Uranium 238 dating process
Uranium-238, the most prevalent isotope in uranium ore, has a half-life of about 4.5 billion years; that is, half the atoms in any sample will decay in that amount of time.
Uranium-238 decays by alpha emission into thorium-234, which itself decays by beta emission to protactinium-234, which decays by beta emission to uranium-234, and so on.
Because this method is useful for the period of time from about 100,000 years to 1,200,000 years before the present, it helps in bridging the gap between the carbon-14 dating method and the potassium-argon dating method.
First discovered in the 18th century, uranium is an element found everywhere on Earth, but mainly in trace quantities.
Other minerals sometimes used for uranium-lead dating include monazite, titanite and two other zirconium minerals, baddeleyite and zirconolite.
However, zircon is so overwhelming a favorite that geologists often just refer to "zircon dating." But even the best geologic methods are imperfect.
Natural uranium consists of three isotopes: uranium-238, uranium-235, and uranium-234. The nuclei of radioactive elements are unstable, meaning they are transformed into other elements, typically by emitting particles (and sometimes by absorbing particles).
This process, known as radioactive decay, generally results in the emission of alpha or beta particles from the nucleus.
In a rock twice as old there will be one 235U atom left for every three 207Pb atoms (Pb/U = 3), and so forth.
In these cases, the concordia diagram is a valuable tool.
Consider the concordia: as zircons age, they move outward along the curve.
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Uranium-234–uranium-238 dating, method of age determination that makes use of the radioactive decay of uranium-238 to uranium-234; the method can be used for dating of sediments from either a marine or a playa lake environment.