review of some points from last thursday. d” chemical and physical (mechanical) layers in the...

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)