Plate Tectonics

1. Plate Tectonics Earth on the move

2. Lyell’s breakthrough. Uniformitarianism

3. Uniformitarianism (notes) • Uniformitarianism: Only the forces active now, were active in the past. • “ The present is the key to the past” … • Erosion can make a canyon a mile deep if there is enough time. concept developed by Charles Lyell • Leads to the understanding that the Earth is many millions of years old.

4. Cross-Cutting Relationships • Originally developed by James Hutton in Theory of the Earth (1795) and embellished upon by Charles Lyell in Principles of Geology (1830), the principle of cross-cutting relationships states that the geologic feature which cuts another is the younger of the two features.

5. Alfred Wegener’s Evidence for Continental Drift (circa 1915 AD) • The same Fossils of animals and plants in distant continents. • Ancient folded mountains, glaciers and coal deposits become continuous once continents are put back together again • Identical sedimentary rocks found in identical layers at remote regions of the world • Look on page 21 of text.

6. Alfred Wegener’s Theory of Continental Drift • Makes a theory for the continents once having been together in a super-continent called PANGAEA • BUT, he has no mechanism or explanation for what could move the massive continents.

7. −60 °C (−76 °F)

8. Six months later, on May 12, 1931, Wegener's body was found halfway between Eismitte and West camp. It had been buried (by Villumsen) with great care and a pair of skis marked the grave site. Wegener had been fifty years of age and a heavy smoker and it was believed that he had died of heart failure brought on by overexertion. His body was reburied in the same spot by the team that found him and the grave was marked with a large cross., • Published in 1915

9. Where in the world was this animal?

11. What is this?How do we know it existed Mid Atlantic Ridge

12. From Space

13. Paleomagnetism Paleomagnetic info from the sea floor (page 27)

14. Plate Boundaries • We have discovered 3 types of plate movement • All three can cause Earthquakes • Divergent – ( plates moving apart) • mid-ocean ridges, new ocean floor and rift valleys form from these • Convergent (move together)– ocean trenches and most mountains form from these • Transform (or) Strike SlipBoundaries (move side to side) Only form earthquakes.

15. Divergent Boundary Rift Valley

16. Two types of Convergent Plate boundaries • The boundary where the two continental plates meet is called a COLLISIONARY boundary. • Creates Folded mountains and earthquakes

17. Subduction Boundary • A special type of convergent plate boundary • In locations around the world, ocean crust subducts, or slides under, a continental plate. • This creates the geologic features we see below

18. Subduction in Action

19. Transform boundaries –Or A Strike Slip fault (also called a lateral fault), They don’t create or consume crust. Rather, two plates move against each other, building up force, then releasing this force in a sudden and often violent jerk. This sudden jerk creates an earthquake.

21. Earth’s Weather is Created by Convection Cells

22. Convection Cells are what power plate movement.

23. Do you know what’s happening here? Is that happening in this picture as well?