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Origin of the solar system
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Solar Systems Form by Accretion
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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
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Exosolar systems 1137 known systems, 467 known to have multiple planets (two have 7 planets) Some problems for standard theory: orbits not often circular and not coplanar and not all orbit in same direction! Maybe planetary interactions are generally more important than in our solar system
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Formation of the moon
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e=(ra-rp)/(ra+rp), a=(rp+ra)/2
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Meteorites and the composition of the Earth
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Timing of core/moon formation
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Principles of Isotope Geology: Conventional radiogenic isotope systematics used in geology: 147 Sm - 143 Ndt 1/2 = 10.6 x 10 10 yrs 87 Rb- 87 Srt 1/2 = 48.8 x 10 9 yrs 238 U- 206 Pbt 1/2 = 4.47 x 10 9 yrs 235 U- 207 Pbt 1/2 = 0.704 x 10 9 yrs 232 Th- 208 Pbt 1/2 = 14.01 x 10 9 yrs 187 Re - 187 Os t 1/2 = 42.3 x 10 9 yrs 176 Lu - 176 Hft 1/2 = 35.7 x 10 9 yrs
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The Law of Radioactive Decay The basic equation: - - dN dt N or dN dt =N # parent atoms time 1½¼1½¼ D* = Ne t - N = N(e t -1) age of a sample (t) if we know: D* the amount of the daughter nuclide produced N the amount of the original parent nuclide remaining the decay constant for the system in question (= ln 2/ t ½ ) More conventionally, D (present) = D o + D*
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These systematics are being used as chronometers a)model age b)isochron age and as petrogenetic tracers….
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Hf is enriched in the silicate mantle after core formation
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Major structural divisions of the Earth
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