1. Describe evidence for the mechanism behind continental drift. 1.Describe 1 evidence for continental drift AND how it supports the theory. 2.Why was the theory of continental drift not accepted right away? 02/05/2015

2. Continental Drift All continents were part of a giant landmass called Pangaea that existed 200 million years ago.

4. Wegener’s Evidence for Continental Drift 1.Continents fit together like a puzzle. 2.Fossil correlation 3.Mountain ranges / Rock layers line up 4.Glacier evidence

5. 1. Continents fit together like a puzzle.

6. 2. Fossil Correlation Same fossil found on different continents How did the fossils get from continent to continent?

7. 3. Mountain Ranges and Rock Layers line up

8. 4. Glacier Evidence Glacier residue present in warm climate continents. This suggests that the continents must have moved from a different latitude.

10. So why was Wegener’s theory not accepted at first? No mechanism for moving continents. – i.e. How do the continents move?

11. Harry Hess US geologist and Naval officer (1940s) Gathered more evidence to support the theory of continental drift.

12. Hess’ Evidence 1.Ocean Topography 2.Seafloor Magnetism 3.Seafloor Age

13. What does the ocean floor look like? Page 451 – Read and define… Abyssal Plain Deep-sea Trench Mid-ocean Ridge Page 474 – Read and take notes Ocean-floor Topography

14. Ocean Floor Topography Is the Ocean Floor flat? NO

15. Ocean Floor Topography

16. Abyssal Plains Flat plains of sediments

17. Deep Sea Trenches Elongated depressions Deepest parts of the ocean

20. Mid-Ocean Ridges Underwater mountain ranges

24. Ocean Floor Topography How did these features form?

25. Magnetism Lava contains iron – Iron is magnetic (points to magnetic north) When the lava solidifies, the iron will be “frozen” in the direction of the magnetic north at the time of eruption.

29. Magnetism Direction of the iron at the seafloor is not always the same. The patterns are mirror images on either side of the ridges.

31. Age of the Seafloor

32. Seafloor rocks have different ages. Similar pattern of age on either side of the ridges. Youngest rocks towards the center of the ocean (by the ridges) Oldest rocks closest to the continents