<Tr> <Td> </Td> <Td> This article does not cite any sources . Please help improve this article by adding citations to reliable sources . Unsourced material may be challenged and removed . (October 2009) (Learn how and when to remove this template message) </Td> </Tr> <P> An island arc is a type of archipelago, often composed of a chain of volcanoes, with arc - shaped alignment, situated parallel and close to a boundary between two converging tectonic plates . </P> <P> Most of these island arcs are formed as one oceanic tectonic plate subducts another one and, in most cases, produces magma at depths below the over-riding plate . However, this is only true for those island arcs that are part of the group of mountain belts which are called volcanic arcs, a term which is used when all the elements of the arc - shaped mountain belt are composed of volcanoes . For example, large parts of the Andes - Central American - Canadian mountain chain may be known as a volcanic arc, but they are not islands (being situated upon and along a continental area) and are thus not classified as an island arc . On the other hand, the Aegean or Hellenic arc in the Mediterranean area, composed of numerous islands such as Crete, is an island arc, but is not volcanic . Parallel to it is the South Aegean Volcanic Arc, which is the volcanic island arc of the same tectonic system . </P> <P> There is some debate about the usefulness of the distinction between island arcs and volcanic arcs . The term "volcanic island arc" is merely a sub-classification of "island arc ." Island arcs are tectonically created arc - shaped mountain belts that are partly below sea level . Essentially, they represent a specific geographic - topographic situation in which a mountain belt is partly submerged in ocean . Many of these are composed of volcanoes, and can thus be further classified as volcanic island arcs . </P>

Island arcs like the islands of japan formed when two