GEOG 170A1 Lecture 15: GEOG 170- Earth’s Environment: Introduction to Physical Geography - Lecture 15: Physical Parts of Earth Day 2
14 Nov 2014
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Geog 170- earth"s environment: introduction to physical geography - lecture 15: Earth"s continents were once a large mass called pangaea. we know this via 3 converging lines of evidence: A) all continents share same fossil species; B) magnetic alignment of rock is consistent with a single initial location; C) continents fit together like a jigsaw puzzle. 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. Subduction is convergent spreading collision zones of compression/mountain building and crustal destruction. Deep ocean trenches (mariana trench 36,000 feet below sea level) Huge mountain ranges from inland volcanoes, where subducting crust is being recycled" as magma and erupting (andes mountains; cascade. These are hotspots" and can occur inland from actual subduction zones.
