�鶹��Ѱ�����

Imagine discovering your birth date was 65 million years earlier than you thought.

This is the predicament the Grand Canyon is in, thanks to assistant professor Rebecca Flowers and her team who place the age of the iconic canyon at 70 million years old. Her research indicates dinosaurs may have been the first gawkers at the edge of the canyon long before today’s 5 million annual visitors.

For 150 years scientists have debated the age of the 280-mile-long canyon, with most placing the age between 5-6 million years. But Flowers and her team used an improved dating method that exploits the radioactive decay of uranium and thorium atoms to helium atoms locked in a mineral called apatite.

During the carving of the canyon, the helium-laden mineral grains cooled and moved closer to the surface. Looking at the temperature variations recorded by the apatite grains helped the team infer how much time had passed since there was significant excavation of the canyon. These new dating techniques have encouraged geologists like Flowers to redouble their efforts to pinpoint the age of the canyon.

“If it were simple, I think we would have solved this problem a long time ago,” Flowers says. “I expect that our interpretation that the Grand Canyon formed some 70 million years ago is going to generate a fair amount of controversy and I hope it will motivate more research to help solve this problem.” 

Read more at  and search for “Grand Canyon.”