1. Types of Plate Boundaries
Created by Dr. Michael J. Passow

2. Wegener’s “Continental Drift”
Hypothesis: All continents once joined together as supercontinent PANGAEA.
Over millions of years, continents split and moved to present positions (next slide)
Evidence: matching coastlines, fossils, rocks, ancient climates
Weakness: no explanation of continents could move (“driving mechanism”)
Result: rejected for decades

3. http://www. mapsharing

4. Emerging Evidence for Plate Tectonics
Mapping the ocean floors using echo-sounding (sonar) records
Paleomagnetism patterns in ocean basalt
Earthquake epicenter patterns
Volcano locations
Hot Spots (ex., Hawaii and the Emperor Seamounts)
Ocean drilling

5. Continental Drift to Plate Tectonics
By the late 1960s, the many lines of geoscience data obtained through developing technologies all provided evidence that:
1) surface plates existed and
2) they are moving very slowly in three basic patterns

6. Divergent/Convergent/Transform plate boundaries

7. Divergent Boundaries (spreading centers)

8. Continental Rift Valleys
Perhaps the most famous example is the East African Rift Valley. Eventually, a new ocean may form here. (2- 3 million years ago, humans first evolved here.)

9. Convergent Boundaries (subduction zones)

10. Ocean-continent convergent boundaries

11. Most of the Pacific Ring of Fire consists of ocean-continent boundaries

12. Ocean-ocean convergent boundary
Japan

13. Continental-continental convergent boundary
The Himalayas are one of the best examples of this type of boundary.

14. Transform Fault Boundaries

15. http://homepage. ufp. pt/biblioteca/GlossarySaltTectonics/Pages/PageT

16. Continental transform fault: San Andreas system
Most transform faults exist in the ocean floor
One important example on a continent is the San Andrea system

17. Putting It All Together

18. Causes (Driving Mechanisms) for Plate Tectonics
Convection
Slab-Pull and Ridge-Push
Mantle “plumes”
“Whole Mantle” and “Mantle-Core” models