1. Proving Wegener

2. Mid Ocean Ridge The Mid-Atlantic Ridge is part of under-seas Mountain Range known as Mid-Ocean Ridge The rocks found on Continents are as old as 3.8 billion years old. The oldest rocks in the ocean are only 190 million years old. The closer to the Mid-Ocean Ridge the young the rocks became

3. Mid Ocean Ridge

4. Mid-Ocean Ridge

6. Sea Floor Spreading Harry Hess suggested the Mid-Ocean Ridge was a rift. Magma wells up forming new ocean floor pushing the old floor further away Hypothesis: If the ocean floor is moving then so must the continents be moving Hess found the mechanism Wegener had been looking for.

7. Sea-Floor Spreading

8. Magnetic Reversal Paleomagnetism is when magma cools and hardens into rock and the magnetic orientation becomes permanent. Scientist found that the Earth has reversed its magnetic field. North becomes South; and South becomes North Scientist discovered that rocks of the same age had the same polarity. Scientist discovered a pattern of alternating polarity among rocks called Geomagnetic reversal time scale.

9. Magnetic Symmetry Discovered on either side of the Mid-Ocean Ridge identical pattern of magnetic reversal. Using this data and geomagnetic reversal time scale were able to date the ocean floor. Found the age of the sea floor was also symmetrical. The further from the Mid-Ocean Ridge on either side the older the rocks became This further supported Hess’s Theory of Sea Floor Spreading

10. Magnetic Reversal

11. Wegener Redeemed Scientist found the same magnetic reversal on Land as on the Ocean Floor Scientist reasoned that Sea Floor Spreading was the missing mechanism that forced the continents to move. Wegener’s idea of Continental Drift becomes the Theory of Plate Tectonics.

12. Tectonic Plate Boundaries

13. Plate Boundaries

14. Divergent Plate Boundaries

15. Convergent Plate Boundaries

16. Transformed Plate Boundaries