1. Plate Tectonics
Liz LaRosa for use with my 5th Grade 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
Is denser than the crust

5. Earth Layers Asthenosphere: from greek word “weak”.
Zone of weak, easily deformed rock in the upper mantle.
Lithosphere: from greek word “stone”.
Floats on the asthenoshpere
Includes all of the crust and part of the upper mantle.
Cool rigid portion of the Earth
Divided into seven major plates…

6. 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

7. Apple Demo
Compare the layers of the Earth to this apple.

8. STOP

10. Tectonic Plates

11. Plate Tectonics Greek – “tektonikos” of a builder
Theory scientists use to explain plate movement
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

12. Plate Tectonics Plates in constant motion….very slow
Moves only few cm per year
Boundaries where plates meet are usually the site of earthquakes and volcanoes
Movement of plates causes Earth’s surface to change constantly and dramatically (crumpling rocks, folding them, stretching and cracking)
Moves continents around globe
Causes earthquakes and volcanic eruptions

13. Convection Transfer of heat
Cannot take place without a source of heat.
Ex. Hot water is less dense than cold water and rises, causing convection currents which transport energy.

14. How Plates Move

15. Plate Tectonics
Plates move away from each other along divergent boundaries
Plates collide along a convergent boundary
Plates grind past each other along transform fault boundaries
These plate movements have produced most of the world’s volcanoes, earthquakes, high mountain ranges, and deep ocean trenches

16. Continental Drift Alfred Wegener 1900’s
Continents were once a single land mass that drifted apart.
Fossils of the same plants and animals are found on different continents
Called this supercontinent Pangea, Greek for “all Earth”
245 Million years ago

17. Remember The continents and oceans are on Earth’s plates.
Because plates move, the continents we live on today were different places in the past.
They will continue to move in other positions in the future!

18. Evidence of Pangea

19. Discussion
How were similar rock types used to support the continental drift hypothesis?
Similar rock types in mountains such as the Appalachian Mountains and the Caledonian Mountains suggest that North America and northern Europe were at one time connected as part of a single landmass. Likewise, similar volcanic rocks in Africa and South America suggest that these two continents were also joined.

21. Sea Floor Spreading

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

24. STOP

25. Different Types of Boundaries

26. Divergent Boundary Caused by magma being pushed upward under a plate
Magma presses against plate
Melts and stretches lithosphere until it cracks
Magma flows into the gap and cools to form new crust

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

28. Divergent Boundary – Iceland

29. Divergent Boundary - Oceanic

30. Divergent Boundary - Continental

31. Convergent Boundary Three kinds of collisions possible
Oceanic plate collide with oceanic plate: one of the plates is pushed under the other.
The plate that is forced down, melts…creating a trench
Two continental plates collide: one forced under other.
Plates crumple and fold, forming mountain ranges
Oceanic plate collides with continental plate: oceanic plate forced downward.
Mountains and volcanoes form along the boundary between plates

32. FACT
80% of the worlds volcanoes and 90% of all earthquakes occur along convergent boundaries!!!

33. Convergent Boundary – Indian and Eurasian Plates
Indian Plate

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. Transform Fault Boundaries
Two plates move past each other in opposite directions

38. Transform Boundary – San Andreas Fault

39. Discussion What is plate tectonics?
Plate tectonics is a theory that Earth's surface is made of rigid slabs of rock, or plates, that move with respect to each other.
What are Earth's outermost layers called?
Earth's outermost layers, which include the crust and the solid, uppermost mantle, make up the lithosphere.

40. Discussion What are the three types of plate boundaries?
Divergent, transform, and convergent are the three types of plate tectonic boundaries.
Why do tectonic plates move?
The mantle moves horizontally under Earth's plates due to convection currents. Earth's plates carried along by the moving mantle below them.

41. STOP

42. FACT
95% of all earthquakes occur at or near the edges of moving plates, along great cracks in Earth’s crust called faults.

43. Earthquakes As plates continue to move, rocks put under great strain
Rocks bend and stretch until they reach their breaking point
Suddenly, rocks snap and move into new positions
A jolt on energy is released
Felt as earthquake
Causes tsunami’s

45. Volcanoes
A volcano is a mountain that may form around the opening as the lava cinders build up
Occurs at plate boundaries
(convergent: oceanic/continental)

46. Formation of Volcanoes
Magma, or molten rock beneath Earth’s surface is forced up through an opening in Earth’s surface.
Molten rock erupts as lava
Hot molten rock is pushed upward to form volcanic mountains

47. Types of Volcanoes Shield volcano Looks like a warriors shield
Long, flat, slightly domed

48. Types of vocanoes Cinder cone volcano
Built up from ashes/cinders and rocks that burst during a violent eruption
Rocks fall back to surface, creating a cone.

49. Types of volcanoes Composite volcano
Switches between quiet eruptions of flowing lava and violent eruptions
Most powerful type of eruption

51. Discussion
How are earthquakes and volcanoes related to the theory of plate tectonics?
Most volcanic eruptions and earthquakes occur along plate boundaries.

52. Amazing sight in the South Pacific

53. In the South Pacific the water is much warmer than normal
In the South Pacific the water is much warmer than normal.  Environmentalists have said that Global Warming causes it.  Other Scientists have noted there is a substantial amount of volcanic activity in that same area.  It has a tendency to warm water, also.  Here’s an interesting set of photos.

54. August 2006, the yacht 'Maiken' is travelling in the south Pacific when they came across a weird sight...

55. It was sand in the water, and floating ON TOP of the waves...

58. This is not a beach, it is volcanic stones floating on the water.

62. The trail left by the yacht...

66. And then this was spotted... ash and steam rising from the ocean...

68. And, while they were watching...

74. A brand new island formed...

77. A plume of black ash...

79. Review 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