Metamorphic processes invalidate radiometric dating methods

Each such age would match the result given by the isochron.

Gain or loss of In order to make the figures easy to read (and quick to draw), the examples in this paper include few data points.

Unfortunately, one must wade through some hefty math in order to understand the procedures used to fit isochron lines to data.

General comments on "dating assumptions" All radiometric dating methods require, in order to produce accurate ages, certain initial conditions and lack of contamination over time.

Age "uncertainty" When a "simple" dating method is performed, the result is a single number.

There is no good way to tell how close the computed result is likely to be to the actual age.

There are minor differences between isotopes of the same element, and in relatively rare circumstances it is possible to obtain some amount of differentiation between them. The effect is almost always a very small departure from homogeneous distribution of the isotopes -- perhaps enough to introduce an error of 0.002 half-lives in a non-isochron age. but it is rare and the effect is not large enough to account for extremely old ages on supposedly young formations.) as minerals form.

This results in a range of X-values for the data points representing individual minerals.

(Rocks which include several different minerals are excellent for this.) Each group of measurements is plotted as a data point on a graph.

The X-axis of the graph is the ratio of in a closed system over time.

The better the fit of the data to the line, the lower the uncertainty.

For further information on fitting of lines to data (also known as regression analysis), see: Note that the methods used by isotope geologists (as described by York) are much more complicated than those described by Gonick.

However, the methods must be used with care -- and one should be cautious about investing much confidence in the resulting age...