How does a river carve a canyon a mile deep?
The Grand Canyon is over a mile deep and took a river millions of years to cut. Scientists still disagree about exactly how old it is.
▶ Start the storyA river carves a canyon by cutting down through rock for a very long time while the land beneath it rises. The Grand Canyon is the famous example: a steep-sided canyon carved by the Colorado River in Arizona, 277 miles long, up to 18 miles wide and over a mile deep. It is not a crack in the ground. It is a river valley that kept getting deeper.
1,857 m
The key is . The Colorado , the high plateau the river cuts across, was pushed upward, and as it rose, the river's channel became steeper. A steeper stream runs faster, and a faster stream is better at cutting through rock. The Colorado River responded to the rise by cutting its channel faster and deeper.
The cutting does not stop at the river. The river's cut down too, and the cliffs retreat, so the canyon deepens and widens at the same time. That is how the walls end up so far apart.
All that cutting laid the rock layers open like pages of a book. Nearly two billion years of Earth's history are exposed, from the two-billion-year-old Vishnu Schist at the bottom to the 270-million-year-old Kaibab Limestone on the rim.
The river itself is muddy: the name Colorado comes from the Spanish for "colored reddish" because of its heavy load. In 1869 Major John Wesley Powell led the first expedition down the canyon.
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Recap
Rising land makes a river steeper and faster, and faster water cuts down faster.
💡 A trick to remember it · Lift the land and the river speeds up: a tilted slide cuts a deeper groove than a flat one.
Surprising fact · The canyon exposes nearly two billion years of Earth's history, yet scientists still debate how old the canyon itself is.
Sources (2)
No source, no claim. Every fact in this lesson (13 claims) cites at least one of these.