Questions linger over Mount Steele's slide

A massive avalanche that shook Canada's fifth-tallest mountain this summer still has scientists talking, not just about what caused it but also the implications it could have on the Yukon's mining industry.

Geologists are continuing their research into how a huge slab of ice came off Mount Steele, a 5,067-metre peak located in the Yukon's Kluane mountain range, triggering massive snow avalanches and rockslides.

Speaking in Whitehorse to mining industry delegates Tuesday at the 35th annual Yukon Geoscience Forum, Yukon government geologist Panya Lipovsky said the Mount Steele slides were amongthe largest on record in Canada.

"It was one of the largest events ever documented in the Canadian Cordillera, so there was quite a bit of interest by the public and scientists across the country," Lipovsky said Tuesday. "We've been looking at it ever since."

On July 22, a 400-metre chunk of ice and rock fell off the mountain's north slope, triggering an enormous avalanche of snow and, two days later,an even larger rockslide. The event shook the earth with a force equivalent to an earthquake with a magnitude of up to 5.6, Lipovsky said.

She said centuries of high seismic activity in the area, changing temperatures and physical weathering may have weakened a glacier that normally acts as a foothold for the surrounding rock and ice.

"Climate has a large influence on permafrost temperatures and thermal contraction and expansion of the rocks," she said.

"The climate in that part of the world has been warming since the end of the Little Ice Age. During that period, air temperatures have risen, permafrost temperatures have probably risen, and freeze-thaw cycles may have changed. But at this point, we don't really have enough data to be conclusive about that."

Although mining companies are not likely to be digging for minerals in the rugged terrain that surrounds Mount Steele, Mike Burke of the Yukon Geological Survey said research by Lipovsky and others can be valuable to the industry.

"Say you find a deposit off in the middle of somewhere and you have to build a road to it," he said. "Climate change, permafrost changes all those sort of things are going to impact your infrastructure. That impacts your costs."

Lipovsky warned that similar slides are possible in the territory, and researchers are trying to learn as much as they can about what happened on Mount Steele so they can apply it to other cases. They are currently focusing efforts on modelling similar rock slides, she said.