The half-lives of the cascade from uranium-235 to lead-207 has been been extrapolated to about 704 million years and the cascade form uranium-238 to lead-206 has been calculated to about 4.47 billion years.This data is compared to a curve called the Concordia diagram.Definition Uranium–Lead dating is the geological age-determination method that uses the radioactive decay of uranium (U) isotopes (238U, 235U, and also in this entry 232Th) into stable isotopes of lead (Pb) (206Pb, 207Pb, and 208Pb, respectively).
Some of the classic problems with this kind of dating process include what the process can really date, how far the radiometric process can date accurately, and the assumptions taken so the dating process works.
One assumption is to use a worldview that uniformitarianism is accepted Where is the time from starting point, the original amount of uranium, the amount of uranium at the measurement, the original amount of lead, the amount of lead at the measurement, the rate uranium changes to lead, the average rate of loss and gain in the amount of lead, the average rate of loss and gain in the amount of uranium..
It may sound straight-forward, but there are many variables that have to be considered.
The three main parameters that have to be set are the original amount of uranium and lead in the sample, the rate at which uranium and lead enter and leave the sample, and how much the rate of decay changes.
This diagram has been made by using the ratio of uranium to lead of all the rocks dated with this method and their assumed age.