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)