1. Types of Plate Boundaries (finish Chapter 4) Hot Spots – more evidence for plate tectonics Divergent, Convergent and Transform plate boundaries - some examples California’s complicated tectonic setting – how it defines our local geography

2. Ocean island and seamount chains Most earthquakes and volcanic eruptions occur near plate boundaries – but not all. The Hawaiian Islands are large volcanoes that have formed in the middle of the Pacific Plate. Does this fit into plate tectonic theory? http://pubs.usgs.gov/gip/dynamic/hotspots.html#anchor19620979

3. Hot Spots – places where there has been continuous volcanism for a long period of time – sites of ‘leaks’ or ‘mantle plumes’ They provide measurements of absolute rates of plate motion Subduction zone (crust destroyed) Plates converge (compress) Midocean ridge (crust created) Plates diverge (move apart) younger older Hot spot

4. http://volcano.und.edu/vwdocs/vwlessons/hot_spot_pics/ages_of_islands.gif The hypothesis that islands increase in age with distance from the current hot spot mantle plume is correct

5. Types of Plate Margins Figure 4.17, Skinner et al., 1999 Divergent – new crust is generated where plates pull apart Convergent – crust is consumed in the mantle as one plate dives under another Transform – plates slide horizontally past one another – crust is neither created nor consumed

6. Mid-ocean ridges - divergent margins where new ocean crust is made as plates pull apart Gakkel Ridge Flyby Juan de Fuca Ridge

7. Figure 4.18, Skinner et al., 1999 Mid ocean Ridges

8. Formation of new crust at MOR http://oceanexplorer.noaa.gov/explorations/02fire/background/plumes/media/fig2.html “pillow” lava

9. Mid ocean ridges are also divergent margins http://www.geophysics.rice.edu/plateboundary/age.72.gif Slow spreading rate Fast spreading rate

10. Figure 4.18 Skinner et al., 1999 Formation of Divergent Margins

11. Examples of divergent margins – land being split apart Gulf of California Iceland East African Rift

12. Convergent Margins: Collision Zones Figure 4.24, Skinner et al., 1999

13. Figure 4.20, Skinner et al., 1999 Convergent Margins Features of Subduction Zones

14. Convergent Margin examples

15. http://www.geophysics.rice.edu/plateboundary/aleut1.pdf Convergent Plate Boundary – Aleutian Arc

16. http://www.moorlandschool.co.uk/earth/tectonic.htm

17. 200 million years ago to Present http://www.ucmp.berkeley.edu/geology/tectonics.html

18. http://www.soc.soton.ac.uk/soc_home2.php?pagetype=news3&idx=212 Tectonic setting for Sumatra/Andaman Earthquakes Subduction zone

20. Figure 4.25, Skinner et al., 1999 Transform Margins: The San Andreas Fault

21. http://www.geophysics.ricehttp://www.geophysics.rice. edu/plateboundary/cal1.pdf

22. California’s complex Tectonic Setting http://geography.sierra.cc.ca.us/booth/California/1_lithosphere/plates_west_coast.jpg Volcanoes line up inland of subduction zone Juan de Fuca plate being subducted under North American plate Spreading center – splitting Baja California from Mexico and causing Basin and Range crust expansion California’s big cities are actually on the Pacific plate and moving northwest with it – plate boundary is the San Andreas Fault (a transform fault)

23. http://www2.nature.nps.gov/geology/us gsnps/province/INDEXbasinRangeSUB S.gif

24. http://www.gly.uga.edu/railsback/1121NAWestBasin&Range.jpeg

25. http://geography.sierra.cc.ca.us/booth/California/1_lithosphere/TransRanges_Big.gif