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When a rock undergoes metamorphism, some or all of its argon can be outgassed.
If all the argon was lost, this would reset the K-Ar clock to zero, and dating the rock would give us the time of metamorphism; and if we recognized the rock as metamorphic this would actually be quite useful.
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.
The severity of this problem decreases as the accuracy of our instruments increases.
Still, as a general rule, the proportional error in K-Ar dating will be greatest in the youngest rocks.
The reasoning is as follows: the atmosphere does not only contain Ar as being atmospheric argon.
It is therefore essential to have as much information as possible about the material being dated and to check for possible signs of alteration.Another concern with K-Ar dating is that it relies on there being no Ar in the rock when it was originally formed, or added to it between its formation and our application of the K-Ar method.Because argon is inert, it cannot be chemically incorporated in the minerals when they are formed, but it can be physically trapped in the rocks either during or after formation. If the source of this argon is atmospheric contamination, then we can correct for this.It may be used to date a wide range of natural and man-made materials.Fossils may be dated by taking samples of rocks from above and below the fossil's original position.