Radioactive decay is a natural process and comes from the atomic nucleus becoming unstable and releasing bits and pieces.

These are released as radioactive particles (there are many types).

dating rocks by radioactivity-54

This technique has become more widely used since the late 1950s.

Its great advantage is that most rocks contain potassium, usually locked up in feldspars, clays and amphiboles.

The relationship between the two is: T = 0.693 / λ Many different radioactive isotopes and techniques are used for dating.

All rely on the fact that certain elements (particularly uranium and potassium) contain a number of different isotopes whose half-life is exactly known and therefore the relative concentrations of these isotopes within a rock or mineral can measure the age.

However, potassium is very mobile during metamorphism and alteration, and so this technique is not used much for old rocks, but is useful for rocks of the Mesozoic and Cenozoic Eras, particularly unaltered igneous rocks.

Argon-Argon dating (39Ar-40Ar) This technique developed in the late 1960s but came into vogue in the early 1980s, through step-wise release of the isotopes.

those that form during chemical reactions without breaking down).

The unstable or more commonly known radioactive isotopes break down by radioactive decay into other isotopes.

This decay process leads to a more balanced nucleus and when the number of protons and neutrons balance, the atom becomes stable.