ASTR 6 Lecture Notes - Lecture 13: Oceanic Crust, San Andreas Fault, Subduction
24 Feb 2017
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The lithosphere is broken up into segments called plates. The plates can move around because the mantle is in motion. Plates are moving relative to plates around them. Alfred wegener- published a theory of continental drift. He claimed that the continents had once been part of a supercontinent that he named pangaea. By 1960s there was so much evidence that proved wegener right. Pangaea started to break up into the two continents laurasia (northern hemisphere) and gondwanaland (southern hemisphere) Eurasia starts to break up as well as south america and africa. Gondwanaland splits into africa, south america, australia, antartica and india. Crustal material is split apart or rifted, and crust on each side of boundary is moving away from the boundary. These plates are found above where hot material is rising up through the asthenosphere. The overlying lithosphere is thin and fractured. https://www. evernote. com/home. action#n=b02a17b4-3465-44ac-82d8-476645e0ec8e&ses=4&sh=2&sds=2& There is volcanic activity, earthquakes at the boundaries. Most of the plates on earth are divergent.
