I got it from
How old is the Grand Canyon? | The Real Age of the Grand Canyon.
However, when I first scanned the site, my eyes focused in on the 70,000. It didn't register that other scientists think it may be only I apologize for the confusion. At any rate, the reason for the discrepancy is that the Grand Canyon is not equally old. There are parts of it that are much younger than other parts.
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Some scientists believe that the Grand Canyon is 70 million years old. Others contend that the natural wonder is only between five and six million years old.
Both are right.
Scientists examined rocks from the Grand Canyon with the so-called thermo chronology method. With this method, the U.S. researchers were able to determine when the Earth’s interior hot rock came to the surface and cooled there. Accordingly, two middle sections, called the Hurricane segment and the Eastern Grand Canyon segment, were formed between 50 and 70 million and between 15 and 25 million years ago.
However, two other sections are much younger – they were carved out only five or six million years ago. Their creation formed a single canyon which today averages about 4,000 feet in depth. Over the past four million years ago caused the erosion caused the newly formed giant canyon to grow deeper, wider and longer."