Transcript PowerPoint - Living Stones

RADIOMETRIC DATING
&
THE AGE OF THE EARTH
Why is this topic in any way important?
The Theory of Evolution requires very long
time spans for the proposed changes in
organisms to take place.
This is due to the number of generations needed to allow very small changes to
accumulate and produce species/species transitions, if this is possible.
Therefore, scientists who believe in evolution need to be able to
show that the Earth is very old in order to validate their ideas.
If the Earth is young, then evolution cannot happen.
It is not straightforward to estimate the age of the Earth [or the universe] as
huge assumptions have to be made to do so.
Radiometric dating has been used by geologists to estimate the age of rocks in
the Earth’s crust.
Radiometric dating is used to estimate the age of some rocks
There are THREE basic rock types:
IGNEOUS
[cooled from molten rock]
SEDIMENTARY
[mixed particles of igneous rock]
METAMORPHIC
[reheated sedimentary rock]
Only igneous and metamorphic rocks can be used for radiometric dating
as the radioactive materials are “frozen” in when the rock cools
BUT… the vast majority of fossils are found in sedimentary rock layers
About 75% of the Earth’s land surface is covered by sedimentary rock
Therefore, fossils cannot normally be dated using the rocks in which they are
buried – only adjacent strata where applicable
The Earth’s crust
How has the age of rocks been estimated in the past?
Traditional geology has used an idea popularised by Charles Lyell. 1797 –1875
Uniformitarianism
This is a geological doctrine. It states that current geologic
processes, occurring at the same rates observed today, in
the same manner, account for all of Earth's geological
features.
“The present is the key to the past”
Modern geologists are moving away from this model and many now think that
the sedimentary rock layers were the result of a series of catastrophic events.
The 1980 eruption of Mount St. Helens is a recent catastrophic event
NOAH’S FLOOD IS A BIBLICAL CATASTROPHIC EVENT!
So now the situation has changed and scientific - rather than purely dogmatic dating methods are sought to ascertain the age of rocks and fossils.
Lyell said his goal was to: "free the science from Moses“, when he wrote
his “Principles of Geology”
The Geologic Column
This is the conventional
representation of the so called
geologic column including some
typical fossil types found in the
layers.
If these layers were laid down
very gradually, according to
uniformitarian principles, then
this could provide evidence for
evolutionary development.
[Despite the very awkward issue
of the “Cambrian explosion”]
If these layers were laid
down by a single
catastrophic event, then
evolution is a dead theory
THE METAPHYSICAL ASSUMPTIONS
There is no God, only the material world exists.
God exists and he created the material world.
We are here and simpler life forms exist.
God created all life forms.
Therefore we must have evolved from simpler
life forms as the human race is very recent.
We have NOT evolved from simpler life forms
and the human race is a very recent creation.
The biochemical and physiological similarities
between higher organisms provide evidence of
descent.
The biochemical and physiological similarities
between higher organisms provide evidence of
a common design.
Evolution is therefore a FACT as there is no
other possible explanation for the data, apart
from alien intervention.
Therefore, all other proposed causes of life are
not correct.
According to the neo-Darwinian theory,
evolution requires millions of years. Therefore,
the fossil bearing rocks containing simple
organisms MUST be millions of years old.
Millions of years are NOT required for creation
so the fossil bearing rocks are not ancient and
were laid down by a recent flood as described
in the Bible.
Any data that indicates a young age for
fossil bearing rocks MUST BE WRONG
Any data that indicates a very old age for
fossil bearing rocks MUST BE WRONG
The age of the igneous and metamorphic rocks underneath the sedimentary layers does not
matter in terms of evolution! These may indicate the age of the Earth.
The underlying rocks do not contain fossils so can never provide evidence of any
proposed evolutionary timeline.
Sedimentary rocks are most often dated using “index fossils”. This is called relative
dating.
The sedimentary layers
containing the fossils cannot
easily be given an absolute
date. Therefore, nearby rock
intrusive layers are used i.e.
hardened lava and “tuff”,
which is compacted volcanic
ash. These layers are dated by
radiometric means, often
potassium/argon dating.
Normal perceptions regarding radiometric dating
FossilEra
“Absolute dating is used to determine a precise age of a rock or fossil through radiometric
dating methods. This uses radioactive minerals that occur in rocks and fossils almost like a
geological clock. It’s often much easier to date volcanic rocks than the fossils themselves
or the sedimentary rocks they are found in. So, often layers of volcanic rocks above and
below the layers containing fossils can be dated to provide a date range for the fossil
containing rocks.”
This quotation from a website that sells fossils indicates how
much trust is placed in the apparently “precise” dating that can
be achieved through radiometric techniques.
“For religious reasons, some students believe that the earth is young
(on the order of 10,000 years old); they are antievolution at least in
part because a young earth would provide inadequate time for
evolution to occur. Therefore, it becomes important for them to
invalidate radiometric dating as a way to disprove evolution.
Although one cannot deal with the religious ideas promoting such
views, students need to understand how isotopic age dating works
and that it is very accurate—usually less than 1% error of
measurement. Methods used for radiometric dating are based on the
same physics that put people on the moon—it is not unreliable
science! Commonly students are familiar only with carbon-14 dating,
and are unaware of the large number of isotopes available for dating
different periods of time. The multiplicity of isotopic dating
techniques resulting in the same or very close dates also supports the
reliability of radiometric dating.”
We are told here that the same physics that put
men on the moon can date rocks better than 1%
Here is how to get reliable rock ages…………
STEP 1
Process the rock with
sophisticated equipment.
A pure rock sample is
thus obtained.
STEP 2
Look at the rock under a microscope, after sophisticated processing.
STEP 3
Carefully examine the rock to discover its age.
STEP 4
Turn up the magnification to discover the age of the rock.
MAGMA PRODUCTS
DCLXVI
THE THREE KEY QUESTIONS
How does radiometric dating work and what can it tell us?
How accurate is radiometric dating?
Can we place confidence in radiometric dating?
The centre of an atom is called the nucleus and is positively charged.
This enables negative electrons to stay in “orbit” around the nucleus.
The nucleus contains particles
called protons and neutrons. In
most atoms there are roughly
equal numbers of each.
The protons have a POSITIVE CHARGE
The neutrons have NO CHARGE
The number of negative electrons is
equal to the number of protons.
The nucleus is in fact very small and is only 1/100,000 the size of the whole atom.
Atoms of the same element can have different numbers of neutrons in the nucleus.
These are called ISOTOPES.
Some isotopes of an element can be stable but others are not and the nucleus can
decay, often forming a completely new element. This is called RADIOACTIVE DECAY.
The decay is random, BUT has a definite probability of happening for any isotope.
The nuclei of atoms like to
be in their “comfort zone”
This is often shown on a
neutron/proton graph
If the neutron/proton
ratio goes outside the
stability region then the
nucleus will be unstable.
This is often called a
RADIOACTIVE ISOTOPE.
The unstable nuclei of atoms can “decay” emitting energy or particles or even splitting into
two smaller nuclei.
Scientists cannot predict when a particular nucleus will decay but when there
are billions of nuclei [in even a very small sample of material] the decay
process is statistically predictable.
Radioactive source decay equations
N0
N
activity   A 
 N
t
N  N 0e
N
T1 
2
0.693

 t
half life
λ = decay constant
N
 N
t
N
 t
N
ln N  t  c
ln N  t  ln N 0
N  N 0e
 t
N
 N    t
When t = 0 N = N0 so
N
ln
 t
N0
λ is the decay constant and N0 is the initial
value of N at t =0
radioactive decay graph
Nt
this is an
exponential decay
The number of active atoms tends
to zero after a long time
Time t
HALF LIFE
The average time taken for HALF the active atoms to decay in a sample of
any isotope is predictable and is called the half life.
It doesn’t matter where you start, the half life is always the same.
The longevity of any radioactive isotope depends on its half life.
Short half life decays quickly.
Longer half life decays more slowly.
How can radioactive decay be used to estimate dates in the past?
daughter atoms (d)
[ decay product ]
Nt
parent atoms (P)
[original radioactive material ]
The time that has elapsed
from an event in the past to
the present can be estimated
if the P/d RATIOS are known
for the date in the past and
for the present, and also the
half life is known.
TIME INTERVAL
Time t
PAST
PRESENT
Measuring current P/d ratios with a mass spectrometer is possible but the key problem is
how to estimate the isotope ratios in the past.
Pt  P0 e  t
do
dt
Po
Pt
P0  d 0  Pt  d t
d0
R0 
P0
dt
Rt 
Pt
t
d 0 Pt d t P0 e  t
dt
1
  
 t
P0 P0 P0
P0
Pt e
1  R0  e  t  Rt e  t
1  R0
 e  t
1  Rt
t
ln
 
1 Rt
1 R0

If R0 = 0 then t can be found as Rt
can be measured
Some isotopes used in long age radiometric dating
ZIRCON
PITCHBLENDE
Intrinsic problems with simple radiometric dating
1. The initial isotope ratio cannot be measured directly.
2. Some of the daughter product may have been in the rock already before
any decay of the parent took place.
3. The rock may not over time be a closed system and could gain or lose
parent or daughter atoms.
4. The radioactive decay rate may not have been constant.
N.B. Measuring current half-lives is not difficult and can be done with
reasonable accuracy in most cases.
POTASSIUM - ARGON DATING
Potassium is a highly reactive metal and argon is a noble gas.
This dating method overcomes the initial isotope ratio problem as it is assumed that
all the previous argon gas has escaped from the rock when molten.
About 0.01% of natural potassium is
radioactive potassium 40.
About 10% of K40 decays
to produce argon gas.
40
19
39
19
K 1940K 1941K
40
K  10e18
A   
If the potassium/argon ratio can be measured then the age of solidification can
be calculated if the rock is a closed system thereafter.
Initial argon in the rock, subsequent reheating, or later diffusion/infusion will all
invalidate this method.
The minerals that are best suited for dating include biotite, muscovite, and plutonic/high grade
metamorphic hornblende, and volcanic feldspar; whole rock samples from volcanic flows and shallow
instrusives can also be dated if they are unaltered (Faure, 1986).
K40 decay scheme
The potassium and argon
concentrations in the rock have
to be measured from different
pieces of the same sample.
The argon concentration is
measured using a mass
spectrometer while the
potassium concentration is
measured via absorption
spectrometry.
Argon – Argon dating
This is a variation on potassium-argon dating where the measurement of
the K/Ar ratio is from the same rock sample.
The rock sample is irradiated with fast neutrons in a nuclear reactor in
order to convert the potassium 39 to argon 39. The natural K40/K39 ratio is
known, so a ratio of argon39/argon40 measured in a mass spectrometer
can reveal the original K40/Ar40 ratio.
This technique has to be calibrated against a known reference which is
mostly dated with the original K/Ar method. Hence only relative dates can
be obtained.
Argon–argon (or 40Ar/39Ar) dating is a radiometric dating method invented to supersede
potassium-argon (K/Ar) dating in accuracy.
Dating minerals may provide age information on a rock, but assumptions must be made.
Minerals usually only record the last time they cooled down below the closure temperature,
and this may not represent all of the events which the rock has undergone, and may not match
the age of intrusion. Thus, discretion and interpretation of age dating is essential. 40Ar/39Ar
geochronology assumes that a rock retains all of its 40Ar after cooling past the closing
temperature and that this was properly sampled during analysis.
The 40Ar/39Ar method only measures relative dates. In order for an age to be calculated by
the 40Ar/39Ar technique, the J parameter must be determined by irradiating the unknown
sample along with a sample of known age for a standard. Because this (primary) standard
ultimately cannot be determined by 40Ar/39Ar, it must be first determined by another dating
method. The method most commonly used to date the primary standard is the conventional
K/Ar technique.[1] An alternative method of calibrating the used standard is astronomical
tuning (also known as orbital tuning), which arrives at a slightly different age.[2]
Why can potassium-argon dates be unreliable?
1. The original molten rock contained argon which heating had not removed.
2. The rock cooled slowly allowing argon to diffuse into the rock.
3. Over time, argon diffused out of the rock as it is inert and has a small
atomic radius.
4. Atmospheric argon entered the rock at some stage (argon is about 1%
by volume of the Earth’s atmosphere and this argon is 99.6% 40Ar).
If K – Ar dates are to be trusted to indicate “millions of years” then the rock
must have been a completely closed and stable system after cooling, and
also have contained no argon40 at all.
K – Ar dating is used to estimate the ages of lava and tuff layers which are
found in the sedimentary rock layers.
The KBS TUFF controversy
Leakey supplied samples from the KBS tuff to Jack Miller, a geophysicist at Cambridge
University, to determine the feasibility of radiometrically dating them. Jack Miller and
his partner Frank Fitch preliminarily dated the rocks at 212 to 230 million years old. In
conventional geochronology, those dates correspond to the Triassic (the lower dinosaur
strata), but Leakey was working near the boundary of the Tertiary and the Quaternary,
which is thought to be only around two million years old.
In 1980, Ian McDougall of Australian National University weighed in on the KBS tuff
controversy, reporting a date of 1.88 million years. Again, much more interestingly,
McDougall revealed that Fitch and Miller had achieved a scatter of 0.52 to 2.64
million years on one set of samples, but on another set, they had a scatter of 8.43
to 17.5 million years! Thus, the total scatter was from half a million years to 17.5
million years, a range of 17 million years (not including the preliminary finding of
230 million years) on a layer of rock supposedly around two million years old.
There is a HUGE difference between the intrinsic accuracy of
mass spectrometer measurements and the variability in the
rock itself due to a range of unpredictable and unknown
interfering factors.
Dalrymple's early work on 26 historic lava flows showed that many of them had excess
argon and were not set to zero at the eruption of the volcano. The following is the data
from these tests: 5
•
•
•
•
•
•
•
•
Hualalai basalt, Hawaii (AD 1800-1801)
Mt. Etna basalt, Sicily (122 BC)
Mt. Etna basalt, Sicily (AD 1972)
Mt. Lassen plagioclase, California (AD 1915)
Sunset Crater basalt, Arizona (AD 1064-1065)
Glass Mountain (BP 130-390)
Mt. Mihara (AD 1951)
Sakurajima (AD 1946)
1.05 to 1.19 million years
100,000 years
150,000 years
130,000 years
210,000 to 220,000 years
130,000 years in the future
70,000 years in the future
200,000 years in the future
It seems that rocks whose ages are very recent cannot be accurately dated
by K-Ar techniques just because of the relatively wide ranges of error.
“A few years ago I took a course in the ‘Evolution of Desert Environments’. We were
standing on the Simi Volcanic flow, about 80 miles south of the south end of Death Valley.
The instructor was a well known geologist and evolutionist from Cal. State Long Beach.
He told us that the upper end of the flow was dated at 100,000 years, the middle of the
flow was dated at 50,000 years, and the toe of the flow was dated at 20,000 years. He then
noted that the whole flow probably occurred and solidified (the surface at least) within
weeks. He then said, based on his observation of the rates of evolution of desert
environments, he thought the flow was less than 10,000 years of age. He then said,
‘radiometric dating is the cornerstone of modern historical geology and we get this kind
of variation?’ Clearly he was not happy with the published dates on the Simi flow”.
The Simi flow would have been dated by the K/Ar method
Physics cannot date rocks! It can only be used to measure isotope ratios in any
sample of rock. This ratio has to be interpreted in terms of the assumed
formation and history of the rock. The measured ratio may be very accurate
indeed but the calculated age of the rock depends upon the model(s) used.
Rubidium strontium dating
Rubidium and strontium are both reactive metals.
This uses a very simple decay process, which has very long half life. Therefore the
dating method is only suitable for rocks which are thought to be very old indeed.
87
37
87
Rb 38
Sr  10 
Half life = 48,800,000,000 years
The problem with using Rb/Sr dating is that the rocks in question already have
strontium present before cooling. Therefore the initial conditions are not known.
This means that a special technique has to be used which is called
ISOCHRON DATING.
ISOCHRON DATING
The initial conditions of rock can never be measured – only assumed.
Some radioisotopes in rocks produce a daughter product that has a
stable version [another isotope of the daughter element ] already in the
rock. If the two isotopes of the daughter element are evenly mixed when
the rock is formed and the parent element is unevenly distributed then
isotope ratio measurements can in fact yield an age estimate.
This means that the original amount of daughter product does not need to
be known, i.e. the original parent/daughter isotope ratio is not needed.
Several isotope ratio measurements need to be taken from different
parts of the same rock sample. In this way variable amounts of the
parent isotope will be present.
Isochron dating is theoretically wonderful but in practice there are problems.
P0
P
d
d0
Two isotope ratios need to be measured
to determine an isochron date. These are:
P
D
and
d  d0
D
A graph is plotted of
D
d  d0
D
against
P
D
time
The gradient of this line gives the age of
the rock via a simple formula.
d  d0
D
x x
x
x
gradient m
x
P
D
 m  1
t  ln 




  decay constant
ISOCHRON THEORY
P  P0 e  t
P0  Pe t
P0  P  d
number of atoms constant

Pe  P  d

t

P e 1  d
t
t
exponential decay

d  P e 1

t

d  d0  P e  1  d0
d  d 0   P et  1  d 0
D
D
measured isotope
ratios
D
constant at
a given time
constant at
all times
If a graph is plotted of
the isotope ratios, a
straight line is obtained
whose gradient enables
the time to be found.
Isochron dating promises mathematical perfection , but………….
Mixing of rocks can produce fictitious isochron plots
If these two rocks are mixed
together but not perfectly, and
various samples are taken and
analysed to produce an
isochron plot, then a straight
line graph is obtained whose
slope is meaningless.
P1
d1
D1
P2
d2
D2
ROCK 1
d
D
ROCK 2
x
ROCK 1
x
x
ROCK 2
mixing line
P1
P2
d1
d2
D1
D2
ROCK 1
f
1-f
ROCK 2
As the mixing fraction changes, the relative proportions of each isotope type change.
If the isotope ratios from a set of samples with different mixing fractions are plotted
as if they were a standard isochron plot, then a straight line is obtained which has no
age significance. This is called a FICTITIOUS ISOCHRON.
MIXING THEORY
The mixing of two equal masses of two rock types can be defined by a mixing fraction f where 0 < f < 1
Pm  fP1  1  f P2
Y
The isochron plots
then become:
Simplifying using
Finding the line
gradient

1 f
f
d m  fd1  1  f d 2
Dm  fD1  1  f D2
dm
fd  1  f d 2
P
fP  1  f P2
 1
X m  1
Dm fD1  1  f D2
Dm fD1  1  f D2
P
P  P2
d
d  d 2
X m  1
Y m  1
Dm D1  D2
Dm D1  D2
Y 
d1  d 2 d1  D1d 2  d1 D2 


D1  D2 D1
D12  D1 D2
X 
P1  P2
P  D1 P2  P1 D2 
 1 
D1  D2 D1
D12  D1 D2
Y D1d 2  d1 D2

X D1 P2  P1 D2
This gradient is independent of f
showing that the plot is linear for all
mixing fractions.
This theory applies to a mix without subsequent decay.
MIXING THEORY [with subsequent decay]

d  Pm 1  e  t

The mixing equations now become:
Pm  fP1  1  f P2  d
The isochron plots
then become:
the line gradient is
Y
d m  fd1  1  f d 2  d
dm
fd  1  f d 2  d
 1
Dm
fD1  1  f D2
X
Dm  fD1  1  f D2
Pm
fP  1  f P2  d
 1
Dm
fD1  1  f D2
Y D1d 2  d1 D2  d D1  D2 

X D1 P2  P1 D2  d D1  D2 
This gradient is independent of f showing that the plot is linear for all mixing fractions.
The gradient of the line cannot be used to calculate an age for the rock.
This theory applies to a mix with subsequent decay.
Detecting rock mixing
This is not at all easy and can only be done with a simple two component
mix, assuming that the reference daughter isotope concentration is the
same in each sample. This criterion is not met for general mixing.
Conclusion
Isochron dating must be considered as being unreliable simply because a straight
line plot is indistinguishable from a mixing line, and there is no foolproof method of
distinguishing between a true isochron and a mixing line.
Geologists therefore can “choose” isochron derived dates that are in
agreement with the “expected” age of the rock.
Uranium-lead-thorium dating
This is a very complicated dating technique as there are three extended decay chains
involved and several methods of dealing with the data.
235
92
U
238
92
207
82
Pb
U
206
82
Pb
Th
208
82
Pb
232
90
All stable lead isotopes that
result from single decay chains.
The intermediate isotopes all have short half lives so the processes can be
treated as single decays, providing that the whole decay chain is in equilibrium.
Lead has another non-radiogenic isotope 204
which is used as a
82 Pb
measurement reference to form isochron type equations.
This is the oldest form of radiometric dating.
235
92
U
decay series
238
92
U
decay series
232
90
Th
decay series
Uranium lead dating uses equations of the form:
d  d 0  P t
    e  1
D  D0  D


This is for the three radioactive isotopes that produce
lead. The zero subscript indicates the initial ratio.
This rearranges to give:
1 
t  ln
 
d
D
 Dd00
P
D

 1


Three dates can be calculated for the three isotopes,
but the initial d/D ratio must be assumed.
Also, the U/Pb system must be closed, i.e. no gain or loss of parent or daughter.
Faure states that: “most minerals are not closed systems” p208 Principles of Isoptope Geology.
Concordia diagrams
These are used to identify U/Pb loss or gain at a specific time as in a closed
system any plot of the isotope ratios should lie on the Concordia line.
The discordia line
intercepts should
show the time since
closure and the time
since crystallisation.
However, U/Pb loss by diffusion over time will produce a fictitious Discordia line
which has no dating significance. (p297 Principles of Isotope Geology)
LEAD-LEAD DATING
This technique uses isotope ratio measurements of lead 204, 206 and 207 to estimate the
age of the Earth and also meteorites.
The classic is the “Holmes-Houtermans model”, which assumes:
1.
2.
3.
4.
5.
6.
The Earth was originally molten and homogenous (evenly mixed).
U, Th and Pb were uniformly distributed.
The isotopic composition of lead was the same everywhere.
After solidification “small regional differences” arose in the U/Pb ratio (how?).
Subsequently in any given region the U/Pb ratio only changed due to decay.
At the time of formation of a mineral (e.g. galena) the Pb was separated from
U and Th and its isotopic composition has remained constant ever since.
This model does not produce very good results when used.
The next version is the “Stacey-Kramers” model which assumes:
1. The “evolution” of lead started 4.57 Ga years ago.
2. At a more recent date (3.7 Ga) the U/Pb ratio was changed by geochemical differentiation
and has remained constant since then.
This model produces better results when used, but still relies upon huge assumptions.
All the main radioisotope dating techniques highlighted so far have common features:
1.
2.
3.
4.
A long age history of the Earth is assumed.
The formation mechanism and history of the rocks is assumed.
The isotope ratio measurements are interpreted in terms of 1. & 2.
The calculated ages are very large.
An analytical method such as this is a classic case of circular reasoning.
The calculated age of a rock will depend uniquely on the mathematical model
used, which in turn will depend uniquely on the assumptions made about the
rock formation, history and likely age of the rock.
Radiometric dating is therefore not normal operational science but uses a variety of
forensic techniques [based on accurate physics measurements now], which can only
suggest rock ages based on geological models of rock history.
In fairness to other evidence; If the Earth started as a molten blob then it would have
taken at least 20 Ma to cool, apart from any internal radioactive heating.
What is the conflict between conventional geology and Biblical teaching?
GEOLOGY
Old universe
Old solar system
Old Earth
BIBLE
Young universe
Young solar system
Young Earth
There is disagreement among sincere Christians regarding the true interpretation of the
Genesis account of creation. Some Christians who are qualified scientists think that the
days in Genesis 1 refer to long periods of time whereas Christians who adopt a literal
translation of Genesis will believe that God created everything in six 24hr periods.
THE FLOOD & NOAH
If there was a global flood about 4000 years ago, then this would
have caused severe disruption to the Earth’s crustal rocks. The
Genesis account indicates that the “fountains of the great deep
were broken up”. Almost all sedimentary rocks would have been
deposited at this time. The geological significance of this is that all
conventional radiometric dating assumptions would be changed.
CARBON DATING
All living organisms contain carbon.
This carbon has three isotopes. One of these is radioactive.
C14 half life
5730 years
in the atmosphere
99%
1%
1 part in 1012
When an organism dies, the carbon-14 decays, but the other isotopes do not.
Therefore, the carbon isotope ratios in an old sample of organic material
can indicate its age IF the initial isotope ratios are known.
HOW CAN THE ORIGINAL ISOTOPE RATIOS BE FOUND?
HOW FAR BACK CAN CARBON DATING GO?
Carbon-14 is produced from nitrogen-14 in the upper atmosphere by cosmic rays.
The newly produced carbon-14 is soon oxidised to give carbon dioxide which
disperses through the atmosphere and is absorbed by plants to enter the food chain.
SUN
N-14
COSMIC RAYS
ELECTRONS, PROTONS & IONS
C-14 in the
atmosphere forms
an equilibrium
concentration
where the decay
rate is equal to the
production rate.
C-14
CO2
neutrons produced
by cosmic rays
plant
EARTH
HALF LIFE 5730 YEARS
The C14 concentration in the atmosphere would reach equilibrium in about 30,000y
Carbon 14 Dating Schematic
CARBON 14
CARBON 12
C14/C12 ratio in
the organism
when buried
If the C14/C12
ratio is measured
and the initial
ratio is known, the
sample can be
dated.
C14/C12 ratio in
the organism now
After 50,000
years, very
little left
If the carbon isotope ratio is the same in plants as it is in the atmosphere, then the initial
conditions are known for any dead organic matter, and dating can be estimated by
measuring the current carbon isotope ratio.
What are the problems with carbon dating?
1. The atmospheric concentration of C-14 has not been the same in the past as it is now.
2. Plants do not absorb the different carbon isotopes at equal rates.
3. The very low concentration of C-14 means that it is difficult to detect, and any
contamination by more recent organic matter can greatly affect results.
HOWEVER – the dating
technique has been
refined to account for
systematic errors by
calibrating it using
artefacts of known age –
as well as tree rings
[dendrochronology ]
and stalagmites.
each ring represents one year
stalagmites are carbonate deposits
A Simple Mass Spectrometer
Simple Mass Spectrometer Schematic
An Accelerator Mass Spectrometer
capable of detecting
down to 1 atom in 1015
How good is carbon dating in practice?
Up to 4000 years: quite good as the results can be compared with artefacts
and trees etc of a known age enabling empirical calibration.
Beyond 4000 years: the technique is still used but is not as reliable as
there are far fewer artefacts/trees etc of known age to act as references for
atmospheric C14 concentration.
Can carbon dating give us any information about the age of rocks or the Earth?
Not directly – but………
C -14 has been detected in diamonds which are thought to have been formed
millions of years ago. [25x machine threshold].
C -14 has been detected in coal. [450x machine threshold]. Coal is thought to
have been formed at least 2 million years ago [mostly 60MYA].
C -14 has been detected in fossil wood from sandstone in Australia. This
sandstone is thought to have been formed 200 -250 million years ago.
The conclusion from this scientific evidence is that many rock dates
presupposed by secular geologists must be wrong – the presence of
measurable C-14 in these examples absolutely invalidates previous date
estimates. There should be almost none left after 50,000 years.
This means that the dating of the so called geologic column is wrong and
that the embedded fossils cannot be millions of years old.
The Geologic Column
This is a schematic
diagram of the
sedimentary rock layers
that cover about 75% of
the Earth’s land surface.
There is an apparent
nice timeline showing the
supposed evolution of
animal life.
THIS IS ALL PURE FICTION
The dates cannot be correct
and there are very, very few
fossils of higher vertebrates.
The vast majority of fossils
are of marine organisms.
All fossils were rapidly
buried.
GENERAL CONCLUSIONS
K/Ar dating gives very unreliable results, especially for younger rocks.
Rb/Sr isochrons cannot be distinguished from meaningless mixing lines.
All isochron techniques are therefore suspect.
U/Pb dating methods cannot rely on closed rock systems so all dating
techniques attempt to account for this with very variable success.
Long age dating is not an exact science and relies on assumed rock histories
and invariant decay rates. It may or may not be correct.
Carbon dating has revealed the young age of the geologic column and has
therefore invalidated the so-called fossil record as proof of evolution.
THE RATE PROJECT
Radioisotopes and the Age of the Earth (RATE)
Recent experiments commissioned by the RATE project1 indicate that "1.5 billion
years" worth of nuclear decay took place in one or more short episodes between
4,000 and 14,000 years ago. The results strongly support our accelerated decay
hypothesis, that episodes with billion-fold speed-ups of nuclear decay occurred in
the recent past, such as during the Genesis flood, the Fall of Adam, or early
Creation week. Such accelerations would shrink the alleged 4.5 billion year
radioisotope age of the Earth down to the 6,000 years that a straightforward
reading of the Bible gives.
These experimental results are as yet provisional evidence, as a sound
theoretical model for accelerated decay has not yet been finalised.
Can radiometric dating……….
Prove that the earth is 4.6 billion years old?
NO
Prove that the earth is 6000 years old?
NO
Prove that most fossils are very old?
NO
What you believe about the past depends on your assumptions.
Scientific methods cannot tell us exactly what happened in the past –
they can only provide data that is or is not consistent with any theory
about past events.
Thank you for listening.
I hope that your understanding of radiometric
dating is better than it was.