Geology 101 Lab 1 Monday September 1 2014 Continental Drift Continental drift was a precursor to Plate Tectonic Theory It was proposed by Alfred Wegener in 1915 He noted the jigsaw puzzle fit of the coastlines on opposite sides of the Atlantic He proposed Pangea existed a super continent He was criticized for it His theory was never accepted in his lifetime Seafloor Spreading Early 1960s Harry Hess suggested that new oceanic crust are created in oceanic ridges such as the Mid Atlantic Ridge As the process goes on the seafloor the floor is carried apart like a conveyor belt He also suggested crust descends in the vicinity of deep ocean trenches Seafloor spreading combined with a greater understanding of remnant magnetism preserved in oceanic rocks developed into the unifying theory called Plate Tectonics Earth s Layered Structure Crust mantle core all have a distinct chemical composition Crust o 5 70 km top layer Mantle Core o 2900 km o 3480 km o 100 km fluid like behavior The lithosphere is the rigid outer shell of earth The temperature pressure regime in the upper asthenosphere result in a Plate Tectonics 7 major plates All their major interactions occur at their boundaries Plate Boundaries Divergent o 2 plates move apart o ex Mid Atlantic ridge Convergent o Plates moving together o Several types of convergent margins o Can cause volcanic eruptions o Two continents can collide Ex Himalaya Mountains Transform o Plates slide horizontally past one another
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