# Using the earth for radiometric dating

### Using the earth for radiometric dating

It has the same number of protons, otherwise it wouldn't be uranium.

It is based on a comparison between the observed abundance of a naturally occurring radioactive isotope and its decay products, using known decay rates.

This chain eventually ends with the formation of a stable, nonradioactive daughter nuclide.

Each step in such a chain is characterized by a distinct half-life.

...igneous activity (both extrusive and intrusive) occurred in the Caledonian mountain belt, which stretched from New England, Nova Scotia, Newfoundland, Scotland, and Scandinavia to eastern Greenland.

Radiometric dating of granitic intrusions associated with the Caledonian orogeny yields ages between about 430 million and 380 million years.

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.

Radioactive elements "decay" (that is, change into other elements) by "half lives." If a half life is equal to one year, then one half of the radioactive element will have decayed in the first year after the mineral was formed; one half of the remainder will decay in the next year (leaving one-fourth remaining), and so forth.

The formula for the fraction remaining is one-half raised to the power given by the number of years divided by the half-life (in other words raised to a power equal to the number of half-lives).

If we knew the fraction of a radioactive element still remaining in a mineral, it would be a simple matter to calculate its age by the formula To determine the fraction still remaining, we must know both the amount now present and also the amount present when the mineral was formed.

Contrary to creationist claims, it is possible to make that determination, as the following will explain: By way of background, all atoms of a given element have the same number of protons in the nucleus; however, the number of neutrons in the nucleus can vary.

Scientific knowledge of Earth’s geologic history has advanced significantly since the development of radiometric dating, a method of age determination based on the principle that radioactive atoms in geologic materials decay at constant, known rates to daughter atoms.