by Bryan Walsh
In New England, 1816 was called the “Year Without a Summer,” or “Eighteen Hundred and Froze to Death.”38 Rainfall levels were abnormally high in much of Europe, and sodden harvests rotted in the fields. The ceiling of the Earth’s atmosphere actually dropped, chilling temperatures and causing further havoc with the weather. Albany, New York, experienced snow in June, and in Europe late spring snows fell brown and red, tainted by the ash cloud. The very sunset was altered, as the ash filtered the light into the fiery reds and oranges immortalized in the works of contemporary painters like the English artist J. M. W. Turner.39 Wood writes of the Scottish meteorologist George Mackenzie, who kept daily records of cloudy skies over the British isles in the first few decades of the nineteenth century. “In 1816, there wasn’t a single sunny day,” Wood told me. “Not a single one.”
Lord Byron was inspired by the Tambora gloom to write the poem “Darkness,” with the lines:
The bright sun was extinguish’d…
Morn came and went—and came, and brought no day.40
Of even greater literary value was Mary Shelley’s novel Frankenstein, written during that summer that wasn’t in 1816. Mary, her lover (and future husband) Percy Shelley, as well as Byron, his lover Clair Claremont, and his doctor John William Polidari were forced by the terrible weather to seek indoor pastimes at Byron’s villa on Lake Geneva in Switzerland. Byron proposed that the group entertain each other by composing ghost stories, and Mary Shelley’s Frankenstein—which would become a metaphor for another existential risk, the invention of artificial intelligence—was the result.
But if the well-off were inconvenienced by the endless cold and rain, the poor died in droves. Epidemics of typhus raged through Europe, with 100,000 people in Ireland dying from the disease.41 Crop yields in the British Isles fell by as much as 75 percent. In Switzerland—today one of the richest countries in the world—families starved en masse. In China peasants sucked on white clay to stave off hunger pangs, and some even sold their children as slaves, in hopes that their offspring would at least be given something to eat. There were worse fates than bondage, after all. “From Indonesia to Switzerland, people killed their children and themselves, rather than have their children face slow death from starvation,” said Wood. No wonder historians have characterized the years from 1816 to 1819 as the last great crisis of hunger to afflict the Western world.42
Beyond the art, and the death, Tambora reshaped global history. Migration to the United States accelerated—the number of European immigrants arriving at American ports in 1817 was more than double any previous year. Desperate farmers in New England abandoned their lands and moved west in search of a better climate, with Vermont alone in 1816 and 1817 losing some 10,000–15,000 emigrants, twice what had been the usual number.43 The sheer misery of the volcanic famine was so great that it may have helped encourage laissez-faire European governments to start actively responding to natural disasters. “It was the beginning of the realization that a responsibility of government is to care for citizens in times of crisis,” said Wood. “We take it for granted but that principle did not exist at all.”
The history of the Year Without a Summer makes for horrifying and fascinating reading, but what matters is this question: would our world suffer the same fate if another VEI 7 volcano of the size and scale of Tambora were to erupt—let alone a supervolcano?
In some ways we’d clearly be better off. In 1815 most of humanity still made their living as subsistence farmers, which left them vulnerable to the failure of a single harvest. Global trade was limited, so there was no easy way to ship food from places that were less affected by volcanic cold to those in dire need. There was no Red Cross, no World Health Organization, no world anything. The institutions and the wealth that cushion the world today—or at least the developed world—from even the worst natural disasters did not exist.
But as rich and as technologically advanced as we are, there are some aspects of life in 2019 that would make us more vulnerable than our ancestors to the shock of a global volcanic eruption. Global trade could help cushion the blow, but it depends in part on aviation, and as we saw after the 2010 eruption of Eyjafjallajökull in Iceland, even a minor volcano with a VEI score of just 4 can bring air travel to a halt should it strike at the wrong time and the wrong place. Volcanic ash can be as toxic to jet engines as it is to lungs, and Eyjafjallajökull grounded airlines in Europe for days, costing the global economy nearly $5 billion.44
The wealth that globalization has created has also led to specialization, magnifying the misery caused by any lengthy disruption in trade. My great-great-great-great grandfather in Ireland would have known how to grow his own food, because he had to. I do not. “Even an eruption on the scale of Tambora could cause real problems,” said Bill McGuire, a British volcanologist and natural disaster expert. “This is especially worrying as such events may happen as frequently as every several hundred years.”
Human history has repeatedly been marked by volcanic eruptions around the size of Tambora. In 1257, the Samalas volcano erupted on Lombok island in Indonesia, dampening global temperatures and helping to usher in what is known as the Little Ice Age, a period of unusual cooling that lasted from the fourteenth century into the 1800s. As happened after Tambora, cold weather and heavy rains ruined harvests in Europe; archeologists in England discovered mass graves with more than ten thousand skeletons dating back to the year after the eruption. One English monk in 1258 recorded that the year was marked by “such unendurable cold, that it bound up the face of the earth, sorely afflicted the poor, suspended all cultivation.” Some historians have even suggested that the climatic change triggered by Samalas hastened the decline of both Byzantium in Eastern Europe and the Mongol Empire in Asia.45
Scientists have connected even older volcanic eruptions to reductions in the flow of the Nile River, which in turn may have triggered political revolts and war in Ptolemaic Egypt.46 In 2018 the journal Science named AD 536 the “worst year to be alive,” largely because a massive volcanic eruption in Iceland that year caused temperatures to fall even more than they did after Tambora, leading to widespread famines, starvation, and even the terrible Plague of Justinian, an infectious disease that killed up to half the population of the eastern Roman Empire and sped its decline.47 “You have political disturbances that seem to come out of nowhere, but are connected to volcanic eruptions,” said David Pyle, a volcanologist at the University of Oxford. “That suggests there could be quite dramatic impacts in terms of the changes wrought by volcanoes.”
In 2018, Alan Robock, along with Stephen Self and Chris Newhall—two veteran volcanologists who created the VEI scale—publicly warned that the world was utterly unprepared for Tambora- and Samalas-scale volcanos.48 Just as few in Indonesia or Sri Lanka feared the threat of major tsunamis before December 26, 2004, because none had occurred in memory, the world has done little to prepare for a VEI 7 volcanic eruption because we have no ready experience of one. But Tambora erupted a little more than two hundred years ago—beyond our living memory, but virtually concurrent in geologic terms. VEI 7 eruptions seem to happen on average every few hundred years, which means it may not be long before another occurs. Yet the threat barely registers. “We have to overcome that human tendency to not want to deal with problems until they are painfully obvious,” Newhall told me.
What Tambora and the other eruptions of its class teach us is that volcanoes can have global effects, ones that continue well after the volcano itself has fallen silent. A volcanic change to the climate can cause starvation, massive refugee flows, even political revolts. We can’t prevent a volcano from erupting—at least not yet. But we can control how our society responds to the shock of a catastrophe, be it a supervolcano or another existential threat. “Tambora was an object lesson in how human systems affect the severity of human outcomes that result from a climatic crisis,” said Wood. “The extremity of the natural event met the vulnerability of the human community. The result was disaster.”
Will we fare better when our time comes? And what happens if that test is even bigger than what followed Tambora?
Michael Poland is the scientist-in-charge at the USGS’s Yellowstone Volcano Observatory, and he wanted me to know this much: he is not trying to cover up the end of the world. As well as being America’s first national park, Yellowstone is home to the most notorious supervolcano in the world. The volcanic system has produced three supereruptions over the past 2.1 million years, and Yellowstone is still highly active, as the park’s dazzling array of geysers demonstrate on a daily basis for the more than four million people who visit each year.49 So when Yellowstone experienced a swarm of hundreds of minor earthquakes in the summer of 2017, it drew the attention of the media and conspiracy theorists alike. It was Poland’s job as Yellowstone’s top volcanologist to assure anyone who asked that, no, the earthquakes did not mean that a world-ending supereruption was nigh. Which isn’t to say that he convinced everyone. “There’s always a significant part of the population that wants to believe the worst,” Poland said.
In the case of Yellowstone, the worst would be like nothing the planet has experienced for tens of thousands of years. Yellowstone sits atop a volcanic hot spot, a long plume of magma that rises up from deep inside the Earth’s mantle, like water being squeezed up a straw. That magma fills a shallow cauldron of molten rock just beneath the surface, a process that causes the ground in Yellowstone to rise and fall perceptibly, as if the Earth itself were breathing. When that magma reservoir fills to capacity, Yellowstone can blow. In the center of the park is a caldera, like the one that now forms Lake Toba in Indonesia, measuring 28 miles by 47 miles.50 It is the hole left by Yellowstone’s last supereruption some 640,000 years ago, which disgorged an estimated 240 cubic miles of volcanic material. Lava alone spread across some 1,700 square miles during that eruption, an area larger than the state of Rhode Island. Deposits of volcanic ash from the eruption have been found as far afield as present-day Iowa, Louisiana, and California.51
The magma reservoir beneath Yellowstone is filling again even now, and one day America’s first national park could become its first supervolcano.52 First would come a swarm of increasingly intense earthquakes, a sign that magma was rushing toward the surface. The pressure would build until, like champagne in a bottle given a vigorous shake, the magma would burst through the ground in a titanic eruption that would discharge the toxic innards of the Earth to the air. It would continue for days, burying Yellowstone in lava within a forty-mile radius of the eruption.
These earthquakes should fortunately give visitors and workers weeks of warnings, permitting time to evacuate the park. (That’s why the Yellowstone Volcano Observatory is more properly an earthquake observatory.) Yellowstone as we know it, though, would cease to exist. But as with past supereruptions, the true existential threat would come from the ash, lava, and volcanic gases that would shoot upward with a force equal to a thousand Hiroshima-sized nuclear bombs,53 sufficient to reach a height of fifteen miles or more.
The USGS volcanologist Larry Mastin modeled a Yellowstone supereruption and found that the northern Rockies could be buried in up to three feet of volcanic ash, smothering large swaths of Colorado, Wyoming, and Utah. Depending on the prevailing weather patterns, much of the Midwest would receive a few inches of ash, which would fall like black rain, plunging the region into darkness. Even the coasts—where the majority of Americans live—would likely see a dusting as the vast ash cloud spread out like an unfolding umbrella in the days following the eruption.54 “What Yellowstone could produce looks almost like a hurricane, something that is almost continental in size,” said Mastin.
Raging lava may be the volcanic showstopper, but ash is how a supereruption kills. Volcanic ash is not like the burnt-out embers of a campfire, or the bits that fall from the end of a cigarette. It is hard and abrasive, made up of tiny, jagged pieces of pulverized rock and glass. The ash is corrosive to living tissue, and in the aftermath of a Yellowstone supereruption, hospitals would be choked with victims coughing up blood as the silicate in the ash slashed at their lungs.
“Drowning in a liquid form of concrete” is how Marie Jones and John Savino put it in their book Supervolcano.55 Those who avoided the ash in the air would still struggle to find uncontaminated water. Volcanic ash isn’t soluble, so if ash-laden sewage enters a treatment plant, it will act as a wrecking ball, shredding mechanical equipment and stopping up biological reactors.
Accumulated volcanic ash is also heavy, and in the states closest to Yellowstone, buildings would collapse beneath the weight, just as snow from a blizzard can cave in roofs. But collapse would require only four inches of accumulated volcanic ash, far less than what will fall in the aftermath of a supereruption.56 Ashfall will bring down power and telephone lines and ruin power plants. It could even fully collapse the grid by destroying the transformers that are the backbone of the electricity distribution system. While downed power lines can be restored in a matter of hours, it can take as long as two years to order and install a replacement for a single damaged electrical transformer.57 If Yellowstone’s ashfall managed to knock out a significant share of America’s 2,100 electrical transformers, vast swaths of the country could be in the dark for a very, very long time.
Even as we grappled with a prolonged and widespread blackout, our food system might be crippled. More than a few inches of ashfall can kill crops in the fields. If Yellowstone were to erupt during the spring or summer, an entire season’s worth of midwestern corn or soybeans could be wiped out in a few days. Depending on how much poisonous fluoride is contained in the ash, pastureland could contaminated by as little as 1/32nd of an inch of ash. Any livestock that fed on the grass could die horribly from gastrointestinal blockage, while those that survived would eventually die of starvation or thirst.58 Even the earth itself would be poisoned. It could take generations before soil buried in more than four inches of ash could be restored to fertility. Oh, and aviation across the country would probably be grounded for weeks or longer, although with the blackouts and the food shortages and the air pollution, canceled flights would be the least of our concerns.
A FEMA estimate pegged the total damage to the United States from a Yellowstone supervolcano at $3 trillion, some 16 percent of the country’s GDP.59 That would be almost twenty times more than Hurricane Katrina, the most expensive natural disaster in American history, which cost $125 billion and resulted in the deaths of nearly two thousand Americans.60 But it’s guesswork to put a dollar figure on something as catastrophic as a Yellowstone supereruption, in part because it would be the first truly continental-scale disaster this country has ever experienced. In every past catastrophe—hurricanes, earthquakes, floods—most of the United States remained untouched, which meant safe parts could divert aid to and take in refugees from affected regions. But no corner of the continental United States would be exempt from the effects of a supervolcano. “If Yellowstone erupts, with the ash fallout, you’re looking at the eradication of most of the Midwest and the U.S.A.,” said John Grattan, an archeologist and disaster expert at Aberystwyth University in Wales. “It will be incredibly dramatic, something beyond the scale of government.”
It will also be felt well beyond the United States. Half of the world’s cereal grains are produced on North American farmland, and losing much of the Midwest farm belt, even temporarily, could mean global famine.61 Take $3 trillion or more out of the U.S. economy and you have a recipe for a financial crash that would make the Great Depression look like a mild bump.
The most lasting effect of a Yellowstone supervolcano, however, would be on the global climate. In 2006, Claudia Timmreck and Hans-F. Graf modeled the climatic effects of a Yellowstone-like supereruption. They reported that aerosols from the volcano could spread globally if the eruption occurred during the summer. Over the short term, as the cloud of aerosols from Yellowstone blocked sunlight, global average temperatures could plunge as much as 18 degrees and not return to normal for as long as
a decade.62 Rainfall would decline significantly; along with the cooling, that might be enough to trigger a drastic die-off of tropical rain forests. The planet’s most productive wildlife habitats would be annihilated and billions of tons of carbon that are stored in those trees would be released into the atmosphere. That would accelerate global warming—though not, unfortunately, in time to counter the volcanic winter.
The world has less than two and a half months of estimated food reserves,63 so we could quickly find ourselves in a race against global starvation. The 800 million people who are already hungry might be the first to die,64 but no part of the planet would remain unscathed. It would be, as Hans-Peter Plag wrote in a 2015 report for the European Science Foundation, “the greatest catastrophe since the dawn of civilisation.”65 There’s a reason why a 2017 survey by Oxford’s FHI listed supervolcanoes as the single natural existential threat that poses the highest probability of human extinction.66 “This is absolutely an existential risk,” said Oxford’s David Pyle. “The sheer knockout effects, the cascade of disruption, would be mind-blowing.”
You may now be asking yourself: what are the chances that this mind-blowing, knockout catastrophe is going to happen? This is where geologic time scales work in our favor. The probability of a supereruption at Yellowstone in any given year is 1 in 730,000, or 0.00014 percent.67 We’re closer to Yellowstone’s next supereruption than we are distant, but that day—should it come—is likely still tens or even hundreds of thousands of years away. It’s also possible that the threat from Yellowstone could be receding. As the North American tectonic plate slowly shifts, the magma hot spot that powers the Yellowstone volcanic system is beginning to encounter thicker and colder rocks that take more energy to burn through, which would forestall or even eliminate the chance of an eruption.
