This age is computed under the assumption that the parent substance (say, uranium) gradually decays to the daughter substance (say, lead), so the higher the ratio of lead to uranium, the older the rock must be.
Of course, there are many problems with such dating methods, such as parent or daughter substances entering or leaving the rock, as well as daughter product being present at the beginning.
Steve Austin and his associates at the Institute for Creation 'Research' (ICR) collected a dacite sample from Mt. Helens, Washington State, USA, which probably erupted in 1986 AD. then ineffectively separated the sample into several mineral and glass 'fractions', submitted the dacite and its 'fractions' for potassium 40-argon 40 (K-Ar) dating, and subsequently used the bogus results to inappropriately attack the K-Ar method. If the earth were only 6000–10 000 years old, then surely there should be some scientific evidence to confirm that hypothesis; yet the creationists have produced not a shred of it so far.Where are the data and age calculations that result in a consistent set of ages for all rocks on earth, as well as those from the moon and the meteorites, no greater than 10 000 years? Second, it is an approach doomed to failure at the outset.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. Most scientists today believe that life has existed on the earth for billions of years.