Lecture 3 - How Oceans Form: The African Rift
Monday, January 23, 2012
No required reading for this lecture.
The African Rift from Kenya, Ethiopia, Egypt, Jordan and Israel
Rifts widen into young oceans
Failed rifts are preserved in modern continents from the break up of Pangea
Triple Junctions and Aulacogens
o 3 arms to the rift
o Only 2 of the arms "grow up" and become active
o The third cracks and never develops
o Failed rifts fill up with sediment and contain a lot of oil and gas
The St. Lawrence is sitting right on top of a failed rift
o When they are reactivated, there are intra margin earthquakes
o There are triple junctions all over the world
Mantle plumes in low pressure
o Basalt - iron and magnesium rich rock
Very fluid, like blood
How Oceans Grow
Stage 1: East African Rift
Continent undergoes extension. The crust is thinned and a rift valley forms.
Stage 2: Red Sea
Continent tears in two. Continent edges are faulted and uplifted. Basalt eruptions form oceanic crust.
Stage 3: Atlantic Ocean