1. Chapter 17 Plate Tectonics
Section 17.1
Drifting Continents

2. 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.

3. 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

4. The Theory of Continental Drift

5. 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

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

7. 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

8. 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

9. 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.