Pictograph Cave State Park managers say erosion and human intervention past and present threaten what remains of more than one hundred pictographs at the National Historic Landmark. Analysis suggests paintings date back hundreds and thousands of years.
Historically, archaeologists who excavated the site changed it by displacing soil and removing the original floor, among other alterations. And in the mid-1990s, analysis found a stock pond above the shelter could have contributed to water exposure and erosion of the paintings.
Park managers say interventions like those can worsen the natural erosion and weathering that already contributes to the gradual and inevitable loss of the pictographs.
Montana Fish Wildlife and Parks Heritage Specialist Brenna Moloney says some pictographs are visible solely when the walls are wet. When the walls are dry, only a few of the brightest pop out in red.
On one sunny weekday morning in September, Moloney points up at a row of fading red lines on the walls of Pictograph Cave: “To the right of the rifles there, there’s shield warriors, there’s depictions of the hunt.”
Over the next two years, $75,000 in National Park Service funding will go towards hiring a geotechnical engineer and planning for ways to protect this space. It’s one of three cave-like shelters carved into a towering sandstone bluff just outside of Billings.
Major rockfalls occurred at Pictograph Cave State Park in both 2021 and 2014. No one was harmed. But the soft rock is crumbling and the paintings along with it.
Moloney says some pictographs fall and shatter on the floor, but site managers are able to pick up and preserve others, like a turtle upwards of 2,000 years old now on display at the park visitor center.
“Eagle Sandstone is constantly shifting, eroding, and changing,” says Moloney. “It’s a natural process, and we’re going to lose them eventually, but we want to mitigate human causes to that, that might be accelerating that process and also just keep people safe when they come to visit this place.”
Moloney says FWP will produce an assessment and site plan with the grant award, and move on to implementation at a later date.