Geography Reference
In-Depth Information
60
˚
N
30˚N
Pangea
90˚W
60˚W
60˚E ˚E
120˚E
Tethys Sea
Permian
-250 m.y.
30
˚
S
60˚S
Late
Cretaceous
-75 m.y.
Laurasia
Late
Triassic
-210 m.y.
Gondwana
Present
Midoceanic rift
Island-arc trench
Late
Jurassic
-150 m.y.
Figure 13.3
Wegener's Hypothesis of Continental Drift.
Wegener's dates have been revised but were
remarkably prescient.
Adapted with permission from:
Wegener,
The Origin of the Continents and
Oceans,
1914.
At plate boundaries,
tectonic plates
either
diverge
(spread apart),
converge
(come together) or
transform
(slide past one another). In the Atlantic Ocean, the North
American plate is diverging from the Eurasian plate.
Along this plate boundary, new oceanic crust is constantly
being created where the plates diverge. A chain of volca-
noes called the Mid-Atlantic Ridge have formed on the
ocean fl oor.
