112-pp8a - UNIVERSITY OF SOUTH ALABAMA Quiz Three...

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1 Quiz Three (10:10-10:15 AM) GY 112: Earth History Stable Isotope Stratigraphy UNIVERSITY OF SOUTH ALABAMA Last time we covered… 1. Radioactive Decay 2. Radiometric Dating 3. Mass spectrophotometers ....on the chalk board (Doug’s wrist is still sore!) Radioactive Decay Radioactive Decay Three modes of decay 1) Alpha Decay Loss of alpha particle Convert parent into element that has nucleus containing two fewer protons 2) Beta Decay Loss of beta particle Convert parent into element whose nucleus contains one more proton by losing an electron 3) Gamma Decay Capture of beta particle Convert parent into element whose nucleus has one less proton Radioactive Decay http://mike.gamerack.com/science/halflifeu238.gif Uranium Decay 238 U 206 Pb + 8 α
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2 Radioactive Decay • Radiometric dating – Radioactive isotopes decay at constant geometric rate • After a certain amount of time, half of the parent present will survive and half will decay to daughter • Half-life – Interval of time for half of parent to decay Absolute Age • Absolute ages change – Error increases in older rocks – Techniques change • Biostratigraphic correlations may be more accurate Radiometric dating Very old rocks, REE bearing minerals 106,000,000,000 143 Nd (Neodymium-143) 147 Sm (Samarium-147) Various rocks and minerals 48,600,000,000 87 Sr (Strontium-87) 87 Rb (Rubidium-87) Metamorphic, igneous rocks, Zircon, U-bearing minerals 14,000,000,000 208 Pb (Lead-208) 232 Th (Thorium-232) Metamorphic, igneous rocks, Zircon, U-bearing minerals 4,500,000,000 206 Pb (Lead-206)
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This note was uploaded on 02/04/2012 for the course GLY 112 taught by Professor Haywick during the Spring '12 term at S. Alabama.

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112-pp8a - UNIVERSITY OF SOUTH ALABAMA Quiz Three...

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