GEOL 101 Study Guide - Midterm Guide: Stratovolcano, Rhyolite, Andesite
23 Dec 2015
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Chapter 5 (cid:1) (cid:1) (cid:1) (cid:1) mtns: example: pompeii the planet"s surface, 3 forms: Volcanoes = unpredictable and dangerous; can build or tear down. Volcanic eruptions transfer materials from the inside of the earth to. Character of lava reflects its viscosity (resistance to flow) Differences in viscosity depend on chemical composition, temperature, gas content, crystal content, and silica content. Columnar jointing: occurs during the final stages of cooling, polygonal column fracture: lava cools faster in water (pillow) Volcaniclastic deposits: volcanoes can erupt large quantities of fragmental igneous material. Blocks refrigerator sized, broken up during eruptions. Pyroclastic debris pyroclastic flow, very hot: tephra, tuff, ignimbrite. Volcanic debris flow moves downslope like wet concrete: lahar ashy mud. Gas bubbles rise faster than magma moves. Vesicles last bubbles to form freeze into lava and this is holes. Gas has trouble escaping because bubbles can"t push through the sticky lava. Explosive pressures build inside beneath the volcano (cid:1)
