Everything about Island Arc totally explained
A
volcanic arc is a chain of
volcanic islands or
mountains formed by
plate tectonics as an oceanic
tectonic plate subducts under another tectonic plate and produces
magma. There are two types of volcanic arcs: oceanic arcs (commonly called
island arcs, a type of
archipelago) and continental arcs. In the former,
oceanic crust subducts beneath other oceanic crust on an adjacent plate, while in the latter case the oceanic crust subducts beneath
continental crust. In some situations, a single subduction zone may show both aspects along its length, as part of a plate subducts beneath a continent and part beneath adjacent oceanic crust.
Two classic examples of oceanic island arcs are the
Mariana Islands in the western
Pacific Ocean and the
Lesser Antilles in the western
Atlantic Ocean. The
Cascade Volcanic Arc in western
North America and the
Andes along the western edge of
South America are examples of continental volcanic arcs. The best examples of volcanic arcs with both sets of characteristics are in the North Pacific, with the Aleutian Arc consisting of the
Aleutian Islands and their extension the
Aleutian Range on the
Alaska Peninsula, and the Kuril-Kamchatka Arc comprising the
Kuril Islands and southern
Kamchatka Peninsula.
Petrology
In the
subduction zone, loss of
volatiles from the subducted slab induces partial melting of the overriding
mantle and generates low-density,
calc-alkaline magma that buoyantly rises to
intrude and be extruded through the
lithosphere of the overriding 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 gravitational pull of the relatively dense subducting plate pulling the leading edge of the plate downward. Multiple
earthquakes occur along this subduction boundary with the
seismic hypocenters located at increasing depth under the island arc: these quakes define the
Wadati-Benioff zones.
Ocean basins that are being reduced by subduction are called 'remnant oceans' as that'll slowly be shrunken out of existence and crushed in the subsequent
orogenic collision. This process has happened over and over in the geologic history of the Earth.
Examples
Continental arcs
Island arcs
Aleutian Islands
Kuril Islands
Japan and Ryukyu Islands
Izu Islands
Philippines
Mariana Islands
Tonga and Kermadec Islands
Bonin Islands
Crete and Dodecanese
Andaman and Nicobar Islands
Mentawai Islands
Sunda Arc
Lesser Sunda Islands
Tanimbar and Kai Islands
Solomon Islands
South Aegean Volcanic Arc
Lesser Antilles, including the Leeward Antilles
South Sandwich Islands
Mascarene Islands
Ancient Island arcs
Insular Islands
Intermontane IslandsFurther Information
Get more info on 'Island Arc'.
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