1. Plate Tectonics
Lynn Hahn

2. Tectonic Plate Theory
Theory that explains the movement of continents across the globe. It explains why some earthquakes occur and volcanoes on land and the ocean floor.

4. The Tectonic Plates

5. The Tectonic Plates
Tectonic plates are large pieces of the lithosphere
2 different types of plate: Oceanic and Continental

6. How the plates move Convergent - Plates are moving towards each other
Divergent - Plates are moving away from each other
Transverse - Plates are moving past each other

7. Convergent Plate Boundaries
3 different types of convergent boundaries
Oceanic – Oceanic Convergence (2 oceanic plates converge
Oceanic – Continental Convergence (1 oceanic plate and 1 continental plate)
Continental – Continental Convergence (2 Continental plates
Convergent – when two objects move towards one another
The two objects are two tectonic plates

8. Oceanic – Oceanic Boundaries

9. Oceanic – Oceanic Boundaries
The slower moving plate SUBDUCTS the faster moving plate
Subducted plate – the plate that is forced into the mantle (the slower plate)
Forms trenches and volcanoes.
Hawaii is the result of underwater mountain ranges reaching above water.

10. Oceanic – Continental Boundaries

11. Oceanic – Continental Boundaries
Oceanic Plate is denser
Oceanic plate will subduct the continental plate
Forms offshore volcano range and an underwater trench
Ex. Andes Mountains

12. Continental – Continental Boundaries

13. Continental – Continental Boundaries
Two continental plates colliding
Neither plate subducts the other
One plate will crumble and break apart
Forms mountain ranges and a higher plateau
Ex. Himalayan Mountains and Tibetan Plateau

14. Divergent Plate Boundary

15. Divergent Plate Boundaries
Moving apart and makes a gap
Magma rises from asthenosphere and creates mountains as magma cools
Ex. Mid Atlantic Ridge
Results in new crust forming at a Rift Valley

16. Transform Plate Boundaries

17. Transform Plate Boundaries
Form Faults
Breaks in the lithosphere
Rocks move past each other
Ex. San Andreas Fault

18. Evidence for Plate Tectonics
In the middle of the oceans – The N and S are magnetic Poles
Magnets have a certain arrangement that makes them magnetic. Every 200,000 years the earth’s magnetic poles switch and S becomes North and North become South
The magnetic rocks on earth reflect the direction of magnetic North and magnetic South

19. Evidence Cont’d
As magma comes out of the floor at a divergent boundary, the material aligns itself the current magnetic poles. After the magma cools, this become permanent.
Once the poles switch, the new magma will have a new arrangement
PROOF!! – We see bands on the sea floor that reflect changes in magnetic N and S. IF the sea floor was not spreading, we wouldn’t

20. Other Evidence
Fit of the Continents - Noted the similarity in the coastlines of North and South America and Europe and Africa. Today the fit is done at the continental shelf and it is nearly a perfect match.
Rock Similarities
Rocks of same age match across ocean basins.
Termination of mountain chains.

21. References and Pictures
US Geological Survey Western Earth Surface Processes Team and the National Park Service,