We can see how do deal with this if we take a particular case. For example the amount of Rb in mantle rocks is generally low, i.e. The mantle thus has a low If these two independent dates are the same, we say they are concordant.PART 1: Back to Basics PART 2: Problems with the Assumptions PART 3: Making Sense of the Patterns This three-part series will help you properly understand radiometric dating, the assumptions that lead to inaccurate dates, and the clues about what really happened in the past.

An hourglass is a helpful analogy to explain how geologists calculate the ages of rocks.

When we look at sand in an hourglass, we can estimate how much time has passed based on the amount of sand that has fallen to the bottom.

Considering that the half-life of potassium-40 (40K) is fairly long (1,250 million years, Mc Dougall and Harrison, 1999, p.

9), the K-Ar method cannot be used to date samples that are much younger than 6,000 years old (Dalrymple, 1991, p.

After the passage of two half-lives only 0.25 gram will remain, and after 3 half lives only 0.125 will remain etc.

To see how we actually use this information to date rocks, consider the following: Usually, we know the amount, N, of an isotope present today, and the amount of a daughter element produced by decay, D*.

Considering that the dacite probably erupted in 1986 AD, Austin should have known that at least some of the samples would have given dates that were younger than 2 million years old and that Geochron Laboratories could not have provided reliable answers.

wrote: “I just wanted to drop a note to express my gratitude for the kind of information you supply at the CMI web-site.

Anyone can learn technical jargon (queue Wikipedia page for Potassium Argon Dating); reading this post only requires a knack for scientific reasoning.

Before I begin, there is one set of terms you should be able to distinguish: radiometric dating is a method of estimating the age of geological events using radioactive isotopes in minerals; radioactive dating occurs in the storage room at the nuclear power plant and has very little to do with geology.

Over the years, Answers in Genesis has committed to undermining the credibility of radiometric dating techniques.