1. Chapter 5 Earth and its Moon

2. The Earth

3. Table 5-1 Some Properties of Earth and the Moon

4. Figure 5.1 Earth and Moon

5. Earth Structure Inner core Outer core Mantle Crust Hydrosphere Atmosphere Magnetosphere

6. Tides Variation in ocean level Two high tides daily Two low tides daily Vary from several cm to several m Tidal force is differential force

7. Figure 5.2 - Lunar Tides

8. Figure 5.3 - Solar and Lunar Tides

9. Tidal locking Moon keeps same face toward earth Revolves and rotates in 27.3 d Synchronous orbit

10. Figure 5.4 - Tidal Locking

11. Tidal bulge drag Slows rotation of earth Day was 21 hours 500 million years ago Year was 410 days long Eventually moon’s revolution will be synchronized with earth’s rotation

12. Figure 5.5 - Earth’s Atmosphere

13. Earth’s atmosphere Troposphere Stratosphere Mesosphere Ionosphere

14. Convection Warm air rises Cold air falls Happens in troposphere Winds and weather

15. Figure 5.6 - Convection

16. Earth’s temperature Absorbs sunlight Re-radiates energy Average temperature -23°C without atmosphere All water frozen

17. Greenhouse effect Carbon dioxide and water vapor trap radiated infrared radiation Raises average temperature 40 K Above freezing point of water

18. Figure 5.7 Greenhouse Effect

19. Ozone layer Straddles stratosphere and mesosphere Ozone is 3 oxygen atoms per molecule Protects life from damaging UV Man-made chlorofluorocarbons (CFCs) CFCs release chlorine Chlorine attacks Ozone

20. Discovery 5-1 Earth’s Growing Ozone Hole

21. Discovery 5-2a The Greenhouse Effect and Global Warming

22. Discovery 5-2b The Greenhouse Effect and Global Warming

23. No lunar atmosphere Moon’s gravity too weak to hold atmosphere No atmosphere to moderate temperature 100 K to 400 K fluctuations Some water ice at lunar poles

24. Earth’s interior Seismic (earthquake) waves P-waves and S-waves Outer core liquid (thick) Inner core solid Core is iron and nickel

25. Figure 5.8 P- and S-waves

26. Figure 5.9 Seismic Waves

27. Differentiation Variation in composition and density between mantle and core Earth was molten in past Early bombardment Nuclear radioactivity

28. Figure 5.10 Earth’s Interior

29. Moon Structure Core Soft asthenosphere Solid rocky lithosphere Crust No hydrosphere, atmosphere, magnetosphere Uniform density Chemically differentiated

30. Figure 5.11 Global Plates

31. Plate tectonics Surface composed of plates Drift several cm per year Earthquakes Continental drift Mountain building Ocean ridges Driven by convection in mantle

32. Figure 5.12 Himalayas

33. Figure 5.13 Californian Fault

34. Figure 5.14 Plate Drift

35. Figure 5.15 Pangaea

36. Surface of moon No plate tectonics No air or water causing erosion No ongoing volcanic activity

37. Figure 5.16 Full Moon, Near Side

38. Lunar features Maria (singular mare) Highlands Craters

39. Figure 5.17 Full Moon, Far Side

40. Lunar maria Means “seas” (don’t contain water) Roughly circular Dark Flat plains from spread of lava Basaltic 3300 kg/m 3 Mantle material 3.2 to 3.9 billion years old

41. Figure 5.18 Moon, Close-up

42. Lunar highlands Several km above maria Lighter colored Rich in aluminum 2900 kg/m 3 More than 4 billion years old

43. Lunar cratering Formed long ago by meteoritic impact Fast moving object (several km/s) Tremendous impact energy Pushes flat material up and out Forms crater Ejecta blanket

44. Figure 5.19 Meteoroid Impact

45. Cratering rate Older highlands have more craters Younger maria have less craters Meteoritic bombardment rate dropped 3.9 billion years ago End of accretion process in which planetesimals became planets Roughly constant rate since then

46. Figure 5.20 Lunar Craters

47. Figure 5.21 Lunar Surface

48. Lunar erosion 10 km crater every 10 million years 1 m crater per month 1 cm crater every several minutes Accumulated dust from impacts (lunar regolith) averages 20 m deep Deepest on highlands Shallowest on maria

49. Earth’s magnetic field Earth acts as if it contains a giant magnet Creates magnetic field in and around earth Compasses respond to this magnetic field North and south magnetic poles roughly aligned with the earth’s rotation axis Magnetic N is 13.5° E of true N in LB Caused by charged particles in earth’s molten metallic core

50. Magnetosphere Region in space around a planet influenced by planet’s magnetic field Buffer zone between planet and high energy particles of solar wind

51. Figure 5.22 Earth’s Magnetosphere

52. Magnetism and particles Magnetism does not affect neutral particles and electromagnetic radiation Charged particles can be trapped by magnetic field Electrons and protons spiral around field lines

53. Van Allen belts Discovered in the 1950’s Charged particles in solar wind trapped in doughnut shaped regions Inner belt mostly protons, 3000 km above earth’s surface Outer belt mostly electrons, 20,000 km above earth’s surface

54. Figure 5.23 Van Allen Belts

55. Aurora Some charged particles escape from Van Allen belts above north and south poles Collide with air molecules and create light show Aurora borealis or Northern Lights Aurora australis or Southern Lights

56. Figure 5.24 Aurora Borealis

57. No lunar magnetism Moon rotates slowly No molten or metal rich core

58. Earth-moon formation Earth formed about 4.6 billion years ago Moon probably formed by a collision of Mars sized object with earth Iron core left behind, moon made of mantle type material

59. Figure 5.25 Moon Formation

60. Earth evolution During molten phase, earth became differentiated in density and chemistry Intense meteoritic bombardment ended 3.9 billion years ago Surface cooled first, developing crust Core is still partially molten

61. Lunar evolution Oldest rocks in lunar highlands 4.4 billion years old Early meteoritic bombardment kept surface layers molten Moon cooled more quickly than earth After bombardment, lunar crust and basins remained 3.9 to 3.2 billion years ago basins flooded with basaltic flow - these became maria

62. Figure 5.26 Lunar Evolution

63. Far side of moon Earth’s gravity formed thicker lunar crust on far side of moon than on near side Near side had substantial volcanic activity Far side had little substantial activity

64. Figure 5.27 Large Lunar Crater

65. Large impact crater Some large basins caused by impact didn’t flood with lava