GEOG 1350 Lecture Notes - Lecture 4: Volcanic Explosivity Index, Pyroclastic Rock, Volcanic Crater
26 Oct 2016
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Document Summary
2/3 of all volcanoes are found on the ring of fire" surrounding the pacific. Subduction zones and mid-ocean ridges allow molten rock to reach the surface. It is found deep within the crust and upper mantle. It is found flowing from an erupting volcano magma we can see. The most abundant elements in magma are silicon and oxygen; when combined they are referred to as silica. Volcanic rocks are named based on the amount of silica present. Magma also contains small amounts of gases (water vapour and carbon dioxide). Volcanoes have different shapes based on the chemistry and viscosity of their magma. Magma viscosity is determined by silica content and temperature. Hotter, less viscous, fewer gasses - hawaii. Volcanoes with high silica magma produce the most explosive eruptions. As magma approaches the surface, the pressure lowers allowing gases to bubble up and escape: clue for future eruption if we can measure gases escaping.
