This dating method is based upon the decay of radioactive potassium-40 to radioactive argon-40 in minerals and rocks; potassium-40 also decays to calcium-40. On the other hand, the abundance of argon in the Earth is relatively small because of its escape to the atmosphere during processes associated with volcanism.

Why is potassium-40 used to date fossils?

The element potassium is stable at the atomic mass of 39, but it has a radioactive isotope, potassium-40. The half-life of potassium-40 is 1.3 billion years. Rocks can require 200,000 years for enough argon gas to build up to provide an accurate measurement. As a result, this technique is used to date older objects.

Is potassium used to date rocks?

Potassium-Argon Dating Potassium is a component in many common minerals and can be used to determine the ages of igneous and metamorphic rocks.