My Issues(?) with Radioisotope (Radiometric) Dating

In earlier posts, I made some comments about not completely trusting Radiometric dating.  I doubt I’ll ever be an expert on the science, but I do have a sort of rudimentary understanding of it.

The basic idea behind radiometric dating is that a specific isotope decays to another isotope.  One of the more common isotope decays is Potassium (K) to Argon (Ar).  This kind of decay is found in lava flows.  Basically, there is a small amount of K found in the lava rock, and over time, it decays to Ar.  Based on the half life of Ar, we can ascertain how much Ar has been generated since the lava flow hardened.  This gives a reasonable length of time.

The initial problem, one I’ve heard a lot and many young-earth creationists proclaim, is that you cannot guarantee there isn’t any “excess” Ar in the lava when it hardened.  Thus, if the lava flow were covered by, say, water, the amount of Ar in the rock would be much higher than what is released by the K atoms.  This would lead to false ages, since there would be much more Ar than should be for the measurement.  Many people say that if there were a worldwide flood (like the case of Noah), then the water over the earth would account for too much Argon, thus misleading the measurements of K-Ar to falsely show older dates.

What I haven’t seen much of, personally, is how young earth creationists deal with the Ar-Ar dating that scientists use to account for any “excess” Ar.  Basically, if you take the rock sample, and place it next to a nuclear reactor, the radioactivity will force the K to make a different Ar isotope.  Then you can measure the 2 different Ar isotopes and determine if there is a constant ratio between them.  If the ratio is relatively constant, then there is a good chance that there was no excess Argon.  If the ratio is erratic, then the sample has been contaminated, so it is typically thrown out as “too old.”

Thus, it would seem that science has a relatively reliable way to determine the age of certain types of rocks.  Now, there have been many young-Earth creationists that have K-Ar dated lava flows of known eruptions, and the results are inconsistent with recorded history.  Famously, a scientist sent a sample of rock from the Mt. St. Helens eruption in 1980 and the lab (unknowing to the origins of the rock) returned a date of 2M years +/- 600k years.  Obviously this is wrong, and the scientist in question definitely gamed the system to make an “expose” of the K-Ar method.  Before submitting his sample, the lab said their equipment was unable to detect Ar levels of rock less than 2M years old, but he submitted anyway.

Basically, I have 2 main “issues” with the method, and perhaps there are answers out there that I have not personally found yet – again, I’m not a geologist, and I’m just reading stuff online, so these are questions, not necessarily critiques.

1 – Why is it that *most* K-Ar calculations are in the Millions of years?  Is the method capable of dating younger rocks correctly?  By “younger” I mean eruptions that can be corroborated by historical record.  If so, then great – evidence K-Ar works really well!  If not, why not?  How else can we calibrate the equipment/method?

2 – If God were to have used a significant amount of Argon in the creation of the planet, for whatever reason, then the Ar would be evenly distributed throughout the earth.  This would cause a constant ratio between Ar(40) and Ar(39) when doing Ar-Ar dating, and falsely generate old dates.

Again, I’m not a scientist, but I would hope that the scientific method would generate repeatable, consistent results, regardless of the age of the specimen.

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  • Jonathan

    I just want to say that even though I don't always comment, I enjoy the read. Thanks for the interesting posts