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_Comments on David Plaisted's "The Radiometric Dating Game" - Part 2_

Further Reply to David A. Plaisted's Comments on Radiometric Dating
Kevin R. Henke, Ph.D.
December 28, 1998
_________________________________________________________________

The following text was posted to the talk.origins newsgroup on
December 28, 1998. It consists of David Plaisted's response to Kevin
Henke's [1]original critique, with additional comments in response
from Henke. All contents are © 1998,1999 by Dr. Kevin R. Henke. The
text has been reformatted into HTML, with live links in place of text
URLs where appropriate. I have not altered the content in any
substantial way.

Dr. Henke is currently a post doctoral fellow in the [2]Department of
Chemistry at the [3]University of Kentucky. [4]Dr. David Plaisted
earned his PhD in computer science from [5]Stanford University in
1976, and is currently Professor of [6]Computer Science at the
[7]University of North Carolina, Chapel Hill.

Text was provided by Dr. Kevin Henke, HTML formatting by Tim Thompson.
_________________________________________________________________

For the readers of Talk.origins and others:

In early December, 1998, I commented on David A. Plaisted's
anti-radiometric dating article "[8]The Radiometric Dating Game".
David kindly replied to my critique on December 15, 1998. Below I
reply further to David's comments of December 15, 1998. My original
critique, from early December 1998, is in [9]Part 1.

DAP = comment by David A. Plaisted, creationist.
KRH = comment by Kevin R. Henke, geologist and advocate of radiometric
dating.

_DAP:_ I was not aware that many of my arguments originated from
Slusher. I appreciate this clarification.

_KRH:_ You're welcome. However, I don't think that Mr. Slusher
would appreciate how one of your anonymous email friends misused
his 1981 book. There were no quotation marks around the word for
word statements in your report on pages 4-5, 10-11 in [10]The
Radiometric Dating Game and Slusher (1981, p. 38-40) was never
credited. Because it is difficult to check the reliability of
anonymous emails, I don't think that it's a good idea to use them
in reports. Anonymous sources are of questionable quality and they
cannot be checked or verified by your readers. Certainly, you
wouldn't want to be associated with anonymous contacts that
possibly plagiarize the works of their fellow creationists.

_DAP:_ Dr. Henke criticizes my stand on the age of the earth. My main
concern is not with the age of the earth, but with the strata of the
Cambrian period and later.

_DAP:_ I appreciate the technical clarifications about lava and magma
and about mica, but these do not affect the main argument.

_DAP:_ Dr. Henke is right that my discussion of a change in decay
rates is speculation. But a tremendously large number of neutrinos
might not have much of an effect on most elements, except to cause
radiactive elements to decay faster, since neutrinos interact
principally (but very weakly) with nucleii.

_KRH:_ If a large number of neutrinos affected radioactive decay,
why wouldn't they also disrupt the nuclei of stable isotopes? If
neutrinos disrupted atomic nuclei, what effect would that have had
on terrestrial life forms? Again, we have NO evidence that
radioactive decays rates have been significantly affected by
neutrinos, neutrons or anything else. Arguments about changes in
radioactive decay rates have no scientific support and are just
wishful thinking by creationists.

_DAP:_ I realize that neutrons would not have been responsible, rather
neutrinos. Another proposal by some creationists is that the physical
constants have changed, allowing for a more rapid decay rate in the
past. But if the decay rates have not changed, it would not bother me.

_KRH:_ Creationist Setterfield has argued that the speed of light
has decayed since the "creation a few thousand years ago." If the
speed of light has changed, then radioactive decay rates and other
physical constants would also be changed. Setterfield's arguments
are so flawed that even some of his follow creationists tore them
apart in a couple of 1988 issues of the "[11]Creation Research
Society Quarterly." See:

Aardsma, Gerald E., 1988, "Has the Speed of Light Decayed
Recently?"
[12]Creation Research Society Quarterly, vol. 25, #1, June, 1988,
p. 36f.

Humphreys, D. Russell, "Has the Speed of Light Decayed Recently? -
Paper 2"
[13]Creation Research Society Quarterly, vol. 25, #1, June, 1988,
p. 40-45.

_KRH:_ There are also other comments and articles from
Setterfield's creationist critics in the September 1988 issue of
the "[14]Creation Research Society Quarterly". Also see Impact
#179, [15]Has the Speed of Light Decayed?, by Aardsma.

_DAP:_ The problem with decay rates and branching factors is discussed
nicely in a recent issue of [16]Science (December 4, 1998, p. 1840).
The problem is not that better values are not always known, but that
even when they are known, they are not always used. But still, I
appreciate the clarifications and updates provided by Dr. Henke.

_KRH:_ Nothing in Renne et al. (1998a) gives any comfort to
creationists. The article is dealing with errors of about 3% and
less.

_DAP:_ Dr. Henke states that the argon retention abilities of minerals
are well known. There are many variables involved in a supposed
millions of years history, and the analysis is done under the
assumption that such a history of life is correct. Without knowing the
ages of the rocks, it is hard to see how one can correctly account for
all of these variables. The same applies to the effects of water.

_KRH:_ A rock with a long history has not necessarily experienced a
lot of events or "variables." It's history may have been very quiet
and boring. Some Precambrian rocks, like those in the subsurface of
central North America, have no chemical or mineralogical evidence
to indicate that they have been heated or otherwise altered in 2.5
billion years. This is especially true if they're dense and
unfractured plutonic rocks that have never been exposed to
oxidizing conditions. Yes, as surprising as it sounds, nothing
significant may happen to rocks for millions or even billions of
years. Many of these ancient rocks are located in the center of
continents far away from subduction zones and other active
boundaries of tectonic plates.

_KRH:_ How do analytical chemists that measure Pb, Sr, Rb, etc.
allow their results to be determined by any assumptions about the
"history of life"? The chemists would need to make sure that the
zircons, feldspars, biotites or whatever minerals that they're
analyzing are unaltered. They would then need to properly analyze
the samples. But they don't need to know if the samples came from
the Precambrian Canadian Shield of western Ontario or a Tertiary
granite from New Zealand. The chemists might ask the geologist if
they should expect a lot of daughter product or not. Having a rough
idea of what to expect may be important in the detection efforts or
to speed up their work. However, I would think that to keep biases
out of the analysis that the geologist would tell the chemists as
little about the samples and their origins as possible. I know that
with the recent controversy about "life" in a Martian meteorite,
the geologists did not tell many of their subcontracting analytical
chemists that the samples supposedly came from Mars.

_KRH:_ Again, if water has greatly disrupted the isotopic chemistry
of a rock sample, in all probability, the water would also
noticeably change the mineralogy of the sample. Altered rocks are
usually easy to identify.

_DAP:_ Along this line, it is interesting that I received e-mail from
an author of a book on radiometric dating from an evolutionary
viewpoint. He stated that K/Ar dating and Rb/Sr dating are no longer
considered accurate, but that dating based on zircons is now
emphasized.

_KRH:_ This is another anonymous email. Instead of using anonymous
emails, we should be looking at any peer-reviewed documents from
your anonymous contact that summarize his/her skepticism of
radiometric dating methods. Again, why should we trust any source
that we can't verify? Your "evolutionary" author's statement sounds
like something that Alan P. Dickin might say. Dickin (1995, p. 53),
interestingly, has been very critical of Rb/Sr isochron dating.

_DAP:_ Dr. Henke admits that xenoliths can be hard to see. This is
therefore another possible problem with radiometric dating.

_KRH:_ Xenoliths can be hard to see in the field, but they're often
not a problem if you use thin sections and some other laboratory
work. As creationist Austin states in "[17]Excess Argon within
Mineral Concentrates from the New Dacite Lava Dome at Mount St.
Helens Volcano", a number of different xenolith lithologies have
been found at his Mt. St. Helen's field site. However, except for
gabbro xenoliths, Austin's report gives no indication that he
avoided other, less noticeable, xenoliths. Furthermore, it is clear
from [18]his Figure 4 that he improperly sampled and dated zoned
feldspars, which may partially explain his old dates. So, the real
question is: why does Austin make sampling mistakes that most other
geologists would know enough to avoid?

_DAP:_ Dr. Henke gives some examples where different methods agree.
But what is needed is a comprehensive double-blind study, not a few
examples.

_KRH:_ I cited Harland et al. (1989), Faul (1966) and Dalrymple
(1991), which contain MORE than just "a few examples." Before you
claim that they only contain a "few examples," you should look at
the page after page of data tables in these references. If Harland
et al. (1989) doesn't contain enough examples for the Phanerozoic,
try these references:

Odin, Gilles S., 1982, "Numerical Dating in Stratigraphy," parts 1
& 2, John Wiley & Sons, Chichester, 1040p. This two volume set
contains numerous examples of reliable Phanerozoic radiometric
dates.

Tucker et al., 1998, "New U-Pb zircon ages and the duration and
division of Devonian time," Earth and Planetary Science Letters,
1998, v. 158, p. 175-186. Tucker et al. (1998) compare U/Pb dates
to fossil data and other calibrations of the Devonian time period
from the literature.

_KRH:_ The following references report on interlaboratory studies
of numerous K/Ar and 40Ar/39Ar mineral standards:

Samson and Alexander, 1987, "Calibration of the Interlaboratory
40Ar-39Ar Dating Standard, Mmhb-1," Chemical Geology (Isotope
Geoscience Section), v. 66, p. 27-34. This article discusses the
calibration of a hornblende in a syenite from southern Colorado.
The age of the hornblende is about 520.4 ± 1.7 million years and is
based on 58 potassium and 54 40Ar* analyses from more than 18
different laboratories.

Sudo et al., 1998, "SORI93 biotite: A New Mineral Standard for K-Ar
Dating," Geochemical Journal, v. 32, p. 49-58. Sudo et al. (1998)
describe the development of a new K/Ar standard from a 92.6 ± 0.6
million year old Japanese granodiorite.

Renne et al., 1998b, "Intercalibration of Standards, Absolute Ages
and Uncertainties in 40Ar/39Ar Dating," Chemical Geology, v. 145,
p. 117-152. This article discusses numerous analyses on several
different mineral standards. For example, the Fish Canyon sanidine,
alone, was analyzed 380 times.

Other K/Ar and 40Ar/39Ar mineral standards include: P-207
(Dalrymple and Lanphere, 1969); Bern4M and Bern4B (Jaeger et al.,
1963 and Flisch, 1982); Hb3gr (Turner et al., 1971); and LP-6
(Ingamells and Engels, 1976; Odin et al., 1982).

_DAP:_ It is, I agree, possible to correct for atmospheric argon in
K/Ar dating. But this does not apply to the argon diffusing up in the
earth's crust, which has a different isotopic composition.

_KRH:_ 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.

_DAP:_ Dr. Henke's treatment of argon contamination in the crust is
speculative, even though he cites some sources. How can we know for
sure what is going on down there?

_KRH:_ There have been NUMEROUS field and modeling studies of Ar in
the Earth's interior (as examples, I found these studies just
looking through a few recent journals: Albarede, 1998; Kamijo et
al., 1998; Tolstikhin and Marty, 1998; Winckler et al., 1997; Marty
and Humbert, 1997; and Morgan, 1998). Also see Dickin (1995, p.
287-293); Chamorro-Perez et al. (1996), Trieloff et al. (1997),
Jackson (1998, p. 169-171) and Faure (1986, p. 79-80)). You can
read this literature to get an idea of what we know about the
movement of argon in the upper mantle over time. Contrary to
creationist claims, scientists know quite a lot about argon in the
Earth's interior. In addition, K/Ar isochron dating is often
helpful in overcoming difficulties with determining irregular
initial Ar isotope values. Examples from the literature, such as
Harland et al. (1990) and Dalrymple (1991), show that K/Ar dates
are often consistent with U/Pb and Rb/Sr dates.

_DAP:_ He admits that some rocks (hornblendes) can be affected in this
manner and give too old dates. How do we know this is not a more
general problem?

_KRH:_ First of all, hornblende is a mineral and not a rock. We
know that it's not a more widespread problem because we understand
the crystalline structures of hornblende, micas, and other minerals
that are commonly used in K/Ar dating. Scientists have been
studying the interactions between argon and different minerals for
decades and they know where the argon can hide in the crystalline
structures of these minerals. You can read the literature to find
out how argon interacts with the minerals that are commonly used in
radiometric dating. Begin by looking at the table of closure
temperatures in Harland et al. (1990, p. 74) and their references.
The references should provide information on how argon interacts
with different crystalline structures. McDougall and Harrison
(1988, chapter 5) provide laboratory results and detailed
mathematical explanations of argon diffusion through various
minerals, including biotite, hornblende, muscovite and feldspars.

_DAP:_ Again, Dr. Henke brings up the age of the earth question, which
is not my concern here. But I appreciate his information about the
amount of argon in the earth.

_DAP:_ Much of Dr. Henke's criticism is directed at John Woodmorappe
and not at me. I do not wish to comment on this, except to express
appreciation for the explanation of the 34 billion year isochron. But
I would like to hear John Woodmorappe's side of the story.

_KRH:_ In disputes between authors, it's always a good idea to look
up all of the original references that are at the center of the
dispute. That is, look up the references in Woodmorappe and compare
what they say with what Dalrymple (1984) and Woodmorappe (1979,
1985) CLAIM that they say.

_DAP:_ Dr. Henke admits that chlorites and devitrified glasses can
produce inaccurate K/Ar dates. Why is this believed?

_KRH:_ Again, we understand the chemical and structural changes
that occur as glass devitrifies or as biotite or other minerals
convert to chlorite. We recognize that these structural changes may
result in the release of argon or its absorption. Look at Deer et
al. (1972-1977) or another mineralogy book. You can see where the
argon could be located in hornblende, biotite or chlorite crystals
and how these locations could be disrupted or formed as biotite
converts to chlorite. Volcanic glass is full of random bubbles that
may contain argon. As the glass devitrifies (breaks down) these
bubbles would be opened and their contents released. This is not
difficult to understand. For further discussions, see McDougall and
Harrison (1988, p. 33) and their references.

_DAP:_ The dates do not agree with the expected values, so some
explanation is found.

_KRH:_ So, what's wrong with looking for an explanation for any
observation? Sometimes, scientists think that they have an
explanation for an observation, but investigations show that they
are wrong. Geologists always try to explain their results, whether
their results are expected or a complete surprise.

_DAP:_ To me, it is reasonable to assume that all of the old dates for
fossil-bearing rock are unreliable.

_KRH:_ You can call them "unreliable," but that doesn't answer the
question: why are they unreliable? Why is it "reasonable" to call
all Phanerozoic radiometric dates unreliable? Do you call all
clocks unreliable, just because a few of them don't keep good time?
How do you explain the consistent results in Harland et al. (1990),
Hirschmann et al. (1997) and the other references that I mention in
this reply? If a K/Ar analysis of a chlorite gives a date of 17
billion years, both creationists and geochronologists would be
skeptical of this result. The scientist would try to find out why
the date is bad. Geochronologists would look at the crystalline
structure of the chlorite. Chemical comparisons may be made between
the chlorite and any surrounding minerals. Laboratory studies would
look at how temperature and fluids may affect the movement of argon
in and out of the chlorite. Field investigations may also reveal
important information about the history of the chlorite and its
host rock, such as metamorphic events, faulting, or pronounced
weathering. However, is the creationist going to do any science or
will the creationist just quote Genesis, walk away, and solve
nothing?

_DAP:_ I would like a clearer explanation of why Dr. Henke feels that
chlorites and devitrified glasses can produce too young K/Ar dates,
and if this is so, why they were dated in the first place.

_KRH:_ Again, as I just discussed above, the gain or loss of argon
has to do with changes in the chemistry and amorphous structure of
glass as it devitrifies and as chlorite develops from biotite or
other minerals. Often scientists date materials to determine how
they retain or release argon. Not all radiometric dates are taken
literally, that is, not all radiometric dates are used to determine
the chronological history of their host rocks. Sometime the dates
have other geochemical applications. For example, Dalrymple and
Moore (1968) dated the rims and centers of submarine pillow basalts
to understand the retention of Ar as a function of the lava's
cooling rate. They didn't intend on deriving actual radiometric
dates for the basalts. In another study, Hart (1964) obtained K/Ar
and Rb/Sr dates on minerals surrounding the Eldora stock in
Colorado. The purpose of the study was to understand how the
injection of the pluton affected the retention of daughter products
in the minerals of the surrounding rock as a function of distance
from the pluton.

_DAP:_ On reading Dr. Henke's reply, one sees that even he
acknowledges a large number of problems with radiometric dating.

_KRH:_ Yes, scientists admit that there can be problems, but they
are not as hopelessly numerous or complex as creationists claim.
Some rocks, especially sedimentary rocks, cannot even be dated with
radiometric methods. Fortunately, radiometric methods often work so
that geologists have put together a reasonable history for the
Earth.

_DAP:_ I would like to ask him what method is always reliable. I would
like him to provide a list of methods that are always reliable, and
together give conventional dates for the majority of the geologic
column.

_KRH:_ There is no such thing as "always" in science. No scientific
method works for all samples and under all conditions. Science just
doesn't work that way. Again, Harland et al. (1990) lists numerous
dates that have been used to calibrate the Phanerozoic geologic
time scale. I have already cited Hyndman (1985, p. 675-676), which
provides a list of largely reliable radiometric methods and which
minerals or other materials are most effective with those methods.
Faure (1986) and Dickin (1995) provide further details on which
materials in which rocks are useful for dating igneous
crystallization and metamorphic events.

_DAP:_ My impression is that even methods that are considered reliable
can be explained away if the dates do not fit.

_KRH:_ Again, no method is perfect in all situations. The real
issue is not to explain away anything. Science DEMANDS that you
explain EVERYTHING, whether the methods give you the results that
you expect or not. Even when things seem to work, explaining the
process helps scientists to understand what's going on, which in
turn allows us to expand on the methods and possibly find new
applications.

_DAP:_ The problem is complicated by the fact that if the date is too
young, one can invoke a later event, and if the date is too old, one
can say it was inherited from before.

_KRH:_ You can't rationally invoke anything unless you have field
or laboratory evidence to back it up. People can cry "god did it"
or "the argon just leaked out," but peer-reviewed journals would
demand at least some reasonable ideas and field/laboratory evidence
to explain an unexpected event. If a date is too old when compared
with other dates, magnetic or fossil data, the scientist must
explain why. If the date is too young, again the scientist must
explain why and provide the field/laboratory evidence to back it
up. For example, the mineralogy of the rock, minerals textures, or
field structures may indicate the presence of one or more
metamorphic events. If scientists don't explain anomalous results,
the peer-reviewers might suspect that the geologist messed up the
sample collection or the laboratory messed up the analysis.
Furthermore, even when the dates seem reasonable, peer-reviewers
would still want some references or evidence to back up the
results. All results should be justified and verified.

_DAP:_ But this does call these dating methods into question, since
many dates could have been inherited form earlier events before the
appearance of life.

_KRH:_ Certainly, igneous rocks may have experienced a number of
metamorphic, weathering or other alteration events after
crystallization. Some radiometric methods, such as K/Ar, may date
the last metamorphic event. Other methods, such as Rb/Sr whole rock
analyses, may date the initial crystallization event. Discordant
U/Pb dating may provide ages for both dates. I don't know what the
appearance of life has to do with radiometric dates.

_DAP:_ Dr. Henke discusses a few cases of double blind studies or
comparisons of different methods that show agreements. But what is
needed is a general study, not just isolated cases.

_KRH:_ What do you mean by a "general study"? I really don't know
what you're asking for that hasn't already been done. You just need
to review the literature before calling for a "general study"and
stating that the literature only has "isolated cases." The
literature is full of formations and mineral samples that have been
dated countless times. The results are consistent, abundant and not
"isolated." Again, Harland et al. (1990) and Odin (1982) list
numerous examples of radiometric dates that are used to support the
geologic time scale from Cambrian to Recent. Numerous meteorites
and world famous formations have been dated many times with many
different methods. Dalrymple (1991, p. 140), for example, lists 56
Rb/Sr, Pb/Pb, and U/Pb analyses for the Qorqut Granite of Greenland
from Moorbath et al. (1981), Pankhurst et al. (1973), and
Baadsgaard (1976). The results ranged from 2.52 to 2.58 billion
years. These results are very consistent and undermine creationism.
The 55 million year old Skaergaard Intrusive of Greenland has been
consistently dated by 40Ar/39Ar dating (Hirschmann et al., 1997);
fission track methods (Brooks and Gleadow, 1977); fossils and
magnetic data in associated rocks (Soper et al., 1976; Faller,
1975; Tarling, 1967; Tarling et al., 1988; Schwarz et al., 1979);
and other radiometric methods (Hirschmann et al., 1997, p.
647-648). Again, interlaboratory studies of minerals from
Phanerozoic outcrops fill the literature. I found several of them
just looking through a few volumes of the 1998 literature and
they're listed above.

_DAP:_ I do not comment on whether haloes give evidence for altered
decay rates or not.

_DAP:_ It is true that mixings of two sources in isochrons can be
detected. But mixings of three sources cannot. This is discussed in
great detail in the article "[19]More Bad News for Radiometric
Dating", along with other aspects of isochron methods.

_KRH:_ I don't know how you can claim that mixing of three sources
cannot be detected. As an example, Dickin (1995, p. 180-182) shows
that 87Sr/86Sr vs 1/Sr graphs have been used by Moorbath and
Thompson (1980) to decipher the complex mixing history of the
Tertiary Isle of Skye volcanics in northwest Scotland. Dickin
(1995, p. 180-199) mentions a number of other isotopic techniques
that are used to detect mixing between multiple sources. In
particular, Dickin (1995, p. 192-194) discusses Carlson and Hart
(1988) in some detail, where various Nd, Pb, and Sr isotope plots
indicate THREE distinctive mantle sources for basalts from the
northwestern United States. Simonetti et al. (1998) used Sr, Nd and
Pb isotopes to demonstrate that THREE distinct mantle components
mixed to form Deccan alkaline complexes in India.

_KRH:_ Your hypothetical example in "[20]More Bad News for
Radiometric Dating" is often hard to follow, but it is clearly
invalid. You attempt to show how three magmas with different
concentrations of a radioactive parent isotope (P), the daughter
isotope (D) of the parent, and a non-radioactive isotope (N) of the
daughter would go undetected by isochron methods. You state that
for the first source (#1), N1 = 0. For the second source, the
parent is absent, so P2 = 0. You state that the third source has no
D, N, or P, so D3 = 0, P3 = 0, and N3 = 0. To make things more
realistic, let's use Rb/Sr dating, so P = 87Rb, D = 87Sr and N =
86Sr. When we apply your analogy to a real world system, we can
immediately see that your assumptions are invalid. Terrestrial
magmas and rocks, water, meteorites and moon rocks have initial
87Sr/86Sr (D/N) values near 0.7. However, your first source ignores
nature and has D1 > N1 and N1 = 0 or an undefined 87Sr/86Sr. This
is unrealistic. You can't set the Sr and 87Rb values for your
hypothetical three magmas to any values you want. Nature restrains
your selection of values and voids your hypothetical argument.
Because nature restrains and controls the chemistry of Rb and Sr,
Rb/Sr dating works.

_DAP:_ Dr. Henke does not respond to my criticism of the isochron
based on meteorites from which the 4.5 billion year age of the earth
is obtained.

_KRH:_ I did respond. I simply cited Dalrymple (1991). I did not
extensively summarize or comment on Dalrymple (1991, chapter 6)
because I thought that you could read it for yourself and that the
reference would answer your questions better than I could.

_DAP:_ This involves only a small number of meteorites. What happens
when more meteorites are added?

_KRH:_ 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).

_DAP:_ But in any case, my main concern is with the age of life, not
the age of meteorites.

I encourage readers to consult the articles "[21]More Bad News for
Radiometric Dating" and "[22]Magma Opus Tells a Tale on Radiometric
Dating" for additional information. I also encourage them to re-read
my article "[23]The Radiometric Dating Game", where a number of Dr.
Henke's points are well discussed.

_DAP:_ In general, I believe that practicing geologists are well aware
of the weaknesses and assumptions of radiometric dating.

_KRH:_ Yes, we admit our weaknesses and limitations. Despite the
problems, radiometric dating usually works as the literature
indicates. At the same time, I wish that creationists would admit
the weaknesses, limitations and questionable assumptions associated
with taking Genesis literally.

_DAP:_ I close by re-citing a quotation from an evolutionary source,
cited in a creationist web site ([24] Science and the Bible - Part 2,
The Scientific Evidences for Creation):

"It is obvious that radiometric techniques may not be the absolute
dating methods that they claimed to be. Age estimates on a given
geological stratum by different radiometric methods are often quite
different (sometimes by hundreds of millions of years). There is no
absolutely reliable long-term radiological "clock". The uncertainties
inherent in radiometric dating are disturbing to geologists and
evolutionists... .[47]"

_KRH:_ You should really look up the original reference instead of
just quoting it from another creationist web site. As the web site
indicates, this invalid quotation is from Stansfield, William D.,
1977, "The Science of Evolution," MacMillian, p. 84. Stansfield is
a biologist and not a geochronologist. So, why should I accept a 20
year old opinion on radiometric dating from a biologist? Would you
want your dentist to give you advice on your eye sight? Besides,
did you ever wonder why your creationist allies left off the last
part of this quotation? Notice the three periods at the end of the
quote. Here is the full quotation with the missing part in capital
letters.

"It is obvious that radiometric techniques may not be the absolute
dating methods that they claimed to be. Age estimates on a given
geological stratum by different radiometric methods are often quite
different (sometimes by hundreds of millions of years). There is no
absolutely reliable long-term radiological "clock". The
uncertainties inherent in radiometric dating are disturbing to
geologists and evolutionists, BUT THEIR OVERALL INTERPRETATION
SUPPORTS THE CONCEPT OF A LONG HISTORY OF GEOLOGICAL EVOLUTION."

_KRH:_ This 20 year old quotation from a biologist is hardly a
death sentence for radiometric dating.

_KRH:_ Again, David, thanks for your time. Please read the
references that I cite. They would answer most, if not all, of your
concerns and questions. If not, my colleagues and I can give you
dozens and dozens of other references. There's no need to be so
distrustful of radiometric dating.

_REFERENCES_

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References

1. file://localhost/www/sat/files/tim_thompson/plaisted-review.html
2. http://www.chem.uky.edu/
3. http://www.uky.edu/
4. http://www.cs.unc.edu/~plaisted/
5. http://www.stanford.edu/
6. http://www.cs.unc.edu/
7. http://www.unc.edu/
8. http://www.firinn.org/trueorigin/dating.htm
9. file://localhost/www/sat/files/tim_thompson/plaisted-review.html
10. http://www.firinn.org/trueorigin/dating.htm
11. http://www.creationresearch.org/crsq.html
12. http://www.creationresearch.org/crsq.html
13. http://www.creationresearch.org/crsq.html
14. http://www.creationresearch.org/crsq.html
15. http://www.icr.org/pubs/imp/imp-179.htm
16. http://www.sciencemag.org/
17. http://www.icr.org/research/sa/sa-r01.htm
18. http://www.icr.org/research/sa/sa-r01e.jpg
19. http://www.cs.unc.edu/~plaisted/ce/dating2.html
20. http://www.cs.unc.edu/~plaisted/ce/dating2.html
21. http://www.cs.unc.edu/~plaisted/ce/dating2.html
22. http://www.cs.unc.edu/~plaisted/ce/magma.html
23. http://www.cs.unc.edu/~plaisted/ce/dating.html
24. http://hubcap.clemson.edu/spurgeon/books/apology/Chapter7.html
25. http://www.icr.org/pubs/imp/imp-179.htm
26. http://www.icr.org/
27. file://localhost/www/sat/files/tim_thompson/radiometric.html