Age dating metamorphic rocks

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A coin, vessel, or other common artifact could link two archaeological sites, but the possibility of recycling would have to be considered.

It should be emphasized that linking sites together is essential if the nature of an ancient society is to be understood, as the information at a single location may be relatively insignificant by itself.

Just as the use of the fossil record has allowed a precise definition of geologic processes in approximately the past 600 million years, absolute ages allow correlations back to Earth’s oldest known rocks formed more than 4 billion years ago.

In fact, even in younger rocks, absolute dating is the only way that the fossil record can be calibrated.

These include some that establish a relative chronology in which occurrences can be placed in the correct sequence relative to one another or to some known succession of events.

Radiometric dating and certain other approaches are used to provide absolute chronologies in terms of years before the present.

To date past events, processes, formations, and fossil organisms, geologists employ a variety of techniques.Episodes of global volcanic activity, rifting of continents, folding, and metamorphism are defined by absolute ages.The results suggest that the present-day global tectonic scheme was operative in the distant past as well.plate tectonics has had a profound impact on the scientific understanding of our dynamic planet.Similarly, in geology, if distinctive granitic pebbles can be found in the sediment beside a similar granitic body, it can be inferred that the granite, after cooling, had been uplifted and eroded and therefore was not injected into the adjacent rock sequence.Although with clever detective work many complex time sequences or relative ages can be deduced, the ability to show that objects at two separated sites were formed at the same time requires additional information.

In addition, they have had to develop special techniques with which to dissolve these highly refractory minerals without contaminating the small amount (about one-billionth of a gram) of contained lead and uranium on which the age must be calculated.

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