20 maio 2010

The terrible persistence of Volcanoes

Simon Winchester for Lapham's Quarterly

The map is almost uncannily similar: a spray of black dots showing the recordings of a foul gray haze spreading all across Europe, from Helsinki to Naples, from Heligoland to Majorca, and reaching eventually to Aleppo and Damascus—and all caused by clouds of ash from an immense volcano erupting far across the sea in Iceland. 

This was a map drawn not this year, but created from data collected in 1783. The volcano, called Laki, erupted for eight dismal months without cease. It ruined crops, it lowered temperatures and drastically altered the weather. It killed 9,000 people, it drenched the European forests in acid rain, it caused skin lesions in children and the deaths of millions of cattle and, by one account, it was a contributing factor (due to hunger-inducing famines) to the outbreak six years later of the French Revolution.

Volcanoes, on the other hand, do not end. They may not kill so widely—the total number of casualties from the hundred greatest of the world’s volcanoes barely approach the hundreds of thousands of deaths from one almighty earthquake—but they remain standing, haughtily reminding those below of their terrible potential. They then can and do erupt for long and debilitating periods—Eyjafjallajokull, which is causing such uncertainty and apprehension in today’s Europe, poured out its gases and rock ash for two full years when it last erupted in 1821. They are gigantic spigots which once opened, can be turned off only when some kind of equilibrium is restored in the hadean chambers beneath them—and even then they are prone to be opened once again when pressure below become unsustainable. 

The geographical extent of a volcano’s wind-borne ash-clouds, and the duration of the eruptions, are often such as to effect changes in society itself. Tambora, which erupted on the Indonesian island of Sumbawa in 1815, remains a classic of its kind. It was immense: almost 40 cubic miles of pulverized rock were hurled into the sky, producing clouds which darkened, cooled and polluted a world that was already well populated and widely civilized. The consequences ranged from the dire—a lowering of temperature that caused frosts in Italy in June and snows in Virginia in July, the failure of crops in immense swathes across Europe and the Americas and the infamous “year without summer” of 1816—to the frankly ludicrous. Irish migrants, promised better weather in New England, found it on landing to be every bit as grim as the Connemara and Cork they had left, and so either went home, or pressed on in hope to California.

Seventy years later, nearby Krakatoa had world-wide effects too, both short-term physical and the long-term societal. A series of tsunamis (which killed 40,000 locally) were noticed swelling the waters as far away as Portland Bill and Biarritz. The bang of its detonation was clearly heard (like naval gunfire, said the local police officer) 3,000 miles away on Rodriguez Island. But then came a year’s worth of awe-inspiring evening beauty—astonishing sunsets of purple and passion fruit and salmon that had artists all around the world trying desperately to capture what they managed to see in the fleeting moments before dark. A Londoner named William Ashcroft left behind almost 500 watercolors that he painted, one every ten minutes like a human film camera, from his Thames-side flat in Chelsea; Frederic Church, of the Hudson River School, captured the crepuscular skies over Lake Ontario in their full post-Krakatoan glory; and many now agree that Edvard Munch had the purple and orange skies over Oslo in mind when ten years afterwards he painted, most hauntingly, The Scream.

Most important of all, however, is the fact that truly gigantic volcanic explosions—those that rank 8 on the Volcanic Explosivity Scale (Tambora was on this scale a 7, Krakatoa a 6, while the eighteenth century Laki and today’s Eyjafjallajokull rate merely as twos)—often bring about the wholesale extinctions of species. Such events only occur about once every 100,000 years. Toba, a few miles up the road from Tambora, was one such: it erupted 72,000 years ago, and so changed the climate that humankind was reduced to no more than a thousand breeding pairs, almost eliminating us before we had had much of a chance to get going. 

And today, there is Yellowstone—a VEI 8 volcano with a record of past fury, standing there innocently, just waiting to explode again. Signs of its imminent eruption are everywhere—though imminent in this case signifies at least a quarter of a million years, by which time humankind will be extinct anyway.

I mentioned this once to an audience in Kansas City, adding the quarter-million-year caveat as a form of comfort. It did not work. It merely prompted a middle-aged woman to rise, choleric, incredulous and demanding. “Extinct!” she spluttered. “What on earth do you mean? Even Americans will be extinct?”

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