Argon–argon dating is a radiometric dating method invented to supersede potassium-argon (K/Ar) dating in accuracy. . UC Berkeley press release: " Precise dating of the destruction of Pompeii proves argon-argon method can reliably date. For the K/Ar dating system, this decay scheme to calcium isotopes is ignored. argon isotopes are measured, yielding more precise and accurate results. (2) 40K has a half-life of billion years. (3) 40K (parent isotope) breaks down to 40Ar (daughter isotope) by gaining an electron. (4) "Because argon is a gas.
In the field, they look like large raisins in a pudding, and even occur in beds piled one on top of the other, glued together by the lava. The study by Funkhouser and Naughton was on the xenoliths, not on the lava. The xenoliths, which vary in composition and range in size from single mineral grains to rocks the size of basketballs, do indeed carry excess argon in large amounts. Funkhouser and Naughton were quite careful to point out that the apparent "ages" they measured were not geologically meaningful.
Quite simply, xenoliths are one of the types of rocks that cannot be dated by K-Ar techniques. Funkhouser and Naughton were able to determine that the excess gas resides primarily in fluid bubbles in the minerals of the xenoliths, where it cannot escape upon reaching the surface.
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. 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 [Wiens' article] is devoted to explaining how one can tell how much of a given element or isotope was originally present.
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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 [in Wiens' article], and the accompanying explanation, tell how this is done most of the time. There are only a few different 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.
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.
physics - Is K-Ar a reliable method for dating rock ages? - Skeptics Stack Exchange
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 [of Wiens' article]. 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.
Different dating techniques usually give conflicting results. 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, [there are] textbooks, non-classroom books, and web resources. Anomalies As noted above, creationists make great hay out of "anomalies" in radiometric dating.
It is true that some "anomalies" have been observed, although keep in mind that these have been identified by professional scientists in published literature, not by creationists or others outside of peer-reviewed scientific literature.
Argon–argon dating - Wikipedia
First of all, many of these claimed "anomalies" are completely irrelevant to the central issue of whether the Earth is many millions of years old. This is certainly true when errors are in the range of a few percent in specimens many millions of years old.
This is also true of anomalies noted in carbon dates. Carbon dating cannot be used to date anything older than about 50, years, since the carbon half life is only years. For additional discussion, see Radiocarbon dating. In any event, it is important to keep these anomalies in perspective. For example, out of literally tens of thousands of dates measured using the rubidium-strontium dating scheme see description of the Rb-Sr scheme in Agesonly about 30 cases have been noted where the individual data values initially appeared to lie nearly on a straight line as is requiredbut the result was later found to be significantly in error.Radiometric Dating is Flawed!! Really?? How Old IS the Earth?
Instead, the ratios of the different argon isotopes are measured, yielding more precise and accurate results. The amount of 39ArK produced in any given irradiation will be dependant on the amount of 39K present initially, the length of the irradiation, the neutron flux density and the neutron capture cross section for 39K. However, because each of these parameters is difficult to determine independantly, a mineral standard, or monitor, of known age is irradiated with the samples of unknown age.
The monitor flux can then be extrapolated to the samples, thereby determining their flux. This flux is known as the 'J' and can be determined by the following equation: In addition to 39Ar production from 39K, several other 'interference' reactions occur during irradiation of the samples.
Other isotopes of argon are produced from potassium, calcium, argon and chlorine. As the table above illustrates, several "undesirable" reactions occur on isotopes present within every geologic sample.
These reactor produced isotopes of argon must be corrected for in order to determine an accurate age. The monitoring of the interfering reactions is performed through the use of laboratory salts and glasses.
For example, to determine the amount of reactor produced 40Ar from 40K, potassium-rich glass is irradiated with the samples. The desirable production of 38Ar from 37Cl allows us to determine how much chlorine is present in our samples. Multiple argon extractions can be performed on a sample in several ways.
Step-heating is the most common way and involves either a furnace or a laser to uniformily heat the sample to evolve argon. The individual ages from each heating step are then graphically plotted on an age spectrum or an isochron.
Mechanical crushing is also a technique capable of releasing argon from a single sample in multiple steps.