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Island arcs are long chains of active volcanoes with intense seismic activity found along convergent tectonic plate boundaries. Most island arcs originate on oceanic crust and have resulted from the descent of the lithosphere into the mantle along the subduction zone.
The slow folding and pleating of the sediments as they rose up from the depths is believed to have initially formed a series of long east–west volcanic island arcs. Volcanic rocks produced in these island arcs are found among the ophiolites of the Penninic nappes.
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.
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]
They are found on the oceanward side of island arcs and Andean-type orogens. [3] Globally, there are over 50 major ocean trenches covering an area of 1.9 million km 2 or about 0.5% of the oceans. [ 4 ]
The Ryukyu Arc is an island arc which extends from the south of Kyushu along the Ryukyu Islands to the northeast of Taiwan, spanning about 1,200 kilometres (750 mi). [2] [3] [4] It is located along a section of the convergent plate boundary where the Philippine Sea Plate is subducting northwestward beneath the Eurasian Plate along the Ryukyu ...
Between 625 and 550 Ma, a subduction zone initiated in the Paleoasian Ocean between Baltica and Gondwana. The subduction produced a string of volcanic island arcs off the coast of Gondwana, including the Carolina Terrane, Avalonia microcontinent, and Gander Terrane. [7] It is unclear whether the arc formed on oceanic or continental crust. [5]
The island arc rocks became exposed above the water line and began to erode as an east-west strike-slip fault emerged. From the Miocene to recent times, oblique strike-slip faults formed along the sutures between old island arcs as the island compressed against North America and oceanic plateau terranes. Nine large fault bounded mountain ranges ...