island arc

Curved chain of volcanic islands. Island arcs are common in the Pacific where they ring the ocean on both sides; the Aleutian Islands off Alaska are an example. The volcanism that forms island arcs is a result of subduction of an oceanic plate beneath another plate, as evidenced by the presence of ocean trenches on the convex side of the arc, and the Benioff zone of high seismic activity beneath.

Such island arcs are often later incorporated into continental margins during mountain-building episodes.