GEOG 170A1 Study Guide - Final Guide: Continental Crust, Andes, Plate Tectonics
11 Dec 2014
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Document Summary
Earth"s continents were once a large mass called pangaea. we know this via 3 converging lines of evidence: Magnetic fields consistent with early single land mass. Plates were cast into motion by the force of seafloor spreading caused by upwelling molten magma. This is termed divergent spreading where plates are spreading apart from one location. When plates collide at the point of contact (convergence), the higher density plate will dive underneath the lighter" plate. (mariana trench 36,000 feet below sea level) and huge mountain ranges from inland volcanoes. Where subducting crust is being recycled" as magma and erupting (andes. These are hotspots" and can occur inland from actual subduction zones. Earth"s topography is architected" by the hydrologic, rock and tectonic cycles. Tectonic cycles are important in particular for mountain building---which happens when oceanic plates collide with continental plates building mountains through compression and volcanism. Earth"s crust is born of upwelling magma:
