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Download Volcanoes and Volcanism (Con`t.)
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Crater Lake Jena Hershkowitz and Ethan Farina-Henry IGNEOUS PROCESSES AND IGNEOUS ROCKS FLUIDITY AND VISCOSITY OF MAGMA Magmas tend to rise. Less dense than solid rock. Liquid rock has more volume than solid. Rise is controlled by FLUIDITY of the magma. FLUIDITY is a fluid’s ability to flow. Governed by temperature and composition. Greater heat greater fluidity of magma. Lower silica content greater fluidity of magma. IGNEOUS PROCESSES AND IGNEOUS ROCKS FLUIDITY AND VISCOSITY OF MAGMA Movement of magma also related to VISCOSITY. VISCOSITY is fluid’s resistance to flow. Opposite of fluidity. Greater viscosity of magma, the lower the ability to flow. Cool magmas flow sluggishly, while hot magmas flow easily. Viscosity also increases with silica content. IGNEOUS PROCESSES AND IGNEOUS ROCKS FLUIDITY AND VISCOSITY OF MAGMA Magma composition reflects silica content. Felsic magmas have higher silica content so felsic magmas have greater viscosity. Felsic magmas also form at lower temperatures so felsic magmas again are less likely to flow. Felsic magmas and lavas consequently are much more explosive than mafic magmas and lavas. IGNEOUS PROCESSES AND IGNEOUS ROCKS FLUIDITY AND VISCOSITY OF MAGMA Mafic magmas have low silica content so mafic magmas have lower viscosity. Mafic magmas also from at higher temperatures so mafic magmas will flow easily. Mafic magmas have greater ability to rise to the surface. Mafic magmas and lavas generally produce very quiet eruptions. IGNEOUS PROCESSES AND IGNEOUS ROCKS CRYSTALLIZATION OF MAGMA All magmas eventually cool and crystallize. Melting temperature and freezing temperature is the same for each individual mineral. Just the direction of the reaction changes. Minerals that melt first when a rock is heated, also tend to crystallize last when a magma is cooled. Partially cooled magma will contain solid mineral crystals that crystallize at high temperature. It will also contain ions that may crystallize later. IGNEOUS PROCESSES AND IGNEOUS ROCKS Bowen’s Reaction Series CRYSTALLIZATION OF MAGMA IGNEOUS PROCESSES AND IGNEOUS ROCKS CRYSTALLIZATION OF MAGMA OTHER POSSIBILITIES FRACTIONAL CRYSTALLIZATION Earlier forming crystals are denser than magma. Sink to the bottom of magma chamber. Changes composition of magma. IGNEOUS PROCESSES AND IGNEOUS ROCKS CRYSTALLIZATION OF MAGMA Palisades Sill, NJ IGNEOUS PROCESSES AND IGNEOUS ROCKS CRYSTALLIZATION OF MAGMA Bushveld Complex, S. Africa
