ANT100Y1 Lecture Notes - Lecture 9: Cosmic Ray, Carbon-12, Stone Tool
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ANT100Y1 Full Course Notes
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A radiometric dating method, based on radioactive decay of isotopes. Isotopes=different forms of an element with different atomic weights ie different numbers of protons and neutrons in the nucleus. Some isotopes are stable, others are unstable--gradually decay, changing into stable elements. Can be used to date objects/organisms, if you know: Problem if sample is older than context. Some materials contain ancient carbon--date will not be accurate. Sea mammal bone (plankton ingests ancient carbon, sea mammal ingests it, dating its composition as older than organism) Rate of decay is measured by a half-life (the time it takes for half of the isotope to decay) Most common form of carbon=carbon 12 (stable. Plants absorb c14 in carbon dioxide during photosynthesis; eaten by herbivores, eaten by carnivores. As c14 decays (converting to n14) it releases radioactive beta particles. Geiger counter used to estimate amount of c14 left in sample. Charcoal, wood, seeds, bone, all ideal artifacts for dating.
