Blue Planet Notes for Exam 2

Blue Planet Notes for Exam 2 - Igneous Rocks Slow Cooling...

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Igneous Rocks : Slow Cooling: intrusive within crust, Coarse Grained Fast Cooling: (aka volcanic) extrusive from the crust, fine grained Igneous Rocks: slowly cooled from magma Magma : liquid rock, contains gases and mineral grains Types of Magma based on Silica content o 1) Basaltic : about 50% silica with little dissolved gasses Volcanic Basalt Intrusive Gabbro Makes up oceanic lithosphere (found in mid-ocean ridges) Low Viscosity (flows easily) Eruptions less explosive Very common volcanic rock o 2) Andesitic : about 60% silica with lots of dissolved gasses Volcanic Andesite Intrusive Diorite Higher Viscosity Eruptions are more explosive Forms Island Arc Volcanoes o 3) Rhyolitic : about 70% or more silica with lots of dissolved gasses Volcanic Rhyolite (Ex: Pumice, the floating rock) Intrusive Granite Highest viscosity Very explosive eruptions, so a lot of carbon dioxide is released. New Mexico Rocks o Sandias Granite o West Mesa Basalt o Jemez Rhyolite o Mt. Taylor Andesite and Basalts Volcanic Hazards: Dependant on magma types o Gas-rich magmas : the magma is under a lot of pressure when it is under the surface. The pressure drops as the magma moves up, and then the gas comes out of the magma. At the same time, the magma starts to cool so your get glass and Rhyolite shards. The gas adds energy. This is called a Pyroclastic Flow. Pyroclastic Flows : too dense to rise in the eruption column, so it falls back and moves down the flank of volcano. It is hot, mobile, very fast, and flows tephra and gas. Can travel up to 100 km away at speeds of 700 km/hr Mt. St. Helen’s in 1980 Lateral blast and column eruption Volcanoes Plate Tectonic Settings Rhyolitic Volcanoes: always found in the continental crust, never oceanic.
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Andesitic Volcanoes: Found in both oceanic and continental crust o Arc volcanism subduction zones Basaltic Volcanoes: Found at ocean ridges and hot spots, mostly oceanic but some continental. o Unique because of melting in the mantle, requires a thin crust. Sedimentary Rocks : The most common at the surface of the Earth. Formed by accumulation/consolidation of loose rock/mineral material Pre-existing rocks weathered and eroded then transported and deposited, then buried and lithified o Weathering : two types 1) Physical : breaking the rock into pieces Freeze-Thaw: water ice has a 9% expansion o So, water gets in the rocks, and then it freezes, expands, and breaks the rocks. Forest Fires Salt Wedging 2) Chemical : Changes the chemical composition of the rock by chemical reactions Chemically change existing minerals to new stable minerals. Agent of Weathering: water + carbon dioxide = carbonic
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This note was uploaded on 04/02/2008 for the course ENVS 101 taught by Professor Peterj.fawcett during the Spring '08 term at New Mexico.

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Blue Planet Notes for Exam 2 - Igneous Rocks Slow Cooling...

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