Dating geological specimens

24-Aug-2019 14:20 by 8 Comments

Dating geological specimens

Radiometric dating is self-checking, because the data (after certain preliminary calculations are made) are fitted to a straight line (an "isochron") by means of standard linear regression methods of statistics.The slope of the line determines the date, and the closeness of fit is a measure of the statistical reliability of the resulting date.

Some of the isotopes used for this purpose are uranium-238, uranium-235 and potassium-40, each of which has a half-life of more than a million years.The results showed that Ötzi died over 5000 years ago, sometime between 33 BC. Uranium has a very long half-life and so by measuring how much uranium is left in a rock its approximate age can be worked out. In a related article on geologic ages (Ages), we presented a chart with the various geologic eras and their ages.Technical details on how these dates are calculated are given in Radiometric dating. As with any experimental procedure in any field of science, these measurements are subject to certain "glitches" and "anomalies," as noted in the literature.Here is one example of an isochron, based on measurements of basaltic meteorites (in this case the resulting date is 4.4 billion years) [Basaltic1981, pg. Skeptics of old-earth geology make great hay of these examples.In a separate article (Radiometric dating), we sketched in some technical detail how these dates are calculated using radiometric dating techniques.

As we pointed out in these two articles, radiometric dates are based on known rates of radioactivity, a phenomenon that is rooted in fundamental laws of physics and follows simple mathematical formulas.

Unfortunately, these elements don't exist in dinosaur fossils themselves.

Each of them typically exists in igneous rock, or rock made from cooled magma.

The rejection of the validity of fossils and of dating by religious fundamentalists creates a problem for them: Fossil sequences were recognized and established in their broad outlines long before Charles Darwin had even thought of evolution.

Early geologists, in the 1700s and 1800s, noticed how fossils seemed to occur in sequences: certain assemblages of fossils were always found below other assemblages. Since 1859, paleontologists, or fossil experts, have searched the world for fossils.

Fossils, however, form in sedimentary rock -- sediment quickly covers a dinosaur's body, and the sediment and the bones gradually turn into rock.

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