Geology Reference
In-Depth Information
Many of the mid-ocean ridges also have a rift valley. A
rift valley
is created as the two
plates pull apart and the freshly created, cooling rocks between them are stretched until
they
fault
(break) and drop down, creating a valley. This process is illustrated in Figure
9-2.
Figure 9-2:
Character-istics of
a mid-ocean ridge
and rift valley.
The seafloor spreading that occurs along oceanic divergent boundaries, or mid-ocean
ridges, creates new seafloor and builds oceanic crust. (I describe this process in
Chapter 10 as well.)
Parting the Red Sea
In some areas of the world, divergent boundaries occur where continental plates are
moving apart instead of oceanic plates. It is common for continental divergent boundar-
ies to begin as a
triple junction,
where the crust splits apart in three directions.
In most triple junctions, evidence shows that only two of the cracks continue to separ-
ate. For example, in Figure 9-3 the triple junction between the Arabian Plate and two
parts of the African Plate is illustrated.
Figure 9-3:
A re-
gion of active rift-
ing around the Ar-
abian Peninsula
and Africa.
