Where do subduction zones occur? What happens at them? What becomes of a subducted plate edge?
Subduction zones occur at convergent plate boundaries, where two tectonic plates collide. There are three types of convergent plate boundaries: oceanic-continental, oceanic-oceanic, and continental-continental.
In an oceanic-continental subduction zone, an oceanic plate dives beneath a continental plate due to the differences in density. The denser oceanic plate is forced beneath the less dense continental plate. This process forms a deep oceanic trench, such as the Peru-Chile Trench along the western coast of South America. As the oceanic plate sinks deeper into the mantle, it undergoes intense heat and pressure, causing melting. The molten rock, known as magma, rises through the continental crust, leading to volcanic eruptions. This volcanic activity is responsible for the formation of volcanic arcs, like the Andes Mountains.
In an oceanic-oceanic subduction zone, two oceanic plates converge, and one subducts beneath the other. This type of subduction can lead to the formation of volcanic island arcs, such as the Aleutian Islands in Alaska or the Japanese archipelago.
In a continental-continental subduction zone, two continental plates collide, and neither subducts. Instead, the intense pressure and compression result in the formation of mountain ranges, like the Himalayas.
As for what becomes of a subducted plate edge, it eventually sinks deep into the mantle, where it experiences high temperatures and pressures. The subducted plate edge can undergo partial melting, contributing to the formation of magma chambers. Some of this magma eventually rises to the surface, resulting in volcanic activity at the subduction zone.
Subduction zones are commonly found around the edges of tectonic plates, where one plate is forced underneath another plate. They occur primarily at convergent plate boundaries, where two plates are moving towards each other.
At a subduction zone, two possible scenarios can happen depending on the type of plates involved. If an oceanic plate is subducting beneath a continental plate, the denser oceanic plate will sink beneath the less dense continental plate. This leads to the formation of a deep oceanic trench, which is a long, narrow depression on the seafloor. Additionally, the subduction process can cause intense compression and deformation of the overriding plate, leading to the formation of mountain ranges.
In the case of two oceanic plates colliding, a similar process occurs. The older and colder oceanic plate will subduct beneath the younger and hotter plate. This creates a volcanic arc, which is a chain of volcanoes formed along the plate boundary. These volcanic arcs often give rise to island chains.
As for the fate of the subducted plate, it depends on its composition and the depth at which it is subducted. At shallow depths, the plate materials may undergo partial melting, which can produce magma that rises to the surface, eventually creating volcanoes. In some cases, the subducted plate can sink deeper into the Earth's mantle, where it may undergo further chemical changes or be recycled into the mantle over time through geological processes.