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Plate_Tectonics_2016.notebook February 03, 2016 The Continental Drift Theory Continental Drift - All continents formed a single landmass and have drifted to current locations Alfred Wegener (1912) German scientist who proposed this Theory. He called this supercontinent ____________ 1 Plate_Tectonics_2016.notebook February 03, 2016 Wegener's Evidence: 1. Fossils 2. Rock Formation 3. Climate Not quit e enough .. believed .No one him! 2 Plate_Tectonics_2016.notebook February 03, 2016 Fossil Evidence shows that organisms lived on both continents when they were joined Mesosaurus: freshwater reptile Glossopteris: found on all southern continets 3 Plate_Tectonics_2016.notebook February 03, 2016 Rock Evidence: similar rock types and ages are found on different continent. Rock Types 4 Plate_Tectonics_2016.notebook February 03, 2016 Climate Evidence: warm weather fossils in cold places and glacial clues in warm places Spitsbergen, Arctic Ocean warm weather fossil here? Glacial Scouring 5 Plate_Tectonics_2016.notebook February 03, 2016 Chapter 10 Sec 2 Sea floor spreading proves continental drift. * paleomagnetism 6 Plate_Tectonics_2016.notebook February 03, 2016 Midocean ridge a long, undersea mountain chain that has a valley at its center. • Seafloor spreading the process by which new oceanic lithosphere forms as magma rises to Earth’s surface and solidifies at a midocean ridge. Pushed continents apart by creation of new rock. • Rocks closer to the ridge are younger younger rock older rock it! Draw ! el it b a L 7 Plate_Tectonics_2016.notebook February 03, 2016 8 Plate_Tectonics_2016.notebook February 03, 2016 How did we discover this? 1947 scientists studying the ocean floor found: 1.The sediment that covers the sea floor is thinner closer to a ridge than it is farther from the ridge 2.The ocean floor is very young. less than 175 million years old. (on land 3.8 billion) rift crack in the earth's crust 9 Plate_Tectonics_2016.notebook February 03, 2016 The Earth has a magnetic field with 2 poles. electrical currents flow from South to North. t! I w a Dr Lines show direction and magnitude of the magnetic field. Paleomagnetism: Paleomagnetism: Basaltic rocks (igneous) forming at mid ocean ridges records and locks in the Earth's polarity as it cools Field Reversal field has reversed itself in the past Good to know: Harry Hess: Conclusive Evidence for the Theory of Seafloor Spreading *The Glomar Challenger (1968) was a research ship that drilled into the seafloor to obtain rock samples. 10 Plate_Tectonics_2016.notebook February 03, 2016 Magnetic Reversals When scientists placed these periods of normal and reversed polarity in chronological order, they discovered a pattern of alternating normal and reversed polarity in the rocks. Scientists used this pattern to create the geomagnetic reversal time scale. 11 Plate_Tectonics_2016.notebook February 03, 2016 Plate Tectonics 12 Plate_Tectonics_2016.notebook February 03, 2016 •Plate Tectonics: the theory that explains how large pieces of the lithosphere, called plates, move and change shape •lithosphere: the solid, outer layer of Earth that consists of the crust and the rigid upper part of the mantle •asthenosphere: the solid, plastic layer of the mantle beneath the lithosphere; made of mantle rock that flows very slowly, which allows tectonic plates to move on top of it 13 Plate_Tectonics_2016.notebook February 03, 2016 Plate Boundaries •The three types of plate boundaries are: 1. divergent boundaries 2. convergent boundaries https://www.youtube.com/watch?v=BlymeytlMiM 3. transform boundaries https://www.youtube.com/watch?v=tIuk2blBzHs https://www.youtube.com/watch?v=2q4Yqctq6nE •Each boundary is associated with a specific types of geologic activity. 14 Plate_Tectonics_2016.notebook February 03, 2016 Causes of Plate Motion •Convection the movement of heated material due to differences in density that are caused by differences in temperatures. hot, less dense material rises colder, denser material sinks •Heat comes from: • energy generated by Earth’s core • radioactivity within the mantle 15 Plate_Tectonics_2016.notebook February 03, 2016 Ridge Push: asthenosphere being pushed away from divergent boundaries Slab Pull: asthenosphere being pulled down near convergent boundaries 16 Plate_Tectonics_2016.notebook February 03, 2016 Continental Crust Characteristic Oceanic Crust 3550 km Thickness 512 km Granite (light) Composition Basalt (dark) to 3.8 billion B.P. Geological age to 150,000,000 B.P. 2.7 Density 3.0 Ave. +1,000 m Elevation Ave. 3,000 m No Remelted and destroyed Yes 17 Plate_Tectonics_2016.notebook February 03, 2016 Panthalassa Ocean Wegener's evidence for Continental Drift 1. "Puzzle Like" Fit of Continents 2. Fossil Clues 3. Climate Clues (glacial scouring) 4. Rock Clues 18
