Radiometric dating definition yahoo
When they die, they stop exchanging carbon with the biosphere and their carbon 14 content then starts to decrease at a rate determined by the law of radioactive decay.Radiocarbon dating is essentially a method designed to measure residual radioactivity.The method does not count beta particles but the number of carbon atoms present in the sample and the proportion of the isotopes. Samples that have been radiocarbon dated since the inception of the method include charcoal, wood, twigs, seeds, bones, shells, leather, peat, lake mud, soil, hair, pottery, pollen, wall paintings, corals, blood residues, fabrics, paper or parchment, resins, and water, among others.Physical and chemical pretreatments are done on these materials to remove possible contaminants before they are analyzed for their radiocarbon content.It is rapidly oxidized in air to form carbon dioxide and enters the global carbon cycle.Plants and animals assimilate carbon 14 from carbon dioxide throughout their lifetimes.Measurements should be taken on samples from different parts of the rock body.This helps to counter the effects of heating and squeezing, which a rock may experience in its long history.
Fossils may be dated by taking samples of rocks from above and below the fossil's original position.
Radiometric dating (often called radioactive dating) is a way to find out how old something is.
The method compares the amount of a naturally occurring radioactive isotope and its decay products, in samples. It is the main way to learn the age of rocks and other geological features, including the age of the Earth itself.
Contamination from outside, or the loss of isotopes at any time from the rock's original formation, would change the result.
It is therefore essential to have as much information as possible about the material being dated and to check for possible signs of alteration.
Liquid scintillation counting is another radiocarbon dating technique that was popular in the 1960s.