1. Copyright © 2007 Pearson Prentice Hall, Inc. 1 Continental Crust Thicker Less dense Older (up to 4 billion) vs Oceanic Crust Thinner More dense Younger (< 220 Million Figure 13-7

2. Copyright © 2007 Pearson Prentice Hall, Inc. 2 Continental Crust Thicker Less dense Older (up to 4 billion) vs Oceanic Crust Thinner More dense Younger (< 220 Million) Figure 13-7

3. Copyright © 2007 Pearson Prentice Hall, Inc. 3 Continental Crust Thicker Less dense Older (up to 4 billion) vs Oceanic Crust Thinner More dense Younger (< 220 Million) Figure 13-7

4. Nature of the Ocean Floor: Topography Convergent Boundaries = Trenches

5. Nature of the Ocean Floor: Topography Mid Ocean Ridges = Divergent Boundaries

6. Copyright © 2007 Pearson Prentice Hall, Inc. 6 Figure 13-7 Continents grow by collisions Forming mountains at continent-continent convergent boundaries

7. Copyright © 2007 Pearson Prentice Hall, Inc. 7 Continents grow by collisions Forming mountains at continent-continent convergent boundaries Ex. India & Asia

8. Copyright © 2007 Pearson Prentice Hall, Inc. 8 The continents move through time. 225 million years ago they combines into one supercontinert called “Pangea”

9. Copyright © 2007 Pearson Prentice Hall, Inc. 9

10. 10 Cascadia subduction zone http://en.wikipedia.org/wiki/Image:Subduction.jpg

11. Copyright © 2007 Pearson Prentice Hall, Inc. 11 Cascadia subduction zone

12. Copyright © 2007 Pearson Prentice Hall, Inc. 12 http://www.nps.gov/archive/olym/geology/accretion.htm Earth Quakes in the Cascadia subduction zone Note zone with few E.Q.s = locked = potential for very large quake (9.0+)