1. Chapter 7 Plate Tectonics

2. Unit essential questions
How do we know that plates move?
How is the Earth’s surface shape by plate motion?
Why do earthquakes and volcanoes occur?

3. What is happening now
S. America is moving away from Africa 2 to 3 cm/year
Hawaii is moving northwest at rate of 8 to 9 cm/year
Mt. Everest is slowly rising

5. Alfred Wegener
A German scientist, geophysicist, and meteorologist in early 1900’s
Continental drift = Earth’s continents had once been joined as a single landmass (Pangea), and slowly drifted away from one another, like gigantic puzzle pieces
Analyzed rock type, geological structures and fossils at the “edges” of the puzzle pieces

6. Today Pangea puzzle piece activity
Take notes on evidence that continents move (p. 218 – 220). Use the following table to organize your notes. You should have about 4 – 5 points per evidence.
3. Questions 1 – 8 on page 222
Climate clues
Fossil clues
Rock clues

7. Chapter 7.2 Development of a Theory

8. Continental drift

9. Evidence Rock Fossils Climate
Appalachian mountains in US share similar rock in Greenland and Europe
Land dwelling reptile Lystrosaurus and Cynognathus – weak swimmers, could not have swum large distances
Mesosaurs (aquatic reptile) found only in fresh water so likely did not cross the ocean
Glossopteris (fern) seeds could not have travelled far
Glacial deposits in South America, Africa, India and Australia – this area was once near the south pole

10. A rejected hypothesis
Many people did not believe Wegener that plates moved
Why?
Could not explain how it moved
Could not explain what forces move continents
Later accepted in the early 1960s, 30 years after his death

11. Seafloor spreading
Process by which new oceanic crust forms along mid ocean ridge and older crust moves away from the ridge
If the sea floor spreads, continents must be moving
Determine the age of the rock across the sea floor
Continents are “passengers “that ride with ocean crust as it slowly moves away from ocean ridges

12. 7.3 The theory of plate tectonics
Quiz on chapter 7 next class.

13. Seafloor spreading
Process by which new oceanic crust forms along mid ocean ridge and older crust moves away from the ridge
If the sea floor spreads, continents must be moving
Determine the age of the rock across the sea floor
Continents are “passengers “that ride with ocean crust as it slowly moves away from ocean ridges

14. Plate tectonics
Earth’s surface is made of rigid slabs of rock, or plates, that move with respect to one another
Lithosphere – Earth’s outermost layer
Asthenosphere – plastic material beneath lithosphere

15. Why or how do continents move?
Convection current = circulation of materials caused by differences in temperature and density
Hot air rises while dense, cold air sinks

17. Plate Boundaries Divergent plate boundary = two plates separate
Transform plate boundary = two plates slide past each other
Convergent plate boundary = two plates collide
Dense plate sinks below the more buoyant plate in a process known as subduction

18. Today
Try the oreo cookies and plate tectonics. You do not need to answer the questions.
On page 243, answer questions 13 – 23