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Announcements

Announcements. 12/6 is the LAST day to turn in work for this Quarter. Sea Floor ( Due 11/26) Relative dating problem set (Due 12/3) Radiometric dating problem set (Due 12/5) Lab Practical 12/9. (Corrections procedure different, see your instructor. ) Unit exam 12/11

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Announcements

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  1. Announcements • 12/6is the LAST day to turn in work for this Quarter. • Sea Floor (Due 11/26) • Relative dating problem set (Due 12/3) • Radiometric dating problem set (Due 12/5) • Lab Practical 12/9. (Corrections procedure different, see your instructor.) • Unit exam 12/11 • Final essay 12/18 • Final exams 12/19 & 12/20

  2. Earth Science A study in change: Plate Tectonics

  3. Plate Tectonics: History • Began as continental drift • Suggested by Alfred Wegener. • Continental drift is the theory that all of the continents used to be one large landmass, called Pangaea.

  4. Continental Drift evidence • Jigsaw Puzzle-shapes of continents fit. • Fossil Evidence-matching fossils on separate continents. (Mesosaurus) • Geologic Features-mountain ranges, ages and kinds of rocks match along edges of continents. (Diamonds) • Ancient climates- glacier markings match on separate continents, some in areas that are now tropical.

  5. Continental Drift- a science failure! • Wegener couldn’t figure out HOW it worked! He had no driving force. • No reason for how it worked meant that people could find other reasons for his “proof”. • Science community needed a reason for making continental drift GO.

  6. Plate tectonics replaced continental drift • The theory of plate tectonics: • Lithosphere (solid crust and upper mantle) is broken into plates. • Tectonic Plate- A large, solid piece of the earth’s crust that includes the continents and ocean floor. • These plates float or ride on the asthenosphere.

  7. The main difference between plate tectonics and continental drift = Plate tectonics has a driving force = convection currents. (Demo)

  8. OH, Convection currents! Density! D= M/V

  9. How does it work? • Mantle is a liquid. • Recall: Temperature of Earth becomes warmer as you go deeper into Earth. • So, mantle rock near the core heats up and rises. As the rock rises, it cools; cool mantle rock then sinks. (Sound familiar? Like the atmosphere!) • Convection currents within the mantle drive the plate movement. IT’S ALL ABOUT DENSITY! • Hot fluids rise, cold fluids sink. • Think: Grocery store conveyor belt, and we are the groceries!

  10. So what? • Fun stuff happens when the plates move!

  11. Fun stuff like. . . • Earthquakes • Volcanoes • Mountains • Islands

  12. Plate Boundaries - where the action occurs (3 types) • Divergent- a place where 2 plates move away from each other. • Convergent- a place where 2 plates move towardeach other. • Transform-a place where 2 plates slide past each other.

  13. Plate Boundaries

  14. Transform Boundary Plate Boundaries

  15. Transform Boundaries • Areas where two plates slide past each other. • Not a smooth movement • Slip and stick pattern. • Cause of earthquakes! • San Andreas fault in California • Crust conserved (not created or destroyed)

  16. Divergent Boundaries Plate Boundaries

  17. Divergent Boundaries • Divergent- a place where 2 plates move away from each other. • Places where new crust is formed! • On land = Rift valley • In water = Mid-ocean ridge

  18. Divergent Boundaries • Mid-ocean ridges- underwater mountain ranges. (larger than the ones on land!) • Have a rift(tear) in the center - allows magma to flow to the surface. • Newest crust is in the center. (Igneous rock) • New crust forces old crust away from the ridge. • Earthquakes and volcanoes common.

  19. Divergent Boundaries

  20. How do we know? • Last week = Sea floor lab: • Magnetic field tells us!(Paleomagnetism) • Earth’s magnetic field changes! Reverses! Every so often. . . • As new igneous rock forms, magnetic minerals will line up with Earth’s magnetic field. • Bandsof rock along rift valleys and mid-ocean ridges alternate N/S directions!

  21. Other ways we know: • “Old” rock is found farther from a rift valley or mid-ocean ridge than “new” rock. • Fossils help us know this. • Fossils from recent eras are close to the boundary • Fossils from older eras are far from the boundary.

  22. Convergent Boundaries Plate Boundaries

  23. Convergent Boundaries • Convergent- a place where 2 plates move toward each other. • Places where crust is destroyed and recycled • Continent + continent = mountain • Continent + ocean = subduction zone/volcanoes • Ocean + ocean = island arc

  24. Subduction Zones • Continent + ocean = subduction zone • Continental crust is less dense and “floats”, oceanic crust is more dense and“sinks”. • Due to DENSITY! • The oceanic crust will get pushed underneath the continental crust. • Causes melting • Associated with volcanoes • Andes Mountains of South America.

  25. Plate Boundaries - Convergent Oceanic + Continental = subduction zone + mountain (So. America) Oceanic + Oceanic = subduction zone + island arc (Japan, Alaska) Continental + Continental = mountains (Mt. Everest)

  26. Mountains • Continental crust moving toward continental crust • Convergent boundary • No place to go, but UP! • Mt. Everest (29,035 ft; or 8,850 m)

  27. Mountains

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