Transcript:

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.

Vocabulary:

drawn 吸引

to take in 吸收；領(lǐng)會

scale n. 規(guī)模；比例

problematic adj. 問題的；有疑問的

gathering n. 聚集；集會

origin n. 起源；原點

segments n. 片段；段數(shù)

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