There are varying opinions about the origin of carbon 14 and how it becomes a
part of organic matter. One opinion
teaches that carbon 14 is formed in the atmosphere when cosmic rays strike
nitrogen atoms in the air.
According to this theory it stays in the atmosphere for twenty-five years before
being absorbed through photosynthesis or rainwater.
Another view holds that carbon 14 is a naturally occurring isotope of
carbon 12. It turns into nitrogen
14, does not decay, and is very stable.
This view holds that this change occurs at a constant rate that is not
affected by the environment. A
problem with both of these environmentally based views was discovered when dirt
from the moon was found to contain carbon 14.
However, the moon has no atmosphere, and therefore, its carbon 14 could
not come from cosmic rays striking nitrogen.
Since carbon 14 has a half-life of less than 6,000 years, then the carbon
14 on the moon must be fairly young.
Since other dating methods prove the moon to be very old, it is then
claimed that carbon 14 comes directly from the sun.
Some have even collected carbon 14 from space suggesting that this is
evidence that carbon 14 comes from the sun.
It is theorized that the sun creates carbon 14 in its nucleus and sends the
carbon 14 out in solar flares.
Some contend that it is carried by the solar winds rather than in solar
flares. Many believe that the
sun sends out carbon 14; however, we need to understand that the sun is a
fairly unstable star that goes through cycles that dramatically affect the
climate of the earth. This most likely affects the amount of carbon 14
distributed by the sun.
Regardless of how carbon 14 is generated, scientist are fairly certain that
carbon is absorbed into plants through photosynthesis and is stored in the
wood and plant matter. Animals
eat the plants and deposit carbon into their wastes. The amount of carbon 14
in their wastes can be used to date the animals.
Wood is known to store carbon 14 as it can be found and measured in
the various rings of trees.
Other organic materials store carbon 14 such as bone; however, it should be
noted that since bone is porous,
Therefore, it easily absorbs carbon 14 from the environment around
Carbon 14 has a half-life of 5,730
years and was thought to stay in the atmosphere for twenty-five years before
being absorbed through photosynthesis or rainwater.
Certain man made interferences to carbon 14 levels in our environment
have revealed that the absorptions rate for carbon 14 at the surface level
of our environment could be as rapid as 4-6 years.
For the deep ocean these rates are thought to be significantly
higher. The amount of carbon 14
in the atmosphere that is available for absorption by living organisms is
fundamental to radiocarbon dating. The revelation of these rapid absorption
rates has the tendency of making radiocarbon dating more complicated and
Since carbon 14 is
unstable, the amount of carbon 14 in organic matter begins to decrease at a
given rate once the organic matter dies.
This dissipation rate is thought to be vary accurate and measurable,
hence the amount of carbon 14 in a given sample at the time of its
measurement is thought to reveal it relative age.
Knowing the amount of carbon 14 available for absorption by a living
organism is essential for the accurate determination of the age of the
sample being tested.
A sample of organic
matter is tested by burning it into carbon.
The carbon is then converted into graphite, and the levels of carbon
14 in the graphite are then measured.
Very sensitive and carefully calibrated instruments are used to
measure the levels of carbon 14 in the graphite.
It must be noted that “only about one part in a million million of
modern carbon is 14C.”
Therefore, the smallest portion of contamination in any given sample
can alter the results of the test.
It is important to
note that there are scientific limits for any radiocarbon dating.
Henry Morris notes that a half-life for carbon 14 is approximately
5,730 years, and he adds, “Therefore, by about six half-lives, or about
35,000 years, there would be practically no carbon 14 left to measure (some
claim to be able to measure an extremely small amount out to as much as
80,000 years, or 14 half-lives, but that is very doubtful).”
M. J. Aitken sets the half-life of carbon 14 at 5,730 years and
indicates that radiocarbon dating is limited to about 50,000 years at a
maximum on account of contamination.
He hopes that if contamination can be eliminated in the future,
dating can be extended to a 70,000-year maximum range.
The critical element
in radiocarbon dating is the level of carbon 14 contained in the sample at
the moment of its demise; this would be its zero carbon 14 age.
Taylor writes, “One of the most fundamental assumptions of the
14C method is the requirement that natural 14C
concentrations in materials of ‘zero 14C age’ in a particular
reservoir are equivalent to that which has been characteristic of living
organisms in that same reservoir over the entire 14C time scale.”
Therefore, the veracity of radiocarbon dating is dependent upon the
levels of carbon 14 that are and have been contained in the atmosphere.
If the earth is very old then carbon 14 levels would be at a constant
level having reached saturation.
However, if the earth is young then carbon 14 levels may not be at
saturation yet and would still be building to a constant level.
If this is the case, then the starting point for dating a sample may
not be as straightforward as some have assumed.
In addressing the issues of carbon 14
levels in our atmosphere, there are varying opinions in the scientific
field. Sheridan Bowman suggested, “in principle there is a constant 14C
level in all living organisms.”
His assumption is based on the presupposition that there is a constant level
of carbon 14 in our atmosphere and environment at all times.
If there is a constant level of carbon 14 in our environment and has
been for millions, even billions of years then dating with carbon 14 becomes
rather easy. In the early years
of radiocarbon dating this assumption permeated the radiocarbon scientific
Through dendrochronology, which is the
study of tree rings, some have suggested that it is possible to build a
tree-ring ladder that dates back as far as about 9000 B.C.
They suggest that it is then possible to determine the amount of
carbon 14 that was in the atmosphere each year by measuring the carbon 14 in
each ring. They note that the
amount of carbon 14 in the atmosphere has fluctuated over the years.
Henry Morris suggests that the evidence obtained from these tree-ring
carbon 14 studies indicates that the levels of carbon 14 in the atmosphere
have been and continue to be on a climb to saturation.
He suggests that this indicates that the earth may be younger than
50,000 years old since it would take approximately 50,000 years for the
carbon 14 levels on the earth to reach a saturation level.
He also notes that this fact affects the actual dating process since
the assumption has been that carbon 14 is already at a stable level; yet,
the evidence indicates that the level has been consistently climbing
The saturation theory suggested by
Morris appears to be substantiated by a chart placed in Aitken’s text.
The chart demonstrates the findings of data derived from
dendrochronologically dated wood and indicates that carbon 14 levels have
been constantly changing throughout history.
writes specifically of this saturation effect and includes charts that
demonstrate that it would take at least 35,000 years for carbon 14 levels to
reach saturation. However, he
makes the assumption that our current levels of carbon 14 must have reached
saturation a couple of hundred thousand years ago.
He also notes that the “zero” age for any sample is fully dependant
upon the stability of carbon 14 in the atmosphere and the various global
Therefore, the lack of a stable
saturation of carbon 14 in our environment presents a formidable problem for
radiocarbon dating. Whether one
holds the young earth presupposition and believes that our carbon 14 is not
constant because the earth has not existed long enough to reach saturation.
Or, if one is of the ancient earth point of view and believes that
the earth must have reached saturation long ago.
The fact that tree ring carbon 14 studies reveal an unstable and
changing level of carbon 14 in our environment makes radiocarbon dating a
random guess at its very best.
defines numerous major anomalies that affect the amount of carbon 14 in our
atmosphere at any given time.
He notes the reservoir effect and claims that there are various reservoirs
in our environment that absorb and release carbon 14 as carbon 14 levels
vary. The oceans are one such
large carbon 14 reservoir. The
assumption in the early years of radiocarbon dating was that these
reservoirs stabilized the amount of carbon 14 in our world.
However, Taylor notes, “one of the earliest illustrations of the
breakdown of this assumption was the determination that living samples from
a fresh water lake with a limestone bed exhibited apparent 14C
‘ages’ of as much as 1600 years.”
also noted the de Vries effect which identifies that in at least the last
1600 years there have been significant changes in the levels of
carbon 14 contained in our
atmosphere. This effect
“created a situation in which it is not possible to assign an actual
calendar age to any sample derived from this time period to better than
about a 300-year time span unless ‘wiggle-matching’ procedures are
In other words, adjustments have to be made to the results of the
tests in order to arrive at an accurate date.
For samples of a known age this wiggle-matching is possible.
However, how does one know whether one’s wiggle-matching has returned
a successful age on a sample of unknown antiquity.
A third anomaly has been identified as the Suess effect.
The Suess effect is caused by the significant use of fossil fuels in
the twentieth century. Fossil
fuels release large volumes of CO2 into our atmosphere that
contains no carbon 14.
Hence, these fossil fuels have lowered the amount of
carbon 14 in our atmosphere.
This effect was first noted in 1950 by Hans Suess of the United
States Geological Survey. While
this effect is noted by Taylor, an appropriate
compensation is not prescribed.
The last anomaly noted by Taylor is that of the Atomic Bomb Effect.
The test of atomic bombs in our atmosphere has produced significant
amounts of artificial carbon 14.
notes, “between 1955 and 1963, the
activity in terrestrial organics almost doubled.
Unfortunately, it was during this period that early work on the
method, using solid or particulate carbon, occurred.”
The effect of atomic weapons made it complicated to do accurate
low-level carbon 14 testing.
Since the1963 international agreement halted the testing of atomic weapons
in the atmosphere, it would be assumed that the carbon 14 levels would have
returned to normal. However,
the continuing growth in the use of fossil fuels has probably over
compensated for the Atomic Bomb Effect.
When radiocarbon dates are suggested it
should be understood that these dates are not the same as actual calendar
dates because a radiocarbon date represents a range of dates falling along a
bell-shaped curve. Each
fragment taken from a sample will very in date by a couple of hundred years
and will follow along the bell of a curve.
Therefore, the center point of the curve is presumed to be close to
the accurate date of the wood or organic matter.
One should keep in mind that carbon 14 tests are expensive to do and
often only a few samples are taken at a given site.
Therefore, carbon 14 dates are, at best, only a ballpark figure.
Removing contaminating materials from a sample can be a
daunting task for radiocarbon dating. When dating things like charcoal, it
is important to remove things like roots; however, root hairs are
microscopic. Hairs from roots
that had already died may be impossible to find and can add more recent
carbon to the sample. Once the contamination is removed, the sample is
burned to carbon; the carbon is converted to graphite; and, the graphite is
dated. This conversion process
may also introduce contamination to the sample.
It has been noted by many researchers that the simple selection of a
laboratory can affect the date returned for a given sample.
Since the amount of carbon 14 in the atmosphere changes,
the testing has to be carefully calibrated to remain accurate.
This calibration can often be daunting.
It is thought that items from 8000 B.C. actually carbon 14 date at
about 9000 B.C.. This date-gap
widens with older items. This
is compounded by the calibration curve used, as different curves are
available. Taylor discusses the complicated process of
calibration by providing a series of more than fifteen charts and over
twenty pages of explanation that reveal that the calibration curve used on a
particular sample could easily vary the resulting date by as much as 1,000
years, if not more.
Other difficulties can affect the results of radiocarbon
dating. When a pool of water
sits on limestone for a long time, old carbon dissolves into the water.
This is illustrated by living plant life taken from Montezuma's well
which carbon 14 dates at about 25,000 B.C.
If a site was underwater for a long time before it was uncovered, it
may carbon 14 date to be much older than it really is.
Also, bone is a very porous material and will absorb
carbon 14 from materials around
the bone including the soil in which it is buried.
These are just two examples of the many circumstances that surround
Items that are thought to be reasonably datable include
wood, bone, shell, sediments and soil, peat, mortar, seeds, grain, ivory,
paper, and textiles. However,
there is considerable debate about the veracity of radiocarbon dating for
many of these items.
Radiocarbon dating was successful in dating one of the Dead Sea scrolls to
what would be considered a relatively accurate date range, but the target
range was known and expected and may have contributed to the calibration
procedures selected for the test.
While some strongly support radiocarbon dating, it must
be noted that since our environment is not at the
carbon 14 saturation level, as
some have assumed, it is very difficult, if not impossible, to know the
level of carbon 14 a sample held
when it died. Therefore, it is
virtually impossible to date organic matter with this dating method.
The levels of contamination that may find their way into a sample are
numerous and unpredictable. It
is of particular interest that the limit of radiocarbon dating is between 30
and 40 thousand years; it may be possible to achieve 70 thousand years, but
it is highly unlikely. Anyone
that presents an older radiocarbon date is outside of the scope of Carbon 14
dating and is either ignorant or deceptive with his assumptions.
Therefore, radiocarbon dating is the science of measuring
the levels of carbon 14 in
ancient organic matter with the intention of dating its approximate age.
The method is complicated to perform and requires that numerous
calculations be performed on the results in order to achieve a presumed
level of accuracy. The changing
levels of carbon 14 in our
atmosphere challenge the method, as the amount of
carbon 14 absorbed by the
organic matter at its death is its ‘zero
carbon 14 age.’
Radiocarbon dating is limited to approximately 40,000 years at the
outside as any sample of older antiquity would have too little
carbon 14 to measure.
After the inception
of radiocarbon dating and as its dating method was being employed with an
assumed and blind accuracy, dendrochronology appeared in the scientific
dating community and challenged the assumed accuracy of carbon 14 dating.
Dendrochronology compares the tree rings of trees.
As successively older trees are added to the chronology, a tree-ring
dating scale has developed.
Dendrochronology has challenged radiocarbon dating in that it has revealed
that the amount of carbon 14 in our environment is not at saturation and is
still changing. The tree rings
also reveal that the dates assumed to be represented by various carbon 14
results have not always been accurate.
While tree ring
dating appears to be relatively simple and straightforward, there are
problems that arise in tree ring studies.
Stephen Nash writes, “Tree-ring dating is a straightforward
procedure, at least in principle.
In practice, it can be astonishingly difficult.”
Some tree species may show vary little variation in their tree ring
growth while others may be aggressive in their response to their
environmental conditions. Some
species may not grow at all in a given year, yielding a missing ring, while
others may provide false rings during some years.
Against the problems of missing and false rings, there are two good
defenses. First, examining the
whole circumference of the ring may yield a partial ring at some point in
the ring. This becomes
increasingly difficult in situations that require that an increment corer be
used, such as when dating the wood out of an ancient cathedral or other
structure. In such
circumstances only a portion of the circumference of a tree may be available
for examination. Secondly,
comparison between contemporary old and young trees may provide a valuable
defense, as the younger trees are less susceptible to missing or false
There are four
conditions that must be fulfilled before dendrochronology can be considered
for a given region. First, the
tree species being examined can only add one tree ring per year.
The dendrochronologist must be able to identify missing and double
rings that are sometimes present in stressful years.
Second, the growth of the tree species must only be limited by one
environmental factor at a time.
In some regions tree growth is limited by a lack of moisture.
In Alaska tree growth is limited by the cold
climate. A combination of these
factors would make tree-ring dating virtually impossible.
Third, the tree species must show a variation in its growth pattern
from year to year. Nash notes,
“Trees that enjoy beneficial growth factors tend to produce annual rings
that are relatively uniform in their width and, in a sense, have no
Trees that grow under an environmental factor that stresses their
growth develop variations in their ring growth that lend themselves to
dating. Lastly, the
geographical region within which the trees are being studied has to be
extensive enough that the tree-ring data can be crossdated with trees
somewhat removed from each other by distance.
There appears to be
some influence upon a tree’s ring growth based upon its actual growing
conditions. Aitken notes,
“Although it is evident that trees carry a climatic signal the relative
importance of different factors is not easy to assess and interpretation in
terms of past climate is far from straightforward.
Also, such interpretation – as well as dating – is subject to
interference by local environment, e.g. whether the tree was in a dense
forest or isolated.”
Hence trees growing in an open field will demonstrate different
growth patterns than trees growing in a forest.
When trying to date ancient timber found in a tell or other
archaeological site identifying these trees can be troublesome.
The best that
dendrochronology can provide is the date that the tree was felled.
In order for this date to be provided the sapwood as well as the
heartwood must be intact. The
sapwood is rarely left attached during woodworking.
However, if it was left intact the likelihood of it preservation is
small, especially in wet burial conditions.
Aitken notes that if the sapwood is not present “then an estimate of
the number of rings of missing sapwood has to be made.”
In order to check
the correctness of a dendrochronological ladder, Baillie notes three levels
of replication. Primary
replication provides matches between individual tree-ring patterns that go
to make up a site chronology.
Secondary replication provides a more robust and internal replication as it
allows for comparisons between
independent site chronologies.
Tertiary replication “provides the ultimate test, involves correlations
between the chronologies of independent workers.”
The tree ring ladder
currently extends back to 6700 B.C. for the Bristlecone Pine chronology of
the White Mountains of California.
A European chronology known as the Irish bog-oak ladder extends back
Both of these chronologies have floating chronologies that are
thought to be able to add to both ladders significantly if a linking tree
can be found. Concerning the suggested ladder of tree-ring data for these
chronologies, Baillie suggests that there are gaps in the chronology where
the ladder is connected by one or two trees, which makes the chronologies
open to significant error.
There are also places where chronologies from different regions have been
linked together, which causes significant criticism.
As a result, the extension of the chronology is open to speculation.
dendrochronology is the science of tree-ring dating that works to build a
dating ladder based on the study of tree-rings.
This science has been used to date ancient architecture and
archaeological sites. It has
also been used to correct the calibration scales for radiocarbon dating as
tree-rings store carbon 14 for calibration purposes.
Dendrochronology currently extends back to approximately 6700 B.C.
Thermo Luminescence Dating
Thermo Luminescence dating (which will be referred to as
TL in this paper) is used to determine how long ago a piece of pottery or
other crystallized element was placed in a kiln.
TL measures the electrons trapped in the crystals in the pottery.
This measurement can point to how long ago the pottery was baked in a
kiln. This dating method could
be used in conjunction with most archaeological sites since pottery and
pottery shards are normally present at these sites.
Luminescence dating is based on the principle that when
pottery is baked in a kiln, it released its accumulated radiation.
Fleming notes, “Each of the minerals used to make a piece of pottery
had geological radiation histories even before they were brought together in
ceramic manufacture, but kiln-firing at 600°C
or more will have completely erased the associated TL signal.”
A scientific explanation is given when Nash writes, “The natural
radioactivity present in these materials and their surroundings cause
ionization of atoms, which leads to subsequent trapping of charged particles
at defects in the crystal lattice.
Exposure to sufficient heat or light releases the charge from these
traps and results in a luminance signal whose intensity is proportional to
the time elapsed since the previous detrapping event.”
Aitken notes, “The act of firing ‘drained’ all previous TL, thereby
setting the clock to zero.”
Once the collected luminance is released from the crystals contained
in the pottery, it begins to build its luminescence at a constant rate that
is measurable when the pottery is exposed to sufficient heat again.
Thermo luminescence dating is significantly harder to
perform than radiocarbon dating.
In radiocarbon dating the carbon14 decays at a regular rate in spite
of the element that contains it.
With Thermo Luminescence dating, each material holds a different
sensitivity and “each sample must be measured individually because it will
be influenced by the actual impurity content and thermo history.”
Nash notes, “Luminescence requires the measurement of a multitude of
variables, each with its own error term, which when propagated lower
In essence there are more tests that need to be performed and more
calculations that need to be completed.
On the other hand radiocarbon dating does not produce a calendar date
with its result; Thermo Luminescence dating does.
It should be noted, as well, that while radiocarbon
dating only extends back 30 to 40 thousand years, and Dendrochronology
reaches back approximately 8,000 years, Thermo Luminescence dating can reach
back nearly 500,000 years.
Giving it the longest reach of those dating methods studied in this paper.
For those holding an old earth philosophy this would be a strong
When a piece of pottery is tested for Thermo
Luminescence, it is first ground to a fine powder and is then placed in an
oven that is fitted with a photomultiplier.
When the sample is heated it will give off three types of light.
The first is incandescence, which is the red-hot glow that emanates
from the sample. This light
will overload the photomultiplier and must be filtered out using a special
filter. The second light is
spurious thermo luminescence and is the result of the impurities in the
sample as well as the process of preparing the sample.
This spurious emission is controlled through the use of an inert gas
like nitrogen, argon, or helium.
This also requires the evacuation of oxygen from the oven before
injecting the gas.
Another important requirement of laboratory preparation
is that all processing must be completed under red light.
Aitken notes, “exposure to light causes most minerals to lose some of
their latent TL (i.e. to be ‘bleached’); sunlight, daylight and fluorescent
white lights are particularly effective.”
This genders a question.
What if the owner set the pottery out in the sun for days, months, and years
after it was baked,? Would this
effect the Thermo Luminescence dating?
If momentary exposure in the laboratory will impact the sample, one
has to wonder about the samples treatment throughout its history, including
its discovery at the archaeological site.
One safe guard that is imposed in the testing process is that a
second sample is tested that is carrying an artificial dose of TL that is
applied for the purpose of verifying the testing procedure that is employed.
Aitken notes that the position of the sample in the
ground is a large part of the accuracy of Luminescence dating.
In his text Aiken provides a figure that shows how a sample buried
less than 30 cm under the surface would be contaminated by the gama
radiation that could penetrate the soil to that level.
He also notes that debris buried near the sample could contaminate
the sample as well. In his
figure Aitken notes even a rock, if it does not have the same level of
radioactivity as the sample, could significantly affect the same.
In considering Thermo Luminescence dating for
archaeological purposes one must consider the error margins of the method.
Fleming demonstrates in his text that the error margins for this
dating method may make it impractical for most archaeological sites that are
within the dating range of radiocarbon dating.
He notes, “little effort has been (or indeed should be) expended on
pottery from Mediterranean cultures active in the first millennium BC or on
Roman wares of the first four centuries AD, unearthed in northern Europe.
Stylistic dating for those parts would rarely carry more than twenty
years uncertainty, but a TL result would be unlikely to carry a standard
of less than
years per analysis.”
Therefore, the error margins of samples that can be more accurately
dated with other methods are to be preferred over Thermo Luminescence
It is interesting that Aitken writes, “pottery was not
made much before 10,000 years ago and it is earlier, in the Palaeolithic,
beyond the 40,000—year range of radiocarbon that TL makes it most important
contribution to archaeology.”
Here Aitken turns his discussion toward dating materials like flint,
burnt stones, volcanic lava, and other elements.
The difficulty with each of these other elements revolves around how
well the TL clock was set to zero.
Was the element heated enough to release the TL content within the
sample? That is a question that
may never be answered.
Possibly the most noted problem discussed in the study of Thermo
Luminescence dating is the question of contaminating the sample with outside
influences. It is difficult to
understand how a sample buried less than 30 cm in the ground could be
contaminated while the same sample was originally created to be used in
daily life. Certainly, the
piece of pottery was not created and then immediately buried.
It most likely had significant exposure to sunlight, most likely
direct sunlight. How would
long-term exposure to direct sun light effect the luminescence dating of the
object? Having searched for an
answer none was found in the texts available to this author.
Therefore, Thermo Luminescence dating attempts to date an
artifact based on its thermo luminescence radioactive content.
It is based on the principle that pottery and certain other elements
release their luminescence content when they are exposed to enough heat,
like the heat of a kiln oven.
This heat essentially sets the luminescence clock to zero for the sample in
question. Over time, the sample
will recollect and store luminescence radioactivity that when reheated can
be measured to establish through a difficult process believed to be an
accurate calendar date for the artifact.
In this study we have considered the scientific dating
methods of radiocarbon dating, dendrochronology, and thermo luminescence
dating. We have considered the
origin, principles and difficulties surrounding each method.
We have also considered the reasonable date ranges that might be
provided by each method. In the
end we find that these scientific methods are less reliable and usable than
the general public might currently understand.
In subsequent modules of study it will be discovered that these
scientific methods are rarely trusted by archaeologists in the field today.
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