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Saturday, October 31, 2015

Enormous, ‘catastrophic’ landslide in northern Canada almost went undetected by humans 10-31

It was enough rock and ice to equal the weight of 33 million pickup trucks. And for an earth-shattering two minutes, it barrelled down a mountain at nearly 200 km/h, pulverizing everything in its path.

And the Yukon didn’t even know it was there.

“Most likely it would have been missed,” said Colin Stark, one of two Columbia University geologists who spotted the “catastrophic” event from more than 5,000 kilometres away.

Expected to rank among the world’s 10 largest landslides for 2015, the slide saw a massive chuck of rock and ice slough off Mount Steele, Canada’s fifth highest peak.

If the Oct. 11 slide had struck in a populated region of India or China, hundreds would be dead. Even in Canada’s sparsely populated Rocky Mountains, it would have at least blocked a highway or buried a wilderness lodge.

But it occurred in a remote corner of Kluane National Park, Canada’s Wales-sized contribution to a swath of protected land stretching all the way to Anchorage, Alaska.


“That particular area, as the crow flies, is about 70 kilometres to the Alaska Highway; people aren’t back there very often,” said Jeff Bond with the Yukon Geological Survey.

Quite often, said Bond, the only way remote Yukon landslides are recorded is if some bystander happens to phone it in.

“We hear about them from helicopter pilots who say, ‘hey, did you guys know about this big slide?’ ”
In the summer of 2014, for instance, a landslide plowed into a creek within Kluane National Park, violently creating Canada’s newest lake. But it wasn’t until six months later that the change happened to be spotted by an off-duty parks employee who was out for a hike.

Credit for discovering the Oct. 11 avalanche falls to Stark and his research partner, Göran Ekström.
Operating out of Columbia University’s Department of Earth and Environmental Sciences, they have pioneered a way of discovering landslides by sifting through data typically used to detect earthquakes.

In the case of Mount Steele, one of the few witnesses to more than 45 megatons of falling rock and ice was “YUK8,” an unmanned Canadian seismic monitoring station located only 25 kilometres away.

Confirmation then came in via Landsat 8, a NASA Earth-monitoring satellite that focused in on the remote mountain and noted that vast areas of the surrounding peaks and glaciers had been blackened by debris.

Jsayre64/Wikipedia Commons

“The fact that the debris fell on ice contributed to the long debris field,” NASA wrote in a subsequent post.

Named for Sam Steele, the Yukon’s indomitable top Mountie during the Klondike Gold Rush, Mount Steele has proved to be surprisingly delicate of late.

In 2007, the mountain first found its way into geology textbooks with a slide that buried an area larger than Vancouver’s Stanley Park, and shook the ground with the force of a 5.2 earthquake.
That time, the only witnesses were a research team led by glaciologist Garry Clarke, who just happened to be nearby when they heard the distinctive roar of a mountain falling over.
“They got dusted by the ice avalanche, actually,” Bond said.

Mount Steele is part of the Saint Elias Mountains, which includes Canada’s highest peak, Mount Logan. Amid regular earthquakes and landslides, it’s also a good candidate for Canada’s most geologically interesting corners.

Just last year, in fact, a mountain face broke off nearby Mount La Perouse, in Alaska, creating one of North America’s largest known natural landslides.

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