Question

How do we know how old a fossil is?

Answer 1

Fossils:

Fossils are the preserved remains of organisms like plants and animals that existed on the earth a long time ago but got buried or extinct.

Estimation of the age of the fossil:

The age of the fossils are estimated through two methods:

1. Relative method:

• The depth at which the fossil is found is related to the period during which the fossil (organism) lived.
• This means that the organism present at a deeper level from the surface of the earth got buried before the organism that is present near the surface of the earth.
• The organism (fossil) present near the surface of the earth is buried later and is therefore from a recent period as compared to another fossil that is buried at a deeper level.

2. Carbon dating method:

• This method measures the ratio of the amount of the isotopes of the same element. In carbon dating, a radioactive isotope of carbon, that is carbon-14 (C-14) present in a fossil is used to estimate its age.
• The ratio of the isotopes in a fossil is compared to the ratio of the isotopes in the organisms present today to know the difference.
• C-14 is a radioactive isotope and is not absorbed by the organisms after their death, therefore, its amount is used to estimate the time of the death of the organism. There is a reduction in the radioactivity of this isotope after death.