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A volcanic arc (also known as a magmatic arc [1]: 6.2 ) is a belt of volcanoes formed above a subducting oceanic tectonic plate, [2] with the belt arranged in an arc shape as seen from above. Volcanic arcs typically parallel an oceanic trench , with the arc located further from the subducting plate than the trench.
Andesite and basaltic andesite are the most abundant volcanic rock in island arc which is indicative of the calc-alkaline magmas. Some Island arcs have distributed volcanic series as can be seen in the Japanese island arc system where the volcanic rocks change from tholeiite—calc-alkaline—alkaline with increasing distance from the trench. [15]
[6] [7] At issue are the current estimates of plate configuration and rate of subduction, but based on the chemistry of these volcanoes, they are also subduction related and therefore part of the Cascade Volcanic Arc. [8] [9] The Cascade Volcanic Arc appears to be segmented; the central portion of the arc is the most active and the northern end ...
Back-arc basins form behind a volcanic arc and are associated with extensional tectonics and high heat flow, often being home to seafloor spreading centers. These spreading centers are like mid-ocean ridges, though the magma composition of back-arc basins is generally more varied and contains a higher water content than mid-ocean ridge magmas. [16]
The eastern boundary is a subduction zone, the Lesser Antilles subduction zone, where oceanic crust of the South American plate is being subducted under the Caribbean plate. Subduction forms the volcanic islands of the Lesser Antilles Volcanic Arc from the Virgin Islands in the north to the islands off the coast of Venezuela in the south.
The ancient Nicaraguan arc comprises a Cretaceous-Eocene ancient arc (∼130-50 Ma), an Oligocene-Miocene arc (∼30-5 Ma) and the Recent volcanic front. [5] The ancient arc has a more acidic calc-alkaline composition, wheres the Oligocene-Miocene arc is transitional towards basaltic tholeiiic composition, and the volcanic front is mostly ...
The Aleutian island arc formed ~50-55 ma as a result of Kula Plate subduction under the North American Plate before the Pacific plate arrived. [3] There are three stratigraphic units of the Aleutian island arc: volcanic rocks from ~55-33 ma, marine sedimentary rocks from ~23-33 ma, and sedimentary and igneous rocks from ~5 ma-present. [3]
A continental arc is a type of volcanic arc occurring as an "arc-shape" topographic high region along a continental margin.The continental arc is formed at an active continental margin where two tectonic plates meet, and where one plate has continental crust and the other oceanic crust along the line of plate convergence, and a subduction zone develops.