Potassium 40 dating rocks

30 Jan

Potassium argon (40K-40Ar) dating is a form of radiometric dating widely used because of the range of dates for which it is useful.

The technique can be used for dates ranging from earth's beginning, 4550 mya (4.55bn in US terminology) to about 100,000 years ago.

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.

A second problem is that for technical reasons, the measurement of argon and the measurement of potassium have to be made on two different samples, because each measurement requires the destruction of the sample.

If the mineral composition of the two sample is different, so that the sample for measuring the potassium is richer or poorer in potassium than the sample used for measuring the argon, then this will be a source of error.

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.

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In the case of potassium-argon decay, this loss of a proton causes the atom to change from a reactive alkali metal to a non-reactive noble gas, which is an important characteristic.

Because argon is an inert gas, if it is not physically trapped in a rock, it will diffuse into the atmosphere.

Different methods have their own limitations, especially with regard to the age range they can measure and the substances they can date.

A common problem with any dating method is that a sample may be contaminated with older or younger material and give a false age.