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Plate Tectonics

Plate Tectonics. For these notes you will need a blank sheet of paper and Red, brown, and blue color pencil. A Scientific Theory is a well-tested concept that explains a wide range of observations.

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Plate Tectonics

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  1. Plate Tectonics For these notes you will need a blank sheet of paper and Red, brown, and blue color pencil

  2. A Scientific Theory is a well-tested concept that explains a wide range of observations. • The theory of Plate Tectonics explains the formation, movement and subduction of the Earth’s plates.

  3. The Earth’s lithosphere is made of a number of different plates moving in a variety of directions. • How the plates move relative to each other determines the type of boundary.

  4. What is the process of sea-floor spreading? • A process that continually adds new material to the ocean floorhappens at the mid-ocean ridge

  5. What evidence is there for sea floor spreading? • Molten material on sea floor • Magnetic strips alternate magnetic fields • Drilling samples from the Glomar Challenger • Rocks closer to the ridge were younger than rocks further away • http://geology.com/nsta/

  6. Divergent Boundaries • At divergent boundaries the plates are moving apart. • As the crust splits new crust is formed from magma moving up from below.

  7. Divergent Boundaries • These often form rift valleys. http://geology.com/nsta/

  8. Transform Boundaries • In Transform boundaries the two plates slide past each other (Pacific & North American Plate). • Usually find many earthquakes along these boundaries.

  9. Transform boundary • http://geology.com/nsta/

  10. Convergent Boundaries • Convergent Boundaries are formed when two plates collide. • One, or both, of the plates is subducted depending on the type of crust.

  11. Subduction • Subduction is when crust material is forced back down into the mantel.

  12. subduction? • Place where the ocean floor sinks back into the mantle • Cool dense crust (basalt) sinks under less dense continental crust (granite) • http://geology.com/nsta/

  13. Convergent Boundaries • If dense ocean crust meets light continental crust the ocean crust usually subducts. • The resulting friction often causes earthquakes and chains of volcanic mountains along the continents.

  14. Convergent Boundaries

  15. Convergent Boundaries • Ocean crust colliding with ocean crust can cause both plates to subduct. • The friction can cause volcanic island arcs in the ocean.

  16. Convergent Boundaries

  17. Convergent Boundaries • When continental crust meets continental crust the old ocean crust subducts while the light continental crust layers buckle up.

  18. Convergent Boundaries http://www.classzone.com/books/earth_science/terc/content/visualizations/es0804/es0804page01.cfm?chapter_no=visualization

  19. Convergent Boundaries • The Himalayan Mountains were formed in this manner.

  20. What is happening to the Pacific Ocean? • It is shrinking from subduction

  21. The Atlantic Ocean? • Fewer trenches causes less subduction so it is getting larger. http://geology.com/nsta/

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