EAS201 Lecture Notes - Lecture 4: Crystallization, Andesite, Gabbro
20 Sep 2016
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Magma molten rock + suspended crystals + gases. Volcano vent from which magma, solid rock debris + gases erupt. We organize magma according to their silica content. There is a range of compositions, sio2, always predominant. 3 or (4) common types (basaltic, andesitic, rhyolitic) Viscosity varies with temperature, sio2 content, gas content (0. 2-3%, mainly h2o + co2) The higher the temperature, the lower the viscosity. The less silica there is, the more fluid the magma is. The more silica there is, the more bonds there are, which makes the magma more viscous. Formation of magma due to heating, and/or pressure decrease and/or water uptake. To melt a rock: pressure, temperature and fluid content are the three parameters needed (however can melt when using only one also) * the asthenosphere probably has ~5% partial melt, rising locally to 30% below the mid ocean ridges a lot of water in igneous rock solid liquid solid liquid again.
