subduction zone


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subduction zone,

large-scaled narrow region in the earth's crust where, according to plate tectonicsplate tectonics,
theory that unifies many of the features and characteristics of continental drift and seafloor spreading into a coherent model and has revolutionized geologists' understanding of continents, ocean basins, mountains, and earth history.
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, masses of the spreading oceanic lithosphere bend downward into the earth along the leading edges of converging lithospheric plates where it slowly melts at about 400 mi (640 km) deep and becomes reabsorbed. Subduction zones are usually marked by deep ocean trenches that often exceed 6 mi (10 km) compared to the ocean's overall depth of 2 to 4 mi (3 to 5 km). A pattern of earthquakes of shallow, intermediate, and deep focus occurs along the same angle as the descending plate, which is steeply inclined (30°–60°) toward the continent behind the trench in a zone called the Benioff Zone, discovered by the U.S. seismologist Hugo Benioff. This earthquake pattern enables geophysicists to trace the descending plate to depths of 600 to 700 km (370–440 mi), where temperatures are thought to be between 1,000°C; and 2,000°C; (1,800°–3,600°F;). As the oceanic plate descends, friction between the two plates probably causes partial melting of the descending plate forming a magma of andesitic composition that rises along fractures. If the overlying crustal plate is oceanic, the magma may erupt to form volcanic island arcs, such as Japan or the Aleutians. If the overlying plate is continental, a line of batholiths and volcanoes may be created as in the Coast Ranges of Canada and the W United States. See continentcontinent,
largest unit of landmasses on the earth. The continents include Eurasia (conventionally regarded as two continents, Europe and Asia), Africa, North America, South America, Australia, and Antarctica.
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; continental driftcontinental drift,
geological theory that the relative positions of the continents on the earth's surface have changed considerably through geologic time. Though first proposed by American geologist Frank Bursley Taylor in a lecture in 1908, the first detailed theory of
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; seafloor spreadingseafloor spreading,
theory of lithospheric evolution that holds that the ocean floors are spreading outward from vast underwater ridges. First proposed in the early 1960s by the American geologist Harry H.
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References in periodicals archive ?
"Subduction zone earthquakes often produce large tsunamis because there are large and rapid displacements of the seafloor," GNS earthquake geologist Kate Clark told the (http://www.nzherald.co.nz/nz/news/article.cfm?c_id=1&objectid=11931364) New Zealand Herald .
This Cascadia subduction zone last generated a magnitude-9.0 earthquake in the Pacific Northwest in 1700, and based on what we know about the frequency of such quakes, Hayes said that another one of similar strength could occur any day now.
The deep structure of the subduction zone for the Cocos Ridge segment is less constrained with receiver function data by Dzierma et al.
* CHILE: As the only segment of the Chile-Peru Subduction Zone not to have ruptured within the last 100 years, the north Chile segment is now considered to be a region at high risk from an earthquake similar in size to the 2010 event.
* Chile - As the only segment of the Chile-Peru Subduction Zone not to have ruptured within the last 100 years, the north Chile segment is now considered to be a region at high risk from an earthquake similar in size to the 2010 event.
Several studies have shown that this subduction zone may exhibit lateral variations in the dip angle of the subducted oceanic lithospere as well as changes in the distribution of seismicity along and down dip the trench, specially at intermediate depths (between the latitudes 3[degrees]N-4[degrees]N), where a seismic gap is apparent (Pennington, 1981; Taboada et al., 1998; Monsalve, 1998; Gutscher et al., 1999, Vargas et al., 2003, Mejia and Meyer, 2004, Chicangana and Vargas, 2004).
During a prolonged history of subduction, the dip and location of the subduction zone may vary causing the locus of arc magmatism to migrate and causing intermittent switching from compressional to extensional environments.
The Indian Ocean earthquake occurred between the Eurasian and Indian plates along a subduction zone, an area where one plate tries to dive beneath another.
Groat warned that there is a 10 to 14 percent chance in the next 50 years of an earthquake in the Cascadia subduction zone that could generate a massive tsunami off the Oregon coast.
Indonesia is located in the mid of tectonic plate collision of Indo-Australia, Eurasia and Pacific Plates where subduction zone was formed and generates active volcanoes and active faults resulting earthquakes and volcanic eruptions.
The Pacific Coast from northern British Columbia to Punta Gorda, near Cape Mendocino in California's Humboldt County, is the region known to geologists as the Cascadia Subduction Zone. There, two large slabs of the Earth's crust called the Juan de Fuca and the Gorda plates have been diving ponderously down beneath the North American continental plate for millions of years.
The 500-km-long Nankai Trough, a vigorous subduction zone from the Kii Peninsula to the western Izu Peninsula, has had large-scale earthquakes every 100 to 200 years.