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By using our site, you acknowledge that you have read and understand our Cookie Policy , Privacy Policy , and our Terms of Service. Earth Science Stack Exchange is a question and answer site for those interested in the geology, meteorology, oceanography, and environmental sciences. It only takes a minute to sign up. The Washington Post article Scientists discover hundreds of footprints left at the dawn of modern humanity describes the geological dating of stratified layers of mud by analyzing and dating minerals within each layer. But since floods jumble materials of different origins and ages together, that meant the scientists had to date dozens of different minerals. The youngest crystal in the footprint layer would represent the oldest possible age for the prints; the oldest crystal in the layer above it would represent the youngest they could be. Using the argon-argon dating technique, by which scientists measure the decay of an isotope called Argon into Argon in order to find the age of crystals, they came up with a rough approximation of the footprints’ age: 19, years at the oldest, 10, or 12, years at the youngest. I can’t exactly follow the logic, but I’m asking here about the dating process itself.

## Uranium-lead and potassium-argon dating

Radiometric dating is a means of determining the “age” of a mineral specimen by determining the relative amounts present of certain radioactive elements. By “age” we mean the elapsed time from when the mineral specimen was formed. Radioactive elements “decay” that is, change into other elements by “half lives. The formula for the fraction remaining is one-half raised to the power given by the number of years divided by the half-life in other words raised to a power equal to the number of half-lives.

One of the most widely used dating methods is the potassium-argon from the original story that explained how potassium-argon dating works.

Potassium-Argon radiometric dating is used to establish dates of lava flows. The reality of water running through any sample on earth is a strong problem for any reliance on this dating method. Running water dilutes potassium levels rapidly which equates to artificially older dates on specimens. This equates to this dating method becoming invalid because running water is abundant and may occur anywhere on earth or in the unobserved past.

Ask any farmer and they can tell you about the loss of potassium in soil because each year they have to drop fertilizer on their crops. Dating methods that rely on a decay rate between parent and daughter with potassium are rendered invalid. Other potassium-argon dating errors. We know the true ages of flows observed to form less than 50 years ago.

If the method fails on rocks when we have an independent eye-witness account, then why should we trust it on other rocks where there are no independent historical cross-checks? Argon gas, brought up from deep inside the earth within the molten rock, was already present in the lavas when they cooled.

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What are the most common forms of radiometric dating? What is potassium-argon dating? What is the most How are “too young” ages explained? Can those.

Potassium—argon dating , abbreviated K—Ar dating , is a radiometric dating method used in geochronology and archaeology. It is based on measurement of the product of the radioactive decay of an isotope of potassium K into argon Ar. Potassium is a common element found in many materials, such as micas , clay minerals , tephra , and evaporites. In these materials, the decay product 40 Ar is able to escape the liquid molten rock, but starts to accumulate when the rock solidifies recrystallizes.

The amount of argon sublimation that occurs is a function of the purity of the sample, the composition of the mother material, and a number of other factors. Time since recrystallization is calculated by measuring the ratio of the amount of 40 Ar accumulated to the amount of 40 K remaining. The long half-life of 40 K allows the method to be used to calculate the absolute age of samples older than a few thousand years.

## Radioactive dating

Potassium-Argon Dating Potassium-Argon dating is the only viable technique for dating very old archaeological materials. Geologists have used this method to date rocks as much as 4 billion years old. It is based on the fact that some of the radioactive isotope of Potassium, Potassium K ,decays to the gas Argon as Argon Ar By comparing the proportion of K to Ar in a sample of volcanic rock, and knowing the decay rate of K, the date that the rock formed can be determined.

How Does the Reaction Work? Potassium K is one of the most abundant elements in the Earth’s crust 2.

Potassium—argon dating has made it possible to establish that the earliest different argon the original story that explained how potassium-argon dating works.

Science in Christian Perspective. Radiometric Dating. A Christian Perspective. Roger C. Wiens has a PhD in Physics, with a minor in Geology. His PhD thesis was on isotope ratios in meteorites, including surface exposure dating. Radiometric dating–the process of determining the age of rocks from the decay of their radioactive elements–has been in widespread use for over half a century.

There are over forty such techniques, each using a different radioactive element or a different way of measuring them. It has become increasingly clear that these radiometric dating techniques agree with each other and as a whole, present a coherent picture in which the Earth was created a very long time ago.

## Potassium-argon (K-Ar) dating

Some updates to this article are now available. The sections on the branching ratio and dating meteorites need updating. Radiometric dating methods estimate the age of rocks using calculations based on the decay rates of radioactive elements such as uranium, strontium, and potassium. On the surface, radiometric dating methods appear to give powerful support to the statement that life has existed on the earth for hundreds of millions, even billions, of years.

We are told that these methods are accurate to a few percent, and that there are many different methods. We are told that of all the radiometric dates that are measured, only a few percent are anomalous.

technique, in which Potassium and Argon are measured. separately The K/Ar dating method applied to Holocene volcanic eruptions in Southern Italy. ).

If you’re seeing this message, it means we’re having trouble loading external resources on our website. To log in and use all the features of Khan Academy, please enable JavaScript in your browser. Donate Login Sign up Search for courses, skills, and videos. Science Biology library History of life on Earth Radiometric dating. Chronometric revolution. Potassium-argon K-Ar dating. K-Ar dating calculation. Atomic number, atomic mass, and isotopes. Current timeTotal duration

## Potassium-Argon Dating

Potassium-argon dating , method of determining the time of origin of rocks by measuring the ratio of radioactive argon to radioactive potassium in the rock. This dating method is based upon the decay of radioactive potassium to radioactive argon in minerals and rocks; potassium also decays to calcium Thus, the ratio of argon and potassium and radiogenic calcium to potassium in a mineral or rock is a measure of the age of the sample.

The calcium-potassium age method is seldom used, however, because of the great abundance of nonradiogenic calcium in minerals or rocks, which masks the presence of radiogenic calcium. On the other hand, the abundance of argon in the Earth is relatively small because of its escape to the atmosphere during processes associated with volcanism. The potassium-argon dating method has been used to measure a wide variety of ages.

Also called single crystal argon or argon-argon (Ar-Ar) dating, this method is a refinement of an older approach known as potassium-argon.

Potassium-Argon dating has the advantage that the argon is an inert gas that does not react chemically and would not be expected to be included in the solidification of a rock, so any found inside a rock is very likely the result of radioactive decay of potassium. Since the argon will escape if the rock is melted, the dates obtained are to the last molten time for the rock.

Since potassium is a constituent of many common minerals and occurs with a tiny fraction of radioactive potassium, it finds wide application in the dating of mineral deposits. The feldspars are the most abundant minerals on the Earth, and potassium is a constituent of orthoclase , one common form of feldspar. Potassium occurs naturally as three isotopes. The radioactive potassium decays by two modes, by beta decay to 40 Ca and by electron capture to 40 Ar.

There is also a tiny fraction of the decay to 40 Ar that occurs by positron emission. The calcium pathway is not often used for dating since there is such an abundance of calcium in minerals, but there are some special cases where it is useful. The decay constant for the decay to 40 Ar is 5.

## Radiometric Dating

Radiometric dating, often called radioactive dating, is a technique used to determine the age of materials such as rocks. It is based on a comparison between the observed abundance of a naturally occurring radioactive isotope and its decay products, using known decay rates. It is the principal source of information about the absolute age of rocks and other geological features, including the age of the Earth itself, and it can be used to date a wide range of natural and man-made materials.

Response: A good part of [Wiens’ article] is devoted to explaining how The reasons are discussed in the Potassium-Argon Dating section [of.

Roger C. Wiens has a PhD in Physics, with a minor in Geology. His PhD thesis was on isotope ratios in meteorites, including surface exposure dating. First edition ; revised version Radiometric dating–the process of determining the age of rocks from the decay of their radioactive elements–has been in widespread use for over half a century.

There are over forty such techniques, each using a different radioactive element or a different way of measuring them. It has become increasingly clear that these radiometric dating techniques agree with each other and as a whole, present a coherent picture in which the Earth was created a very long time ago. Further evidence comes from the complete agreement between radiometric dates and other dating methods such as counting tree rings or glacier ice core layers.

Many Christians have been led to distrust radiometric dating and are completely unaware of the great number of laboratory measurements that have shown these methods to be consistent. Many are also unaware that Bible-believing Christians are among those actively involved in radiometric dating. This paper describes in relatively simple terms how a number of the dating techniques work, how accurately the half-lives of the radioactive elements and the rock dates themselves are known, and how dates are checked with one another.

In the process the paper refutes a number of misconceptions prevalent among Christians today. This paper is available on the web via the American Scientific Affiliation and related sites to promote greater understanding and wisdom on this issue, particularly within the Christian community.