- Potassium-Argon (K-Ar) Dating by jed fong on Prezi.
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The technique is best used on material more than , years old -- such as the dating of layers associated with the earliest remains of hominids, notably in the Olduvai Gorge. Lava flows embedded with the deposits containing archaeological material have been dated. The process by which an archaeologist determines dates for objects, deposits, buildings, etc.
Relative dating , in which the order of certain events is determined, must be distinguished from absolute dating , in which figures in solar years often with some necessary margin of error can be applied to a particular event.
Potassium-Argon Dating
Unless tied to historical records, dating by archaeological methods can only be relative -- such as stratigraphy , typology , cross-dating , and sequence dating. Absolute dating , with some reservation, is provided by dendrochronology , varve dating , thermoluminescence , potassium-argon dating , and, most important presently, radiocarbon dating. Some relative dating can be calibrated by these or by historical methods to give a close approximation to absolute dates -- archaeomagnetism, obsidian hydration dating , and pollen analysis.
Still others remain strictly relative -- collagen content , fluorine and nitrogen test, and radiometric assay. The methods have varying applications, accuracy , range , and cost. Many new techniques are being developed and tested.
The basis for this technique is that a uranium isotope , U , as well as decaying to a stable lead isotope , also undergoes spontaneous fission. One in every two million atoms decays in this way. Fission is accompanied by an energy release which sends the resulting two nuclei into the surrounding material , the tracks causing damage to the crystal lattice.
K–Ar dating
These tracks can be counted under a microscope after the polished surface of the sample has been etched with acid. The concentration of uranium can be determined by the induced fission of U by neutron irradiation of the sample. Since the ratio of U to U is known, and is constant, a comparison of the number of tracks from natural fission and the number from induced fission will give the age of the sample. Though the method has been limited in its archaeological use so far, it has already proved a useful check method for potassium-argon dating for volcanic deposits at Olduvai Gorge, Tanzania, and obsidian , tephra beds, mineral inclusions in pottery , and some man-made glasses have also been dated.
A further use of the method is based on the fact that fission tracks disappear if the substance is heated about ? The study of earth history by correlating archaeological events to the timing and sequencing of geological events.
Specifically, it is the dating of archaeological data in association with a geological deposit or formation, such as the dating of Pleistocene human remains in the context of glacial advances and retreats. The term is applied to all absolute and relative dating methods that involve the earth 's physical changes, like radiocarbon dating , dendrochronology , archaeomagnetism, fluorine testing, obsidian dating , potassium-argon dating , thermoluminescence , and varve dating.
The time taken for half of a given amount of a radioactive substance to decay into a non-radioactive substance. It is also defined as the time taken for half the quantity of a radioactive isotope in a sample to decay and form a stable element. Potassium-argon dating , for instance, can provide the age of a specimen by clocking the rate at which radioactive isotopes of these elements have decayed. When radiometric methods cannot be applied, investigators may still ascribe a relative age to a fossil by relating it to the….
More About Potassium-argon dating 5 references found in Britannica articles Assorted References major reference In dating: Analysis of separated minerals In dating: Potassium—argon methods age determination of tektites In tektite: Chemistry and petrography of tektites archaeology In archaeology: Dating Homo erectus In Homo erectus: Help us improve this article! Contact our editors with your feedback. You may find it helpful to search within the site to see how similar or related subjects are covered.
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