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It can be determined experimentally or by using the half-life, and is equivalent to the fraction of atoms that decays per some interval of time.For the Rb-Sr system, λ = 1.42 x10 The graph shown below indicates the points plotted, the regression line and its equation.This is in part because uranium and lead are not retained in rocks as easily as some others, and in part because the parent isotopes and daughter products are not even directly related.For the isotopes uranium-235 and uranium-238 to respectively become lead-207 and lead-206, they must first undergo a serious of highly unstable transformations into isotopes with very short half-lives.However, if one knows the scientific formula for interpreting these transitions, the results can be "highly precise" according to paleontologist Guy Narbonne (Kerr, 789).The half-life of uranium-235 is 704 million years, while the half-life of uranium-238 is 4.5 billion years.These radioactive isotopes and their half-lives can be used as our natural clock, i.e., we can find out how old certain rocks are from this information. Using Math to Find the Age of Rock in Southwest Colorado In this section, we will guide you through the process of finding the age of a sample of gabbro found at Electra Lake, just north of Durango in southwest Colorado.

Since argon is a noble gas, it would have escaped the rock-formation process, and therefore any argon in a rock sample should have been formed as a result of k-40 decay.It was discovered that some chemical elements, notably uranium and thorium, are strongly radioactive.These elements occur naturally in nearly all rocks, and they account for the radioactivity you could observe with a Geiger counter.If there is too much daughter product(in this case nitrogen-14), age is hard to determine since the half-life does not make up a significant percentage of the material's age.The range of practical use for carbon-14 dating is roughly a few hundred years to fifty thousand years.

In an igneous rock formation, the entirety of the cooled rock will have the same ratio of strontium-87 and strontium-86 (another stable isotope).