Geography
How Canyons Are Formed Through River Erosion Over Millennia
Quick fact
The Grand Canyon in Arizona is over 277 miles long, up to 18 miles wide, and reaches a depth of over a mile, all carved by the Colorado River over about 5 to 6 million years.
Why this is interesting
Think of a river as a slow-moving knife, slicing through solid rock over millions of years. How does water—something so soft—carve the world's most dramatic canyons?