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45 megatons of rock and ice tumbled down the southeast flank of Mount Steele.

Scientists detect giant Yukon avalanche in early October

Katie Jones
Digital Reporter

Saturday, October 31, 2015, 6:07 PM - Two scientists from Columbia University have detected a massive avalanche on one of Canada's highest mountains -- that otherwise would have gone completely unnoticed in a remote part of northwestern Canada.

On October 11, five megatons of rock and ice came crashing down the southeast face of Mount Steele in southwestern Yukon Territory. The amount of debris that fell is equivalent to the weight of about 700 aircraft carriers.

Colin Stark and Goram Ekstrom of Columbia University discovered the huge landslide using advanced software and earthquake sensors that monitor seismic waves. Seismic waves are vibrations that radiate through Earth’s crust because of sudden movements of rock, ice, magma, or surface debris.

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Two days later, Stark and Ekstrom were able to confirm the slide with satellite imagery showing scenes of the aftermath and long path of debris. The glacier that surrounds Mount Steele contributed to the length of the debris field, as tumbling rocks and ice went flying across the slick icy surface at speeds of up to 30 metres per second.

Though rumblings from the giant slide registered on seismic monitoring systems, there is no evidence that suggests an earthquake triggered the event.

"Very large landslides like this often have very ambiguous triggers,” said Stark. “Failure takes place because of a long-term accumulation of stress within the rock slope and a long-term weakening of the rock. A hair-trigger is often all that is needed.”

Avalanches on Mount Steele are not uncommon. In 2007, an avalanche that began on Mount Steele dumped more than 100 megatons of debris on Steele Glacier. The debris pile from that landslide is still visible beneath the snow a few kilometers to the northwest of the the debris from this month's slide.

Since 2013, Stark and Ekström have detected and identified ten landslides using a combination of seismic signals and satellite imagery that have been large enough to dump more than 15 megatons of debris. 

While the 2015 Mount Steele landslide was large for a rock avalanche, much larger events have occurred. Scientists have observed massive landslides in Kashmir and Tibet transporting as much as 440 megatons and 550 megatons of debris.

Mount Steele is located among the Silas Mountains in an uninhabited region of the Canadian territory, and is the fifth highest mountain in the country.

Source: NASA Earth Observatory

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