The Structure of the Earth and Plate Tectonics

1. The Structure of the Earth and Plate Tectonics

2. Lesson Objectives This lesson will teach you everything you need to know about the Structure of the Earth and Plate Tectonics. By the end of this lesson you will be able to… Name and describe Earth’s main layers. Name and describe three types of plate boundaries

3. Instructions • Complete this lesson on your own and at your own pace. • Use the navigational buttons along the bottom to move throughout the lesson. • Take notes as you go.The objectives (on the previous page) will be assessed by practice quizzes and on our Chapter Test. • After linking to a website, simply close your browser window to return to this lesson. • Have a pencil & paper handy. • Have fun!

4. Structure of the Earth • The Earth is made up of 4 main layers: • Inner Core • Outer Core • Mantle • Crust Mantle Outer core Inner core Crust

5. Structure of the Earth The inner core is a primarily solid sphere about 1220 km in radius situated at Earth's center. Based on the abundance of chemical elements in the solar system, their physical properties, and other chemical constraints regarding the remainder of Earth's volume, the inner core is believed to be composed primarily of a nickel-iron alloy, with small amounts of some unknown elements. Working from the center of the Earth out we have:

6. Structure of the Earth The liquid outer core is 2300 km thick and like the inner core composed of a nickel-iron alloy (but with less iron than the solid inner core). Iseismic and other geophysical evidence indicates that the outer core is so hot that the metals are in a liquid state. Working from the center of the Earth out we have:

7. Structure of the Earth The mantle is approximately 2,900 km thick and comprises 70% of Earth's volume. This is the largest layer!! In the mantle, temperatures range between 500-900 degrees Celsius at the upper boundary with the crust to over 4,000 degrees Celsius at the boundary with the core. Working from the center of the Earth out we have:

8. The Crust This is where we live! The Earth’s crust is made of: Continental Crust & Oceanic Crust

9. The Crust Continental Crust Continental crust forms the land (the continents, as the name suggests) that we see today. Continental crust averages about 35 km thick. Under some mountain chains, crustal thickness is approximately twice that thickness (about 70 km thick). Continental crust is less dense and therefore more buoyant than oceanic crust Continental crust contains some of the oldest rocks on Earth.

10. Oceanic Crust As the name already suggests, this crust is below the oceans. Compared to continental crust, Oceanic crust is thin (6-11 km). It is more dense than continental crust and therefore when the two types of crust meet, oceanic crust will sink underneath continental crust. The rocks of the oceanic crust are very young compared with most of the rocks of the continental crust. They are not older than 200 million years. The Crust

11. Checkup Quiz: Review song/video of the layers Move forward when you are ready to test yourself on the knowledge you gained!

12. Which layer is the rigid outer layer of the Earth? Checkup Quiz: Outer core Asthenosphere Inner core Crust Mantle

13. Structure of the Earth • The Earth is made up of 4 main layers: • Inner Core • Outer Core • Mantle • Crust Mantle Outer core Inner core Crust

14. Which layer is the rigid outer layer of the Earth? Crust

15. Which layer of the earth is made of mostly solid metals? Checkup Quiz: Outer core Asthenosphere Inner core Mantle Lithosphere

16. Structure of the Earth Video

17. Which layer of the earth is made of mostly solid metals? Inner core

18. Which layer of the earth is made of mostly liquid metals? Checkup Quiz: Outer core Asthenosphere Inner core Mantle Lithosphere

19. Structure of the Earth Video

20. Which layer of the earth is made of mostly solid metals? Outer core

21. Which layer labeled as #5? Checkup Quiz: Asthenosphere Outer core Inner core Lithosphere Mantle Hint: use the scale on the right of the figure!

22. Structure of the Earth • The Earth is made up of 4 main layers: • Inner Core • Outer Core • Mantle • Crust Mantle Outer core Inner core Crust

23. Which layer labeled as #5? Outer core

24. What is Plate Tectonics?

25. 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.

26. 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.

27. World Plates

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

29. What are tectonic plates made of? • Take a look at both labels for lithosphere. The lithosphere is made up of either type of crust and the upper part of the mantle.

30. What lies beneath the tectonic plates? • Below the lithosphere (which makes up the tectonic plates) is the asthenosphere.

31. Plate Movement • “Plates” of lithosphere are moved around by the underlying hot mantle convection cells

32. Plate Movementonly need the first :35 sec.

33. Plate Movement Continental drift is the movement of the Earth's continents relative to each other. The hypothesis that continents 'drift' was first put forward by Abraham Ortelius in 1596 and was fully developed by Alfred Wegener in 1912.

34. Try to logically piece the continents together so that they form a giant supercontinent. Use the handout in class to use to cut out and paste. Exercise 1: Wegener On the back, explain your reasoning on the evidence.

35. What happens at tectonic plate boundaries?

36. Divergent Convergent Transform Three types of plate boundary

37. Spreading ridges As plates move apart new material is erupted to fill the gap Divergent Boundaries

38. In plate tectonics, a divergent boundary is a linear feature that exists between two tectonic plates that are moving away from each other. These areas can form in the middle of continents or on the ocean floor. As the plates pull apart, hot molten material can rise up this newly formed pathway to the surface - causing volcanic activity. Where a divergent boundary forms on a continent it is called a RIFT or CONTINENTAL RIFT, e.g. African Rift Valley. Where a divergent boundary forms under the ocean it is called an OCEAN RIDGE

39. Age of Oceanic Crust Ocean Ridges: This map shows the age of the oceanic crust. The red coloring shows the youngest ages, whilst the dark blue shows the oldest ages (around 200 million years old). Answer: Divergent boundaries Where are the Ocean Ridges located? Courtesy of www.ngdc.noaa.gov

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

41. Convergent Boundaries • There are three styles of convergent plate boundaries • Continent-continent collision • Continent-oceanic crust collision • Ocean-ocean collision

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

43. Continent-Continent Collision Himalayas

44. Continent-Oceanic Crust Collision • Called SUBDUCTION

45. Continent-Oceanic Crust Collision At a convergent boundary where continental crust pushes against oceanic crust, the oceanic crust which is thinner and more dense than the continental crust, sinks below the continental crust. The oceanic crust descends into the mantle at a rate of centimeters per year Subduction is a way of recycling the oceanic crust. Eventually the subducting slab sinks down into the mantle to be recycled. It is for this reason that the oceanic crust is much younger than the continental crust which is not recycled.

46. Subduction • Oceanic lithosphere subducts underneath the continental lithosphere • Oceanic lithosphere heats and dehydrates as it subsides • The melt rises forming volcanism • E.g. The Andes

47. Ocean-Ocean Plate Collision • 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. • E.g. The Mariana Trench is 11 km deep!

48. Ocean-Ocean Plate Collision The subducting plate is bent downward to form a very deep depression in the ocean floor called a trench.

49. Transform Boundaries • Where plates slide past each other Above: View of the San Andreas transform fault

50. This map summarizes all the known plate boundaries on Earth, showing whether they are divergent, convergent or transform boundaries