The landslide on November 28, 2020, caused 18 million cubic meters of rock to fall on a mountain slope, uprooting trees and displacing soil before falling into Elliot Creek, according to a study published in Geophysical Research Letters. Earthquake sensors at stations around the world, including Germany, Japan and Australia, detected the landslide, the study said. The slide destroyed the salmon breeding habitat 8.5 miles[8.5 km]in the creek and sent a pile of mud and organic matter more than 60 miles to Bute Inlet, about 150 miles from Vancouver, he said. At the same time as the slide, a professor at Columbia University in New York measured a magnitude 5 earthquake in the area. Marten Geertsema, lead author of the paper and assistant professor at the University of Northern British Columbia, said that although the landslide was not the largest in Canada, it was “very, very huge”. “Imagine a landslide with a mass equal to all the cars in Canada traveling at a speed of about 140 kilometers per hour when it falls into a large lake,” he said in an interview. Geertsema said that when the huge slide fell into a lake below, most of the water drained and was forced to descend into a 10-kilometer canal, causing extensive erosion and loss of salmon habitat. It removed about four million cubic meters of material from the creek in 10 minutes, which would take thousands of years if the stream continued to flow normally, he said. Professor Brian Menounos, Canada President of Glacier Change Research at the University of Northern British Columbia, said many factors came together to cause slope instability and landslides. “What we do not know is whether the last straw that broke the camel’s back, in the absence of a better phrase, was a storm or unusually wet conditions during 2020,” he said. What scientists know, he said, is that the glaciers that once covered and held the slopes are melting at a rapid rate due to man-made climate change, leaving the sides of the mountains loose and exposed. Geertsema said the biggest impact of the landslide was on the fishing grounds. Homalco First Nation contributed to the research and its members co-authored the study, which was released last month, bringing their knowledge of Elliot Creek salmon habitat, he said. Menounos said landslides are not uncommon and have plagued continents for millennia, including the creation or diversion of bodies of water and rivers. However, defrosting is expected to accelerate landslides and, in some cases, scientists have the tools and data to better map the topography beneath glaciers, allowing them to estimate such events, including new lake formations, he said. “The ability to drain maybe half the volume of the lake in 10 minutes or less, I mean, was terribly strong and annoying,” Menounos said. “I feel very small, to study things with such force.” Our Morning and Afternoon Newsletters are compiled by Globe editors, giving you a brief overview of the day’s most important headlines. Register today.
