It will be necessary for an expert to check my understanding of this, which comes from a brief (but recent) conversation with geochemist who knows radioactive dating very well. If my information is not fully accurate, blame me rather than assume that the experts don't know the answer. :-)
The rocks in question from Mt St Helens did not go through a liquid state prior to ejection from the volcano. Therefore, K-Ar dating cannot be used. That method assumes that all of the Ar gas found within a given sample is a result of the decay of the K since the rock hardened; prior to that time, when the rock is in a liquid phase, the Ar simply gets away.
What is disturbing about this particular claim (that is, the one creationists typically make in this instance), according to this particular expert, is that those rocks are known not to have gone through the liquid phase shortly before they were ejected, and therefore that any K-Ar dates they yield are known not to give the date at which they were ejected. That is, all of this was known by the creationist "experts", so (as in the case with the RATE project) it is substantially about integrity. It's possible that I could get the person who told me this to make a public comment here, but I don't know him well and he's a busy person. I'll look into it.
Ted
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Received on Wed Nov 5 06:51:16 2008
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