Earth Science Chapter 5

1. Earth Science Chapter 5 Plate Tectonics

2. Big Ideas • Earth’s Interior • Convection and the Mantle • Drifting continents • Sea-floor Spreading • Plate Tectonics

3. Earth’s Interior • How far do you think it is to the center of the Earth?

4. Almost 4,000 miles! • The deepest mine in the world is only 2 miles

5. How do you think scientists know about the center of the Earth?

6. Geologists use 2 main types of evidence to learn about Earth’s interior: • Direct Evidence from rock samples • Indirect evidence from seismic waves

7. Evidence from Rocks • Humans have drilled holes and extracted rock from depths of 12 miles • Blasts from the Earth have brought rocks from 100 ft to the surface

8. Evidence from Seismic Waves • Earthquakes produce seismic waves • The speed of seismic waves and the path they take show the structure of the planet

10. Three main layers • The three main layers of Earth are the crust, mantle, and the core • These layers differ in size, composition, temperature, and pressure

12. Temperature • The first 20 meters beneath Earth’s crust is cool • After this depth, temperature rises 1 degree Celsius per 40 meters • Heat comes from the molten layer and radioactive substances

13. Pressure • The deeper you go, the higher the pressure • This pressure is equal to that of a swimming pool

14. Pressure

15. Lab Skills Activity • Work with a partner, • Read the directions to the Lab Zone Skills Activity • Create the Data Table on page 129

16. Crust • Crust is a layer of rock that forms Earth’s outer skin • Crust includes both dry land and ocean floor • Crust is very thin compared to the other layers of Earth, only 5-70 km thick

17. Crust

18. Crust • The crust beneath the ocean is oceanic crust and usually made of basalt • Continental crust consists of rocks such as granite

19. I was very disappointed in the behavior of some of you on Friday. • That was extremely disrespectful of you to run from the classroom when the bell rang. • You need to remember that I dismiss you and not the bell. • Please take your seat and sit quietly while you wait for class to begin

20. Mantle • The mantle is about 40 km below the surface • It consists of a hot, solid rock • It can be divided into layers • The mantle is about 3000 km thick

21. Mantle

22. Lithosphere • The crust and the uppermost part of the mantle form the lithosphere • It is about 100 km thick • Lithos means “stone” in Greek

23. Lithosphere

24. Asthenosphere • Under increase heat and pressure • Less rigid-soft like tar, but still solid • Asthenes means “weak” in Greek

26. The Lower Mantle • Beneath the asthenosphere the mantle is solid • This material extends to the Earth’s core

27. Lower Mantle

28. The Core • Consists of mostly nickel and iron • Made of two parts, a liquid outer core and solid inner core • Together it is about 3486 km thick

29. Despite extreme pressure, the outer core is molten surrounding a dense, solid inner core • Evidence suggests that the extreme pressure in the inner core will not allow the solid metal to spread and become liquid

30. Core

31. Core and Magnetic field • Scientists think that movements in Earth’s liquid outer core create Earth’s magnetic field. • This magnetism is what attracts a compass’ needle towards north (it aligns with Earth’s magnetic field)

33. Individually • Complete the section 1 assessment on page 131, including the “writing in science” assignment. If you do not complete these in class, they will become your homework and will be due tomorrow.

34. Make a Chart

35. When you complete the chart • Read the sections “Convection Currents”, and “Convection Currents in Earth.” • 1. Define Convection Currents • 2. Explain how convection currents work, using a real example • 3. Create an illustration of a convection current

36. Bellwork • What are the three types of heat transfer and give an example of one that is not in your book!

37. Drifting Continents • http://www.youtube.com/watch?v=WaUk94AdXPA

38. Continental Drift • Prior to Columbus, mapmakers did not know about the new worlds • Shortly after they began to notice how the coastlines of several countries seemed to fit together like a puzzle

40. Continental drift • Early 1900s German Scientist Alfred Wegener made a hypothesis: • All of the continents were once joined together in a single land mass and have since drifted apart.

41. The Origin of Continents and Oceans • Wegener gathered evidence from different scientific fields to support his ideas about continental drift. • He studied land features, fossils, and evidence of climate change

42. Write a Book! • Make your own version of Wegner’s book • Use the same title as he did • Read pages 138-138 about the evidence he found • Create a page for each type of evidence • Explain how the evidence supports his hypothesis and include illustrations if appropriate.

43. The Origin of Continents and Oceans • Page 1: Title • Page 2: Evidence from land features • Page 3: Evidence from fossils • Page 4: Evidence from climate • Page 5: Conclusion

44. WHAT DID YOU FIND?

45. Sea-Floor Spreading • http://www.youtube.com/watch?v=p0dWF_3PYh4

46. Mid Ocean Ridges

47. Mid Ocean Ridge • Curve like seams through Earth’s oceans • Most mountains are under water, except Iceland!

48. Iceland

49. Hess and Sea-floor spreading • Harry Hess in 1960 realized that Wegener was right and the continents were being moved by sea-floor spreading: • The sea floor spreads apart along both sides of a mid-ocean ridge as new crust is added • The ocean floors act like conveyor belts carrying the continents along with them