Geology Reference
In-Depth Information
In the early part of the twentieth century, German scientist Alfred Wegener proposed
that all the continents had at one time been connected; they had comprised a single
large continent, a
supercontinent,
called
Pangaea.
He proposed that over a long span of
geologic time, the location of the continents changed as they separated and moved
apart from one another. His idea is known as the
continental drift hypothesis.
Observations of geography, geology, and the location of fossils across the continents
support the idea of an ancient supercontinent. In this section, I describe these various
lines of supporting evidence.
Continental puzzle solving
If you look at a map of the world such as Figure 8-1, you will notice that the eastern
coast of South America and the western coast of Africa have a very similar shape. We-
gener also noticed this fact. He suggested that South America and Africa had once been
connected along these coastlines.
Figure 8-1:
The
continents today.
Early critics argued against this line of evidence, stating that coastal shorelines are con-
stantly changing and pointing out, correctly, that the fit along the coasts of these two
continents was not perfect enough to support Wegener's idea. However, if you include
the
continental shelf,
the portion of the continent that continues from the coast under-
water for a few miles, when you put the continents together, the fit is nearly perfect, as
illustrated in Figure 8-2.
