1. Plate Tectonics

2. 4 Main Layers
The earth is divided into four main layers based on composition and state of matter.

3. A. Inner Core
Solid- It is very hot, but it is a solid because it is under so much pressure from all of the layers above it.
Made of Solid Iron - very dense metal

4. B. Outer Core
Liquid
Made of Iron and Nickel

5. C. Mantle
Liquid- peanut butter-like consistency. It can flow and move, but is almost solid in places.
Made of lighter elements.
Convection Currents occur in the mantle.

6. D. Crust Solid, rocky. We live on the crust
Made of mostly Oxygen and Silicon.
Made up of rocks and sediments.
Divided into Plates that move around on the mantle.

7. II. Convection in the Mantle
A. Since the mantle is liquid, the material can flow. Convection currents cause the material to move around.
B. Convection Current- when material is heated, it becomes less dense and rises. Then it cools, becomes more dense and sinks again.

8. III. Plate Tectonics
A. The solid, outer part of the crust and upper mantle is called the LITHOSPHERE.
B. The lithosphere floats on the liquid-like part of the mantle, which is called the ASTHENOSPHERE.
The lithosphere is broken into sections called PLATES. The plates get carried along as the asthenosphere moves due to convection currents, like a raft in a river.

10. IV. Alfred Wegener
A. Alfred Wegener believed the crust of the earth moved as early as the 1800s, but he couldn’t explain what made them move. He called his idea CONTINENTAL DRIFT. He thought the plates moved because of 4 reasons:

11. # 1- the shapes of the continents look like they fit together like a puzzle.
Pangea- supercontinent when all the continents joined together.

12. # 2- Fossils on continents beside each other match up.

13. # 3- Rock types and Mountain ranges on continents beside each other match up.

14. # 4- Warm climate fossils are found in Antarctica, and there is evidence of glaciers in places that are now tropical. A possible explanation is the continents moved.
Glossipteris- fern fossil found in Antarctica

15. Types of Plate Boundaries

16. When 2 plates meet….. 1- They can crash together =
Convergent Boundary OR
2- They can move away from each other = Divergent Boundary OR
3- They can slide past each other = Sliding/Transform Boundary

17. Convergent Boundaries
There are two types of Convergent Boundaries:
A. Subduction: when one plate is more dense than another, the more dense plate goes underneath the less dense plate.
Subduction
The 2nd type is collision

18. Convergent Boundaries: Subduction
One plate goes under the other
Features that occur: Earthquakes, Volcanoes, Ocean Trench
Remember:
“The Ocean floor is going DOWN!!!!”

19. Example
Mt. St. Helens- Juan de Fuca plate goes under the North American Plate.
What are some indicators that a volcano might erupt soon?

20. Convergent Boundaries, Collision
B. Collision: when the 2 plates are the same material. When they hit, they both buckle up
(this makes mountains)
The two plates have the same density, they buckle up and move to a higher elevation
Features: Earthquakes, Folded Mountains

21. Example Mt. Everest, Himalayas
The plates are still colliding and gaining Elevation
What are some forces of nature that keep Everest from getting much higher?

22. Divergent Boundaries When two plates move apart. Features:
In continents:
Rift Valley, Volcanoes, Earthquakes
In oceans:
Mid-Ocean Ridge, Volcanoes, Earthquakes

23. Examples:
Great Rift Valley, Africa
Mid-Atlantic Ridge, Atlantic Ocean

24. Example: Great Rift Valley, Africa

25. Sliding/Transform Boundary
When two plates slide past each other.
Features: Earthquakes

26. Example:
California- Pacific Plate slides past the North American Plate at the San Andreas Fault.

27. Example: San Andreas Fault Where is it?