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The rocky walls of the Grand Canyon look like a box of melted crayons.
They have layers of red, pink, purple, brown, green, gray, and yellow. No giant machines dug the canyon. It was created by the mighty Colorado River. Of course, the river had help from small streams and tributaries. Wind, rain, snow, and ice helped. And so did the Earth’s moving tectonic plates.
The canyon is a slow and steady work in progress. It began more than 6 million years ago and is still forming today.
The Mighty Colorado
The strong waters of the Colorado and its branches picked up billions of bits of grit. The grit is called sediment. It was made of gravel, mud, sand, and silt, or powdered rock. It made the river like a powerful tool that wore away the rock and shaped the canyon. The sediment still scours away. It makes the canyon deeper by about six inches every thousand years.
Explore the Grand Canyon
The Colorado River’s 1,450 miles start in Colorado’s Rocky Mountain National Park. It starts out at 9,010 feet above sea level. It goes into the Grand Canyon at Lee’s Ferry, at just over 3,000 feet. The river reaches the lower end of the canyon at the Grand Wash Cliffs. By then, it has dropped another 2,200 feet.
▲ Earth’s crust is made up of huge slabs of rock, called plates. At one time, western North America was at or below sea level. About 70 million years ago, the Pacific plate crashed into the North American plate. The Pacific plate slid under its neighbor. That created a 130,000-square-mile area a mile high. It’s called the Colorado Plateau. Then, aftershocks formed the Rocky Mountains. Before that crash, the ancestor of the Colorado River had wandered over the plateau. Afterward, the water began running downhill toward the Gulf of California. That was the start of the Grand Canyon.
▲ The Colorado River can be as deep as 90 feet and as shallow as 6 feet. Its average depth is about 20 feet. The river has rapid and calm waters. The rapids are usually in shallow places. The calm waters are mostly found in deeper parts.
◀ Today, the river is bluish-green. Sediment and silt stay behind the Glen Canyon Dam in Lake Powell. The dam was finished in 1963. It has cut the amount of water flowing into the Colorado River by about 90 percent.
