Quick radiometric dating question- misused techniques

Just a quick question, as I've not been able to find out in anything I've read so far. I know that using the wrong radiometric dating methods brings back wrong results, e.g. using K-Ar on some lava that is practically still warm is useless.My question is- If I were to date a series of much too young or much too old lavas with K-Ar dating, even though it could not possibly tell me the age of the lava, what kinds of numbers would I get? I'm particularly interested to know if the technique would still be able to tell oldest from youngest, or if the numbers would be fairly random? Would the same apply to other radiometric techniques?

Thread moved here from the Proposed New Topics forum.

Not an expert, and I am talking off the topic of my head.I think that K/Ar dating is suitable for dating the Earth's oldest rocks. At least those that had high enough K content to begin with. Dating low K rocks is a another mater.The catch it, K/Ar is particularly subject to reseting by more recent thermal events - Metamorphism. As such, the date you would get would be the date of metamorphism, not the origin date of the igneous rock. It's possible to date the same rock using different methodology, and to then get different dates. But they may well be different because you are dating different events in the rocks history.Enough from me. Better listen to the real experts around here.Moose

We discussed this in the A Guide to Creationist Tactics. The thing is that as you reach the bounds of a method you get the bounds as a returned value and that is about it. Hope this helps.

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Anyone so limited that they can only spell a word one way is severely handicapped!

As Jar just pointed out, applying any analytical method to an analysis that is outside of its area of usefulness is just downright silly.It would be a little like taking an instrument that cannot see less than 1 part per thousand of mercury in water (due to instrumental design limitations or background system noise or whatever reason) then measuring drinking water with it.The result can never be less than the minimum background reading of 1 part per thousand so it wouldn't make much sense to then complain that the drinking water doesn't meet environmental guidelines and closing the reservoir.The correct thing to do would be to report less than LOD (Limit Of detection) and that is exactly what all of the labs that I work with (including my own) do.Then you go try again with a method that does work Edited by PurpleYouko, : No reason given.

Thanks for the input guys

So let's say I'm a YEC and I'm mightily impressed by Steve Austin's erroneous dates for the Mount St. Helens lava. While evolutionists are metaphorically talking about how you can't measure sand grains with rulers, I'm thinking that Austin has done something clever. Here's what would be going through my head:You have a rock sample whose age you know nothing about. (I know that scientists understand rock-forming processes and they also will have recorded where in the geologic column the rock came from, but we're talking about a YEC here who thinks scientists are lying imbeciles.) How do you pick which dating method to use? If you use K-Ar like Austin did, you will get a date that says it's millions of years old. If it's very young rock, then you are very very wrong. That is what Austin showed.So my own question is, let's say with a blind sample,a.) How would you guess which radiometric method to try first?
b.) How do you know if the dates you've got are erroneous? (Besides the obvious fact that you'd date more than one sample by different methods to see if the dates correlate.)Thanks.Edited by LindaLou, : No reason given.

Hey, you talkin' 'bout me?? I haven't been a good boy and looked into what was said but I think you statement above is not precisely enough worded to be correct in this particular context. What the K-Ar method will show is that a young rock is no older than the minimum date it can measure. This is, again in this context, very different than saying it is as old as the minimum date that K-Ar is good for.This is just like the inverted case of using C14 for very old materials. The date returned means that the material is at least as old as the maximum reasonable date for C14 dating methods.ABE
Once you have the results saying that the rock is no older than the K-AR minimum date then you know you need another method to narrow it down. So it doesn't matter where you start you'll end up with the right answer. You'll just waste time and money going the longer way around.Edited by NosyNed, : No reason given.

Thanks Nosy, that's clear now. But I'm still wondering what this data looks like that says that your sample is no older than the minimum age the method measures. Is it plotted on a graph? Does the machine spit out a piece of paper saying "fail"? Or is it simply a matter of observing that you have received the minimum date for your chosen method and therefore you need to try a method more suitable for a younger sample? Just curious; I will probably need to explain this in my own words at some point.Edited by LindaLou, : No reason given.

In radiocarbon dating the point at which the sample's signal is lost amid the background signal marks the upper limit.This is somewhat dependent on equipment, shielding, etc., but for most laboratories the limit is currently not much over 50,000 years. With older equipment in past decades it could be in the 35,000-40,000 range.Experimental results are occasionally being obtained back more toward 80,000 years using the AMS (Accelerator Mass Spectroscopy) method, but those ranges are not ready for prime time.

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Religious belief does not constitute scientific evidence, nor does it convey scientific knowledge.

someone who actually knows what he is talking about.I have never done or seen done or even read about the details of the procedures. I made the whole thing up but it is what is true about the methods until someone who knows says otherwise .

You might know the most minute of details for C14 dating at least:If the sample's signal is lost in the background how is that reported?In the context of this discussion there is an important difference between: The sample is 50,000 years old and the sample is at least 50,000 years old.Do you have actual reports?

I've submitted nearly 600 samples, and well as lectured on the subject and done one monograph. This is on the archaeological end, not the intimate details of the processing. When a sample returns a measured age you get a figure such as 10,000100. If the C13 is measured as well you will get the conventional age (corrected for C13), and that is expressed in the same way.If the sample is old enough to be lost in the background radiation it would be expressed as >50,000 (for example). Here is a link to a blog showing how creationists missed the ">" sign (probably from not knowing what it meant) and used the resulting dates on natural gas to "prove" a young earth, when in fact they were expressing the limits of the equipment being used:http://blog.darwincentral.org/...e%E2%80%9D-%E2%80%94-part-vThis link has references to an article in Radiocarbon. (I assume this is what you mean by "actual reports."

For the specific case of K-Ar, the method is known to give erroneous dates if the lava cooled too quickly. The 39Ar-40Ar method was invented to correct for this, and has been shown to be much more accurate and reliable. K-Ar dates are much less expensive, but should be taken with a grain of salt until they are verified by 39Ar-40Ar or other means.Isotopic dating is subject to many variables and pitfalls. The more that is known about a sample, the better it can be prepared and dated. Thus, blind samples are generally frowned upon, and some labs will refuse to accept them.

LindaLou, in message 9, was considering datings using such methods as K/Ar, Rb/Sr, and U/Pb. For such long lived isotopes there is or can be a minimum possible datable age.You responded to her and jumped to C14 dating, where there is a maximum possible datable age.You were not responding to the subtheme that LindaLou was discussing.Minnemooseus (w/ Adminnemooseus looking over shoulder)