EPS C20 Lecture 6: Discovering plate tectonics
17 Nov 2020
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World wide standardized seismic network 100+ stations. First time anyone tried to build a global network to see seismic sources anywhere in the world. To detect nuclear tests/explosions on fairly regular basis. Byerly vault -- above the berkeley campus. One of the original wwssn network sites. Berkeley was one of the highest quality sites because it was so deep. Why do earthquakes occur in these specific regions? underground. Rigid plates moving across the surface of earth. All the deformation occurs at the boundaries. 1620: francis bacon africa & south america fit together. Mid 1800"s: first proposed that continents did fit together. 1912: alfred wegener -- proposed continental drift . Conclusion: there used to be a supercontinent -- pangea. Wegener"s ideas were only discussed for a decade & then dropped. Land masses sank as the earth cooled & contracted. Land bridges between the continents could explain the fossil record. Periodic reversals of the earth"s magnetic field as recorded as stripes.
