Geologic age dating methods

Absolute dating places events or rocks at a specific time.If a geologist claims to be younger than his or her co-worker, that is a relative age.If a geologist claims to be 45 years old, that is an absolute age.Superposition: The most basic concept used in relative dating is the law of superposition.For centuries people have argued about the age of the Earth; only recently has it been possible to come close to achieving reliable estimates.In the 19th century some geologists realized that the vast thicknesses of sedimentary rocks meant that the Earth must be at least hundreds of millions of years old.Geologists generally know the age of a rock by determining the age of the group of rocks, or formation, that it is found in.The age of formations is marked on a geologic calendar known as the geologic time scale.

This "radiometric" approach has superseded all other techniques for determining absolute ages. Their nuclei tend to emit particles spontaneously - ie, they are radioactive.These discussions were rendered obsolete by the discovery of radioactivity in 1896 by the French physicist Henri Becquerel.The existence of radioactivities of various kinds in rocks has enabled earth scientists to determine the age of the Earth, the moon, meteorites, mountain chains and ocean basins, and to draw up a reasonably accurate time scale of evolution.his document discusses the way radiometric dating and stratigraphic principles are used to establish the conventional geological time scale.It is not about the theory behind radiometric dating methods, it is about their , and it therefore assumes the reader has some familiarity with the technique already (refer to "Other Sources" for more information).

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