Plate Tectonics Mrs. Mia Conlon Marine Science History • Alfred Wegener hypothesized all the lands were a single protocontinent called Pangaea • Pangaea means “all lands” or “all Earth” • Continental shelves provide the best fit • Couldn’t provide an excepted mechanism to support until after death in the 1960’s Continental Drift • The theory that the continents move or “drift” relative to each other • Wegener was the first to use the term even though the theory had been around since the 19th century • Supported by geologic and fossil evidence • Has been encompassed into plate tectonics Plate Tectonics • DEFINITION - scientific theory that describes the large-scale motion of Earth's lithosphere • The rigid lithosphere has plates (oceanic & continental crust) that move above the fluid asthenosphere. • The movement is caused by convection currents within the asthenosphere. Material rises as it is heated and falls as it cools creating a circular pattern and motion. Supported by Geologic evidence – matching striations at continental edges Fossil evidence – matching species along continental edge areas Paleomagnetism – magnetite and particle orientation Sea Floor Spreading - Theory of new crust being created at ridge, pushed away, and returning underneath plate at trenches. Proposed by Hess in 1960’s • Heat flow • • • • Divergent Boundary Terms for Divergent Boundary • Lithosphere - the crust plus the rigid, upper mantle. • Lower Mantle (semi-rigid) - the deepest parts of the mantle, just above the core. • Magma - molten rock withing the Earth's mantle. In seafloor spreading, magma moves from the asthenosphere to the crust. • Ocean - large bodies of water sitting atop oceanic crust. • Oceanic Crust - thin parts of the Earth's crust located under the oceans. • Oceanic Ridge - newly-formed region of the oceanic crust. • Upper Mantle (rigid) - the uppermost part of the mantle, part of the lithosphere. • Asthenosphere = Upper Mantle (flowing) - the lower part of the upper mantle that exhibits plastic (flowing) properties. It is located below the lithosphere (the crust and upper mantle). Divergent Boundary characteristics • Plates move apart • Creates new sea floor • Mid-ocean ridges Convergent Boundary Terms for Convergent Boundary • Asthenosphere = Upper Mantle (flowing) - the lower part of the upper mantle that exhibits plastic (flowing) properties. It is located below the lithosphere (the crust and upper mantle). • Continental Crust - thick parts of the Earth's crust, not located under the oceans. • Lithosphere - the crust plus the rigid, upper mantle. • Lower Mantle (semi-rigid) - the deepest parts of the mantle, just above the core. • Magma - molten rock withing the Earth's mantle. In seafloor spreading, magma moves from the asthenosphere to the crust. • Ocean - large bodies of water sitting atop oceanic crust. • Oceanic Crust - thin parts of the Earth's crust located under the oceans. • Subduction Zone - the area in which one part of the Earth's crust (a plate) is pushed underneath another plate as the two plates collide. • Upper Mantle (rigid) - the uppermost part of the mantle, part of the lithosphere. • Volcanos - a place on the Earth's surface where molten rock, gases and pyroclastic debris erupt through the earth's crust. Convergent Boundary Characteristics • Plates move towards each other • Old sea floor is destroyed • trenches Transform Boundary Transform Boundary Characteristics • • • • Plates move past each other No destruction or creation of crust Faults are formed Numerous types of faults