GEOG306 Lecture Notes - Lecture 7: Volcanic Explosivity Index, Plinian Eruption, Continental Crust
17 Jan 2018
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Document Summary
3 types of volcanoes: plate split: under the ocean, hotspot volcanoes, subduction volcanoes, oceanic plates are heavy, and once deep enough melt the crust above them. Chemical composition of earth"s crust: oceanic crust subducted under continental crust, silica content is the most predominant chemical composition. Yellowstone super volcano: last eruption 640,000 years, ejected 1000km^3 of rock, dust, ash [mt. St. helens -- ~2. 8km^3: since 2004-2009: it has uplifted 20cm. Indication that the granitic magma underground are active. No evidence that another such cataclysmic eruption will occur at yellowstone i the foreseeable future. Recurrence intervals of these events are neither regular nor predictable: plinian eruption can cause nuclear winter, its huge, spews a lot of volcano material. Predictable locations for volcanoes: plate boundaries, ring of fire , hotspot volcanoes, a lot of the same places as earthquakes. Measuring/accessing hazard: volcanic explosivity index f (total volume ejected, height of eruption cloud, duration of eruptive phase, qualitative description)
