How would you discribe a subduction zone?

Question

please give details

Answer 1

subduction zone




large-scaled narrow region in the earth's crust where, according to plate tectonics, 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.

Answer 2

A subduction zone is where (most commonly) and oceanic plate is subducted beneath a continental plate, or where (much less commonly) an oceanic plate is subducted beneath another oceanic plate. There is a possible third scenario, and that is where a continental plate is subducted beneath a continental plate, but this usually results in suturing of the two plates with minor subduction. Also, an oceanic plate can be thrusted onto a continental plate, the there is no subduction here.

Answer 3

i think of the methods that initiate a subduction zone are the comparable ones that shop it going. There are super convection cells that seem to hold the crust alongside. And at spreading centers the upwelling that types new crust creates slightly bit a topographic extreme (a.ok.a. mid-ocean ridge), so i'm particular gravity performs a place in plate action, too, enormously for oceanic plates. As to what could reason decoupling of a passive margin to style a subduction zone, the finest answer could be that the forces appearing on the oceanic crustal section grow to be reliable sufficient relative to the forces appearing on the remainder of the plate to interrupt the section. i'm particular some deformation happens as properly as breakage. And, because of the fact that mom Nature's heterogeneity has a tendency to bring about imprecision, this breakage won't continuously happen at an actual boundary between oceanic and continental crust. subsequently, there's a lot of oceanic crust uncovered on the western coast of the U. S.. i've got seen it in California as a techniques inland because of the fact the Sierra Nevadas and in Alaska, and assume this is uncovered someplace else. It’s been stated that the Puerto Rican Trench may well be at the instant extending itself to style a subduction zone than might desire to finally amplify alongside the full jap fringe of North usa and South usa. the present trench seems to have began at a remodel margin, the place plate segments are shifting previous one yet another. slightly bit transpression because of the fact the segments on the two length of the remodel are pressed in the direction of one yet another (possibly via action of alternative plates), slightly bit up-and-down, and we've ourselves a subduction zone. yet another style of dividing of a plate is taking place in Baja California, in the Gulf of Cortez (a.ok.a. the Gulf of California). A spreading center is docking with the North American plate, and the combination of spreading and remodel action has further approximately the hollow of the Gulf as properly because of the fact the formation of the San Andreas Fault. Africa is being pulled aside alongside the East Africa Rift. The rifting there seems to have been preceded via the eruption of flood basalts and is a results of the formation of a clean spreading center. Such new spreading centers don’t continuously gain tearing continents aside; the Mississippi Vallley seems to be a failed rift device. There seems sufficient variability in the composition of the crust and in the dynamics of the convection to permit very almost any style of plate replace we are able to think of.