Fire and ice

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      Nothing would throw a crimp into the 2010 Winter Olympics in Whistler quite like a volcanic eruption. Fire and ice are a bad mix, especially in steep terrain. And there are mountains aplenty in Western Canada's winter playground, which falls smack in the middle of something called the Garibaldi Volcanic Belt.

      One of many volcanic peaks in the belt, Mount Cayley rises 2,264 metres above the Squamish River to the west and 1,844 metres above the Cheakamus River to the east. It is 30 kilometres east and slightly south of Whistler, 49 kilometres due north of Squamish and some 93 kilometres north of downtown Vancouver, putting it in close proximity to well over half of British Columbia's human population.

      The Garibaldi volcanic belt is one of many collections of volcanoes running along the western spine of South and North America. They arc across the North Pacific along the Aleutian Islands before dipping south and west through Japan and Indonesia, then turning east over northern Australia before heading deep down under to Antarctica. Geologists call the whole complex the Pacific "Ring of Fire", and with good reason. Here, some of the world's most powerful earthquakes have occurred, the most recent almost a year ago today, when parts of Indonesia's and Thailand's coasts were submerged under relentlessly advancing walls of seawater after a quake triggered the worst tsunami in modern history. It is also here that some of the world's notable volcanic eruptions have occurred. In 1883, for example, much of the small Indonesian island of Krakatoa vanished in a series of thunderous explosions that triggered devastating waves that claimed thousands of lives. And it is here, too, that some scientists believe a volcanic eruption of momentous magnitude occurred in AD?535, an eruption so powerful that it sent vast amounts of vaporized seawater and volcanic ash into the atmosphere, where it circled the globe and triggered a "volcanic winter" that truly made the Dark Ages dark.

      Even relatively recent events at Washington state's Mount St. Helens have an otherworldly feel, at least for those of us not directly witnessing them. But for Vancouver volcanologist Catherine Hickson, who was at Mount St. Helens on May 18, 1980, and nearly became a "crispy critter" in the three-plus hours it took her to reach safety after its eruption, there is nothing abstract about what happened there. "It indelibly impressed upon me that there are events that can have huge consequences for us here," Hickson recalls. "And, remember, Mount St. Helens was not a big eruption."

      Yet to even understand when and where a "small" eruption might occur in Western Canada, it turns out that experts like Hickson are pretty much in the dark. In 2003, Hickson was one of three scientists with the Geological Survey of Canada to report on a hypothetical eruption at Mount Cayley. The trio noted that "no volcano monitoring has been done in Canada at a level approaching that in other developed countries with historically active volcanoes." In fact, no equipment to detect seismic activity-a likely precursor to an eruption-is located within 15 kilometres of any Canadian volcano, making it very difficult to predict an impending event. Moreover, just to complete a rapid evaluation of hazards around nine B.C. volcanoes where seismic activity does occur would take current staff up to four years to complete. In short, as Hickson and her coauthors warned in the journal Natural Hazards, Canada has nothing approaching "timely eruption forecasting".

      Perhaps it's time it did.

      IN THE HISTORIC record, there is only one volcano known to have taken human life in what is now Canada. The event coincided with the arrival of the first European explorers to penetrate the uncharted coastal waters of northern British Columbia. In a misty and mysterious land where thickly forested mountains dropped out of the heavens to form ragged shorelines, among the first things that Juan Francisco de la Bodega y Quadra and his crew members aboard the Sonora encountered was fire. The year was 1775. According to Padre Miguel de la Campa, what Spanish crew members, little more than boys, saw near the mouth of the Nass River was a landscape in upheaval. "They suffered somewhat from the heat," de la Campa penned by candlelight below deck in his diary, "which they attributed to the great flames which issued from four or five mouths of a volcano and at nighttime lit up the whole district, rendering everything visible."

      From their vantage, the visitors could not have known that on land an estimated 2,000 members of two Nisga'a tribes perished in the eruption. In 1935, pioneering anthropologist Marius Barbeau-who gained fame for his work on British Columbia First Nations-journeyed up the Nass River, reporting on the expedition in the pages of the Canadian Geographical Journal. Among Nisga'a elders, Barbeau wrote, a certain "veteran" named Neesyoq told vivid stories of the volcano's eruption and its aftermath.

      Neesyoq claimed that the eruption was a consequence of some young Nisga'a men incurring the wrath of the Salmon Spirit for showing disrespect to a "humpback salmon" caught in the Nass River.

      "The volcanic eruption soon after broke out," Neesyoq said. "First there was smoke, like that coming out of a house, a big pillar of smoke. It was as if a house was burning on the mountain top. The people saw a big fire. The fire came down the side in their direction, but not as fast as a forest fire. It moved down slowly, very slowly.

      "It was strange and frightful," Neesyoq continued. Invisible fumes pushed ahead of the advancing wall of fire. "Those who smelled them were smothered," the elder said, and their bodies "stiffened like rock".

      Today, the glassy, black basalt deposits comprising the Nass lava flats are a draw to tourists and local residents alike, much as they were to Sutherland Brown, a geologist with the provincial Department of Mines and Petroleum Resources, who, after visiting the area in the late 1960s, reported his findings in a 1969 entry in the Canadian Journal of Earth Sciences. Brown concluded that the lava flow began in a narrow valley of a tributary of the Tseax River. It then moved five kilometres downhill and formed a dam, creating present-day Lava Lake, before descending northward down the Tseax Valley to the Nass River, where it fanned out to cover an area almost 10 kilometres long and a little more than three kilometres wide. The magnitude of the flow was so great that it actually pushed the main stem of the Nass River over to the northern fringe of the valley flat. In total, a landmass roughly 38 square kilometres in size was buried to an average depth of 12 metres. Put another way, it was enough to bury a good chunk of Vancouver-from the western fringes of the UBC Endowment Lands east to Cambie Street, and from False Creek south to the Fraser River-under four storeys of lava.

      Neither Spanish nor Nisga'a witnesses to that distant event had ever heard of continental drift, a concept first advanced in a 1915 book-The Origin of Continents and Oceans-by Alfred Wegner, a German explorer and meteorologist. But it would have much to do with what happened in the Nass Valley 230 years ago. Like many pioneers, Wegner's revolutionary idea was born of a simple observation. As author Simon Winchester recounts in Krakatoa: The Day the World Exploded, Wegner's "roving attention" was drawn to an obvious pattern that revealed itself in a simple map of the world. As Wegner wrote to his fiancée years before publishing his eye-popping theory:

      "The coastlines of Africa and South America are such-with the huge eastward convexity of Brazil so alluringly similar to the immense eastward concavity between Nigeria and Angola-that they seem to fit." Wegner would later suggest that over tens of millions of years, large landmasses pulled apart or collided in a process he called "continental displacement". Wegner's work was derided by some, but further geological study proved him right. Today, Winchester writes, geologists generally agree that "the earth's surface appears to be armored with between six and thirty-six…rigid plates, depending on how they are defined and counted." And what happens where these plates meet explains a lot about volcanic activities.

      "The problem is this," Hickson explains, "all of North America is essentially moving westward toward Japan, but this piece of oceanic plate is coming toward us. So we have this collision zone. And where you have collision zones you get mountain ranges, volcanoes, and earthquakes."

      How so? While the basaltic plate underneath the ocean is generally dense and hard, its continental cousin lighter and looser. When the two butt heads, they trigger something known as subduction. The heavier oceanic plate dips under the continental plate, heading toward the earth's hot inner core: a metaphoric hell, as it were. And it carries parts of the continental plate with it.

      "What starts off beneath the sea as cold and solid now moves down toward the hot mantle and turns viscous and runny," Winchester writes. "Its fluid components begin to 'sweat out'-suddenly bubbling and frothing and coursing, and because they are light and volatile, so rising back up again, passing into the solid mantle through which all the downsliding ingredients had passed. To make matters more complicated still, as they course upward through this material, they began to melt that too.

      "The Promethean material searches ceaselessly for some weakened spot in the crust above it. Every so often it finds one, a crack, a crevice, or fault, and then forces its way up into a holding chamber. Before long the accumulating pressure…becomes too great, and the temperature too high, and the proportion of dissolved gas becomes too large, and it explodes out into the open air in a vicious cannonade of destruction."

      Something similarly vicious occurred at Mount Meager, a neighbour to Mount Cayley, a few centuries before Christ's birth. It was an eruption equal in force to that occurring at Mount St. Helens 25 years ago, and it is on this that Hickson and her fellow scientists at the Geological Survey base their Mount Cayley disaster scenario.

      The first signs of trouble at Mount Cayley would likely be increased seismic activities-tremors-in and around the mountain. Whether such tremors were caught, however, would depend entirely on whether the equipment Hickson and others bemoan not being in place now was actually there. Eventually, the tremors would destabilize things enough that magma would penetrate upward into newly opened spaces, bringing the liquid rock closer to the surface and causing the mountain itself to swell. With swelling would come fractures, and with fractures, more magma movement, ever upward and outward. Hot springs on the mountainside would, by this point, display more "vigour"; in other words, they would get hotter. Shortly after, the first of many landslides might begin, and if they were severe enough, they'd cut right across the Squamish River. "Flooding," Hickson says, "would become a major problem for the town of Squamish and could ultimately overrun parts of Highway 99."

      The continued presence of unimaginably hot magma near the surface would almost certainly trigger what are known as phreatic explosions-a common occurrence in situations where there is a lot of snow or ice. As heat within the mountain and near the surface melted the snow without, water would begin percolating into the hot rock. As hot water converted to steam, pressure would build. And as it did, it would eventually release, either by sudden and violent venting or, in the absence of adequate vent routes, exploding outward, pushing tons of rock with it.

      At this point, Hickson and company somewhat dryly report: "Squamish would be fully evacuated, Whistler would be at least considered for evacuation, and Highway 99 closed."

      Often, Hickson and company report, the vivid orange lava flows we associate with volcanoes are "among the least hazardous" phenomena associated with eruptions. Lava generally moves slowly. You can usually outrun it, and in the broad scheme of things, it does not affect a large area. Lahars are another matter entirely and could be set in motion by phreatic explosions. In the Garibaldi volcanic belt, much like the trio of massive snow- and ice-covered volcanic peaks to Vancouver's south-Washington state's Mount Baker, Mount Ranier, and Mount St. Helens- lahars may be our biggest worry.

      Lahar is the Javanese word for mudflow. These flows always consist of water and volcanic rock "particles", some of which may be as big as houses. But it is the fine particles that are of most concern. The magma inside a volcano has two important constituents other than liquid rock: heat and gas. And the gas of most concern is sulphur dioxide. Heat, gas, and snowmelt seeping into the mountain combine to form sulphuric acid. As the acid inexorably eats away at the surrounding rock, it breaks it down into particles. The resulting slurry of acidic water and rock particles create a claylike mixture that, when unleashed, can result in particularly nasty mudflows-nasty because the clay content in such mixtures makes them difficult to dilute. This is very important because when lahars are triggered, they naturally follow the contours of the land, and river valleys in particular. "The more clay content in a lahar, the more it tends not to dilute," says Willy Scott, a volcanologist with the U.S. Geological Survey's David A. Johnston Cascades Volcano Observatory in Vancouver, Washington. High-clay-content lahars move as cohesive blocks. They don't readily break down. And they displace a lot of river water in the process.

      Hickson and company liken such flows to wet concrete, with the added wrinkle that they move at alarming speeds, an average of 30 to 65 kilometres per hour and with top speeds of about 100 kph, and travel great distances before eventually stopping. Study of sediments associated with a large lahar at Mount Baker-that awesome 3,285-metre, snow-covered peak that rises above the clouds just south of the mountains hemming in the southern flank of the Fraser Valley-suggests that some 6,800 years ago a cementlike slurry slid off the mountain and may have travelled 100 kilometres before being stopped by Puget Sound. A 1995 report by the U.S. Geological Survey said that the slurry would have been at least 100 metres deep and of devastating force. Masses of material are known to have entered the Nooksack River, and scientists infer that it would have resulted in major flooding of the Sumas River, which, in turn, would have put parts of the Fraser Valley under water.

      Similarly massive lahars have been detected in the geological record of Mount Ranier, again terminating at Puget Sound, but with the important caveat that if such a massive mudflow were to recur, its path would be directly through parts of a relative newcomer to the landscape of the Pacific Northwest: Seattle.

      Such flows could be expected before, during, and even years after an eruption at Mount Cayley. When the eruption itself occurred, it would likely be "sustained" and "explosive" in nature. Pyroclastic flows-superheated, dense avalanches of gas, rock particles, and ash-would race down the mountainside at speeds of up to 150 kph. Ash and water particles would also be blown 20 kilometres or more into the air, and the dense plume would likely be sustained for 12 or more hours after the eruption began. Heavier ash particles would soon drop out of the darkened sky over Greater Vancouver, Chilliwack, Abbotsford, the Fraser Valley, Bellingham, Kamloops, Whistler, and Pemberton, forcing a suspension of all local air traffic.

      Depending on the ash volume, weak structures, including some buildings, would be vulnerable to collapse, Hickson and company report. In addition, "the ash would damage power and communications lines, satellite dishes, computer and other electrical equipment. Telephone, radio, cell phone and satellite communications would be cut off."

      "Thirty-six hours after the erup?tion began, the ash plume would spread to…most of the west coast from Seattle to Anchorage, causing all airports to be closed and all relevant flights to be diverted or cancelled. The plume would then sweep eastward and disrupt air traffic across Canada from Alberta to Newfoundland."

      All this and more, the experts tell us, could be expected from a relatively small volcanic eruption.

      When the editors of Natural Hazards first approached Hickson and asked her to come up with a volcano-related disaster scenario, they asked for a worst-case scenario. A worst case would be what volcanologists refer to as a caldera event. That's where the explosive force is so great that you end up with a crater or hole greater than two kilometres across. Volcanic explosions of this kind have occurred in what is now Yellowstone Park. The last such eruption occurred there about 640,000 years ago, and the one before that another 640,000 or so years earlier.

      But Hickson and the rest of the team took a pass on illustrating just what that would mean. For one, no one knows when such an event would happen again. It could be a few years away. It could just as easily be tens of thousands of years away.

      Readers wanting to get a taste for what something big might look like, however, would be hard pressed to find a more tantalizing scenario than that portrayed in David Keys's 2000 book Catastrophe: An Investigation Into the Origins of the Modern World. In it, Keys suggests something monumental happened in 535 AD. His interest in writing the book was spurred by numerous written accounts in the mid-sixth century of bizarre weather aberrations: massive crop failures, unseasonably cold weather, droughts followed by periods of heavy rain, snowstorms in summer, months of diminished sunlight. Climatic upheaval for a period of decades around this time is also borne out in modern-day scientific analyses of annual growth rings in ancient trees and in the layer-upon-layer of compacted snow that formed ice sheets. Something, indeed, happened around that time that appears in the physical record. Weather patterns around the world were shaken up.

      Keys suggests that the climatic chaos triggered all manner of things, from the devastating Black Plague to a series of great political and religious upheavals, including the origin and spread of Islam, the rebirth of a united China, and the demise of numerous ancient super-cities. But what set the weather on its erratic course? The most likely causes, Keys surmised, were either a very large object from space colliding with Earth or, more likely, a gigantic volcanic eruption that probably occurred near present-day Indonesia.

      In ancient Javanese writings, just such an event is described, one that suggested the creation of an entirely new body of water-later called the Sundra Straits-that would separate the islands of Java and Sumatra.

      Ken Wohletz, a geologist at New Mexico's Los Alamos National Laboratory, says that were such an eruption to have taken place, it would have vaporized up to 100 cubic kilometres of seawater and carried the vapour and volcanic ash 50 kilometres into the atmosphere.

      Although much of the vapour would have fallen back to earth as an ash-clogged rain within hours of the volcano's eruption, as much as half of it would have stayed up there, where it would have been "carried around the world by stratospheric winds", Wohletz writes. "This vapour would have condensed to form ice crystals, and these ice crystals would disperse in the rarified air to form stratus clouds, darkened by entrained ash."

      A dark cloud layer, anywhere up to 150 metres thick and circling the globe, would have taken years to dissipate. In the meantime, temperatures would have dropped on average between 5 and 10 degrees for up to two decades. Under such circumstances, all the social and political upheaval Keys writes about would have been linked. And the unifying theme would have been sudden climate change.

      In the closing pages of Catastrophe, Keys suggests that given the 640,000-year intervals between two caldera-forming eruptions at Yellowstone, the world is past due for a globally significant eruption. It is a suggestion that obviously rankles the U.S. Geological Survey. Such events do not, the Survey says on a Web site dedicated to future volcanic activity in the Yellowstone area, occur with the same consistency as the national park's famed geyser, Old Faithful.

      "The fact that two eruptive intervals (2.1 million to 1.3 million and 1.3 million to 640,000 years ago) are of similar length does not mean that the next eruption will necessarily occur after another similar interval," the USGS says. "The physical mechanisms may have changed with time. Furthermore, any inferences based on these two intervals would take into account too few data to be statistically meaningful." To say that an eruption that might happen in tens or hundreds of thousands of years is overdue "would be a gross overstatement".

      Notably absent from the USGS's discussion is any mention of Keys's book.

      Some catastrophes, it seems, are not worth dwelling on. For when they occur, a cancelled Olympics will be the least of our worries.