Island Arcs

Introduction
Island arcs are volcanic islands that form parallel to ocean trenches in subduction zones. The Pacific Ring of Fire is home to many of these groups of islands. Volcanoes that form above hot spots like the Hawaiian islands are not volcanic arcs.

Volcanic island eruption, USGS

Volcanic island eruption, USGS

Two oceanic plates converge
Islands form an arc when two oceanic plates converge creating a row of islands above the overriding plate. The older plate, which is heavier and denser, is forced beneath the lighter plate. The subducting plate begins to heat up as it descends into the lithosphere .

Formation of island arc
The leading edge of the oceanic plate begins to melt as it is forced deep into the crust and upper mantle. The melting plate feeds magma chambers that supply volcanic islands that form an arc when the molten rock erupts onto the ocean floor of the overriding plate.

Mariana Islands
Deep ocean trenches form between the converging plates. Islands form parallel to the ocean trenches on the overriding plate. The Marianas trench, where the Challenger Deep is located, forms the boundary between two converging oceanic plates. The Mariana Islands are parallel to the trench and formed beside the trench.

More Pacific Ring of Fire Links

Strike Slip Fault Learn more about strike slip faults that are boundaries between crustal plates including the San Andreas Fault.

Subduction Zones Find out why the Pacific Ring of Fire has so many subduction zones. 

Aleutian Trench Learn more about this long trench which parallels the Aleutian Islands.

Tectonic Plate Movement Find out about tectonic plate movement and how it relates to the Theory of Plate Tectonics


Redoubt Volcano Learn more about redoubt volcano located on the Cook Inlet of Alaska.

Island Arcs  Arcs of islands are a string of volcanic islands in the ocean. Find out more about these islands in the Pacific Ocean.

Pacific Ring of Fire Learn more about the Ring of Fire which is home to towering volcanoes and great earthquakes.

Kids Fun Science The links on our home page include information about volcanoes, science activities, plate tectonics, the rock cycle and much more.