Vancouver: A retreating glacier in a remote British Columbia valley caused a massive landslide that crested a 100-metre-tall tsunami, wiped out kilometres of salmon habitat and was detected as far away as Australia, a study says. The landslide on Nov. 28, 2020, sent 18 million cubic metres of rock cascading down the side of a mountain, uprooting trees and displacing soil before crashing into Elliot Creek, said the study published in Geophysical Research Letters.
Earthquake sensors at stations around the world including in Germany, Japan and Australia detected the landslide, the study said. The slide destroyed salmon-spawning habitat over 8.5 kilometres of the creek and sent a plume of mud and organic matter more than 60 kilometres into Bute Inlet, about 150 kilometres from Vancouver, it said. At the same time as the slide, a professor at Columbia University in New York measured a magnitude-5 earthquake in that area. Marten Geertsema, lead author of the paper and adjunct professor at University of Northern British Columbia, said although the landslide wasn’t the largest in Canada, it was “very, very enormous.’’ “Imagine a landslide with a mass equal to all of the automobiles in Canada travelling with a velocity of about 140 kilometres an hour when it runs into a large lake,’’ he said in an interview.
Geertsema said when the massive slide fell into a lake below, most of the water was drained and forced down a 10-kilometre-long channel, causing widespread erosion and loss of salmon habitat. It removed about four million cubic metres of material from the creek within 10 minutes, something that would have taken thousands of years if the stream continued to flow normally, he said.
By Hina Alam
The Canadian Press