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Geology Estimating the Age of Rocks

Estimating the Age of Rocks


The dating of rocks is possible because of radioactive atoms.

Radioactive atoms decay at different rates but for a particular atom the rate is constant. It is because we know
the decay rate of different atoms we can accurately determine the age of a rock which contains Carbon 14.

Carbon 14 is an isotope of carbon. It is present in plant and animal matter and is useful for dating rocks 40,000
to 70,000 years old. We can accurately age a rock in this time period by determining how much Carbon 14
remains in the rock. Carbon 14 decays at a constant rate.

Carbon 14 decays by:

C14 8 neutrons N14 7 neutrons

———— Radioactive Decay ——————> + Energy released

6 protons 7 protons