Yellowstone, petrified watermelon, rock art: These 15,000-year-old rocks tell Idaho’s past

As Nichole Schwend weaves through the basalt rocks that litter Celebration Park, she points to faint engravings on the dark desert rocks and asks visitors what they see.

One carving near the Celebration Park Visitor’s Center looks like a circle with two rectangles on top of it.

Schwend, director of Canyon County Parks, Cultural and Natural Resources, says she thinks it looks like an owl. Other people say a rabbit. Some younger visitors say it looks like Mr. Krabs from SpongeBob SquarePants.

In all truthfulness, nobody truly knows what the rock carving means. But it’s just one of the thousands that line the Snake River Canyon in southern Idaho; hundreds of engravings exist in Celebration Park, just 40 miles south of Boise, alone.

They’re called petroglyphs, and they’ve existed in Idaho for as many as 12,000 years.

“These petroglyphs here would have been linked to the Shoshone-Bannock and the Northern Paiute people that inhabited southern Idaho,” Schwend told the Idaho Statesman in an interview in August.

“We’re looking at this as being an area that is inhabited on and off throughout history for back to 10,000 years,” Schwend continued. “The x-ray fluorescence studies they just did showed that some of these petroglyphs right here at the beginning of this trail are 10,000 years old, plus or minus 2,000.”

What are petroglyphs?

You may have heard of hieroglyphs before — the language system used in ancient Egypt of detailed paintings or carvings of animals and other depictions of people and daily life.

Petroglyphs differ from hieroglyphs in that a distinct language can be discerned from the latter, with each object representing a word, syllable or sound. That’s not the case with petroglyphs; there is no predictable method or pattern to translate them, meaning much of what we see today remains a mystery.

Native Americans created the petroglyphs by taking a hard-to-break-down rock, usually quartzite, and pecking away at the softer basalt rocks. Pecking is the process of using the harder stone to chip away at a softer rock to create art and carvings.

Some petroglyphs at Celebration Park can be identified, such as those that look like a man or a lizard; these are called representational petroglyphs. But for every representational petroglyph, there are ten abstract petroglyphs: carvings that offer no discernible rhyme or reason.

Some look just like wiggly lines. One looks like a figure eight. Elsewhere a group of petroglyphs, known as a panel, include several triangular shapes created by carving one small circle at the top, two circles in a line below that, followed by rows of three and four.

Then there is a star shape that lines up perfectly with the sun during the winter solstice.

These types of petroglyphs are called abstract, which can further be broken down into rectilinear petroglyphs, which are the ones that look like lines and corners.

Some tribes prefer to call the petroglyphs “rock writing,” Schwend said, and she’s starting to incorporate that term into her tours.

“We definitely don’t want to speak on behalf of the tribes,” Schwend said. “We just bring attention to there are terms that describe things in ways that make sense.”

Many of the petroglyphs are just as much of a mystery to members of the Shoshone-Bannock and Paiute tribes today, but they retain some understanding of what was depicted by their ancestors.

Dorena Martineau, the cultural resource director for the Paiute Indian Tribe of Utah, told the Statesman that the petroglyphs were created as a way to tell stories. Martineau is the daughter of LaVan Martineau, who authored the book “The Rocks Begin to Speak” as he attempted to decipher rock writing.

“They usually tell stories of travels, of things that they’ve seen on sites; it’s like their book,” Martineau said. “Back then, things are different, so different, but it’s more like stories, tales and adventures.”

Martineau said that there are petroglyphs telling the story of when Native Americans first encountered white men on a train at Nine Mile Canyon in Utah. White men were typically depicted in rock writing as wearing cowboy hats, she said.

According to the volunteer-run project The Decolonial Atlas, one of the larger petroglyphs found along the Snake River Canyon is believed to be a map of the upper Snake River made by a pre-colonial Shoshone cartographer. The Snake and Salmon Rivers can be observed in the design, according to The Decolonial Atlas, along with depictions of buffalo, deer and other big game known to live in rich hunting land for the Shoshone.

The depictions of animals can also be interpreted based on the different features of each animal pecked into the rock.

“Like the mountain sheep, you know what a mountain depicts, you know what the meaning is behind the mountain sheep. They’re strong, they climb, they’re really sturdy on their feet,” Martineau said. “So sometimes petroglyphs will depict that, you know, they’ll have a mountain sheep track or foot or something one leg shorter, one can be longer, and that means they’re climbing.”

Petrified Watermelon

Celebration Park is littered with dark black rocks that would look more at home on a different planet in a sci-fi TV show than in the middle of the Idaho desert. But it’s these black, basalt rocks on which the petroglyphs are pecked that make Celebration Park — and much of the Snake River Canyon — so unique.

This part of the story starts 16.5 million years ago.

The Yellowstone hotspot, which now sits in northwest Wyoming and is the namesake of Yellowstone National Park, once called present-day McDermitt, Nevada, home. Over the course of millions of years, the hotspot shifted through southern Idaho due to tectonic plate movement.

Lava flows from the hotspot helped carve the giant basalt cliffs seen in southern Idaho, including Celebration Park, today. The Snake River Plain, which the Snake River runs through today, was molded by millions of years of lava flows and is often called “Idaho’s smile.”

Fast forward to about 15,000 years ago, and a second major geological event helped shape Idaho’s landscape. Today’s Salt Lake used to be much larger; back then, it was called Lake Bonneville, and it was approximately 325 miles long and 135 miles wide and stretched into southern Idaho.

About 15,000 years ago, a lava eruption diverted water from Bear Lake in southeast Idaho into Lake Bonneville. The water level of Lake Bonneville rose as a result and caused erosion of a soft sediment layer near modern-day Preston, Idaho, causing water to flood into the Snake River Canyon.

“As this lake is draining, they figure about the equivalent of Lake Michigan drained in six weeks,” Schwend said.

The rush of water into the valley ripped chunks of basalt off the cliffs and swept these newly formed boulders down the valley, helping create the Snake River and lining it from top to bottom with basalt rocks.

Many of the rocks were around the size of watermelons, and they finally earned a name following World World 2 courtesy of Farris Lind, the founder of Stinker Stores service stations. Lind was looking for a way to beat out his competitors and did this by creating over one hundred somewhat controversial highway signs.

One of the more tame ones was in a field of lava rock just outside Idaho Falls that read “Petrified watermelon. Take one home to your mother-in-law.”

“It was this hilarious sign that linked to the Bonneville Flood and this type of gravel,” Schwend said. “And so because of that, geologists have officially named this stuff the Bonneville Flood melon gravel.”

Preserving and educating

One day there most likely won’t be any petroglyphs left, at least in their natural location. The basalt rocks are susceptible to erosion due to the desert sand or could crack if a rock suffers from frost heaving in the winter.

Shifting sands could also cover the rocks entirely at some point. Alternately, shifting sands could uncover new stones underneath the surface. But it’s not a guarantee. Fortunately, because the petroglyphs are three-dimensional, they last longer than if they were painted onto the stones, known as pictographs.

The best preservationists can do for now, aside from taking the stones out of their natural location, is to prevent people from stepping and touching them.

“They’ve been here for 10,000 years. We don’t want to be the ones that erase that,” Schwend said. “So not touching them, not walking on the rock, certainly not trying to make your own petroglyphs. Those are never great ideas. Don’t try to steal the petroglyphs; treat it as a sacred place.”

It’s not just physical destruction and the sands of time that have resulted in the loss of petroglyphs and their understanding. Martineau says that the forced removal of Native American children from their families into boarding schools also contributed to losing knowledge of Native American history.

“A lot of our kids, as you know, were sent away in boarding schools, and we were forbidden to speak our languages, so we kind of lost some of those things,” Martineau said. “I’m sure there are a few that still understand and know what some of these mean. But it’s beginning to get lost.”

Visitors can view the petroglyphs anytime, but guided tours are available starting at the visitor’s center from 10 a.m. to 2 p.m. Tour guides will educate visitors on the history of the petroglyphs, as well as the Native Americans who once lived there, who primarily lived along the Snake River in the winter months due to milder weather.

The Shoshone-Bannock tribal land is now at the Fort Hall Reservation in southeastern Idaho, while the Northern Paiute now primarily live throughout California, Nevada, Oregon and Idaho.

Much of the education is taught from an archaeological perspective, Schwend said, but they attempt to remain respectful of Native American beliefs.

“This is speaking from an archaeologist’s point of view,” Schwend said. “Many of the tribes will tell you (the petroglyphs) have been here for all time, and it wasn’t because of the flood. They’ve always been here. We try to be really respectful of that.”

“We are an archaeology park; we try to stick to the facts,” Schwend continued. “We’re not trying to say what they meant spiritually or any of that. We’re just trying to speak to the science end of it.”