Dating rocks with uranium 238
The reason for stopping at lead is because lead is not radioactive and will not change into a different element.
It may sound straight-forward, but there are many variables that have to be considered.
In addition, the parent and daughter isotopes must remain together in a rock to use them to determine the rock's age.
Because sedimentary rocks contain fragments of many rocks that could be different ages, radiometric dating is less useful for dating sedimentary rock.
Radiocarbon dating is used to date very recent artifacts, and is usually useful only for archeological purposes.
It cannot be used to date rocks, both because of its short half life (about 5,000 years), and because it can only be used to date the remains of living things (such as bones, or wood).
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.
Uranium-lead dating uses four different isotopes to find the age of the rock.
For example the half-life of uranium is 4.5 billion years. This technique is primarily used to date igneous rocks.