Together with stratigraphic principles, **radiometric** **dating** methods are used in geochronology to establish the geologic time scale.Among the best-known techniques are radiocarbon **dating**, potassiumâ€“argon **dating** and uraniumâ€“lead **dating**.

To see how we actually use this information to date **rocks**, consider the following: Usually, we know the amount, N, of an isotope present today, and the amount of a daughter element produced by decay, D*.By definition, D* = N-1) (2) Now we can calculate the age if we know the number of daughter atoms produced by decay, D* and the number of parent atoms now present, N.By allowing the establishment of geological timescales, it provides a significant source of information about the ages of fossils and the deduced rates of evolutionary change.**Radiometric** **dating** is also used to date archaeological materials, including ancient artifacts.Nd ratios on several minerals with a mass spectrometer and then from the slope determine the age of the rock. If a magma cools quickly on the surface of the Earth, some of the Ar may be trapped.

The initial ratio has particular importance for studying the chemical evolution of the Earth's mantle and crust, as we discussed in the section on igneous **rocks**. If this happens, then the date obtained will be older than the date at which the magma erupted.The method compares the abundance of a naturally occurring radioactive isotope within the material to the abundance of its decay products, which form at a known constant rate of decay.and is now the principal source of information about the absolute age of **rocks** and other geological features, including the age of fossilized life forms or the age of the Earth itself, and can also be used to date a wide range of natural and man-made materials.Different methods of **radiometric** **dating** vary in the timescale over which they are accurate and the materials to which they can be applied.All ordinary matter is made up of combinations of chemical elements, each with its own atomic number, indicating the number of protons in the atomic nucleus.We can also construct a Concordia diagram, which shows the values of Pb isotopes that would give concordant dates.