Geography 2152F/G Lecture Notes - Lecture 8: Volcanism, Sulfur Dioxide, Tephra
21 Apr 2016
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Document Summary
Nearly 2/3 of all volcanoes are found on the ring of fire surrounding pacific ocean. Subduction zones and mid-ocean ridges allow molten rock to reach the surface. Found deep within the crust and upper mantle. Lava is magma on the earth"s surface. The most abundant elements in magma are oxygen and silicon; when the two combine, they are called silica. Volcanic rocks are named based on amount of silica present. Types of volcanic rocks: basalt, andesite, dacite, rhyolite. 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 (bubbling hints at eruption) Hawaiian volcanic magma has low silica content. Rhyolitic and dacitic magmas produce explosive eruptions while basaltic and andesitic magmas produce eruptions that tend to flow rather than explode. Volcanoes are sorted into 4 different types and are classified based on shape, appearance, style of eruptions: shield, composite, volcanic dome, cinder cone: shield volcanoes.
