1. Plate Tectonics
Liz LaRosa for use with my Science Class

2. Earth’s Layers
The Earth's rocky outer crust solidified billions of years ago, soon after the Earth formed.
This crust is not a solid shell; it is broken up into huge, thick plates that drift atop the soft, underlying mantle.

3. The Crust Outermost layer 5 – 100 km thick
Made of Oxygen, Silicon, Aluminum

4. The Mantle Layer of Earth between the crust and the core
Contains most of the Earth’s mass
Has more magnesium and less aluminum and silicon than the crust
Is denser than the crust

5. The Core Below the mantle and to the center of the Earth
Believed to be mostly Iron, smaller amounts of Nickel, almost no Oxygen, Silicon, Aluminum, or Magnesium

6. Tectonic Plates

7. Plate Tectonics Greek – “tektonikos” of a builder
Pieces of the lithosphere that move around
Each plate has a name
Fit together like jigsaw puzzles
Float on top of mantle similar to ice cubes in a bowl of water

8. Continental Drift
In 1912 a German meteorologist named Alfred Wegener noticed that the continents fit together like puzzle pieces.
He proposed that the continents were joined together in the past, in a large land mass called Pangaea, Greek for “all Earth”
Fossils of the same plants and animals are found on different continents.

9. Over time, the continents drifted apart – Wegener named his theory “Continental Drift”.

10. Evidence of Pangea

11. He supported his theory with four pieces of evidence.
1. Puzzle like fit of continent edges

12. 2. Matching fossils of plants and animals on once connected land areas.
Fossils of Glossopteris are found in Permian rocks of South Africa, India, Australia, South America, and Antarctica

13. 3. Rock similarities and ages
Mountains in South America and Antarctica are believed to have formed as part of the same mountain chain.

14. 4. Climate evidence (Glacial evidence in Africa, South America, Australia, and India and tropical plant fossils in Arctic areas)
Fossils found in Antarctic soil indicate that the now frigid continent was once lush with trees and ferns, and home to dinosaurs, amphibians, and later, marsupials.

15. Wegener’s theory made sense, but no one wanted to accept it until they knew HOW the continents moved.

16. Continental Drift Whiplash
In the 1960’s, a Princeton University scientist named Harry Hess, discovered how the continents drifted.
Continental Drift Whiplash

17. Seafloor Spreading
Magma in the mantle rises and pushes the plates apart, forming new oceanic crust.

18. How Plates Move

19. Sea Floor Spreading
Mid Ocean Ridges – underwater mountain chains that run through the Earth’s Basins
Magma rises to the surface and solidifies and new crust forms
Older Crust is pushed
farther away from the ridge

20. Seafloor Spreading causes Continental Drift

21. Supporting evidence of seafloor spreading
1. Magnetic iron particles record the time of the rock formation.
2. Rocks farther away from the opening age at the same rate on both sides.

22. A map of the ocean floor provides even more evidence http://maps

23. Iceland shows seafloor spreading above the water, which makes it easier to study

24. Plate Tectonic Theory
Theory of Plate Tectonics -Earth’s crust is broken into plates which float and move.

25. Earth’s crust made of many plates is similar to the panels on the outside of a soccer ball.

26. There are about 13 plates covering Earth’s surface

27. Plate Boundaries (edges)
When the plates move, their boundaries, or edges, can scrape and collide.

28. Different Types of Boundaries

29. Convergent Boundary
Plates move toward each other

30. Convergent Boundary
When two continental plates move into each other, the plates combine and form mountains. (India into Asia)

31. Convergent Boundary – Indian and Eurasian Plates
Indian Plate

32. Convergent Boundary
When an oceanic plate runs into a continental plate, the heavier oceanic plate subducts (sinks) back into the mantle.
Volcanic mountains are created along this edge.

33. Oceanic plate into continental
Example: Pacific plate (oceanic) subducts (sinks) under Japan (continental).

34. Convergent Boundary – Oceanic & Continental
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35. Convergent Boundary – Oceanic & Oceanic
Note – plates are reversed
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36. Convergent Boundaries - Continental
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37. Divergent Boundary
Plates move apart

38. When both diverging plates are both oceanic, it is called seafloor spreading (Mid-Atlantic Ridge)

39. Divergent Boundary - Oceanic

40. When both diverging plates are continental it is called rift valley formation (Africa)

41. Divergent Boundary - Continental

42. Divergent Boundary – Arabian and African Plates
Arabian Plate
Red Sea
African Plate

43. Divergent Boundary – Iceland

44. Transform Boundary
Plates slide past each other

45. San Andreas Fault, CA
Each time the plates slide past each other, an earthquake occurs

46. San Andreas Fault

47. Transform Boundary – San Andreas Fault
United States
California

48. Find the three boundaries

49. Asthenosphere A plastic-like layer found below the lithosphere.
The rigid oceanic and continental plates of the lithosphere sit on top

50. The Asthenosphere is heated by the hot Outer Core

51. Convection Current crust mantle core
Hot material rises, cooler material sinks, creating a current, called a Convection Current

52. When the asthenosphere moves, it carries the lithospheric plates (divergent, convergent, and transform motions) Convection currents cause plate motion

53. Every time these plates move we get earthquakes, volcanic eruptions, and possibly tsunamis

54. Review (These will be quiz questions)
Name the 3 main layers of the Earth
What is a tectonic plate?
What was Pangea?
What is Sea-Floor spreading?
Name the three different types of plate boundaries and one location on Earth for each one.
What causes the plates to move?