As long as an organism is alive, the supply of carbon-14 is replenished.
When the organism dies, the supply stops, and the carbon-14 contained in the organism begins to spontaneously decay into nitrogen-14.
Stratigraphy: Study of layers of rocks or the objects embedded within those layers.
The age of the remains of plants, animals, and other organic material can be determined by measuring the amount of carbon-14 contained in that material.
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