1. Continental Drift
Chapter 7 Section 1
Pgs

2. Evidence for Continental Drift
Edges of continents fit together like a puzzle

3. Pangaea
Alfred Wegener suggested all continents were jointed in the past.
Hypothesis of continental drift: continents moved slowly to their positions.
Wegener thought the continents were one large land mass called Pangaea, 200 million years ago.

4. A controversial Idea
Wegener’s ideas were not accepted until after he died.
He was unable to explain exactly how the continents drifted apart
He thought they plowed through ocean floor, and were driven by the spin of the earth.
Other scientists did not agree.

5. Fossill Clues Fossils provide evidence for continental drift
Fossils of the reptile Mesosaurus were found in south America and Africa.
The reptile couldn’t live in salt water, so it was concluded that it must have lived on both continents when they were joined.

6. A Widespread Plant
Fossil plant, Glossopteris was found in Africa, Australia, India, South America, and Antarctica.
Because the plant was found in so many areas, the fossils also support Wegener’s theory.

7. Climate Clues Fossils of warm weather plants were found in the arctic.
Evidence of glaciers were found in tropical regions.

8. Rock Clues Similar rock structures are found on different continents.
South America and western Africa have similar rock structures.
Eastern U.S. , Greenland, and Western Europe have similar rock structures.

9. How Could Continents Drift?
Wegener couldn’t explain how, when or why the continents drifted.
Wegener said low density continents plowed through high density ocean floor.
He thought the spin of the earth caused this to happen.
Scientists rejected his reasoning, and also rejected his theory entirely.
After Wegener died more clues were found to support his theory.

10. Questions Chapter 7.1
What are the four clues that provided evidence for Wegener’s theory?
What is continental drift?
What is Pangaea?
What was Wegener’s explanation of how the continents moved?
How did the Mesosaurus help explain continental drift?