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SIO224 Internal Constitution of the Earth

SIO224 Internal Constitution of the Earth. Fundamental problem: the nature of mass and heat transfer in the mantle and the evolution of the Earth. Ingredients for a unified mantle model. Seismology:1D and 3D structure of the Earth

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SIO224 Internal Constitution of the Earth

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  1. SIO224 Internal Constitution of the Earth Fundamental problem: the nature of mass and heat transfer in the mantle and the evolution of the Earth

  2. Ingredients for a unified mantle model • Seismology:1D and 3D structure of the Earth • Geochemistry: bulk composition of the Earth; heat production; geochemical tracers of “mantle reservoirs” • Mineral physics: thermoelastic properties of materials at high T and P (equations of state); phase transformations; rheology of mantle materials • Geodynamics: flow models, geoid constraints, mantle convection, effects of phase transformations and viscosity variations on convection, thermochemical convection, thermal history.

  3. Shear velocity -- +-1% isovelocity surfaces Includes S and SS cluster analysis data

  4. Origin of the solar system

  5. Solar Systems Form by Accretion

  6. Planetary migration • Giant planets have migrated over time, Uranus and Neptune were closer in but migrated out after Saturn and Jupiter went into 2:1 resonance • Jupiter also migrated slightly inward – interactions with left over material led to late heavy bombardment

  7. Exosolar systems • 2796 known systems, 625 known to have multiple planets (two have 7 planets) • On average, one planet per star and 1 in 5 Sun-like planets have an “Earth-sized” planet in the habitable zone • First planets to be identified were “hot Jupiters” – now known to be not so common • Some systems are not “nebular like” • Maybe planetary interactions are generally more important than in our solar system

  8. Formation of the moon

  9. Meteorites and the composition of the Earth

  10. Timing of core/moon formation

  11. Principles of Isotope Geology: Conventional radiogenic isotope systematics used in geology: 147Sm - 143Nd t 1/2 = 10.6 x 1010 yrs 87Rb - 87Sr t 1/2 = 48.8 x 109 yrs 238U - 206Pb t 1/2 = 4.47 x 109 yrs 235U - 207Pb t 1/2 = 0.704 x 109 yrs 232Th- 208Pb t 1/2 = 14.01 x 109 yrs 187Re - 187Os t 1/2 = 42.3 x 109 yrs 176Lu - 176Hf t 1/2 = 35.7 x 109 yrs

  12. The Law of Radioactive Decay The basic equation: dN dN - µ - l N or = N dt dt 1 ½ ¼ # parent atoms D* = Nelt - N= N(elt -1) age of a sample (t)if we know: D*the amount of the daughter nuclide produced Nthe amount of the original parent nuclide remaining lthe decay constant for the system in question (= ln 2/ t ½) More conventionally, D(present) = Do + D* time 

  13. These systematics are being used as chronometers • model age • isochron age and as petrogenetic tracers….

  14. Earth composition continued….. • lithophile elements (oxygen, oxides, silicate minerals, Greek lithos - stone) • chalcophile (sulphides, Greek khalkos=copper) • siderophile (metallic, Greek sideros=iron)

  15. Hf is enriched in the silicate mantle after core formation

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