Holmes radiometric dating


16-Feb-2020 11:38

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If a zircon crystal originally crystallizes from a magma and remains a closed system (no loss or gain of U or Pb) from the time of crystallization to the present, then the Discordant dates will not fall on the Concordia curve.Sometimes, however, numerous discordant dates from the same rock will plot along a line representing a chord on the Concordia diagram. is then interpreted to be the date that the system became closed, and the younger date, t*, the age of an event (such as metamorphism) that was responsible for Pb leakage.If you asked the same question of an educated European in AD 1900 you would have received a quite different answer.He would have answered that the Earth was ancient, that there had not been a Noachian flood, and that the species of life had not been fixed over the history of Earth.It became clear that there had been significant changes in the Earth's topography over time and that these changes could neither be accounted for by natural processes operating during the brief nor by the postulated Noachian flood.Notable observations included: ran from about 1780-1850.

Hutton and Lyell, who held that the history of Earth was dominated by slow relatively uniform changes in an Earth with a static over all history.These were long on armchair speculation and short on substantive supporting evidence.