Start Radioactive dating exercises

Radioactive dating exercises

Potassium-argon dating is very susceptible to resetting because the argon decay products are merely held in place mechanically by surrounding atoms.

Suppose, in repaving your driveway, you find a stash of old coins buried in the ground. Of course there are more outlandish explanations, like somebody counterfeiting 1920 coins in 1900 (and successfully anticipating any changes in design in the meantime), or secretly tearing up part of the driveway after 1950, but unless someone comes up with really persuasive evidence, we're justified in ignoring these hypotheses.

The driveway was poured in 1950, and the coins are all dated 1920. Radiometric dating generally requires that a system be closed - in other words, has not had material added or removed.

Uranium-lead dating methods often use this approach because some of the minerals used in dating lose the lead decay products over time.

It's amazing how often people fail to realize that you can't date materials if they don't have the necessary ingredients. You can't use carbon-14 to date an arrowhead with no carbon in it.

If you don't have minerals with those elements, you can't date the rock.

In particular, quartzites and carbonate rocks almost always don't have enough to permit dating.

When t = 0, ln N(0) = C Taking exponentials of both sides, we get N(t) = N(0)exp(-Kt) If t = one half life, then N(t)/N(0) = 1/2 = exp(-Kt), and: ln(1/2) = -ln2 = -Kt, so t = ln2 / K So what we do in practice is determine the decay constant and calculate half life from it.