1. Plate Tectonics
and Continental Drift

2. Continental Drift A theory from Alfred Wegener
States that continents can drift apart from one another and have done so in the past

3. Continental Drift This helps to support Pangea
Pangea was a landmass of all continents together
Pangea means “all earth”

4. Continental Drift Evidence of Continental Drift
Continents seem to fit together
Fossils of same plants and animals are found on both sides of the Atlantic Ocean

5. Seafloor Spreading
Many years later the thought of seafloor spreading was introduced.
Seafloor spreading is the process where new oceanic lithosphere is created as materials are pulled away.
As plates move apart, the seafloor spreads apart and magma rises to fill in the gap.

6. Seafloor Spreading
Mid-ocean ridges occur at areas of seafloor spreading
Mid-ocean ridges are underwater mountain chains
The Mid-Atlantic Ridge is the largest mountain chain in the world.

7. Plate Tectonics
Plate tectonics is the theory that Earth’s lithosphere is divided into plates that move around on top of the asthenosphere.

8. What makes them move??? 3 Possible forces: Ridge Push Convection
Slab Pull

9. Plate Boundaries Plates can move 3 different ways.
Collide, separate, or slide past one another

10. Plate Boundaries
When two plates meet and they push into one another it is called a convergent boundary.
Results in mountains and volcanos

11. Plate Boundary
Areas where oceanic plates sink down into the asthenosphere is called a subduction zone.

12. Plate Boundary
When two plates move away from one another we call it a divergent boundary.
Results in volcanos and seafloor spreading

13. Plate Boundary
When two plates slide past one another the boundary is called a transform boundary.
Results in a lot of earthquakes!

14. Movement of Plates Plates move so slow you can’t feel or see them.
Centimeters per year!
Motion is monitored through GPS systems.

15. EXIT SLIP Describe continental drift theory.
What are the 2 main pieces of evidence for continental drift?
Name the 3 types of plate boundaries.
Describe the movement at each plate boundary and what results from each .