The hike was steep, but Chris Rost promised it would be worthwhile.

Weekends often find this 48-year-old physician’s assistant in Glacier National Park, hiking, skiing, climbing and volunteering. But last Sunday, he took a small group beneath the park’s postcard scenery.

Montana has almost 300 known caves and caverns, and Rost belongs to a group, the Northern Rocky Mountain Grotto, that aims to make sure they’re explored safely and responsibly.

“First rule of cave club: We don’t disclose exact locations of caves,” he posted on activity-planning site Meetup before the trip. This was “so we can protect the caves (they are fragile environments) from the masses.”

During the two-hour drive from Columbia Falls, Rost told his passengers — Daniel Foust, Lindsey Battle, Allison MacFarlane and myself ­­— about the damage “the masses” can inflict underground. One popular spot, Lick Creek Cave in Lewis and Clark National Forest became choked with trash and graffiti.

It’s since been improved, thanks to cleanups and increased surveillance, but other threats remain. White Nose Syndrome, a fungal disease, had hitchhiked from cave to cave on explorers’ unwashed gear, killing an estimated 6 million U.S. bats since 2006.

Last Sunday’s destination, two hours from the nearest road, seemed well-hidden enough to escape harm. “If this cave were a mile hike, it’d be inundated with visitors,” Rost surmised. But a small plaque and horseshoe at the entrance confirmed that cavers had found it worth a visit.

It didn’t seem so at first. The entrance passage ­— less than 2 feet high — felt like crawling up the mountain’s intestines, with a dead packrat supplying the smell. That was the worst part, Rost said, once the group emerged from the squeeze into a dome-shaped room.

Sure enough, the wrinkled tunnels widened. White and yellow crystals covered some spots like hives. The deeper passages had been carved by a stream, clear enough to be nearly invisible, and old enough to have worn through 7 feet of rippled, inch-high limestone layers. Its source: a waterfall, gushing from a gap high above head level, in the wall of a tight but high-ceilinged chamber.

Foust, a Whitefish-based artist, climbed the opposite wall for a better look. The rest huddled on a ledge, getting spritzed by the waterfall and staring into the darkness above them.

Rost hopes that even better caves have yet to be found.

“People are out just beating the bush, walking the ridgelines, looking to find things,” he said on the drive home, talking about the “grotto’s” work. “We’re getting leads all the time, and we need to get out and explore these things.”

Doing so, he continued, is as much for the caves’ good as it is for cavers’.

“One of the ways you protect a cave is [that] you discover it, and you map it.”

According to the National Parks Service, construction above caves can disrupt the slow, steady dance of water and stone that nurtures caves.

“If you don’t know a cave exists, and someone wants to build a road [there]...all of a sudden you’ve got equipment that’s damaging the ground below it and ruining structures inside a cave that have been developed for tens of millions of years,” Rost said.

As he’s has seen firsthand, humans can cause even worse damage when they actually enter a cave. The risks of contamination make him reluctant to share caves’ exact location.

“In order to do it in a positive manner,” he said, “you really have to be educated, and you have to be safe.”

To this end, he encourages would-be cavers to join the Northern Rocky Mountain Grotto, which works to survey and protect the caves its members visit.

“We want to promote caving, preservation, conservation, as well as recreation [and] having fun, because we definitely enjoy it.”

Chris Rost organizes treks into Glacier using Meetup.com. His group is called “All Things Glacier.”

Reporter Patrick Reilly can be reached at preilly@dailyinterlake.com or 758-4407.