1. Plate Tectonics Video Clip of Continental Drift

2. Structure of the Earth The Earth is made up of 3 main layers: –Core –Mantle –Crust Inner core Outer core Mantle Crust

3. The Crust This is where we live! The Earth’s crust is made of: Continental Crust - mostly old -thick (10-70km) - buoyant (less dense than oceanic crust) Oceanic Crust - young - thin (~7 km) - dense (sinks under continental crust)

4. What is Plate Tectonics?

5. Plate Tectonics Theory that the Earths crust is broken into plates that float and move around

6. If you look at a map of the world, you may notice that some of the continents could fit together like pieces of a puzzle.

7. Plate Tectonics The Earth’s crust is divided into 12 major plates which are moved in various directions. This plate motion causes them to collide, pull apart, or scrape against each other. Each type of interaction causes a characteristic set of Earth structures or “tectonic” features. The word, tectonic, refers to the deformation of the crust as a consequence of plate interaction.

8. World Plates

9. What are tectonic plates made of? Plates are made of rigid lithosphere. The lithosphere is made up of the crust and the upper mantle.

10. What lies beneath the tectonic plates? The asthenosphere is part of the mantle, below the lithosphere, where convection currents occur

11. Plate Movement “Plates” of lithosphere are moved around by the underlying hot mantle convection cells Convection currents: magma heats and rises then cools off and sinks back toward the center of the Earth

12. Continental Drift All continents were once connected, then broke apart and drifted slowly to their current location

13. Continental Drift Alfred Wegener, scientist in the 1900’s, came up with the idea of Continental Drift stating that the continents were once a single land mass that drifted apart. Called this supercontinent Pangaea, Greek for “all Earth” 245 Million years ago Split again – Laurasia & Gondwana 180 million years ago

14. Supercontinents Alfred Wagner -German Meteorologist 1912 – proposed hypothesis of continental drift Continents moved slowly to their current locations Evidence of continental drift ● Continents fit like a puzzle ● Fossils ● Plants ● Climate ● Similar Rock layers

15. Evidence of Pangaea

16. What happens at tectonic plate boundaries?

17. Divergent: (divide) Convergent: (come together) Transform: (slide past each other) Three types of plate boundary

18. Different Types of Boundaries

19. 2 plates moving A P A R T As plates move apart new material is erupted to fill the gap Seafloor Spreading Midocean ridges – volcanic islands, Ex. Mid-Atlantic Ridge Rift Valley – makes volcanoes and new land from the rising magma Divergent Boundaries

20. Divergent Boundary - Oceanic http://www.geology.com

21. Divergent Boundary - Continental http://www.geology.com

22. Age of Oceanic Crust Red, Yellow = new crust Blue, Green = old crust Courtesy of www.ngdc.noaa.gov Mid-Atlantic Ridge

23. Iceland has a divergent plate boundary running through its middle Iceland: An example of continental rifting

24. Africa's Great Rift Valley

25. Divergent Boundary – Arabian and African Plates

26. Plates moving together There are three styles of convergent plate boundaries –Continent-continent collision –Continent-oceanic crust collision –Ocean-ocean collision Convergent Boundaries

27. Forms mountains, e.g. European Alps, Himalayas Continent-Continent Collision

28. Convergent Boundary – Indian and Eurasian Plates

29. Convergent Boundaries - Continental-Continental http://pubs.usgs.gov/gip/dynamic/understanding.html & http://www.geology.comhttp://www.geology.com

30. Called SUBDUCTION zone -creates coastal volcanoes Continent-Oceanic Crust Collision

31. Oceanic lithosphere subducts underneath the continental lithosphere Oceanic lithosphere heats and dehydrates as it subsides The melt rises forming volcanism Ex. The Andes, South America Subduction

32. Convergent Boundary – Oceanic & Continental http://pubs.usgs.gov/gip/dynamic/understanding.htmlhttp://pubs.usgs.gov/gip/dynamic/understanding.html & http://www.geology.comhttp://www.geology.com

33. When two oceanic plates collide, one runs over the other which causes it to sink into the mantle forming a subduction zone. The subducting plate is bent downward to form a very deep depression in the ocean floor called a trench. The worlds deepest parts of the ocean are found along trenches. –Ex. The Mariana Trench is 11 km deep! Ocean-Ocean Plate Collision The less dense plate is has areas that get pushed up creating a volcanic island arc. –Ex. The Aleutian Islands, Alaska

34. Convergent Boundary – Oceanic & Oceanic http://pubs.usgs.gov/gip/dynamic/understanding.htmlhttp://pubs.usgs.gov/gip/dynamic/understanding.html & http://www.geology.comhttp://www.geology.com

35. Marianas Trench Aleutian Islands, AK

36. Where plates slide past each other, creating vibration (EARTHQUAKES)‏ Transform Boundaries Above: View of the San Andreas Fault in California

37. Transform Boundary – San Andreas Fault www.geology.com

39. …what’s the connection? Volcanoes and Plate Tectonics…

40. Volcanism is mostly focused at plate margins Pacific Ring of Fire

41. - Subduction - Rifting - Hotspots Volcanoes are formed by:

42. Pacific Ring of Fire Hotspot volcanoes

43. Hot mantle plumes breaching the surface in the middle of a tectonic plate What are Hotspot Volcanoes? Photo: Tom Pfeiffer / www.volcanodiscovery.com The Hawaiian island chain are examples of hotspot volcanoes.

44. The tectonic plate moves over a fixed hotspot forming a chain of volcanoes. The volcanoes get younger from one end to the other.

45. …what’s the connection? Earthquakes and Plate Tectonics…

46. As with volcanoes, earthquakes are not randomly distributed over the globe At the boundaries between plates, friction causes them to stick together. When built up energy causes them to break, earthquakes occur. Figure showing the distribution of earthquakes around the globe

47. Plate Tectonics Summary The Earth is made up of 3 main layers (core, mantle, crust)‏ On the surface of the Earth are tectonic plates that slowly move around the globe Plates are made of crust and upper mantle (lithosphere)‏ There are 2 types of plate There are 3 types of plate boundaries Volcanoes and Earthquakes are closely linked to the margins of the tectonic plates