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Lecture 20 Earth's Interior and Geophysical Properties

Lecture 20 Earth's Interior and Geophysical Properties. Lecture Outline. I Earth's Internal Structure A) The Crust B) The Mantle C) The Core i. Composition ii. Core-Mantle Boundary II Isostasy III Earth's Gravity IV Earth's Magnetic Field A) Magnetic Reversals

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Lecture 20 Earth's Interior and Geophysical Properties

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  1. Lecture 20 Earth's Interior and Geophysical Properties

  2. Lecture Outline I Earth's Internal Structure A) The Crust B) The Mantle C) The Core i. Composition ii. Core-Mantle Boundary II Isostasy III Earth's Gravity IV Earth's Magnetic Field A) Magnetic Reversals B) Magnetic Anomalies V Heat Within the Earth VI Conclusions Lecture 20 i

  3. Geophysics 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 photo by John Galetzka, USGS

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

  5. Controls on Seismic Wave Velocity Pressure

  6. Controls on Seismic Wave Velocity Composition Material Vp (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 StructureThe Crust Mohorovicic Discontinuity (Moho)

  10. Earth's Internal StructureCrustal Thickness

  11. Earth's Internal StructureCrustal Thickness (United States)

  12. Earth's Internal StructureThe Composition of the Crust

  13. Earth's Internal StructureThe Mantle

  14. Earth's Internal StructureThe Mantle Mantle is Solid (S waves propagate) Mantle is Rigid (seismic waves propagate) Mantle is Fluid (convection cells present)

  15. Earth's Internal StructureThe Composition of the Mantle Hofman Hart and Zindler Hutchinson Mason 1988 1986 1974 1966 SiO2 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 Al2O3 4.06 4.10 3.50 3.10 CaO 3.21 3.24 3.25 2.30

  16. Earth's Internal StructureThe Core Size: radius 3480 km (1/2 Earth) volume 1/8 Earth mass 1/3 Earth Properties: density 10-13 g/cm3 pressure 136-330 GPa temperature 5500±1500 K state liquid-solid

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

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

  19. Earth's Internal StructureMajor Discontinuities - The Moho

  20. Earth's Internal StructureThe 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

  30. Gravity Anomaly

  31. Gravity Anomaly

  32. Gravity Anomaly

  33. Earth's Magnetic Field

  34. Earth's Magnetic Field

  35. Rock Magnetism

  36. Earth's Magnetic Field

  37. Earth's Magnetic Field

  38. Earth's Magnetic Field

  39. Heat within the Earth

  40. Heat within the Earth

  41. 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

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