GRANITE FALLS — Every spring, hikers flock by the tens of thousands to Big Four Mountain to see the caves that form as snowmelt and warm air hollow out caverns.

But the attraction is unstable and a constant threat to those who wander too close. Four people have been killed at or near the caves in the past two decades.

That’s why researchers from two Texas universities worked with the U.S. Forest Service to study hikers’ risky behavior and how it might be averted.

Baylor University professors Kelli McMahan and Chris Wynveen visited the caves in the summer of 2017 to observe how visitors behaved and interviewed those who got too close. Along with Texas A&M staff, they recommended some changes to the trail.

The researchers spent four days watching visitors. They approached those who got too close to the caves and asked the red-handed hikers what it might take to keep them from climbing on or going in the ice structures.

For the most part, McMahan said visitors indicated they weren’t really sure where on the trail to stop.

“Because of the terrain, it’s not very developed,” McMahan said.

The trail technically stops at the rock field that stretches out in front of the caves.

“It’s very hard to communicate what’s the trail and what’s not,” she said. “Everything looks like the trail.”

Based on hours of these recorded interviews, the researchers came up with some techniques that may deter visitors from venturing too close.

“(The Forest Service has) done a really good job of communicating along the trail, but people need more clarity right where they want to be,” McMahan said. “They want to be in the caves, they want to feel the cold air.”

Ideally, she said the end of the trail needs to be moved. Then brush and other physical features could be used to make walking up to the caves more difficult.

“You could still see it, still enjoy it, but not interact,” McMahan said.

One method could involve renaming the end of the trail to the “viewing area” to make it clear guests aren’t meant to stray.

The researchers also recommended the forest service explore using technology to convey how dangerous the caves are. McMahan said a kiosk playing a looped video of ice cascading down the face of the caves might be effective.

But there are many technical challenges to getting power in the middle of the forest.

Posts on social media show that people continue to venture in and around the caves.

In 2010, 11-year-old Grace Tam of Marysville was struck and killed by falling ice while she was about 20 feet away from the caves on a family hike. Four years ago, a cave partially collapsed while people were inside. A woman was killed at the scene and her brother died months later of his injuries. A 27-year-old Bothell woman also was killed by falling ice in 1998 near the mouth of the caves.

Ashley Ross of the Darrington District said the Forest Service is looking at a complete redesign of the Big Four Ice Caves trail. Ross said they’d like to make the trail a loop to keep folks moving, and to add more signage.

But funding for such a project could be about five years down the road, she said.

The agency plans to work with the National Forest Foundation to pay for the changes.

Julia-Grace Sanders: 425-339-3439; jgsanders@heraldnet.com.