04.Plate Tectonics[1]

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04.Plate Tectonics[1]

  1. 1. Geo 100- Useful Information <ul><li>Course Homepage: http://mercury.atmos.albany.edu/geo100/ </li></ul><ul><li>For SKN, email your name to instructor at </li></ul><ul><li>[email_address] </li></ul>
  2. 2. Theory of Plate Tectonics – an overview Geo 100N Spring 2005
  3. 3. Plate Tectonics -Overview <ul><li>The Lithosphere and Crust </li></ul><ul><li>Basic Concepts of Plate Tectonics </li></ul><ul><li>Plate Movements and Boundaries </li></ul><ul><li>Summary </li></ul>
  4. 4. Inside the Earth USGS
  5. 5. The Lithosphere http://volcano.und.edu/vwdocs/vwlessons/plate_tectonics/part1.html
  6. 6. Basic Concepts of Plate Tectonics
  7. 7. The Earth’s surface is covered by about 12 lithospheric plates USGS
  8. 8. The plates move slowly (a few cm/year). USGS
  9. 9. Most endogenic geological activity occurs at or near plate boundaries. Mt St Helens, 1980 Endogenic = process that originates within the Earth’s interior
  10. 10. Plate interiors are relatively quiet geologically
  11. 11. Plate Movements and Boundaries
  12. 12. Divergent boundaries <ul><li>Plates move apart </li></ul><ul><li>Volcanic activity is always present </li></ul><ul><li>Earthquakes are shallow </li></ul><ul><li>Two types of boundaries: </li></ul><ul><ul><li>Oceanic </li></ul></ul><ul><ul><li>Continental </li></ul></ul>
  13. 13. Oceanic Divergent Boundary <ul><li>Sea-floor spreading of oceanic lithosphere </li></ul><ul><li>examples: Mid Atlantic Ridge, East Pacific Ridge </li></ul>USGS
  14. 14. Sea-floor spreading of oceanic lithosphere USGS, Digital elevation model
  15. 15. Mid Atlantic Rift at Iceland Þingvellir (Thingvellir), Iceland
  16. 16. Continental Divergent Boundary <ul><li>Continental rifting </li></ul><ul><li>Eventually, oceanic crust is formed and divergence becomes oceanic type </li></ul><ul><li>Modern Example: East Africa </li></ul>
  17. 17. East African Rift Zone Oldoinyo Lengai, Kenya
  18. 18. Convergent boundaries <ul><li>Plates move toward each other </li></ul><ul><li>Volcanic activity common </li></ul><ul><li>Deep, medium, and shallow earthquakes </li></ul><ul><li>Three types of Convergent Boundaries </li></ul><ul><ul><li>Ocean-ocean </li></ul></ul><ul><ul><li>Ocean-continent </li></ul></ul><ul><ul><li>Continent-continent </li></ul></ul>
  19. 19. Ocean-ocean convergence <ul><li>Subduction – one oceanic plate subducts (dives) beneath the other </li></ul><ul><li>Volcanic island arc is formed </li></ul><ul><li>Example: Aleutian Islands </li></ul>
  20. 20. Aleutian Islands, Alaska Kanaga
  21. 21. Ocean-continent convergence <ul><li>During ocean-continent convergence, oceanic lithosphere always subducts beneath continental lithosphere </li></ul><ul><li>Continental volcanic arc formed </li></ul><ul><li>Example: Andes mountains </li></ul>
  22. 24. Continent-continent convergence <ul><li>Subduction does not occur (continental crust is too buoyant to be subducted) </li></ul><ul><li>Mountain building occurs without volcanism </li></ul><ul><li>Example: Himalayas, Alps </li></ul>
  23. 25. India-Asia Collision <ul><li>Collision of India with Eurasian plate caused uplift of the Himalaya, the highest mountains on Earth. </li></ul>
  24. 26. Transform boundaries <ul><li>Plates slide past each other </li></ul><ul><li>Little or no volcanic activity </li></ul><ul><li>Shallow earthquakes </li></ul><ul><li>Example: oceanic transform faults; San Andreas Fault </li></ul>
  25. 27. San Andreas Fault <ul><li>Pacific plate is moving NW relative to the North American Plate </li></ul><ul><li>As plates move, transform fault slips, and earthquakes occur </li></ul>
  26. 28. Summary <ul><li>Earth’s surface is covered by about 12 lithospheric plates. </li></ul><ul><li>The plates move slowly (2.5-15 cm/year). </li></ul><ul><li>Most volcanism and earthquake activity occurs at or near plate boundaries. </li></ul><ul><li>Plate interiors are relatively quiet geologically (some exceptions). </li></ul>
  27. 29. Geo 100- Useful Information <ul><li>Course Homepage: http://mercury.atmos.albany.edu/geo100/ </li></ul><ul><li>For SKN, email your name to instructor at </li></ul><ul><li>[email_address] </li></ul>

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