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MOUNT ST. HELENSMount St. Helens' 1980 Eruption was rated at category 5 on the Volcanic Explosivity Index.Getty/InterNetwork Media

Small disturbances can eventually have immense consequences. In the namesake example of the butterfly effect, the vortex spun from a butterfly’s wing creates tiny changes in the atmosphere that result in a hurricane half a world away. While that’s theoretically possible, no one has yet tried to blame the insect world for triggering a cyclone.

But a strong link does exist between the small particles suspended high in Earth’s atmosphere, such as those spewed from erupting volcanoes, and the overall climate down at the planet’s surface. High-altitude aerosols, especially in large numbers, block sunlight from reaching the ground and scatter it back into space, thereby cooling the planet for months or even years (SN: 2/18/06, p. 110). The 1991 eruption of Mount Pinatubo in the Philippines, for example, caused the global average temperature to briefly drop about 0.4 degrees Celsius. The eruption of Indonesia’s Tambora in 1815 triggered agricultural failures in North America and Europe, caused the worst famine of the 19th century and cooled the planet so much that 1816 became known as “the year without a summer.”

While many eruptions in historic times caused real climatic changes, previously only Tambora had been linked to significant social disruptions, says Kenneth Verosub, a geophysicist at the University of California, Davis. Now, however, analyses by Verosub and colleague Jake Lippman suggest a connection between the 1600 eruption of Huaynaputina, a little-known peak in Peru, and one of the greatest famines ever to strike Russia.

“People have long known about the eruption and have long known about the famine, but no one has previously linked the two,” Verosub says.

Other volcanic eruptions of approximately Huaynaputina’s size or larger have occurred more recently, including Pinatubo in 1991 and Indonesia’s Krakatau in 1883, but they didn’t cool Earth as much and didn’t trigger societal upheavals. The reason, researchers say, may stem from the immense volumes of sulfur-rich fluids that fueled Huaynaputina’s eruption, which released an exceptional amount of planet-cooling aerosols.

Krakatau and Pinatubo also took place in a more industrialized world in which nations were more connected than they were when Tambora blew its top. So perhaps technology and globalization have rendered modern society more resilient to the effects of a worldwide catastrophe such as a massive volcanic eruption.

Unfortunately, though, overpopulation and humanity’s consumption of a large fraction of the world’s biological productivity mean that even today a large eruption could deal humanity a significant blow, some scientists say.

Trouble down south

The Andes, the world’s longest mountain chain, stretch along the western edge of South America and are chock-full of volcanoes. In February 1600, Huaynaputina, a relatively inconspicuous peak in southern Peru with no known history of eruption — in the local language, the name means “new volcano” — catastrophically exploded. The eruption, the largest in South America in written or oral history, lasted at least two weeks and belched as much as 12 cubic kilometers of ash, much of that spewing into the atmosphere during the first two days.

Avalanches of volcanic ash and hot boulders spilled east and southeast of the peak, and lahars — flows of ash and mud with the consistency of wet cement — destroyed several villages on the way to the Pacific coast, about 120 kilometers away. Significant quantities of ash smothered the region, says Charles Walker, a historian at UC Davis. “Some people didn’t see the sun for months, and agricultural production was devastated for the next two years,” he notes.

As many volcanic eruptions do, Huaynaputina lofted immense amounts of sulfur dioxide into the atmosphere. That gas reacts with water vapor in the air and then condenses into Earth-cooling droplets of sulfuric acid, which can destroy high-altitude ozone. Eventually the droplets are cleansed from the air by natural processes. The amount of sulfur-bearing compounds deposited on ice in Greenland and Antarctica in the months after the eruption suggests that Huaynaputina spewed between 16 million and 32 million metric tons of sulfur into the air, says Hannah Dietterich, a geologist at Pomona College in Claremont, Calif.

Most of that sulfur came not from the lava, but rather from pressurized fluids that accumulated in the volcano’s magma chamber before the eruption, she and her colleagues proposed in December 2007 at a meeting in San Francisco of the American Geophysical Union. Geochemical analyses of trace elements in the apatite minerals recovered recently from rocks made of Huaynaputina’s ash suggest that the magma could have contained no more than 4.1 million metric tons of sulfur. The tests also hint that as much as 5 percent of the material that erupted from the peak could have been fluid rich in sulfur dioxide, carbon dioxide and water — substances that, as they rose to Earth’s surface, would have violently expanded and fueled the eruption.

The big chill

Several studies indicate that the sulfur dioxide emissions from Huaynaputina were roughly comparable to those of Tambora. Therefore, says Verosub, the climatological consequences of the two volcanoes should be similar. Indeed, the chilling effects of Huaynaputina’s eruption in 1600 were substantial and were felt worldwide, he and Lippman report in the April 8 Eos.

To wit: Tree ring data gathered throughout the Northern Hemisphere indicate that 1601 was, on average, the coldest year out of the last 600. In Switzerland, 1600 and 1601 were among the coldest years between 1525 and 1860. In Estonia, the winter of 1601–1602 was the coldest in a 500-year period. In Latvia, the late date of ice breakup in the harbor at Riga indicates the winter was the worst in the 480 years before today. In Sweden, record amounts of snow in the winter of 1601 were followed in the spring by record floods. People around the world felt the effects of Huaynaputina’s changes to climate.

Through a chance meeting on an airplane, Verosub found that Huaynaputina may have triggered substantial social upheaval as well. While he chatted with a seatmate about his research on the effects of volcanic eruptions, a fellow seated in the row behind — Chester Dunning, a historian specializing in Russian history at Texas A&M University in College Station — overheard the conversation and introduced himself.

“So,” Verosub asked Dunning later in the chat, “did anything interesting happen in Russia in 1601?” The reply: “Oh, yeah. That was a terribly cold time in Russia.” That cold spell was just the beginning of the nation’s woes, Dunning continued.

Large portions of Russia received heavy rains in the summer of 1601, and by the end of the growing season it was clear that most crops would fail. In that age, Dunning explains, most farmers expected to occasionally experience a bad year and stockpiled accordingly, so farmers and their families didn’t suffer immediately. However, another agricultural failure the following year led to widespread starvation in both 1602 and 1603.

This lengthy famine — Russia’s worst, says Dunning — claimed the lives of an estimated 2 million people, or about one-third of the population, and more than 100,000 died in Moscow alone. Government inability to alleviate both the calamity and the subsequent unrest eventually led to the overthrow of Czar Boris Godunov, a defining event in Russian history.

Many volcanoes, besides killing local residents during their eruptions, have caused indirect deaths by triggering famines in the surrounding regions, says Lee Siebert, a volcanologist at the Smithsonian Institution in Washington, D.C. In 1783, for example, the clouds of volcanic ash and poisonous gases lofted during the eruption of Laki in Iceland killed more than half of the nation’s livestock, which in turn led to a food shortage that resulted in the death of about one-quarter of the population there. Also that year, an eruption of Asama, one of Japan’s most active volcanoes, may have contributed to a local famine that lasted four years and killed between 300,000 and 1 million Japanese, Siebert says.

The local and regional effects of volcanoes are common and often well-documented. However, the purported long-distance link between Huaynaputina and the subsequent famine and social unrest in Russia marks the only instance besides Tambora in which a specific volcano has been blamed for causing global misery, Verosub says.

Future shock?

In general, the larger the volcanic eruption, the bigger the cooling effect and the longer that effect lasts, sulfur content of its aerosols notwithstanding. Scientists categorize eruptions according to the Volcanic Explosivity Index, a parameter that depends on factors such as how much material is thrown from the peak and the height of the ash plume that’s produced.

The Huaynaputina eruption of 1600 falls into VEI category 6, which denotes an eruption with an ejecta volume greater than 10 cubic kilometers and a plume height that exceeds 25 kilometers. By comparison, Tambora has been tagged as a VEI category 7 eruption, which signifies an eruption that produces a similarly lofty ash plume but generates more than 100 cubic kilometers of ejecta.

Since 1601, there have been five category 6 eruptions, including Laki (1783), Krakatau (1883) and Pinatubo (1991). However, none of these events spawned adverse societal effects on a global scale as Huaynaputina did. In part, Huaynaputina’s sulfur-rich plume could have rendered the peak’s eruption inordinately powerful.

Climate at the time could have played a role as well, says Verosub: In 1600, the world was in the midst of the Little Ice Age, typified by harsh winters, springs and summers much cooler and wetter than normal, and shorter-than-average growing seasons. A large volcanic eruption during that period would have depressed average temperatures even further — adding insult to injury, as it were.

The demographics of the era also played a role, Dunning speculates. During the 1500s, the population in many regions had doubled, and as the century progressed, the proportion of young males had grown even faster. As a result, many of the younger sons of the late 1500s ended up not receiving their fathers’ land, jobs or titles, producing what Dunning terms “a surplus population of angry young men.” And in general, food production wasn’t keeping up with population growth.

By the 1590s, Dunning notes, many parts of the world were experiencing a wave of starvations, rebellions and unrest. Then, he adds, “at this most excruciating moment, this other thing comes along to take things where they’d never gone before.” None of the countries of early modern Europe were equipped to deal with such crises, Dunning says.

Is the situation any better today? Would modern technology and an increased global interconnectedness enable 21st century humans to better survive an immense, Earth-chilling eruption? Surprisingly, the answer to both questions may be no.

In the past, Verosub notes, most of a society’s foodstuffs were grown locally and in wide variety, so not every crop required the full growing season to mature. Therefore, any event that shortened a region’s growing season didn’t necessarily doom the entire harvest. Staples that formed the bulk of the diet were, for the most part, homegrown.

Today, on the other hand, most large-scale agricultural production focuses on a single crop that’s chosen to take full advantage of a region’s climate in order to realize maximum output — a severe disadvantage if the growing season is significantly trimmed by, say, a volcanic eruption.

Not only were preindustrial farming practices possibly more resilient to total agricultural failure, people then “were used to living on the margin,” Dunning says. “Everybody knew hunger … and the idea that you should plan for a bad year was ingrained in these societies.”

Today, by comparison, the world’s surplus food supply would last only about 90 days, a number that’s steadily dropping as population increases. Additional pressure on food, water and other resources in some nations, such as China, stem from a rapidly increasing standard of living and the resulting changes in dietary preferences (SN: 1/19/08, p. 36).

Humans are consuming an ever-increasing fraction of the biological productivity at the base of Earth’s food chain, in some regions almost two-thirds of the biomass that would be available if humans weren’t clearing forests, farming or otherwise occupying the land (SN: 10/13/07, p. 235). Rising population, plus the shift in some areas to divert agricultural production to produce inedible commodities such as ethanol, has led many to suggest a modern-day food crisis is at hand.

“What happens if another major eruption happens today?” Verosub asks. “If we lower the growing season globally, are we looking at a food crisis? … We’ve got a really stressed system, and if we hit it hard, is it going to collapse? I think that’s worth thinking about.”

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