America. On a continental scale the Cretaceous and Oligocene were periods of re-arrangements in the orogeny. Locally the details of the nature of the orogeny varies depending on the segment and the geological period considered.

Geology of the Pacific Ocean overview about the 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.

References

  1. "Sizes of Tectonic or Lithospheric Plates". About.com Geology. Retrieved 4 January 2016.
  2. Oxford Atlas Of The World 26th Ed. New York, NY: Oxford University Press. 2019. p. 74. ISBN   978-0-19-006581-2.
  3. Dutch, Steven. "Sea Floor Spreading in the Pacific".
  4. Kelly McGuire (8 April 2004). "Tectonics of South America: Chile Triple Junction" (PDF). Retrieved 27 February 2016.
  5. Kate Ravilious (30 Jan 2011). "Darwin Gap quake will shake Chile again". New Scientist. Retrieved 8 Feb 2011.
  6. "Mountains on a plate form the Andes" (Issue No:214). University World News. 25 March 2012. Retrieved 8 February 2016.
Bibliography

Coordinates: 15°00′00″S85°00′00″W / 15.00000°S 85.00000°W / -15.00000; -85.00000