The number of tracks increases over time at a rate that depends on the uranium content.It is possible to calculate the age of a sample by measuring the uranium content and the density of the fission tracks.
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.
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.
Buried bones absorb chemicals, such as uranium and fluorine, from the surrounding ground and absorb more of these chemicals the longer they remain buried.
The rates of absorption depend on a number of factors which are too variable to provide absolute dates.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.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.Sedimentary rocks are rarely useful for dating because they are made up of bits of older rocks.