GEOL 101 Chapter Notes - Chapter 2: Mid-Ocean Ridge, Seafloor Spreading, Continental Drift
Document Summary
9:27 am: alfred wegener proposed that continents had once been joined together to form a single huge supercontinent (pangaea) and had subsequently drifted apart. According to this hypothesis, new seafloor forms at mid-ocean ridges, then spreads symmetrically away from the ridge axis. Eventually, the ocean floor sinks back into the mantle at deep-ocean trenches: geologists documented that the earth"s magnetic field reverses polarity every now and then. Transform: divergent boundaries are marked by mid-ocean ridges. At divergent boundaries, seafloor spreading produces new oceanic lithosphere: convergent boundaries are marked by deep-ocean trenches and volcanic arcs. As a plate moves over the hot spot, the volcano moves off and dies, and a new volcano forms over the hot spot. Hot spots may be caused by mantle plumes: during rifting, continental lithosphere stretches and thins. If it finally breaks apart, a new mid-ocean ridge forms and seafloor.
