1. BEFORE THE BELL RINGS
Please copy your homework into your assignment book
Please turn your Homework in to the orange basket.

2. Warm-up
Why does the Earth have continents? Have these continents always been here?

3. Monday, November 21, 2016 Warm-up
Continental Drift and Plate Tectonics
Chapter 16.2 Vocabulary
Homework: Section Review Chapter 16.2: 1-5

4. Continental Drift to Plate Tectonics and Earth’s Structure

5. Continental Drift and Alfred Wegener
Wegener's Hypothesis
In 1912, a German scientist named Alfred Wegener proposed a hypothesis that is now called continental drift.
Wegener hypothesized that the continents once formed part of a single landmass called a supercontinent named PANGEA or “One Earth”
Compiled years of evidence on expeditions around the world and died in Greenland.

6. Pangea

7. Evidence for Continental Drift

8. Similar Mountains and Fossils Continents Apart

9. Evidence of Different Climates

10. Wegener’s Theory Rejected
Wegener suggested that the continents plowed through the rock of the ocean floor. However, this idea was shown to be physically impossible.
Wegener couldn’t find any mechanism for how or why plates moved around the globe.
Continental drift ultimately rejected and Wegener died in 1930 while on an expedition in Greenland.

11. But then…! Theory of Plate Tectonics!
In 1947, researchers (Harry Hess) began mapping the ocean floor.
Mid-Ocean ridge discovered and mapped.

12. Mid-Ocean Ridge Discoveries
1.) Sediment thinner at ridge than farther out on either side. What does this mean about the age of rocks at the ridge compared to further toward the continents?
2.) Sediment and rocks are younger at the ridge than further out towards continents.
What does this mean?
New crust is forming at the ridge and moving outward on either side of the ridge suggesting plates move.

15. Magnetic Striping

16. Mechanism Found! Convection Cycles

17. Theory of Plate Tectonics
Theory that explains how and why plates move.

18. Layers of the Earth

19. Layers
Crust-Like the shell of an egg is very thin (roughly 5km thick). Mostly Silica and Oxygen. Very brittle.
Lithosphere: Includes crust and upper mantle. A tectonic plate is made of lithosphere.
Mantle: Dense, hot layer of semi-solid (like liquid plastic) rock. Mostly iron and magnesium. Like the white part of a boiled egg.
Asthenosphere: Makes up lower mantle.
Liquid Outer Core: Spins and makes earth’s magnetic field. Made of iron and nickel.
Solid Inner Core: Made solid by tons of pressure. Extremely hot and made of iron and nickel. Like the yolk of an egg.