The exact processes that formed the Grand Canyon remain a compelling puzzle. But studies suggest this giant gorge was cut by flowing water just a few million years ago – a blink in geological time. The canyon’s rocks have a much longer history – the oldest are around 2 billion years old.
Perhaps 30-70 million years ago, these rock layers were uplifted to form the high, flat Colorado Plateau. There are several theories explaining how and why this uplift happened. Around 5-6 million years ago, the Colorado River changed its course and began to carve down through the plateau.
The river uses sediment and rocks like chisels and sandpaper to chip away its channel. It has tremendous erosive power because it is fast flowing with a large volume, enabling it to carry a large amount of debris. Arizona’s arid climate means rock is unprotected by vegetation, making it more susceptible to erosion.
Five of North America’s seven life zones – areas with similar plants and animals – appear within the Grand Canyon’s one-mile high walls. While desert scrub like cacti are found close to the river, a spruce-fir forest covers the North Rim above 2,500m.
More than 1,500 plant, 355 bird, 89 mammal, 56 reptile and amphibian, and 17 fish species are found around the canyon. Other wildlife species are rare or protected. For example, the Californian condor is among the world’s rarest birds.
The Grand Canyon by numbers
Average depth: 1 mile
Length: 277 river miles
Minimum width: 600ft
Maximum width: 18 miles
Age: 2 billion years
Vistors per year: 4.5 million￼
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