Rangers at Utah's Arches National Park were investigating large graffiti Thursday that was carved so deeply into a famous red rock arch that it might be impossible to erase, officials said.

The carvings discovered earlier this month measure about 4 feet across and 3 feet high, park Superintendent Kate Cannon said.

The vandalism is part of a "tidal wave of graffiti" at Arches and other national parks in recent years, she said.

Two years ago, at least eight national parks in the West began the delicate task of cleaning up graffiti-like paintings left on famous, picturesque landscapes. The damage was discovered after images were shared on social media.

The Arches rock formation, commonly known as Frame Arch, is off a popular hiking trail where visitors can look through it and view the park's iconic, stand-alone Delicate Arch.

Cannon said the graffiti was etched so deeply that it might have taken at least an hour for someone to carve.

She said park workers can try to reduce the carving's visibility by grinding down the rock around it, but that causes further damage to the surface. She said they could also try to fill in the etchings with some kind of material that blends in, but it's unclear if that would be a permanent or unnoticeable treatment.

Defacing surfaces in the park is illegal and anyone caught can face up to six months in jail and a $5,000 fine.

Social media seems to be a driver of increased vandalism, but Cannon said graffiti generally has become inexplicably popular among visitors.

"It is really overwhelming," she said.

Officials hope public outrage and vigilance can ease the problem.

"We take great pains to be out in the park and around where people are," Cannon said of park ranger patrols. "Unfortunately, we can't be everywhere all the time."