1. Continental Drift

2. Note the Shapes South America & Africa: They Match! What about any others? North America?

3. Continental Drift: The Idea that the continents move around and change locations on Earth. Alfred Wegener proposed the idea of Continental Drift The globe before and after continental separation By Antonio Snider-Pellegrini, 1858 (pre-Wegener)

4. “Continental Drift” Evidence: Fossils

5. Animal and plant fossils are located on continents that a currently do not touch These continents must have touched at some time for matching fossils to be found in the in the areas shown on the continents

6. “Continental Drift” Evidence: Glacial Markings Marks where glaciers used to scrape along the surface are found on continents that must have once touched Some of these continents are in areas currently too warm to support glacier devlopment These continents must once have been in colder regions

7. “Continental Drift” Evidence: Glacial Markings

8. “Continental Drift” Evidence: Mountain Belts Mountain belts and rock types connect across continents Some matching mountain belts and rock types are found on continents that no longer touch These continents must have touched at some time

9. “Continental Drift” Evidence: Mountain Belts

10. Moving Continents…Back in time…

11. Pangaea 250 million years ago, the continents fit together like a jigsaw puzzle!

12. ● The Continents Move Around on Earth ● Evidence for Continental Drift: Shape of the Continents Fossils Glacial Markings Mountain Belts ● Pangaea existed when all the continents were together Conclusions

13. Part 1: The Creation of New Oceanic Crust Seafloor Spreading

14. Oceanic plates move apart at mid-ocean ridges. Magma moves into the rift. The magma cools and becomes new ocean floor. The new material magnetizes based on the Earth’s magnetic field at the time. The new material moves away from the ridge. More magma moves into the rift and the cycle continues

15. Age and Magnetic Field recorded in the seafloor and spread to each side of the ridge Each side of the ridge is the same!!

16. Determining Seafloor Age

17. ● Continents > 4 Billion Years Old ● Seafloor < 200 Million Years Old AGE continent ocean Seafloor Age

18. AGE Age distribution The colors represent different ages The youngest crust is nearest the ridge The pattern is symmetric The pattern is more obvious in the Atlantic ocean, where spreading has been very even

19. ● The ocean is much younger than the continents. Continents: 4 Billion years Oceans: <200 Million years ● Seafloor ages make a mirror image (symmetric) pattern. Conclusions