Dating techniques are procedures used by scientists to determine the age of rocks, fossils, or artifacts. Relative dating methods tell only if one sample is older or younger than another; absolute dating methods provide an approximate date in years. The latter have generally been available only since Many absolute dating techniques take advantage of radioactive decay , whereby a radioactive form of an element decays into a non-radioactive product at a regular rate. Others, such as amino acid racimization and cation-ratio dating, are based on chemical changes in the organic or inorganic composition of a sample.
Historical Geology/Absolute dating: an overview
Layers that are farther beneath the surface are usually older in relativity to the layers that are closer to the surface. Geologists look for index fossils, evidences of specific organisms that were widespread, rapidly evolving, plentiful, and only existed during a specific geologic time period. Trilobites are an example of one such index fossil. When an index fossil is identified in a rock layer, it can be assumed that the age of the rock falls within the time period of the organism's existence.
Historical Geology/Fossils and absolute dating
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Geologists use two techniques to date rock layers. The first technique is called " relative dating. When one finds layers at an angle, especially at a sharp angle, one can regard the formation as due to shifts in the earth that occurred after the layers were deposited.