How does radioactive dating relate to fossils and radioactive waste?

Answer 1

There are a number of types of radiometric dating. Carbon-14 dating, which is perhaps best known, can only be used for things some thousands of years old at most, and so is not particularly useful for fossils. Other types of radiometric dating, however, are good for hundreds of thousands or millions of years, and these are very useful for fossils. In fact they can be used to estimate the ages of various kinds of rocks.

Radioactive waste is a pollutant that affects some radiometric dating techniques, skewing them. For example, above ground nuclear testing in the 1950s and 1960s produced waste carbon-14, almost doubling the amount in the atmosphere for some time. This would make samples from that period appear too new.

Most radioactive materials in nuclear waste or pollution would not have this sort of effect, however. In order to influence radiometric dating, the material measured has to be part of the pollution or has to be generated from it. Carbon-14 results from a collision of a neutron with nitrogen-13 (a hydrogen atom is also generated). But this happens in the upper atmosphere as a result of cosmic rays. There are very few sources of neutrons on Earth, with uranium-235 probably being the most common. So ordinary nuclear waste from such sources as power plants will not usually skew carbon-14 dating.

On the other hand, the isotopes other than carbon-14 that are used in radiodating may be among those in nuclear waste. Among the isotopes that might be affected are those used in iodine-xenon dating, rubidium-strontium, and potassium-argon dating. Nuclear pollutants might include these isotopes in them, and so exposure would possibly skew results.

There are other forms of pollution that affect carbon dating. Burning of fossil fuels increases the amount of carbon dioxide in the atmosphere without increasing the amount of carbon-14. This would make some samples from the period after about 1700 appear too old.