Each volcanic eruption produces a new deposit of ash and rock.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 method compares the abundance of a naturally occurring radioactive isotope within the material to the abundance of its decay products, which form at a known constant rate of decay.
Together with stratigraphic principlesradiometric dating methods are used in geochronology to establish the dating rocks and fossils time scale.
By allowing the establishment of geological timescales, it provides a significant source of information about the ages of fossils and the deduced rates of evolutionary change.
Instead, other methods are used to work out a fossil’s age.
Uranium is present in many different rocks and minerals, usually in the form of uranium-238.