Which type of material becomes molten rock at subduction zones? light plates heavy plates continental crust new oceanic crust

Continental crust

Explanation:

The main mechanism of formation of the molten rock is by partial fusion of the rocks that form the upper portion of the terrestrial mantle. This fusion of the solid rocks to form the magma is controlled by three physical parameters: (1) its temperature; (2) its pressure; and (3) its composition.

At any given pressure and for any rock composition, an increase in temperature after the solidus point will cause melting. Inside the solid continental crust, the temperature of a rock is controlled by the geothermal gradient and the radioactive decay within the rock. The average values of the geothermal gradient range around 25 ° C / km, with a wide range ranging from a minimum of 5-10 ° C / km in the ocean trenches and in the subduction zones, to a maximum of 30- 80 ° C / km under the ocean ridges and in volcanic arc environments.

The pressure is the other of the factors that determine the fusion, and by this way the formation of the magmas. When the heated material rises by convection which induces flotation and crosses the solidus-liquidus barrier, its temperature is reduced by adiabatic cooling. When this happens, the rock liquefies by melting, turning into molten rock when it reaches the surface. The melt may also result from the reduction of the pressure, in a phenomenon known as decompression fusion.

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