1. STRUCTURE OF THE EARTH

2. Differentiation of Earth Earth is divided into layers based on density and composition Solid Layers – Core (iron-nickel) – Mantle (pyroxene, olivine) – Crust (feldspars) Liquid/Gas Layers – Hydrosphere (water) – Atmosphere (gases) Fig 1.3

3. Differentiation of Earth Early Earth was mostly molten ("liquid rock") More dense material pulled by gravity to the center of Earth Less dense feldspar minerals formed solid crust Fig 9.8

5. Earth's internal heat comes from:internal heat Residual heat from planetary accretion (about 20%) Residual heat from planetary accretion Heat produced through radioactive decay (80%). Radioactive isotopes in the Earth are:radioactive decay potassium-40 uranium-238 uranium-235 thorium-232 At the center of the planet, the temperature may be up to 7,000 K and the pressure could reach 360 GPa

6. INNER CORE Based on the abundance of chemical elements in the solar system, their physical properties, and other chemical constraints regarding the remainder of Earth's volume, the inner core is believed to be:solar system Solid Composition - iron-nickle alloy -with very small amounts of some other elements. 1220 km thick (radius) Depth from crust: 5155 km

7. TemperatureTemperature of the inner core estimated using experimental and theoretical constraints on the melting temperature of impure iron at the pressure (about 330 GPa)GPa 5,700 K (5,430 °C; 9,800 °F). Pressure in Earth's inner core 330 to 360 GPa (3,300,000 to 3,600,000 atm) iron can only be solid at such high temperatures because its melting temperature increases dramatically at these high pressures.

8. OUTER CORE Liquid layer 2,260 km thick Composed of iron and nickelironnickel Outer boundary lies 2,890 km (1,800 mi) beneath the Earth's surface.

9. Temperature of the outer core: – 4400 °C in the outer regions – 6100 °C near the inner core Eddy currents in the nickel iron fluid of the outer core are believed to influence the Earth's magnetic field. Eddy currentsfluid Earth's magnetic field The outer core is not under enough pressure to be solid, so it is liquid even though it has a composition similar to that of the inner core. Sulfur and oxygen could also be present in the outer core.Sulfuroxygen

10. Highly viscous layer between crust and outer core ~2890 km thick (1800 miles) Makes up 84% of Earth by volume Structure known from seismology (earthquake studies) MANTLE

11. Convection Currents Plates move because heat is being released from deep inside the earth. Convection currents in the mantle cause hot material to rise and expand (plates diverge) and cooler material to sink and contract (plates converge).

12. Lower Mantle (Mesosphere) Depth from surface: 600 Thickness: 2300 km More rigid than asthenosphere High temperature---from 500 to 4,000°C--- enough to melt the rocks but the pressure is so great that these rocks remain in the solid/plastic form

13. Asthenosphere (weak sphere) Below the lithosphere Depth from surface: 100 km Thickness: 100 km Upper mantle Slight melting due to increased temperature/pressure (makes it weak) Lithosphere “floats” over it

14. Lithosphere (sphere of rock) Crust and upper mantle: solid rock Depth from surface: 10 km 100 km thick (average) 250 thick (mountains) Few km thick (oceans) Rigid Cool

15. Plate

16. Mohorovicic Discontinuity The “Moho” Discovered in 1909 Seismic wave velocity increases below ~ 50 km Boundary between crust and mantle

19. covers mantle solid outer shell “floats” on mantle upper part of the lithosphere made of 2 parts: continental crust and oceanic crust THE CRUST

21. CONTINENTAL CRUST crust is thickest below the continents Thickness: 30-40 km older than oceanic crust rocks consist mainly of granites---light colored, with large grains Average density is 2.7 g/cm 3

22. Oceanic crust covers ocean floor 6-11 km thick made of a rock called basalt---dark, fine rock made from lava that cools quickly rocks contain iron and magnesium grains of rock very small average density is 3 g/cm 3