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GLG 201 3.30.07 - Texture Rocks that cool BELOW the surface...

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GLG 201 3.30.07 Igneous Rocks: Last Depositional Environment On continents, where does most volcanic material come from? Material comes from pockets of molten material beneath the Earth’s surface. Igneous Environments Higher SiO2: Higher resistance to flow Felsic volcanoes DON’T have many flows that move easily Also tend to be gassy Massive Eruptions Ash Tuff Rhyolite Mafic Volcanoes DO have flows Basalt Volcanic material cools on Earth’s surface Some igneous rocks cool BELOW surface
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Unformatted text preview: Texture Rocks that cool BELOW the surface are coarse-grained Where does magma come from? Pockets under the earth’s surface NOT in the core NOT a layer beneath Earth’s surface Magma forms in pools just beneath the surface Change in melting point (water) Temperature variations trigger melting Why does magma rise? Melted rock is lighter than the surrounding material Why are there intrusive rocks of different compositions? Most of the Earth is mafic...
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