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Though we know that K-Ar dating works and is generally quite accurate, however, the method does have several limitations.First of all, the dating technique assumes that upon cooling, potassium-bearing minerals contain a very tiny amount of argon (an amount equal to that in the atmosphere).While this assumption holds true in the vast majority of cases, excess argon can occasionally be trapped in the mineral when it crystallizes, causing the K-Ar age to be a few hundred thousand to a few million years older than the actual cooling age.

The discovery gave scientists a tool for dating rocks that contain radioactive elements.Many elements have naturally occurring isotopes, varieties of the element that have different numbers of neutrons in the nucleus.of grains between top and bottom is always proportional to the time elapsed.In principle, the potassium-argon (K-Ar) decay system is no different.The concept of how these methods work is simple: one element decays into another at a rather predictable rate. If these assumptions are correct, then the radiometric dates are correct.

However, there is no way to independently test these assumptions.(The nucleus of an atom is made up of protons and neutrons.) For example, the element carbon, which always has six protons in its nucleus, has three isotopes: one with six neutrons in the nucleus, one with seven, and one with eight.Some isotopes are stable, but some are unstable or radioactive.Scientists determined the Earth's age using a technique called radiometric dating.Radiometric dating is based upon the fact that some forms of chemical elements are radioactive, which was discovered in 1896 by Henri Becquerel and his assistants, Marie and Pierre Curie.The rates of decay of various radioactive isotopes have been accurately measured in the laboratory and have been shown to be constant, even in extreme temperatures and pressures.