Download Wegener and The Continental Drift Hypothesis What is continental

Wegener and The Continental Drift Hypothesis
Alfred Wegener
What is continental drift?
Wegener put together a tremendous amount of evidence that the
continents had been joined. He advanced a great idea. But other
scientists didn’t accept it.
Wegener’s Continental Drift Hypothesis
Wegener put his idea and his evidence together in his book, The
Origin of Continents and Oceans. The book was first
published in 1915. He included evidence that the continents had
been joined. New editions of the book containing additional
evidence were published later.
In his book he said that around 300 million years ago, the
continents had all been joined. They created a single landmass he
called Pangaea, meaning “all earth” in ancient Greek. The
supercontinent later broke apart. Since then the continents have
been moving into their current positions. He called his hypothesis
continental drift.
The Problem with the Hypothesis
Wegener had a lot of evidence to support his hypothesis. But he
had a problem. The problem was that he could
not explain how the continents could move through the oceans. He
suggested that continental drift occurred like an
icebreaker plows through sea ice (Figure 1.1). He thought the
continents could cut through the ocean floor.
FIGURE 1.1 An icebreaking ship.
Other scientists didn’t buy his idea. They thought that the
continents would be much more deformed than they are.
Wegener believed that Africa and South America had once been
joined. He had the evidence. But very few scientists
accepted his idea.
He needed a mechanism that they would accept. Alfred Wegener
died in 1930 on an expedition on the Greenland icecap. The
continental drift hypothesis was put to rest for a few decades. It
was when technology could provide even more evidence for
continental drift that scientists looked into the idea again.
Technology also helped scientists to develop a mechanism for how
continents could drift.
Vocabulary
continental drift: Early 20th century hypothesis, made by
AlfredWegener, that the continents move about on Earth’s surface.
Summary
• Alfred Wegener said that the continents had been joined as a
single landmass, which he called Pangaea.
• Wegener thought that Pangaea was together about 300 million
years ago.
• Wegener could not develop a mechanism for continents moving
through oceanic crust that other scientists
would accept.
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