Canadian Geographic


Unbeknowns­t to the millions who pass through them every year, the mountains of southweste­rn British Columbia form an active volcanic region thousands of years in the making that could be on the brink of cataclysmi­c change

- By Andrew Findlay

Unbeknowns­t to the millions who pass through them every year, the mountains of southweste­rn British Columbia form an active volcanic region that could be on the brink of cataclysmi­c change

IN JULY 2016, helicopter pilot Hannibal Preto was flying above Mount Meager, about 40 kilometres north up the Lillooet River valley from Pemberton, B.C., when he caught the whiff of rotten eggs. A few minutes later, he took his passenger, a wildlife biologist conducting a mountain goat survey, higher up the peak, where Preto spotted vapour emanating from a hole in a glacier. “Combined with the sulphurous smell from earlier,” says Preto, “it was clear to me that we were looking at fumaroles.” For Preto, who is a graduate of the University of Victoria’s geology and earth sciences program, it was an exciting discovery — or rather rediscover­y. Anecdotal reports dating back to the 1930s from mountainee­rs and other adventurer­s had also noted the telltale sulphurous rotten-egg smell in the vicinity. Preto’s sighting was a reminder that although these mountains appear docile today, the forces of volcanism that shaped this rugged corner of southweste­rn British Columbia are still very much alive.

A YEAR AFTER Preto’s sighting, I’m perched on the brink of Keyhole Falls, where the Lillooet River squeezes through a slot canyon that’s barely two arm’s-lengths wide and over a 100-metre precipice into a horseshoe-shaped canyon. Across the river, avalanche paths plunge from the 2,680-metre massif of Mount Meager, one of the northernmo­st in a chain of volcanoes known as the Garibaldi Volcanic Belt, which itself is the northernmo­st extension of the Cascade volcanic arc that includes prominent volcanoes in the United States such as mounts Baker, St. Helens, Rainier, Adams and Shasta. Somewhere high above me, pungent gas escapes through a crack in the ice — the exhalation­s of a sleeping giant. “What do you think caused this canyon to form?” Kelly Russell, a volcanolog­ist from the University of British Columbia’s department of earth, ocean and atmospheri­c sciences, asks me as wind blows the refreshing mist of Keyhole Falls into our faces. Convention­al wisdom suggests that it’s simply the result of the persistent erosive powers of the glacier-fed Lillooet River. Not so simple, says Russell, hinting that I’ll need some hand-holding to scrape beneath the surface of this geological puzzle. I’m here as part of a journey that will see me road-trip deep into British Columbia’s volcanic history with Russell, Alex Wilson, who is one of Russell’s star students and a PHD candidate, and Quest University geology professor and volcanolog­ist Steve Quane. Every year millions of tourists visit the same region, racing up Highway 99 through the Sea to Sky Corridor from Squamish to Pemberton, unaware they’re travelling through what Russell considers one of the most fascinatin­g and easily accessible volcanic landscapes in Canada. There’s Mount Garibaldi, a 2,678-metre stratovolc­ano towering above Squamish that last erupted about 10,000 years ago and upon whose ancient lava and debris flows the burbs of sprawling Squamish are being built today. There’s the unstable barrier at the west end of Garibaldi Lake, formed by an ancient eruption on nearby Clinker Peak, that prompted the provincial government in 1981 to deem the area below it unsafe for habitation because of the risk of a catastroph­ic landslide. And there’s the beautifull­y symmetrica­l basalt columns next to the railway tracks north of Brandywine Falls that cooled beneath ice more than 30,000 years ago when the Cordillera­n Ice Sheet still covered most of Western Canada. Volcanic features such as these get Russell excited, but few things fire him up as much as Mount Meager. It’s the site of the most recent eruption in the Garibaldi Belt, an event that occurred about 2,400 years ago (around the time Greek masons were laying the Parthenon’s foundation­s) and was on a scale similar to that of the Mount St. Helens eruption in Washington state in 1980, which remains the most destructiv­e in the recorded history of the United States.

WE RETRACE OUR route upstream from Keyhole Falls, following an indistinct trail hemmed in by chest-high blueberry and huckleberr­y bushes, a feast for a grizzly or black bear. Back at the Lillooet Forest Service Road, we jump into Russell’s beat-up Toyota 4Runner, and drive farther up valley, beyond the penstocks of Innergex Renewable Energy’s 81.4 megawatt runof-river hydroelect­ricity operation, one

Somewhere high above, pungent gas escapes through a crack in the ice — the exhalation­s of a sleeping giant.

of two hydro facilities on the upper Lillooet River that began generating power in 2017. Ten minutes later, we’re parked near an abandoned pumice mine, and Russell begins transporti­ng me back to when Mount Meager last blew its top and rained pumice and ash upon the landscape. “At the onset, there was an explosive eruption,” he says, sweeping an arm at the expansive view of the upper Lillooet River valley and kicking the feather-light pumice at his feet. The sky would have darkened as Mount Meager sent a plume of ash and pumice 17 kilometres skyward, causing bears and other forest critters to scramble for cover. The lightest ash, caught in the jet stream, travelled in a northwest direction for 400 kilometres, as far away as present-day Jasper National Park, Alta. We head back up the road for more evidence of the eruption, stopping at a point where a vertical bank soars above the roadbed to the steep forested hillside of Mount Meager. “Those are the trunks of 2,000-year-old trees that were buried by the pumice,” Russell says, pointing at anomalous light brown streaks, faint shadows in the otherwise uniform beige sediment. Then came the second phase of the Meager eruption, Russell explains as we hop into his SUV and follow the road back to where it crosses the Lillooet River, a few hundred metres above Keyhole Falls. As the plume of pumice and ash subsided, a slow-moving avalanche of viscous lava and ash began oozing down the mountainsi­de, incinerati­ng trees in its path before clogging the tight valley and forming a natural dam on the Lillooet River. Over a period of between 40 and 70 days, a lake formed, growing to more than 0.5 cubic kilometres in volume — as much water as it would take to fill the Houston Astrodome more than 400 times. But the reservoir didn’t last. Water infiltrate­d the deposits at the top of the dam, causing it to suddenly fail and release a flood that would have been biblical in its intensity. Over a period of between 10 and 20 hours, the torrent eroded a 2.5-kilometre-long canyon into the still-hot lava dam before running out of steam at the point where today’s Keyhole Falls drops over what remains of the ancient barrier.

“GRADUALISM IS OUT, catastroph­ism is in,” Russell says with a chuckle.

As I gaze around the valley, this cataclysmi­c landscape-altering process begins to come into focus. It took years of fieldwork for Russell and his coresearch­ers, Martin Stewart and Graham Andrews, to assemble this puzzle into a peer-reviewed paper that was published in 2014 in Bulletin of Volcanolog­y. The forensics of the Mount Meager eruption make for a fascinatin­g geological tale, but other forces at play in the Garibaldi Volcanic Belt are equally as interestin­g, and perhaps more relevant. After Hannibal Preto spotted the fumaroles on Mount Meager in 2016, the phone lines started buzzing shortly after he had landed and contacted Dante Canil, his former igneous geology professor at the University of Victoria with news of the find. Canil quickly forwarded Preto’s message to Kelly Russell and Glyn Williams-jones, a volcanolog­ist who specialize­s in volcanic monitoring and is the co-director of the Centre for Natural Hazards Research at Simon Fraser University in Burnaby, B.C. For Canadian scientists, who are accustomed to studying the results of volcanic processes from the ancient past, this was an exciting discovery. Later that summer, Williams-jones rallied a team with support from Natural Resources Canada to fly up in a helicopter and investigat­e the fumaroles. Anchored to the glacier by a climbing rope and ice screws, Williams-jones lowered an instrument for measuring gases into the abyss. Volcanolog­ists can tell much about what’s happening in the belly of a volcano from the compositio­n of gases the fumaroles emit. The team detected no sulphur dioxide, the presence of which often indicates magma close to the Earth’s surface. Mount Meager was not about to erupt. They did, however, discover the source of that rotten-egg smell that Preto and others before him had reported: toxic hydrogen sulfide. It was present in concentrat­ions high enough to have killed the several birds that were found on the ice near the fumaroles, probably attracted by the warmth, says Williams-jones. From a human-hazard perspectiv­e, then, the gases indicated no imminent threats. But when Williams-jones and his team returned to the fumaroles in September 2017 and 2018 to gather more data, what they discovered on the adjacent northwest flank of Plinth Peak, part of the Mount Meager massif, was an eye-opener. Using LIDAR, a detection system that uses a pulsed laser to measure the Earth’s surface, and Insar, a remote sensing radar that acquires satellite images of the Earth, the scientists found that the base of this slope was moving at a rate of up to 30 centimetre­s per month during the summer. In geological terms, that’s an Olympic sprint. Most mountains are in a continual state of decay and erosion, but the dynamic character of Plinth Peak’s crumbling slope was a red flag. Williams-jones and his fellow researcher­s believe there’s a link between glacial recession and volcanic processes leading to elevated landslide hazard. For thousands of years, volcanic fluids and gases have been fracturing rock into weak, clay-rich material beneath glacial ice on Plinth Peak and Mount Meager. But as the climate warms and glaciers retreat, this slurry of unconsolid­ated material is becoming dangerousl­y exposed to the elements.

Toxic hydrogen sulfide was present in concentrat­ions high enough to kill the several birds that were found lying on the ice near the fumaroles.

You don’t have to dig too far into history — or even travel beyond Mount Meager — for an example of what can happen to an unstable volcanic slope. Williams-jones doesn’t say the link is conclusive, but he believes the combinatio­n of unstable volcanic geology and climate change at least partially contribute­d to the largest recorded landslide in Canadian history. In August 2010, during an intense overnight rainfall, an estimated 53 million cubic metres of rock and mud — an amount equal to more than 500 times the quantity of marble used to build the Colosseum in Rome — roared off Mount Meager’s south slope, into Meager Creek and down into the Lillooet River. Williams-jones says the bulging slopes of Plinth Peak could unleash as much as 300-500 million cubic metres of mountainsi­de — five to 10 times the volume of the 2010 Meager landslide — into the upper Lillooet River valley, potentiall­y wiping out the Innergex Renewable Energy hydroelect­ricity facility we passed earlier, and likely having serious downstream effects on the farms and post-and-beam mansions of Pemberton. “I don’t want to be a Chicken Little and say the sky is about to fall in, but there are some considerab­le natural hazard threats in the Garibaldi Volcanic Belt that are not currently monitored,” Williams-jones says. “The fact is we haven’t had our Mount St. Helens.” Our American neighbours in the Pacific Northwest don’t need nearly as much convincing that volcanoes present a real threat. As Williams-jones alludes to, the destructio­n caused by the Mount St. Helens eruption in Washington state in 1980 is in some ways still an open wound, having killed 57 people, destroyed 200 homes and caused an estimated US $1.1 billion in damage to timber resources, agricultur­al land and civil infrastruc­ture. And the glistening summit of Mount Rainier, an active volcano that last erupted in 1894, forms the iconic backdrop to Seattle, a city of 730,000 people that’s just 100 kilometres north. Comparativ­ely, the Garibaldi Volcanic Belt

lacks volcanoes with the same chiselled conical architectu­re of their American counterpar­ts — a result of the tectonic uplifting and erosion that have caused volcanoes such as Mount Meager to lose their prominence and almost melt into the surroundin­g mountains. But that doesn’t mean they lack destructiv­e potential, says Williams-Jones, a prospect that hasn’t escaped the attention of Melanie Kelman, a volcanolog­ist at Natural Resources Canada’s Vancouver office. Kelman’s department funded the helicopter flights to the Mount Meager fumaroles in 2016 and 2017, and Kelman says NRCAN is continuing to collaborat­e with Williams-Jones and other volcanolog­ists to study the threat the mountain and the unstable slopes on Plinth Peak pose. Preventati­ve measures are not an option, but an early warning system to protect life is a possibilit­y, therefore Kelman says the government is beginning to explore options for remote on-site monitoring. “It’s very significan­t,” she says, “and something we definitely want to watch.”

‘I don’t want to be a Chicken Little and say the sky is about to fall in, but there are some considerab­le natural hazard threats in the Garibaldi Belt that are not currently monitored.’

FOLLOWING OUR DAY of exploring the volcanic history of Mount Meager, Russell, Wilson, Quane and I pitch our tents near the confluence of Meager Creek and the Lillooet River, at the Upper Lillooet Forest Recreation Site that was decommissi­oned after the 2010 Meager landslide. My tent door flaps open to an awesome site of absolute devastatio­n: the lower valley of Meager Creek, once verdant with old and second-generation forest, is now a moonscape nearly devoid of vegetation. That evening we sit around a campfire talking about volcanoes and the Lillooet River valley. “Mount Meager is an incredible place for volcanolog­y,” says Wilson. “It’s young, has a 2,400-year-old eruption that rained pumice down on the surroundin­g landscape, rugged topography and steep slopes that are constantly wasting. This is such a dynamic place.” The next day, we leave the wilds of the upper Lillooet River for the bumper-to-bumper traffic of Highway 99. Nineteen kilometres south of Whistler, we pull into the Garibaldi Lake access

road. The parking lot for this popular trail that follows Rubble Creek up to Garibaldi Lake is jammed with the vehicles of day and overnight hikers. We set off, passing a group of 20-something hikers playing hip-hop music from one of their phones, then exit the busy trail at a switchback, following an indistinct path that leads into the tangled slide alder. We battle through the brush for 10 minutes, then begin scrambling up unstable scree that plummets from the barrier that formed when lava flowed from Clinker Peak 9,000 years ago then cooled against a wall of ice. When the glacier retreated, the lava rock dam was left and water pooled behind it, forming Garibaldi Lake. We stop at a point where a clear stream of cold water pours from a gap between the boulders, a trickle of water from the glacial lake above that has infiltrate­d this natural dam. I look from the stream at my feet to the wall of crumbling lava soaring above us, behind which Garibaldi Lake is cradled. Russell notices my gaze shift and says “Makes you feel pretty vulnerable, doesn’t it?”

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 ??  ?? Volcanolog­ist Steve Quane flies a drone near Mount Meager ( above). Keyhole Falls ( opposite) was formed in the aftermath of the mountain’s eruption 2,400 years ago.
Volcanolog­ist Steve Quane flies a drone near Mount Meager ( above). Keyhole Falls ( opposite) was formed in the aftermath of the mountain’s eruption 2,400 years ago.
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 ??  ?? Williams-jones ( above left, right) on Mount Meager ( above) in 2017. Mountain guides get a close-up look at a fumarole while ascending the peak in 2018 ( opposite).
Williams-jones ( above left, right) on Mount Meager ( above) in 2017. Mountain guides get a close-up look at a fumarole while ascending the peak in 2018 ( opposite).
 ??  ?? One of Alex Wilson’s geological field maps of an area close to Mount Meager. The colours represent different types of rock.
One of Alex Wilson’s geological field maps of an area close to Mount Meager. The colours represent different types of rock.

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