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
Has more magnesium and less aluminum and silicon than the crust
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. Tectonic Plates

8. 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

9. 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

10. 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.

11. How Plates Move

12. 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

13. 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

14. 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!

15. Evidence of Pangea

17. Sea Floor Spreading

18. 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

19. Different Types of Boundaries

20. 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

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

22. Divergent Boundary – Iceland

23. Divergent Boundary - Oceanic

24. Divergent Boundary - Continental

25. 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

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

27. Convergent Boundary – Indian and Eurasian Plates
Indian Plate

28. Convergent Boundary – Oceanic & Continental
&

29. Convergent Boundary – Oceanic & Oceanic
Note – plates are reversed
&

30. Convergent Boundaries - Continental
&

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

32. Transform Boundary – San Andreas Fault

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

34. 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
(watch YOU TUBE video)

35. Volcanoes
A volcano is a mountain that may form around the opening as the lava cinders build up
Occurs at plate boundaries

36. 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

37. Amazing sight in the South Pacific

38. 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.

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

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

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

47. The trail left by the yacht...

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

53. And, while they were watching...

59. A brand new island formed...

62. A plume of black ash...

64. 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