1. Continental Drift and Plate Tectonics

2. The Origins
Alfred Wegener developed a theory that the continents once formed a giant supercontinent

4. Evidence of Continental Drift
Jigsaw puzzle like

5. Evidence
Plant and animal fossils found on several different continents were quite similar.
Physically impossible for these organisms to have traveled across the ocean
Compelling evidence that the two continents were once joined.
Plant/
Animal
Evidence

7. Evidence
Broad belts of rocks in Africa and South America are the same type
Mountain belts match up
Rock
Evidence

8. Evidence
Glacial striations on rocks- cuts from when glaciers move match up across the world
Glacial
Evidence

9. So the Continents Move? Theory lead to Plate Tectonics
Plate Tectonics now is able to explain why, how, and where the plates will move.
Continental Drift only knew that plates moved, but DID NOT KNOW HOW

12. Projected Future

13. Crust- hard solid
Mantle- soft solid
Outer Core- liquid
Inner Core- solid

15. Earth’s Structure Lithosphere – crust and upper mantle
Crust is broken up into large segments called plates

16. Asthenosphere – lower mantle

17. Plates and Layers Plates are made out of the Lithosphere
“Float” on Asthenosphere
Acts like a liquid and a solid
Continental Plate
Oceanic Plate
Lithosphere
Asthenosphere
Mantle

18. Inside the Mantle
Because the earth is very hot inside, a current of heat flows from the core to the crust.
This is called convection current (heat rises, cools, then sinks down)

19. Convection Currents Explains how plates move
Wegner could never explain this!!

20. Plate Movements Plates are sitting onto of the mantle and “float”.
They either push together, pull apart, or grind against each other.

21. Divergent Plate Two plates push apart
Creates sea floor spreading, leading to the formation of new crust
SEA FLOOR SPREADING:
Mid Atlantic Ridge – magma coming up creating new rock in center

22. Forming a Divergent Boundary
To view this animation, click “View” and then “Slide Show” on the top navigation bar.

23. Where is the youngest rock? Where is the oldest rock?
Is there is a pattern?

24. What Do the Volcanoes Show?
75 km
40 myo
50 km
30 myo
20 myo
25 km

25. Convergent Boundary Plates colliding together Ocean-Ocean : Volcanoes
Ocean – Continental : Volcanoes
Continental – Continental: Mountains

26. Convergent Boundary

27. Convergent Boundary

28. Transform Boundary Plates slide past each other
Creates large breaks in rock
Earthquakes
Examples: San Andreas Fault