These layers are like bookends -- they give a beginning and an end to the period of time when the sedimentary rock formed.By using radiometric dating to determine the age of igneous brackets, researchers can accurately determine the age of the sedimentary layers between them.Using the basic ideas of bracketing and radiometric dating, researchers have determined the age of rock layers all over the world.This information has also helped determine the age of the Earth itself.For example, by using a laser, researchers can measure parent and daughter atoms in extremely small amounts of matter, making it possible to determine the age of very small samples [source: New Scientist].
Radiometric dating isn't the only method of determining the age of rocks.
Each of them typically exists in igneous rock, or rock made from cooled magma.
Fossils, however, form in sedimentary rock -- sediment quickly covers a dinosaur's body, and the sediment and the bones gradually turn into rock.
As discussed before, the assumptions influence the interpretation of the data.
There are three main assumptions that must be made to accept radiometric dating methods.
These must be accepted on faith in uniformitarian and naturalistic frameworks.