Carbon dating bones
This relatively new technique was developed in order to achieve more accurate dates than those obtained from the potassium-argon method.
The older method required two samples for dating and could produce imprecise dates if the argon was not fully extracted.
The number of tracks increases over time at a rate that depends on the uranium content.
Measuring the proportions of argon-39 and argon-40 within a sample allows the age of the sample to be determined.
Fossils and other objects that accumulate between these eruptions lie between two different layers of volcanic ash and rock.
An object can be given an approximate date by dating the volcanic layers occurring above and below the object.
The heat from a volcanic eruption releases all the argon from the molten rock and disperses it into the atmosphere.
Argon then starts to re-accumulate at a constant rate in the newly formed rock that is created after the eruption.