The Grand Canyon, located in the northwestern corner of Arizona, stretches more than 277 miles (446 km).
It is more than 1 mile (1.6 km) deep in places and about 18 miles (29 km) wide at its widest point.
This amazing gash in the earth was cut by the powerful flow of the Colorado River and the result is that nearly two billion years of the Earth’s geological history have been exposed.
Recent geological evidence suggests the Colorado River established its course through the Grand Canyon at least 17 million years ago.
Geologists can learn a lot about the ancient history of this region by studying the many layers of rock that the river has exposed.