Deciphering the Grand Canyon

  • Exhibition Text

    • For geologists, the Grand Canyon is one of the most spectacular natural laboratories on our planet. The canyon's formations embody the enormity of geological time, and its vast size and intricately structured towers and walls demonstrate the immense power of erosion. Geologists closely inspect every face of the canyon, and read the layers of its rocks like the page of a book. They construct detailed maps and determine its three-dimensional structure to understand how the canyon and the rocks exposed in it formed.

      The Grand Canyon Region
      The Colorado Plateau is an uplifted area of flat plains, broad mesas, great canyons, and spectacular vistas. As the plateau rose, the Colorado River cut its way downward, creating the mile-deep chasm of the Grand Canyon. This extraordinary depth resulted from the powerful erosion of the river. Its power to erode is a consequence of its steep drop combined with the rapid uplift of the plateau. These processes continue today.  

      Carving the Canyon
      The Grand Canyon has been eroding at the geologically rapid rate of 3 centimeters every hundred years. The erosion is rapid because the Kaibab Plateau, a high tableland that encompasses northern Arizona, is rising quickly. In addition, the river drops more than 600 meters from Lake Powell to Lake Mead, and thus its rapid current has great power to erode. Boulders from the cliffs fall into the river, where the water breaks them down to pebbles, sand, and finally, silt. 

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Scientists at Work: Grand Canyon

The Grand Canyon extends more than 400 kilometers, from Lake Powell to Lake Mead, and it cuts 2 kilometers into the crust, revealing 1.7 billion years of the Earth's geological history. The geology of the Grand Canyon was first systematically studied by the explorer-geologist John Wesley Powell, in three epic exploratory trips between 1869 and 1872. More than a century later, we are still interpreting the details of its formation and of the fossil life contained within its steep rock walls.

In this video, Dr. James Webster from the American Museum of Natural History explores the Grand Canyon in Arizona with Dr. George Billingsley from the United States Geological Survey and Dr. Steven Reynolds from Arizona State University.

 

This video was produced in 1999 for the David S. and Ruth L. Gottesman Hall of Planet Earth at the American Museum of Natural History.

Video credits:
American Museum of Natural History
Ballentyne Brumble Communications

In This Section

Uplift and erosion

Uplift and erosion

About 70 million years ago, the region of what is now northern Arizona started to rise.

When did the canyon form?

When did the canyon form?

The Shivwits Plateau, just to the north of the Grand Canyon, contains gravels deposited by rivers flowing from the southwest.

Building the canyon's layers

Building the canyon's layers

When the layers at the bottom of the Grand Canyon formed 1.7 billion years ago, Arizona was at the western edge of North America.

The sea retreats, the sea returns

The sea retreats, the sea returns

The upper walls of the Grand Canyon reveal sedimentary rock layers formed in marine and continental environments between 550 and 260 million years ago.

Energy and transport

Energy and transport

The size of rock fragments in sedimentary rocks indicates the amount of energy needed to deposit them.