Uranium 238 dating process white label dating affiliate
Join Britannica's Publishing Partner Program and our community of experts to gain a global audience for your work!Uranium-234–uranium-238 dating, method of age determination that makes use of the radioactive decay of uranium-238 to uranium-234; the method can be used for dating of sediments from either a marine or a playa lake environment.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).Other minerals sometimes used for uranium-lead dating include monazite, titanite and two other zirconium minerals, baddeleyite and zirconolite.However, zircon is so overwhelming a favorite that geologists often just refer to "zircon dating." But even the best geologic methods are imperfect.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).
In a rock twice as old there will be one 235U atom left for every three 207Pb atoms (Pb/U = 3), and so forth.Dating a rock involves uranium-lead measurements on many zircons, then assessing the quality of the data.Some zircons are obviously disturbed and can be ignored, while other cases are harder to judge.This means that zircon data can tell us not only when a rock formed, but also when significant events occurred during its life.
The oldest zircon yet found dates from 4.4 billion years ago.Of all the isotopic dating methods in use today, the uranium-lead method is the oldest and, when done carefully, the most reliable.