Island Arcs

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Island Arcs


relief structures of contemporary geosynclinal systems occurring in the transitional zones between continents and oceans. Island arcs are linear mountains that divide the basins of the marginal seas from the deep-sea trenches. The foundations of island arcs are underwater mountain ranges from 40–50 to 200–400 km wide and up to 1,000 or more km long, composed primarily of volcanic strata of basalt, a mixture of andesite and basalt, or andesite. The top of the range rises above sea level in the form of islands. Island arcs frequently consist of two parallel ridges, one of which, usually the outer ridge facing the deep-sea trench, is an underwater mountain range. In such cases the ridges are separated from one another by a longitudinal depression up to 3–4.5 km deep filled with a stratum of sediment 2–3 km deep. Transverse depressions are found in fracture zones and usually form the deeper straits.

Most island arcs are located on the northern and western margins of the Pacific Ocean; the only exceptions are the Antilles, the Lesser Antilles, and the Sunda arcs. In their early stages of development island arcs are a thickening of the ocean crust with volcanic structures on the crest, for example, the Mariana and Kermadec island arcs. In later stages island arcs form large islands and peninsulas, for example, the Japanese Islands, the Kamchatka Peninsula, and New Guinea; here the structure of the crust is similar to that of continents. Island arcs have highly differentiated gravitational and magnetic fields, increased heat flows, and active volcanic and seismic activity. Between island arcs and the deep-water trenches lies the region of earthquake concentration, the Benioff zone, which passes under the island arcs.


Ostrovnye dugi: Sb. st. Moscow, 1952. (Translated from English.)
Gorshkov, G. S. Vulkanizm Kuril’skoi ostrovnoi dugi. Moscow, 1967.
Pushcharovskii, Iu. M. Vvedenie ν tektoniku Tikhookeanskogo segmenta Zemli. Moscow, 1972.
Udintsev, G. B. Geomorfologiia i tektonika dna Tikhogo okeana. Moscow, 1972.
Mitchell, A. H., and H. G. Reading. “Evolution of Island Arcs.” Journal of Geology, 1971, vol. 79, no. 3.


References in periodicals archive ?
Miller, one of Jordan's colleagues at USC, reported in Geophysical Research Letters detecting boundaries in the keels that suggest that island arcs smashed into cratons, piling up against them over time.
Pinet and Tremblay (1995) proposed that emplacement of the Quebec ophiolites was caused by the collision of an island arc with the North American continent during the Ordovician.
1973 'Distribution and Petrology of Late Cenozoic Volcanoes in Papua New Guinea'The Western Pacific: Island arcs, marginal seas, geochemistry, P.
Gabbro is also found in "ophiolite" complexes, bits of fossil ocean crust and mantle commonly found on land in tectonic plate collision zones and in island arcs (see map on page 24).
Global Relief" is a physical map of the Earth with land surfaces and ocean floors color coded to emphasize major deserts, mountain ranges, island arcs, and ocean trenches.
25) ratios are consistent with calc-alkaline rocks of continental margin-type island arcs.
10d, after Condie 1989) where primitive island arcs have lower ratios than continental (Andean) arcs.
Recent advances in the study of orogenic belts include discovery of many exotic geologic bodies such as fragments of oceanic plateaus or island arcs that have traveled great distances to their present position.
In island arcs not mapped in great detail (the great majority), exploration strategies will be brightened by the realization of the intense dynamism of arc systems and of the dominant role of strike-slip faults in this dynamism.
Hoffman proposes that mantle convection swept the microcontinents and island arcs toward an area where cold mantle material was sinking.