Scientists measure the ages of things past by using natural, radioactive materials that change, or decay, into other chemical elements at constant rates. By comparing what's left of the original material with the amount of decay product, an age can be calculated. Different elements decay at different rates, allowing determination of a wide range of ages.
Most such materials were formed before the formation of the solar
system or from series where one radioactive substance decays to a different radioactive
element. But not 14carbon, widely used to date things
within the past 40,000 years. This form of carbon is constantly being created by
interaction of cosmic rays and nitrogen atoms. But this interaction is affected by the
earth's magnetic field—and that fluctuates, resulting in different rates of
14carbon creation through time and thus distortion of
true age. Luckily, by calibrating 14carbon ages by
reference to matter of known ages, especially tree rings, we finally can correct these
deficiencies. The artifacts of our desert's past are now known with greater
accuracy than ever before.
Contributor: Arthur H. Harris, Laboratory for Environmental Biology, Centennial Museum, University of Texas at El Paso.
Desert Diary is a joint production of the Centennial Museum and KTEP National Public Radio at the University of Texas at El Paso.