Earth's Tectonic Forces Unveiled

1. The Big Crack Up!

2. LEARNING TARGET 4: • Describe plate movements that cause ocean basins, ocean trenches, and mountains to form; • Explain the causes of earthquakes and volcanic eruptions.

3. EARTH: A GIGANTIC RECYCLING CENTER!

4. Plate Tectonics • The theory of plate tectonics is based on the evaluation of scientific evidence and observation- The Scientific Method • Continental Drift hypothesis • Seafloor Spreading hypothesis

5. Plate Boundaries Convergent Divergent Transform

6. Plate Tectonics • Explains the configuration of topographic features of the Earth- mountains, valleys, volcanoes, islands, oceanic trenches, faults

7. Tectonic plates • Are composed of the lithosphere • Move as a coherent mass • May contain oceanic crust and continental crust

8. Plate Boundaries • Where does the energy come from to move plates? • Where does it go? Topographic features on the Earth’s surface reflects what is happening in the mantle.

10. Volcanic arc Oceanic crust subducts under continental crust Melting occurs at about 100 miles down Hot more buoyant material rises Convergent Plate Boundary

11. Volcanic Arc • Oceanic and continental crust • Cascade Range, Andes, Alaska • Characteristics: large volcanoes; subduction zone; trench; oceanic crust subducts under continental crust

12. Convergent Plate Boundary • Map and cross-section views of the subduction zone • The oceanic Juan de Fuca plate subducts under the continental North American Plate

13. Two oceanic crusts Oceanic crust subducts under opposing oceanic crust Oldest oceanic crust subducts Convergent Plate Boundary

14. Island Arc • Japan, Indonesia, Philippines, Caribbean, Aleutian Islands

15. Earthquakes trace the SUBDUCTING SLAB to about 500 miles or 650 kilometers Convergent Plate Boundary Gold dots represent earthquake hypocenters

16. Sketch a cross-section of a convergent plate boundary that contains an oceanic crust. • Label with the following terms: • Subduction zone • Trench • Area of melting • Area of volcanism • Arrows indicating direction of plate movement

17. Convergent Plate Boundaries • Two continental crusts • Neither subduct due to buoyancy of crusts • Mountains form

18. India collided with Asia about 40 million years ago • Mt. Everest, 29,000 feet

19. Divergent Plate Boundary • Two plates move apart • Run through ocean basins

20. Divergent Plate Boundaries New crust forms at mid-oceanic ridges. The seafloor spreads out. This is Seafloor Spreading.

21. In most locations, mid-ocean ridges are 6,500 feet (1,980 m) or more below the surface of the oceans. In a few places, they reach above sea level and form islands. Iceland (North Atlantic), the Azores (west of Portugal), and Tristan de Cunha (south Atlantic between southern Africa and South America)

22. How Does Seafloor Spreading Affect Neighboring Plates?

23. East Africa Rift Zone • Continental crust is beginning to pull-apart forming a rift valley

24. Process of Ocean Basin Formation

25. Sketch a cross section of a divergent plate boundary. • Label with the following terms: • rift valley; • oceanic ridge; • oceanic crust; • location of melting and volcanism; • and arrows indicating direction of plate movement .

26. Transform Plate Boundary

27. Transform Plate Boundary • The tectonic plates pass by each other • Connected to other plate boundaries • San Andreas Fault Label the plates, their movement directions, and the San Andreas Fault

28. HotSpots • Stationary plumes of hot material that initiate at the core/mantle interface • Hawaii: the plume is beneath oceanic crust Animation of Formation

29. Hot Spots

30. Hot Spots • Yellowstone is associated with a hot spot under continental crust

31. Name the landform associated with oceanic crust subducting under continental crust. Oceanic crust?