1. OC/GEO103 Lecture 5 Earth Structure

2. What’s inside the Earth? Is there really another world at the center? What is the energy for changing surface features?

3. The Earth System

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’s surface is constantly changing How do we know it’s dynamic?? Earthquakes (and tsunamis) Volcanic eruptions Magnetic Field 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

14. Continents vs Oceans

15. Elevated Continents

16. Submerged 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. Major Questions: How are the ocean basins formed? How permanent are these features? What is the age of the ocean floor? What’s the age of the continents? Why are the ocean basins deep and the continents high?

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

20. What’s going on inside the Earth?

21. Early Ideas 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

26. Earth’s Interior is: Too hot! -- melted rock (magma) comes from even shallow depths Heat comes from radioactivity (principally K, U and Th in the mantle) Crushingly high pressure! -- no open spaces!

27. Information about the Earth’s Interior comes from: Volcanoes Seismic Waves (“sound images”) Meteorites

28. Volcanoes Hawaiian “hotspot” etc Windows into the Earth Samples 200km down (e.g., diamonds!)

29. Seismic Waves Sound energy from earthquakes and large explosions is recorded at seismometers distributed around the globe

30. Meteor Crater (Arizona)

31. Willamette Meteorite Found 1902, in West Linn Largest in the U.S.A. Sold and now resides at the American Museum of Natural History, in NYC

39. Dimensions and Boundaries 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.

40. Where does this picture come from? 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

41. 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 Submerged 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. –Composed of highly evolved rocks, like granite, and metamorphic rocks, squeezed and heated under mountain ranges

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. –Composed of basalt (volcanic).

59. Elevated Continents Submerged 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. Water Fills in the Low Areas

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

71. PLATE BOUNDARIES

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

73. 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 :