Grand Canyon

The Grand Canyon is a huge canyon in northern Arizona. A canyon is a deep valley with steep sides. The Grand Canyon was carved into the rock by the Colorado River. It is 277 miles long. It is up to 18 miles wide from one side to the other. In some places it is more than a mile deep. It has been a national park since 1919, and it is one of the most visited places in the United States.

The walls of the canyon are made of layers of rock. The oldest rock is at the bottom, near the river. It is almost two billion years old, which makes it some of the oldest rock you can see anywhere on the surface of the Earth. The top layers are much younger — only about 270 million years old. Each layer was made at a different time, from sand, mud, or seashells that piled up in ancient seas, deserts, rivers, or swamps.

The size of the canyon is hard to picture in numbers alone. The Empire State Building is 1,454 feet tall. You could stack five of them inside the canyon, and the top of the highest one still would not reach the rim. Hikers usually take two days to walk from the top down to the river. It takes even longer to climb back up.

The canyon was carved by water over millions of years. As the land around the Colorado River was slowly pushed upward by movements deep inside the Earth, the river kept flowing. It cut downward into the rock as the land rose beneath it. Bit by bit, the river carried away the rock. This process of wearing away rock is called erosion.

How old is the canyon? That is actually still an open question. For a long time, most scientists thought the Colorado River carved the whole canyon about six million years ago. Newer research has suggested that parts of the canyon might be much older — maybe 70 million years old, back when dinosaurs still roamed the Earth. Other scientists think the older date is wrong. The question is not settled, and new evidence keeps coming in.

People have lived in and around the Grand Canyon for thousands of years. Eleven Native American tribes today have deep connections to the land, including the Havasupai, Hualapai, Navajo, Hopi, Zuni, and Southern Paiute. The Havasupai still live inside the canyon today, in a small village called Supai that you can only reach by foot, horse, or helicopter. About five million people visit the park each year.