1. Chapter 7
Plate Tectonics

2. Chap 7, Sec 2 (Restless Continents)
Objectives:
What is continental drift?
How do landforms, fossils, and climate changes show evidence of the changing surface of the Earth?
Explain how sea-floor spreading provides a way for continents to move.

3. Explain how magnetic reversals provide evidence for sea-floor spreading.

4. Tech Terms:
Alfred Wegener –
German scientist whom in the 1900’s hypothesized that the continents had once been a huge landmass which he called Pangaea (“all lands”).

5. continental drift – the slow movement of continents over Earth’s surface. It was a hypothesis, that was tested.
fossil – any trace of an ancient organism that has been preserved in sedimentary rock.

6. BEHIND THE HYPOTHESIS:
THE SCIENTIST
BEHIND THE HYPOTHESIS:
Alfred Wegener

7. 4. mid-ocean ridge – longest chain of mountains extending into all of Earth’s oceans, that curves like the seam of a baseball along the sea floor.

9. 5. sea floor spreading – the process that adds new material to the ocean floor at the mid-ocean ridge. Molten material erupts and spreads out through the valley that runs along the center of the mid-ocean ridge. It then pushes aside the rock that was already there.

10. FURTHER EVIDENCE

11. Wegener used evidence from landforms, fossils, and climate to support his hypothesis.
Wegener’s hypothesis was rejected because he could not provide an explanation for the force that pushes and pulls the continents.

12. It’s all about …
CONVECTION CURRENTS!!!!!!