The igneous activity that produced such intrusions...
...calculation was based on the assumption that the substance of the Earth is inert and thus incapable of producing new heat.
However, to read any clock accurately we must know where the clock was set at the beginning.
For geological purposes, this is taken as one year.
those that form during chemical reactions without breaking down).
The unstable or more commonly known radioactive isotopes break down by radioactive decay into other isotopes.
His estimate came into question after the discovery of naturally occurring radioactivity by the French physicist Henri Becquerel in 1896 and the subsequent recognition by his colleagues, Marie and Pierre Curie, that compounds of radium (which occur in uranium minerals)...
Another role of isotopic geochemistry that is of great importance in geology is radiometric age dating. Beginning with studies in the 1950s, a much better chronology and record of Pleistocene climatic events have evolved through analyses of deep-sea sediments, particularly from the oxygen isotope record of the shells of microorganisms that lived in the oceans.