Plate tectonics, earthquakes, and the structure of the earth

1. Plate tectonics, earthquakes, and the structure of the earth

2. Goals for the lecture • Students will write and discuss various ideas related to the physical structure of the Earth (9C, 10A, 10B, 10C, 10E, 10F) • Students will write and discuss ideas related to plate tectonics, as well as follow its progression through history(10D)

3. Why does the Earth look like this? • Where did the tectonic plates come from? • They came from the ancient land masses the used to cover the Earth

4. History • Has the Earth always looked like this? • What did the Earth look like in the past?

5. History • What name do we give this place? • Pangea • When was this? • 200 million years ago (mya) • Before there was Pangea, the Earth looked even less like it does today

6. History • About 160 mya, Pangea began to break apart. • Laurasia and Gondwanaland were the dominant land features.

7. History • About 120 mya, Laurasia and Gondwanaland began to break apart. • Continents we might recognize were the result.

8. History • 80 mya, Madagascar breaks off from India as India begins its race across the Indian Ocean.

9. history • 40 mya, Inland seas in the North American Plate and Asian plates drained and India began to push up the Himalayan mountains.

10. Today

11. Fossil Evidence • Organisms have left fossil evidence of their existence on continents across oceans. • Originally thought to be caused by organisms traveling across the ocean on “Rafts.”

12. Fossil Evidence • Other theories suggested organisms crossed over land bridges that were once exposed.

13. Fossil Evidence • A 3rd theory surfaced known as Island stepping stones.

14. Evidence that this is what really happened…

15. Continental drift • Alfred Wegener publishes The Origin of Continents and Oceans in 1915. • Proposes that the continents were once all part of a large landmass called Pangea, and then drifted apart.

16. Continental drift • This idea matured into our current theories of Plate Tectonics • The surface of the earth is divided into about 20 plates.

17. Plate tectonics • All plates contain both continental and oceanic crust. • This is a major departure from continental drift.

18. The theory • Plates are rigid structures and will always move as a distinct unit. • The distance between two points on a tectonic plate will always be the same

19. Lithosphere • The layer of solid rock that surrounds the Earth and a thin layer of molten rock beneath it.

20. asthenosphere • The molten rock beneath the lithosphere.

21. Where do things change? • At the boundaries between plates. • 3 categories • Divergent • Convergent • Transform

22. Divergent

23. Wait no…

24. Divergent boundaries • Occur at oceanic spreading centers, typically called “Mid-Ocean Ridges” • 2 “Plates” are being pulled apart by magma from underneath that is pushing upwards • Process known as Seafloor Spreading

25. Convergent boundaries • 3 classifications of Convergent Boundaries • Oceanic-Continental • Oceanic-Oceanic • Continental-Continental

26. Convergent boundaries • Subduction Zone(vocabulary)- the place where one tectonic plate rides up over another and causes it to be pushed down and recycled (melted)

27. Convergent boundaries • Oceanic-Continental • Result in the formation of Volcanic Arcs along the boundary

28. Convergent boundaries • Oceanic-Oceanic • Result in the formation of Island Arcs • Chains of volcanic islands that form along oceanic plate boundaries

29. Convergent boundaries • Oceanic-Oceanic boundaries will also result in the formation of Trenches • These are places where the ocean is deeper than the surrounding area due to subduction.

30. Convergent boundaries • Continental-Continental • Result in the formation of mountain ranges made from deformed (squeezed) native rock

31. Convergent boundaries

32. Transform boundaries • Plates move in opposing directions on either side of the boundary.