Chapter 17 Plate Tectonics Section 17.1 Drifting Continents

Vocabulary Continental Drift: Fossil: Pangaea: The hypothesis that the continents slowly move across Earth’s surface. Fossil: A trace of an ancient organism that has been preserved in rock. Pangaea: The name of the single landmass that broke apart 200 million years ago and gave rise today’s continents.

The Theory of Continental Drift State Alfred Wegener’s hypothesis about how Earth’s continents have moved. Wegener’s hypothesis was that all the continents had once been joined together in a single landmass and have since drifted apart. Wegener named his supercontinent ________. Pangaea

The Theory of Continental Drift

The Theory of Continental Drift What did Wegener think had happened to this supercontinent? Wegener thought that this supercontinent had broken apart and that the pieces had slowly moved to become the continents as they are today. Wegener’s idea that the continents slowly moved over Earth’s surface became known as ____________. continental drift

The Theory of Continental Drift Complete the concept map. Continental drift Is supported by evidence from Landforms Climate Fossils

The Theory of Continental Drift Give an example of evidence from landforms that supported Wegener’s idea of continental drift. An example is mountains in South Africa that line up with mountains in Argentina or coal fields in Europe that match up with coal fields in North America. Any trace of an ancient organism preserved in rock is called a(n) ________. fossil

The Theory of Continental Drift How did Wegener explain similar fossils on different continents? Wegener explained it as evidence that the continents had once been united. True or False: Wegener believed that Earth’s climate had changed. False

Scientist’s Reject Wegener’s Theory How did Wegener think that mountains formed? Wegener thought they formed when drifting continents collided, causing their edges to crumple and fold. How do the locations of mountains support Wegener’s ideas how mountains form? Mountains usually occur in narrow bands along the edges of continents, as you would expect if the collision of continents forms mountains.