Theory of Continental Drift

1. Theory of Continental Drift Unit 1, Section 3

2. Theory of Continental Drift • In 1910, Alfred Wegener hypothesized that all the continents had once been joining together in a single landmass and have since drifted apart

3. Pangea • Means ‘all lands’ • All the continents were connected together as one supercontinent (landmass) • Over 10 million years ago, Pangea began to break apart • Video of Continent Movement

5. Continental Drift • Continental Drift – continents move slowly over Earth’s surface • Examples of Evidence  • Landforms • Fossils • Climate

6. Evidence from Landforms • Landforms on different continents form chains • Examples: • Mountain ranges running from east to west in South Africa line up with a mountain range in Argentina • European coal fields match up with similar fields in North America • The continents fit together like a puzzle

7. Evidence from Fossils • Fossils – any trace of an ancient organism that has been preserved in rock • Fossils of the same species can be found on continents widely separated • Suggests that the continents were once joined

8. Evidence from Climate • Climates suggest the location of a landmass • Evidence of ancient climates suggest that the location of the landmass has not always been the same • Example: • Spitsbergen island lies in the Arctic ocean and is covered in ice but it has fossils of tropical plants that could not have survived in a cold climate • When the plant was alive 200 million years ago, the island must have been closer to the equator

9. Evidence from Climate • Continental Glaciers – thick layers of ice that cover hundreds of thousands of square km • Examples: • South Africa has evidence of an ancient continental glacier but its currently in a location that wouldn’t support a glacier • Therefore, South Africa must have been closer to the pole in ancient times

10. Evidence of Continental Drift • According to Wegener’s theory, the climate has not changed, instead the positions of the continents have changed • As continents move toward the equator, it gets warmer • As continents move toward the poles, it gets colder

11. Scientists reject Wegener’s Theory • Wegener could not provide a satisfactory explanation for the force that pushes and pulls the continents • From our studies, what force pushes and pulls the continents?

12. Questions • What was Wegener’s Theory of Continental Drift? • What were the three types of evidence Wegener used to support his theory? • How did Wegener use evidence based on fossils to support his theory that the continents have moved?

13. Questions • What was the main reason scientists rejected Wegener’s theory of continental drift? • Coal deposits have also been found beneath the ice of Antarctica. But coal only forms in warm swamps. Use Wegener’s theory to explain how coal could be found so near the poles