Grand Canyon

A mile-deep gorge carved by the Colorado River, exposing nearly two billion years of rock layers.

The canyon is famous for its colourful cliffs. Its walls are made of stacked rock layers, like the pages of a giant book, and together they show nearly two billion years of Earth's history. Native American peoples have lived in and around the canyon for thousands of years, and the Pueblo people treated it as a holy place. Its rocks are some of the best-preserved records of early North American history anywhere.

How the canyon formed

The story starts almost two billion years ago, when the dark rocks now found at the very bottom of the canyon were formed. Over a very long time, layer after layer of sand, mud and sea creatures settled on top. Then, between about 70 and 30 million years ago, slow movements of the Earth's crust pushed the whole region upward into a high, flat area called the Colorado Plateau. Starting about 5 to 6 million years ago, the Colorado River began cutting downward, while rain, ice and side streams widened the walls.

Reading the rock layers

Geologists read the canyon from the bottom up: the oldest rocks are at the bottom and the youngest are on top. The top layer, the Kaibab Limestone, actually formed on the floor of an ancient sea, yet today it sits as high as about 2,700 metres above sea level. The North Rim is roughly 300 metres higher than the South Rim, so it is cooler and gets more snow, and its road is closed in winter.

People and wildlife

The first European known to have seen the canyon was the Spanish explorer García López de Cárdenas, in 1540. President Theodore Roosevelt loved the area and helped protect it; it became a national monument in 1908. Today the park is home to mule deer, desert bighorn sheep, black bears and elk, and very rare California condors, giant vultures that were brought back to the region after almost disappearing, now soar over the eastern part of the park.

On the globe

The model shows the canyon as eroded, step-like land with flat rock layers, standing buttes, side canyons and the Colorado River winding through the bottom. Zoom in to follow the river and count the coloured stripes in the walls.