Carbon-14 is produced at a constant rate in Earth’s atmosphere and is in a fixed ratio compared to Carbon-12 in living plants and animals.
Ratio of Carbon-14 to Carbon-12 in organic material decreases by half every 5,730 years.
On land, pollen and insect remains are used for dating deposits from the Quaternary ice age.
In 1897, the great physicist Lord Kelvin was one of the first scientists to use physico-chemical principles in calculating the age of the Earth at between 20 and 40 million years!
The age of lava is closely related to the time at which the sediment above and below it was deposited.
In 1905, Rutherford used the decay of uranium to calculate a mineral’s age at 500 million years old.
Radiometric dating is based on the amount of time it takes certain radioactive substances to decay.
Atoms with identical chemical properties, but different weights, are known as isotopes of an element.
Until recently, sedimentary rocks were not suitable candidates for radiometric dating, because the age of a specific grain in sedimentary rock, such as sandstone, is the age at which the mineral formed in its original igneous setting and not when it was locked into the sedimentary deposit.
The problem has been to relate radiometric dates from igneous rock to the stratigraphic record, which consists mainly of sedimentary deposits.