1. Plate Tectonics
Chapter 9.2 – 9.3

2. Plate Tectonics
Proposed in 1965 by Tuzo Wilson = combination of Wegener & Hess’s ideas.
Convection Currents move the lithospheric plates causing geologic activity – (mountain building, volcanic eruptions and earthquakes)

3. Convection Currents
The magma in the lower mantle is warmer. It expands, becomes less dense and rises.
When it reaches the upper mantle it cools, contracts, becoming more dense and sinks.
This constant rise and fall of magma causes the convection currents that drive plate tectonics.
The crust plates ride along on top of these convection currents.
Upper Mantle - COOLER
Lower Mantle - HOTTER

4. Earth Layers
1. Lithosphere: the ridged crust and upper part of the mantle.
Cool, hard and solid
Breaks very easily
2. Asthenosphere: the lower mantle
Hot and plastic-like
Flows easily

5. The lithosphere is broken up into 7 large plates and 20 smaller plates

6. The plates have boundaries As they move they affect one another.
Convergent Boundary
Divergent Boundary
Transform Boundary

7. Plate Tectonics Reference Table
You need to know how to read this table!!

8. Pacific Plate – Where the Action is! RING OF FIRE!!

9. Hawaii Hawaii is a chain of islands made from an underwater volcano.
Yet Hawaii is NOT on a plate boundary.
How was Hawaii created?

10. Hawaiian Hot Spot Hawaii is in the middle of the Pacific Plate
Not on a boundary.

11. Magma Rises under Hawaii
Hot spot is located in the mantle and does not move
The Pacific Plate moves NW over the hot spot forming a line of volcanoes.

12. Plate Boundaries!!
Divergent
Convergent
Transform

13. Divergent Boundary
When Plates Divide or Separate

14. Step 1 – Rift Valley Magma pushes up cracks in the crust
Convection causes the separated plates to move and form a rift valley.

15. Step 2 – Add Water
The valley widens and begins to be filled with water. (Red Sea)

16. Step 3 – Ocean Formed Eventually an ocean forms
At the rate of 6 cm per year
Ex. Mid Atlantic Ridge

17. Divergent Boundaries Map

18. Transform Boundary Two Plates slide past each other
Also called strike-slip boundary
Ex: San Andreas Fault in California

19. San Andreas Fault The Pacific Plate moves North
The North American Plate moves South

20. San Andreas Fault
Causes stress that leads to Earthquakes in California

21. Convergent Boundaries
2 Plates colliding into each other.
Example: Himalayan Mountains formed when India collided with Asia

22. We will Continue these notes tomorrow
We will Continue these notes tomorrow!!! There is a lot to know about Convergent Boundaries!