EARTHSC 2GG3 Lecture 4: Natural Disasters - Lecture 4 - Volcanoes
16 Jun 2016
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Document Summary
Most active volcanoes are located near plate boundaries. Mid-ocean ridges and subduction zones are sites where molten rock reaches the surface: magma is molten rock, lava is magma on the earth"s surface. 2/3 of all active volcanoes on land are located along the ring of fire which surrounds the pacific ocean. Lava: magma that reaches the earth"s surface. Pyroclastic debris: lava and rock fragments ejected in a volcanic eruption: these are the types of pyroclastic debris. Volcanic bomb: large, semi molted rocks, can be size of small bulls. Lapilli: small as a dime, molted material. Ancient volcanic ash layers: different parts of the ashes slowly going down. Volcano: hill or mountain produced by volcanism. Vent: opening through which eruption takes place. Most magmas come from the asthenosphere: weak, but not liquid, layer of rock. Three main ways in which silicate rocks can melt: decompression. Pressure exerted on hot rock is reduced.
