In ocean-ocean convergence, melting occurs at about 62 kilometers depth, contributing to the formation of?

• A. Volcanic island arcs
• B. Mountain belts on continents
• C. Mid-ocean ridges
• D. Transform faults

Answer: (A)

In ocean-ocean convergence, the subducting oceanic plate releases fluids as it descends. Those fluids lower the melting point of the overlying mantle in the mantle wedge, causing partial melting at considerable depth. The resulting magma then rises and feeds volcanic activity on the overriding plate, producing a chain of volcanoes. When these volcanoes erupt at the surface, they form a volcanic island arc. This arc form is characteristic of subduction zones where one ocean plate dives beneath another.

This is different from mountain belts formed by continent-continent collision, mid-ocean ridges created by seafloor spreading at divergent boundaries, or transform faults produced by horizontal sliding along transform boundaries, which do not generate island arcs.