Argon radiometric dating

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That means even minor mechanical disturbance, like heating, can allow them to escape.So potassium-argon is the least stable commonly-used dating method.Geologists have used this method to date rocks as much as 4 billion years old.It is based on the fact that some of the radioactive isotope of Potassium, Potassium-40 (K-40) ,decays to the gas Argon as Argon-40 (Ar-40).A line whose slope is proportional to the age of the sample is called an isochron.

The cure for this problem is pretty straightforward.One out of every 10,000 Potassium atoms is radioactive Potassium-40 (K-40).These each have 19 protons and 21 neutrons in their nucleus.Most of the things that upset K-Ar dating, like slow escape of Ar atoms, weathering, or heating, make ages too young by resetting the clock.Occasionally, ages can be too old, for example, historic lava flows can yield K-Ar ages of millions of years.

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