Value of potassium argon dating to geologists

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Potassium is a common element found in many materials, such as micas, clay minerals, tephra, and evaporites.In these materials, the decay product Ar is able to escape the liquid (molten) rock, but starts to accumulate when the rock solidifies (recrystallizes).Potassium (K) is one of the most abundant elements in the Earth's crust (2.4% by mass).

Lava flows that lie above and below rock beds with ancient human fossils are a good—and true—example.The potassium-argon (K-Ar) isotopic dating method is especially useful for determining the age of lavas.Developed in the 1950s, it was important in developing the theory of plate tectonics and in calibrating the geologic time scale.The rock sample to be dated must be chosen very carefully.Any alteration or fracturing means that the potassium or the argon or both have been disturbed.Ar (argon), the atom typically remains trapped within the lattice because it is larger than the spaces between the other atoms in a mineral crystal.

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