1. Earth’s Interior

3. Evidence for the structure of Earth’s interior is indirect
P and S seismic waves provide evidence of a multi-layered interior with each section possessing distinct properties
Density and gravity studies of Earth and its influence on other celestial bodies requires an interior more dense than the crust
Meteorite samples provide material evidence for the composition of Earth’s interior

4. Seismic waves (P & S) increase in velocity at depth of 10 to 30 km (varies locally)
This is the boundary between the crust and mantle
Density increases abruptly
The boundary is called the Mohorovicic Discontinuity

5. You can call it the MOHO

6. P and S waves

7. P and S wave shadow zone
No seismic waves are received in a zone on the other side of Earth from the Focus ( degrees )

8. P waves only are received at an angle greater than 143 degrees from the focus

9. P waves are deflected as they travel through a new medium - the liquid outer core

10. S waves do not travel through liquids

11. Outer core is liquid inner core is solid

13. Isaac Newton
Observed Earth’s gravitational influence on other celestial bodies
If Earth is to have enough mass to exert that much gravity, it’s interior must be more dense than the crust
Several minerals are possible

15. Properties of Earth’s interior
Must be dense
Must contain liquid to stop S waves
Must be metallic to create magnetic field when rotating

16. Meteors contain elements from early solar system and formation of planets
Meteors contain heavy elements iron and nickel
Iron and nickel are dense enough and exist as a liquid at pressures and temperatures inferred for Earth’s core

17. Inferred properties of Earth’s interior

18. Summary Earth has very thin crust which fractures easily
Mantle is below the crust and is much more dense
Outer core is a viscous liquid and is made of iron and nickel
Earth has a solid iron-nickel inner core
Density, temp, and pressure all increase from the crust to the inner core

19. Temp and pressure increase with depth

21. The End