The Year Without Summer: 1816 and the Volcano That Darkened the World and Changed History
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By this time, Tambora’s umbrella ash cloud extended for more than three hundred miles at its widest point. As the cloud spread, the heavier clumps of ash within it drifted to the ground, but the rest remained aloft. “The ashes now began to fall in showers,” the ship’s captain wrote, “and the appearance altogether was truly awful and alarming.” By noon, the darkness was complete, and the rain of ash—which one sailor described as a tasteless “perfect impalpable powder or dust” that gave off a vaguely burnt odor—covered every surface on the ship. “The darkness was so profound throughout the remainder of the day,” continued the commander, “that I never saw any thing equal to it in the darkest night; it was impossible to see your hand when held up close to the eye.” Ash continued to fall throughout the evening; despite the captain’s efforts to cover the deck with awnings, the particles piled as much as a foot high on many surfaces. At six o’clock the following morning, there was still no sign of the sun, but the accumulated weight of the ash—which one officer estimated at several tons—forced the crew to begin tossing the powder overboard. Finally by noon on April 12, a faint light broke through, and the captain was struck by the thought that the Benares resembled nothing more than a giant calcified pumice stone. For the next three days, however, he noted that “the atmosphere still continued very thick and dusky from the ashes that remained suspended, the rays of the sun scarce able to penetrate through it, with little or no wind the whole time.”
A Malaysian ship from Timor sailing through the region also found itself in “utter darkness” on April 11. As it passed by Tambora, the commander saw that the lower part of the mountain was still in flames. Landing farther down the coast to search for fresh water, he found the ground “covered with ashes to the depth of three feet,” and many of the inhabitants dead. When the ship departed on a strong westward current, it had to zigzag through a mass of cinders floating on the sea, more than a foot thick and several miles across.
On the island of Sumatra, over a thousand miles west of Tambora, local chieftains heard the explosions on the morning of April 11. Fearing a conflict had broken out between rival villages, they hurried down to Fort Marlborough, the British encampment in Bengkulu. Other tribal chieftains on Sumatra and the neighboring islands also assumed the sounds presaged some sort of invasion, but once they received reassurance on that score, they ascribed the explosions to supernatural causes. “Our chiefs here,” reported an official at Fort Marlborough, “decided that it was only a contest between Jin (the very devil), with some of his awkward squad, and the manes of their departed ancestors, who had passed their period of probation in the mountains, and were in progress towards paradise.”
At Gresik on eastern Java, natives decided that the blasts were the “supernatural artillery” of the venerated South Java Sea spirit queen Nyai Loroh Kidul, fired to celebrate the marriage of one of her children; the ash was “the dregs of her ammunition.” If so, her ammunition made most of April 12 utterly dark in the village. When the British resident in Gresik awoke that morning, he had the impression that he had slept through a very long night. Reading his watch by lamplight, he discovered that it was 8:30 A.M., and pitch-black outside from the cloud of ashes descending. He breakfasted by candlelight at 11:00 and thought he could see a faint glimmering of light, but at 5 P.M. he still could “neither read nor write without candle.” In the nearby village of Sumenep, ash fell about two inches thick, and “the trees also were loaded with it.”
A tsunami reached eastern Java around midnight on April 10–11, and tremors struck the central region of the island eighteen hours after the eruption. Between two and three in the afternoon of April 11, a European observer in the village of Surakarta (Solo) noticed “a tremulous motion of the earth, distinctly indicated by the tremor of large window frames; another comparatively violent explosion occurred late in the afternoon.… The atmosphere appeared to be loaded with a thick vapour: the Sun was rarely visible, and only at short intervals appearing very obscurely behind a semitransparent substance.” Surakarta remained in darkness for much of the following day, as well. Raffles, too, reported that even at a distance of eight hundred miles, “showers of ashes covered the houses, the streets, and the fields, to the depth of several inches; and amid this darkness explosions were heard at intervals, like the report of artillery or the noise of distant thunder.”
Twenty-four hours after Tambora erupted, the ash cloud had expanded to cover an area approximately the size of Australia. Air temperatures in the region plunged dramatically, perhaps as much as twenty degrees Fahrenheit. Then a light southeasterly breeze sprang up, and over the next several days most of the ash cloud drifted over the islands west and northwest of Tambora. By the time the cloud finally departed, villages within twenty miles of the volcano were covered with ash nearly forty inches thick; those a hundred miles away found eight to ten inches of ash on the ground.
Even a small quantity of ash could devastate plants and wildlife. One district that received about one-and-a-quarter inch of ash discovered that its crops were “completely beaten down and covered by it.” Dead fish floated on the surfaces of ponds, and scores of small birds lay dead on the ground.
By the time the volcano finally subsided, Tambora had released an estimated one hundred cubic kilometers of molten rock as ash and pumice—enough to cover a square area one hundred miles on each side to a depth of almost twelve feet—making it the largest known volcanic eruption in the past 2,000 years. Geologists measure eruptions by the Volcanic Explosivity Index, which uses whole numbers from 0 to 8 to rate the relative amount of ash, dust, and sulphur a volcano throws into the atmosphere. Like the Richter Scale for earthquakes, each step along the Explosivity Index is equal to a tenfold increase in the magnitude of the eruption. Tambora merits an Index score of 7, making the eruption approximately one thousand times more powerful than the Icelandic volcano Eyjafjallajökull, which disrupted trans-Atlantic air travel in 2010 but rated only a 4; one hundred times stronger than Mount St. Helens (a 5); and ten times more powerful than Krakatoa (a 6). Only four other eruptions in the last hundred centuries have reached a score of 7. Modern scientists identify and measure past eruptions using layers of volcanic debris found in ice cores, lake sediments, and other undisturbed soils. Each eruption has a distinct chemical signature that, along with conventional methods of carbon dating, can be used to associate each layer of volcanic material with a particular eruption.
It was also by far the deadliest eruption in recorded history. As soon as the volcano quieted, Raffles ordered the British residents to make a survey of their districts to ascertain the extent of the damage. The reports that reached him detailed a horrific picture.
Before the eruption, more than twelve thousand natives lived in the immediate vicinity of Tambora. They never had a chance to escape. Nearly all of them died within the first twenty-four hours, mostly from ash falls and pyroclastic flows—rapidly moving streams of partially liquefied rock and superheated gas at temperatures up to 1,000 degrees, hot enough to melt glass. Carbonized remains of villagers caught unaware were buried beneath the lava; fewer than one hundred people survived. “The trees and herbage of every description, along the whole of the north and west sides of the peninsula,” reported one British official, “have been completely destroyed.” Another found that in the area surrounding Mount Tambora, “the cattle and inhabitants were nearly all of them destroyed … and those who survived were in such a state of deplorable starvation, that they would unavoidably share the same fate.” One village had sunk entirely, its former site now covered by more than three fathoms (eighteen feet) of water. And the Raja of Sanggar confirmed that “the whole of his country was entirely desolate, and the crops destroyed.” The survivors of his village were living on coconuts, but even the supply of that food was nearly exhausted.
On April 19, the Benares reached Bima. The coastline was barely recognizable; what had been one of the most beautiful and regular harbors in Asia now was an obstacle course, littered with masses of
black pumice stone, tree trunks burnt and splintered as if by lightning, and the prows of previously sunken ships which the ocean had thrown onto land. The village had only a small supply of rice to stave off starvation. When the Benares departed several days later, it sailed past Mount Tambora, which had been one of the highest peaks in the archipelago, often used by sailors as a landmark. Clouds of smoke and ash still obscured the volcano’s peak. Even at a distance of six miles, sailors could see patches of lava steaming along the mountainside.
A heavy rainstorm on April 17 had left the air cleaner and cooler, and probably saved a substantial number of lives on the more distant islands as the rain washed the ash off crops and provided fresh drinking water to help stem an incipient epidemic of fever. But nothing could save those closer to Tambora. Over the following month, thousands more perished—some from severe respiratory infections from the ash that remained in the atmosphere in the aftermath of the eruption, others from violent diarrhoeal disease, the result of drinking water contaminated with acidic ash. The same deadly ash poisoned crops, especially the vital rice fields, raising the death toll higher. Horses and cattle perished by the hundreds, mainly from a lack of forage. Lieutenant Owen Phillips, dispatched by Raffles to investigate conditions and provide an emergency supply of rice to the inhabitants, arrived in Bima several weeks after the eruption and reported that “the extreme misery to which the inhabitants have been reduced is shocking to behold. There were still on the road side the remains of several corpses, and the marks of where many others had been interred: the villages almost entirely deserted and the houses fallen down, the surviving inhabitants having dispersed in search of food.” In the nearby village of Dompo, residents were reduced to eating stalks of papaya and plantain, and the heads of palm. Even the Raja of Sanggar lost a daughter to hunger.
In the end, perhaps another seventy to eighty thousand people died from starvation or disease caused by the eruption, bringing the death toll to nearly ninety thousand in Indonesia alone. No other volcanic explosion in history has come close to wreaking disaster of that magnitude.
And yet there would be more casualties from Tambora. In addition to millions of tons of ash, the force of the eruption threw 55 million tons of sulfur-dioxide gas more than twenty miles into the air, into the stratosphere. There, the sulfur dioxide rapidly combined with readily available hydroxide gas—which, in liquid form, is commonly known as hydrogen peroxide—to form more than 100 million tons of sulfuric acid. The sulfuric acid condensed into minute droplets—each two hundred times finer than the width of a human hair—that could easily remain suspended in the air as an aerosol cloud. The strong stratospheric jet streams quickly accelerated the particles to a velocity of about sixty miles per hour, blowing primarily in an east-to-west direction. The sheer power of the jet stream allowed the aerosol cloud to circumnavigate Earth in two weeks; but the cloud did not remain coherent.
Variations in the wind speed and the weight of the particles caused some parts of the cloud to travel faster or slower than others, and so the cloud spread as it moved around Earth, until it covered the equator with an almost imperceptible veil of dust and sulfurous particles. It also began to spread north and south, albeit far more slowly. While it took only two weeks for the aerosol cloud to cover the globe at the equator, it was likely more than two months before it reached the North and South Poles.
Rather than a slow, steady broadening of the equatorial cloud into the Northern and Southern Hemispheres, the cloud expanded in fits and starts. As some pieces of the cloud were blown away from the equator, they were quickly caught up in the dominant stratospheric jet streams—which in May blow east to west in the Northern Hemisphere, and west to east in the Southern Hemisphere. The cloud soon began to resemble streamers or filaments, with small portions regularly pushed off the equator and into the middle latitudes in each hemisphere. Eventually, these filaments coalesced into a single, coherent cloud that covered Earth.
And there they remained. Had the aerosol cloud ascended only into the lowest part of the atmosphere, the troposphere, where clouds form, rain would soon have cleansed the ash from the air. But in the more stable stratosphere, conditions mitigate against the formation of clouds of water droplets. The coldest air already is at the bottom of the stratosphere, with warmer air above it, so air rarely rises from the troposphere into the stratosphere. With no rising plumes of warm air to carry moisture into the stratosphere, clouds almost never form; the stratosphere is drier than most deserts. With no clouds, there could be no rain to wash away the stratospheric aerosol veil. Only the slow action of gravity and the occasional circulation of air between the stratosphere and the troposphere could drag the droplets back to the earth. And so the extraordinarily fine sulfur particles from Tambora that reached the stratosphere remained suspended in the air for years, freely transported around the globe by the winds. By the winter of 1815–16, the nearly invisible veil of ash covered the globe, reflecting sunlight, cooling temperatures, and wreaking havoc on weather patterns.
2.
PORTENTS
“The country has all the appearance of the middle of winter…”
FROM TERAMO IN central Italy, near the Adriatic coast, came reports in late December 1815 of “the heaviest snow ever known in that country.” According to one account, over a six-hour period “a greater quantity of snow [fell] than has been known in the memory of man.” More astonishing was the nature of the precipitation. The snow “was of a red and yellow color … [which] excited great fear and apprehension in the people.” Believing that “something extraordinary has taken place in the air,” the local residents organized religious processions to placate God; in the meantime, provincial authorities summoned a professor of physical science from Parma (who was also a Jesuit priest) to study the phenomenon. For the rest of the winter, the Abruzzo region remained cold, with significantly more snow and freezing rain than usual.
Several weeks later, an intense blizzard raged across northeastern Hungary for two days. The snow reportedly covered houses to the rooftops, and killed more than ten thousand sheep and hundreds of oxen. Despite the magnitude of the storm, news accounts focused primarily on the fact that “the snow was not white, but brown or flesh colored.” April brought reports of another colored snowfall in Italy, this time around the Tonale Pass, in the Italian Alps: “It was brick red and left an earthy powder, very light and impalpable, unctuous to the touch … [with an] astringent taste.” The colored snow almost certainly was the result of ice droplets forming with ash particles from Tambora as their nuclei. The deepest clouds associated with severe storms occasionally are able to reach into the stratosphere, which is consistent with the colored snow falling in particularly extreme weather events. Over the course of months—and, in this case, years—gravity also slowly dragged the stratospheric sulfur particles into the upper reaches of the troposphere, where the particles could more easily form the centers of ice crystals.
No contemporary accounts appear to have made the connection between the phenomenon of colored snow in Italy and Hungary and the eruption of Mount Tambora nearly halfway around the world, although reports of Tambora had reached London by the end of 1815, and a few amateur scientists—most famously Benjamin Franklin—had previously essayed a connection between volcanic eruptions and unusual atmospheric conditions. Following the eight-month-long eruption of Laki in southern Iceland in June 1783, Europe and North America experienced highly unusual weather, including a persistent dry haze during the summer and an extremely cold and snowy winter that killed thousands of people across Europe. Although Franklin, who was living in Europe at the time, acknowledged in a 1784 lecture to the Manchester Literary and Philosophical Association that “the cause of this universal fog is not yet ascertained,” he suggested that it may have been “the vast quantity of smoke, long continuing, to issue during the summer [from Laki] … which smoke might be spread by various winds, over the northern part of the world.” And the frigid temperatures, he proposed, probably resu
lted from this fog blocking the rays of the sun, thereby reducing the amount of solar energy that reached Earth.
Throughout the winter of 1815–16, the spreading aerosol cloud from Mount Tambora had been doing precisely that: cooling global temperatures by reflecting and scattering sunlight. Although the cloud reflected only one half to one percent of the incoming energy, it reduced the Northern Hemisphere average temperature in 1816 by about three degrees Fahrenheit. This seemingly small cooling had a considerable impact on global weather patterns, with devastating consequences for agriculture on both sides of the Atlantic. Ironically, however, the effects of Tambora’s aerosol cloud could have been far worse if the eruption had been slightly weaker. While immense in size and scope, Tambora’s aerosol cloud was not particularly efficient at reflecting sunlight. Stronger volcanic eruptions tend to eject more sulfur dioxide into the stratosphere than weaker eruptions, which leads to more sulfuric acid droplets within the same volume of atmospheric gases. A greater number of droplets increases the chance that droplets will meet and collide, forming larger droplets that will be removed more quickly from the stratosphere by gravity. A single, larger droplet also has less total surface area than two smaller droplets, and so is less effective at scattering sunlight. There is therefore a balance to be struck between eruptions that are too weak to penetrate into the stratosphere—and so produce small, short-lived cooling—and eruptions that produce large, less effective sulfuric acid droplets. By measuring the remnants of Tambora’s aerosol cloud in ice cores and lake sediments, modern scientists have determined that the climatic consequences—while undoubtedly devastating—could have been far worse if the particles had been roughly half their size.
Unlike the sudden drop in temperatures in the Indonesian archipelago that occurred immediately after the eruption of Mount Tambora, the planet-wide cooling was a gradual process that took up to a year to be fully realized. While air temperatures can, and frequently do, change rapidly in response to variations in solar energy, soil and ocean temperatures adjust much more slowly. The land and sea possess considerable capacity to store heat, while the atmosphere has practically no storage. When the atmosphere is cooler than the land and sea, heat will flow from these reservoirs back into the air; but since the air cannot store heat for long, much of this is soon lost to space. If, on the other hand, the atmosphere is warmer, some of that excess heat will be stored in soil and water until a balance is reached. This process may be seen clearly in summer: The warmest weather often occurs not in June, when the sun is strongest, but in August, when the ocean and land have warmed.