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Nilanjan Bhowmick AIR 3, CSIR NET (Earth Science)
Srikanta Nayak posted an Question
April 19, 2021 • 22:54 pm
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30 points
30 points
- IIT JAM
- Geology (GG)
How island arc formed..
2 Answer(s)
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Vaibhav singh Best Answer
Island arcs ir Volcanic Islandic arc are nothing but Volcanic mountain chains .They are Oceanic equivalent of Continental Volcanic arcs. Island arcs are formed at ocean-ocean convergence margin where older,denser oceanic plate subducts under the other relatively less denser oceanic plate .Due to flux-induced partial melting ,magma is produced in the zone of melting above the subducting plate. The magma formed being less denser rises above in forms of magma daipirs(blobs) and erupts at the surface of overriding oceanic plate . By passage of long time ,erupting lava forms typical volcanoes (especially shield volacanoes as in Hawaiin Islands).You should note the lava erupted is Basaltic (less viscous) so can form shield volcano chains ....so called island arc chains. You may ask Why arc, not straight line of volcanoes ?? Bcoz rigid plates are floating above plastic static asthenosphere.when One volcano is formed at one locality,it is being moved away after long geologic time,and at the same locality other volcano start to form.
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Vaibhav jain
Island arcs are formed in a subduction setting where an oceanic plate subducts into mantle which on partial melting rises upto the surface in the form of plumes. Island arcs are typical of overriding oceanic plate. Such arcs sometimes form a chain/series of arcs or hotspots. Hawaiin island chain is an example.
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But again sir...how arc shaped volcano formed..
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Vaibhav jain![best-answer]()
When this less buoyant magma hits the surface it punctures the lithosphere and expells hot magma in a radial form like a cone. cross section of which is an arc shape.