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 below). He thought the continents could cut through the ocean floor.
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.
- 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.
Use the resource below to answer the questions that follow.
- Continental Drift: Planet of Man at http://www.youtube.com/watch?v=bVdrg5ZId1M at (9:47)
- What is uniformatarianism?
- What did Wegener write about in his book?
- What did Wegener think caused continental drift?
- Give specific examples of the response to Wegener's continental drift hypothesis.
- What did scientists learn after the war?
- Describe the continental drift hypothesis.
- Why did scientists reject Wegener’s idea? What was needed for them to accept it?
- What was Wegener's mechanism for drifting continents?