ERTH 20 Lecture Notes - Lecture 3: Plate Tectonics, Oceanic Basin, Curie Temperature
7 May 2020
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Document Summary
Earth"s magnetic field is recorded by magnetic minerals in rocks. When molten rocks cool below a specific temperature (curie point) some minerals permanently record the earth"s magnetic field: magnetic minerals will point towards the pole just like a compass. Inclination: angle of magnetic minerals from the horizontal will depend upon latitude. Sonar was used to map the ocean bathymetry (depth: the deepest parts of the ocean occur near land, a mountain range (ridge) runs through every ocean basin with submarine volcanoes. At mid ocean ridges, two plates are moving apart and new ocean crust is constantly formed. New crust records magnetic field as it cools and so over time records patterns of magnetic reversals. Theory that earth"s lithosphere is broken into a dozen or so rigid plates that move relative to the ocean rifts. Earth"s lithosphere is broken into a dozen or so rigid plates that move relative to one another on the hotter, more plastic asthenosphere.
