email - September 2001

Danny Defends Argon Dating

We received a long email from Danny that had several points worth discussing. We don’t have space to discuss them all this month, but we can address some of them. Maybe we will have space to address the remainder next month.

Subject: Evolution page
Date: Fri, 31 Aug 2001 10:52:00 -0700 (PDT)
From: Danny

While I find your page on evolution humorous and well written, I have to ask where on earth you got the view of evolution that you did.

3) … Your point about Mt. St. Helen's may be true, I haven't heard of such a thing, and it seems suspcious that the only source on this is an institute of creationism (why not have neutral geology or geophysics labs who have no stake in the evolution argument made this claim). However I'm willing to give you the benefit of the doubt and assume for the moment it is true. If it is, that STILL doesn't make your claim valid. Just because there are errors in measurement, doesn't mean that all measurements are in error. …

Where did we get our view of evolution? We got it from public school, from biology textbooks, from National Geographic, and from PBS television programs. Danny implies that the view of evolution we are trying to dispel is unscientific. We agree. But the general public believes that it is scientific because the public gets its view of evolution from public schools, biology textbooks, National Geographic, and PBS television programs. Our goal is to show the general public that what they have been taught is contrary to scientific principles.

Danny’s comment about Mount St. Helens has to do with tests to check the assumption that fresh lava contains no radiogenic argon. These tests show that fresh lava sometimes has so much argon in it that the lava appears to be several million years old. This is important because potassium-argon dating is sometimes used to date hominid fossils.

Danny is skeptical because the “only source” of data is the Institute for Creation Research. He would rather have data from “neutral geology or geophysics labs.” (We wonder what makes a lab “neutral.” His implication is that creationists are biased and evolutionists aren’t. That, of course, is ridiculous.)

Furthermore, ICR didn’t do the analysis. ICR collected the rock samples and sent them to a reputable geology laboratory that does potassium-argon dating.

ICR isn’t the only source of such information. We suggested to Danny that he do a literature search for the term “excess argon” and see what he found. Unfortunately he thought we meant to do a simple Internet search. He wrote,

I did as you suggested. The first two hits on google were both from the ICR which isn't helpful. The #3 hit actually argues persuasively against the Mt. St. Helen's data that you cite. As does the #4 hit. However they are from uncertain (and seemingly biased) sources, and I take them with the same skepticism as I did the ICR report. The URL for your perusal is: http://home.mmcable.com/harlequin/evol/lies/lie024.html

The #5 hit was from the New Mexico Bureau of Geology which I would consider a neutral source as it is not specifically devoted to debunking or supporting evolution. This report states that there are probably errors with excess argon. However, the conclusions are about 10 orders of magnitude less than what you would need for your argument to be convincing.

Danny probably means "10 times" not "10 orders of magnitude", which is 10,000,000,000 times.)

What we meant was for him to do a literature search of respected scientific journals. We thought that since his email address was from a well-known university that he would have access to a library that would allow him to search those journals. Since I (without using your contributions) have paid the big bucks to be able to search the archives of the highly respected journal Nature, I did what we suggested Danny do, and sent him excerpts from the first two hits. Here they are.

Nature 387, 586 - 589 (1997)
The Lu-Hf dating of garnets and the ages of the Alpine high-pressure metamorphism
S. DUCHÊNE, J. BLICHERT-TOFT, B. LUAIS, P. TÉLOUK, J.-M. LARDEAUX & F. ALBARÈDE

[snip]

Other than K-Ar, of which the significance is obscured by the unpredictable presence of excess argon, high-temperature paths of eclogite exhumation have so far been dated using only two methods. U-Pb dating of zircons gives, in principle, reliable crystallization ages, although zircon is not a mineral specific to high-pressure assemblages. In addition, as best shown in the case of Dora Maira linear arrays defining concordia lower intercepts indicate the presence of inherited lead and therefore do not provide unambiguous crystallization ages. Ion-probe dating can recognize old discordant areas in zircons, but the youngest part of the concordia is linear, making mixing between young populations difficult to identify. The second method, which is that of Sm-Nd internal isochrons in garnet-bearing rocks, often fails when isotopic equilibration between clinopyroxene and garnet has not been achieved. In addition, the small spread of Sm-Nd ratios severely limits the precision of this method of dating. The closure temperature of Sm-Nd in garnet is still debated but is supposed to be higher than 600°C, which should provide valuable information on the timing of eclogite exhumation. [emphasis supplied]

Nature 400, 58 - 61 (1999)
Cretaceous age for the feathered dinosaurs of Liaoning, China

[snip]

To address the possibility of argon loss and/or trapped excess argon, CO2-laser incremental-heating of the sanidine of P4T-1 was also undertaken (Fig. 3b). The release profile (Fig. 3b) was relatively flat with only a slight deviation from a plateau occurring at the lowest three temperature increments. All of the 24 increments that formed the plateau yielded over 95% radiogenic 40Ar and totalled more than 90% of the 39Ar released from the sample. The calculated age for the plateau is 124.6 +/- 0.1 Myr (Fig. 3b). The uniformly high radiogenic yields of all 24 increments resulted in a small cluster of points when plotted on an inverse (36Ar/40Ar vs 39Ar/40Ar) isochron, making any fit unreliable. If we include the three lower radiogenic steps that fell outside the plateau in the isochron, an age of 124.6 +/- 0.1 Myr (MSWD (mean sum of weighted deviates) = 1.48) is obtained. The 40Ar/36Ar intercept of 286.2 +/- 10.7 is not distinguishable from the air ratio. The incremental-heating and single-crystal experiments indicate little alteration of the sanidine, no discernible excess argon and no apparent detrital contamination of the sanidine. [emphasis supplied]

We were merely looking for confirmation that the “excess argon” problem is well known in scientific circles, but we got an unexpected bonus.

The first hit illustrates how geologists pick and choose the dating technique based upon whether or not they give the desired answer. Duchêne et al. have gotten the dates they desire using Lu-Hf dating. They are certainly aware that other scientists might use K-Ar, U-Pb, Ion-probe, or Sm-Nd dating and get significantly different results. Therefore, they have to make a preemptive strike to discredit the other dating techniques.

Finally, Danny said, “Just because there are errors in measurement, doesn't mean that all measurements are in error.”

We aren’t talking about measurement error. There wasn’t really any “excess argon” in the lava from Mount St. Helens. There was exactly the right amount of argon, and it was properly measured. The measured amount just happened to be more than the amount of argon predicted by the incorrect assumptions used for potassium-argon dating.

We aren’t talking about measurement error. We are talking about methodological error. There is a difference. Measurement error has to do with incorrectly measuring the amount of certain elements in rocks. Methodological error has to do with the erroneous assumptions about how those elements got to be in the rocks.

The scientific method has to do with proposing a theory and then designing experiments to test that theory. The theory behind potassium-argon dating is based on the idea that there was no radiogenic argon in ancient lava flows when they were formed, and that all the argon that is in them now came from potassium decay. One way to test that theory is to see if there is any argon in recent lava flows. The theory behind potassium-argon dating says there should not be any. The data says there often is some. Which do you reject-the theory or the data?

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