Time, Cratons, and Voyageurs NP

One short-lived isotope is 14 C, alsoknown as C-14 or radiocarbon. “Normal”carbon is 12 C and is not radioactive.Since 14 C has a half-life of only 5730years, it “should” be nearly all gone,except that more is continuously beingmade in Earth’s upper atmosphere byhigh-energy radiation causing neutrons tosmash into 14 N, converting it to 14 C.Any living organism which exchangesCO 2 with the atmosphere will have a ratioof 14 C to 12 C which is controlled by theamount of 14 C in the air. Upon death,however, the continuously decaying 14 C isno longer replenished.Radiocarbon dating is useful indetermining the age of organic materialup to about 70,000 years, with carefulmeasurement.Useful for archaeology and some aspectsof recent geology.