How do We Determine the Age of Fossils?

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Fossils are the remains of prehistoric animals and plants. They could be thousands or millions of years old. A fossil or the rock in which it is found is slightly radioactive. By measuring this radioactivity, the age of fossils can be determined. Over a span of time, the radioactivity of material decreases to zero. It may take thousands or million of years for a material to lose its radioactivity. Plants and animals contain in them small amounts of radioactive elements. This radioactivity begins to decrease as soon as they die. Measuring this radioactivity, thus gives their age.

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