Review of some points from last Thursday
D”
Chemical and physical (mechanical) layers in the Earth’s crust
P-waves
3 types of plate boundaries
1) 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
3) Transform- continental-continental crust (e.g., San Andreas Fault)- oceanic-oceanic crust (e.g., faults perpendicular to MOR)
Augustine
Iceland: a mid-ocean rift above water!1: divergent plate boundary
Krafla, 1980
Thingvellir: site of first parliament in 930 A.D.
Iceland: a mid-ocean rift above water!1: divergent plate boundary
3 types of plate boundaries
2: convergent plate boundary
subduction zone
a) ocean-continent
Examples of ocean-continent subduction zone products
Mt. St. Helens (January, 23, 2006 – Dave Sherrod, USGS) Mt. St. Helens,
spring 1980
Cascades volcanism
East
Depth of Earthquakes in subduction zones
Cross-section through Japan area
depth
200 km
400 km
Pacifi
c Plat
e
EurasiaPlate
200 km400 km 0 km
West
Limestonein the Andes
In addition to subduction and volcanism there can be uplift of crust due to convergent plate motion
2: convergent plate boundary (continued)
S NIndia Tibetan
Plateau
Mt. Everest
b) continent-continent
3 types of plate boundaries2: convergent plate boundary
c) ocean-ocean
Augustine
ocean-continent
Aleuts Arc
Augustine Volcano
January 29, 2006 January 30, 2006
3.) Transform Boundary (Strike Slip Faults)