2. Plate Tectonics Ch 8 I. Plate Tectonics - study of the movement of the plates of the Earth’s surface A. Lithosphere - crust & upper mantle broken into plates that can move ocean plates are made of Basalt continent plates are made of Granite http://www.brainpop.com/science/earth/platetectonics/index.asp http://www.brainpop.com/science/earth/platetectonics/index.asp

4. -layer below the lithosphere; -part of the mantle that has partially melted rock enabling plates to slide over each other B. Asthenosphere

5. II. Evidence for Plate Tectonics 1. Similarities in the shapes of the continents, they look like puzzle pieces 2. Fossil remains of Mesosaurus are only found in Brazil, South America & in South Africa 3. Specific rocks coincide on Africa & South America where they seem to fit

6. Fossils of Pangaea

7. A. Alfred Wegener Proposed theory of continental drift Noted the evidence for continental drift which eventually developed into the theory of plate tectonics

8. Areas where plates come together or move apart Belts where earthquakes& volcanoes occur Largest belt is called the Pacific Ring of Fire III. Plate boundaries

9. Ring of Fire

10. 3 Types of Plate Boundaries 1. Converging Plate Boundaries – come together 2. Diverging Plate Boundaries – move apart 3. Transform Plate Boundaries - sliding http://www.pbs.org/wnet/savageearth/animations/hellscrust/index.html

11. A.Converging Boundaries (coming together) a. Collision b. Subduction

12. 1. Collision - two continental plates coming together forming a mountain chain (C-C) a. Himalayas - formed from India & Eurasia crashing together

13. b. Ural Mountains - formed 300 million yrs. ago by a collision between Europe & Asia c. Southern Appalachians -formed by a collision between North America & Africa

14. 2. Subduction Oceanic plate being pushed beneath another oceanic plate or a continental plate; (O-O or O- C) a. O-O subduction results in a trench & island arc

16. Subduction Ex. Ex. #1. Pacific Plate under the Philippine Plate: forms the Mariana Trench & Mariana Islands #2 Pacific Plate under the Eurasian Plate: forms the Aleutian Trench & Aleutian Islands

17. b. O-C subduction Results in trench & coastal, continental mountains Ex. #1Nazca Plate under the South American Plate: forms Peru-Chile Trench & the Andes Mountains

18. O-C Subduction

19. #2 Juan de Fuca Plate under the North American Plate Forms Cascadian Trench, Mt. St. Helens & the Cascade Mountain Range http://bcove.me/s3bmueq3

20. Mt. St. Helens Land Sat Photos Before & After

21. What is left of the trees @ Mt. St. Helens

22. Remains of tress floating on Spirit Lake on the slopes of Mt. St. Helens

23. B. Diverging Boundaries (moving apart) youngest rock is on the rift zone Rock is older the further away it is from the rift in the plates

24. Examples of Divergent Plate Boundaries http://geology.wr.usgs.gov/docs/parks/animate/A49.gif http://geology.wr.usgs.gov/docs/parks/animate/A49.gif Mid Atlantic Ridge 1. Mid Atlantic Ridge - N. American & Eurasian Plates are parting; Iceland East Pacific Rise 2. East Pacific Rise - Pacific & Nazca Plates are parting

25. C. Sliding Boundaries (transform) 1. N. American & Pacific Plates: forming the San Andreas Fault in CA

26. IV. Craton - continent core; oldest & most altered rock of continent 3 Sources of Material Added to the Continents - Sediments deposited by rivers - Volcanic Rock added during eruptions - Terrane- Deep sea sediments at O-C plate boundaries ocean sediments scraped off & left behind to become part of the continent at subduction zones

27. V. Harry Hess Princeton University Theory of Sea Floor Spreading Hot, less-dense material in the mantle is forced upward to the surface at a mid-ocean ridge The sea floor is carried away from the ridge as the new material flows sideways out of the rift The new sea floor cools, becomes more dense than the layer below it & sinks a bit to form a trench

28. Evidence for Sea Floor Spreading 1. Age Evidence - rocks at the mid-ocean ridges are younger than the rocks further from the rift 2. Magnetic Clues - in iron bearing basalt rock of ocean floors; sea floor rocks show many magnetic reversals; magnetic alignment of rocks flip flops back & forth parallel to the mid-ocean ridges http://geology.wr.usgs.gov/docs/parks/animate/A47.gif http://earthsci.terc.edu/content/visualizations/es0803/es0803page01.cfm?chapter_n o=visualization

30. Sea Floor Spreading

31. VI Causes of Plate Tectonics A. Convection Currents - the cycle of heat rising, cooling & sinking B. Differences in rock density; more dense rock sinks (ocean floor)