M A S T E R P A G E
Three Pioneers
3.2a
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1.
In 1912, when Alfred Wegener proposed in print that Earth’s
continents floated on denser and more stable material below, he
was openly ridiculed and even scorned by his colleagues. Not until
several decades later did his ideas receive any acceptance. Today
he stands as the forefather of modern plate tectonics because of his
theory of continental drift. His widely accepted theory of land
displacement holds that Earth’s continents have been in motion
throughout geological time.
Wegener believed that there was once a single supercontinent,
which he called Pangea (or Pangaea). He said that Pangea broke
apart millions of years ago to form two large continents. He called
the one in the northern hemisphere Laurasia and the one in the
southern hemisphere Gondwanaland. After a very long span of
centuries, Wegener said, Laurasia split to form North America,
most of Asia, Greenland, and a large section of Europe.
Gondwanaland became Africa, South America, Australia, India,
and Antarctica. Wegener believed that the land masses drifted for
millions of years before assuming their present shapes and arriving
at their present locations. He was led to this notion by the
congruity he observed in the shorelines of the lands bordering the
Atlantic Ocean and several other kinds of evidence. Further, he
said, the process of continental drift is still going on—the
continents are still on the move.
Alfred Wegener, who was educated to be a meteorologist and an
Arctic climatologist, insisted that his theory was correct because
of the evidence he saw. To support his ideas about continental
drift, Wegener pointed to the similarities in the fossils of the
southern
continents. Fossils of the same sort from ferns and freshwater
reptiles had been found in all of the southern continents. He saw
this as evidence that all the lands south of the equator has once
been part of a single land mass. He argued that such land-based
life forms could never have crossed the thousands of miles of open
ocean that now separate these land masses. His critics scoffed
because the physical model that Wegener proposed to explain the
movement of continents did not fit what was then known about the
physics of the Earth.
For the next 30 years or so, scientists paid little attention to
Wegener’s theory. In the 1960s, however, geologists discovered
that the ocean floors had been spreading, thus influencing the
shapes and sizes of the continents. This new theory, called plate
tectonics, provided a mechanism that made sense in physical terms
to account for Wegener’s idea of continental drift.
Although the continents themselves do not drift, as Wegener
proposed, he was correct in his thesis that Earth’s surface is not
fixed. He was a man well ahead of his time whose insight went
beyond safe and conventional thinking. So important is Wegener
to our current understanding of plate tectonics that in the 1970s a
crater on the dark side of the moon was named for him, to honor
his courage and vision.
Tragically, Alfred Wegener never lived to see his ideas accepted
by the scientific community. He perished while attempting to cross
Greenland from a camp on the ice cap in the winter of 1930. His
purpose was to learn more about atmospheric conditions in the
Arctic in order to better predict world weather patterns.
What title would you give this essay?
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Write a two- or three-sentence summary of the essay, then add a one-sentence comment.
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A G U
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F E M A
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