英语听力精选进阶版 14360（在线收听）

Grand Canyon 'formed recently'

Summary

27 January 2014

The world-famous Grand Canyon in the American state of Arizona may be a lot younger than we thought. New research suggests it might be only five to six million years old. Earlier studies had claimed the canyon was perhaps 70 million years old.

Reporter:

Jonathan Amos

Report

Millions of tourists are drawn each year to the Grand Canyon to see its impressive rocks, which record nearly two billion years of Earth history. Running for almost 450km and to a depth of 1,800m, it is almost too vast to take in. 

Its huge scale has also been problematic for scientists who've spent years gathering data from different locations through the canyon to try to work out its true age. 

Some of the most recent investigations had indicated an ancient origin, while others thought it was much younger. 

Now a new study in the Nature Geoscience journal pulls it all together. It finds, yes, the Grand Canyon has very old segments, but the full system was only cut into the form we know today by the Colorado River just over five million years ago.