Petroglyphs are images etched into stone. They’re created by carving away the darker top layer of the rock face, called patina, to reveal a lighter surface underneath. And they can offer clues to centuries of environmental change.
In the Southwest, many petroglyphs express the viewpoint of ancestral Puebloan people who thrived in the region from around 300 to 1300 BCE.
It’s difficult to date petroglyphs, and archaeologists sometimes rely on surrounding pottery or other markers to age the creations. They may have marked significant cultural events or simply reflected human experience. Regardless of their original intent, petroglyphs offer a record of past climate changes within the Southwest.
For example, Newspaper Rock, in Southeast Utah, boasts depictions of clan symbols, plants and animals, and other unknown expressions left to individual interpretation. Petroglyphs at this site are 2,000 years old and document numerous climate and cultural changes. Some depict aquatic animals such as frogs, turtles, and fish that are no longer found in the area because it’s become hotter and drier. The artists who made the carvings may have been witnesses to a very different climate.
In addition, petroglyphs found at higher elevations might have been carved at a time when there were nearby sand dunes or rocks to climb. As flooding and erosion re-shaped the area, such climbing aids disappeared, making higher elevations unreachable.
Like pages in a book, petroglyphs can be pieced together to communicate the story of those who lived centuries ago.
This Earth Note was written by Darrien Benally and produced by KNAU and the Sustainable Communities Program at Northern Arizona University.
