fis|sion-track dating

fis|sion-track dating «FIHSH uhn TRAK»,

a method of determining age of rocks and other geological formations by counting the characteristic tracks left by spontaneous fission of uranium 238 during the lifetime of each sample. The number of tracks is proportional to the age of the sample. »

Fission-track dating is direct and visual and has proved to be applicable to many materials and over an enormous range of ages. The critical factor is the uranium content of the material to be dated. A concentration of one part per million—which is common in rocks—provides enough tracks to date an object older than some 100,000 years easily (Scientific American).