January 25, 2021

BC Landslides in the far reaches of the coast trigger massive debris layers

BC, a large landslide north of the Campbell River dumped about 7.7 million cubic meters of debris into a sea inlet, transforming much of the coastal landscape.

Scientists say the magnitude of the event was equivalent to a magnitude 4.9 earthquake – one-sixth of Canada’s largest in 1965.

In January 1965 BC, the so-called Hope Slide near Hope was one of the largest in Canadian history, sending 47 million cubic meters of rock, mud and debris across Highway 3.

But last month the slide for Butte Inlet went unnoticed for weeks because it was in a remote area.

Scientists say the initial landslide occurred in the coastal mountains 110 kilometers northeast of the Campbell River, where a steep slope went up and sent debris into the swollen glacier lake.

Dec. (Bastian Fleury / 49 Northern Helicopters)

Geologists and seismologists believe that the early slide referred to them as the “eruption flood”, which occurred on November 28 at 6 p.m.

‘Layer of Dangers’

Daniel Sugar, an associate professor in the Department of Earth Sciences at the University of Calgary, said: “I’m excited about this.

“It’s very interesting risks or domino series of events. A landslide triggered a displacement wave – like a tsunami on a lake – which was lowered via the moraine. [a debris accumulation] It shut off the lake to cause this explosive flood and then this turbulent current in the sea. “

Sugar suspects that heavy rain caused the initial collapse of the slope, which had previously shown instability. The sudden eruption of water from the lake triggered millions of cubic meters of soil and debris and discharged Elliott Creek into a valley.

“The boulders, which are almost like wet concrete, will carry the boulders and wash over Elliott Creek and then the Southgate River, and the trees will be uprooted and placed in the Butte Inlet,” Sugar said.

Take a look | FExhaust from the helicopter pilot’s camera that detects the size of the debris field:

Helicopter pilot Bastian Fleury flew into the Southgate River on December 10, 2020, to investigate why trees and logs float to the nearby Butte Inlet. The pilot found evidence of a large landslide carved into a creek bed. 0:52

It was a rainy winter, and reverse inlet residents were evacuated in late October for fear of landslides. But, with the exception of the odd lodge, this slide is rarely near people, especially in the winter.

The curious helicopter pilot discovered the magnitude of the landslide

On December 10, as logs and trees were floating in the Butte Inlet, a helicopter pilot decided to fly over a remote area near the Southgate River – about 15 minutes from the Campbell River – to search for the source of the destruction, first the Southgate River, then the creek.

Bastian Fleury of 49 Northern Helicopters flew for a decade, so he saw some slides. But there is no such thing.

“It’s a weird site. I’ve seen landslides, but it’s a big, big one. We know something big happened,” he said.

Flori could not fly far enough to find the source because the weather was dangerous and the visibility was not high.

But he suspected that it was somehow related to the glacial lakes provided by Homatko Icefield, which is the largest in the southern part of the coastal mountains.

In Flori’s scenes, when the helicopter flies with the former creek bed, it becomes clear that whatever power comes from the mountain, it is powerful. The shallow creek bed has been transformed into a steeply sloping valley. In other photos across the river, the odd islands of spiral trees are in danger as a muddy river continues to flow.

“It’s so crazy,” Fleury said, looking forward to flying farther to see the starting site where the slope collapsed while the weather cooperated.

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