With this in mind geologist have long known that the deeper a sedimentary rock layer is the older it is, but how old?
This feature is produced by changes in deposition over time.
Among the best-known techniques are radiocarbon dating, potassium-argon dating and uranium-lead dating.
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 or radioactive dating is a technique used to date materials such as rocks or carbon, in which trace radioactive impurities were selectively incorporated when they were formed.
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.
Though relative dating can only determine the sequential order in which a series of events occurred, not when they occur, it remains a useful technique especially in radiometric dating.