Geologists use radiometric dating to estimate how long ago rocks formed, and to infer the ages of fossils contained within those rocks. Radioactive elements decay The universe is full of naturally occurring radioactive elements. Radioactive atoms are inherently unstable; over time, radioactive "parent atoms" decay into stable "daughter atoms. When molten rock cools, forming what are called igneous rocks, radioactive atoms are trapped inside. Afterwards, they decay at a predictable rate.
This relies on a proven combination of basic mathematics and knowledge of the physical properties of different chemical elements.
To understand radiometric dating techniquesyou first have to have an understanding of what is being measured, how the measurement is being made and the theoretical as well as practical limitations of the system of measurement being used. As an analogy, say you find yourself wondering, "How warm or cold is it outside? You need a device to measure this activity a thermometer, of which various kinds exist.
You also need to know when you can or cannot apply a particular type of device to the task at hand; for example, if you want to know how hot it is on the inside of an active wood stove, you probably understand that putting a household thermometer intended to measure body temperature inside the stove is not going to prove helpful. Be aware also that for many centuries, most human "knowledge" of the age of rocks, formations such as the Grand Canyon, and everything else around you was predicated on the Genesis account of the Bible, which posits that the entire cosmos is perhaps 10, years old.
Modern geological methods have at times proven thorny in the face of such popular but quaint and scientifically unsupported notions. Radiometric dating takes advantage of the fact that the composition of certain minerals rocks, fossils and other highly durable objects changes over time.
Specifically, the relative amounts of their constituent elements shift in a mathematically predictable way thanks to a phenomenon called radioactive decay. This in turn relies on knowledge of isotopessome of which are "radioactive" that is, they spontaneously emit subatomic particles at a known rate. Isotopes are different versions of the same element e. Some things in nature disappear at a more or less constant rate, regardless of how much there is to start with and how much remains.
Apologise, but, scientists radiometric dating apologise
For example, certain drugs, including ethyl alcohol, are metabolized by the body at a fixed number of grams per hour or whatever units are most convenient. If someone has the equivalent of five drinks in his system, the body takes five times as long to clear the alcohol as it would if he had one drink in his system. Many substances, however, both biological and chemical, conform to a different mechanism: In a given time period, half of the substance will disappear in a fixed time no matter how much is present to start with.
Such substances are said to have a half-life. Radioactive isotopes obey this principle, and they have wildly different decay rates. The utility of this lies in being able to calculate with ease how much of a given element was present at the time it was formed based on how much is present at the time of measurement. This is because when radioactive elements first come into being, they are presumed to consist entirely of a single isotope. As radioactive decay occurs over time, more and more of this most common isotope "decays" i.
Imagine that you enjoy a certain kind of ice cream flavored with chocolate chips. You have a sneaky, but not especially clever, roommate who doesn't like the ice cream itself, but cannot resist picking out eating the chips - and in an effort to avoid detection, he replaces each one he consumes with a raisin.
He is afraid to do this with all of the chocolate chips, so instead, each day, he swipes half of the number of remaining chocolate chips and puts raisins in their place, never quite completing his diabolical transformation of your dessert, but getting closer and closer. Say a second friend who is aware of this arrangement visits and notices that your carton of ice cream contains 70 raisins and 10 chocolate chips.
She declares, "I guess you went shopping about three days ago. Because your roommate eats half of the chips on any given day, and not a fixed number, the carton must have held 20 chips the day before, 40 the day before that, and 80 the day before that.
The bigger c1 is, the older the rock is. That is, the more daughter product relative to parent product, the greater the age.
Thus we have the same general situation as with simiple parent-to-daughter computations, more daughter product implies an older age. This is a very clever idea. However, there are some problems with it.
First, in order to have a meaningful isochron, it is necessary to have an unusual chain of events. Initially, one has to have a uniform ratio of lead isotopes in the magma. Usually the concentration of uranium and thorium varies in different places in rock. This will, over the assumed millions of years, produce uneven concentrations of lead isotopes. To even this out, one has to have a thorough mixing of the magma.
Even this is problematical, unless the magma is very hot, and no external material enters. Now, after the magma is thoroughly mixed, the uranium and thorium will also be thoroughly mixed. What has to happen next to get an isochron is that the uranium or thorium has to concentrate relative to the lead isotopes, more in some places than others.
So this implies some kind of chemical fractionation. Then the system has to remain closed for a long time. This chemical fractionation will most likely arise by some minerals incorporating more or less uranium or thorium relative to lead.
Anyway, to me it seems unlikely that this chain of events would occur. Another problem with isochrons is that they can occur by mixing and other processes that result in isochrons yielding meaningless ages. Sometimes, according to Faure, what seems to be an isochron is actually a mixing line, a leftover from differentiation in the magma.
Fractionation followed by mixing can create isochrons giving too old ages, without any fractionation of daughter isotopes taking place. To get an isochron with a false age, all you need is 1 too much daughter element, due to some kind of fractionation and 2 mixing of this with something else that fractionated differently. Since fractionation and mixing are so common, we should expect to find isochrons often.
How they correlate with the expected ages of their geologic period is an interesting question. There are at least some outstanding anomalies. Faure states that chemical fractionation produces "fictitious isochrons whose slopes have no time significance.
As an example, he uses Pliocene to Recent lava flows and from lava flows in historical times to illustrate the problem. He says, these flows should have slopes approaching zero less than 1 million yearsbut they instead appear to be much older million years.
Scientists radiometric dating
Steve Austin has found lava rocks on the Uinkeret Plateau at Grand Canyon with fictitious isochrons dating at 1. Then a mixing of A and B will have the same fixed concentration of N everywhere, but the amount of D will be proportional to the amount of P. This produces an isochron yielding the same age as sample A.
This is a reasonable scenario, since N is a non-radiogenic isotope not produced by decay such as lea and it can be assumed to have similar concentrations in many magmas.
Magma from the ocean floor has little U and little U and probably little lead byproducts lead and lead Magma from melted continental material probably has more of both U and U and lead and lead Thus we can get an isochron by mixing, that has the age of the younger-looking continental crust. The age will not even depend on how much crust is incorporated, as long as it is non-zero. However, if the crust is enriched in lead or impoverished in uranium before the mixing, then the age of the isochron will be increased.
If the reverse happens before mixing, the age of the isochron will be decreased. Any process that enriches or impoverishes part of the magma in lead or uranium before such a mixing will have a similar effect. So all of the scenarios given before can also yield spurious isochrons. I hope that this discussion will dispel the idea that there is something magical about isochrons that prevents spurious dates from being obtained by enrichment or depletion of parent or daughter elements as one would expect by common sense reasoning.
So all the mechanisms mentioned earlier are capable of producing isochrons with ages that are too old, or that decrease rapidly with time. The conclusion is the same, radiometric dating is in trouble. I now describe this mixing in more detail.
Suppose P p is the concentration of parent at a point p in a rock.
Was and scientists radiometric dating congratulate, simply magnificent
The point p specifies x,y, and z co-ordinates. Let D p be the concentration of daughter at the point p. Let N p be the concentration of some non-radiogenic not generated by radioactive decay isotope of D at point p. Suppose this rock is obtained by mixing of two other rocks, A and B.
Suppose that A has a for the sake of argument, uniform concentration of P1 of parent, D1 of daughter, and N1 of non-radiogenic isotope of the daughter. Thus P1, D1, and N1 are numbers between 0 and 1 whose sum adds to less than 1. Suppose B has concentrations P2, D2, and N2.
Let r p be the fraction of A at any given point p in the mixture. So the usual methods for augmenting and depleting parent and daughter substances still work to influence the age of this isochron. More daughter product means an older age, and less daughter product relative to parent means a younger age.
In fact, more is true. Any isochron whatever with a positive age and a constant concentration of N can be constructed by such a mixing. It is only necessary to choose r p and P1, N1, and N2 so as to make P p and D p agree with the observed values, and there is enough freedom to do this.
Anyway, to sum up, there are many processes that can produce a rock or magma A having a spurious parent-to-daughter ratio. Then from mixing, one can produce an isochron having a spurious age. This shows that computed radiometric ages, even isochrons, do not have any necessary relation to true geologic ages. Mixing can produce isochrons giving false ages. But anyway, let's suppose we only consider isochrons for which mixing cannot be detected.
How do their ages agree with the assumed ages of their geologic periods? As far as I know, it's anyone's guess, but I'd appreciate more information on this. I believe that the same considerations apply to concordia and discordia, but am not as familiar with them.
It's interesting that isochrons depend on chemical fractionation for their validity. They assume that initially the magma was well mixed to assure an even concentration of lead isotopes, but that uranium or thorium were unevenly distributed initially. So this assumes at the start that chemical fractionation is operating. But these same chemical fractionation processes call radiometric dating into question.
The relative concentrations of lead isotopes are measured in the vicinity of a rock. The amount of radiogenic lead is measured by seeing how the lead in the rock differs in isotope composition from the lead around the rock.
This is actually a good argument. But, is this test always done? How often is it done? And what does one mean by the vicinity of the rock? How big is a vicinity? One could say that some of the radiogenic lead has diffused into neighboring rocks, too. Some of the neighboring rocks may have uranium and thorium as well although this can be factored in in an isochron-type manner. Furthermore, I believe that mixing can also invalidate this test, since it is essentially an isochron.
Finally, if one only considers U-Pb and Th-Pb dates for which this test is done, and for which mixing cannot be detected. The above two-source mixing scenario is limited, because it can only produce isochrons having a fixed concentration of N p. To produce isochrons having a variable N pa mixing of three sources would suffice.
This could produce an arbitrary isochron, so this mixing could not be detected. Also, it seems unrealistic to say that a geologist would discard any isochron with a constant value of N pas it seems to be a very natural condition at least for whole rock isochronsand not necessarily to indicate mixing. I now show that the mixing of three sources can produce an isochron that could not be detected by the mixing test. First let me note that there is a lot more going on than just mixing.
There can also be fractionation that might treat the parent and daughter products identically, and thus preserve the isochron, while changing the concentrations so as to cause the mixing test to fail. It is not even necessary for the fractionation to treat parent and daughter equally, as long as it has the same preference for one over the other in all minerals examined; this will also preserve the isochron. Now, suppose we have an arbitrary isochron with concentrations of parent, daughter, and non-radiogenic isotope of the daughter as P pD pand N p at point p.
Suppose that the rock is then diluted with another source which does not contain any of D, P, or N. Then these concentrations would be reduced by a factor of say r' p at point p, and so the new concentrations would be P p r' pD p r' pand N p r' p at point p.
Now, earlier I stated that an arbitrary isochron with a fixed concentration of N p could be obtained by mixing of two sources, both having a fixed concentration of N p. With mixing from a third source as indicated above, we obtain an isochron with a variable concentration of N pand in fact an arbitrary isochron can be obtained in this manner. So we see that it is actually not much harder to get an isochron yielding a given age than it is to get a single rock yielding a given age.
This can happen by mixing scenarios as indicated above. Thus all of our scenarios for producing spurious parent-to-daughter ratios can be extended to yield spurious isochrons. The condition that one of the sources have no P, D, or N is fairly natural, I think, because of the various fractionations that can produce very different kinds of magma, and because of crustal materials of various kinds melting and entering the magma. In fact, considering all of the processes going on in magma, it would seem that such mixing processes and pseudo-isochrons would be guaranteed to occur.
Even if one of the sources has only tiny amounts of P, D, and N, it would still produce a reasonably good isochron as indicated above, and this isochron could not be detected by the mixing test. I now give a more natural three-source mixing scenario that can produce an arbitrary isochron, which could not be detected by a mixing test.
P2 and P3 are small, since some rocks will have little parent substance. Suppose also that N2 and N3 differ significantly. Such mixings can produce arbitrary isochrons, so these cannot be detected by any mixing test. Also, if P1 is reduced by fractionation prior to mixing, this will make the age larger. If P1 is increased, it will make the age smaller. If P1 is not changed, the age will at least have geological significance. But it could be measuring the apparent age of the ocean floor or crustal material rather than the time of the lava flow.
I believe that the above shows the 3 source mixing to be natural and likely. We now show in more detail that we can get an arbitrary isochron by a mixing of three sources. Thus such mixings cannot be detected by a mixing test. Assume D3, P3, and N3 in source 3, all zero. One can get this mixing to work with smaller concentrations, too.
All the rest of the mixing comes from source 3.
For many people, radiometric dating might be the one scientific technique that most blatantly seems to challenge the Bible's record of recent creation. For this reason, ICR research has long focused on the science behind these dating techniques. Oct 27, We are told that scientists use a technique called radiometric dating to measure the age of rocks. We are also told that this method very reliably and consistently yields ages of millions to billions of years, thereby establishing beyond question that the earth is . Radiometric dating Geologists use radiometric dating to estimate how long ago rocks formed, and to infer the ages of fossils contained within those rocks.
Thus we produce the desired isochron. So this is a valid mixing, and we are done. We can get more realistic mixings of three sources with the same result by choosing the sources to be linear combinations of sources 1, 2, and 3 above, with more natural concentrations of D, P, and N. The rest of the mixing comes from source 3. This mixing is more realistic because P1, N1, D2, and N2 are not so large. I did see in one reference the statement that some parent-to-daughter ratio yielded more accurate dates than isochrons.
To me, this suggests the possibility that geologists themselves recognize the problems with isochrons, and are looking for a better method. The impression I have is that geologists are continually looking for new methods, hoping to find something that will avoid problems with existing methods. But then problems also arise with the new methods, and so the search goes on. Furthermore, here is a brief excerpt from a recent article which also indicates that isochrons often have severe problems.
If all of these isochrons indicated mixing, one would think that this would have been mentioned: The geological literature is filled with references to Rb-Sr isochron ages that are questionable, and even impossible. Woodmorappepp. Faurepp.
Zhengpp. Zheng pp. He comes closest to recognizing the fact that the Sr concentration is a third or confounding variable in the isochron simple linear regression. Snelling discusses numerous false ages in the U-Pb system where isochrons are also used. However, the U-Th-Pb method uses a different procedure that I have not examined and for which I have no data.
Many of the above authors attempt to explain these "fictitious" ages by resorting to the mixing of several sources of magma containing different amounts of Rb, Sr, and Sr immediately before the formation hardens.
AkridgeArmstrongArndtsBrown, Helmick and Baumann all discuss this factor in detail. Anyway, if isochrons producing meaningless ages can be produced by mixing, and this mixing cannot be detected if three or maybe even two, with fractionation sources are involved, and if mixing frequently occurs, and if simple parent-to-daughter dating also has severe problems, as mentioned earlier, then I would conclude that the reliability of radiometric dating is open to serious question.
The many acknowledged anomalies in radiometric dating only add weight to this argument. I would also mention that there are some parent-to-daughter ratios and some isochrons that yield ages in the thousands of years for the geologic column, as one would expect if it is in fact very young.
One might question why we do not have more isochrons with negative slopes if so many isochrons were caused by mixing. This depends on the nature of the samples that mix. It is not necessarily true that one will get the same number of negative as positive slopes. If I have a rock X with lots of uranium and lead daughter isotope, and rock Y with less of both relative to non-radiogenic lea then one will get an isochron with a positive slope.
If rock X has lots of uranium and little daughter product, and rock Y has little uranium and lots of lead daughter product relative to non-radiogenic lea then one will get a negative slope. This last case may be very rare because of the relative concentrations of uranium and lead in crustal material and subducted oceanic plates.
Another interesting fact is that isochrons can be inherited from magma into minerals. Earlier, I indicated how crystals can have defects or imperfections in which small amounts of magma can be trapped. This can result in dates being inherited from magma into minerals. This can also result in isochrons being inherited in the same way. So the isochron can be measuring an older age than the time at which the magma solidified. This can happen also if the magma is not thoroughly mixed when it erupts.
If this happens, the isochron can be measuring an age older than the date of the eruption. This is how geologists explain away the old isochron at the top of the Grand Canyon. From my reading, isochrons are generally not done, as they are expensive. Isochrons require more measurements than single parent-to-daughter ratios, so most dates are based on parent-to-daughter ratios.
Opinion scientists radiometric dating remarkable, rather amusing
So all of the scenarios given apply to this large class of dates. Another thing to keep in mind is that it is not always possible to do an isochron.
Often one does not get a straight line for the values. The carbon half-life is only years. Cesium has a half-life of 30 years, and oxygen has a half-life of only The answer has to do with the exponential nature of radioactive decay.
The rate at which a radioactive substance decays in terms of the number of atoms per second that decay is proportional to the amount of substance. So after one half-life, half of the substance will remain. After another half-life, one fourth of the original substance will remain. Another half-life reduces the amount to one-eighth, then one-sixteenth and so on.
The substance never quite vanishes completely, until we get down to one atom, which decays after a random time. Since the rate at which various radioactive substances decay has been measured and is well known for many substances, it is tempting to use the amounts of these substances as a proxy for the age of a volcanic rock.
So, if you happened to find a rock with 1 microgram of potassium and a small amount of argon, would you conclude that the rock is 1. If so, what assumptions have you made? In the previous hypothetical example, one assumption is that all the argon was produced from the radioactive decay of potassium But is this really known?
How do you know for certain that the rock was not made last Thursday, already containing significant amounts of argon and with only 1 microgram of potassium? In a laboratory, it is possible to make a rock with virtually any composition. Ultimately, we cannot know.
Generally, we are told that scientists have ways to analyze the object they are dating so as to eliminate the uncertainties due to unknown processes that occurred in the past. One way this is done in many radioactive dating techniques is to use an isochron. Most scientists today believe that life has existed on the earth for billions of years. This belief in long ages for the earth and the existence of life is derived largely from radiometric dating. These long time periods are computed by measuring the ratio of daughter to. Jan 23, Radiometric dating measures the decay of radioactive atoms to determine the age of a rock sample. It is founded on unorthamericanjunioramateur.comovable assumptions such as 1) there has been no contamination and 2) the decay rate has remained constant.
But there is a seemingly good reason to think that virtually all the argon contained within a rock is indeed the product of radioactive decay.
Volcanic rocks are formed when the lava or magma cools and hardens. But argon is a gas. Since lava is a liquid, any argon gas should easily flow upward through it and escape. Thus, when the rock first forms, it should have virtually no argon gas within it. But as potassium decays, the argon content will increase, and presumably remain trapped inside the now-solid rock.
So, by comparing the argon to potassium ratio in a volcanic rock, we should be able to estimate the time since the rock formed. This is called a model-age method. In this type of method, we have good theoretical reasons to assume at least one of the initial conditions of the rock. The initial amount of argon when the rock has first hardened should be close to zero. Yet we know that this assumption is not always true. We know this because we have tested the potassium-argon method on recent rocks whose age is historically known.
That is, brand new rocks that formed from recent volcanic eruptions such as Mt. Helens have been age-dated using the potassium-argon method. Their estimated ages were reported as hundreds of thousands of years based on the argon content, even though the true age was less than 10 years.
Since the method has been shown to fail on rocks whose age is known, would it make sense to trust the method on rocks of unknown age? But many secular scientists continue to trust the potassium-argon model-age method on rocks of unknown age. If so, then their true ages are much less than their radiometric age estimates. The age estimate could be wrong by a factor of hundreds of thousands.
Amusing topic scientists radiometric dating agree
But how would you know? We must also note that rocks are not completely solid, but porous. And gas can indeed move through rocks, albeit rather slowly. So the assumption that all the produced argon will remain trapped in the rock is almost certainly wrong. And it is also possible for argon to diffuse into the rock of course, depending on the relative concentration. So the system is not as closed as secularists would like to think. There are some mathematical methods by which scientists attempt to estimate the initial quantity of elements in a rock, so that they can compensate for elements like argon that might have been present when the rock first formed.
Such techniques are called isochron methods. They are mathematically clever, and we may explore them in a future article. However, like the model-age method, they are known to give incorrect answers when applied to rocks of known age. And neither the model-age method nor the isochron method are able to assess the assumption that the decay rate is uniform. As we will see below, this assumption is very dubious. Years ago, a group of creation scientists set out to explore the question of why radiometric dating methods give inflated age estimates.
We know they do because of the aforementioned tests on rocks whose origins were observed. But why? Which of the three main assumptions initial conditions are known, rate of decay is known, the system is close is false? To answer this question, several creation geologists and physicists came together to form the RATE research initiative R adioisotopes and the A ge of T he E arth.
This multi-year research project engaged in several different avenues of study, and found some fascinating results. As mentioned above, the isochron method uses some mathematical techniques in an attempt to estimate the initial conditions and assess the closed-ness of the system. However, neither it nor the model-age method allow for the possibility that radioactive decay might have occurred at a different rate in the past.
In other words, all radiometric dating methods assume that the half-life of any given radioactive element has always been the same as it is today. If that assumption is false, then all radiometric age estimates will be unreliable. As it turns out, there is compelling evidence that the half-lives of certain slow-decaying radioactive elements were much smaller in the past.
Science Confirms a Young Earth—The Radioactive Dating Methods are Flawed
This may be the main reason why radiometric dating often gives vastly inflated age estimates. First, a bit of background information is in order. Most physicists had assumed that radioactive half-lives have always been what they are today.
Many experiments have confirmed that most forms of radioactive decay are independent of temperature, pressure, external environment, etc. In other words, the half-life of carbon is years, and there is nothing you can do to change it. Given the impossibility of altering these half-lives in a laboratory, it made sense for scientists to assume that such half-lives have always been the same throughout earth history.
But we now know that this is wrong. In fact, it is very wrong. More recently, scientists have been able to change the half-lives of some forms of radioactive decay in a laboratory by drastic amounts. However, by ionizing the Rhenium removing all its electronsscientists were able to reduce the half-life to only 33 years!
For most scientists the standard geological timescale, with its millions and billions of years, and radioisotope dating are almost synonymous. From Vardiman et al. Carbon dating is used to determine the age of biological artifacts up to 50, years old. This technique is widely used on recent artifacts, but educators and students alike should. Radiometric dating is a means of determining the age of very old objects, including the Earth itself. Radiometric dating depends on the decay of isotopes, which are different forms of the same element that include the same number of protons but different numbers of neutrons in their atoms. If you believe radiometric dating mean? Geologist ralph harvey and counting of scientists accept radiometric dating is potholer refuting carbon 14 and analyzed with sedimentary rocks that pervades academia today. In certain assumptions are three main types of carbon dating in order for a rock. Wiki user june 16, certain rocks.
In other words, the Rhenium decays over 1 billion times faster under such conditions. Thus, any age estimates based on Rhenium-Osmium decay may be vastly inflated.
The RATE research initiative found compelling evidence that other radioactive elements also had much shorter half-lives in the past. Several lines of evidence suggest this. But for brevity and clarity, I will mention only one. This involves the decay of uranium into lead Unlike the potassium-argon decay, the uranium-lead decay is not a one-step process.
Rather, it is a step process. Uranium decays into thorium, which is also radioactive and decays into polonium, which decays into uranium, and so on, eventually resulting in lead, which is stable. Eight of these fourteen decays release an alpha-particle: the nucleus of a helium atom which consists of two protons and two neutrons.
The helium nucleus quickly attracts a couple of electrons from the environment to become a neutral helium atom.