ERTH 2415 Lecture 9: ERTH 2415 - CLASS 9
5 Oct 2016
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Document Summary
Erth 2415 class 9: plate tectonics and volcanoes. Volcanic eruptions are caused by earth"s internal energy. Composition of the crust as a result of planetary differentiation, 8 elements form 98% of the crust (silicon and oxygen account for ~ 75%) Si-o tetrahedron molecule: four oxygen ions surrounding a much smaller silicon ion. Tetrahedrons combine to form rings, chains, sheets and 3d structures. Magma: partially molten rock below the earth"s surface. Magma that reaches the earth"s surface is called lava. Crystallization: process of mineral formation by solid-liquid separation in a cooling magma. Igneous rocks: form by cooling and solidification from hot molten rock material. Intrusive igneous rocks cooling at depth - slow cooling with large crystals. Most magmas solidify at depth and are later exposed by erosion. Extrusive (volcanis) igneous rocks cooling at the surface fast cooling with small crystals when it makes contact with the atmosphere. Cooling environment intrusive versus extrusive rocks.
