1. Exploring the Deep GEO/OC103 Lecture 4: The Structure of the EARTH

2. The Edge of the Sea "Now I hear the sea sounds about me; the night high tide is rising, swirling with a confused rush of waters against the rocks below …. Once this rocky coast beneath me was a plain of sand; then the sea rose and found a new shore line. And again in some shadowy future the surf will have ground these rocks to sand and will have returned the coast to its earlier state. And so in my mind's eye these coastal forms merge and blend in a shifting, kaleidoscopic pattern in which there is no finality, no ultimate and fixed reality - Earth becoming fluid as the sea itself." Rachel Carson, The Edge of the Sea,  1955

4. Atmosphere

5. Hydrosphere Atmosphere

6. Hydrosphere Cryosphere Atmosphere

7. Hydrosphere Cryosphere Biosphere Atmosphere

8. Lithosphere Hydrosphere Cryosphere Biosphere Atmosphere

9. Our Dynamic Earth Earth is incredibly dynamic How do we know it’s dynamic?? Earthquakes Volcanic eruptions Surface Features: –Mountain Ranges; Mid-Ocean Ridges; Deep-Sea Trenches

10. Topography of the Ocean Floor

11. Mid-Ocean Ridge Topography of the Ocean Floor

12. Mid-Ocean Ridge Deep-sea Trench Topography of the Ocean Floor

13. Mid-Ocean Ridge Deep-sea Trench Topography of the Ocean Floor Island Chain

15. Elevated Continents

16. Depressed Ocean Basins

17. Circumference  40,000 km (25,000 miles) Radius  6,300 km (4,000 miles) (1 meter = 1/10,000,000 distance from equator to pole) How Big is the Earth?

18. Questions: How are the ocean basins formed? How permanent are these features? What is the age of the ocean floor? Why are the ocean basins deep and the continents high?

19. The Surface of the Earth 2 levels: –elevated continents –depressed ocean basins What causes these surface features? We must know what goes on inside the Earth

20. Interior of the Earth?

21. Jules Verne

22. “Journey to the Center of the Earth” Entered in Iceland Exited in Italy

23. “Tarzan” “John Carter of Mars” Edgar Rice Burroughs

25. Information about the Earth’s Interior comes from: Meteorites Volcanoes Seismic Waves

26. Meteor Crater (Arizona)

27. Willamette Meteorite Found 1902, in West Linn Largest in the U.S.A. Sold and now resides at the AMNH

28. Volcanoes E.g., Hawaiian “hotspot” Windows into the Earth Samples 200km down

29. Seismic Waves Sound energy from earthquakes and large explosions

37. DEPTHS Top of Mantle – 10 to 70 km (5 to 30 miles) Top of Core – 2,900 km (2000 miles) Center of Earth – 6,300 km (4,000 miles) Mt. Everest  9 km high. Mariana Trench  11 km deep.

38. How do we know what’s inside the Earth?

39. How do we know what’s inside the Earth? Direct Observations: Exposures on Surface Up from  50 km (30 miles) depth Drilling To  15 km (10 miles) Volcanic Material Up from  200 km (120 miles) depth

40. How do we know what’s inside the Earth?

41. How do we know what’s inside the Earth? Indirect Observations: Magnetic Field Iron core. Gravity Field Densities: –Crust: 2 - 3 gm/cm 3 –Mantle: 3.3 - 5.8 gm/cm 3 –Core: 10.8 gm/cm 3 Earthquake Seismic Waves Physical state of crust, mantle, core.

45. LITHOSPHERE –rigid outer shell –crust and upper mantle (~ 50 to 200 km thick) –somewhat brittle, breakable –cold (like butter out of fridge) ASTHENOSPHERE –warmer, plastic layer under lithosphere –mantle from ~ 150 to 700 km –squishy, plastic –warm (like softened butter) LOWER MANTLE –Solid, but can flow over time! –~700 to 2900 km OUTER CORE –liquid INNER CORE –solid Interior of Earth by STRENGTH

47. Elevated Continents Depressed Ocean Basins

48. Swimming Pool

49. Earth’s Mantle

51. Continental Crust Earth’s Mantle

52. Types of Crust Continental Crust

53. Types of Crust Continental Crust – 20 to 70 km (10 to 30 miles) thick.

54. Continental Crust Earth’s Mantle

56. Oceanic Crust

57. Types of Crust Continental Crust – 20 to 70 km (10 to 30 miles) thick. Oceanic Crust

58. Types of Crust Continental Crust – 20 to 70 km (10 to 30 miles) thick. Oceanic Crust – 7 km (4 miles) thick.

59. Elevated Continents Depressed Ocean Basins

62. Thick, Buoyant Continental Crust

63. Thin, Less-Buoyant Oceanic Crust

65. Thick Continental Crust Floats Higher

66. Thin Oceanic Crust Floats Lower

68. Mid-Atlantic Ridge

69. Thick Continental Crust Floats Higher Thin Oceanic Crust Floats Lower

70. Water Fills in the Low Areas

71. And Hides Features on the Ocean Floor! Water Fills in the Low Areas

72. PLATE BOUNDARIES

73. PLATE TECTONICS Tectonics: From the Greek “tecton” builder “architect” The study of large features on Earth’s surface and the processes that formed them.

74. Large features: – continents, mountain ranges – ocean basins and processes: – earthquakes – volcanic eruptions due to movement of plates of Earth’s outer shell. All resulting from mantle convection PLATE TECTONICS :

75. Cracked Egg Shell!