1. Chapter 4: Plate Tectonics
PowerPoint Review

2. Section 4.1 Earth’s Interior

3. Can you name Earth’s layers?
The crust
The mantle
The outer core
The inner core

4. The Crust Crust - a layer of rock that forms Earth’s outer skin
This includes both dry land and ocean floor
2 Types of Crust
continental crust -the crust that forms the continents (granite)
oceanic crust-the crust beneath the ocean (basalt)

5. The mantle is made of three parts:
Lithosphere - uppermost part of the mantle (rigid, hard layer)
Asthenosphere - some what soft and can bend like plastic
Lower mantle - solid layer beneath the asthenosphere

6. The Core Outer Core Molten metal made of iron and nickel
The movement of the outer core creates Earth’s magnetic field.
Inner Core
A dense ball of solid material made of iron and nickel

7. Travel to Earth’s Interior…Impossible
Heat
Temperature increases 1° C for every 40 meters traveled
Pressure
Pressure increases as you move deeper into Earth’s interior

8. How Do We Know What’s Inside?
Evidence from rock samples
Drilling samples
Volcanic eruptions blast rock to the surface
Evidence from seismic waves
Geologists study how they travel through Earth

9. Layers of the Earth

10. Section 4.2 Convection in the Mantle

11. There are three types of heat transfer: radiation, conduction and convection.

12. Radiation Radiation- the transfer of energy through space
No direct contact with the heat source
Sunlight

13. Conduction
Conduction- heat transfer within a material or between materials that are touching
A metal spoon heats up in a pot of boiling water

14. Convection
Convection - heat transfer by movement within a fluid

15. Let’s take a look at heat transfer.

16. Section 4.3 Drifting Continents

17. Alfred Wegener
Wegener’s hypothesis was that all the continents were once joined in a single landmass and have since drifted apart.
Wegener’s evidence to support continental drift included the puzzle-like fit of the continents, similar mountain ranges, glacial deposits, coal belts, Glossopteris fossils as well as fossils from Mesosaurus and Lystrosaurus.

18. A Theory Rejected
Since Wegener couldn’t explain the force that would move massive continents, his theory wasn’t accepted by the scientific community until after his death.

19. Section 4.4 Sea-Floor Spreading
Old Sea-Floor
New Sea-Floor

20. Mid-Ocean Ridge
Mid-ocean ridge - an undersea mountain chain that is part of a long system of mountains that winds beneath Earth’s oceans.
The ocean floor is mapped using sonar.

21. Evidence of Sea-Floor Spreading
Molten material
Magnetic stripes
Drilling samples

22. How Subduction Happens
Convection currents pull the ocean floor apart at mid-ocean ridges
Magma rises and cools creating new sea-floor.
Gravity pulls old, dense sea-floor down beneath the trench.
Old sea-floor is recycled back into the mantle.
Takes 200 million years!

23. Let’s see it in action.

24. Section 4.5 The Theory of Plate Tectonics

25. Plate Boundaries
There are three kinds of plate boundaries: spreading boundaries, colliding boundaries, and sliding boundaries.

26. Most common type of boundary
Spreading Boundaries
AKA: divergent boundary
Two plates move apart
Ocean: mid-ocean ridge
Land: rift valley
Most common type of boundary

27. Colliding Boundary AKA: convergent boundary
Occurs where two plates collide
Three Types
oceanic/oceanic
oceanic/continental
continental/continental

28. The Himalayas

29. Sliding Boundary AKA: transform boundary
Occurs where two plates move past each other in opposite directions
Crust is neither created nor destroyed
San Andreas Fault

30. The End.