Question

How does a subduction volcano form?

Answer 1

Hint:Volcanic activity is a sudden movement of the earth’s crust caused by the convergence or divergence of the tectonic plates. It can occur both on the land due to the convergence of tectonic plates like the Pacific Ring of Fire and in the oceans due to the divergence of tectonic plates like the Mid-Atlantic Ridge. A volcano develops when hot lava, volcanic ash and gases like steam, carbon dioxide and sulphur compounds erupt from the earth’s surface after escaping the magma chamber through faults and cracks.

Complete answer:Subduction volcanic zone is formed when an ocean plate converges beneath a continental plate, creating a large linear depression called an oceanic trench. As the subducted slab descends deeper, it progressively encounters higher temperatures and higher pressures which result in the slab releasing water into the mantle wedge that lies over the descending plate. Water causes the lowering of the temperature of the mental wedge which makes it melt. The resultant eruption contains basalt, andesite, dacite, rhyolite and andesite. The major volcanoes are Mt. St. Helena, Mt.Fuji and Mt.Etna, all of which lies hundreds of kilometres away from the trench in volcanic arcs. Volcanic arc could be both island and continental in nature. Island arcs include the Mariana and the Tonga island arcs and continental arc includes the Cascade volcanic arc. The Aleutian Trench has both island and continental arcs.

Note: There are about 1500 potentially active volcanoes on earth other than the continuous belt of volcanoes on the ocean floor. Out of these, 500 have already erupted at least once in history. Hawaii’s Mauna Loa is the largest active volcano on earth.