1. Continental Drift

2. CH 9 Plate tectonics
1915 – Alfred Wegner proposed his continental drift hypothesis
His hypothesis:
200 mya one large supercontinent Pangaea (all lands) began to break up
Panthalassa – all oceans
Not widely accepted b/c he couldn’t explain why the plate movement occurred

3. Continental Drift Evidence
Wegner could not explain his hypothesis, but had evidence
4 Pieces of Evidence
Continents fit like puzzle pieces
Matching Fossils
Ancient climate (glacial evidence)
Rocks (matching mountain ranges)

4. Continents Fit Like Puzzle Pieces

5. Mesosaurus Fossils

6. Glacier Evidence

7. Rocks - Matching mountain chains

8. Breakup of Pangaea

9. Plate Tectonics

10. Plate Tectonics
Move slowly about 5 cm or 2.5 inches per year (same as fingernails)
Plate movement causes Earthquakes, volcanoes, mountains

12. Evidence for Plate Tectonics
Paleomagnetism: rocks align with Earth’s changing magnetic poles showing patterns of spreading
Ocean Drilling: seafloor sediments confirmed seafloor spreading
Earthquake patterns: show plate boundaries
Hot spots: show plate movement over magma plumes

14. Hot Spots

15. Hot Spots

16. What moves the plates? Convection Currents: the driving force behind
plate tectonics.

17. What moves the plates? Convection Currents: the driving force behind
plate tectonics.