GLG 121 Lecture Notes - Lecture 3: Silicate Minerals, Continental Crust, Volcanic Glass
4 Oct 2016
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Volcanic (extrusive): quick cooling at the surface: sedimentary. Magma crystallization igneous rock weathering sediment erosion. Transport deposition sedimentary metamorphic (buried) melting . Weathering/other natural effects can alter circle of cycle. Earth"s crust: 80% igneous rocks, 15% metamorphic rocks, 5% sedimentary rocks, oceanic crust is 3-6 miles thick and continental crust is typically 20-30 miles thick. Magma vs lava: 3 parts to magma (solid, liquid, gas) Gas portion = volatiles, vaporizes at surface. Fast-cooling = fine grained (minerals are too small to see) Most common igneous rock = basalt (fine grained) Slow-cooling = coarse grained (large mineral growth: 2. Almost all igneous rocks are composed of the silicate minerals. Take two rocks with identical felsic compositions, you may get two rocks with different textures. Rhyolite (cools fast) and granite (cools slow: same composition with different appearances. Common igneous rocks: granite, basalt, diorite, gabbro, rhyolite, andesite. Other (unique) igneous rocks: obsidian (volcanic glass, conchoidal fractures like glass, pumice (only rock that floats)
