1. Plate Tectonics

2. A.Structure of Earth’s Interior Earth’s interior consists of three major zones defined by their chemical composition—the Crust, Mantle, and Core. Determined by sending seismic waves through the earth I. EARTH

3. Seismic Waves Paths Through the Earth

4. 1.CRUST Thin, rocky outer layer Varies in thickness - Roughly 7 km in oceanic regions - Continental crust averages 8–40 km - Exceeds 70 km in mountainous regions I. EARTH A. Structure of Earth’s Interior

5. I. EARTH 1. Crust Continental crust - Upper crust composed of granitic rocks - Lower crust is more akin to basalt - Average density is about 2.7 g/cm 3 - Up to 4 billion years old

6. A. Structure of Earth’s Interior I. EARTH 1. Crust Oceanic crust - Basaltic composition - Density about 3.0 g/cm 3 - Younger (180 million years or less) than the continental crust

7. A. Structure of Earth’s Interior I. EARTH 2. Mantle Below crust to a depth of 2900 kilometers Composition of the uppermost mantle is the igneous rock peridotite (changes at greater depths).

8. A. Structure of Earth’s Interior I. EARTH  Lithosphere Crust and uppermost mantle (about 100 km thick) Cool, rigid, solid 2. Mantle

9. I. EARTH  Asthenosphere Beneath the lithosphere Upper mantle To a depth of about 660 kilometers Soft, weak layer that is easily deformed A. Structure of Earth’s Interior

10. 2. Mantle I. EARTH  Lower Mantle 660–2900 km More rigid layer Rocks are very hot and capable of gradual flow. A. Structure of Earth’s Interior

11. I. EARTH 3. CORE Below mantle Sphere with a radius of 3486 kilometers Composed of an iron-nickel alloy Average density of nearly 11 g/cm 3 A. Structure of Earth’s Interior

12. 3. CORE I. EARTH  Inner Core Sphere with a radius of 1216 km Behaves like a solid A. Structure of Earth’s Interior

13. 3. CORE I. EARTH  Outer Core Liquid layer 2270 km thick Convective flow of metallic iron within generates Earth’s magnetic field A. Structure of Earth’s Interior

14. Earth’s Layered Structure

15. 4. Earth’s Composition I. EARTH  Mantle  Crust Early seismic data and drilling technology indicate that the continental crust is mostly made of lighter, granitic rocks. Composition is more speculative. Some of the lava that reaches Earth’s surface comes from asthenosphere within. A. Structure of Earth’s Interior

16. 4. Earth’s Composition I. EARTH  Core Earth’s core is thought to be mainly dense iron and nickel, similar to metallic meteorites. The surrounding mantle is believed to be composed of rocks similar to stony meteorites. A. Structure of Earth’s Interior

17. 4. Earth’s Layers I. EARTH Velocity of seismic waves increases abruptly below 50 km of depth Separates crust from underlying mantle  Moho (Mohorovičić discontinuity) A. Structure of Earth’s Interior

18. 4. Earth’s Layers I. EARTH  Shadow Zone Absence of P waves from about 105 degrees to 140 degrees around the globe from an earthquake Can be explained if Earth contains a core composed of materials unlike the overlying mantle A. Structure of Earth’s Interior

19. Earth’s Interior Showing P and S Wave Paths

20. I. EARTH B. Density  The relationship of mass and volume in an object  Mass per unit volume Or  The concentration of material in a given amount of space  SI Unit: g/ml or g/cm 3 Density = Mass Volume

21. I. EARTH C. Metric System 1.BASE UNITS Gram (g) Liter (l) Meter (m) 2. PREFIXES Kilo (k) = 1,000 Hecto (h) = 100 Deca (da) = 10 King Hector Died, (base) drinking chocolate milk }1 milli (m) = 0.001 centi (c) = 0.01 deci (d) = 0.1

22. A. An Idea Before Its Time II. Theory of Continental Drift 1. Wegener’s continental drift hypothesis stated that the continents had once been joined to form a single supercontinent. a.Wegener proposed the supercontinent, Pangaea b.It began to break apart 200 million years ago and form the present landmasses.

23. Breakup of Pangaea

24. A. An Idea Before Its Time II. Theory of Continental Drift 2. Evidence a. The Continental Puzzle b. Matching Fossils - Fossil evidence for continental drift includes several fossil organisms found on different landmasses.

25. A. An Idea Before Its Time II. Theory of Continental Drift 2. Evidence d. Ancient Climates c. Rock Types and Structures - Rock evidence for continental exists in the form of several mountain belts that end at one coastline, only to reappear on a landmass across the ocean.

26. Matching Mountain Ranges

27. Glacier Evidence

28. B. Rejecting the Hypothesis II. Theory of Continental Drift 1. A New Theory Emerges Wegener could not provide an explanation of exactly what made the continents move. News technology lead to findings which then lead to a new theory called plate tectonics.

29. III. Plate Tectonics  According to the plate tectonics theory, the uppermost mantle, along with the overlying crust, behaves as a strong, rigid layer. This layer is known as the lithosphere. A plate is one of numerous rigid sections of the lithosphere that move as a unit over the material of the asthenosphere.

30. A. Causes of Plate Motion III. Plate Tectonics 1.Types of Heat (energy) Transfer a)Convection – transfer of heat through a fluid b)Conduction – transferred from molecule to molecule by direct contact (solids) c)Radiation – transfer of heat by means of electromagnetic waves (no matter needed)

31. HEAT TRANSFER

32. A. Causes of Plate Motion III. Plate Tectonics 2. Convection a.Takes place in the asthenosphere b.Movement in the fluid caused by the changes in density c.Heating → molecules move further apart → less dense → rise hits ceiling → molecules, closer together → more dense → cools → sinks → continues

33. Mantle Convection Models

35. III. Plate Tectonics B. Plate Boundaries Place where plates meet faults form along these boundaries Plate boundaries are where the plate move and cause earthquakes Ring of Fire

36. III. Plate Tectonics

37. B. Plate Boundaries III. Plate Tectonics 1. Boundary Types a.Divergent boundaries (also called spreading centers) are the place where two plates move apart. Tension Stress b.Convergent boundaries form where two plates move together. Compression Stress c.Transform fault boundaries are margins where two plates grind past each other without the production or destruction of the lithosphere. Shearing Stress

38. Three Types of Plate Boundaries

40. Stress at Plate Boundaries

41. 2. Divergent Boundaries a.Oceanic Ridges and Seafloor Spreading i.Oceanic ridges are continuous elevated zones on the floor of all major ocean basins. The rifts at the crest of ridges represent divergent plate boundaries. III. Plate Tectonics

42. 2. Divergent Boundaries a.Oceanic Ridges and Seafloor Spreading ii. Rift valleys are deep faulted structures found along the axes of divergent plate boundaries. They can develop on the seafloor or on land. iii.Seafloor spreading produces new oceanic lithosphere. III. Plate Tectonics

43. Spreading Center

45. 3. Divergent Boundaries III. Plate Tectonics a. Continental Rifts i. When spreading centers develop within a continent, the landmass may split into two or more smaller segments, forming a rift.

46. East African Rift Valley

47. Convergent Boundaries 9.3 Actions at Plate Boundaries  A subduction zone occurs when one oceanic plate is forced down into the mantle beneath a second plate. Denser oceanic slab sinks into the asthenosphere.  Oceanic-Continental Pockets of magma develop and rise. Continental volcanic arcs form in part by volcanic activity caused by the subduction of oceanic lithosphere beneath a continent. Examples include the Andes, Cascades, and the Sierra Nevadas.

48. Oceanic-Continental Convergent Boundary

49. Convergent Boundaries 9.3 Actions at Plate Boundaries Two oceanic slabs converge and one descends beneath the other.  Oceanic-Oceanic This kind of boundary often forms volcanoes on the ocean floor. Volcanic island arcs form as volcanoes emerge from the sea. Examples include the Aleutian, Mariana, and Tonga islands.

50. Oceanic-Oceanic Convergent Boundary

51. Convergent Boundaries 9.3 Actions at Plate Boundaries When subducting plates contain continental material, two continents collide.  Continental-Continental This kind of boundary can produce new mountain ranges, such as the Himalayas.

52. Continental-Continental Convergent Boundary

53. Collision of India and Asia

54. Transform Fault Boundaries 9.3 Actions at Plate Boundaries  At a transform fault boundary, plates grind past each other without destroying the lithosphere.  Transform faults Most join two segments of a mid-ocean ridge. At the time of formation, they roughly parallel the direction of plate movement. They aid the movement of oceanic crustal material.

55. Transform Fault Boundary

56. Evidence for Plate Tectonics 9.4 Testing Plate Tectonics  Paleomagnetism is the natural remnant magnetism in rock bodies; this permanent magnetization acquired by rock can be used to determine the location of the magnetic poles at the time the rock became magnetized. Normal polarity—when rocks show the same magnetism as the present magnetism field Reverse polarity—when rocks show the opposite magnetism as the present magnetism field

57. Paleomagnetism Preserved in Lava Flows

58. Evidence for Plate Tectonics 9.4 Testing Plate Tectonics  The discovery of strips of alternating polarity, which lie as mirror images across the ocean ridges, is among the strongest evidence of seafloor spreading.

59. Polarity of the Ocean Crust

60. Evidence for Plate Tectonics 9.4 Testing Plate Tectonics  Earthquake Patterns Scientists found a close link between deep-focus earthquakes and ocean trenches. The absence of deep-focus earthquakes along the oceanic ridge system was shown to be consistent with the new theory.

61. Evidence for Plate Tectonics 9.4 Testing Plate Tectonics  Ocean Drilling The data on the ages of seafloor sediment confirmed what the seafloor spreading hypothesis predicted. The youngest oceanic crust is at the ridge crest, and the oldest oceanic crust is at the continental margins.

62. Evidence for Plate Tectonics 9.4 Testing Plate Tectonics  Hot Spots A hot spot is a concentration of heat in the mantle capable of producing magma, which rises to Earth’s surface; The Pacific plate moves over a hot spot, producing the Hawaiian Islands. Hot spot evidence supports that the plates move over the Earth’s surface.

63. Hot Spot

64. Causes of Plate Motion 9.5 Mechanisms of Plate Motion  Slab-Pull and Ridge-Push Ridge-push causes oceanic lithosphere to slide down the sides of the oceanic ridge under the pull of gravity. It may contribute to plate motion. Slab-pull is a mechanism that contributes to plate motion in which cool, dense oceanic crust sinks into the mantle and “pulls” the trailing lithosphere along. It is thought to be the primary downward arm of convective flow in the mantle.

65. Causes of Plate Motion 9.5 Mechanisms of Plate Motion  Mantle Convection The unequal distribution of heat within Earth causes the thermal convection in the mantle that ultimately drives plate motion. Mantle plumes are masses of hotter-than- normal mantle material that ascend toward the surface, where they may lead to igneous activity.

66. Mantle Convection Models