1. Review of some points from last Thursday

2. Chemical and physical (mechanical) layers in the Earth’s crust

3. P-waves

4. 3 types of plate boundaries
Divergent
- mid-ocean ridges (e.g., Mid-Atlantic Ridge: MAR)
- continental rifts (east African Graben)
- 1st continental rift, then mid-ocean ridge (e.g., Red Sea, MAR)
2) Convergent
- ocean-under-continental crust subduction (e.g., Cascades, Alaska)
- continental-under-continental crust subduction (e.g., Himalayas)
- ocean-under-ocean crust subduction (e.g., Aleuts)
- continent-under-ocean crust subduction
Transform
- continental-continental crust (e.g., San Andreas Fault)
- oceanic-oceanic crust (e.g., faults perpendicular to MOR)
Augustine

5. 1: divergent plate boundary
Iceland: a mid-ocean rift above water!

6. Krafla, 1980 1: divergent plate boundary
Iceland: a mid-ocean rift above water!
Thingvellir: site of first
parliament in 930 A.D.

7. 3 types of plate boundaries
2: convergent plate boundary
subduction
zone
a) ocean-continent

8. Examples of ocean-continent subduction zone products
Cascades volcanism
Mt. St. Helens (January, 23, 2006
– Dave Sherrod, USGS)
Mt. St. Helens,
spring 1980

9. Depth of Earthquakes in subduction zones
Cross-section through Japan area
depth
200 km
400 km
Pacific Plate
Eurasia
Plate
0 km
West
East

10. In addition to subduction and volcanism there can be
uplift of crust due to convergent plate motion
Limestone
in the Andes

11. Mt. Everest S N India Tibetan Plateau
2: convergent plate boundary (continued)
Mt. Everest S N
India
Tibetan
Plateau
b) continent-continent

12. 3 types of plate boundaries
2: convergent plate boundary
Augustine
ocean-continent
Aleuts Arc
c) ocean-ocean

13. Augustine Volcano
January 29, 2006
January 30, 2006

14. 3.) Transform Boundary (Strike Slip Faults)