In late November, a seismic listening station in Colorado picked up a strange signal coming from the Coast Mountains north of Vancouver. It showed a 4.9 magnitude disturbance, but it was clear to seismologist Göran Ekström that this was no earthquake.
From his office at Columbia University’s Lamont Doherty Earth Observatory just north of New York City, Ekström spends his days scanning the globe for geologic disturbances in real time — including earthquakes, volcanic eruptions, the “calving” of massive icebergs from the polar ice sheets, and even secret underground nuclear tests by rogue states.
Each of these phenomena exhibit a signature as distinct as a fingerprint. That’s how Ekström could tell that the November seismic energy, relayed from Colorado to his computer, was the result of a collision involving a huge mass of sliding rock, lasting about a minute and a half. It was clear to Ekström that a landslide of phenomenal violence had happened somewhere on the B.C. coast, but no one knew exactly where.
The southern Coast Mountains are so remote, it took until Dec. 10 before a helicopter pilot accidentally stumbled across the disaster site over Bute Inlet, a massive deep water fjord ringed by high mountains and glaciers, about 110 kilometres northwest of Vancouver. He noticed the debris in the inlet first, then followed it inland to the source.
An investigation is ongoing, but here’s what we now think happened: at around 6 a.m. on Nov. 28, 18.5 million cubic metres of rock — enough to fill Vancouver’s BC Place stadium nine times — dropped off a mountain, sliding about a kilometre before it slammed into a lake at the base of a retreating glacier. The impact created a tsunami wave 100 metres high, which broke the banks of the lake and gathered momentum as it picked up rock, earth and trees, bulldozing 13 kilometres down the mountain, gouging salmon rivers and smacking into the ocean at Bute Inlet.
Scientists call such an event an “outburst flood.” The lower end of the overflowing lake fed into Elliot Creek, which delivered the surging slurry of water, silt, rocks and vegetation down the mountain and into the larger Southgate River, which empties into Bute Inlet.
Even there, the wave did not stop: the tsunami created a wide plume of mud and sediment that travelled at least 70 kilometres underwater out into the Pacific Ocean — a shock to the marine system so immense, it lowered deep water temperatures by at least half a degree Celsius. (The video below shows what happens when an outburst flood occurs.)
Hakai Institute, a Calvert Island-based scientific research and teaching centre, is now collaborating with experts from the Province of B.C., multiple universities and local First Nations to understand what triggered the collapse of the rock, and in the bigger picture, how climate change could make these kinds of phenomena more commonplace in the future.
The disaster at Bute Inlet is also adding a new sense of urgency to climate research already underway.
As reported earlier in this series, University of Northern British Columbia and Hakai Institute researcher Brian Menounos and collaborators have determined that British Columbia’s 16,000-plus mountain glaciers are melting faster than previously thought, with the prospect of losing 70 per cent of our glaciers by the end of the century. Many of our smaller mountain glaciers will completely disappear long before this time, and researchers are studying the evolving effects on ocean ecosystems their altered rhythms of water release will cause.
Every once in a while, however, those effects will be sudden and dramatic. Expect more outburst floods to transform British Columbia’s terrain with frightening power.
As the ice melts, there will be more and more high-altitude lakes like the one at Bute Inlet, along with higher amounts of precipitation as rain, all in proximity to steepened, glacier-gouged rock no longer held up by walls of glacial ice.
“If glacier retreat continues and even accelerates with climate change, then there is good reason to think we can expect to see an increase in these sorts of events,” says Menounos of the Bute Inlet disaster. “What we’re seeing is a natural process that is being exacerbated by humans.”
In terms of understanding what triggered the slide, it’s still early days — a group of investigators, led by the Province of B.C., weren't able to access the site until spring.
But work is already underway to measure the speed, length and mobility of the slide, the height of the wave, and to compare before and after satellite mapping of the site.
The tweets below reveal how the Hakai team used before and after aerial data to recreate the event.
“We’re incredibly fortunate that we had a preexisting map of the area.”— Hakai Institute (@HakaiInstitute) February 25, 2021
- @derekheathfield from @HakaiGeospatial
By comparing previously collected landscape data with maps post-slide, scientists can calculate how much material fell off the mountainside & where it ended up.
One great concern moving forward, is that as our mountain glaciers melt, there will be a growing hazard from high-altitude lakes created by the meltwater. The lake at the head of Elliot Creek at Bute Inlet was something called a moraine-dammed lake — which are common in our coastal mountains. Such a lake is created when healthy glaciers flow out of the high mountains, scouring and pushing rock and soil to the front as they advance; when the glacier melts and recedes, that leading edge of rock becomes a dam wall that holds the meltwater, creating a lake. Anyone flying over the Coast Mountains has seen these beautiful powder-blue lakes growing around glacier toes.
In other cases, glacial ice itself can dam meltwater to create water bodies, which can suddenly and catastrophically drain into a valley as the ice destabilizes and melts. (Icelanders call the release “jökulhlaup.”)
As our glaciers disappear, steep slopes of mountain rock shaped and gouged by the glacier are left behind, which can become unstable without a body of ice to support it. Such unstable rock is thought to have toppled into the lake above Elliot Creek at Bute Inlet, creating the massive wave.
Hazards also come from landslides that don’t fall into water and create tsunamis, but just barrel down from the mountains into a valley, like the big Christmas Eve 2020 landslide that occurred in B.C.’s Taku River watershed near Alaska.
John Clague, a professor at the department of earth science at Simon Fraser University and a global authority on earthquakes and landslides, says the destabilization of mountain rock from retreating glaciers, in concert with melting alpine permafrost, could cause more of these kinds of events in the future. We often think of permafrost as a northern, high-latitude phenomena, he says, but in places like the southern Coast Mountains, rock that was once permanently frozen now thaws amid lower temperatures, forcing water into the joints of the rock, ultimately destabilizing slopes as the rock refreezes and melts again and again.
“We think these two processes — [destabilizing] of slopes formerly backed by ice, and melting permafrost — are responsible for many of these landslides,” says Clague.
As climate change intensifies, scientists believe that mountain landslides will become a bigger problem all over the world. A 2018 study looking at the connection between outburst floods caused by moraine dam failure and climate change, the first of its kind, did not find an increasing incidence of these kinds of disasters in the world yet, but predicts “increased glacial lake outburst floods during the next decades and into the 22nd century."
Given the mounting research, what happened at Bute Inlet can be interpreted as a preview of what we will see as our glaciers continue to melt and disappear, when ice has been replaced by high-altitude water that along with melting permafrost and steepened rock, strains under the force of gravity.
Marten Geertsema, a geomorphologist with B.C.’s Ministry of Lands, Natural Resource Operations and Rural Development and a resident landslide expert, says the key to understanding glacier-related landslides will be to probe how they happen — both now and in the past. That means not only visiting the Bute Inlet slide site to investigate on the ground, but revisiting historical “monster slides” that dwarf what happened in Bute Inlet.
Geertsema cites two examples: the infamous Hope slide, more than four times bigger than the Bute disaster, which dropped over 40 million cubic metres of rock and earth rock onto a highway just outside Hope, B.C., in January 1965, killing four. And the more recent Mount Meager slide near Pemberton which was even bigger.
Clague points to Europe in 2003, the year of an infamous heatwave, which saw an increasing number of rock falls and slides in the Alps, in response to a surge in temperatures. And in the Andes Mountains of Peru, a farmer is suing a German power company for its role in causing climate change, and more specifically, for creating a large glacial lake at risk of a catastrophic outburst flood, putting 120,000 people at risk.
B.C.’s Coast Mountains do not have concentrated populations of Europe or parts of Andean Peru, but Clague says we need to look at the Bute incident as a cautionary tale and plan for the future.
“Imagine a big landslide coming into Shuswap Lake, or into one of our big [hydro dam] reservoirs. It’s not impossible to imagine that it would be very disastrous.”
While we cannot predict landslides, there are things we can do now to minimize potential hazards. Clague points to Robin McKillop, one of his SFU master’s students from the early 2000s, who prophetically based his master’s thesis on creating a methodology to evaluate the risk of landslides on the B.C. coast, which saw him survey 160 different glacial lake locations back in 2005, including the Elliot Creek watershed that flooded into Bute Inlet.
(He did not flag the Elliot Creek area at the time, because he was focused on identifying unstable moraine dams at risk of catastrophic breach, as opposed to outburst floods caused by rockfall.)
McKillop is now a geomorphologist with Palmer Environmental Consulting Group where he evaluates the risks of landslides, earthquakes and other natural phenomena for resource industry clients. He says the work he did as a master’s student with Clague could be used to improve and expand on the limited inventories the province currently maintains.
Given the vastness of the B.C. coast, he says we need to narrow the focus when it comes to identifying at-risk areas. “It’s best to do things backward almost.” That means, from the outset, we need to identify the elements most at risk on the landscape, and look at the potential hazards there first. That means cataloguing existing communities, wilderness lodges, hydroelectric and resource infrastructure, hatcheries, and not least, the natural resources that continue to sustain many First Nations in the hinterland. “That’s one way we can fast-track getting some answers out where it matters most.”
A spokesman for the Ministry of Forests says the province doesn’t currently have an “official dedicated monitoring program for landslides,” but that limited monitoring for slides is done using imagery.
There are other ways the province can be proactive in warning about future landslides. Geertsema points to how the province currently uses sensors to monitor potentially unstable slopes near highways. He is also excited about how we can use radar satellites that can monitor at-risk slopes. It doesn’t work well in forested areas, he says, but in rocky mountainous areas, we would be able to detect movement as it happens. “That’s one of the main tools that could be developed.”
In other parts of the world — like the Himalayas, the Andes of South America, and the European Alps, for example — the danger of mountain landslides revolve around loss of human life. Glacial floods like the one that occurred above Bute Inlet have claimed more than 12,000 lives globally by one estimate. But on the B.C. coast, the ecosystems and natural resources that First Nations depend on will bear the brunt.
Not long after the Bute disaster was discovered, Chief Darren Blaney of the Homalco First Nation, whose traditional territory includes Bute Inlet, took a helicopter to see the devastation.
It was a rare clear day, and they got right up to the glacier. The lake was gone. Coho and chum salmon spawning grounds were erased as the tsunami roared down Elliot Creek and scoured parts of the Southgate River. Homalco’s new ecotourism resort, about 10 kilometres from the slide, escaped damage, but the potential loss of salmon to the area puts the future presence of grizzly bears into question, which will be a big draw for post-COVID tourists. Worse still are the impacts on Homalco’s food security.
“This [disaster] has a bunch of branches to it, from archaeological, to climate change, to forestry, to even the logging we have to do up there,” says Blaney.
About four kilometres of logging roads and a bridge were destroyed, which is needed by Homalco’s logging company to access cut blocks near the Southgate River. Even timber they planned to harvest was destroyed by the slide, he says, translating into a direct revenue hit for the First Nation. It’s uncertain if the logging access roads can even be rebuilt, given that the ground is now so unstable.
The slide disturbed so much forest and land that the Homalco are now planning an archeological investigation to try and identify any unearthed artifacts and other remains.
Salmon is a concern that eclipses all others. The disaster couldn’t have come at a worse time, given that in recent years the Homalco have not been able to catch even the small allotment of chum allowed to them by law. In addition to partnering with the province and Hakai Institute to better understand the slide, they are now in talks with the federal Fisheries and Oceans Canada, in hopes of restoring the damage to the chum and coho salmon spawning grounds.
These are the same places where Blaney’s forebearers would place fish traps each fall for chum. His grandfather would set up a seasonal salmon fishing camp in the Southgate River, spending long periods of time fishing and preserving fish with the extended family.
When travelling through the area, Blaney says his grandfather would sometimes have to steer his boat to the centre of Bute Inlet, if he heard the rumbling coming from big mountain glaciers high above, usually the sign that a big piece of ice had broken off, for fear of what might come down the mountain. But with climate change, he says, it’s all different now.
“There are more torrential downpours, the 200- and 500-year floods are a lot more now,” he says, which not only bodes ill for the stability of the mountains and glaciers, but for the salmon whose spawning habitat is destroyed by the torrents of storm water.
Amid all the devastation, the Homalco continue to hold their breath: some researchers have warned that the first slide could trigger a second one soon. When, they can’t say.
Meanwhile, Bute Inlet was still cloudy with sediment almost two months after the landslide, with unknown consequences to the entire marine ecosystem.
As the Homalco are now witnessing firsthand, the disaster at Bute Inlet is a signpost to the future. The effects of rising greenhouse emissions, like the Big Melt they trigger, have seemed gradual, inviting complacency. Now researchers are measuring the real impacts retreating icefields already are having on people and nature. And like the slowly drying out forests that suddenly but increasingly burst into flame, we need to be aware that melting glaciers can give way in an instant, wreaking devastation.
As the Big Melt unfolds, so too does the urgency to lessen its speed and impact by combatting the climate crisis.
Read more: Environment