Problems with radiometric dating techniques

Scientist Realizes Important Flaw in Radioactive Dating

This is an enormous branch of geochemistry called Geochronology. There are many radiometric clocks and when applied to appropriate materials, the dating can be very accurate. As one example, the first minerals to crystallize condense from the hot cloud of gasses that surrounded the Sun as it first became a star have been dated to plus or minus 2 million years!! That is pretty accurate!!! Other events on earth can be dated equally well given the right minerals.

For example, a problem I have worked on involving the eruption of a volcano at what is now Naples, Italy, occurred years ago with a plus or minus of years. Yes, radiometric dating is a very accurate way to date the Earth.


We know it is accurate because radiometric dating is based on the radioactive decay of unstable isotopes. For example, the element Uranium exists as one of several isotopes, some of which are unstable. When an unstable Uranium U isotope decays, it turns into an isotope of the element Lead Pb. We call the original, unstable isotope Uranium the "parent", and the product of decay Lead the "daughter". From careful physics and chemistry experiments, we know that parents turn into daughters at a very consistent, predictable rate.

A geologist can pick up a rock from a mountainside somewhere, and bring it back to the lab, and separate out the individual minerals that compose the rock. They can then look at a single mineral, and using an instrument called a mass spectrometer, they can measure the amount of parent and the amount of daughter in that mineral. The ratio of the parent to daughter then can be used to back-calculate the age of that rock.

The reason we know that radiometric dating works so well is because we can use several different isotope systems for example, Uranium-Lead, Lutetium-Halfnium, Potassium-Argon on the same rock, and they all come up with the same age. This gives geologists great confidence that the method correctly determines when that rock formed.

Hope that helps, and please ask if you'd like more details! I think that I will start by answering the second part of your question, just because I think that will make the answer to the first question clearer. Radiometric dating is the use of radioactive and radiogenic those formed from the decay of radioactive parents isotopes isotopes are atoms of the same element that have different numbers of neutrons in their nuclei to determine the age of something.

It is commonly used in earth science to determine the age of rock formations or features or to figure out how fast geologic processes take place for example, how fast marine terraces on Santa Cruz island are being uplifted.

Radiometric dating relies on the principle of radioactive decay. All radioactive isotopes have a characteristic half-life the amount of time that it takes for one half of the original number of atoms of that isotope to decay. By measuring the parent isotope radioactive and the daughter isotope radiogenic in a system for example, a rock , we can tell how long the system has been closed in our example, when the rock formed. The process of radiogenic dating is usually done using some sort of mass spectrometer.

A mass spectrometer is an instrument that separates atoms based on their mass. Because geochronologists want to measure isotopes with different masses, a mass spectrometer works really well for dating things. I do think that radiometric dating is an accurate way to date the earth, although I am a geochronologist so I have my biases.

Most estimates of the age of the earth come from dating meteorites that have fallen to Earth because we think that they formed in our solar nebula very close to the time that the earth formed. The fact that the age we calculate is reproducible for these different systems is significant.

We have also obtained a very similar age by measuring Pb isotopes in materials from earth.

Radiometric dating

I should mention that the decay constants basically a value that indicates how fast a certain radioactive isotope will decay for some of these isotope systems were calculated by assuming that the age of the earth is 4. The decay constants for most of these systems have been confirmed in other ways, adding strength to our argument for the age of the earth. Radiometric dating depends on the chemistry and ratios of different elements. It works like this:. Take, for example, zircon, which is a mineral; its chemical formula is ZiSiO 4 , so there is one zirconium Zi for one silicon Si for four oxygen O.

One of the elements that can stand in chemically for zircon is uranium. What is more alarming is that the Google searches for "carbon 14 RATE", "carbon 14 diamond", and "carbon 14 coal" yield hits predominantly in woowoo fundamentalist sites, and no hits on the first 15 pages 10 links per page to anything at talkorigins.

I eventually managed to find an excellent article see the top of this post using pandasthumb. That led me to this non-technical article,. I think the news item on their front page refers to a much older event. What happened, from what I recall, is that someone hacked TalkOrigins and managed to get the site to display hidden spam links at the bottom of pages, making Google think it was a spam site and thus getting it removed from Google. They fixed that issue a while ago. PZ Myers says they've had some technical issues.

I am working my way through Kirk Bertsche's 9 page essay on the subject. Thanks DH for this link. This article does a good job at explaining the technical complexities of measuring the very small amounts of C14 present in these ancient samples and why non-zero amounts are measured. I'm a complete non-expert in this field of radiometric dating, but it strikes me reading this how contamination by modern carbon introduced during sample preparation seems to be a severe issue.

I'm wonder whether they've extracted samples under an inert atmosphere and then used laser ablation to ionize samples in their mass spectrometers? I'm probably teaching grandmother to suck eggs, as the old saying goes. Getting back to my OP - I feel that some definitive work needs to be done in this area. It's easy to see that the sceptical creationist is simply going to see the scientific response as making excuses for the data instead of holding up some hard data that either explains or explodes the anomaly. Another thing I've heard from creationists is that fossils made by soaking samples in tar pits appear to be extremely old.

Of course, the problem is that this process results in contamination with old carbon, making the sample appear older. In the case of old samples with almost no C, even the tiniest bit of contamination would make the sample appear far younger. Always remember that C dating is not a magical process; it is a measure of C and the age interpretation depends on a few assumptions.

How reliable is geologic dating?

It's also worth noting that C is only useful for a bit more than , years. The vast majority of fossils aren't dated using C at all, but other radioisotopes. Science has several very reasonable explanations for levels of modern carbon in very old samples. Although this satisfies the scientist, who for all sorts of other reasons quite reasonably assumes that these samples are truly old, it leaves enormous scope for the creationists to reinforce their followers' faith that the earth is young.

I still feel that some definitive experiments in this area would be useful to test the various rational explanations for the c14 anomaly. I can see though that science has problems taking on creationists because of the perceived risk of lending credibility to their ideas. Bit of a dilemma there.

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Also as soon as one creationist idea is exploded, they just move on to another area where uncertainty in the science offers them the opportunity to mislead. That begs the question that an anomaly even exists. What does exist are limits to the applicability of 14 C dating techniques. Several of the test results touted by creationists were definitive experiments to assess those limitations. There is no arguing with young earth creationists.

They are immune to logic and evidence. Broadly speaking I agree with you. But, reading the experts' explanations of the "anomaly" read to me, as a non-expert in this field, like perfectly reasonable explanations as long as you accept the "old earth" explanation. If you don't, such dismissive arguments as 'the extra C14 could be due to uranium decay' leave enough wriggle room uncertainty for the creationist to thrive in.

You're right though, I'm probably being naive in thnking they will be convinced. Even so, it is always good when creationists have been casting doubt in some area to be able to completely explode their reasoning. I'm still looking for a reference, in a refereed scientific journal, confirming the finding of carbon14, in any amount, in diamonds or coal. I suspect, but haven't been able to confirm, that the reports of carbon 14 in these substances have been made up out of whole cloth by Young Earth Creationists, but I am loath to make this claim, absent evidence that reports of these findings haven't been published in any journals that aren't connected with such organizations as the Institute for Creation Science.

I further think that it is the fact that the claims are conscpicuously bogus that has accounted for their not having been responded to. After all, to my limited understanding, carbon 14 is associated with organic processes, and, right off the bat, I find myself wondering why it would be found in any allotrope of carbon, which is an inorganic element.

Can anyone out there either confirm or disconfirm my suspicions? You need to know that I will not be much impressed by anything coming from the ICR or any similar group. Well one of two things could be happening, the carbon 14 signature is reset every time the rock melts because the carbon 14 disperses among the liquid rock, Also neutron bombardment from uranium decay could possibly have an impact, but you'd also have other trace elements that tell the tale of this neutron contamination. Since the discussion is specifically about Carbon14 in coal I am unclear as to why you would be talking about molten rock.

Creation v. Evolution: How Carbon Dating Works

Coal is not known for its inclination to melt. Since Carbon14 dating is only relevant to dating organic matter I am unclear as to why you would be talking about resetting the Carbon14 clock in molten rock. Molten rock is not organic material friendly. We all make mistakes. I made one in You need to be a member in order to leave a comment. Sign up for a new account in our community.

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