Dating minerals

After one half-life, 50 percent of the original parents remains; after two, only 25 percent remains, and so on.

Decay curve of a radioactive element with a half-life equal to one time unit.

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.

At time 1, 50% of the parent atoms remain; at time 2, only 25% remain, and so on.Once scientists have determined the parent-daughter ratio, they can use this measurement along with half-life of the parent to calculate the age of a rock containing the radioactive isotope.Radiometric dating has shown that very old rocks--3.5 billion years or older--occur on all the continents.Radiometric dating works best on igneous rocks, which are formed from the cooling of molten rock, or magma.As magma cools, radioactive parent isotopes are separated from previously formed daughter isotopes by the crystallization process.

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