A usually curved chain of volcanic islands occurring on the overriding tectonic plate of a subduction zone, bounded on the convex side by a deep oceanic trench, and formed by magma that rises from the melting of the descending plate.
A usually curved chain of volcanic islands bounded on the convex side by a deep oceanic trench. Island arcs form in the overriding tectonic plates of subduction zones as the result of rising melt from the downgoing plate. The arcs are curved because of the curvature of the Earth. The Aleutian Islands, in Alaska, are an island arc. An island arc is a kind of volcanic arc.