r. Henke reviewed my Radiometric Dating Game article, and his
review has been
A Radiometric Dating Resource List. I initially responded to him
by e-mail, and my responses are also recorded at that location. This
article is a more extensive to reply to Dr. Henke’s review. I may
omit topics which are already adequately treated in my previous
responses. I looked at the book by Dalrymple (1991), as well as the
article (Dalrymple, G. B., 1984 How Old is the Earth?: A Reply to
‘Scientific’ Creationism In “Proceedings of the 63rd Annual Meeting of
the Pacific Division, American Association for the Advancement of
Science” vol. 1, pt. 3, Frank Awbrey and William Thwaites (Eds).) I
also plan to read Woodmorappe’s new book, and may modify this web page
afterwards. I also plan to modify the Radiometric Dating Game
Dr. Henke emphasizes the assumed 4.5 billion year age of the earth,
which is not my main concern. I am mainly concerned with the age of
life on earth.
Dr. Henke gives some technical corrections to my article, which I
appreciate, but these do not affect the main argument.
Dr. Henke gives evidence that the decay rates have not changed.
I ordered Dalrymple’s book (Dalrymple, G. B., 1991 The Age of the
Earth Stanford University Press, 1991), but unfortunately it says
nothing about the effect of neutrinos on decay rates. The agreement
of many different techniques on meteorites suggests that any change in
decay rates would have to affect all of them proportionally, which
seems unlikely for changes based on large numbers of neutrinos.
However, there is reason to believe that a change in the speed of
light might also change decay rates, and cosmologies permitting a
larger speed of light in the past have been proposed by some
Dalrymple (1984, p. 88-89) refutes in some detail the various
creationist claims that radioactive decay rates may be influenced by
neutrinos, neutrons, and cosmic radiation, including Dudley’s
Dalrymple (1984, pp. 88-89) discusses various creationist proposals
for altering decay rates involving neutrons or neutrinos. He rejects
the idea that neutrinos could affect radioactive decay, but really
gives no support for this statement. He rejects Dudley’s hypothesis
of a “neutrino sea,” but this does not affect the possibility that
neutrinos from some other source (perhaps a supernova) could influence
radioactive decay. Concerning the identity of the supernova, Slusher
(Slusher, H.S., 1981. Critique of Radiometric Dating, Institute for
Creation Research, Technical monograph 2 (2nd ed.), 46 pp, p. 55)
cites F.B. Jueneman (Industrial Research, Sept., 1972, p. 15) in the
The online Encyclopedia Britannica has this to say about the Gum
The remnant of that local big bang is a pulsar called Vela-X (PSR 0833-45),
which recent observations have positioned in the southern sky some
1,500 light years away, and which is considered to have given rise to the
huge Gum Nebula ... Being so close, the anisotropic neutrino flux
of the super-explosion must have had the peculiar characteristic of
resetting all our atomic clocks.
Concerning the timing of this supernova, if the Vela Pulsar is
the same as Vela-X, then the estimated date of the supernova
would be fairly recent, according to the online Encyclopedia
Gum Nebula, largest known nebula in terms of angular diameter as seen
from Earth, extending over at least 40 degrees in the southern
constellations Puppis and Vela. A complex of diffuse, glowing gas too
faint to be seen with the unaided eye, it was discovered by the
Australian-born astrophysicist Colin S. Gum, who published his
findings in 1955. The Gum Nebula lies roughly 1,000 light-years from
the Earth and may be the remnant of an ancient supernova--i.e.,
violently exploding star.
The Crab Pulsar is the youngest known, followed by the Vela Pulsar
that has a projected timing age of 11,000 years.
Concerning a possible change in decay rates, Dalrymple (1991, p. 329)
mentions that Pb-Pb ages for meteorites tend to be about one percent
higher than Rb-Sr and K-Ar ages. This can be explained by the K-Ar
ages measuring a slightly later event, or by uncertainties in the
Rb-Sr decay constant. It can also be evidence of a change of the
decay constants, since Pb-Pb ages are based on the decay of uranium to
lead, which partially involves alpha decay, and Rb-Sr decay is based
on beta decay (ejection of an electron). K-Ar decay is based on
electron capture, which is in a sense the inverse of beta decay. So
it could be that a change in decay constants would treat K-Ar decay
and Rb-Sr decay the same, but U-Pb decay would be affected
differently. In fact, based on a comment by (apparently) Slusher
(1981), there may be a systematic difference between U-Pb ages and
K-Ar ages, which could be a further evidence of a change in decay
rates. The Pb-Pb method essentially depends on the ratio between
decay rates of two uranium-based decay systems, both involving alpha
decay. Thus the Pb-Pb method may be less sensitive to changes in the
decay constants than the U-Pb methods, and perhaps this is one reason
why it yeilds better agreement with other methods.
It is also interesting in this regard that beta decay creates an
anti-neutrino. It could just as well occur by absorbing a neutrino,
and thus an increase in the flux of neutrinos could increase the beta
decay constants. The web site
How to Change Nuclear Decay Rates mentions that electron capture
invoves the emission of a neutrino, and so it might be stimulated by
the absorption of an anti-neutrino. In fact, since neutrinos are so
difficult to detect, it could be that they are already causing some of
the radioactive decay that is observed.
Slusher (1981, p. 23) cites (Lee, T.D. and Yang, C.N.,
Phys. Rev. Lett. 4, 1960, p. 307) as predicting that “nuclear
reactions may be induced by electron neutrinos.” Slusher (1981,
p. 23) mentions that the transformation of 37Cl to 37Ar by a neutrino
“is an established method of study of high-energy solar neutrinos.”
This transformation involves the change of a neutron to a proton. The
same reaction would cause the decay of rubidium to strontium. In
fact, this reaction for rubidium might be much more likely to be
caused by neutrinos than the transformation of 37Cl to 37Ar, since
rubidium naturally decays to strontium. Thus Rb-Sr ages might be
increased significantly by large numbers of neutrinos. The same
reaction would cause the decay of carbon 14, and might increase
radiocarbon ages as well. However, since carbon 14 has such a short
half life, and decays spontaneously relatively rapidly, the effect due
to neutrinos may be smaller than for substances such as rubidium with
very long half lives. This might explain why low carbon 14 ages are
sometimes found in conjunction with lava flows having very old
radiometric ages. By analogy with the effect of neutrinos on decay,
anti-neutrinos could change a proton to a neutron, and thus contribute
to the decay of potassium to argon, increasing K-Ar ages. Since
neutrinos apparently have mass, they may be able to disturb nucleii
slightly, and thus induce unstable nucleii to decay even by alpha
decay. Another possibility is that a change in the speed of light
could influence decay constants.
If the neutrino flux contributes to radioactive decay, then we would
expect to see variations in the rate of decay, corresponding to changes
in the neutrino flux. This would imply that there would be statistical
irregularities in radioactive decay. Such irregularities were
claimed, according to Slusher (1981, p. 49):
The source for this information is Anderson, J.L., Abstract of Papers,
161st National Meeting, American Chemical Society, Los Angeles, 1971.
In a similar vein, Slusher (1981, p. 26) reports:
In a recent publication it has been reported that decay rates of 14C
may not be predictable as previously believed ... . Dr. John L.
Anderson performed experiments on molecular mono-layers with 14C added.
The emitted radiations did not occur in the patten that classical
theory assumes. Dr. Anderson’s findings were confirmed through
independent research at Atomic Energy Commission Laboratories.
Such irregularities were observed for carbon 14, cobalt 60, and cesium
137. The source for this information is Anderson, J.L. and Spangler,
G.W., “Radiometric Dating: Is the ‘Decay Constant’ Constant?”, Pensee,
p. 31. Even Dalrymple (1984, p. 88) recognizes such irregularities:
Anderson and Spangler maintain that their several observations of
statistically significant deviations from the (random) expectation
strongly suggests that an unreliability factor must be incorporated
into age-dating calculations.
Dalrymple cites the references Anderson, J. L., 1972, Non-Poisson
distributions observed during counting of certain carbon-14-labeled
organic (sub) monolayers, Phys. Chem. J. 76: 3603-3612 and Anderson,
J.L.and G.W. Spangler, 1973, Serial statistics: Is radioactive decay
random? Phys. Chem. J. 77: 3114 - 3121. Such statistical
irregularities could be evidence that the neutrino flux is
influencing the rate of radioactive decay.
Under certain environmental conditions, the decay characteristics of
14C, 60Co, and 137Ce, all of which decay by beta emission, do deviate
slightly from the ideal random distribution predicted by current
theory ... , but changes in the decay constants have not been
Dr. Henke criticized some statements in my article taken from Slusher
about the branching ratio for potassium. Slusher asserted that the
best known value of the branching ratio was not always used in
computing K-Ar radiometric ages. Unfortunately, Dalrymple (1991) says
nothing about the calculation of the branching ratio. He simply gives
the correct value for the K-Ar system. The issue is not just how well
this was known in the past, but which value was actually used, and
whether dates published in the past have been computed with the most
recent value. Often values for constants are standardized, so that
the values actually used may not be the most accurate known. All that
Dalrymple (1991) says is that his ages were all recomputed using the
most accurate values of the constants. This implies that some of them
were originally computed using less accurate values, which is similar
to Slusher’s point.
Dalrymple (1984, p. 91) does discusses the branching ratio. He admits
that Slusher’s statements about it would have been true in the 1940s
and early 1950s, but are no longer true. But he didn’t say when the
correct value for the branching ratio began to be used. Even some
figures from (Faure, Principles of Isotope Geology, 1977) are based on
another constant that is 2 or 3 percent too low, according to
Dalrymple, and so there may be many ages in the literature that need
revision by small amounts.
Dr. Henke criticizes my concern that argon can move in and out of
However, Henke admits that this can happen in some cases. He states
that geologists are aware of this problem, and make allowances for it.
But it is more difficult to remove argon that has deposited on cracks
in the mineral, which can be difficult to see. Dr. Henke referenced
Davis A. Young frequently, but I was not able to find Young referenced
in any of the other sources I examined except Dalrymple (1991).
Dr. Henke states that hornblendes retain argon very well, but then
later says that they can easily absorb excess argon.
Dr. Plaisted wants to give his readers the impression that argon can
readily move in and out of minerals and, therefore, the gas is too
volatile for radiometric dating. Specifically, he quotes one of his
anonymous friends that claims that argon easily diffuses from minerals
(p. 11, also the identical statement is made in Slusher, 1981,
p. 39). Of course, these statements are inaccurate generalizations.
Young (1982, p. 101) notes that argon would more likely adsorb onto
the surfaces of the minerals rather than move into their tight
structures. Geochronologists are aware that excess argon may
accumulate on mineral surfaces and the surface argon would be removed
Geologists also recognize that heating causes argon to leave
minerals, and that dissolved argon in a mineral that does not escape
will become incorporated into it, artificially increasing its K-Ar
age. I will comment more on this below, but a few comments now are
a discussion of radiometric dating from Cornell, we learn (quoting
From another table at the same location, we find that argon loss in
biotite by radial diffusion in an infinite cylindrical crystal of
radius 150 microns, is 1/1000 of a percent in one year at 240 degrees
centigrade, the same percent in 100 years at 200 degrees centigrade,
the same amount in 10,000 years at 160 degrees centigrade, and the
same amount in 10 million years at about 110 degrees centigrade. To lose
one percent in one year requires a temperature of nearly 500 degrees
For a temperature of 300K (27 degrees C), there is no significant
argon loss from biotite. At 600K (327 degrees C), there is a slow but
significant diffusion rate. At 700K (427 degrees C), loss of argon is
Thus the temperature does not have to be very high for argon to move
through rock. This also justifies Slusher’s statements about argon
moving in and out of rocks with ease. However, it does not seem
likely that sedimentary rocks would be this hot very often, except
near lava or magma flows.
But argon does not need to move through all rock in order to influence
radiometric dates, it only has to reach ancient lava flows. This it
can do by following the path of the ancient lava flow itself, coming
up along the path of the magma. As the magma or lava cools, this path
will consist entirely of hot magma or lava, and so the argon will have
a free path, and will continue to enter the magma as it cools. Thus
in many cases, the lava or magma will never completely degas, and
extra argon will end up trapped in the cooled rock. This will result
in artificially increased K-Ar ages.
Many ancient lava flows are relatively flat, in contrast to modern
ones. Also, they appear to have been covered over quickly. The
flatness means that the lava is a contiguous mass, and can still be
reached from the hot magma by a continuous path of hot rock. The fact
that they soon are covered over means that the argon has a hard time
escaping vertically from the lava, so argon coming up from the mantle
will tend to enter the cooling rock. Both facts will tend to produce
artificially high K-Ar ages in these flows which will not be seen in
modern lava flows in the same manner.
Modern lava flows often come down the sides of volcanoes, and thus
become separated from their source by large distances. Also, they do
not get quickly buried by additional sediment. Thus modern lava flows
are not subject to the same mechanism of artificial increases in their
K-Ar ages as are ancient ones. Also, it is reasonable to assume that as
argon leaves the mantle in successive eruptions, the amount of argon
remaining is reduced, so that later lava flows are less susceptible to
such artificial increases in age. The path of magma also becomes
longer for later flows, and the magma probably also is a little
cooler, inhibiting argon flow. Thus later lava flows give younger
Another point to note is that even after it cools, the lava or magma
may still have many cracks in it, permitting argon to flow. This
argon will tend to deposit on the surface of minerals, but with the
passage of time it will tend to diffuse into the interior, even if
only a very small distance. This is especially true as the lava is
cooling. This will make it more difficult to detect this added argon
by the spectrum test described below.
Also, the diffusion of argon in cracks and channels of a mineral is
likely much less temperature-dependent than diffusion through unbroken
regions of the mineral, since diffusion through cracks and channels
simply involves jumps through the air. By a combination of diffusion
through cracks and channels, and short passages through unbroken
regions of the mineral, argon may be able to reach a considerable
distance into the mineral. At low temperatures, this may become the
dominant means by which argon diffuses into a mineral, but the effect
of this kind of diffusion at low temperatures may not be evident until
many years have passed. Thus it may take experiments lasting 50 or
100 years at low temperatures to detect the effects of this kind of
diffusion of argon, which however could be significantly increasing
the K-Ar ages of minerals over long time periods.
Dickin (Radiogenic Isotope Geology, 1995, p. 247) mentions a study
showing that volcanic rocks contain excess atmospheric argon, some of
which cannot be removed by baking in a vacuum. Faure (1986, p. 74)
also states concerning removing atmospheric argon before dating, “The
difficulty can be reduced, if not completely avoided, by the removal
of adsorbed atmospheric argon before the argon is extracted from the
samples. It has been claimed that this can be accomplished by
preheating samples under vacuum or by leaching them briefly with
hydroflouric acid, or both ... . However Armstrong (1978) has
questioned whether atmospheric argon, that has been acquired by
minerals over a long interval of time, can be removed by this
Thus there is some means by which argon from outside can become very
firmly embedded within a rock, and one would expect that the quantity
of this argon would continue to increase over time, giving anomalously
old K-Ar ages. Added atmospheric argon can be detected, because the
ratio of argon 40 to argon 36 for atmospheric argon is 295.5 to one
(Faure, 1986, p. 95), and the amount of argon 36 can be measured. But
argon 40 coming up from the mantle and diffusing into a mineral would
not be detectable in this way, because it has a higher ratio of argon
40 to argon 36. Faure (1986, p. 79) mentions that the ratio of argon
40 to argon 36 in the mantle may be as high as 10,000 or even 25,000
to one. Dickin (1995, p. 247) mentions that atmospheric argon
adsorbed onto a rock can be as high as 70 percent of the total argon,
especially for young material. This shows that rocks can adsorb a
large amount of argon relative to the argon needed to give them old
K-Ar ages, and also suggests that old K-Ar ages can be produced by
external argon from the mantle. Over a long period of time, adsorbed
argon will tend to diffuse into the rock, and thus it will be possible
for even more argon to be deposited on the surface, increasing K-Ar
ages even more.
Concerning excess argon, Faure (1986, p. 72) states:
Generally, excess 40Ar is observed in minerals that have been exposed
to a high partial pressure of argon during regional metamorphism, in
pegmatites ..., or kimberlite pipes. The argon that may either
diffuse into the minerals or may be occluded within them is derived by
outgassing of K-bearing minerals in the crust and mantle of the
Earth. ... The presence of excess 40Ar increases K-Ar dates and may
lead to overestimates of the ages of minerals dated by this method.
Concerning the abilities of various minerals to retain argon, Dr.
However, there is a methodological problem connected with the manner
in which geologists infer the argon-retention abilities of different
minerals. Concerning the suitability of different minerals for K-Ar
dating, Faure (1986, p. 72) writes “The minerals beryl, cordierite,
pyroxene, and tourmaline frequently contain excess 40Ar, while
hornblende, feldspar, phlogopite, biotite, and sodalite contain such
excess 40Ar only rarely ... .” And how is this known? By comparing
the K-Ar dates yielded by such minerals with the expected ones. Thus
the correctness of the geologic time scale is assumed in deciding
which minerals are suitable for dating. For example, concerning the
use of glauconies for K-Ar dating, Faure (1986, p. 78) writes, “The
results have been confusing because only the most highly evolved
glauconies have yielded dates that are compatible with the
biostrategraphic ages of their host rocks whereas many others have
yielded lower dates. Therefore, K-Ar dates of ‘glauconite’ have often
been regarded as minimum dates that underestimate the depositional age
of their host.” Dickin (1995, p. 56) says “in some cases erroneous
glauconite model ages could be increased to near the stratigraphic age
by leaching with ammonium acetate, which is thought to remove excess
loosely bound Rb from the expandable layers of the lattice.” But
leaching with acetic acid had unpredictable effects. So for K-Ar
dating, “the most highly evolved” glauconies are selected to give the
best ages, and Rb-Sr model ages of glauconies can in some cases be
improved by leaching with ammonium acetate, but not acetic acid.
Model ages are based on assumptions about initial Rb and Sr
concentrations, as well. It also appears that near the beginning of
the Cambrian period, zircons are preferred to either K-Ar or Rb-Sr
dating. All of these choices are made in order to obtain dates that
are more in agreement with each other. The result is that radiometric
dating is in danger of being based on circular reasoning.
Once Ar40 is produced by the decay of K40 within a mineral, the ability
of the mineral to retain the argon would depend on the identity of the
mineral and its thermal environment (e.g., Hyndman, 1985, p. 675-676).
Hornblendes, for example, retain argon very well, while biotites are
less effective and feldspars readily leak the gas. Geologists are
familiar with the argon-retention abilities of different minerals and
use these differences to their advantage.
Dr. Henke criticizes my concerns about the effects of heating and water
on K-Ar dating.
Here he confuses heating with metamorphism. The latter involves a
change in the structure of a mineral, but lesser heating may not.
However, heating can cause argon to leave a mineral, and in fact this
is the basis for K-Ar dating in the first place. Faure (1986, p. 123)
verifies that modest increases in temperature of one or two hundred
degrees centigrade can have drastic effects on radiometric dates
without any observable changes in the rocks. Faure (1986, p. 69)
mentions specifically that heating can cause argon loss without any
other physical or chemical changes in the rock. Dr. Henke also
discusses the effect of hot water on rocks, producing alterations in
their structure. Of course, a greater problem is diffusion of water
through a sample that is not hot enough to alter the structure, and
Dr. Henke does not discuss this. A further problem is that water can
cause the transport of dissolved argon, which can then enter other
rocks. He refers to “weathering,” which can only occur for exposed
rocks. Another problem is water traveling underground, which can also
influence the argon content of rocks without weathering, as it is
In several places in his report (for example, p. 6-7), Dr. Plaisted is
concerned that radiometric dates may be unknowingly affected by the
movement of water through the rock or by metamorphic heating.
Fortunately, his concerns are largely unfounded.
Dr. Henke discusses xenoliths and xenocrysts, which are older rocks
that can be carried along with magma. He says that geologists attempt
to avoid these, but he does not say whether this is always possible,
and whether some xenoliths and xenocrysts can be too small to see,
even with a microscope. Dickin (1995, p. 249) mentions that some
subaerially erupted lavas contain inherited argon: “Lavas shown by 14C
dating of wood inclusions to be less than 1 kyr old nevertheless gave
K-Ar ages up to 465 kyr.” A cause that has been suggested for this is
“partially digested crustal xenocrysts” (p. 250).
Dr. Henke discusses my concerns that various methods do not agree on
the phanerozoic. This issue has already been discussed in our earlier
exchanges. Let me just repeat here than many authorities point to
common disagreements between various methods.
Concerning such disagreements, Dr. Henke states:
Along this line, it is interesting that Woodmorappe (Woodmorappe, J.,
Radiometric Geochronology Reappraised, Creation Research Society
Quarterly, vol. 16, September, 1979, p. 102f.) mentions that there
are a number of agreements between Rb/Sr and K/Ar dates that are
considered “wrong” by geologists, who speculate that some other factor
than a true age may be making these dates agree with one another.
Young (1977, p. 190f) provides an excellent example of fossil data
confirming the results of Rb/Sr and K/Ar dates for the Beemerville
Nepheline Syenite in New Jersey. The syenite intruded into the
Ordovician Martinsburg Formation, but it does not intrude into the
overlying Lower Silurian Tuscarora Formation. Cross-cutting
relationships, fossil data, and the geologic time scale indicate that
the syenite should be 425 to 450 million years old. Rb/Sr and K/Ar
dating of the syenite yielded dates of 424 ±20 million years, 436
±41 million years, and 437 ±22 million years, which are
In his first reply, Henke states concerning disagreements between
Unfortunately, Dalrymple (1991) has little or nothing to say about the
phanerozoic. It is also possible that Faul (Faul, H., 1966 Ages of
Rocks, Planets, and Stars, McGraw- Hill, New York.) is not mainly
concerned about the phanerozoic.
I cited Harland et al. (1989), Faul (1966) and Dalrymple (1991), which
contain MORE than just “a few examples.”
Dr. Henke further states:
This quotation seems to miss the point, as I did not question whether
the different results were listed separately or averaged. A more
important issue is the degree to which different methods agree.
Dr. Plaisted (p. 15) recognizes that a majority of radiometric dates
are K/Ar. He then expresses concern that an overreliance on the K/Ar
method may lead to inaccurate dating of samples. ...
The K/Ar results may be averaged, but the literature overwhelmingly
indicates that results from Rb/Sr, U/Pb and other methods would be
listed separately, no matter how they compare with the K/Ar results
(for example, see the table in Dalrymple, 1991, p. 140-141).
Dr. Henke acknowledges that discordant dates exist. A further problem
with anomalous dates is that some dates may not be published if the
articles mentioning them are rejected. I don’t know about geology,
but in many disciplines, publication is a difficult enterprise. Thus
there could be more anomalies than we know about. Some work may not
be published simply due to the time and effort it requires.
Dr. Henke discusses the question of atmospheric contamination of samples,
altering their K-Ar dates:
My point in mentioning this is to show how easily argon can enter
rocks. I realize that atmospheric argon can generally be corrected
for. I am more concerned about contamination from argon that comes up
from within the earth; this argon is almost entirely argon 40, and so
it is nearly impossible to distinguish from radiogenic argon.
Dr. Plaisted (p. 6-7 and elsewhere) raises concerns about atmospheric
Dr. Henke states:
The context of my statement is a catastrophic situation with many
volcano eruptions in a short time, and large quantities of argon 40
escaping into the atmosphere. For short periods of time, there could
be a significantly larger argon 40 concentration near the ground than
elsewhere, making it harder for argon 40 to leave lava as it cools,
and possibly increasing the argon 40 concentrations in other rocks.
Dr. Plaisted (p. 14) even suggests that argon concentrations in the
atmosphere would concentrate near the ground. Of course, such a layer
would not form because of atmospheric mixing by winds and because the
atomic weight of argon is not that much greater than N2 or O2, the
dominant gases in air.
Dr. Henke states:
It wasn’t clear to me whether this was based on evidence or
conjecture. Argon can travel through fractures, and also be
transported by water. It’s also not clear to me how well we
understand the structure of fractures and cracks in the crust, to
understand how argon will circulate. Furthermore, argon may take
the path of least resistance, but in some cases it could be trapped
underground and spread out into a wide area. Also, if the sediments
were hot enough in places, argon could diffuse through them fairly
easily, as mentioned above.
Young (1982, p. 100-101) refutes Slusher’s claims of crustal
contamination by argon gas. Because argon is inert, the gas would tend
to diffuse through large fractures in the crust rather than into
minerals or small fractures within the minerals. That is, the argon
would take the path of least resistance.
Dr. Henke states:
However, an article by Snelling at
The Institute for Creation Research site lists quite a few
historic volcanoes with excessively large K-Ar dates. This is proof
that the magma contains large amounts of excess argon, which in these
cases was not able to escape.
Dalrymple (1984, p. 81-82; 1991, p.91-92), on the other hand, notes
that historically erupted volcanics rarely contain excess argon.
Dr. Henke states:
It is difficult for me to find the statements to which Dr. Henke is
referring, since my copy of the article does not have his pagination.
I don’t recall the statements to which he refers.
Dr. Plaisted (p. 2, 13) might claim that the excess 40Ar could have
formed from increases in the 40K decay rate in the dense and hot
interiors of stars. This suggestion is not supported by isochrons (as
Dr. Plaisted suggests on p. 13), meteorite chemistry, or the chemistry
of the stellar atmosphere.
Dr. Henke states:
Dalrymple (1991) says nothing about this, but in any event, my main
concern is not the age of the earth. Dalrymple (1984, p. 83) says
that the amount of argon 40 in the atmosphere could have been produced
in 4.5 billion years if there are 170 ppm of potassium in the earth, a
reasonable amount. Dalrymple assumes that half of the radiogenic
argon 40 would be released into the atmosphere, which seems to be an
arbitrary assumption. Perhaps there is much more argon 40 in the
mantle than in the atmosphere. Slusher (p. 39) cites (Cook, Melvin
A., Prehistory and Earth Models, London: Max Parrish and Co. Ltd.,
1966, p. 67) in support of his statement. It is also possible that if
the speed of light were faster in the past, the decay rate might have
been faster as well, producing much argon 40.
Dr. Plaisted (p. 10-11) cites an anonymous friend (whose statement
turns out to come word for word from Slusher, 1981, p. 39) who claims
that there is too much 40Ar in the atmosphere for the Earth to be 4.5
billion years old.
The whole question of how much argon 40 and argon 36 there is in the
atmosphere and in the mantle, is discussed in detail in Dickin (1995,
pp. 287-293). Faure (1986, pp. 79-80) also discusses this issue, and
mentions some work supporting the idea that the mantle lost 95 percent
of its argon in a catastrophic event about 4.45 billion years ago.
This raises the question as to what kind of an event this could be,
especially since gravity would tend to attract argon to the earth, and
argon is highly soluble in molten rock. If one assumes that most of
the argon 36 present when the earth formed was in the mantle, and that
this argon 36 either left the mantle at a constant rate or that most
of it is still there, then it must be the case that the amount of
argon 40 in the mantle is many times larger than in the atmosphere.
These natural assumptions would justify Slusher’s statement that there
is far too much argon 40 to have formed by radioactive decay from
potassium in 4.5 billion years. This could be evidence that the rate
of decay was much larger in the past.
Dr. Henke states:
The quote from Evernden et al. (1964) stated:
In another example from a web site, Dr. Plaisted (p. 20-21) quotes
Evernden et al. (1964), which states that some devitrified (altered)
glasses of known ages gave results that were too young. Both chlorites
and devitrified glasses are alteration products. Therefore,
unreasonable K/Ar dates are expected with these materials because the
alteration events would have caused the argon to move in or out of the
materials. Obviously, geochronologists would avoid these materials if
they wanted quantitative dates.
Thus the evidence is that the devitrification took place at about the
same time as the deposit, which contradicts Henke’s scenario.
Some gave virtually zero ages, although the geologic evidence
suggested that devitrification took place shortly after the formation
of a deposit.
Dr. Henke further states:
However, Dr. Henke is not giving the whole story here. It follows
from the mathematical properties of isochrons that if an isochron,
even with carefully selected samples, gives a Rb/Sr age of 34 billion
years, then at least one of the samples must have a Rb/Sr age of 34
billion years or larger, and probably at least one more has a Rb/Sr
age nearly this large or larger. In fact, from Dalrymple (1984,
p. 79), three of the 8 samples have Rb/Sr ages of nearly 34 billion
years or larger. Thus we still have a serious anomaly to contend
with. Whether this large age is due to leakage of Rb, excess Sr, a
different decay mechanism, or a faster decay rate, the same factor
could be making other Rb/Sr dates too large, as well. Of course, the
first two of these processes probably would not produce false
Among the citations of Woodmorappe (1979), Dr. Plaisted (p. 17) refers
to a ridiculously old Rb/Sr “date of 34 billion years.” Dalrymple
(1984, p. 77f) discusses the origin of this “date” and denounces
Woodmorappe (1979) for creating this fictitious date by misreading an
isochron plot for the Pahrump Group Diabase in California (see the
original source: Faure and Powell, 1972). The diabase shows a terrible
scatter on the 87Sr/86Sr versus 87Rb/86Sr plot and does not provide a
Rb/Sr date. Radiometric dating on related rocks, however, indicates
that the diabase is about 1.2 billion years old. On the badly
scattered diagram, two age-meaningless “reference isochrons” are drawn
to bracket the badly scattered data. One reference isochron is “1.09
billion years.” The other is a “34 billion years.” These reference
isochrons have no time meaning. They are simply drawn in as a guide
for the reader in much the same way that a flying pilot may refer to
the position of another plane as being between “9 and 11 O’Clock” from
her position. In this case, the “9 to 11 O’Clock” has no time meaning,
but simply indicates that the other plane is from the left to the
front left of the pilot.
Dr. Henke states:
What I am looking for is a study in which samples are chosen in a
statistically unbiased manner and sent to laboratories without
information about where they are found, to determine whether the dates
are in acceptable ranges and whether different dating methods agree.
Just to give one example does not settle the issue.
In Lanphere and Dalrymple (1965), 55 laboratories were sent a
muscovite standard for dating. The average K/Ar date for the muscovite
was 83.0 million years and the average Rb/Sr date was reasonably close
at 85.7 million years. Interlaboratory standard deviations were only
1.2% for the K/Ar dates and 2.8% for the Rb/Sr dates. These excellent
results refute creationist claims that K/Ar and Rb/Sr methods are
inconsistent or imprecise.
Concerning the dating of meteorites, Henke states:
This does not answer my question, which referred at least in part to
dates obtained by a simple daughter-to-parent ratio. Dalrymple (1991)
does say that many ages for meteorites are “model ages,” which are
computed by making assumptions about initial amounts of daughter
product. Such assumptions are also necessary for the Pb-Pb method of
dating. For meteorites, there is a good basis for making such
assumptions. Also, Dalrymple (1991) gives impressive agreements
between different isochron methods on meteorites, which support a
roughly 4.5 billion year age without any assumptions on initial
amounts of daughter product. Henke refers to this in his second
Dalrymple (1984, p. 82) states that knowledge of the initial amount of
the daughter product is not even needed to obtain reliable ages with
This could be explained by some mixing process or an increase in the
decay rates, as mentioned above, but the simplest explanation is that
the meteorites are very old. However, in order to date the earth, one
needs an isochron which includes a point from the earth. This is more
difficult, and this is the isochron that I saw on the talk.origins
FAQ, which involved a much smaller number of meteorites. Also, many
of the meteorite dates I saw in the FAQ were apparently simple
daughter-to-parent ratio ages.
Dalrymple (1991) lists more than just a “small number of meteorites.”
For example, tables in Dalrymple (1991, p. 287-289, 291) list numerous
results. Specifically, Figure 6.9 on p. 286 contains the results of 94
radiometric ages of 69 meteorites. Table 6.3 on p. 287-289 contains
the results of 240 radiometric dates on 42 meteorites. None of these
results are only a few thousand years old. For further details, see
Dalrymple (1991, chapter 6).
It is also remarkable that so many different isochron-based dating
schemes, even on the same meteorite, often yield roughly the same 4.5
billion year age. This is true for Rb-Sr, Pb-Pb, Sm-Nd, Lu-Hf, and
Re-Os dating methods, as well as the Ar-Ar spectrum method. This is a
case where different methods agree without making assumptions about
initial amount of daughter product. This either indicates a true age,
or a change in the decay constants. I would like to know how often
this is true on the phanerozoic. How often does one have two or three
different isochrons on the same system yielding very similar dates?
It is also important that the concentrations of parent substances are
linearly independent, to preclude mixings. Such a multiple-isochron
agreement is fairly convincing, but the failure to find such isochrons
likewise casts doubt on the ages obtained. If radiometric dating is
accurate on fossil-bearing rocks, there should be an abundance of such
agreements between different isochrons on the same systems, and they
should yield the conventionally accepted ages. A change in the decay
constants on the phanerozoic seems less likely, since it could
radically affect the properties of matter, and be harmful to life.
Another reliable technique mentioned by Dalrymple (1984) is the U-Pb
concordia-discordia method, which is valid even for many open systems.
This technique requires assumptions about lead and uranium loss, and
seems to give good evidence of a reliable date (relative to decay
constants), especially when there is agreement with other methods
(such as isochrons) on the same system. However, Dickin (1995,
pp. 105-118) mentions that both lead and uranium are mobile, and that
“rocks with complex geological histories ... can yield discordia of
high statistical quality which nevertheless yield erroneous ages”
I mentioned the presence of excess argon 40 in a sample as a problem
leading to artificially old K-Ar dates. Henke states in a reply to
me, concerning the problem of detecting excess argon,
It is possible that such isochrons are not often done. One cannot
always use an isochron, since many minerals may have about the same K
and Ar40 concentrations, and there may be some fractionation of argon
among the minerals. It’s not clear to me if this three dimensional
plot always works, and how often it is used. I was not able to find
any mention of it in Faure (1986) or Dickin (1995). Dickin (1995, p.
116) did mention such a technique for U-Pb dating.
Why not determine the initial Ar isotopes with K/Ar isochron methods?
Also see Mussett and McCormack (1978) on using a three dimensional
plot to distinguish initial and excess argon in K/Ar dating.
Henke further states in his reply to me,
It is true that by using additional isotopes (if they are sufficiently
abundant and do not fractionate), one can often detect mixings of
multiple sources. My point was that the usual mixing test can only
detect two sources. But since these multiple mixing tests are more
difficult and expensive, they may not be done very often. One also
has to know which isotopes to examine. I was suprised that Dalrymple
(1991) said nothing about mixings invalidating isochrons. Dalrymple
(1984, p. 85) cites a source (Kramer, Arndts, and Overn, Bible-Science
Newsletter, 1981) that applied the mixing test to 18 Rb-Sr isochrons
from the literature and found that nearly all of them had correlations
suggesting a mixing. Dalrymple goes to great lengths to explain this
away, but I think this figure is very telling, and find his
explanations unconvincing. It is also remarkable that we have a test
for mixing, which is commonly cited in support of the accuracy of
radiometric dating, but when it gives contrary results, it is simply
ignored. Dickin (1995, p. 44) states,
Dickin (1995, p. 180-199) mentions a number of other isotopic
techniques that are used to detect mixing between multiple sources.
Dickin suggests that mixings may contribute to such isochrons. It
seems reasonable, then, that mixings may be affecting all Rb-Sr
isochrons in igneous rock.
It is a fundamental assumption of the mantle isochron model that
neither isotope nor elemental ratios are perturbed during magma ascent
through the crust. However, it is now generally accepted that this
assumption is not upheld with sufficient reliability to attribute age
significance to erupted isochrons.
This example is given to show that a mixing of three sources cannot
be detected by the usual two sources test. It is not intended to be
natural, but to demonstrate a mathematical fact. There is a lot of
flexibility in the design of such examples, as I indicate, and it is
reasonable to assume that some of these examples would be natural.
It’s the responsibility of the geologist to show that such mixings
have not occurred.
Your hypothetical example in “More Bad News for Radiometric Dating” is
often hard to follow, but it is clearly invalid.
In response to the disagreements between different dating methods,
The problem with this approach is that it leaves ample room for the
exercise of subjective judgment and evolutionary assumptions. Also,
Dalrymple (1991) says essentially nothing about the phanerozoic, and
thus gives little evidence of the accuracy of the conventional dating
scheme on fossil-bearing rocks. Dalrymple (1984, p. 125) also says
little about the phanerozoic, except to note that over 100,000 dates
have been calculated, and only a few percent (p. 76) are anomalous. I
treated this issue of percentage of anomalies in considerable detail
in my original “Radiometric Dating Game” article.
To really understand what’s going on you have to sample the recent
works of many different authors. You have to follow arguments between
experts on different issues and see where they go. Overall, the
geologic time scale is in great shape. Yes, scientists are still
making minor adjustments. However, it’s clear from Strahler (1987),
Dalrymple (1991), etc. that the creationists have lost.
It is interesting that Woodmorappe (1979) gives a number of cases in
which standard geological tests are ignored. For example, dates may
be accepted even when there is evidence of weathering, and rejected
when there is not. There may be evidence of heating, but the date may
be accepted, and there may be no such evidence, but a hypothetical
heating event is assumed anyway. The same applies to the Ar/Ar
spectrum test for initial or adsorbed argon 40. If geological tests
are not being applied consistently, one wonders what value they
Let me clarify the problem with excess argon. There is
an excellent discussion of radiometric dating from Cornell at Tim
Thompson’s radiometric dating page. It gives the diffusion equation
for argon escaping from a rock as it cools. The rate of diffusion is
proportional to the gradient of argon concentration, and increases
rapidly with temperature. Suppose the partial pressure of argon 40 in
the environment is p. Suppose the partial pressure of argon 40 in
lava or magma is initially at least p, as it cools. Then the partial
pressure of argon 40 in the magma will never decrease below p; excess
argon 40 will remain dissolved in the lava or magma as it cools. This
argon 40 will then be trapped within the resulting rocks and lead to
artificially old K-Ar dates. Now, the problem with this is that this
excess argon 40 will probably be deposited as single atoms of argon
distributed evenly within the sample. This makes it very difficult or
even theoretically impossible to distinguish this excess argon 40 from
argon generated by radioactive decay. This will make the sample
appear artificially old right away.
Even if crystals exclude
argon as they form, argon will rapidly diffuse into them as the lava
cools, by the diffusion equation mentioned above.
A similar problem can occur if the excess argon 40 dissolved within
lava or magma is not able to escape, due to rapid cooling or
subsequent deposits of sediment or other lava on top.
It is possible that in some cases an isochron might be able to detect
such initial argon 40, but this can only happen if the potassium
concentration varies significantly within the sample. It is not clear
to me, also, how often such a test for initial argon 40 is performed.
And of course, such isochrons can be falsified by mixings or other
There are spectrum tests for adsorbed argon involving Ar-Ar dating;
basically, one can see whether the argon 40 is concentrated near the
surface of the sample or near the interior. The former would
indicated adsorbed argon 40, which would not give a true age.
However, this test would not indicate excess argon 40 present during
cooling. Faure (1986, p. 104) verifies that biotites with excess
argon can have a flat spectrum, which makes this excess argon
impossible to detect. Faure (p. 101) even implies that the
reliability of the Ar-Ar spectrum test is now being questioned.
It seems reasonable to me that this is a uniform problem with K-Ar
dating. To me the geological evidence suggests catastrophic
conditions and rapid formation of the sedimentary layers in the past.
Thus the lava might have been covered before the excess argon was able
to escape. Or the lava might have cooled quickly, due to rainfall.
It only needs to cool to about 500 degrees centigrade or less to trap
most of the argon, at least for biotite.
As I mentioned before, one sometimes finds significant argon 40 in a
rock and no potassium at all, as mentioned in Snelling’s article.
This shows that excess argon is entering these rocks by some means,
and calls K-Ar dating into question.
Excess argon could even cause different minerals in a given formation
to yield similar K-Ar ages, since they all might have similar
concentrations of K, approximately equal to its abundance in the
earth’s crust, and similar concentrations of argon 40, due to the
partial pressure of argon 40 being similar during cooling. Even
sedimentary minerals might have a similar K-Ar age for the same
reason. Also, lava (magma) that cooled within the earth is likely to
have artificially old K-Ar ages, since the enclosed excess argon 40
might have a more difficult time escaping.
One sedimentary mineral of particular importance for K-Ar dating
is glaucony. The following message from a talk.origins participant
illustrates its importance:
Concerning glauconite, Dr. Henke says
For example, Plaisted’s “explanation” for the correlation of isotopic
age with vertical position in the geologic column is essentially that
excess argon would have existed in lavas in greater quantity early in
the Flood, and decreased as it was outgassed over time. Had Plaisted
actually bothered to look at the data (e.g., Harland et al. “A Geologic
Time Scale 1989”) he would have found that more than half of the dates,
especially for mesozoic-cenozoic parts of the column, are glaucony
(a sediment composed largely of animal fecal matter). Glaucony did
not come from a “magma chamber,” so Plaisted’s explanation cannot
possibly cover the majority of ages on the younger parts of the column.
The fact that glauconies are unreliable is significant, since they
provide such a large part of the dates for the mesozoic-cenozoic parts
of the geological column. Faure (1996, p. 71) also lists glauconies
as being only “sometimes useful” for K-Ar dating.
Of the 429 or so “anomalous” dates in Woodmorappe (1979), 94 (21.9%)
involve illite and glauconite, which (because of their crystalline
structures) are notoriously unreliable in giving K-Ar dates.
Geochronologists know that illite and glauconite K/Ar dates are often
untrustworthy. K/Ar ages from these minerals are often published to
better understand the types of conditions that cause them to produce
unreliable dates rather than to assign actual ages. Woodmorappe is
clearly misusing illite and glauconite dates to simply pad his list.
Glauconies are formed in seawater from a variety of materials, and
incorporate potassium from the seawater (Faure, 1986, p. 78). Faure
states, “The uncertainty about the interpretation of K-Ar dates of
‘glauconite’ has reduced their usefulness in dating sedimentary rocks”
(page 78). The process of their formation gives a ready mechanism for
their K-Ar ages, namely, the incorporation of argon 40 as well as
potassium from the seawater. We can assume that as a result of a
global catastrophe, the oceans were highly enriched in argon 40 in the
past, and that the concentration of argon 40 gradually decreased over
time, due to its diffusion into the atmosphere and due to a smaller
amount being released into the seawater. Therefore older glauconies
would absorb more argon 40 from the seawater, resulting in old K-Ar
dates for lower strata which become progressively younger for higher
strata. Another factor in this direction is that older glauconies
have more time to absorb argon 40.
Let me summarize some of the reasons for questioning the reliability
of K-Ar dating:
Finally, I want to comment on the circumstances of the interchange
with Dr. Henke. During most of our interchange, I was not aware that
it would be published on talk.origins. Now it has been
web-immortalized on a radiometric dating web page. I was not informed
that this exchange had been posted there. In addition, the complete
exchange was not posted, but only a portion of it. I do thank
Tim Thomson for the courteous and professional manner in which he has
interacted with me, and that he has included the rest of my exchange
with Dr. Henke.
It is difficult to detect argon 40 present during cooling.
Some minerals contain argon 40 but no potassium, so this indicates
excess argon 40, which in the presence of potassium leads to artificially
Many historical volcanoes give K-Ar dates that are much too old, even
if the reasons for this are understood.
At least one authority sent me email that K-Ar dating is inaccurate.
Let me briefly comment on a couple of other articles at Tim Thompson’s
page. One by Don Lindsay,
Are Radioactive Dating Methods Consistent With Each Other? shows
that 5 craters give similar dates, three of them dated by three
different radiometric methods, and two by stratigraphic ones. This is
at least close to what I am looking for. However, it would be better
to date all five craters by all four different methods, and see what
the agreement is. It is also possible that each crater gives a
scatter of dates, and the best ones were selected. Furthermore, it is
possible that the craters were chosen as those for which the dating
Fission track dating is also mentioned in Tim Thompson’s web page. It
is interesting that Faure (1986, pp. 345-6) mentions that fission
track dating is calibrated using rocks of “known” ages. If these
“known” ages are incorrect, then fission track dating is also
I also comment on the article
Breakthrough Made in Dating of the Geological Record at the same
article shows an agreement between argon-argon dating and astronomical
time scales which is used to calibrate sedimentary deposits. This is
very interesting, but the assumption is that the precession of the
earth’s axis has been constant for many thousands of years. If there
were a recent global catastrophe, this precession might have been
severely altered, invalidating this calibration. In general,
uniformitarian assumptions such as this were foreseen in the Bible:
And Dalrymple (1984, p. 104) even defines uniformity, following
Hubbert (1967, p. 31), by
Knowing this first, that there shall come in the last days scoffers,
walking after their own lusts, and saying, Where is the promise of his
coming? for since the fathers fell asleep, all things continue as they
were from the beginning of the creation. For this they are willingly
ignorant of, that by the word of God the heavens were of old, and the
earth standing out of the water and in the water; whereby the world
that then was, being overflowed with water, perished.
2 Peter 3: 3-6.
However, the assumption of global catastrophes in the past calls such
calibrations of dating methods into question.
(1) We assume that
natural laws are invariant with time
(2) We exclude hypotheses of
the violation of natural laws by Divine Providence, or other forms of
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