Geography 2152F/G Lecture Notes - Lecture 8: Sulfur Dioxide, Smog, Return Period
31 May 2016
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Document Summary
Nearly 2/3 of all volcanoes found on ring of fire surrounding pacific ocean. Subduction zones and mid-ocean ridges allow molten rock to reach the surface. Magma found deep within the crust and upper mantle. Lava it is found flowing from an erupting volcano basically magma is lava on the earth"s surface. The most abundant elements in magma are silicon and oxygen; when combined referred to as silica. Volcanic rocks are named based on the amount of silica present. Basalt, andesite, dacite, rhyolite (ordered from lowest to highest silica) Magma with high silica content: cooler, more viscous, more gases. Magma with low silica content: hotter, less viscous, fewer gases. 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. Rhyolitic and dacitic magmas therefore produce the most explosive eruptions. Basaltic and andesitic magmas produce eruptions that tend to flow rather than explode.
