Methods for dating rocks and fossils
Accurate dates also allow us to create sequences of evolutionary change and work out when species appeared or became extinct. These are: Where possible, several different methods are used and each method is repeated to confirm the results obtained and improve accuracy.Different methods have their own limitations, especially with regard to the age range they can measure and the substances they can date.Absolute dating is not possible with this method because the rate at which the nitrogen content declines depends on the surrounding temperature, moisture, soil chemicals and bacteria.
Argon is gas that gradually builds up within rocks from the decay of radioactive potassium.
Argon then starts to re-accumulate at a constant rate in the newly formed rock that is created after the eruption.
This relatively new technique was developed in order to achieve more accurate dates than those obtained from the potassium-argon method.
A common problem with any dating method is that a sample may be contaminated with older or younger material and give a false age.
This problem is now reduced by the careful collection of samples, rigorous crosschecking and the use of newer techniques that can date minute samples.