Geology 101 Introduction to Earth Chapter 4-5 Igneous Rocks and Volcanoes
Geology 101 Introduction to Earth Chapter 4-5 Igneous Rocks and Volcanoes GEOL 101 001
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This 2 page Class Notes was uploaded by Kendrick Notetaker on Sunday October 2, 2016. The Class Notes belongs to GEOL 101 001 at University of South Carolina taught by Scott White in Fall 2016. Since its upload, it has received 59 views. For similar materials see Introduction to the Earth in Science at University of South Carolina.
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Date Created: 10/02/16
Geology 101 (Mr. White) Ch 4 - 5 Highlight = Important Principle Highlight = Important Concept Highlight = Key Term [Chapter 4 - 5] [Igneous Rocks and Volcanoes] [Classifying Igneous Rocks] - Texture - Is it possible to see individual minerals? - Are there bubbles on it? Extrusive pyroclasts: Form in violent eruptions from lava thrown high in the air. Ex: Pumice, bomb, volcanic ash. Extrusive Igneous Rocks: Cool rapidly on Earth’s Surface and are fine-grained. Ex: Basalt and Rhyolite. Intrusive Igneous Rocks: Cool slowly in Earth’s interior, allowing large, coarse crystals to form. Porphyritic: Are crystals that start to grown beneath Earth’s surface. As some crystals grow large, but the remaining melt cools faster, forming smaller crystals, due to either erupting to the surface or due to it being intruded close to earth’s surface. - Composition - Dark colored, light gray, pink, blue etc. - What Minerals? Felsic Intermediate Mafic Ultramafic Granite Granodiorite Diorite Gabbro Peridotite Rhyolite Dacite Andesite Basalt Composition Intrusive Rock Types Extrusive Rock Types Origin of Magma - Decompression Melting - Increases in confining pressure cause an increase in the rock’s melting temperature. - When confining pressure drops, decompression melting occurs. Ex: When a volume of rock rises toward the crust from deeper within mantle. - Hydrous Melting - Volaties ( primarily water) cause rocks to melt at lower temperatures - Important factor where oceanic lithosphere descends into the mantle - Water squeezed out of descending crust Evolution of Magma - All Magma stars from melting of the mantle - Bowen’s Reaction Series - Minerals crystallize in a systematic order based on their melting points - As minerals form, the composition of the remaining liquid portion of the magma continually changes 1. As magma temperature decreases 2. Materials crystallize in an ordered series 3. While plagioclase feldspar crystallizes, from calcium-rich sodium rich form 4. The composition of magma changes from ultramafic to andesitic - Volcanoes: Three Common Types - Shield Volcanoes: Are the largest and are made of basalt Are formed from not just lava flows, but from large volumes of pyroclastic materials Pyroclastic materials: are hot chucks which are formed when molten lava pieces are physically thrown out of a volcano. - Cinder Cones: are the smallest and may be either basalt or andesite. Are small and normally formed by only a single eruption which produces usually only one rock type - Stratovolcanoes(composite volcanoes): are intermediate in size and made primarily of andesite Are large and have long and complex eruptive histories and may be composed of a variety of rock types. Divergent Boundaries and Hotspots: Areas of Intense Basaltic Volcanism - Active volcanism along divergent boundaries is and mantle plumes is similar because both are place of intense volcanism that produces almost nothing but basalt. - Fissure Eruptions: Form when melt is extruded from an elongate crack in the ground. - Ex: Fissure eruption in 1983 on Kilaue Volano’s East Rift Zone in Hawaii. - You’re welcome. - Shield Volcanoes: are commonly formed by intense basaltic volcanism in mantle plume of divergent plate boundary settings.
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