Earth Sciences 1022A/B Lecture 3: Igneous Rocks
28 Sep 2015
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Document Summary
Earth sciences 1022a lecture 3 igneous rocks. Magma cooled so quickly that the crystals are very small and hard to see: phaneritic texture: slow cooling magma, large crystals. Form under the ground by slow cooling over millions of years: porphyritic texture: large crystals surrounded by smaller ones. Might form at the neck of a volcano or the magma chamber. The eruption occurs and the magma hits the surface and cools quickly: glassy texture: quenched, no crystals. Lava is cooled so quickly it erupts under a glacier or cold water. Lava is quenched (crystals have no chance to form at all: pyroclastic texture: airborne pieces of magma fell to the ground. Cools in the air and rains down on the slopes of the volcano and produces a particular looking type of volcanic rock. Naming igneous rocks: felsic (~70% silica, really light colored, granite: in cores of mountains.
