Geological dating radioactive elements age dating fault gouge
They were found, however, in much younger sediment and it is not known where these zircons originated.
The second approach, which is more indirect but gives an answer currently believed correct, involves a comparison of the Earth with meteorites.
The remaining number of radioactive atoms is halved every half-life.
Radioactive elements of use in geological dating have relatively long half-lives.
Since 1950, radiometric methods have been developed to a very sophisticated level in several countries, including Canada.
It has been demonstrated that when rocks which have led an undisturbed history are analysed, all methods reveal the same age.
This change takes place at a known rate determined by the half-life; ie, the time required for one-half of the original number of radioactive atoms to convert to the stable daughter product.
These discussions were rendered obsolete by the discovery of radioactivity in 1896 by the French physicist Henri Becquerel.
The existence of radioactivities of various kinds in rocks has enabled earth scientists to determine the age of the Earth, the moon, meteorites, mountain chains and ocean basins, and to draw up a reasonably accurate time scale of evolution.
Charles Darwin reinforced this idea by pointing to the time that must have been required for the EVOLUTION of advanced life from primitive forms.
On the other hand, the great physicist Lord Kelvin vehemently objected and suggested that the Earth might only be a few tens of millions of years old, based on his calculations of its cooling history.
Rocks of almost this age have also been identified in other localities, including Labrador, Minnesota, Africa and India.