Difference between relative dating and radiometric dating
When ‘parent’ uranium-238 decays, for example, it produces subatomic particles, energy and ‘daughter’ lead-206.
Isotopes are important to geologists because each radioactive element decays at a constant rate, which is unique to that element.
These rates of decay are known, so if you can measure the proportion of parent and daughter isotopes in rocks now, you can calculate when the rocks were formed.
Because of their unique decay rates, different elements are used for dating different age ranges.
The age determined by relative dating is based on the rules of super imposition and the presumed age of strata based on fossils.Absolute dating(also known as radiometric dating) is based by the measurement of the content of specific radioactive isotopes of which the "half time" is known.Half time is the time needed for half of a given quantity of an isotope to decay in its byproducts.Scientific American Oct 1980 156-168 The rocks on the surface of the southern Appalachians are older than the sedimentary layers under them.Ager, Derek I can think of no cases of radioactive decay being used to date fossils.