Radiogenic dating methods
By far, the most well-known type of radiometric dating is method using the radioactive isotope of carbon, carbon-14.
However, when the life form dies and is buried or otherwise stops interacting with atmospheric gases there will be no further increase in the amount of radioactive carbon in the system.One of the primary decay products of K-40 is Ar-40--a stable and unreactive gas.Potassium decay has been established as the only source of Argon in volcanic rocks; it is a gas so most of it escapes unless it is formed after the molten rock has solidified, and it is not a major product in any other reactions.It is especially disposed to dating minerals such as Zircon.Zircon is a fairly abundant mineral that exists in many forms in the environment, and because of its chemical structure Uranium is easily incorporated into its molecules.Carbon-14 is present a level of about 1 part per trillion in the atmosphere--for every trillion particles of carbon one is C-14.
While this is an extremely trace amount, over time it is incorporated into the systems of most life forms.
U-238 decays to Pb-206, and U-235 decays to Pb-207.
These two decay pathways have different half-lives that have been measured and recorded.
In this case determining the age of the surrounding earth or rock materials can be very helpful in determining the age of the sample.
Potassium-Argon (K/Ar) dating is a method that applies directly the dating of rocks.
This means that if the amounts of C-14 and N-14 in a sample are known, then its age can be calculated for a wide range of years.