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p. 909. Uranium, thorium, and their daughterslocked

  • Rob Ellam


All isotopes heavier than 208Pb (lead) are radioactive and many of these have half-lives that are long compared to the age of our Solar System. ‘Uranium, thorium, and their daughters’ describes the natural decay series where radioactive isotopes of uranium and thorium decay by α- and β-emission through several stages until a stable lead isotope is produced. The age of the Solar System and Earth has been established at 4.55 Ga through the isochron approach; U-Pb dating was also used to date the boundary between the Cretaceous and Palaeogene geological periods to 66 Ma, the period associated with a mass extinction on Earth when 70 per cent of living things died out.

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