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In a related article on geologic ages (Ages), we presented a chart with the various geologic eras and their ages.

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Their method, a type of radiometric dating called uranium-lead (U-Pb) dating, relies on the fact that uranium isotopes radioactively decay to form lead isotopes.

By comparing the amount of each isotope in a sample, the age of the sample can be calculated.

Clearly, Sedimentary Rocks A were deposited and deformed before the Volcanic Dyke intruded them.

These were then eroded and Sedimentary Rocks B were deposited.

Radiometric dating not only supports the geologic "evolution" of the Grand Canyon, it validates a central tenet in a much different theory of evolution - a theory introduced by Charles Robert Darwin in his 1859 publication, An important criticism of Darwin's theory of evolution was its requirement for "an almost infinite number of generations", when evidence at the time suggested earth was less than 100 million years old.

Nearly 50 years after Darwin published , research on radioactive elements in rocks provided the first reliable evidence that the earth was old enough to accommodate the evolution of complex organisms.From the mapped field relationships, it is a simple matter to work out a geological cross-section and the relative timing of the geologic events.His geological cross-section may look something like Figure 2.In 1907, Bertram Boltwood published an article describing a novel, radiometric method for determining the age of minerals - a method he used to date a rock sample at more than 2 billion years: to search the CAS databases for additional information about radiometric dating and evolution.If your organization is enabled to use the web version of Sci Finder, you can click the links in this article to directly access details of the cited references.Geological Time | Geologic Time Scale | Plate Tectonics | Radiometric Dating | Deep Time | Geological History of New Zealand | Radiometric Dating Radiometric measurements of time Since the early twentieth century scientists have found ways to accurately measure geological time.

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