Cosmic rays to date geology.

Cosmic rays to date geology

In geology, the past often holds the key to the future. In order to predict the potential of an earthquake or a landslide in a certain location, geologists like to know when these events last wracked the area -- a question sometimes quite difficult to answer. Scientists are now developing a promising technique using cosmic rays to help in the geological dating game.

Cosmic rays are high-energy radiation from space that can penetrate Earth's atmosphere. When this radiation hits rocks on the surface, it alters certain atoms to create radioactive chlorine-36. The rays can reach only a few feet into the ground, and so affect rocks on or near the surface. Therefore, it is possible to tell how long a rock has been at the surface by measuring its chlorine-36 content, says Fred M. Phillips of New Mexico Institute of Mining and Technology in Socorro. Phillips and his colleagues from New Mexico Tech and from the University of Rochester (N.Y.) report they have now tested the method by dating boulders atop glacially formed ridges in the Sierra Nevada mountains. Since earthquakes and other geological processes uncover new surfaces, the technique can help scientists date these events, says Phillips, who received the F.W. Clarke award from the Geochemical Society this month for work on chlorine-36 dating.