Ancient Red Rocks

The red cliffs in and around the park belong to the Red Peak Formation, part of the Chugwater Group, a fine-grained sandstone outcrop up to 600 feet thick whose brick red color comes from oxidation of iron minerals in the rock. Some historians believe the name Chugwater comes from a Native American story about a bison hunt in which hunters drove the animals over a cliff into the stream below, known as "water at the place where the buffalo chug." The Red Peak Formation was deposited about 250 million years ago during a desolate period in Earth's history just before the Triassic period, when a catastrophic event caused the extinction of more than 90 percent of Earth's life. Most of the formation, beginning at its base, is completely void of fossils, marking the aftermath of this mass extinction. Two to three million years later, life was beginning to reintroduce itself, and near the top of the formation vertebrate tracks and other fossilized traces of life were found, including some of the oldest known vertebrate tracks and traces, among them ones that resemble a turtle-like reptile called Chelonipus.

Thermopolis, Wyoming · United States