Scientists at the Lamont-Doherty Geological Laboratory of Columbia University at Palisades, N.Y., reported today in the British journal Nature that some estimates of age based on carbon analyses were wrong by as much as 3,500 years.Unlike people, you can’t really guess the age of a rock from looking at it.Yet, you’ve heard the news: Earth is 4.6 billion years old. That corn cob found in an ancient Native American fire pit is 1,000 years old. Geologic age dating—assigning an age to materials—is an entire discipline of its own.Geologic assessment of active tectonism depends on two key measures: the age and the amount of deformation of a given stratigraphic unit.The amount of deformation can normally be measured with greater accuracy than the age.
Because it is radioactive, carbon 14 steadily decays into other substances.
They arrived at this conclusion by comparing age estimates obtained using two different methods - analysis of radioactive carbon in a sample and determination of the ratio of uranium to thorium in the sample.
In some cases, the latter ratio appears to be a much more accurate gauge of age than the customary method of carbon dating, the scientists said.
Of course, there are many problems with such dating methods, such as parent or daughter substances entering or leaving the rock, as well as daughter product being present at the beginning.
Here I want to concentrate on another source of error, namely, processes that take place within magma chambers.