‘Radio-dating in rubble’ article ‘ignores’ data?

7 October 2002

JF from Illinois, USA, says he finds many of our articles on the age of the Earth and Radiometric dating ‘excellent’. Nevertheless he jumps to conclusions by imagining that one of our authors is ‘ignor[ing]’ a fact. The response by Dr Tas Walker shows that it is nothing of the sort. Rather, it shows the importance of detecting underlying assumptions behind supposed facts.

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Evidence for a young Earth

I have been writing a paper on radiometric dating and the age of the earth. Since your magazine has lots of excellent articles on these topics, I have been using it. However, I ran across a problem with one of your articles. Keith Swenson’s article titled Radio-dating in Rubble in the June–August 2001 issue (pg 23–25) discussed using the Potassium-Argon method to date the rocks on Mount St. Helens. In Dalrymple’s book Potassium-Argon Dating: Principles, Techniques, and Applications to Geochronology, Dalyrmple clearly states on page 194 (end of chapter 10) that the youngest rocks that can be dated are rocks which are at least 1,000 years old. Why did Mr. Swenson ignore this fact? In his tables of wrong dates (pg 24), several of the dates there were older than 1,000 years. Why not focus on those dates? Please let me know as I am confused about this issue.



Dear JF,

We’re glad you’ve found our articles helpful. But when you ask, ‘Why did Mr. Swenson ignore this fact?’, it commits a logical fallacy known as a leading question, i.e. a question that presupposes what needs to be proved. It would have been better to ask whether a fact was ignored.

Good experimental work involves properly matching your measuring instrument to the quantity that you want to measure. In the case of potassium-argon dating, we want to accurately measure the relevant potassium and argon isotopes. If there is not enough argon in the sample then the measuring instrument will not be able to measure it accurately. Dalrymple imagines that very-young samples wouldn’t have enough argon to measure accurately because there has not been enough time for it to be produced by radioactive decay. However, his conclusion is only correct if argon were only produced by radioactive decay. I.e. you overlooked that Dalrymple’s ‘fact’ actually presupposes something that actually needs to be proved.

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Radiometric Dating

The results presented in Table 1 of Mr Swenson’s article shows that there was plenty of argon in the Mt St Helens samples. There was an equivalent of 2.8 million years of argon in the pyroxene sample. It was so abundant that the instrument could measure it to an precision of ±0.6 million years. The feldspar sample also had lots of argon and gave an age of 340,000 years. It was some six times more abundant than the precision of measurement which was equivalent to ±60,000 years.

So, there was no problem with the experimental technique. However, the known age of the samples was ten years. Thus, the experiment has shown that one of the basic assumptions of radioactive dating is not correct. The argon in the rock was not produced by radioactive decay, but was present when it formed. So, if the method fails on rocks of known age, why should we trust it on rocks of unknown age, especially when it contradicts the eyewitness testimony of the Bible.

Dr Tas Walker
Creation Ministries International

Published: 4 February 2006