Earth age uranium dating conversation starters dating site
The results from these zircons therefore plot along that straight line, establishing what is called a discordia. If a 1500-million-year-old rock is disturbed to create a discordia, then is undisturbed for another billion years, the whole discordia line will migrate along the curve of the concordia, always pointing to the age of the disturbance.
This means that zircon data can tell us not only when a rock formed, but also when significant events occurred during its life.
However, zircon is so overwhelming a favorite that geologists often just refer to "zircon dating."But even the best geologic methods are imperfect.
Dating a rock involves uranium-lead measurements on many zircons, then assessing the quality of the data.
The two cascades are different—235U becomes 207Pb and 238U becomes 206Pb.
What makes this fact useful is that they occur at different rates, as expressed in their half-lives (the time it takes for half the atoms to decay).
This apparent consistency in textbooks and the media has convinced many Christians to accept an old earth (4.6 billion years old).In a 704-million-year-old rock, 235U is at its half-life and there will be an equal number of 235U and 207Pb atoms (the Pb/U ratio is 1).In a rock twice as old there will be one 235U atom left for every three 207Pb atoms (Pb/U = 3), and so forth.With 238U the Pb/U ratio grows much more slowly with age, but the idea is the same.If you took rocks of all ages and plotted their two Pb/U ratios from their two isotope pairs against each other on a graph, the points would form a beautiful line called a concordia (see the example in the right column). First, its chemical structure likes uranium and hates lead.