GENERAL GEOLOGY

Detailed explanation-1: -These plates collide, slide past, and move apart from each other. Where they collide and one plate is thrust beneath another (a subduction zone), the most powerful earthquakes, tsunamis, volcanic eruptions, and landslides occur.

Detailed explanation-2: -Volatile-driven melting happens at all subduction zones. The melt is generally formed at the point when the slab gets to a certain depth (the depth at which the pressure becomes high enough to force out the water). Pencast of a plot in Pressure-Temperature space for volatile-driven melting!

Detailed explanation-3: -In most subduction zones, substantial partial melting of subducting oceanic crust will only occur if high shear stresses ( > ∼ 100 MPa) can be maintained by rocks close to, or above, their melting temperatures.

Detailed explanation-4: -The water gradually seeps upward into the overlying wedge of hot mantle. The addition of water to the already hot mantle rocks lowers their melting temperature resulting in partial melting of ultramafic mantle rocks to yield mafic magma.