Subduction

thumb|upright=1.85|Diagram of the geological process of subduction

depressions of the sea floor

sediments accreted onto the non-subducting tectonic plate at a convergent plate boundary

thumb|Cerro Mackay, a mountain in Coyhaique in Chile, made of columns of adakite thumb|Closer view of the adakite columns of Cerro Mackay, Chile Adakites are volcanic rocks of intermediate to felsic composition that have geochemical characteristics of magma originally thought to have formed by partial melting of altered basalt that is subducted below volcanic arcs. Most magmas derived in subduction zones come from the mantle above the subducting plate when hydrous fluids are released from minerals that break down in the metamorphosed basalt, rise into the mantle, and initiate partial melting.

thumb|275x275px|Cross-section of a subduction zone and back-arc basin. The forearc is the region between the trench and the volcanic arc.

subdivision of the subalkaline magma series

geology: portion of a tectonic plate that is being subducted

changes of rock due to pressure and heat near a subduction zone

term in Geology