Below you will find graphs that illustrate the decay of parent isotopes
and the growth of daughter isotopes for four geologically important
isotopic systems. The half-life of U-235 decaying to Pb-207 is 713
million years. Note that this half-life can be obtained from the graph
at the point where the decay and growth curves cross. Determine the
half-lives for the other three isotopes and enter your estimate into
the text fields below each graph. Note the differences in scale between
the various graphs. Click the Next button when you are ready to go
continue.
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