The Grand Canyon was carved out of rock by the Colorado River over millions of years. The strata of the canyon is discussed to explain what the layers tell us about how the canyon formed.

According to a new study published in Proceedings of the National Academy of Sciences, an estimated five kilometers (3 miles) of rock strata ... Recent photograph of Grand Canyon from Walhalla ...

Something dramatic happened about 500 million years ago called the Cambrian "explosion," during which an incredible diversity of life forms became preserved in the rock record. These fossils ...