Tambora: The Eruption That Changed the World (24 page)

The prospect of a greater glaciated Alps upset Shelley, whose feelings of excited wonder on first entering the valley now gave way to creeping dread. Observing the lines of forest trees flattened by the encroaching tongue of the Bossons glacier, Shelley found “something inexpressibly dreadful in the aspect of the few branchless trunks which nearest to the ice rifts still stand in uprooted soil. The meadows perish overwhelmed with sand & stones. Within this last year these glaciers have advanced three hundred feet into the valley.”
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The sight of the expanding glacier brought still another reference to Shelley’s encyclopedic mind. The esteemed French naturalist the Comte de Buffon had proposed that “this earth which we inhabit will at some future period be changed into a mass of frost”—in other words, an Ice Age, though it would be another two decades before that term—foundational to modern climate science—was invented. To trace the origins of Ice Age theory to Tambora-era glaciation is the purpose of this chapter.

Shelley’s intuition of Alpine danger in 1816 should be tied to the specific climatic conditions of that cold Tamboran summer, in which the glaciers neared their modern historical maximum and appeared grimly unstoppable: “The race / Of man, flies far in dread,” he wrote. But what Shelley could not have known was that his fears, in the geological short term, were needless. The icy augmentation Shelley was witness to, wrought by Tambora’s chilling hand, represented the southernmost glacial extent of the Little Ice Age. The glaciers of the Mont Blanc massif would never again extend so far as they did for the Shelleys in the Tamboran period.
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Two centuries later, our perception of an Alpine crisis is, of course, very different. With the accelerated global warming of the past half century, Alpine glaciers are now in unprecedentedly rapid retreat, raising the very real prospect of an ice-free Europe by century’s end, with disastrous implications for continent-wide water systems and agriculture.

Meanwhile, back at the hotel in Chamonix, Mary Shelley’s imagination was far from idle. She considered the Alps “the most desolate place in the world,” which, coming from a true-born Romantic, was high praise indeed.
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Their walking tour of Mont Blanc’s northside glacier, the Mer de Glace, had put her in mind of the ghost story competition with Byron and Shelley. She was inspired to “write my story,” as she confided to her journal, and now had a setting for the opening of book 2 where she would reunite the unfortunate monster, lately a murderer on the run, with his unhappy creator. In one of the most gripping scenes of the novel, Frankenstein embarks on his Alpine tour with the hope of discovering in the majestic stillness of the mountains some escape from his grief and regret: “My heart, which was before sorrowful, now swelled with something like joy.” Instead, he finds that the glaciers have become the refuge of his hideous Creature, who waylays him on the vast tundra of the Mer de Glace: “I suddenly beheld the figure of a man, advancing toward me with superhuman speed. He bounded over the crevices in the ice.”
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Mary Shelley’s staged gothic encounter on the Alps in
Frankenstein
echoes Percy’s ambivalence in his poem “Mont Blanc.” Both detect in the sublime beauty of the glaciated peaks an undercurrent of horror.

The Shelleys were not alone in their dread of advancing Alpine glaciers in the waning years of the 1810s. The members of the new Swiss Society for Natural Science, alarmed that the widespread glacial growth of that decade had accelerated markedly on account of the recent cold summers, turned their attention to glaciology for the first time in their annual meeting in Bern in 1816. The following year they announced a new competition. A prize was to be awarded to the scientist who conclusively answered the question of whether the climate of the Swiss Alps had grown colder. In addition, applicants were required to provide their observations on the growth and decay of glaciers. Three years later, however, the society had received a total of one mediocre submission, a testament not to lack of interest in the question but to its difficulty.

Enter Ignace Venetz, a gifted young engineer and montagnard from the Swiss canton of Valais, who followed the Shelleys’ footsteps along the tourist trails of Mont Blanc in the summer of 1820.
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His impression of a glaciated Alps was as powerful as Shelley’s, but his educated eye was better able to decode their ice-bound history through the specific evidence of moraines. Buried beneath swaths of forest, or winding sinuously miles from the present glacial rim and snow line, these riverine piles of rock and earthy debris marked the ghostly outline of the massive glaciers of the past. In his seminal paper of the following year, “Mémoire sur les variations de la température dans les Alpes de la Suisse,” delivered to the Swiss Society, Venetz laid down the founding principles of Ice Age theory. Only historical variations in temperature could explain the changes in glacial extent, he argued. Furthermore, these changes in climate were extreme enough to have once submerged this region of the Swiss Alps beneath a vast sheet of ice, whose subsequent retreat under warmer temperatures had left behind the moraines and striated rocks as a kind of glaciological signature.

The theoretical possibility of large-scale glaciation had been suggested intermittently over the previous decades by scientists in various countries, only to be ignored. Venetz was the first to make a serious case based on geological observation, and the first to make the necessary link between glaciation and climate change. Venetz’s career as a pioneering glaciologist was marked by a lifelong devotion to on-site study in the Alps, but also frustratingly few publications. It is possible, nevertheless, to show that the evolution of his theory of the Ice Age, and its breakthrough revelation, occurred in the course of a specific Swiss crisis during the Tamboran summers of 1816–18, when the multiplying spin-offs of sustained climate deterioration threatened lives and livelihoods across the Alps.

DOOMSDAY IN THE VAL DE BAGNES

Two years after Shelleys’ tour of Mont Blanc, in the spring of 1818, the residents of the Val de Bagnes, forty kilometers to the east along the same mountain range, confronted a chilling sight. The River Dranse, their major water source, which ought to have been swollen with spring meltwater from the mountains, was reduced to a trickle.
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Villagers sent to investigate along the slopes of Mount Le Pleureur, where the Dranse flowed through a narrow gorge at the head of the valley, returned with grim news. The decade’s succession of cold summers, more intense since 1815, had left a potentially disastrous legacy in the form of an ice dam created by the Giétro glacier. Its lip advanced to the very brink of the narrow gorge, the Giétro had begun to deposit huge blocks of ice into the river, forming a cone-shaped dam thirty meters high. A huge lake had now formed behind the icy wall: three and a half kilometers long, two hundred meters wide, and up to sixty meters deep.

Periodic buildup and release of large amounts of water are a natural characteristic of glacial systems, and typically occur in the spring after a cold summer when meltwater coursing from the peaks and slopes, then draining into a river system, meets with an unusually resilient barricade of ice.
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As the weather warms and the volume of water builds, the pressure on the dam increases to a breaking point. In Iceland, the ensuing catastrophic floods are called
jökulhlaups
, meaning “glacier-floods.” The French word
débâcles
is a more emotive term (at least for English speakers) for the same phenomenon, conveying a sense of their devastating impact on vulnerable Alpine communities.

Extreme glacier-flood conditions prevailed across the Alps in the spring of 1818. In the rising midyear temperatures, and with its volume ever-increasing from seasonal runoff, the dammed-up Dranse was poised to burst at any moment. The threatened flood would inundate the pristine valley with over twenty million cubic meters of water, enough to submerge the town of Martigny twenty kilometers away, and destroy all the farmland and villages in its path. The worried peasants of the Val de Bagnes were fortunate in one regard, however. The provincial government had sent Venetz—a true montagnard—to deal with the crisis. In return, the valley residents offered Venetz their most knowledgeable guide, a chamois hunter from the town of Lourtier named Jean-Pierre Perraudin, to accompany him on his tour of the site of potential cataclysm.

Perraudin is a remarkable figure in the history of nineteenth-century science.
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With little education and no academic credentials whatever, he nevertheless took it upon himself to convert any science-minded individual who crossed his path to the long-held local belief that the
Val de Bagnes had once been covered in a vast sea of ice. For evidence of this, he pointed to the existence of striated marks on rocks high above water level; to the presence of moraines that seemed to mark the outlines of an enormous ancient snake of ice now vanished; and to the anomalous, high-up location of giant boulders, called “erratics,” whose mineral constitution did not match that of the rock formations around them.

Joining Venetz and Perraudin on their urgent trek to the Giétro glacier was the director of the nearby salt mines at Bex, Jean de Charpentier, a respected naturalist whom Perraudin had already attempted to convert to his glacial theories, without success.
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Charpentier later recalled their geological conversations, in which he had found himself persuaded that the prevailing view of the transport of enormous boulders by water, especially uphill, was indeed an impossibility. Nevertheless, Perraudin’s larger idea that the entire Rhône Valley had once been submerged beneath a sheet of ice hundreds of feet thick struck him as pure hogwash, a fantasy “so extravagant that I considered it not worth examining or even considering.”
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Charpentier’s reaction was typical of nineteenth-century geologists when first introduced to glacial theory: amused disbelief. The emerging scientific communities of Europe prided themselves on their intellectual sobriety—their quasi-sacred commitment to observed phenomena and empirically testable facts. To succumb to fantasies of an icebound planet—a world so utterly different from the visible one—spoke of medieval-style madness, a nonsense superstition. In key individual cases, however—including Venetz, Charpentier, and later Charpentier’s student Louis Agassiz—this initial outright rejection of glacial theory was followed by a period of increasingly serious reflection on the evidence in its favor, culminating in a conversion to the glacialist cause almost religious in its intensity.