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Grand Canyon

The Colorado River courses through the Grand Canyon in Arizona, USA. The Grand Canyon is a great gorge that twists across the dry, rocky region of Arizona, USA for nearly 450 kilometres (280 miles). It is one of the world’s most spectacular examples of river erosion. The Colorado River cut a deeper and deeper channel as the land over which it flowed slowly began to push upwards. The soft rock layers wore away more easily than the hard layers, which today stand out as near-vertical cliff faces.

The formation of the Grand Canyon

Stages of formation

The Colorado River once flowed gently across the desert (1). Then, between 10 and 12 million years ago, the land beneath it began to rise (2). It did so only by about a quarter of a millimetre per year, but the river kept pace with it, cutting a deeper channel to preserve its downward course to the sea. It carved through different layers of rock, some hard, some soft (3). The soft rock wore away more easily than the hard, which today stands out as vertical cliff faces.

Colorado River

The Grand Canyon is 29 kilometres (18 miles) wide at its widest and more than 1800 metres (about 6000 feet) deep at its deepest.

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