This technique is, however, useful for providing relative dates for objects found at the same site.
Knowing when a dinosaur or other animal lived is important because it helps us place them on the evolutionary family tree.
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.
The age of volcanic rocks and ash can be determined by measuring the proportions of argon (in the form of argon-40) and radioactive potassium within them.
Each volcanic eruption produces a new deposit of ash and rock.
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.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.Uranium is present in many different rocks and minerals, usually in the form of uranium-238.Instead, other methods are used to work out a fossil’s age.