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Claim CD013:

Potassium-argon dating of rocks from lava flows known to be modern gave ages millions to billions of years older.


Morris, Henry M., 1974. Scientific Creationism, Green Forest, AR: Master Books, pp. 146-147.


  1. Argon may be incorporated with potassium at time of formation. This is a real problem, but it is easily overcome either by careful selection of the material being dated or by using 40Ar/39Ar dating instead of K-Ar dating.

    In the case of the claim about recent lava yielding dates that are millions to billions of years old, H. M. Morris (1974) misstated the facts concerning these "anomalous" dates as published in Funkhouser and Naughton (1968). The main misstatements of fact by Morris are as follows:

    Morris cited other examples of anomalous dates produced by excess argon and falsely claimed that it is a universal problem for K-Ar dating. The problem is not universal, as the majority of minerals and rocks dated by K-Ar do not contain the excess argon. Where excess argon is a problem, accurate, reliable dates typically can be obtained using 40Ar/39Ar dating, as demonstrated by Dalrymple (1969) and Renne et al. (1997) and discussed by Dalyrmple (2000).

  2. Morris's complaints are dated in that, for the most part, geologists no longer use the K-Ar dating technique as was practiced in 1974. Instead, K-Ar dating has been largely replaced by the related 40Ar/39Ar dating technique. This change also solved other problems that Morris complained about in his discussion of the K-Ar dating technique. These complaints were as follows:

    1. Claim: K-Ar dating techniques must be calibrated by uranium-lead (U-Pb) dating.

      Response: Some calibrations between U-Pb and K-Ar were done in the 1940s and early 1950s, but the decay rates of all the different radioisotopes involved are now known to within 1 percent, making the different dating techniques independent.

      With 40Ar/39Ar dating, it is possible to calibrate this dating method by using volcanic deposits created in historic volcanic eruptions -- for example, the eruption of Mount Vesuvius on August 24, 79 C.E. (Renne et al. 1997). In addition, 40Ar/39Ar dating can be compared not only with U-Pb dating techniques but also with other absolute dating techniques -- for example, K-Ar, Rb-Sr, and Sm-Nd dating techniques -- which all provide dates consistent with each other and with associated 40Ar/39Ar dates. This has been demonstrated by the dating of chondrite meteorites (Dalrymple 1991) and tektites and other ejecta and deposits created by the giant meteorite impact at Chicxulub in the Yucatan Peninsula (Dalrymple et al. 1993).

    2. Claim: The potassium-argon is an open system.

      Response: The papers cited by Morris fail to probe this point. The first paper simply demonstrates that rock altered by weathering cannot be dated. This is a common-sense conclusion understood by geologists literate in the basics of their profession; it is irrelevant to the unaltered minerals that are typically dated using K-Ar, 40Ar/39Ar, and other techniques. The final paper claims potassium is quite mobile because potassium can be extracted from iron meteorites by using distilled water. However, K-Ar dating commonly uses potassium silicate minerals, which are very insoluble in water and resist weathering. Potassium cannot be significantly leached from the minerals used in K-Ar dating, or, conversely, the minerals from which significant potassium can be leached are not the minerals used in K-Ar dating.

    3. Claim: The decay rate of potassium is subject to change.

      Response: This is simply not true.

    4. Claim: Argon maybe incorporated with potassium at time of formation.

      Response: See first point (a) above.

    5. Claim: K-Ar ages are extremely variable.

      Response: As previously noted, K-Ar and 40Ar/39Ar dating both provide extremely consistent dates when the methods are used properly (Dalrymple 1991; 2000). The single paper (Engels 1971) cited by Morris clearly stated that variability resulted from presence of unwanted impurities in the specific mineral being dated. If the sample dated consisted of an absolutely pure mineral, there would not be any variability in the K-Ar dates obtained from them.


harlequin2, 2001. Ar-Ar dating assumes there is no excess argon?

harlequin2, 2001. 200 year old lava dated 2.96 billion years old?

Lindsay, Don, 2000. Fresh lava dated as 22 million years old.

Stassen, Chris, 1999 (Jan.). Feedback response. (4th response down)


  1. Dalrymple, G. Brent, 1969. 40Ar/36Ar analyses of historic lava flows. Earth and Planetary Science Letters 6: 47-55.
  2. Dalrymple, G. Brent, 1991. The Age of the Earth. Stanford, CA: Stanford University Press.
  3. Dalrymple, G. Brent, 2000 (May/Jun). Radiometric dating does work! Some examples and a critique of a failed creationist strategy. Reports of the National Center for Science Education 20(3): 14-17.
  4. Dalrymple, G. B., G. A. Izett, L. W. Snee and J. D. Obradovich, 1993. 40Ar/39Ar age spectra and total-fusion ages of tektites from Cretaceous-Tertiary boundary sedimentary rocks in the Beloc formation, Haiti. United States Geological Survey Bulletin no. 2065.
  5. Engels, J. C., 1971. Effects of sample purity on discordant mineral ages found in K-Ar dating. Journal of Geology 79: 609-616.
  6. Funkhouser, J. G. and J. J. Naughton, 1968. Radiogenic helium and argon in ultramafic inclusions from Hawaii. Journal of Geophysical Research 73(14): 4601-4607.
  7. Morris, 1974. (see above.)
  8. Renne, P. R., W. D. Sharp, A. L. Deino, G. Orsi and L. Civetta, 1997. 40Ar/39Ar dating into the historical realm: Calibration against Pliny the Younger. Science 277: 1279-1280.

Further Reading:

Attendorn, H.-G. and R. N. C. Bowen, 1997. Radioactive and Stable Isotope Geology. London: Chapman & Hall.

Faure, G., 1986. Principles of Isotope Geology, 2nd ed. New York: Wiley.

McDougall, I. and T. M. Harrison, 1988. Geochronology and Thermochronology by the 40Ar/39Ar Method. Oxford Monographs on Geology and Geophysics no.9. New York: Oxford. (technical)

Thompson, Timothy, 2003. A radiometric dating resource list.

Wiens, Roger C., 1994, 2002. Radiometric dating: A Christian perspective.
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created 2003-6-9, modified 2004-9-21