2. Continental Drift In 1912, Alfred Wegener developed the theory of continental drift, which states that continents are in constant motion on Earth’s surface.

3. Evidence for Continental Drift Wegener based his hypothesis on several pieces of evidence: 1. Shapes of the Continents look like they fit together like puzzle pieces

4. Fossil Evidence 2. The same types of fossils are found on continents separated by vast oceans Example: Mesosaurus was a freshwater reptile and fossils of it have been found on both South America and Africa. How did it cross the ocean?

5. Geologic Evidence 3. Rocks made of similar materials or mountains formed at the same time are found on continents that are now far apart

6. Climate 4. The continents show evidence that the climate changed. Ex/ fossils of tropical species found in Antarctica means it was once closer to the equator

7. Was Wegener Right? Many scientist did not agree with Wegener because he could not give evidence as to how the continents move In the 1960’s new discoveries led scientists to revise Wegener’s hypothesis. The new theory they came up with is called the Theory of Plate Tectonics.

8. Plate Tectonics The theory of plate tectonics says: Continents do not push their way through the solid rock of the upper mantle, rather the continents are part of plates and the plates slide past or move toward or away from each other. The movement of the plates is caused by convection in the mantle.