What is a Subduction Zone?
A subduction zone is a convergent boundary where two tectonic plates collide. Plates are large, dense masses in the crust of the earth, the lithosphere, that float on top of liquefied rock in the asthenosphere. They are constantly shifting and moving, so when they subduct, one pushes beneath the other. Subduction zones create geologic formations such as mountain ranges, ocean trenches, and island arcs, as well as phenomena like earthquakes and volcanoes. Tectonic plates are categorized as either oceanic plates that have large bodies of water above them or continental plates that support land. Geologists have learned about how subduction zones work by studying earthquakes in seismology and volcanoes in volcanology. They know that younger plates are less dense than older plates. Generally, ocean crust is thinner and denser than continental crust. Subduction zones don’t only make certain landscape changes, but they recycle rock by melting it into magma so that crust might form at other te
Geometry and Geophysics | Magmatic Processes | Forearc Processes | Back-arc Processes | Orogeny Subduction zones are regions of the Earth that are defined by deep trenches, lines of volcanoes parallel to the trenches, and zones of large earthquakes dipping from the trenches landward beneath the volcanoes. Plate tectonic theory recognizes that the earth s surface is composed of a mosaic of interacting lithospheric plates, where the lithosphere consists of the crust (continental or oceanic) and associated mantle, for a total thickness of about 100km (60 miles). Oceanic plates are created at mid-ocean ridges (divergent or accretionary plate boundaries) by seafloor spreading and destroyed at convergent or destructive plate boundaries, the subsurface continuations of which are known as subduction zones (Fig. I-1; take a look at a global bathymetric and topographic map at http://ibis.grdl.noaa.gov/cgi-bin/bathy/bathD.pl) Continental crust is produced at subduction zones. At subduction zones,
