3. Continental Drift Alfred Wegener proposed theory in 1912 that the continents had moved. All the continents were once one big continent and moved apart. Evidence included jigsaw fit of continents, fossils, rocks and continuation of geologic features.

4. Alfred Wegener Meteorologist

13. Mechanism of movement of continents wrong.

14. Unexplained Observations Volcanoes occur on edges of continents and rim of Pacific Ocean Mountain range extending around the world (40,000 miles) capped by a grand canyon-like valley. Deep ocean trenches along volcanic mountain chains.

17. Why mountain ranges are located where they are and why there are different types of mountain ranges. Seismologists observe earthquakes occur in a line and deep earthquakes occur along inclined planes.

18. 20th Century Technology Breakthroughs Radiometric Dating Fathometer (echo sounder) WWII Hess measured m-Ar and guyots, led to conclusion that ocean crust pulling apart and new sea floor was created by volcanic eruptions. Magnetometer and drilling ships

19. Sea Floor Spreading Dietz-new crust formation SFS Paleomagnetism~ magnetic bands occur in pairs on both sides of plate boundaries (Vine and Matthews) Younger rocks found closer to spreading centers (s.c.), age increases as distance increases away from s.c. (drillships)

27. Plate Tectonics “construction” Study of the formation and movement of plates Crust is divided into a dozen major plates & many other smaller plates Each plate is moving relative to the other plates creating Earth’s surface features ~ mountains, trenches & volcanoes

31. Thickness of Plates Crust and upper mantle make up the lithosphere ~~ 100 Km thick Most of lithosphere is made of basalt~~ oceanic, thin, 2.9 g / cm 3 Continental crust made of granite material ~~ thicker, 2.7 g / cm 3

34. Plate Boundaries Diverging Boundaries- spreading centers where plates are moving apart. Location of mid-ocean ridges, rift valleys and fracture zones Examples ~~ mid-Atlantic Ridge and East Pacific Rise, East African Rift

42. Converging Boundaries 2 plates move toward each other Three Types Subduction 1)Ocean-continent 2)Ocean- Ocean Collision 3)Continent-Cont

44. Subduction Boundary oceanic plate collides with continental plate or two ocean plates collide with each other Oceanic plate denser/ subducts under continental plate Trenches bordered by volcanoes and mountain chains, earthquakes deeper, lithosphere destroyed

52. Collision Boundary - Collision of two continents. Examples: Himalayas - India and Asia Ural- North America and Europe Appalachians - NA and Africa

56. Sliding Boundaries Two plates are moving past one another Example ~~ San Andreas Fault Pacific Plate moving NW relative to the North American Plate

60. Plate Movement Lithosphere rests on the asthenosphere ~ a layer in the mantle Rocks in the asthenosphere are partially melted and flow slowly Convection currents rising and sinking push the plates apart and pull them together

65. Craton Continent cores that are the oldest and most deformed rocks on cont. North American craton where exposed is called the Canadian Shield, rest is below surface The N.A. craton shows the shape of continent approximately 2.5 bya Continent has grown since

67. Sources of Growth Material Deep-sea sediments - scraped off during subduction of oceanic plate Volcanic Rock- volcanism associated with subduction Deposition of sediments by rivers Thin-Skinned Thrusting - pushing of thin, horizontal sheets of rock onto continental margins

68. Terranes - a block of lithospheric plate that has been moved a great distance and attached to continent Identification of Terranes bounded on all sides by faults rocks and fossils do not match with neighboring terranes magnetic polarity does not match Ex. Cache Creek terrane BC Canada