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Massive landslide on B.C.’s central coast created its own seismic event: geologist

Click to play video 'Landslide on remote B.C. inlet does massive damage' Landslide on remote B.C. inlet does massive damage
The huge landslide that tore down remote Bute Inlet in late November is believed to have created a wave as tall as 110 meters, and did massive damage to the area's salmon spawning habitat. Ted Chernecki reports – Dec 15, 2020

A massive landslide that happened in a remote inlet on B.C.’s central coast caused a shock that was equivalent to a 4.9-magnitude earthquake, experts say.

The slide occurred at 6 a.m. on Nov. 28 at Elliot Creek, just east of the head of Bute Inlet north of Powell River.

Part of the mountainside fell away and much of the debris crashed into an already swollen glacial lake, creating a wave 70 to 110 metres high.

An estimated 7.7 million cubic metres of water, mud and rock blasted downstream and roared into the inlet, forever altering some prime salmon spawning habitat.

“I think it would have wiped out the runs in Southgate (River) for this year,” Darren Blaney, chief of the Homalco First Nation, told Global News.

“It’s a strong run, so it’s going to be a big loss for our community because the chum stocks have been declining so it just knocks it back even more. Our people have been getting less and less chum for our social and ceremonial purposes.”

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Read more: Helicopter footage shows huge landslide on B.C.’s central coast

Click to play video 'Landslide causes tsunami-like wave on B.C.’s central coast' Landslide causes tsunami-like wave on B.C.’s central coast
Landslide causes tsunami-like wave on B.C.’s central coast – Dec 15, 2020

Blaney said the slide took out an 80-foot bridge that was part of a logging operation in the region, and that a cabin may have also washed away.

The Homalco First Nation operates grizzly bear tours in the area and Blaney said they are meeting with the Department of Fisheries and Oceans to learn more about how the slide impacted the area and what can be done for the bears and fish.

“The reason that we’re so focused on our hatchery and rebuilding our stocks is to protect our food security,” Blaney added.

“Because it doesn’t seem like we can rely on the stocks going by Johnson Straight anymore. We have to look deeper into our territory for our own food sources, so that’s what we’ve been working on to secure our future generations.”

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Click to play video 'Helicopter footage shows huge landslide near Bute Inlet on B.C. coast' Helicopter footage shows huge landslide near Bute Inlet on B.C. coast
Helicopter footage shows huge landslide near Bute Inlet on B.C. coast – Dec 14, 2020

Video shot from a helicopter on Sunday shows just how huge the landslide was as the debris came crashing down.

Staff at 49 North Helicopters, based in Campbell River on Vancouver Island, said they had heard about an “unusual amount of wood” floating in Bute Inlet on the weekend.

They decided to fly up the inlet to the Southgate River and saw miles of water, mud and debris.

Brent Ward, a geology professor and co-director of the Centre for National Hazards Research at Simon Fraser University, said they are still waiting for more information, but the remoteness of the site and the weather are making that task difficult.

“What the trigger was, we don’t know,” Ward said. “We know it was cold. There wasn’t a lot of rain in that area. If there was any precipitation, it was snow.”

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He confirmed there were no earthquakes in the area, but that the slide created its own seismic event.

“The concern is, say, if there was infrastructure or ships in the area, then it could have a significant effect.”