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Plates

Plates. Guest Lecture by Dr. Webster. Asthenosphere Continental crust Convergent margin Divergent margin Earthquake Lithosphere. Oceanic crust Plate tectonics Subduction Transform margin Volcano Volcanoes. Vocabulary of the Day. Goals.

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Plates

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  1. Plates Guest Lecture by Dr. Webster

  2. Asthenosphere Continental crust Convergent margin Divergent margin Earthquake Lithosphere Oceanic crust Plate tectonics Subduction Transform margin Volcano Volcanoes Vocabulary of the Day

  3. Goals • Distinguish among types of plate tectonic settings produced by plates diverging, converging, and sliding past each other. • Relate modern and ancient geologic features to each kind of plate tectonic setting. • Relate certain geologic hazards to specific plate tectonic settings. • Universal principles are discovered through observation and experimental verification.

  4. Prior Knowlege • Please get out a piece of paper and write your name on it. • What do you already know? I’m going to show you a few geographic features, I would like you to tell me • A) What is it (name if you know)? • B) How it was formed?

  5. Question 1 • A) What is it? (name if you know) • B) How did it form?

  6. Question 2 • A) What is it? (name if you know) • B) How did it form?

  7. Question 3 • A) What is it? (name if you know) • B) How did it form?

  8. Question 4 • A) What is it? (name if you know) • B) How did it form?

  9. Question 5 • A) What is it? (name if you know) • B) How did it form?

  10. Question 6 • What ONE idea or concept do all five of those geographic features have in common?

  11. Plate Tectonics history • Plate Tectonics is relatively modern model to explain many disparate observations - like the 5 slides from the beginning. • Observations supporting a ‘drift’ theory were made as far back as 1600s • Taylor and Wegener in early 1900s published more complete drift theory

  12. Drift • Observations supporting drift • Fossils • Shapes of continents • BUT - in early 1900’s lacked any way to explain drift • What could make rock cross rock?

  13. Post WWII • Paleomagnetism • Seafloor spreading • + Drift evidence • Observations all need to be explained by a coherent model • Plate Tectonics! • This was a major shift in the scientific view of how the world works

  14. Model of Earth Today • Draw • Three things can happen at the boundaries

  15. Today - convergent • Two types of crust • Drawing • So - can have 3 combos of convergent • Oceanic crust-oceanic crust • Continental crust-continental crust • Continental crust-oceanic crust

  16. Oceanic Thinner (7 km) Different material (basalt) More dense (3 g/cm^3) Younger (200 million years old) Continental Thicker (10-70 km) Volcanic rock with sedimentary on top Granitic materials Less dense (2.7 g/cm^3) Older - billions of years Two Types of Crust

  17. Model of plate tectonics • Must explain the appearance of landscape features - observations

  18. Continental-Oceanic • Predict - which will go under? • What prior knowledge use to predict? • Draw • Subduction

  19. Melting Temperatures http://hyperphysics.phy-astr.gsu.edu/HBASE/geophys/meltrock.html

  20. Subduction predictions • Make a list • Where do we expect to see continental -oceanic crust collisions

  21. SA • http://geology.com/plate-tectonics.shtml

  22. You try • Oceanic crust - oceanic crust • Label features you expect to see.

  23. Examples on Earth • http://geology.com/plate-tectonics.shtml • Top down drawing of area • Can you identify any other places on Earth?

  24. Aleutians

  25. Continental-Continental • Where on the map?

  26. Himalayas • Folded sedimentary rock • Sedimentary - suggests ocean bed • Folding pattern suggests bottom to top pressure http://library.thinkquest.org/10131/geology_visual.html

  27. Hazards associated with convergent margins • Volcanoes • Earthquakes

  28. Summary so far • The plate tectonic model describes how plates can collide. • Colliding plates explain volcanoes, earthquakes, oceanic trenches, island arcs, mountains, and the relative positioning of these features. • One model - describes many observables.

  29. Plate Tectonics Model • Hypotheses often cause scientists to develop new experiments that produce additional data. • Think of an experiment that might support plate tectonics model

  30. More support for plate tectonics • And also directly measured motions with VLBI in 1980’s! • And ground based positions with satellites in 1990’s

  31. Assessment • Write a paragraph describing how the Aleutian Islands and nearby geographical features formed. Sketch the relevant plate configuration with features.

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