The level of nitrogen gradually reduces as the bone decays.
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.
This problem is now reduced by the careful collection of samples, rigorous crosschecking and the use of newer techniques that can date minute samples.
Volcanic rocks – such as tuff and basalt – can be used in dating because they are formed at a particular moment in time, during an eruption.
Instead, other methods are used to work out a fossil’s age.
These include radiometric dating of volcanic layers above or below the fossils or by comparisons to similar rocks and fossils of known ages.
This damage is in the form of tiny marks called fission tracks.
When volcanic rocks and minerals are formed, they do not contain fission tracks.
Most fossils are found in sedimentary rocks deposited in layers.Argon is gas that gradually builds up within rocks from the decay of radioactive potassium.It is initially formed in the molten rock that lies beneath the Earth’s crust.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.