Thomas and Morris on Radioisotope Dating

The February edition of Acts & Facts is out, and the first article we’ll look at is the “Q&A,” Doesn’t Radioisotope Dating Prove Rocks Are Millions of Years Old?, by John Morris and Brian Thomas (M&T, as well shall call them). The answer they are aiming for is, of course, “no.”

Radioisotope decay rates are renowned for constancy under normal conditions, so this assumption appears reasonable. But two observations and two clues omitted from physics textbook discussions of radiodating show that these radioisotope “clocks” are broken.

The four examples that they give should not be unfamiliar to anyone by this point – we have seen them all many times before. But in the interests of creating a shadow Q&A they are worth looking at again.

First, scientists have observed that radioactive isotope (radioisotope) decay rates do fluctuate, including Th-228, Rn-22, and Si-32. Although these particular isotopes are not used to date rocks, they illustrate that radioisotope decay (radiodecay) is not always constant.

Yes, the decay of some elements can be unreliable – this can be a good reason not to use them for dating. The specific reason why those particular three elements are not used, however, is likely because their half-lives are too short to be of any use (note: “Rn-22″ is a typo, as no such isotope could ever exist, but all isotopes of radon from 220 to 229 have half-lives of less than 4 days). The kind of fluctuations to which they are referring to, believed to be in some way caused by the sun, are also exceptionally small – much too small to add noticible uncertainty to dates already calculated, and certainly to allow the potential for a 6000 year old Earth. M&T cite this paragraph to a Creation Science Update article from July 2011, which I wrote about at the time, but a much more detailed blog post on this research can be found here.

Second, rocks observed to form on a particular date often show radioisotope age estimates far exceeding their actual ages. For example, when the fresh lava dome at Mount St. Helens was only ten years old, it showed a radioisotope age estimate of 340,000 years! Many such examples cast doubt on the entire dating method.

The infamous Mt St Helens dating used a method already known to be useless when used on anything less than two million years old. The test is analogous to using a metre ruler to measure the thickness of a piece of paper: a wildly inaccurate reading is the fault not of the ruler, but of the person holding it.

According to M&T, these results “prompted a team of seven creation researchers to investigate the causes of incorrect radioisotope age estimates,” i.e. the RATE project. Not these specific results, mind you, as the project predates the first.

They found two clues in granite rock that are best explained by radioisotopes that decayed much faster in the past than they do today. One clue was abundant helium trapped in tiny zircon crystals inside granite. Decaying uranium atoms emit alpha particles, which are equivalent to helium nuclei. Helium escapes the crystals at a measurable rate. If granites are billions of years old, helium levels inside the crystals should have long since depleted. But crystals from supposedly billion-year-old granites are packed with helium. The best explanation for this is that radioactive decay that would normally take billions of years actually occurred very quickly.

An extensive discussion of Russell Humphreys’ helium diffusion claim can be found at talk origins (I told you these were old). His conclusions seem to be generally error-riddled.

The presence of abundant microscopic radiohalos in granite—darkened scars on certain minerals within granite—provided the second clue. Radioactive polonium-210 emits particles to quickly become lead-206. Also, as hot liquid magma cools to form solid granite, it can only capture the short-lived polonium radiohalos at a specific temperature range—allowing a time window of just days. Researchers found many short-lived polonium radiohalos right beside uranium radiohalos, which would not be expected. The best explanation for slow-cooling granite and quick-forming radiohalos is accelerated decay. Billions of years’ worth of uranium decay (at today’s rates) must have occurred within polonium’s lifetime of hundreds of days. This could only occur if radiodecay was once much faster.

The last piece of evidence is, of course, polonium halos. The first problem with this idea is over whether or not the halos are actually created by polonium, while the second is that polonium is produced all the time from the decay of other elements.

What could have caused the acceleration? Scientists have discovered a few conditions, such as ionization and fluid transport of daughter products, but nobody yet knows the exact cause of the acceleration.

Both of those papers are much older than the RATE project, so M&T’s implication that scientists are now searching for an explanation doesn’t seem to hold up. The applicability of the two studies cited to the issue also seems doubtful.

They conclude:

Trapped helium and short-lived polonium radiohalos present in granite suggest that radiodecay rates were once much higher than they are today. Plus, significantly older radiodates for rocks of a known age show that radiometric dating is not reliable. Although radioisotope methods may have some use in estimating relative ages of rocks, radioisotope methods give inflated age estimates, often because they falsely assume a constant decay rate.

The “may have some use in estimating relative ages” statement is quite interesting. It’s possible that it’s meant as a counter to the fact that radiometric dates are generally consistent with each other and with relative dates derived directly from the rocks themselves. But the creationist idea that the supposed unreliability of the dating methods is always biased dramatically in the direction they want it to be is implausible enough, and claiming on top of that that the relative order of dates would remain intact only worsens the probability. But an admission that they would be prepared to accept that two rocks dated to the same age are the same age could be useful – let’s hope they meant it.

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3 thoughts on “Thomas and Morris on Radioisotope Dating

  1. I couldn’t see anything new here – though no doubt some of it will be ‘new’ for fledgling YEC apologists including those recently converted to Christianity.

  2. There is nothing new here. Nothing, that is, that doesn’t belong to the last millennium. It really illustrates what the ICR has become. It is just a bland recycling of old stories; there are no new arguments and no arguments to counter objections to the original papers.

    These stories do not even all support the basic argument that decay rates have changed. ‘Excess Argon within Mineral Concentrates from the New Dacite Lava Dome at Mount St. Helens Volcano’ by Steven A. Austin, Ph.D. is about what it says in the title – nothing to do with decay rates. 2Ma is by no means the lower limit of K-Ag dating. So why did Austin take his samples to the place that was incapable of doing the measurements with the accuracy that he needed? Presumably it was cheap. Geochron Laboratories claimed to be unable to date samples less than 2Ma old – Austin successfully proved it.

    The RATE project is curious. ICR claim to have many objections to radiological dating but here they are using a radiological method to date rocks – the U-He method was rejected in the early days of radiological dating as being unreliable due to helium moving so easily in and out of the materials being measured.The RATE team obtained some anomalous results and then tried to reconcile them with conventional radiological dating by assuming an effectively instantaneous decay rate. The objections to this are obvious.

    The section about polonium halos contains no references. The obvious link would be to ‘Creation’s Tiny Mystery, by Robert Gentry – http://www.halos.com/book/ctm-toc.htm

    But Gentry had a monumental bust-up with ICR over this. ICR published Impact #353 and Gentry hit back with a 60 page ‘open letter’ – http://www.halos.com/faq-replies/icr-open-lt-2003-1.pdf

    I think the gist of this argument is that Gentry asserted that the granite and the accelerated decay was associated with the creation whereas Snelling associated it with the flood.

    I think M & T need to do their homework – they hardly need to go far to find their reference material.

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