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Plate Tectonics

Plate Tectonics. Earth back then…. Earth Now. Pangea. World used to be a “super continent’ PANGEA. Proof of Pangea. Fossil Evidence – only a few places in the world Fossils – Remains of skeletons preserved in rock seen in multiple continents; walk or swim?. Proof of Pangea.

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Plate Tectonics

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  1. Plate Tectonics

  2. Earth back then….

  3. Earth Now

  4. Pangea • World used to be a “super continent’ • PANGEA

  5. Proof of Pangea • Fossil Evidence – only a few places in the world • Fossils – Remains of skeletons preserved in rock seen in multiple continents; walk or swim?

  6. Proof of Pangea • Glacier Evidence (from ice age) • Large valleys, scratches on rocks seen in multiple places

  7. Proof of Pangea • Glacier Evidence – scratches on rocks

  8. Proof of Pangea • Glacier Evidence – scratches in warm places…. Any better explanation?

  9. How did we get to now?

  10. Theory of Continental Drift • Alfred Wegner • Earths plates floated • Drifted apart over millions of years

  11. Recall the layers…. Upper mantle + crust = ???? Lithosphere • Asthenosphere • - Fluid layer

  12. Theory of Plate Tectonics • Land masses existed as plates that MOVE

  13. Theory of Plate Tectonics • How movement occurs • Convection currents • Heating • Some places hotter than others • Different materials heat differently • Difference causes pushing

  14. Thoery of Plate Tectonics • Plate boundaries & their interactions

  15. Evidence for Plate Tectonics • Pieces of earth move & some will collide • Earthquakes & volcanoes provide evidence • Earthquakes & volcanic eruptions occur at plate boundaries

  16. What happens when the plates move?

  17. Plate boundaries & interactions • 3 possibilities exist • Divergent Plate Boundaries • Convergent plate boundaries • Transform plate boundaries

  18. Plate boundaries & interactions • Divergent Plates • Plates move apart • Rising magma pushes crust • Old rock pushed farther away • New rock at spreading - Ridge (ocean) / Rift (land)

  19. Techniques to learn about earth -Volcanology Things to look for: Volcano types: Rift eruptions • Occurs at spreading ridges of mantle • Ocean or land • Easy flowing eruptions • Large amount of lava

  20. http://www.seed.slb.com/en/scictr/watch/living_planet/mountains.htmhttp://www.seed.slb.com/en/scictr/watch/living_planet/mountains.htm

  21. Plate boundaries & interactions • 3 types of collisions: • Oceanic – continental • Oceanic – oceanic • Continental – continental • Convergent Plates • Plates move closer together • 2 types of rock • Oceanic - under water • Continental - above water • Possible combinations???

  22. Plate boundaries & interactions Oceanic - Continental • Denser plate SUBDUCTS (slides under) • Oceanic (basalt) is denser = ALWAYS subducts below continental (granite) • Less dense plate rises • Subducted plate melts & magma is pushed up • Mountains & volcanoes created Pushes up from subducted plate

  23. Plate boundaries & interactions • Denser plate SUBDUCTS (slides under) • Older = denser = subducts • NO uplift • Subducted plate melts • Chain of volcanoes form @ subduction site (island arc) Plates are level

  24. Plate boundaries & interactions Continental - Continental • NO subduction because of similar density • Crushing & crumbling of rocks • Mountain formation

  25. Plate boundaries & interactions • Transform plate boundaries • Sliding past each other • NO new land forms • Produce earthquakes

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