Radioactive dating methods
Ways they make conflicting results tell the same story
by Tas Walker
When it comes to measuring the ages of things, we are told that there are a dozen
different radioactive dating methods and that they all give the same answer. Do
they?
Fossil wood from a quarry near the town of Banbury, England, some 80 miles north-west
of London, was dated using the carbon-14 method.1
The ages calculated ranged from 20.7 to 28.8 thousand years old. However, the limestone
in which the wood was found was of Jurassic age, of 183 million years.
Clearly the dating methods are in conflict.
Surprisingly, these conflicting results do not unsettle mainstream geologists.
Diamonds analyzed from mines in South Africa and Botswana, and from alluvial deposits
in Guinea, West Africa, found measurable carbon-14—over ten times the detection
limit of the laboratory equipment.2
The average ‘age’ calculated for the samples was 55,700 years. Yet the
rocks that contained the diamonds ranged from 1,000 to 3,000 million years old.
Dating methods are in conflict again.
Rock samples from a lava dome within the Mount St Helens crater, USA, were dated
using the potassium-argon method. Whole-rock samples gave an age of 350,000 years.3 When some of the amphibole
minerals in the rock sample were extracted and analyzed separately, their age was
more than double at 900,000 years. Two mineral samples of a different mineral, pyroxene,
gave an age of 1,700,000 and 2,800,000 years. Which age is right? None, actually.
The lava dome formed after Mount St Helens exploded in 1980 and the samples were
just 10 years old. Here are more conflicting results between dating methods.
Creationist scientists have uncovered dozens of anomalies and conflicts like this.
Surprisingly, these conflicting results do not unsettle mainstream geologists. They
genuinely believe the world is billions of years old, and the conflicting results
do not cause them to question their belief. In their minds, these conflicts are
a little mystery that will be resolved with creative thinking and more research.
In his well-known textbook on isotope geology, Gunter Faure explains the various
radioactive dating methods, including the so-called isochron method. When the results
for a number of rock samples are plotted on a graph and form a straight line, the
researcher can calculate an age for the samples. But Faure warns his readers not
to accept the calculated age without question.
He gives an example of volcanic lava along the border of Uganda, Zaire and Rwanda,
East Africa. That lava is known to be relatively young, possibly erupted within
historical times,4 yet a
rubidium-strontium straight-line isochron gave an age of 773 million years. Does
this worry these scientists? No. They have total faith in the method. In their minds,
the key is the way the results are interpreted. Faure says that in this
case we should interpret the line, not as an isochron, but a “mixing line”.
So how can we tell the difference? We can’t. The only way we can know it is
a mixing line is if the calculated age is wrong—and the only way one can ‘know’
if an age is right or wrong is to have a pre-existing belief about what the age
should be.
Conflicting radioactive dating results are reported all the time and, on their own,
there is no way of knowing what they mean.
In another example, Okudaira et al. measured isochron ages of a rock
called amphibolite sampled from south-east India. With the rubidium-strontium
method they obtained an age of 481 million years but with samarium-neodymium the
age was almost double at 824 million years.5
Did the disagreement cause the researchers to doubt the dating methods? Not at all.
They removed the disagreement by the way they ‘interpreted’ the results.
They said the older age was the age the rocks underwent metamorphism, while the
younger age was when the rocks were later heated. How did they know? No matter what
the numbers are, a plausible story can always be invented after the results
are obtained.
Another example involves a volcanic region in Southern India, a pluton.6 Using the lead-lead method, a whole-rock sample
gave an age of 508 million years. With the potassium-argon method, samples of mica
gave an age of 450 million years. Zircons using the uranium-lead method gave an
age of 572 million years. Three different samples; three different methods; three
different results. Did this cause the researchers to doubt the radioactive dating
methods? No. They just applied some creative interpretation. They said the different
ages are because the huge pluton cooled slowly over millions of years and the different
minerals were affected in different ways. Instead of a problem, the conflict became
a new discovery.
Conflicting radioactive dating results are reported all the time and, on their own,
there is no way of knowing what they mean. So geologists research how other geologists
have interpreted the other rocks in the area in order to find out what sort of dates
they would expect. Then they invent a story to explain the numbers as part of the
geological history of the area. Creationist geologists consider that the Bible records
the true history of the earth and that the rocks are less than 6,000 years old.
Because the Bible is reliable and historically verifiable, we consider it scientifically
valid to interpret the radioactive dating results within the biblical scenario.7
Related articles
Further reading
References
- Snelling, A., Geological conflict:
Young radiocarbon date for ancient fossil wood challenges fossil dating, Creation
22(2):44–47, 2000; creation.com/geological-conflict.
Return to text.
- Baumgardner, J., 14C evidence for a recent global
flood and a young earth; in: Vardiman, L., Snelling, A. and Chaffin, E., Radioisotopes
and the Age of the Earth, Vol. II, Institute for Creation Research, California,
USA, pp. 609–614, 2005. See also
Diamonds: a creationist’s best friend Creation 28(4):26–27,
2006; creation.com/diamonds. Return to text.
- Austin, S.A., Excess argon within mineral
concentrates from the new dacite lava dome at Mount St Helens Volcano, Journal
of Creation 10(3):335–343, 1996; creation.com/lavadome.
Return to text.
- Faure, G., Principles of Isotope Geology, 2nd
ed., John Wiley & Sons, New York, pp. 145–147, 1986. Return
to text.
- Okudaira, T., Hamamoto, T., Prasad, B.H. and Kumar, R., Sm-Nd
and Rb-Sr dating of amphibolite from the Nellore-Khammam schist belt, S.E. India:
constraints on the collision of the Eastern Ghats terrane and Dharwar-Bastarcraton,
Geological Magazine 138(4):495–498, 2001; http://geolmag.geoscienceworld.org/cgi/content/abstract/138/4/495.
Return to text.
- Miyazaki, T. and Santosh, M., Cooling history of the Puttetti
alkali syenite pluton, Southern India, Gondwana Research 8(4):576–574,
2005. Return to text.
- For articles with further information about radiometric dating,
including exciting research results, see creation.com/dating.
Return to text.
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