1. Continental Drift

2. Today’s Objectives SWBAT:
Explain continental drift and analyze the evidence for the theory of continental drift.

3. What is Continental Drift?

4. Continental Drift
Continental Drift – Movement of the Earth’s continents relative to each other.
Proposed by German geologist Alfred Wegener in 19teens.
Believed continents were part of a single landmass he called Pangaea (all lands).
Surrounded by Panthalassa (all seas)
Over time Pangaea broke up into smaller continents and drifted to their present locations.

5. Evidence for Continental Drift
1. Shape of continents
2. Fossils
3. Rock Evidence
4. Glacial Deposits
5. Seafloor Spreading
6. Paleomagnetism

6. Evidence for Continental Drift
1. Shape of Continents

7. Evidence for Continental Drift

8. Evidence for Continental Drift
2. Fossils
The same fossils were found on different continents.
Mesosaurus was found in both western Africa and eastern South America.
Mesosaurus was incapable of swimming across large bodies of water.

9. Evidence for Continental Drift
3. Rock Evidence
Age and type of rocks are similar in coastal regions of widely separated areas.
Appalachian Mountains and Caledonian Mountains have similar age and structure.

10. Evidence for Continental Drift
4. Glacial Deposits
Rocks with glacial scars on South America and Africa, but have much warmer climates now.
Continents were positioned over the South Pole.

11. Evidence for Continental Drift
5. Seafloor Spreading – 1940’s
Scientists wanted to map the Mid – Atlantic Ridge (undersea mountain range in Atlantic ocean)
Rock samples from oceanic crust is younger than continental crust.
Harry Hess, geologist from Princeton, proposed a break in the ocean crust and magma could come up and solidify.
Only possible if the ocean floor is moving away on both sides of the ridge.

12. Evidence for Continental Drift

13. Evidence for Continental Drift

14. Evidence for Continental Drift
6. Paleomagnetism
Paleo means ancient
Paleomagnetism is the study of changes in the earth’s magnetic field over history.
Where does the magnetic field come from?
Outer Core

15. Evidence for Continental Drift
6. Paleomagentism
Sometimes the North and South Pole change magnetic alignment (north becomes south and vice versa)
Magma that comes up solidifies and “locks in” the orientation of the magnetic field.
Rocks are the key to showing the magnetic field has changed.

16. Evidence for Continental Drift

19. Practicing Writing Exercise
What is continental drift? What evidence do we have that supports the idea of continental drift? Be specific!