Denali National Park mudslide

A large mudslide closed the road inside Denali National Park and Preserve on Saturday, July 30, 2016, stranding some people on the west side of the park. The slide occurred at milepost 67 of the road, a mile beyond the Eielson Visitor Center. Crews were still working Sunday afternoon to open the road.

FAIRBANKS - Mud and ash from an ancient volcanic eruption oozed down a slope at Denali National Park and Preserve over the weekend, blocking the park road and leaving an unknown number of guests and National Park Service employees marooned overnight during the park’s busy visitor season.

Park Service spokeswoman Lynn McAloon said the mudslide at 67 Mile Denali Park Road closed the road about a mile beyond the Eielson Visitor Center. The 92-mile park road ends deep in the park at Kantishna.

The mudslide was discovered early Saturday and is estimated to be 100 feet wide and 10 feet deep. No one was hurt in the slide, according to the Park Service. It’s not clear if anyone witnessed the slide, McAloon said.

“The whole contributing factor has been all of the rain we have had,” she said. “These are super-saturated soils.”

Park Service employees are working around the clock to try to clear the road, and equipment was being brought in from Anchorage. Park rangers, equipment operators and geologists responded to the scene.

The slide remained active on Sunday, McAloon said.

“There is continuing ooze,” she said.

Kantishna Air Taxi flew an unknown number of people from the west side of the slide to the entrance area of the park on Saturday. Four buses were allowed to pass through the slide area, heading toward the park entrance, on Sunday.

The road otherwise remained closed at Mile 67 and is expected to be closed today but for two brief openings at 8 a.m. and 6 p.m. to accommodate scheduled bus traffic.

McAloon said that anyone delayed by the mudslide and who wanted to get to the other side was able to do so by Sunday evening.

“Everybody is out if they wanted to be,” she said. “There is nobody trapped out there anymore.”

At least two smaller mudslides have blocked the park road this summer. McAloon said this is the largest slide by far and is made up of a fine-grain ancient volcanic ash, making the mud particularly slick.

“We have seen small amounts of debris come down that slope before, but nothing even remotely close to this,” she said.

On July 15, a slide occurred at milepost 51.5 of the park road, between the Polychrome Overlook and the Toklat Rest Stop. Crews were able to open the road to one lane by the next morning.

In October 2013, a slide covered a 200-foot section of the park road near milepost 37 toward 3,900-foot Sable Pass, one of the steepest sections of the road.

The road had already been closed for the winter when the 2013 landslide occurred and nobody was injured, but 30,000 cubic feet of frozen debris had to be moved.

McAloon said 6 inches of rain has fallen over the park in the last week with more than an inch and a half coming down on Friday.

No flooding has been reported, and the Kantishna airstrip remains open, according to a statement from the Park Service.

Forecasters are predicting a chance of rain today at the park, which is visited by more than half a million people annually.

Contact staff writer Amanda Bohman at 459-7587. Follow her on Twitter: @FDNMborough.