Question

How do we calculate the age of a fossil?

Answer 1

1. The technique used to determine the age of a fossil is Carbon dating from the activity of C¹⁴ isotope present in it.
2. High energy cosmic rays bombard the upper atmosphere producing large number of neutrons.
3. These neutrons collide with nitrogen in the air changing some of it into Carbon-14.
   ₇N¹⁴ + ₀n¹ ―――――→ ₆C¹⁴ + ₁H¹
4. The radioactive carbon combines with oxygen in the upper atmosphere and forms CO₂ which diffuses down to earth and is absorbed by plants and animals.
5. Carbon from plants or living organisms radiates β-particles and a definite proportion of C¹⁴ isotope to C¹² isotope is maintained in all plants and living organisms.
   ₆C¹⁴ ―――――→ ₇N¹⁴ + _-1e⁰
6. When the plant or animal dies, the intake of carbon-14 stops and the C¹⁴ activity decreases. By comparing the radioactivity from present day plant or animals (N₀) with that of the given fossil (N), the age of the fossil can be accurately calculated by using the formula given below: