1. Theory of plate tectonics

2. Continental drift hypothesis Before the theory of plate tectonics in the 1960’s, there was Alfred Wegener’s hypothesis of continental drift. Before the theory of plate tectonics in the 1960’s, there was Alfred Wegener’s hypothesis of continental drift. He thought all the continents were once connected to make a single supercontinent called Pangea. He thought all the continents were once connected to make a single supercontinent called Pangea.

3. Pangea 300 million years ago

4. Evidence that supported Pangea

5. Why do the continents move? The theory of plate tectonics states that the Earth’s lithosphere is broken up into plates. These plates continually move and change shape and size. The theory of plate tectonics states that the Earth’s lithosphere is broken up into plates. These plates continually move and change shape and size. When plates move, they cause earthquakes and volcanoes along the plate boundaries. When plates move, they cause earthquakes and volcanoes along the plate boundaries. Plates move slow-on average 5 cm a year! Plates move slow-on average 5 cm a year! Plate motion is caused by convective currents in the asthenosphere Plate motion is caused by convective currents in the asthenosphere

7. Types of plate boundaries Divergent- plates pull apart Divergent- plates pull apart Real life example: atlantic ocean and east african rift valley Real life example: atlantic ocean and east african rift valley Causes: earthquakes, sea floor spreading, rift valleys, and mid ocean ridges Causes: earthquakes, sea floor spreading, rift valleys, and mid ocean ridges

8. divergent Mid ocean ridge Mid ocean ridge East African rift valley East African rift valley

9. Convergent continental continental 2 continents collide-push together 2 continents collide-push together Example: how Appalachian mountains formed and the Himalayan mountains Example: how Appalachian mountains formed and the Himalayan mountains Causes earthquakes and mountains Causes earthquakes and mountains

10. Appalachian mountains form Appalachian mountains form Himalayan mountains Himalayan mountains

11. Convergent oceanic oceanic 2 ocean plates collide-push together 2 ocean plates collide-push together Example: islands of japan, indonesia Example: islands of japan, indonesia Causes: earthquakes, subduction zones, tsunamis, volcanic islands Causes: earthquakes, subduction zones, tsunamis, volcanic islands

13. Convergent oceanic continental An ocean plate and continental plate collide An ocean plate and continental plate collide Examples: Cascade volcanic mountains in northwestern US (Mt st Helens) Examples: Cascade volcanic mountains in northwestern US (Mt st Helens) Causes: earthquakes, volcanic eruptions, tsunamis Causes: earthquakes, volcanic eruptions, tsunamis

15. Transform fault 2 plates slide past each other 2 plates slide past each other Example: San andreas fault in California Example: San andreas fault in California Causes only earthquakes Causes only earthquakes

17. What evidence supports the theory of plate tectonics? Paleomagnetism- alternating layers of rock at the bottom of ocean floors show normal and reverse polarity Paleomagnetism- alternating layers of rock at the bottom of ocean floors show normal and reverse polarity

18. Earthquake patterns

19. Hot spots