- a curved chain of islands, as the Aleutians or Antilles, usually convex toward the ocean and enclosing a deep-sea basin.
- an arc-shaped chain of islands, such as the Aleutian Islands or the Japanese Islands, usually lying at the edge of a Benioff zone, indicating volcanic activity where the oceanic lithosphere is descending into the earth’s interior
- 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.