The wonderful property of isochron methods is: if one of these requirements is violated, it is nearly certain that the data will indicate the problem by failure to plot on a line.

(This topic will be discussed in much more detail below.) Where the simple methods will produce an incorrect age, isochron methods will generally indicate the unsuitability of the object for dating.

The simplest form of isotopic age computation involves substituting three measurements into an equation of four variables, and solving for the fourth.

The equation is the one which describes radioactive decay: If one of these assumptions has been violated, the simple computation above yields an incorrect age.

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.

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.

The X-axis of the graph is the ratio of in a closed system over time.(For brevity's sake, hereafter I will refer to the parent isotope as ).In addition, it requires that these measurements be taken from several different objects which all formed at the same time from a common pool of materials.Consider some molten rock in which isotopes and elements are distributed in a reasonably homogeneous manner.Its composition would be represented as a single point on the isochron plot: Note that the above is somewhat simplified.Isochron methods avoid the problems which can potentially result from both of the above assumptions.

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