1. Lecture 20 Earth's Interior and Geophysical Properties

2. Lecture Outline IEarth's Internal Structure A)The Crust B)The Mantle C)The Core i.Composition ii.Core-Mantle Boundary IIIsostasy IIIEarth's Gravity IVEarth's Magnetic Field A)Magnetic Reversals B)Magnetic Anomalies VHeat Within the Earth VIConclusions Lecture 20 i

3. Geophysics photo by John Galetzka, USGS geophysics: the branch of earth science which employs physical measurements and mathematical models to explore and analyze the structure and dynamics of the solid Earth and other bodies and their fluid envelopes

4. Controls on Seismic Wave Velocity pressure state of matter composition of matter

5. Controls on Seismic Wave Velocity Pressure

6. Controls on Seismic Wave Velocity Composition Material V p (ms -1 ) Density (gcm -3 ) Salt 4.6 2.2 Quartz 6.1 2.7 Calcite 6.7 2.7 Dolomite 7.4 2.9 Siderite 7.0 4.0 Pyrite 8.4 5.0

7. Controls on Seismic Wave Velocity State of Matter

8. Earth's Internal Structure crust mantle core

9. Earth's Internal Structure The Crust Mohorovicic Discontinuity (Moho)

10. Earth's Internal Structure Crustal Thickness

11. Earth's Internal Structure Crustal Thickness (United States)

12. Earth's Internal Structure The Composition of the Crust

13. Earth's Internal Structure The Mantle

14. Mantle is Solid (S waves propagate) Mantle is Rigid (seismic waves propagate) Mantle is Fluid (convection cells present)

15. Earth's Internal Structure The Composition of the Mantle Hofman Hart and Zindler Hutchinson Mason 1988 1986 1974 1966 SiO 2 45.96 46.38 45.00 48.10 MgO 37.78 38.12 39.00 31.10 FeO 7.54 7.62 8.00 12.70 Al 2 O 3 4.06 4.10 3.50 3.10 CaO 3.21 3.24 3.25 2.30

16. Earth's Internal Structure The Core Size: radius 3480 km (1/2 Earth) volume 1/8 Earth mass 1/3 Earth Properties: density10-13 g/cm 3 pressure136-330 GPa temperature5500±1500 K stateliquid-solid

17. Earth's Internal Structure Composition of the Core  Iron  Nickel ~ 4%  Light Element (O or S) 10% by mass

18. Earth's Internal Structure Major Discontinuities crust/mantle - the MOHO inside mantle (400 km and 670 km) mantle/outer core (CMB) outer/inner core (ICB)

19. Earth's Internal Structure Major Discontinuities - The Moho

20. Earth's Internal Structure The Core-Mantle Boundary  MAJOR Discontinuity  S-waves blocked by liquid outer core

21. Isostasy the condition of equilibrium, comparable to floating, of the units of the lithosphere above the asthenosphere.

22. Isostasy

23. Isostastic Adjustment erosion and deposition glacial rebound crustal thickening

24. Isostastic Adjustment Erosion and Deposition

25. Isostastic Adjustment Glacial Rebound

26. Isostastic Adjustment Crustal Thickening

27. Gravity gravity: the attraction between two masses, such as the Earth and an object on its surface. Commonly referred to as the acceleration of gravity (g).

28. Gravity

29. Gravity Anomaly

33. Earth's Magnetic Field

35. Rock Magnetism

36. Earth's Magnetic Field

39. Heat within the Earth

42. Sources of Earth's Heat Pressure Sunlight Radioactive Decay Primordial Heat

43. Redistribution of Earth's Heat Radiation Conduction Convection

44. Redistribution of Earth's Heat Conduction

45. Redistribution of Earth's Heat Convection