Question

Scientists sometimes describe the canyon walls as a timeline. How is this description accurate?

Answer 1

Answer: Canyons Reveal Earth's History

By studying the exposed layers of rock in a canyon wall, experts can learn about how the climate changed, what kind of organisms were alive at certain times, and perhaps even how the canyon may change in the future.

The oldest rocks exposed in the canyon are ancient, 1,840 million years old. Conversely, the canyon itself is geologically young, having been carved in the last 6 million years.

Geologists call the process of canyon formation downcutting. Downcutting occurs as a river carves out a canyon or valley, cutting down into the earth and eroding rock. Downcutting happens during flooding. When large amounts of water are moved through a river channel, large rocks, and boulders are carried too.

Answer 2

When scientists talk about the canyon walls as a timeline, they mean that the layers of rock in the Grand Canyon were created over millions of years and each one gives a glimpse into the past of the Earth. So if you were to climb down to the bottom of the canyon and check out the layers, you'd be looking at a timeline that goes back millions of years. Each layer of rock tells its own story about the conditions and creatures that were present at the time it was formed. For example, there might be fossils of ancient sea creatures, which shows that the area used to be covered by a sea. Or there could be sandstone or sedimentary rocks, which suggests that it was once a desert or a riverbed. So basically, scientists are saying that the canyon walls are like a book with pages full of stories about the Earth's past.