Island on Fire Page 17
A week and a half later, the ground rips open. Once again, the fire districts are aflame. Huge jets of lava shoot more than 1,000 metres in the air. Lava begins streaming from new volcanic cones and fissures, following the courses of rivers southward just as it did during the Laki eruption.
The well-prepared Icelanders spring into action. The town of Klaustur evacuates, along with farmers in the lava’s path. Police set up checkpoints along the ring road, which lies directly in the course of the advancing lava. Tourists are warned not to travel eastward to the glaciers of Skaftáfell, one of the country’s most popular national parks.
And then the clouds appear. Dark plumes billow above the fissure, laden with toxic gases. Once again, winds are just right to start carrying the volcanic plume eastward and then toward the south. Scientists fly to the plume to measure its chemistry and calculate its likely course. Far overhead, satellites watch as the cloud stretches first toward Scandinavia, and then toward continental Europe and Great Britain.
A farmer in Klaustur, masked against the dust clouds.
When the volcanic haze drifts into Europe, people’s eyes begin to itch and burn. Many have difficulty catching their breath. Environmental experts start measuring levels of sulphuric acid and fluorine in the haze, unsure if they can reassure people that the stuff is safe to breathe. Health authorities warn people not to spend too much time outdoors, especially old people and children.
Occasionally the winds shift, temporarily clearing the haze. But then they shift back, and the dry fog once again covers the countryside. The longer Iceland erupts, the less important the wind direction becomes. The haze has become so diffuse that it settles across Europe like a veil.
By this point airports in many parts of the continent are closed. Hospitals struggle to cope as emergency rooms are flooded with people struggling to breathe. The first deaths come among the old and infirm, and there is a huge run on N95 respirators, the kind that can filter out volcanic particles. No one had ever expected that huge swaths of Great Britain would need respirators, so health authorities have to triage and determine who needs them most urgently. A black market springs up on the Internet as people try to order breathing filters from other parts of the world – only to have deliveries delayed or stopped because ash has grounded flights.
Back in Iceland, agricultural experts warn about fluorine settling out from the haze. Farmers desperately seek to move their animals to unsullied pastures, but none can be found. Sheep die by the tens of thousands, and cattle suffering from fluorosis have to be put down. The country’s livestock industry collapses.
The worst thing about the eruption is that it just goes on and on. For ten long months the fissure keeps spewing pollution. Eventually the ash encompasses so much of the northern hemisphere that all flights are cancelled for several months. Airline companies move as many planes as they can to Buenos Aires, Cape Town and Sydney, but many declare bankruptcy. Ships and trains struggle to move hospital supplies and food to the choking, hungry people of Europe.
Such a scenario may sound far-fetched, but it’s not. ‘I don’t want to be a fearmonger,’ says Anja Schmidt, ‘but these eruptions happened and will happen again in Iceland. And we are more vulnerable now.’ Modern society is so deeply dependent on transportation networks that it simply doesn’t have enough resilience to deal with a Laki-like eruption. Such a cataclysm would test far more than whether jet engines can perform in volcanic ash. It would test to the limit, and probably break, public health and emergency response systems.
How likely is such a disaster? Not as unlikely as you might think. Although an Eyjafjallajökull-type eruption is far more common, a Laki-type eruption happens on average every 200 to 500 years. More than 200 years have passed since Laki blew up. Volcanoes don’t erupt on predetermined cycles, of course, but they do show patterns of activity over time. Scientists can use those patterns to try to calculate how often eruptions of various sizes occur – all the way up to the planet-altering ones.
In the short term, the main thing to worry about is a fairly small eruption – of, say, a VEI 3 or 4 – going off relatively close to a city. Roughly 500 million people live close enough to an active volcano to be at risk. This includes cities such as Naples, close to Vesuvius; and Mexico City, not too far from the steaming Popocatépetl. (Popocatépetl’s name is the Aztec word for ‘smoking mountain’.) We’ve already examined the risks in Naples, so let’s take a closer look at what Mexico’s capital city might be facing.
Popocatépetl has unleashed its wrath three times in the last five millennia – Mesoamerican pottery and other artifacts entombed in the ancient mudflows bear witness to its terrible power. The last of these major eruptions took place around the year 800, and was powerful enough to create a plinian ash plume. At least one research team has argued that mudflows from this eruption buried almost everything around the great pyramid of Cholula, in the Puebla valley. (Some think the structure of the pyramid is a deliberate echo of the volcano’s majestic peak.) Seven centuries later, when the conquistador Hernán Cortés reached Cholula, he marveled at the towering mountain from which ‘both by day and night a great volume of smoke often comes forth and rises up into the clouds as straight as a staff, with such force that although a very violent wind continuously blows over the mountain range yet it cannot change the direction of the column.’
That’s pretty much how Popo – as it’s known locally – looks today. Its summit, at 5,246 metres above sea level, is frequently wreathed in clouds and ash, because after decades of slumber, Popo roared back to life in December 1994. Officials evacuated tens of thousands of people from the surrounding countryside. Since then Popo has continued to erupt intermittently, though not violently; in May 2013, it sent ash drifting over nearby towns.
If Popo were to go off with the ferocity of the 800 eruption, it would rank a VEI of 4. That would make it on the same scale as Laki, but its effects would be very different. The biggest threat would be not a choking haze but churning flows of mud, ash and other rocks, which would rush down the mountain’s slopes and bury everything in their path.
That same sort of risk plagues another famous North American volcano: Mount Rainier, which towers 80 kilometres southeast of the urban sprawl of Seattle. In many ways Rainier is the archetype of the Cascades volcanoes, rising tranquilly above the lushly forested Pacific Northwest. But remember that Mount St. Helens is also in the Cascades, and it blew in 1980 with a VEI of 5, killing 57 people. It also sent the largest landslide in recorded history roaring down the river valley. Avalanching along at more than 200 kilometres an hour, it ripped bridges and houses from their foundations and reached its maximum size about 80 kilometres from the volcano itself. By the time it was all over, much of the river valley was buried under nearly 50 metres of debris.
There’s nothing to say Rainier won’t do the same. In fact, about 5,600 years ago it erupted much like Mount St. Helens. The blast sent mudflows coursing down Rainier’s northeast slope, where they scoured everything in their path. The avalanches eventually covered about 550 square kilometres across the shores of Puget Sound, including the land that is now the port of Tacoma. Over time, other eruptions have piled fresh lava onto Rainier’s summit, partially rebuilding it into a more symmetrical peak. Its last, relatively small, eruption happened about 1,000 years ago. Yet because it lies so close to so many towns, and because of its history of giant mudflows, Rainier remains the most dangerous volcano in the Cascades.
If Popo or Rainier goes off with a VEI of 4 or 5, people will be fairly well prepared. Both mountains are monitored pretty much constantly, and emergency managers are familiar with the kinds of evacuations they would have to conduct if it looked like mudslides were about to start rushing downhill. Undoubtedly not everything would go smoothly: there might be a false alarm or two, and some residents would ignore the warnings until it was too late. But Mexico City and Seattle would survive.
The picture changes when you start considering blasts in the range of VEI
6 and higher. These are on the order of Krakatau in 1883 and Tambora in 1815 – ones that cause regional disaster and have planet-wide effects. Over the past millennium, a blast up to the size of Krakatau has happened about twice per century. And there’s a greater than 10 per cent chance that an even bigger, Tambora-style, event could go off in the next century.
For disasters on this scale, ground zero is likely to be somewhere in Asia. It’s home to a quarter of the world’s volcanoes, and more than two billion people. In 2012, Australian scientists took a broad look at 190 volcanoes across the Asia-Pacific region, aiming to calculate which ones were most likely to send ash drifting across the western part of the Ring of Fire.
Figuring out the eruption frequency of a given volcano might seem simple – take the number of times a volcano has gone off in the past and divide it by the time period you’re studying. In practice, though, this approach is fraught with pitfalls. Notably, it’s very hard to determine how often any volcano has erupted. Researchers tease this information out in various ways, such as by digging trenches to look for ash layers from past explosions, or by searching local archives for accounts of major blasts. But it’s more than possible for a major eruption to have occurred, comparatively recently, without leaving any written trace.
Evacuation routes for an eruption of Popocatépetl, Mexico, run through many small villages.
An unrecorded disaster of Tambora-like dimensions may in fact have happened in the year 1258. Volcanologists know that a VEI 7 eruption must have occurred at this time, because ice cores from both the Arctic and Antarctic show a spike in the amount of sulphur and ash in ice layers dating to that year or the year after. For eruption debris to have reached both poles, the volcano must have gone off somewhere in the tropics – that is, at low enough latitudes for ash and sulphur aerosols to be mixed through the atmosphere and across the equator.
An explosion of this size would have altered climate worldwide, and there seems to be evidence that just such a change did indeed happen. In 2012, a Museum of London archaeology team reported that 10,000-plus bodies found in a mass grave by East London’s Spitalfields Market might date to the year 1258. The scientists can’t pinpoint the exact date of the cemetery, but they have found documentary records of heavy rains, crop failure and famine around 1258, which does add support to the theory that the Londoners died in the aftermath of a colossal eruption.
But what volcano could have been responsible? Some of the top contenders have included El Chichón, in Mexico, and Ecuador’s Quilotoa, but the chemistry of their magma doesn’t match the ash and sulphur found in the ice cores from 1258. What now looks most likely is that the eruption happened in Indonesia, the planet’s most active volcanic region – specifically at the Rinjani volcano, in the Lesser Sunda Islands. Rinjani has an 8.5-kilometre-wide caldera that is known to have been formed some time in the thirteenth century.
It’s hard to believe that such a massive blast could have occurred, not all that long ago, and yet have left no mark in the historical record – and yet this appears to be what has happened. The mystery of the 1258 mega-explosion underscores our ignorance, and this is what is worrying. Who knows if another Indonesian volcano, dormant for centuries and unremarked, is ready to suddenly and calamitously explode?
Any tabulation of the world’s most dangerous volcanoes wouldn’t be complete without a visit to the supervolcanoes – those of VEI 8 or greater, which spew more than a thousand cubic kilometres of material into the sky. The biggest of these eruptions in the past few hundred thousand years was Toba, 74,000 years ago. The most recent was in New Zealand about 26,000 years ago, in the Taupo volcanic zone. That involved ten separate eruptions over several years, which ultimately buried most of New Zealand’s North Island in its volcanic vomit.
If such a supereruption were to occur in Trafalgar Square, it would bury Greater London 700 metres deep in ash. But it doesn’t really matter where exactly the volcano goes off: any supereruption would devastate the planet. Within weeks, the veil of erupted particles would screen out the sun, freezing and killing almost all vegetation. The searing blast would destroy most of the atmosphere’s protective ozone layer, exposing all surviving plants and animals to a flood of deadly ultraviolet radiation. In the longer term, the eruption’s sulphate aerosols would plunge the Earth into an unrelenting volcanic winter, lowering temperatures by as much as 10 degrees Celsius for a decade. There is no precedent for this kind of global natural disaster.
A supereruption occurs perhaps once every 50,000 years. Such an eruption would be what economists call a ‘black swan’ event – one that has an extreme impact on human lives but is almost impossible to predict. But improbability is of course not the same as impossibility. Think of the flooding of the Fukushima nuclear plant in Japan in March 2011, for example – a textbook ‘black swan’ disaster.
So what can we do? For starters, we can step up monitoring at plausible candidates for future supereruptions. Volcano monitoring got its start in 1841 at Vesuvius, when the King of Naples established the Osservatorio Vesuviano halfway up the volcano’s western slope. This was the only such scientific outpost for more than seven decades, until Thomas Jaggar established his at Kilauea in Hawaii. Today there are about 100 volcano observatories and research institutes worldwide, from the Philippines to Kamchatka to Alaska.
The backbone of volcano monitoring is seismology. Magma shifting in deep reservoirs causes the ground to move, a shift that can be detected by seismometers. Volcanic earthquakes are very different from ordinary earthquakes, though; around volcanoes they tend to come in swarms of tiny quakes, with magnitudes typically less than 2. You would never feel these quakes even if you were standing right on the volcano as it went off. The quakes also come in two classes: higher-frequency ones generated when magma moves and fractures rock, and lower-frequency ones that are usually caused by gas bubbles forming and popping in the magma. A low-frequency ‘tremor’ also often shows up before an eruption, probably generated by magma flowing within the ground.
The saucer-shaped object on top of the tripod is a GPS antenna that measures if the ground (here, at Yellowstone) is deforming and possibly indicating a future eruption.
All these signals are sent to scientists at the observatory, who then have to make a decision about what they actually mean. Sometimes, but not always, an earthquake swarm signals an impending eruption. If the high-frequency quakes suddenly disappear, that could be another sign that an eruption is imminent. And the energy seen in volcanic tremors, before an eruption starts, can indicate how much material is going to be released.
There are other ways to feel a volcano’s heartbeat. Global-positioning and other instruments measure changes in the shape of the ground. Gas-monitoring devices stuck into volcanic vents can record changes in the chemistry of volcanic gases. And satellites keep an eye on all the world’s volcanoes from the sky, sometimes providing the only evidence of very remote eruptions, thanks to an ash plume visible in satellite images.
Many of the world’s potential supervolcanoes, such as Yellowstone, are under this kind of close watch. None of them show any hint of unleashing a VEI 8 blast any time soon. Still, there are probably plenty of unknown candidates – especially, as noted, in Indonesia. If one of these underappreciated volcanoes decides to blow, scientists may not have much advance warning at all.
As if that weren’t enough to worry about, the chances of an eruption in colder parts of the world, such as Iceland, also rise every day, thanks to climate change. As Iceland’s ice has melted, its volcanoes have become more active, because the overlying weight of ice has been reduced. This has been going on since the last ice age ended around 12,000 years ago. Great ice sheets that had scraped southward into Europe and North America then retreated, and landscapes that had been buried by tonnes of ice began to rise. Parts of Scandinavia are still uplifting because of this phenomenon, known as postglacial rebound.
Superimposed on the natural rebound is the effect of human activity. Every
day, the burning of fossil fuels adds more heat-trapping greenhouse gases to the atmosphere. As a result, ice is melting all the faster. The great ice sheets atop Greenland and Antarctica are shedding fresh water into the oceans at an accelerating rate; their meltwater accounts for about one-third of the sea level rise seen in recent years. (Much of the rest of the rise comes from the fact that water expands as it gets warmer.)
Iceland, too, is melting. Since 1890, the island has lost 435 cubic kilometres of ice, primarily from the Vatnajökull ice cap. The loss of this ice is changing the geological stresses in the crust beneath, in ways that have altered how much magma gets made – it’s simple cork-and-champagne physics. Geologists estimate that the amount of magma produced beneath Iceland has increased thirty-fold since the end of the last ice age. In the past century alone, magma production rates may have gone up by as much as fifteen per cent. In other words, there is now more magma available to feed volcanoes such as Laki.
A Laki-style eruption, then, may be a far from improbable occurrence. Would it be a disaster? Compared to the global catastrophe of a supereruption, a VEI 4 eruption on the scale of Laki might seem almost tame. But a moderate-sized blast is far more likely to occur in the next few centuries than a Yellowstone-size behemoth, and the consequences of such an explosion – as we have seen – could be grave.
EPILOGUE
Return to Heimaey
THERE IS JUST ONE CHURCH on the tiny island of Heimaey, a simple white building with a charcoal-gray steeple. To reach it you turn your back to the water and your face toward a newborn volcano, and you walk uphill. On the evening of 22 March 1973, nearly everyone who was still on Heimaey made this walk.
The battle to save the island’s port was in top gear, and it was going badly. Spraying seawater on the advancing lava worked to cool it, but not as much as engineers had hoped. Shifts of workers pumped around the clock, and still the lava came. The islanders decided to appeal to a higher power. Thus came about the second Fire Mass.