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 ?
With an average interval of more than 500 years and the last subduction zone quake striking 315 years ago, it's tempting to conclude that the Oregon Coast is in the midst of a period of relative safety, and that OSU's new building and other structures in the tsunami inundation zone are likely to stay dry for a century or more.
Subduction zones are where plate boundaries meet and when one plate sinks beneath the other, going into Earth's interior.
Those veins, along with other characteristics of the rocks, indicate that seismic activity along the ancient subduction zone occurred at depths of 4 km and greater, says Remitti.
We don't yet understand the slow-slip processes that cause faults to behave in this way, and we don't know very much about their relationship to large subduction zone earthquakes," says expedition co-leader Demian Saffer of PennState.
Researchers said they were working to determine just how much of a risk the Hikurangi subduction zone is to New Zealand.
The other, the Cascadia subduction zone, runs along the Pacific Coast on the western borders of Oregon and Washington.
Movement in the Cascadia subduction zone that runs offshore from northern California to British Columbia triggers these large earthquakes at irregular intervals, approximately every 200 to 400 years.
The synoptic model of the Central American subduction zone by Lucke (2012) features the overall geometry of boundary surfaces and first order tectonic discontinuities of the convergent margin, such as the subducted slab of the Cocos plate.
Here, the Nazca plate plunges beneath the South American plate, forming a subduction zone.
Twenty-five minutes isn't long to find shelter from a tsunami, but that's how long Washington state residents living in coastal areas would have if a major earthquake hit the Cascasia Subduction Zone, a 700-mile-long fault on the US West Coast where the Juan de Fuca Plate is pushed under the North American Plate.
These high concentrations of dissolved carbon species, previously unknown at great depth in Earth, suggest they are helping to ferry large amounts of carbon from the subduction zone into the overlying mantle wedge where they are likely to alter the mantle and affect the cycling of elements back into Earth's atmosphere.
The action resembles a subduction zone on Earth, where one slab of crust--or tectonic plate--slides beneath another.