Earth Sciences 2240F/G Lecture 7: Unit 2 Study Guide - Volcanoes - Chapters 7, 8, 9
4 Oct 2015
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Unit 2: study guide: volcanoes: chapters 7, 8, 9. Viscosity: temperature, volatiles (structure of h2o; role, composition (si-o structures, general order of mineral formation. Main compositional types (from more primitive to more evolved: basaltic (basalt volcanic rocks; flows most common, andesitic (intermediate; pyroclastic flows most common, rhyolitic (very viscous flows, pyroclastics and ash) Learn general ranges of sio2, t of eruption, viscosity, water content. 90% associated with plate boundaries; 10% with plumes/hotspots. Spreading centers: partial melt generation (fig. 11, morb, density of asthenosphere peridotite vs. partial melt. Subduction zones: ring of fire , role of water to promote melting, learn basic model (fig. 13, modifications to basaltic melt to yield andesitic/rhyolitic melt. Lava flows, pyroclastic flows and nuee ardente, ash, gas, lahars (armero) Eruption causes (see fig. 1: high silica, high volatiles, viscous magma, cap ruptures. Juan de fuca activity; no volcanism elsewhere (see fig. 4) Mount st. helens 1980: hazard prediction, evidence of magma motion, eruption event.
