EARTHSC 1G03 Chapter Notes - Chapter 2: Seafloor Spreading, Continental Drift, Paleomagnetism
5 Apr 2017
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Alfred wegener proposed that continents had once been joined together to form a one large supercontinent called pangea. Also said that it had drifted apart. This idea is called the continental-drift hypothesis. Wegener drew from several different sources of data to support his hypothesis: The distribution of late paleozoic climatic belts. Correlation of distinctive rock assemblages that are now on opposite sides of the ocean. Rocks retain a record of the earth"s magnetic field that existed at the time the rocks were formed. By measuring paleomagnetism in succesivly older rocks, geologists discovered apparent polar-wander paths. The contrasts among apparent polar-wander paths for different continents serve as proof of continental drift. Around 1960, harry hess, proposed the hypothesis of seafloor spreading. According to this hypothesis, new seafloor forms at mid-ocean ridges, then spreads symmetrically away from the ridge axis. Eventually the ocean floor sinks down back into the mantle at deep-ocean trenches.
