5 volcanoes

5 volcanoes - Volcanism and Volcanic Hazards Magma...

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Unformatted text preview: Volcanism and Volcanic Hazards Magma Formation Remember: The mantle is solid! Three ways to form magma: 1.Decompression 2.Add Volatiles H 2 0 & CO 2 3.Heat Transfer PRESSURE Magma Composition All magma contains Silicon (Si) and Oxygen (O) with varying amounts of Al, Ca, Na, K, Fe and Mg- The amount of silica (SiO 2 ) distinguishes the magma Felsic High silica (>65%) Intermediate moderate silica (50-60%) Mafic Low silica (40-50%) Ultra-mafic Very low silica (30-40%) Magma Composition What kind will we have? Main factor: Source rock composition Secondary: Partial Melting Assimilation Magma Mixing Magma Movement Volcanoes are surface expressions of subsurface igneous activity www.geo.ua.edu Defined by eruptive history: Active : Historical eruption Dormant : Capable of eruption Extinct : No activity Presently - 550 active volcanoes globally Eruption Types Explosive vs. Nonexplosive Factors that control eruptive style of a volcano: 1. Composition 2. Temperature 3. Volatiles www.geo.ua.edu Eruption Types These factors affect the magmas viscosity- Viscosity: materials resistance to flow Temperature hot magma is less viscous Composition Silica content...
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This note was uploaded on 04/19/2011 for the course EES 2001 taught by Professor Thornburg during the Spring '11 term at Temple.

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5 volcanoes - Volcanism and Volcanic Hazards Magma...

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