How does potassium 40 dating work rule of scarcity dating

Posted by / 24-Sep-2017 05:43

The isotope potassium-39 makes up about 93% of natural potassium.Potassium-40 is radioactive but has such a long half-life that it is primordial - it has been around since the earth was being formed. About 10.7% decays to Argon-40 by emitting a positron.Argon-Argon dating is similar to Potassium-Argon dating, but it requires less material.The Potassium 39 in the sample is irradiated to become Argon 39, then the ratio of the gas is compared.As noted in the comments the wikipedia articles (at the time this question was submitted) are contradictory.

This also assumes that there is no other source of argon like trapped air.If so, then the K-Ar and Ar-Ar "dating" of crustal rocks would be similarly questionable.When muscovite (a common mineral in crustal rocks) is heated to 740°-860°C under high Ar pressures for periods of 3 to 10.5 hours it absorbs significant quantities of Ar, producing K-Ar "ages" of up to 5 billion years, and the absorbed Ar is indistinguishable from radiogenic argon ( In other experiments muscovite was synthesized from a colloidal gel under similar temperatures and Ar pressures, the resultant muscovite retaining up to 0.5 wt% Ar at 640°C and a vapor pressure of 4,000 atmospheres.The youngest crystal in the footprint layer would represent the oldest possible age for the prints; the oldest crystal in the layer above it would represent the youngest they could be.Using the argon-argon dating technique, by which scientists measure the decay of an isotope called Argon-40 into Argon-39 in order to find the age of crystals, they came up with a rough approximation of the footprints' age: 19,000 years at the oldest, 10,000 or 12,000 years at the youngest.

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