How Science Figured Out the Age of Earth - Scientific American

Radiometric Dating

earth age radiometric dating

Some individuals have suggested that the speed of light must have been different in the past, and that the starlight has not really taken so long to reach us. So to assume that the K-Ar dates, Rb-Sr dates, and U-Pb dates all reflect the age of the lava, one would have to assume that this lava had no Sr, no Pb, and that all the argon escaped when the beads formed. Layering of Elec-trical Conductivity. Woodmorappe is clearly misusing illite and glauconite dates to simply pad his list.

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Dinosaur Bone Illium bone of an Acrocanthosarus Radio carbon dated at 19, years old! Rutherford assumed that the rate of decay of radium as determined by Ramsay and Soddy was accurate, and that helium did not escape from the sample over time. First, let us examine the results of this "dating method. Some people have tried to defend a young Earth position by saying that the half-lives of radionuclides can in fact be changed, and that this can be done by certain little-understood particles such as neutrinos, muons, or cosmic rays. Such changes can also take place at relatively low temperatures. Because of this, the Septuagint adds in extra time. Furthermore, it is possible that the craters were chosen as those for which the dating methods agreed.

The Himalayan mountains are said by most modern scientists to have started their uplift or orogeny some 50 million years ago. However, recently in Yang Wang et. Dalrymple's work 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: If the present data are representative, argon of slightly anomalous composition can be expected in approximately one out of three volcanic rocks. Dalrymple may have a point. It seems like rocks dating within one or two million years cannot be accurately dated by K-Ar techniques just because of the relatively wide ranges of error. However, can rocks that are tens or hundreds of millions of years be more accurately dated? Perhaps, if these rocks were in fact closed systems and were not subject to contamination by external argon.

Investigators also have found that excess 40 Ar is trapped in the minerals within lava flows. The obvious conclusion most investigators have reached is that the excess 40 Ar had to be present in the molten lavas when extruded, which then did not completely degas as they cooled, the excess 40 Ar becoming trapped in constituent minerals and the rock fabrics themselves.

However, from whence comes the excess 40 Ar, that is, 40 Ar which cannot be attributed to atmospheric argon or in situ radioactive decay of 40 K? It is not simply "magmatic" argon? Funkhouser and Naughton found that the excess 40 Ar in the Hualalai flow, Hawaii, resided in fluid and gaseous inclusions in olivine, plagioclase, and pyroxene in ultramafic xenoliths in the basalt, and was sufficient to yield "ages" of 2.

Many recent studies confirm the mantle source of excess 40 Ar. Hawaiian volcanism is typically cited as resulting from a mantle plume, most investigators now conceding that excess 40 Ar in the lavas, including those from the active Loihi and Kilauea volcanoes, is indicative of the mantle source area from which the magmas came.

Considerable excess 40 Ar measured in ultramafic mantle xenoliths from Kerguelen Archipelago in the southern Indian Ocean likewise is regarded as the mantle source signature of hotspot volcanism.

Further confirmation comes from diamonds, which form in the mantle and are carried by explosive volcanism into the upper crust and to the surface. When Zashu et al. The conventional K-Ar dating method was applied to the dacite flow from the new lava dome at Mount St. Porphyritic dacite which solidified on the surface of the lava dome in gives a whole rock K-Ar 'age' of 0.

Mineral concentrates from the dacite which formed in give K-Ar 'ages 'from 0. These dates are, of course, preposterous. The fundamental dating assumption no radiogenic argon was present when the rock formed is brought into question.

Instead, data from the Mount St. Helens dacite argue that significant "excess" argon was present when the lava solidified in Phenocrysts of orthopyroxene, hornblende and plagioclase are interpreted to have occluded argon within their mineral structures deep in the magma chamber and to have retained this argon after emplacement and solidification of the dacite.

Orthopyroxene retains the most argon, followed by hornblende, and finally, plagioclase. The lava dome at Mount St. Helens dates very much older than its true age because phenocryst minerals inherit argon from the magma.

The study of this Mount St. Helens dacite brings yet another question to mind: How accurate are K-Ar "ages" from the many other phenocryst-containing lava flows world-wide? Potassium is about 2.

Argon is about 3. We can assume then that the magma is probably about 2. Now, Lets say we are trying to date a one billion year old rock. How much of it would be 40 K?

This would leave us with a 0. This gives about 0. This is about one ten millionth of the mass of the rock, a very tiny fraction. If the rock weighed one gram, the Ar in the rock would weight one ten millionth of a gram.

And yet, with a relatively large amount of argon in the air, argon filtering up from rocks below, excess argon in lava, the fact that argon and potassium are water soluble, and the fact that argon is mobile in rock and is a gas, we are still expecting this wisp of argon gas to tell us how old the rock is? The percentage of 40 Ar is even less for younger rocks. For example, it would be about one part in million for rocks in the vicinity of million years old.

However, to get just one part in 10 million of argon in a rock in a thousand years, we would only need to get one part in 10 billion entering the rock each year. This would be less than one part in a trillion entering the rock each day, on the average. This would suffice to give a rock an average computed potassium-argon age of over a billion years. Some geochronologists believe that a possible cause of excess argon is that argon diffuses into certain minerals progressively with time and pressure.

Significant quantities of argon may be introduced into a mineral even at pressures as low as one bar. We can also consider the average abundance of argon in the crust.

This implies a radiometric age of over 4 billion years. So a rock can get a very old radiometric age just by having average amounts of potassium and argon. It seems reasonable to me that the large radiometric ages are simply a consequence of mixing, and not related to ages at all, at least not necessarily the ages of the rocks themselves.

It seems to me to be a certainty that water and gas will enter most, if not all, volcanic type rocks through tiny openings and invalidate almost all K-Ar ages. Rocks are not sealed off from the environment. This contamination would seem to be more and more of a problem the older the rock became. Let me illustrate the circulation patterns of argon in the earth's crust. So argon is being produced throughout the earth's crust, and in the magma, all the time.

In fact, it probably rises to the top of the magma, artificially increasing its concentration there. Now, some rocks in the crust are believed not to hold their argon, so this argon will enter the spaces between the rocks. Leaching also occurs, releasing argon from rocks. Heating of rocks can also release argon. Argon is released from lava as it cools, and probably filters up into the crust from the magma below, along with helium and other radioactive decay products. All of this argon is being produced and entering the air and water in between the rocks, and gradually filtering up to the atmosphere.

So this argon that is being produced will leave some rocks and enter others. Different Dating Methods Agree. It is often said that a great many dating methods, used on a single specimen, will agree with each other, thus establishing the accuracy of the date given. In reality, the overwhelming majority of measurements on the fossil bearing geologic column are all done using one method, the K-Ar method Recall that both potassium and argon are water soluble, and argon a gas is mobile in rock.

Thus the agreement found between many dates does not necessarily reflect an agreement between different methods, but rather the agreement of the K-Ar method with itself Especially noting that Dalrymple suggested that only K-Ar dating methods were at all trust worthy. I have seen no good double-blinded research studies that say otherwise. One would think that if this were a good science, then such studies would be done and published, but they are strangely lacking.

Also, specific differences are known and have been known to exist between different dating methods. For example, Isotopic studies of the Cardenas Basalt and associated Proterozoic diabase sills and dikes have produced a geologic mystery. Using the conventional assumptions of radioisotope dating, the Rb-Sr and K-Ar systems should give concordant "ages".

However, it has been known for over 20 years that the two systems give discordant "ages", the K-Ar "age" being significantly younger than the Rb-Sr "age". The "argon reset model" was the first explanation proposed for the discordance. A metamorphic event is supposed to have expelled significant argon from these rocks.

The reset model is unable to reconcile the new data, leading to a metamorphic event which is excessively young and inconsistent with the conventional stratigraphic interpretation.

The "argon leakage model" also attempts to explain why these rocks have about half the argon which seems to be required by the Rb-Sr system.

The leakage model supposes an incredible improbability. Both the old and new data imply that the rocks leaked argon in nearly exact proportion to the abundance of potassium producing a "leakage isochron", an explanation not supported by a quantity of an appropriate mineral or mesostasis phase. Strong negative correlation between K-Ar model age and K 2 O in the upper portion of the Cardenas Basalt is not easily explained in a consistent manner.

Furthermore, reset and leakage models have difficulty explaining the abundance of initial 36 Ar in the rocks, especially the abundance of 36 Ar in those rocks which supposedly leaked the most 40 Ar. Three alternatives are suggested to the two argon loss models. The "argon inheritance model" and "argon mixing model" simply propose that argon is positively correlated with potassium from its magma source or produced by a mixing process, and that the linear relationship on a plot of 40 Ar versus 40 K is an artifact of the magma, not produced by radioisotope decay within these rocks.

The inheritance of argon seems to be a better model than is the mixing model. All three explanations offered as alternatives to the argon loss models invalidate using the K-Ar system as conventional geochronology would assume. The word "isochron" basically means "same age". Isochron dating is based on the ability to draw a straight line between data points that are thought to have formed at the same time. The slope of this line is used to calculate an age of the sample in isochron radiometric dating.

The isochron method of dating is perhaps the most logically sound of all the dating methods - at first approximation. This method seems to have internal measures to weed out those specimens that are not adequate for radiometric evaluation. Also, the various isochron dating systems seem to eliminate the problem of not knowing how much daughter element was present when the rock formed.

Isochron dating is unique in that it goes beyond measurements of parent and daughter isotopes to calculate the age of the sample based on a simple ratio of parent to daughter isotopes and a decay rate constant - plus one other key measurement.

What is needed is a measurement of a second isotope of the same element as the daughter isotope. Also, several different measurements are needed from various locations and materials within the specimen. This is different from the normal single point test used with the other "generic" methods. To make the straight line needed for isochron dating each group of measurements parent - P, daughter - D, daughter isotope - Di is plotted as a data point on a graph.

The X-axis on the graph is the ratio of P to Di. For example, consider the following isochron graph: Obviously, if a line were drawn between these data points on the graph, there would be a very nice straight line with a positive slope.

Such a straight line would seem to indicate a strong correlation between the amount of P in each sample and the extent to which the sample is enriched in D relative to Di. Obviously one would expect an increase in the ratio of D as compared with Di over time because P is constantly decaying into D, but not into Di. So, Di stays the same while D increases over time.

But, what if the original rock was homogenous when it was made? What if all the minerals were evenly distributed throughout, atom for atom?

What would an isochron of this rock look like? It would look like a single dot on the graph. Because, any testing of any portion of the object would give the same results. The funny thing is, as rocks cool, different minerals within the rock attract certain atoms more than others. Because of this, certain mineral crystals within a rock will incorporate different elements into their structure based on their chemical differences. However, since isotopes of the same element have the same chemical properties, there will be no preference in the inclusion of any one isotope over any other in any particular crystalline mineral as it forms.

So, when put on an isochron graph, each mineral will have the same Y-value. Since a perfectly horizontal line is likely obtained from a rock as soon as it solidifies, such a horizontal line is consistent with a "zero age. Time might still be able to be determined based on changes in the slope of this horizontal line.

As time passes, P decays into D in each sample. That means that P decreases while D increases. This results in a movement of the data points. Each data point moves to the left decrease in P and upwards increase in D. Since radioactive decay proceeds in a proportional manner, the data points with the most P will move the most in a given amount of time.

Thus, the data points maintain their linear arrangement over time as the slope between them increases. The degree of slope can then be used to calculate the time since the line was horizontal or "newly formed". The slope created by these points is the age and the intercept is the initial daughter ratio. The scheme is mathematically sound.

The nice thing about isochrons is that they would seem to be able to detect any sort of contamination of the specimen over time. If any data point became contaminated by outside material, it would no longer find itself in such a nice linear pattern.

Thus, isochrons do indeed seem to contain somewhat of an internal indicator or control for contamination that indicates the general suitability or unsuitability of a specimen for dating. So, it is starting to look like isochron dating has solved some of the major problems of other dating methods. However, isochron dating is still based on certain assumptions. All areas of a given specimen formed at the same time.

The specimen was entirely homogenous when it formed not layered or incompletely mixed. Limited Contamination contamination can form straight lines that are misleading.

Isochrons that are based on intra-specimen crystals can be extrapolated to date the whole specimen. Given these assumptions and the above discussion on isochron dating, some interesting problems arise as one considers certain published isochron dates. So, what exactly is a whole-rock isochron? Whole-rock isochrons are isochrons that are based, not on intra-rock crystals, but on variations in the non-crystalline portions of a given rock.

In other words, sample variations in P are found in different parts of the same rock without being involved with crystalline matrix uptake. This is a problem because the basis of isochron dating is founded on the assumption of original homogeny. If the rock, when it formed, was originally homogenous, then the P element would be equally distributed throughout.

Over time, this homogeny would not change. Thus, any such whole-rock variations in P at some later time would mean that the original rock was never homogenous when it formed. Because of this problem, whole-rock isochrons are invalid, representing the original incomplete mixing of two or more sources. Interestingly enough, whole rock isochrons can be used as a test to see if the sample shows evidence of mixing. If there is a variation in the P values of a whole rock isochron, then any isochron obtained via crystal based studies will be automatically invalid.

The P values of various whole-rock samples must all be the same, falling on a single point on the graph. If such whole-rock samples are identical as far as their P values, mixing would still not be ruled out completely, but at least all available tests to detect mixing would have been satisfied. And yet, such whole-rock isochrons are commonly published.

For example, many isochrons used to date meteorites are most probably the result of mixing since they are based on whole-rock analysis, not on crystalline analysis. There are also methods used to detect the presence of mixing with crystalline isochron analysis. If a certain correlation is present, the isochron may be caused by a mixing. However, even if the correlation is present, it does not mean the isochron is caused by a mixing, and even if the correlation is absent, the isochron could still be caused by a more complex mixing Woodmorappe, , pp.

Therefore such tests are of questionable value. Interestingly, mainstream scientists are also starting to question the validity of isochron dating.

The determination of accurate and precise isochron ages for igneous rocks requires that the initial isotope ratios of the analyzed minerals are identical at the time of eruption or emplacement.

Studies of young volcanic rocks at the mineral scale have shown this assumption to be invalid in many instances. Variations in initial isotope ratios can result in erroneous or imprecise ages.

Nevertheless, it is possible for initial isotope ratio variation to be obscured in a statistically acceptable isochron. Independent age determinations and critical appraisal of petrography are needed to evaluate isotope data. If initial isotope ratio variability can be demonstrated, however, it can be used to constrain petrogenetic pathways. But then,] The cooling history will depend on the volume of magma involved and its starting temperature, which in turn is a function of its composition.

If the initial variation is systematic e. In short, isochron dating is not the independent dating method that it was once thought. As with the other dating methods discussed already, isochron dating is also dependent upon "independent age determinations". Isochrons have been touted by the uniformitarians as a fail-safe method for dating rocks, because the data points are supposed to be self-checking Kenneth Miller used this argument in a debate against Henry Morris years ago.

Now, these geologists, publishing in the premiere geological journal in the world, are telling us that isochrons can look perfect on paper yet give meaningless ages, by orders of magnitude, if the initial conditions are not known, or if the rocks were open systems at some time in the past?! That sounds like what young earth creationists have been complaining about all along. But then, these geologists put a happy face on the situation. The problem is that it is starting to get really difficult to find a truly independent dating method out of all the various dating methods available.

Furthermore, because most upper crustal rocks cooled below annealing temperatures long after their formation, early formed lead rich in Pb is locked in annealed sites so that the leachable component is enriched in recently formed Pb The isotopic composition of the leachable lead component then depends more on the cooling history and annealing temperatures of each host mineral than on their geological age; and the axiom that Pb isotopes cannot be fractionated in the natural environment, is invalid.

Although these experiments are based on a strong Hf attack on zircons, we believe, given the widespread U anomalies of several hundred percent observed in groundwater Osmond and Cowart , that they apply to the differential mobility of radiogenic Pb isotopes on a local and global scale. Also, consider the following excerpt concerning ancient zirons from the Gabbro-Peridotite Complex of the Mar: Zircon age calculations on the base of Upb systematics have been complicated by high share of common Pb and uncertainty of its isotope composition.

Common lead was captured in the process of zircon crystallization, perhaps, by mineral and fluid inclusions. But there is a small share of inherited zircon substance with the age of 3. Thus, the discordia itself obtained by us is interpreted as a result of mixture of newly formed young zircon with some share of Archean zircon presented in each studied crystal. Also, if errors for individual zircon tests are too large, these values are simply discarded.

This enhances the mobility of U and especially Pb. So, how confident can one be in zircon dates who's published Pb levels range from very high to very low? It seems to me that quite often published U-Pb and Pb-Pb dates do in fact involve fairly significant Pb levels. Of course, if the level of Pb is too high, the data obtained is not calibrated, but is simply discarded.

Doesn't this mess up the idea that all lead in zircons must be the result of radioactive decay? It is also of interest in regard to radiometric dating that Robert Gentry claims to have found "squashed" polonium haloes as well as embryonic uranium radiohaloes in coal deposits from many geological layers claimed to be hundreds of millions of years old.

These haloes represent particles of polonium and uranium, which penetrated into the coal at some point and produced a halo by radioactive decay. The fact that they are squashed indicates that part of the decay process began before the material was compressed, so the polonium had to be present before compression. Since coal is relatively incompressible, Gentry concludes that these particles of uranium and polonium must have entered the deposit before it turned to coal.

However, there is only a very small amount of lead with the uranium; if the uranium had entered hundreds of millions of years ago, then there should be much more lead. However, it's just hard to believe, according to conventional geological time scales, that this coal was compressed any time within the past several thousand or even hundred million years.

Some have argued that "radon that results from uranium decay is an inert gas and may have escaped, resulting in little lead being deposited. This would make the observed haloes consistent with an old age for the coal. In addition, not all of the radon would be on the surface of the particles of uranium.

That which was inside or bordering on coal would likely not be able to escape. Since radon has a half-life of about 4 days, it would not have much time to escape, in any event. What happens when something is dated as being very old, but shows little or no physical signs of relative aging?

This basalt group is rather large covering an area of , square kilometers and fills a volume of , cubic kilometers. The vast extent and sheer volume of such individual flows are orders of magnitude larger than anything ever recorded in known human history. Within this group are around individual lava flows each of rather uniform thickness over many kilometers with several extending up to kilometers from their origin.

TL dating and its related techniques have been cross calibrated with samples of known historical age and with radiocarbon and thorium dating. While TL dating does not usually pinpoint the age with as great an accuracy as these other conventional radiometric dating, it is most useful for applications such as pottery or fine-grained volcanic dust, where other dating methods do not work as well. Electron spin resonance ESR. Also called electron paramagnetic resonance, ESR dating also relies on the changes in electron orbits and spins caused by radioactivity over time.

However, ESR dating can be used over longer time periods, up to two million years, and works best on carbonates, such as in coral reefs and cave deposits. It has also seen extensive use in dating tooth enamel. This dating method relies on measuring certain isotopes produced by cosmic ray impacts on exposed rock surfaces.

Because cosmic rays constantly bombard meteorites flying through space, this method has long been used to date the ' flight time' of meteorites--that is the time from when they were chipped off a larger body like an asteroid to the time they land on Earth. The cosmic rays produce small amounts of naturally-rare isotopes such as neon and helium-3, which can be measured in the laboratory.

The cosmic-ray exposure ages of meteorites are usually around 10 million years, but can be up to a billion years for some iron meteorites. In the last fifteen years, people have also used cosmic ray exposure ages to date rock surfaces on the Earth. This is much more complicated because the Earth's magnetic field and atmosphere shield us from most of the cosmic rays. Cosmic ray exposure calibrations must take into. Nevertheless, terrestrial cosmic-ray exposure dating has been shown to be useful in many cases.

We have covered a lot of convincing evidence that the Earth was created a very long time ago. The agreement of many different dating methods, both radiometric and non-radiometric, over hundreds of thousands of samples, is very convincing. Yet, some Christians question whether we can believe something so far back in the past.

My answer is that it is similar to believing in other things of the past. It only differs in degree. Why do you believe Abraham Lincoln ever lived?

Because it would take an extremely elaborate scheme to make up his existence, including forgeries, fake photos, and many other things, and besides, there is no good reason to simply have made him up. Well, the situation is very similar for the dating of rocks, only we have rock records rather than historical records. The last three points deserve more attention. Some Christians have argued that something may be slowly changing with time so all the ages look older than they really are.

The only two quantities in the exponent of a decay rate equation are the half-life and the time. So for ages to appear longer than actual, all the half-lives would have to be changing in sync with each other.

One could consider that time itself was changing if that happened remember that our clocks are now standardized to atomic clocks! Beyond this, scientists have now used a "time machine" to prove that the half-lives of radioactive species were the same millions of years ago. This time machine does not allow people to actually go back in time, but it does allow scientists to observe ancient events from a long way away.

The time machine is called the telescope. Because God's universe is so large, images from distant events take a long time to get to us. Telescopes allow us to see supernovae exploding stars at distances so vast that the pictures take hundreds of thousands to millions of years to arrive at the Earth. So the events we see today actually occurred hundreds of thousands to millions of years ago.

And what do we see when we look back in time? Much of the light following a supernova blast is powered by newly created radioactive parents. So we observe radiometric decay in the supernova light. The half-lives of decays occurring hundreds of thousands of years ago are thus carefully recorded! These half-lives completely agree with the half-lives measured from decays occurring today.

We must conclude that all evidence points towards unchanging radioactive half-lives. Some individuals have suggested that the speed of light must have been different in the past, and that the starlight has not really taken so long to reach us.

However, the astronomical evidence mentioned above also suggests that the speed of light has not changed, or else we would see a significant apparent change in the half-lives of these ancient radioactive decays. Some doubters have tried to dismiss geologic dating with a sleight of hand by saying that no rocks are completely closed systems that is, that no rocks are so isolated from their surroundings that they have not lost or gained some of the isotopes used for dating.

Speaking from an extreme technical viewpoint this might be true--perhaps 1 atom out of 1,,,, of a certain isotope has leaked out of nearly all rocks, but such a change would make an immeasurably small change in the result.

The real question to ask is, "is the rock sufficiently close to a closed system that the results will be same as a really closed system? These books detail experiments showing, for a given dating system, which minerals work all of the time, which minerals work under some certain conditions, and which minerals are likely to lose atoms and give incorrect results.

Understanding these conditions is part of the science of geology. Geologists are careful to use the most reliable methods whenever possible, and as discussed above, to test for agreement between different methods. Some people have tried to defend a young Earth position by saying that the half-lives of radionuclides can in fact be changed, and that this can be done by certain little-understood particles such as neutrinos, muons, or cosmic rays.

This is stretching it. While certain particles can cause nuclear changes, they do not change the half-lives. The nuclear changes are well understood and are nearly always very minor in rocks. In fact the main nuclear changes in rocks are the very radioactive decays we are talking about. There are only three quite technical instances where a half-life changes, and these do not affect the dating methods we have discussed.

Only one technical exception occurs under terrestrial conditions, and this is not for an isotope used for dating. According to theory, electron-capture is the most likely type of decay to show changes with pressure or chemical combination, and this should be most pronounced for very light elements.

The artificially-produced isotope, beryllium-7 has been shown to change by up to 1. In another experiment, a half-life change of a small fraction of a percent was detected when beryllium-7 was subjected to , atmospheres of pressure, equivalent to depths greater than miles inside the Earth Science , , All known rocks, with the possible exception of diamonds, are from much shallower depths.

In fact, beryllium-7 is not used for dating rocks, as it has a half-life of only 54 days, and heavier atoms are even less subject to these minute changes, so the dates of rocks made by electron-capture decays would only be off by at most a few hundredths of a percent. Physical conditions at the center of stars or for cosmic rays differ very greatly from anything experienced in rocks on or in the Earth. Yet, self-proclaimed "experts" often confuse these conditions.

Cosmic rays are very, very high-energy atomic nuclei flying through space. The electron-capture decay mentioned above does not take place in cosmic rays until they slow down. This is because the fast-moving cosmic ray nuclei do not have electrons surrounding them, which are necessary for this form of decay. Another case is material inside of stars, which is in a plasma state where electrons are not bound to atoms. In the extremely hot stellar environment, a completely different kind of decay can occur.

This has been observed for dysprosium and rhenium under very specialized conditions simulating the interior of stars Phys. All normal matter, such as everything on Earth, the Moon, meteorites, etc. As an example of incorrect application of these conditions to dating, one young-Earth proponent suggested that God used plasma conditions when He created the Earth a few thousand years ago.

This writer suggested that the rapid decay rate of rhenium under extreme plasma conditions might explain why rocks give very old ages instead of a young-Earth age. This writer neglected a number of things, including: More importantly, b rocks and hot gaseous plasmas are completely incompatible forms of matter! The material would have to revert back from the plasma state before it could form rocks. In such a scenario, as the rocks cooled and hardened, their ages would be completely reset to zero as described in previous sections.

That is obviously not what is observed. The last case also involves very fast-moving matter. It has been demonstrated by atomic clocks in very fast spacecraft. These atomic clocks slow down very slightly only a second or so per year as predicted by Einstein's theory of relativity. No rocks in our solar system are going fast enough to make a noticeable change in their dates.

These cases are very specialized, and all are well understood. None of these cases alter the dates of rocks either on Earth or other planets in the solar system. The conclusion once again is that half-lives are completely reliable in every context for the dating of rocks on Earth and even on other planets.

The Earth and all creation appears to be very ancient. It would not be inconsistent with the scientific evidence to conclude that God made everything relatively recently, but with the appearance of great age, just as Genesis 1 and 2 tell of God making Adam as a fully grown human which implies the appearance of age. This idea was captured by Phillip Henry Gosse in the book, " Omphalos: The idea of a false appearance of great age is a philosophical and theological matter that we won't go into here.

The main drawback--and it is a strong one--is that this makes God appear to be a deceiver. Certainly whole civilizations have been incorrect deceived? Whatever the philosophical conclusions, it is important to note that an apparent old Earth is consistent with the great amount of scientific evidence.

As Christians it is of great importance that we understand God's word correctly. Yet from the middle ages up until the s people insisted that the Bible taught that the Earth, not the Sun, was the center of the solar system.

It wasn't that people just thought it had to be that way; they actually quoted scriptures: I am afraid the debate over the age of the Earth has many similarities. But I am optimistic. Today there are many Christians who accept the reliability of geologic dating, but do not compromise the spiritual and historical inerrancy of God's word. While a full discussion of Genesis 1 is not given here, references are given below to a few books that deal with that issue. There are a number of misconceptions that seem especially prevalent among Christians.

Most of these topics are covered in the above discussion, but they are reviewed briefly here for clarity. Radiometric dating is based on index fossils whose dates were assigned long before radioactivity was discovered. This is not at all true, though it is implied by some young-Earth literature. Radiometric dating is based on the half-lives of the radioactive isotopes.

These half-lives have been measured over the last years. They are not calibrated by fossils. No one has measured the decay rates directly; we only know them from inference. Decay rates have been directly measured over the last years.

In some cases a batch of the pure parent material is weighed and then set aside for a long time and then the resulting daughter material is weighed. In many cases it is easier to detect radioactive decays by the energy burst that each decay gives off. For this a batch of the pure parent material is carefully weighed and then put in front of a Geiger counter or gamma-ray detector. These instruments count the number of decays over a long time.

If the half-lives are billions of years, it is impossible to determine them from measuring over just a few years or decades. The example given in the section titled, "The Radiometric Clocks" shows that an accurate determination of the half-life is easily achieved by direct counting of decays over a decade or shorter.

This is because a all decay curves have exactly the same shape Fig. Additionally, lavas of historically known ages have been correctly dated even using methods with long half-lives. Most of the decay rates used for dating rocks are known to within two percent.

Such small uncertainties are no reason to dismiss radiometric dating. Whether a rock is million years or million years old does not make a great deal of difference. A small error in the half-lives leads to a very large error in the date. Since exponents are used in the dating equations, it is possible for people to think this might be true, but it is not. This is not true in the context of dating rocks. Radioactive atoms used for dating have been subjected to extremes of heat, cold, pressure, vacuum, acceleration, and strong chemical reactions far beyond anything experienced by rocks, without any significant change.

The only exceptions, which are not relevant to dating rocks, are discussed under the section, "Doubters Still Try", above. A small change in the nuclear forces probably accelerated nuclear clocks during the first day of creation a few thousand years ago, causing the spuriously old radiometric dates of rocks.

Rocks are dated from the time of their formation. For it to have any bearing on the radiometric dates of rocks, such a change of nuclear forces must have occurred after the Earth and the rocks were formed.

To make the kind of difference suggested by young-Earth proponents, the half-lives must be shortened from several billion years down to several thousand years--a factor of at least a million. But to shorten half-lives by factors of a million would cause large physical changes. As one small example, recall that the Earth is heated substantially by radioactive decay.

If that decay is speeded up by a factor of a million or so, the tremendous heat pulse would easily melt the whole Earth , including the rocks in question! No radiometric ages would appear old if this happened.

The decay rates might be slowing down over time, leading to incorrect old dates. There are two ways we know this didn't happen: We should measure the "full-life" the time at which all of the parent is gone rather than the half-life the time when half of it is gone.

Unlike sand in an hourglass, which drops at a constant rate independent of how much remains in the top half of the glass, the number of radioactive decays is proportional to the amount of parent remaining.

A half-life is more easy to define than some point at which almost all of the parent is gone. Scientists sometimes instead use the term "mean life", that is, the average life of a parent atom. For most of us half-life is easier to understand. To date a rock one must know the original amount of the parent element. But there is no way to measure how much parent element was originally there. It is very easy to calculate the original parent abundance, but that information is not needed to date the rock.

All of the dating schemes work from knowing the present abundances of the parent and daughter isotopes. There is little or no way to tell how much of the decay product, that is, the daughter isotope, was originally in the rock, leading to anomalously old ages.

A good part of this article is devoted to explaining how one can tell how much of a given element or isotope was originally present. Usually it involves using more than one sample from a given rock. It is done by comparing the ratios of parent and daughter isotopes relative to a stable isotope for samples with different relative amounts of the parent isotope. From this one can determine how much of the daughter isotope would be present if there had been no parent isotope.

This is the same as the initial amount it would not change if there were no parent isotope to decay. Figures 4 and 5, and the accompanying explanation, tell how this is done most of the time. This article has listed and discussed a number of different radiometric dating methods and has also briefly described a number of non-radiometric dating methods.

There are actually many more methods out there. Well over forty different radiometric dating methods are in use, and a number of non-radiogenic methods not even mentioned here. This refers to tiny halos of crystal damage surrounding spots where radioactive elements are concentrated in certain rocks. Halos thought to be from polonium, a short-lived element produced from the decay of uranium, have been found in some rocks.

A plausible explanation for a halo from such a short-lived element is that these were not produced by an initial concentration of the radioactive element. Rather, as water seeped through cracks in the minerals, a chemical change caused newly-formed polonium to drop out of solution at a certain place and almost immediately decay there.

A halo would build up over a long period of time even though the center of the halo never contained more than a few atoms of polonium at one time. Other researchers have found halos produced by an indirect radioactive decay effect called hole diffusion, which is an electrical effect in a crystal. These results suggest that the halos in question are not from short-lived isotopes after all.

At any rate, halos from uranium inclusions are far more common. Because of uranium's long half-lives, these halos take at least several hundred million years to form. Because of this, most people agree that halos provide compelling evidence for a very old Earth.

A young-Earth research group reported that they sent a rock erupted in from Mount Saint Helens volcano to a dating lab and got back a potassium-argon age of several million years. This shows we should not trust radiometric dating. There are indeed ways to "trick" radiometric dating if a single dating method is improperly used on a sample. Anyone can move the hands on a clock and get the wrong time. Likewise, people actively looking for incorrect radiometric dates can in fact get them. Geologists have known for over forty years that the potassium-argon method cannot be used on rocks only twenty to thirty years old.

Publicizing this incorrect age as a completely new finding was inappropriate. The reasons are discussed in the Potassium-Argon Dating section above. Be assured that multiple dating methods used together on igneous rocks are almost always correct unless the sample is too difficult to date due to factors such as metamorphism or a large fraction of xenoliths.

Low abundances of helium in zircon grains show that these minerals are much younger than radiometric dating suggests. Zircon grains are important for uranium-thorium-lead dating because they contain abundant uranium and thorium parent isotopes. Helium is also produced from the decay of uranium and thorium. However, as a gas of very small atomic size, helium tends to escape rather easily. Researchers have studied the rates of diffusion of helium from zircons, with the prediction from one study by a young- Earth creationist suggesting that it should be quantitatively retained despite its atomic size.

The assumptions of the temperature conditions of the rock over time are most likely unrealistic in this case. The fact that radiogenic helium and argon are still degassing from the Earth's interior prove that the Earth must be young. The radioactive parent isotopes, uranium and potassium, have very long half-lives, as shown in Table 1. These parents still exist in abundance in the Earth's interior, and are still producing helium and argon.

There is also a time lag between the production of the daughter products and their degassing. If the Earth were geologically very young, very little helium and argon would have been produced. One can compare the amount of argon in the atmosphere to what would be expected from decay of potassium over 4.

The waters of Noah's flood could have leached radioactive isotopes out of rocks, disturbing their ages. This is actually suggested on one website! While water can affect the ability to date rock surfaces or other weathered areas, there is generally no trouble dating interior portions of most rocks from the bottom of lakes, rivers, and oceans. Additionally, if ages were disturbed by leaching, the leaching would affect different isotopes at vastly different rates.

Ages determined by different methods would be in violent disagreement. If the flood were global in scope, why then would we have any rocks for which a number of different methods all agree with each other?

In fact, close agreement between methods for most samples is a hallmark of radiometric dating. We know the Earth is much younger because of non-radiogenic indicators such as the sedimentation rate of the oceans. There are a number of parameters which, if extrapolated from the present without taking into account the changes in the Earth over time, would seem to suggest a somewhat younger Earth.

These arguments can sound good on a very simple level, but do not hold water when all the factors are considered.

Some examples of these categories are the decaying magnetic field not mentioning the widespread evidence for magnetic reversals , the saltiness of the oceans not counting sedimentation! While these arguments do not stand up when the complete picture is considered, the case for a very old creation of the Earth fits well in all areas considered. The fact is that there are a number of Bible-believing Christians who are involved in radiometric dating, and who can see its validity firsthand.

A great number of other Christians are firmly convinced that radiometric dating shows evidence that God created the Earth billions, not thousands, of years ago. This is not true at all. The fact that dating techniques most often agree with each other is why scientists tend to trust them in the first place. Nearly every college and university library in the country has periodicals such as Science , Nature , and specific geology journals that give the results of dating studies.

The public is usually welcome to and should! So the results are not hidden; people can go look at the results for themselves. Over a thousand research papers are published a year on radiometric dating, essentially all in agreement. Besides the scientific periodicals that carry up-to-date research reports, specific suggestions are given below for further reading, both for textbooks, non-classroom books, and web resources.

Resources On the Web: Virtual Dating--a very helpful educational course on half-lives and radioactive decay was put together by Gary Novak at California State University in Los Angeles. This site has several interactive web "workbooks" to help the reader understand various concepts involved with radiometricdating.

Reasons to Believe--a Christian ministry supporting the old-Earth viewpoint. Hugh Ross, the founder and head of the ministry, holds a PhD in Astronomy. The ministry supports an accurate interpretation of the Bible while also supportive of science as a tool to study God's creation.

Most of the members hold an old-Earth view, though membership is open to anyone supporting their positional statement. This website has numerous resources on theology and Bible-science issues. There is a wealth of information, including presentations on the interpretation of Genesis chapters , a resource list of apologetics ministries, etc. A review of Phillip Henry Gosse's Omphalos: An Attempt to Untie the Geological Knot , in which fiat creation with the appearance of age is suggested.

Origins--this site is devoted mainly to evidences for intelligent design in nature. Talk Origins--an archive dedicated to creation-evolution issues. It includes separate resource sections on the reliability of radiometric dating, introductory articles, advanced articles, radiocarbon dating, etc.

C Dating--The radiocarbon laboratories at Oxford England and Waikato New Zealand Universities jointly operate this website which gives very comprehensive information on radiocarbon dating. Portions of it were written specifically for use by K students, so it is easy to understand. The site contains explanations on measurements, applications, calibration, publications, and other areas.

Cornell University Geology Lecture Notes--A large number of pdf files of geology lecture notes are available on the web. These are university-level lecture notes describing radiometric dating and related topics. The following books are popular college-level Geology texts that deal in depth with various dating techniques. Geologic Time is very easy to read and has been around for quite some time. The text by Dalrymple is meant to be relatively easy to read, but is also very comprehensive.

The Faure and Dickin texts are regular textbooks for Geology, including more mathematics and more details. Cambridge University Press, pp. Brent The Age of the Earth.

Stanford University Press, pp. AComprehensive Textbook for Geology Students. Faure, Gunter Principles of Isotope Geology , 2nd edition. Wiley, New York, pp.

Atheneum Books, New York, 92 pp. This is a book designed for easy reading on the general subject of dating. This short book covers topics from archeology to tree ring dating to radiocarbon dating of the dead sea scrolls, to dating of meteorites and moon rocks.

The book is out of print, but slightly used copies can be obtained from online dealers like Amazon. Springer-Verlag, New York, pp. This book is a quite comprehensive reference on all methods for determining dates less than about a million years old.

Prometheus Books, Buffalo, pp. This book is a very thorough and comprehensive refutation of young-Earth ideas, written by a non-Christian. The only negative aspect is that at one point Strahler throws in a bit of his own theology--his arguments against the need for a God. This book is long and in small print; it covers a wealth of information. For ice core studies, the Journal of Geophysical Research, volume , starting with page 26,, has 47 papers on two deep ice cores drilled in central Greenland.

Books on scripture, theology, and science: He addresses typical objections brought up by young-Earth adherents, including the death of animals before Adam and Eve's sin, entropy or decay before the fall, the six days of creation, and the flood.

This is a very readable theological book about Genesis. Sailhamer has served on the translation committees for two versions of the book of Genesis. Ross, Hugh Creation and Time: Hugh Ross has a PhD in Astronomy. In this book Dr. Ross defends modern science and an old age for the universe, and refutes common young-Earth arguments. He firmly believes in the inerrancy of the Bible.

Schroeder, Paramount, CA, pp. A persuasive book written for the Christian layman. Stoner uses arguments both from the theological and the scientific side. He talks somewhat philosophically about whether God deceives us with the Genesis account if the Earth is really old. Stoner also tries to discuss the meaning of the Genesis 1 text. Van Till Howard J. This book talks about the misuse of science by both hard-line atheists and by young-Earth creationists.

A good deal of the book is devoted to refuting young-Earth arguments, including a substantial section on the Grand Canyon geology. Its authors are well-known Christians in Geology and Physics. Wiester, John The Genesis Connection. John Wiester has taught Geology at Westmont and Biola University, and is active in the American Scientific Affiliation, an organization of scientists who are Christians. This book discusses many scientific discoveries relating to the age of the Earth and how these fit into the context of Genesis 1.

He argues for an old Earth and refutes many of the common young-Earth claims including their objections to radiometric dating. The following people are sincerely thanked for their contributions to the first edition: Davis Young Calvin College , Dr.

I thank my wife Gwen, and children, Carson and Isaac, for supporting me in this work, and I thank God for giving us the intelligence to understand little bits and pieces of His amazing creation.

More about the author: Wiens received a bachelor's degree in Physics from Wheaton College and a PhD from the University of Minnesota, doing research on meteorites and moon rocks. If bentonite does not always give correlate and correct ages, this calls into question its use for dating the K-T boundary.

Let me briefly comment on a couple of other articles at Tim Thompson's page. This is at least close to what I am looking for. However, it would be better to date all five craters by all four different methods, and see what the agreement is. It is also possible that each crater gives a scatter of dates, and the best ones were selected.

Furthermore, it is possible that the craters were chosen as those for which the dating methods agreed. Possible other sources of correlation Note that if there are small pockets in crystals where both parent and daughter product can accumulate from the lava, then one can inherit correlated ages from the lava into minerals.

Thus even the existence of correlations is not conclusive evidence that a date is correct. Anomalies of radiometric dating If a date does not agree with the expected age of its geologic period, and no plausible explanation can be found, then the date is called anomalous. But if we really understand what is going on, then we should be able to detect discrepant dates as they are being measured, and not just due to their divergence from other dates.

Geologists often say that the percentage of anomalies is low. But there are quite a number of rather outstanding anomalies in radiometric dating that creationists have collected. These anomalies are reported in the scientific literature. For example, one isochron yielded a date of 10 billion years. A Rb-Sr isochron yielded a date of 34 billion years. K-Ar dates of 7 to 15 billion years have been recorded. It's also not uncommon for two methods to agree and for the date to be discarded anyway.

Samples with flat plateaus which should mean no added argon can give wrong dates. Samples giving no evidence of being disturbed can give wrong dates. Samples that give evidence of being disturbed can give correct dates. The number of dates that disagree with the expected ages is not insignificant. I don't know what the exact percentage is. Many dates give values near the accepted ones. But even these often differ from one another by 10 or 20 percent. And quite a few other dates are often much, much farther off.

Whatever is making some of these dates inaccurate could be making all of them inaccurate. Age estimates on a given geological stratum by different radiometric methods are often quite different sometimes by hundreds of millions of years.

There is not absolutely reliable long-term radiological "clock". The uncertainties inherent in radiometric dating are disturbing to geologists and evolutionists As proof of the unreliability of the radiometric methods consider the fact that in nearly every case dates from recent lava flows have come back excessively large.

One example is the rocks from the Kaupelehu Flow, Hualalai Volcano in Hawaii which was known to have erupted in These rocks were dated by a variety of different methods. Of 12 dates reported the youngest was million years and the oldest was 2.

The dates average 1. Another source said that about 5 or 6 of the historic lava flows give ages in the hundreds of thousands of years. Geologists explain the Kaupelehu date by the lava being cooled rapidly in deep ocean water and not being able to get rid of its enclosed argon. Instead, the uncertainty grows as more and more data is accumulated Woodmorappe also mentions that very self-contradictory age spreads in the Precambrian era are common. In addition, Woodmorappe gives over sets of dates "that are in gross conflict with one another and with expected values for their indicated paleontological positions.

This does not include dates from minerals that are thought to yield bad dates, or from igneous bodies with wide biostrategraphic ranges, where many dates are acceptable. He states that the number of dates within range are less than the number of anomalies, except for the Cenozoic and Cretaceous. When one adds in the fact that many anomalies are unreported, which he gives evidence for, the true distribution is anyone's guess.

There have been criticisms of John Woodmorappe's study, but no one has given any figures from the literature for the true percentage of anomalies, with a definition of an anomaly, or the degree of correlation between methods. Steven Schimmrich's review of this study often concerns itself with John W's presentation of geologists explanation for anomalies, and not with the percentage of anomalies; the later is my main concern.

The carbon age of the buried trees is only years, but some of the overlying volcanic material has a ,year potassium-argon age. A similar situation is reported in the December issue of Creation ex nihilo in which lava with a K-Ar age of about 45 million years overlays wood that was carbon dated by 3 laboratories using AMS dating to about 35, years. Still another evidence for problems with radiometric dating was given in a recent talk I attended by a man who had been an evolutionist and taken a course in radiometric dating.

The teacher gave 14 assumptions of radiometric dating and said something like "If creationists got a hold of these, they could cut radiometric dating to pieces. Another evidence that all is not well with radiometric dating is given in the following quote from Coffin p.

Many sedimentary uranium ores are not. Since equilibrium should be reached in 1 million years, this is a problem for sediments that are assumed to be older than 1 million years. On another point, if we can detect minerals that were not molten with the lava, as has been claimed, then this is one more reason why there should be no anomalies, and radiometric dating should be a completely solved problem. But that does not appear to be the case, at least especially on the geologic column. I'm not claiming that anomalous results are being hidden, just that the agreement of a mass of results, none of which has much claim to reliability, does not necessarily mean much.

Picking out a few cases where radiometric dates appear to be well-behaved reminds me of evolutionary biologists focusing on a few cases where there may be transitional sequences. It does not answer the overall question. And as I said above, I'm also interested to know how much of the fossil-bearing geologic column can be dated by isochrons, and how the dates so obtained compare to others.

Gerling et al called attention to some chlorites yielding K-Ar dates of 7 to 15 b. It had been noted that some minerals which yield such dates as beryl, cordierite, etc. They also pointed out that for the anomalies to be accounted for by excess argon, unreasonably high partial pressures of Ar during crystallization would have to be required.

They concluded by suggesting some unknown nuclear process which no longer operates to have generated the Ar. This implies that excess argon is coming from somewhere. Here is another quote from Woodmorappe about isochrons, since some people think that mixing scenarios or other age-altering scenarios are unlikely:. If this condition does not hold, invalid ages and intercepts are obtained.

Models yield isochron ages that are too high, too low, or in the future, sometimes by orders of magnitude. The fact that the only "valid" K-Ar isochrons are those for which the concentration of non-radiogenic argon Ar36 is constant, seems very unusual. This suggests that what is occuring is some kind of a mixing phenomenon, and not an isochron reflecting a true age. We have analyzed several devitrified glasses of known age, and all have yielded ages that are too young.

Some gave virtually zero ages, although the geologic evidence suggested that devitrification took place shortly after the formation of a deposit. Why a low anomaly percentage is meaningless One of the main arguments in favor of radiometric dating is that so many dates agree with each other, that is, with the date expected for their geologic period.

But it's not evident how much support this gives to radiometric dating. If a rock dates too old, one can say that the clock did not get reset. If it dates too young, one can invoke a later heating event. Neither date would necessarily be seen as anomalous.

If lava intrudes upon geologic period X, then any date for the lava of X or later will not be seen as anomalous. And even if the date is one or two geologic periods earlier, it may well be close enough to be accepted as non-spurious. If one does not know the geologic period of a rock by other means, then of course one is likely to date it to find out, and then of course the date agrees with the geologic period and this will not be seen as anomalous.

So it is difficult to know what would be a reasonable test for whether radiometric dating is reliable or not. The percentage of published dates that are considered as anomalous has little bearing on the question. The biostrategraphic limits issue The issue about igneous bodies may need additional clarification. If a lava flow lies above geologic period A and below B, then allowable ages are anything at least as large as A and no larger than B.

This is called the biostratigraphic limit of the flow. Now, according to Woodmorappe's citations, many lava flows have no such limits at all, and most of them have large limits. For example, a flow lying on precambrian rock with nothing on top would have no limits on its dates.

And such flows often have a large internal scatter of dates, but these dates are not considered as anomalies because of the unrestricted biostratigraphic limit. Other flows with wide biostratigraphic limits have weak restrictions on allowable dates. This is one reason why just reporting the percentage of anomalies has little meaning.

Thus these ages, though they generally have a considerable scatter, are not considered as anomalies. He cites another reference that most igneous bodies have wide biostrategraphic limits.

Thus just by chance, many dates will be considered within the acceptable ranges. Again, the percentage of anomalies means nothing for the reliability of radiometric dating. Now, igneous bodies can be of two types, extrusive and intrusive. Extrusive bodies are lava that is deposited on the surface. These cool quickly and have small crystals and form basalt.

Intrusive bodies are deposited in the spaces between other rocks. These cool more slowly and have larger crystals, often forming granite. Both of these tend on the average to have wide biostrategraphic limits, meaning that a large spread of ages will be regarded as non-anomalous. And if we recall that most radiometric dating is done of igneous bodies, one sees that the percentage of anomalies is meaningless.

Thus we really need some evidence that the different methods agree with each other. To make the case even stronger, "Many discrepant results from intrusives are rationalized away immediately by accepting the dates but reinterpreting the biostrategraphic bracket," according to John Woodmorappe. This of course means that the result is no longer anomalous, because the geologic period has been modified to fit the date.

Finally, the fact that the great majority of dates are from one method means that the general but not universal agreement of K-Ar dating with itself is sufficient to explain the small percentange of anomalies if it is small. Preponderance of K-Ar dating Now, the point about agreement is that whatever figure is given about how often ages agree with the expected age, is consistent with the fact that there is no agreement at all between K-Ar and other methods, since so many measurements are done using K-Ar dating.

And one of the strongest arguments for the validity of radiometric dating is that the methods agree. So when one combines all of the above figures, the statement that there are only 10 percent anomalies or 5 percent or whatever, does not have any meaning any more. This statement is made so often as evidence for the reliability of radiometric dating, that the simple evidence that it has no meaning, is astounding to me. I don't object to having some hard evidence that there are real agreements between different methods on the geologic column, if someone can provide it.

The precambrian rock is less interesting because it could have a radiometric age older than life, but this is less likely for the rest of the geologic column. It's not surprising that K-Ar dates often agree with the assumed dates of their geological periods, since the dates of the geological periods were largely inferred from K-Ar dating. By the way, Ar-Ar dating and K-Ar dating are essentially the same method, so between the two of them we obtain a large fraction of the dates being used.

Before the discovery of radioactivity in the late nineteenth century, a geological time scale had been developed on the basis of estimates for the rates of geological processes such as erosion and sedimentation, with the assumption that these rates had always been essentially uniform. On the basis of being unacceptably old, many geologists of the time rejected these early twentieth century determinations of rock age from the ratio of daughter to radioactive parent large.

By , increased confidence in radioisotope dating techniques and the demands of evolution theory for vast amounts of time led to the establishment of an expanded geological time scale. The construction of this time scale was based on about radioisotope ages that were selected because of their agreement with the presumed fossil and geological sequences found in the rocks.

Igneous rocks are particularly suited to K-Ar dating. The crucial determiners are therefore volcanic extrusive igneous rocks that are interbedded with sediments, and intrusive igneous rocks that penetrate sediments. This verifies what I said about almost all of the dates used to define correct ages for geologic periods being K-Ar dates. Also, the uncertainty in the branching ratio of potassium decay might mean that there is a fudge factor in K-Ar ages of up to a third, and that the occasional agreements between K-Ar ages and other ages are open to question.

So the point is that there is now no reason to believe that radiometric dating is valid on the geologic column. I mentioned the presence of excess argon 40 in a sample as a problem leading to artificially old K-Ar dates.

Henke states in a reply to me, concerning the problem of detecting excess argon,. It is possible that such isochrons are not often done. One cannot always use an isochron, since many minerals may have about the same K and Ar40 concentrations, and there may be some fractionation of argon among the minerals.

It's not clear to me if this three dimensional plot always works, and how often it is used. I was not able to find any mention of it in Faure or Dickin It is true that by using additional isotopes if they are sufficiently abundant and do not fractionate , one can often detect mixings of multiple sources. My point was that the usual mixing test can only detect two sources. But since these multiple mixing tests are more difficult and expensive, they may not be done very often.

One also has to know which isotopes to examine. I was suprised that Dalrymple said nothing about mixings invalidating isochrons. Dalrymple goes to great lengths to explain this away, but I think this figure is very telling, and find his explanations unconvincing. It is also remarkable that we have a test for mixing, which is commonly cited in support of the accuracy of radiometric dating, but when it gives contrary results, it is simply ignored.

It is a fundamental assumption of the mantle isochron model that neither isotope nor elemental ratios are perturbed during magma ascent through the crust. However, it is now generally accepted that this assumption is not upheld with sufficient reliability to attribute age significance to erupted isochrons.

Dickin suggests that mixings may contribute to such isochrons. It seems reasonable, then, that mixings may be affecting all Rb-Sr isochrons in igneous rock. Your hypothetical example in "More Bad News for Radiometric Dating" is often hard to follow, but it is clearly invalid. This example is given to show that a mixing of three sources cannot be detected by the usual two sources test. It is not intended to be natural, but to demonstrate a mathematical fact.

There is a lot of flexibility in the design of such examples, as I indicate, and it is reasonable to assume that some of these examples would be natural. It's the responsibility of the geologist to show that such mixings have not occurred.

To really understand what's going on you have to sample the recent works of many different authors. You have to follow arguments between experts on different issues and see where they go. Overall, the geologic time scale is in great shape. Yes, scientists are still making minor adjustments.

However, it's clear from Strahler , Dalrymple , etc. The problem with this approach is that it leaves ample room for the exercise of subjective judgment and evolutionary assumptions.

Also, Dalrymple says essentially nothing about the phanerozoic, and thus gives little evidence of the accuracy of the conventional dating scheme on fossil-bearing rocks. I treated this issue of percentage of anomalies in considerable detail in my original "Radiometric Dating Game" article. It is interesting that Woodmorappe gives a number of cases in which standard geological tests are ignored.

For example, dates may be accepted even when there is evidence of weathering, and rejected when there is not. There may be evidence of heating, but the date may be accepted, and there may be no such evidence, but a hypothetical heating event is assumed anyway.

If geological tests are not being applied consistently, one wonders what value they have. Let me clarify the problem with excess argon. It gives the diffusion equation for argon escaping from a rock as it cools. The rate of diffusion is proportional to the gradient of argon concentration, and increases rapidly with temperature.

Suppose the partial pressure of argon 40 in the environment is p. Suppose the partial pressure of argon 40 in lava or magma is initially at least p, as it cools.

Then the partial pressure of argon 40 in the magma will never decrease below p; excess argon 40 will remain dissolved in the lava or magma as it cools. This argon 40 will then be trapped within the resulting rocks and lead to artificially old K-Ar dates. Now, the problem with this is that this excess argon 40 will probably be deposited as single atoms of argon distributed evenly within the sample. This makes it very difficult or even theoretically impossible to distinguish this excess argon 40 from argon generated by radioactive decay.

This will make the sample appear artificially old right away. Even if crystals exclude argon as they form, argon will rapidly diffuse into them as the lava cools, by the diffusion equation mentioned above. A similar problem can occur if the excess argon 40 dissolved within lava or magma is not able to escape, due to rapid cooling or subsequent deposits of sediment or other lava on top. It is possible that in some cases an isochron might be able to detect such initial argon 40, but this can only happen if the potassium concentration varies significantly within the sample.

It is not clear to me, also, how often such a test for initial argon 40 is performed. And of course, such isochrons can be falsified by mixings or other problems. There are spectrum tests for adsorbed argon involving Ar-Ar dating; basically, one can see whether the argon 40 is concentrated near the surface of the sample or near the interior.

The former would indicated adsorbed argon 40, which would not give a true age. However, this test would not indicate excess argon 40 present during cooling. It seems reasonable to me that this is a uniform problem with K-Ar dating. To me the geological evidence suggests catastrophic conditions and rapid formation of the sedimentary layers in the past. Thus the lava might have been covered before the excess argon was able to escape. Or the lava might have cooled quickly, due to rainfall.

It only needs to cool to about degrees centigrade or less to trap most of the argon, at least for biotite. As I mentioned before, one sometimes finds significant argon 40 in a rock and no potassium at all, as mentioned in Snelling's article.

This shows that excess argon is entering these rocks by some means, and calls K-Ar dating into question. Excess argon could even cause different minerals in a given formation to yield similar K-Ar ages, since they all might have similar concentrations of K, approximately equal to its abundance in the earth's crust, and similar concentrations of argon 40, due to the partial pressure of argon 40 being similar during cooling. Even sedimentary minerals might have a similar K-Ar age for the same reason.

Also, lava magma that cooled within the earth is likely to have artificially old K-Ar ages, since the enclosed excess argon 40 might have a more difficult time escaping. One sedimentary mineral of particular importance for K-Ar dating is glaucony. The following message from a talk. For example, Plaisted's "explanation" for the correlation of isotopic age with vertical position in the geologic column is essentially that excess argon would have existed in lavas in greater quantity early in the Flood, and decreased as it was outgassed over time.

Had Plaisted actually bothered to look at the data e. Glaucony did not come from a "magma chamber," so Plaisted's explanation cannot possibly cover the majority of ages on the younger parts of the column. Of the or so "anomalous" dates in Woodmorappe , 94 Woodmorappe is clearly misusing illite and glauconite dates to simply pad his list. The fact that glauconies are unreliable is significant, since they provide such a large part of the dates for the mesozoic-cenozoic parts of the geological column.

Glauconies are formed in seawater from a variety of materials, and incorporate potassium from the seawater Faure, , p. The process of their formation gives a ready mechanism for their K-Ar ages, namely, the incorporation of argon 40 as well as potassium from the seawater. We can assume that as a result of a global catastrophe, the oceans were highly enriched in argon 40 in the past, and that the concentration of argon 40 gradually decreased over time, due to its diffusion into the atmosphere and due to a smaller amount being released into the seawater.

Therefore older glauconies would absorb more argon 40 from the seawater, resulting in old K-Ar dates for lower strata which become progressively younger for higher strata.

Another factor in this direction is that older glauconies have more time to absorb argon Some minerals contain argon 40 but no potassium, so this indicates excess argon 40, which in the presence of potassium leads to artificially old dates.

Many historical volcanoes give K-Ar dates that are much too old, even if the reasons for this are understood. Finally, I want to comment on the circumstances of the interchange with Dr. During most of our interchange, I was not aware that it would be published on talk. Now it has been web-immortalized on a radiometric dating web page. I was not informed that this exchange had been posted there.

In addition, the complete exchange was not posted, but only a portion of it. I do thank Tim Thomson for the courteous and professional manner in which he has interacted with me, and that he has included the rest of my exchange with Dr. Excuses for anomalies Another issue is that sometimes the geologic periods of rocks are revised to agree with the ages computed.

This also makes data about percentages of anomalies less meaningful. It sometimes seems that reasons can always be found for bad dates, especially on the geologic column. If a rock gives a too old date, one says there is excess argon. If it gives a too young date, one says that it was heated recently, or cannot hold its argon. How do we know that maybe all the rocks have excess argon?

It looks like geologists are taking the "majority view" of K-Ar dating, but there is no necessary reason why the majority of rocks should give the right date. The relationship of a radioisotope age with real-time must be based on an interpretation. A discussion of rubidium-strontium ages in the Isotope Geoscience Section of the journal, Chemical Geology, specifically states that a radioisotope age determination "does not certainly define a valid age information for a geological system.

Any interpretation will reflect the interpreters presuppositions bias. Need for a double-blind test Concerning the need for a double blind test, it would seem that there are many places where human judgment could influence the distribution of measured radiometric dates.

It could increase the percentage of anomalies, if they were regarded as more interesting. It could decrease them, if they were regarded as flukes.

Human judgment could determine whether points were collinear enough to form an isochron. It could determine whether a point can justifiably be tossed out and the remaining points used as an isochron. It could determine whether one should accept simple parent-to-daughter K-Ar ratios or whether some treatment needs to be applied first to get better ages.

It could influence whether a spectrum is considered as flat, whether a rock is considered to have undergone leaching or heating, whether a rock is porous or not, or whether a sample has been disturbed in some way. Since one of the main reasons for accepting radiometric dates at least I keep hearing it is that they agree with each other, I think that geologists have an obligation to show that they do agree, specifically on the geologic column.

Since we do not know whether or how much human judgment is influencing radiometric dating, a double blind study is most reasonable. And it should not be restricted to just one or two well-behaved places, but should be as comprehensive as possible.

Possible changes in the decay rate The following information was sent to me by e-mail:. Radiometric dating is predicated on the assumption that throughout the earth's history radioactive decay rates of the various elements have remained constant. Is this a warranted assumption?

Has every radioactive nuclide proceeded on a rigid course of decay at a constant rate? This has been challenged by studies involving Carbon C At the temperature or pressure, collisions with stray cosmic rays or the emanations of other atoms may cause changes other than those of normal disintegration. It seems very possible that spontaneous disintegration of radioactive elements are related to the action of cosmic rays and the rate of disintegration varying from century to century according to the intensity of the rays.

The evidence for a strongly increasing change in the cosmic ray influx is most favorable especially in light of the decay of the earth's magnetic field.

Most geochronologists maintain that pleochroic haloes give evidence that decay constants have not changed. Crystals of biotite, for example, and other minerals in igneous or metamorphic rocks commonly enclose minute specks of minerals containing uranium or thorium. The a- alpha particles emitted at high velocity by the disintegrating nuclides interact, because of their charge, with electrons of surrounding atoms which slow them down until they finally come to rest in the host material at a distance from their source that depends on their initial kinetic energy and the density and composition of the host.

Where they finally stop to produce lattice distortions and defects there generally occurs discoloring or darkening. Each of the 8 a-particles emitted during the disintegration of U to Pb produces a dark ring in biotite.

Each ring has its own characteristic radius in a given mineral in this case biotite. This radius measures the kinetic energy, hence the probability of emission of the corresponding a-particle and also the half-life of the parent nuclide according to the Geiger-Nuttall law. The Geiger-Nuttall law is an empirical relation between half-life of the a-emitter and the range in air of the emitted a-particles.

If the radii of these haloes from the same nuclide vary, this would imply that the decay rates have varied and would invalidate these series as being actual clocks. Are the radii in the rocks constant in size or are there variable sizes? Most of the early studies of pleochroic haloes were made by Joly and Henderson. Joly concluded that the decay rates have varied on the basis of his finding a variation of the radii for rocks of alleged geological ages.

This rather damaging result was explained away saying that enough evidence of correct radii for defferent geologic periods and sufficient variation in the same period have been obtained that one is forced to look for a different explanation of such variations as were observed by Joly.

Measurements were later made in an excellent collection of samples with haloes. It was found that the extent of the haloes around the inclusions varies over a wide range, even with the same nuclear material in the same matrix, but all sizes fall into definite groups.

The measurements are, in microns, 5,7,10,17,20,23,27, and More recent studies have been made by Robert V. Gentry also finds a variation in the haloes leading him to conclude that the decay constants have not been constant in time. Gentry points out an argument for an instantaneous creation of the earth. He noted form his studies of haloes: For the Po half-life of 3 minutes only a matter of minutes could elapse between the formation of the Po and subsequent crystallization of the mica; otherwise the Po would have decayed, and no ring would be visible.

The occurrence of these halo types is quite widespread, one or more types having been observed in the micas from Canada Pre-Cambrian , Sweden, and Japan. So, then, careful scientists have measured variations in halo radii and their measurements indicate a variation in decay rates. The radioactive series then would have no value as time clocks.

This would knock our C, potassium-argon, and uranium-lead dating measurements into a cocked hat! The age of prehistoric artifacts, the age of the earth, and that of the universe would be thrown into doubt.

Flint, "Radiocarbon Dating," in Science, February 8, , p. This is significant because it is known that neutrinos do interact with the nucleii of atoms, and it is also believed that much of the energy of supernovae is carried away by neutrinos. Isochrons Isochrons are an attempt to avoid the need for an absence of daughter element initially in computing radiometric ages.

The idea is that one has a parent element, X, a daughter element, Y, and another isotope, Z, of the daughter that is not generated by decay. One would assume that initially, the concentration of Z and Y are proportional, since their chemical properties are very similar. Radioactive decay would generate a concentration of Y proportional to X.

So we would obtain an equation of the form. By taking enough measurements of the concentrations of X, Y, and Z, we can solve for c1 and c2, and from c1 we can determine the radiometric age of the sample. If the concentration of K varies in a rock, that it is unlikely for the concentration of added argon 40 to vary in a way that will yield an isochron. But if the concentration of K does not vary, then one can still get an isochron if the concentration of the non-radiogenic isotope Ar36 of the daughter product varies.

So let's call an isochron a "super-isochron" if the concentration of the parent element varies from one sample to another. Let's call it a "wimpy isochron" otherwise. The question is, what percentage of isochrons are super-isochrons, and how do their dates agree with the conventional dates for their geologic period? I would think that it may be rare to have a super-isochron. If one is dealing with minerals that exclude parent or daughter, then one cannot get an isochron at all.

If one is dealing with minerals that do not exclude parent and daughter elements, then most likely the parent element will be evenly distributed everywhere, and one will have a wimpy isochron that cannot detect added daughter product, and thus may give unreliable ages. Whole rock isochrons may also tend to be wimpy, for the same reason. Even super isochrons can yield ages that are too old, due to mixings, however.

False K-Ar isochrons can be produced if a lava flow starts out with a lot of excess Ar40 which becomes well mixed, along with potassium. Then while cooling or afterwards, a mixture of Ar36 and Ar40 can enter the rock, more in some places than others. Other isotopes of argon would work as well. I believe that this will produce a good K-Ar isochron, but the age calculated will be meaningless. There is another way that false isochrons can be produced.

For a wimpy isochron, say a K-Ar isochron, we can assume that initially there is a uniform concentration of K everywhere, and concentrations of Ar40 and Ar36 that form an isochron. Then a lot of Ar40 enters, uniformly, through cracks in the rock or heating. This will retain the isochron property, but will make the isochron look too old. My reasoning was that if the lava is thoroughly mixed, then the concentration of parent material should be fairly constant.

If the concentration of parent substance is not constant, it could indicate that the lava is not thoroughly mixed. Or it could have other explanations. If the lava is not thoroughly mixed, it is possible to obtain an isochron from the mixing of two different sources, in which case the radiometric age is inherited from the sources, and does not necessarily yield the age of the flow. Someone pointed out to me that many Rb-Sr isochrons are super isochrons. I find this information very interesting, and thank him for it.

I'd be curious to know which strata they occur in, as my main interest is the geologic column of Cambrian and above. My impression is that these are not on this part of the geologic column. And how well do the dates correlate with others for the same formation? There are also mixing scenarios that can produce even super isochrons having invalid ages. And geologists admit in any event that isochrons can sometimes give false ages.

Here is a mixing scenario for false isochrons.

Imsges: earth age radiometric dating

earth age radiometric dating

The rates of exchange that would mess up the dates are very tiny. This section needs additional citations for verification.

earth age radiometric dating

Or it could be that such a distribution of argon pressures in the rocks occurred at some time in the past. Table 8 , however, lists only data obtained before ; since that time, older rocks, from the lunar highlands, have been analyzed. Also, even if the argon-argon dating method does eliminate the "contamination" problem, it does not solve the problem of original argon.

earth age radiometric dating

The human element is also important here. Back to HeliumMagnetic decayMoon dustor Metals in oceans. Isochron dating earth age radiometric dating based on earth age radiometric dating ability to draw a straight line between data points that are thought to have formed at the same time. This meticulous work of many historians should not be ignored. For example, it would be about one in million for rocks in the vicinity of 57 million years old. One isotope, potassium, is radioactive and decays to two different daughter products, calcium and argon, by two different decay methods.