1. Inside the Earth Earth’s Shape, Size and Internal Structure

2. The earth is round. Eratosthenes figured it out in 200 B.C. He calculated that Earth’s circumference was 40,000 km – only off by 8 km!!

3. Eratosthenes & the Round Earth 7.2 o angle at Alexandria No angle at Syene (on the Tropic of Cancer) Central angle is 7.2 o (1/50 th of 360 o ). A soldier paced off distance from Alexandria to Syene (5,000 stadia = 800 km).

4. Eratosthenes & the Round Earth (5,000 stadia = 800 km). Multiply X 50, you get the circumference of the Earth: 800 km X 50 = 40,000 km Actual diameter of the Earth (pole to pole) = 40,008 km. Incredibly close for this method of measuring!

5. The earth is sort of round – Oblate Spheroid Due to its rotation, Earth bulges slightly at the equator (about 0.17 % bigger) and is slightly flattened at the poles. It is an oblate spheroid.

6. The earth is sort of round – Oblate Spheroid Equatorial diameter is just 0.17 % bigger than the Polar diameter.

7. The earth is tilted at a 22 ½ o angle.

8. 4 Layers of the Earth Crust 0 – 70 km thick 2,885 km 5,100 km 6,400 km 2,885 km thick 2,270 km thick 1,216 km thick Scale

9. 2 Types of Crust 1) Oceanic Crust 2)Continental Crust 5 – 10 km 20 – 70 km } }

10. Continental Crust- GraniteOceanic Crust - Basalt } Two Essentially Different Rock Types

11. The Mantle – Thickest Single Layer Mesosphere - Lower Mantle (Solid Again) Asthenosphere – Crust and uppermost mantle (Plastic, weak, flows like Silly Putty) Lithosphere – Crust and Uppermost mantle (Solid, Rigid, Brittle)

12. The “Moho” The Mohorovičić discontinuity (“Moho” for short) is a sudden, sharp boundary between the crust and the upper mantle. Increase in P wave velocity is due to a sudden increase in density of the rocks.

13. Layers of the Mantle Lithosphere – Rigid and Brittle (partly crust) Asthenosphere – Plastic and flowing Mesosphere (lower mantle) – Solid Again

14. Rocks of the Mantle Magnetite – Iron Oxide Olivine Peridotite – Iron Silicate Minerals

15. Inner and Outer Cores Outer Core: Liquid Iron and Nickel Hot, but not as hot as the inner core 2,270 km thick

16. Core – Mantle Boundary Huge mountainous “anti- continents” of solid mantle protrude downward into the “anti- oceans” of the liquid iron core.

17. The Two Cores Outer Core – Hot liquid Iron and Nickel with lumpy core /mantle boundary Inner Core – Even hotter but crystalline Iron and Nickel

18. Core Materials The inner core is thought to be made of crystalline iron similar to the type we find in iron meteorites. These distinctive crystal patterns are called Widmanstatten lines.

19. Thicknesses of the 4 Layers Crust 0 – 65 km thick 2,900 km 5,100 km 6,400 km 2,885 km thick 2,270 km thick 1,216 km thick Scale

21. 4 Layers of the Earth