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Get Out the Following Things:

Get Out the Following Things:. Paper off the table Pencil Turn in FF: Earth’s Layers Corrections Review your notes & CLEAR OFF YOUR TABLE!. Plate Tectonics. Looking at the world map, what do you notice about the shape of the continents?. Jot down your ideas on your paper….

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Get Out the Following Things:

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  1. Get Out the Following Things: • Paper off the table • Pencil • Turn in FF: Earth’s Layers Corrections • Review your notes & CLEAR OFF YOUR TABLE!

  2. Plate Tectonics

  3. Looking at the world map, what do you notice about the shape of the continents? Jot down your ideas on your paper…

  4. The thing is…the world didn’t always look like this! It used to look like this:

  5. How is this possible?!?!?

  6. Continental Drift Theory • The continents have shifted their position over geologic time

  7. At one time all land masses were connected into one piece called Pangaea

  8. Pangaea began to split apart 200 million years ago • Diagram North America Laurasia Greenland Eurasia Pangaea Africa West G. S.America Gondwanaland Antarctica East G. Australia India

  9. Continents • The continents are like packages on the seafloor conveyor belt

  10. Evidence • High probability that the continents fit together

  11. Evidence • Minerals, fossils, and mountains on now different continents match if the continents were together

  12. Evidence • Glaciation patterns indicate a common ice cap at the South Pole

  13. Evidence • Paleomagnetism (magnetism of old rocks) indicate a common pole if the continents were all connected

  14. So how do the continents move?

  15. Seafloor Spreading Theory: • Ocean floors are moving like broad conveyor belts

  16. New ocean floor crust is being created at the mid-oceanridges

  17. What causes this? Convection currents within the mantle • The up-welling leg of the current creates a divergent boundary which produces mid-ocean ridges

  18. The down-welling leg of the current creates one type of convergent boundary that results in trenches and a subduction zone

  19. What evidence do we have to support this idea? • Mid-ocean ridges are warmer than surrounding ocean floors • Active volcanoes on ridges, earthquakes on ridges • Mid-ocean ridge rocks are younger than surrounding ocean floor rocks • Mid-ocean ridge volcanoes are younger than volcanoes further away

  20. What evidence do we have to support this idea? • Ocean floor sediments are thin on the ridges and get thicker as the distance from the ridges increase • Polar reversal magnetism proves that the ocean floor is moving away from the ridges

  21. Speed of Spreading • Atlantic Ocean – 2-3 cm/year • South Pacific Ocean – 15-18 cm/year

  22. Plate Tectonics Theory • The lithosphere is divided into a number of large and small plates and the plates are floating on the mantle

  23. Lithosphere = the Earth’s crust plus the upper portion of the mantle layer

  24. Boundaries between Tectonic Plates

  25. Get Out the Following Things: • Plate Tectonic Notes • Plate Tectonic Directed Reading • MAKE SURE YOU HAVE YOUR TEXTBOOK!!!

  26. Plate Boundaries Divergent boundary: • Plates are moving away from each other • Mid-ocean ridges are created and new ocean floor plates are created

  27. Plate Boundaries Divergent boundary:

  28. Leif the Lucky Bridge Bridge between continents in Reykjanes peninsula, southwest Iceland across the Alfagja rift valley, the boundary of the Eurasian and North American continental tectonic plates.

  29. Convergent Boundary: plates are moving toward each other and are colliding (3 types)

  30. When Ocean Plates Collide with Continental Plates • Create subduction zones, trenches • Create near coast volcanoes

  31. When ocean plates collide with other ocean plates Island arcs are created (a pattern of volcanic islands created from a subduction zone that is located off the coast)

  32. When a continental plate collides with another continental plate • Mountainranges are created • (example: Himalayan Mountains)

  33. Himalayan Mountains Mountain Formation Video Clip

  34. Transform Boundary • Plates are neither moving toward nor away from each other, they are moving past one another.

  35. Transform Boundary • The plates may move in opposite directions or in the same directions but at different rates and frequent earthquakes are created (example: San Andreas Fault)

  36. San Andreas Fault

  37. So is the Earth getting bigger? • No • Plates are destroyed as fast as they are created (2 ways) • Plates may be subducted and melted or may push be pushed upward to form mountains

  38. Plate Tectonic Review

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