First, what’s the difference between petroglyphs and pictographs? Petroglyphs are chipped or scratched into a rock’s surface. Pictographs are painted onto a stone surface using natural dyes and pigments. One handy way to confuse yourself when remembering what the difference is is to remember the “pic” in pictograph should mean that someone “picked” the image into the rock, except that it doesn’t. Helpful? No? That’s just the way my mind works.
Now that you’re about to quit reading because your brain hurts, let me assure you that a public service announcement is coming up. Please stand by.
Famous sites for petroglyphs and pictographs in Idaho include Hells Canyon, the Middle Fork of the Salmon, and numerous sites along the Snake River. If you’d like to see some terrific examples and learn more, visit Celebration Park near Nampa.
I’ve mentioned before that interpreting what is sometimes called “rock writing” is not an exact science. That’s because it’s not really writing. The indigenous people of what is now Idaho did not have a handy alphabet they could use to get their message across. The representations carved into or painted on rock often deviated with the artist. Still, they probably were trying to depict what they saw or tell some kind of story. Maybe you can figure out what they were trying to say. If only there was a way to make the images a little clearer. Hey! What if we traced on top of them with chalk so they would show up better in a photo?
And, here comes the PSA. Don’t do that. It’s illegal in many places and problematic everywhere. It used to be a standard practice, but scientists have learned that chalk dust can bake into the rock over the years helping to obliterate the rock art. It is especially damaging to pictographs, potentially destroying the dyes used to create them and leaving calcium behind in concentrations high enough to make them impossible to carbon date.
Another issue with chalking is that it shows the bias of the chalker. They trace what they “see.” The rock art is often faded so interpretation is sometimes dicey. In one famous example chalking the rock art in a Utah cave created the belief that the indigenous artist was depicting a winged monster, maybe even a pterosaur. That excited people who were eager to prove that dinosaurs and humans existed at the same time.
In 2015, scientists used a portable x-ray florescence device to bring out the original detail on the “winged monster.” It turned out that the rock art was originally a depiction of a couple of four-legged animals, maybe a sheep and a dog.
We humans are very good at identifying figures in clouds and wallpaper stains as various objects, animals, and people. That tendency is called pareidolia. And now I regret that I didn’t use that word in my alliterative first sentence. But, back to that Utah cave. When someone chalked those two critters, they “saw” variations in the color of the rock combined with the rock art that looked like a winged beast. Subsequent chalkers “saw” the same thing because of the original chalker’s pareidolia.
So, no chalking, please. It’s too bad, though. Look how well the rock art shows up in this picture of Map Rock near Murphy. That’s Robert Limbert in the white shirt on the right taking notes. We don’t know who the other two people are, perhaps because Limbert didn’t make note of that. The picture is courtesy of Boise State University Library, Special Collections and Archives.