island arc - Island arcs

Oceanic islands occurring in arc-shaped chains, such as the Aleutians, Mariana, Lesser Antilles, S Sandwich, and Tonga-Kermadec Is. They usually contain active volcanoes, and are adjacent to deep ocean trenches. The theory of plate tectonics maintains that island arcs are formed by volcanism generated as the rigid plates making up the Earth's surface are recycled into the Earth's interior beneath the trenches.

An island arc is a type of archipelago formed by plate tectonics as one oceanic tectonic plate subducts under another and produces magma. Island arcs that develop along the edges of a continent (for example, large parts of the Andes/ Central American/ Canadian mountain chain) may be known as a volcanic arc, though most people find the distinction of little benefit. The resulting volcano chain has the shape of an arc parallel to the convergent plate boundary and convex toward the subducting plate.

On the subducting side of the island arc is a deep and narrow oceanic trench, which is the trace at the Earth’s surface of the boundary between the downgoing and overriding plates. This trench is created by the friction of the subducting plate pulling the leading edge of the overriding plate downward. Multiple earthquakes occur along this subduction boundary with the seismic epicenters located at increasing depth under the island arc.

Island arcs

Aleutian Islands Kurile Islands Japan Philippines Marianas Islands Tonga and Kermadec Islands Ryūkyū Islands Ogasawara Islands Crete and Dodecanese Andaman and Nicobar Islands Mentawai Islands Lesser Sunda Islands Tanimbar and Kai Islands Solomon Islands Lesser Antilles, including the Leeward Antilles South Georgia and the South Sandwich Islands Sunda Arc New Zealand