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Transcript
Geology 112 - Earthquakes 1 Activity #8 - Plate Tectonics and Earthquakes Objective: Learning Outcome #1 Outline Plate Tectonics 2 • Evidence for plate tectonic theory • Plates - Lithosphere and asthenosphere • Plate boundaries http://bingweb.binghamton.edu/~ajones/#Seismic%20Waves Dynamic or Static? 3 4 Internal Structure of the Earth http://web.ics.purdue.edu/~braile/edumod/slinky/slinky.htm 5 Some History Fit of the Coastlines? http://pubs.usgs.gov/gip/dynamic/dynamic.html 7 Tectonics Links Together Evidence Rocks, Fossils, and Sediments 6 8 Continental Drift Hypothesis 9 10 Continental Drift Hypothesis Breakup of Pangaea "Scientists still do not appear to understand sufficiently that all earth sciences must contribute evidence toward unveiling the state of our planet in earlier times, and that the truth of the matter can only be reached by combing all this evidence. . . It is only by combing the information furnished by all the earth sciences that we can hope to determine 'truth' here, that is to say, to find the picture that sets out all the known facts in the best arrangement and that therefore has the highest degree of probability. Further, we have to be prepared always for the possibility that each new discovery, no matter what science furnishes it, may modify the conclusions we draw." Alfred Wegener. The Origins of Continents and Oceans (4th edition) Continents, Like a Ship, Sailing through Ocean Crust? 11 The Seafloor 12 Physical - Interior of Earth Low Velocity Zone 13 15 0 Depth (km) Increasing Seismic Velocity • Decrease in rate of increase in seismic velocity (especially S wave) • Less Rigid “Squishy” • 1% Molten Seismic Velocities Physical Layering Lithosphere and Asthenosphere 14 16 Oceanic vs. Continental Lithosphere 17 • Lithosphere = Crust and uppermost mantle • Strong lithosphere vs. weak asthenosphere • Rigid lithosphere vs. “squishy” asthenosphere • Elastic lithosphere vs. viscous asthenosphere • Lithosphere is thin under oceans (5-100 km-thick) • Thicker under continents (100-200 km-thick) • Lithosphere is more rigid under oceans Evidence - Mid-Ocean Ridge Plate Boundaries Science Channel - Bill Nye and Neil Driscoll 18 http://youtu.be/6CsTTmvX6mc 19 Evidence Rock Samples from Mid-Ocean Ridge • Volcanic rocks - Basalt • Pillow-shaped - Underwater eruptions http://www.whoi.edu/home/oceanus_images/pillow/ 20 Seafloor Spreading 21 Evidence - Oceanic Crust Magnetism 22 magnetic Educational Multimedia Visualization Center of the Department of Earth Science, U.C.S.B http://emvc.geol.ucsb.edu/index.htm http://geology.uprm.edu/Morelock/1_image/magstr.jpg 24 23 Magnetic Reversals and Seafloor Spreading https://youtu.be/BCzCmldiaWQ Educational Multimedia Visualization Center of the Department of Earth Science, U.C.S.B http://emvc.geol.ucsb.edu/index.htm Vine-Matthews Hypothesis 25 Testing the Hypothesis by Deep Sea Drilling 26 Harry Hess Vine & Matthews Educational Multimedia Visualization Center of the Department of Earth Science, U.C.S.B http://emvc.geol.ucsb.edu/index.htm Age of Oceanic Lithosphere 27 Activity 8 Summary 28 • Seismic Wave Propagation - Internal Structure of Earth • Pangea and continental drift • Evidence of plate tectonics • Low Velocity Zone - Asthenosphere beneath lithosphere • Difference between ocean and continental lithosphere • Seafloor spreading and testing of Vine-Matthews hypothesis http://www.ngdc.noaa.gov/mgg/ocean_age/