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.
Early attempts at establishing an absolute time scale utilized the following concepts: declining sea levels, cooling of the Earth, cooling of the Sun, Earth tidal effects, sediment accumulation, and changes in ocean salinity.
This works because elements have a life cycle known as a “half-life.” A half-life refers to the amount of time it takes for an isotope to lose half of its atoms as a result of decaying.
When an isotope decays, it often becomes a different kind of element altogether.
He was employed at Caltech's Division of Geological & Planetary Sciences at the time of writing the first edition.
He is presently employed in the Space & Atmospheric Sciences Group at the Los Alamos National Laboratory.
...calculation was based on the assumption that the substance of the Earth is inert and thus incapable of producing new heat.
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)...
Further evidence comes from the complete agreement between radiometric dates and other dating methods such as counting tree rings or glacier ice core layers.
Scientists, using rigorous methods have established a process to eliminate this problem by calibrating radiocarbon dating results to items of a known age.
In this way, items of unknown age can be tested and an age determined to a reasonable degree of accuracy. More tomorrow where we explore the concept of isochron dating and how it neatly destroys most of the rest of these ‘issues’.
The first is that atoms have always decayed at the same rate.
And this isn’t really an assumption as the decay rates have been tested in the laboratory for a hundred years or so, we have an example of a natural nuclear reactor where we can measure the various products and determine the decay rates (and the fine structure constant), and we can observe the past by looking deep into the past of the universe. The sigh isn’t for the effort of writing, it’s for the effort of finding all the references.
Radiometric dating is a process of identifying the age of a material based on known half-lives of decaying radioactive materials found in both organic and inorganic objects.