Problems with radiometric dating methods

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Certain unstable isotopes of trace radioactive elements in both organic and inorganic materials decay into stable isotopes. By measuring the proportion of different isotopes present, researchers can figure out how old the material is.

Here are some of the most common radiometric methods: Radiocarbon dating: Sometimes called carbon-14 dating, this method works on organic material.

Sometimes only one method is possible, reducing the confidence researchers have in the results. “They’re based on ‘it’s that old because I say so,’ a popular approach by some of my older colleagues,” says Shea, laughing, “though I find I like it myself as I get more gray hair.” Kidding aside, dating a find is crucial for understanding its significance and relation to other fossils or artifacts.

Methods fall into one of two categories: relative or absolute.

Both plants and animals exchange carbon with their environment until they die.

Afterward, the amount of the radioactive isotope carbon-14 in their remains decreases.

Before more precise absolute dating tools were possible, researchers used a variety of comparative approaches called relative dating.

The good dates are confirmed using at least two different methods, ideally involving multiple independent labs for each method to cross-check results.Unlike observation-based relative dating, most absolute methods require some of the find to be destroyed by heat or other means.This family of dating methods, some more than a century old, takes advantage of the environment’s natural radioactivity.While K-Ar dating requires destroying large samples to measure potassium and argon levels separately, Ar-Ar dating can analyze both at once with a single, smaller sample.Uranium series dating: U-series dating includes a number of methods, each based on different uranium isotopes’ decay rates.

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