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Transcript
11/12/15 Pieces of lithosphere that move around on top of asthenosphere Act like pieces of a jigsaw puzzle that fit together to form lithosphere Not all tectonic plates are the same Differences in size and shape North American plate versus Cocos plate Parts of crust they contain: Cocos and Nazca plates: only oceanic crust North plate: continental and oceanic crust Continental drift: theory that continents can drift apart Proposed by Alfred Wegener Originally rejected because of lack of evidence Fossil findings Mesosaurus (reptile) Glossopteris (plant) Found on four different continents Glacier activity Grooves created over time match up when continents once fit together Pangaea: “all earth” Began over 225-245 million years ago Panthalassa: “all sea” Both Greek terms Laurasia Gondwana 65 million years ago Further breakup Process by which new oceanic lithosphere is created Occurs at mid-ocean ridges Mid-Atlantic Ridge Underwater mountain chains that run through Earth’s ocean basins Sea floor spreads as tectonic plates spread apart Magma rises to fill gap newly created gap Newest crust is found along ocean ridges Oldest found near edges of continents New lithosphere Process in which Earth’s magnetic poles change place Provides evidence of sea-floor spreading Molten rock contains tiny grains of magnetic minerals (act like compasses) Once molten rock cools minerals are “set in stone” Magnetic fields reverse each time a new band starts