If you're traveling on Glacier National Park's Going-to-the-Sun Road, you can't miss the stunning aftermath of an atomic avalanche that occurred in January.

"I think this was the largest slide I've ever seen," said Mark Dundas, an avalanche technician who works for the park and has walked the avalanche path from top to bottom.

The avalanche likely was triggered by a Jan. 8 rainstorm, starting along the Continental Divide in the steep cliffs known as the Garden Wall. It gained enough force to keep on going even after it hit a relatively flat, half-mile long area, Dundas said.

It barreled across Sun Road above the Loop, then swarmed through the saddles on either side of a knobby hillside. It hurtled across Sun Road a second time below the Loop and carried on to the Packers Roost Road - nearly reaching Upper McDonald Creek.

The slide traveled two linear miles and more than 3,800 vertical feet, Dundas said. Based on its destructive power and the amount of debris it carried, it was easily the highest rating for avalanches, Class 5.

"That's the max," Dundas said. "It would have been amazing to see it happen."

But no one did.

The debris field was first encountered by park plow crews working on clearing Sun Road.

"We couldn't really tell where the road was," said Dundas, who works closely with the crews. The lower portion of road was buried by 15 to 20 feet of debris - a mixture of boulders, trees of all sizes and heavy snow.

"Thousands of trees were destroyed in this avalanche, literally thousands," Dundas said.

The breadth of the avalanche along the lower Sun Road was about 500 feet. But on the periphery of that path, more trees were knocked to the ground by a powerful air blast.

The largest comparable avalanche to occur in the area was a slide that killed two snowmobilers at Red Meadow Lake in the North Fork Flathead drainage in January 2006.

"That was big," Dundas said, "but this was bigger."

Reporter Jim Mann may be reached at 758-4407 or by e-mail at jmann@dailyinterlake.com