1. Chapter 12 Earth’s Interior

2. Mount Etna, Italy

3. Earth’s Internal Structure
Earth’s interior is divided into 3 major layers based on chemical composition
Crust, Mantle & Core
These layers are further divided based on physical properties

4. Layers of the Earth

5. Gravity and Layering
The most dense material (iron) sinks to the center of the planet
The least dense material makes up the outer layers

6. Seismic Waves & the Earth’s Interior
We learn about the earth’s interior by studying seismic waves
Velocities of P & S waves vary as they travel through the earth
Travel faster through stiff (rigid) rocks

7. Possible Paths of Seismic Waves

8. The Earth’s Crust Oceanic Crust Forms at mid-ocean ridges
Averages 7 kilometers thick
Comprised of basalt and gabbro
Average density of 3.0 g/cm3

9. The Earth’s Crust Continental Crust Lots of granite
Averages 40 km thick
Thickest ~70 km at mountains
Thinnest ~20 km Basin & Range regions
Average density of 2.7 g/cm3

10. The Mohorovicic Discontinuity
The “Moho” is the boundary between the crust & mantle
P wave velocities abruptly increase at the “Moho”

11. The Mantle ~80% of earth’s volume Solid rocky layer? Convection Cells
Peridotite
The “D” layer

12. The Core-Mantle Boundary (Guttenberg Discontinuity)

13. The Outer Core
Is a liquid (absence of S waves)
Density of 9.9 g/cm3
Mostly iron with some nickel

14. The Inner Core
Is a solid
Density of 13 g/cm3
Growing as the Earth cools
Rotates faster than other layers

15. The Earth’s Temperature
Heat flows from hotter to colder areas
Earth’s core is 5500° C (10,000° F)
Earth’s surface is 0° C (32° F)
Heat flows from the core to the surface

16. How Did our Earth Get Hot?
Accretion
Radioactive Decay
Asteroid collision
Forming our moon

17. Types of Heat Transfer Conduction Convection Radiation
Molecular Activity
Convection
Movement/Circulation
Radiation
Subatomic Movement

18. Mantle Convection & Plate Tectonics

19. Temperature Profile Geothermal Gradient Crust is 30° C/km
Mantle is 0.3°C/km
Except the “D” layer

20. Earth’s Magnetic Field
Convection of iron in outer core
Random reversals throughout history
During reversals earth is unprotected

23. End of Chapter 12