2. The Theory of Continental Drift

3. Continental drift was proposed by Alfred Wegener He used the following ideas to support his theory: 1. The fit of the continents 2. The distribution of fossils 3. Similar sequence of rocks 4. Ancient climates 5. The wandering of the Earth's polar regions Wegener used his observations to hypothesize that all of the present-day continents were once part of a single supercontinent called Pangaea

4. The Fit of the Continents animation

5. Fossils of the same species were found on several different continents. For example, Glossopteris, a fern, was found on the continents of South America, Africa, India, and Australia. If the continents are reassembled into Pangaea, the distribution of Glossopteris can be accounted for over a much smaller area.

6. Distribution of Similar Fossils

7. Continental Drift - Rock Sequences

8. Continental Drift - Glaciation

10. Sea-Floor Spreading In 1962, Harry Hess proposed that new ocean floor is formed at the mid-ocean ridges. The ocean floor is produced by magma that rises from the Earth’s interior. Hess suggested that the ocean floor moved away from the ridge and plunged into an oceanic trench along the continentals.