I had a dream, which was notall a dream.
The bright sun wasextinguish』d, and the starsDid wander . . .
—Byron, 「Darkness」
IN 1815 on the island of Sumbawa in Indonesia, a handsome and long-quiest mountaiambora exploded spectacularly, killing a huhousand people with its blast andassociated tsunamis. It was the biggest volic explosion ihousand years—150 timesthe size of Mount St. Helens, equivalent to sixty thousand Hiroshima-sized atom bombs.
News didn』t travel terribly fast in those days. In London, The Times ran a small story—actually a letter from a mert—seven months after the event. But by this time Tambora』seffects were already bei. Thirty-six cubic miles of smoky ash, dust, and grit haddiffused through the atmosphere, obsg the Sun』s rays and causing the Earth to cool.
Sus were unusually but blearily colorful, an effect memorably captured by the artist J. M.
W. Turner, who could not have been happier, but mostly the world existed under anoppressive, dusky pall. It was this deathly dimhat inspired the Byron lines above.
Spring never came and summer never warmed: 1816 became known as the year withoutsummer. Crops everywhere failed to grow. In Ireland a famine and associated typhoidepidemic killed sixty-five thousand people. In New England, the year became popularlyknown as Eighteen Hundred and Froze to Death. M frosts tinued until June andalmost no planted seed would grow. Short of fodder, livestock died or had to be prematurelyslaughtered. In every way it was a dreadful year—almost certainly the worst for farmers iimes. Yet globally the temperature fell by only about 1.5 degrees Fahre. Earth』snatural thermostat, as stists would learn, is an exceedingly delicate instrument.
The eenth tury was already a chilly time. For two hundred years Europe and NorthAmeri particular had experienced a Little Ice Age, as it has bee known, whichpermitted all kinds of wintry events—frost fairs ohames, ice-skating races along Dutals—that are mostly impossible now. It eriod, in other words, when frigidity wasmu people』s minds. So erhaps excuse eenth-tury geologists for beingslow to realize that the world they lived in was in fact balmy pared with former epochs,and that much of the land around them had been shaped by crushing glaciers and cold thatwould wreck even a frost fair.
They khere was something odd about the past. The European landscape was litteredwith inexplicable anomalies—the bones of arctic reindeer in the warm south of France, hugerocks stranded in improbable places—and they often came up with iive but not terriblyplausible explanations. One Frenaturalist named de Luc, trying to explain how graniteboulders had e to rest high up on the limestone flanks of the Jura Mountains, suggestedthat perhaps they had been shot there by pressed air in caverns, like corks out of apopgun. The term for a displaced boulder is aic, but in the eenth tury theexpression seemed to apply more often to the theories than to the rocks.
The great British geologist Arthur Hallam has suggested that if James Hutton, the father ofgeology, had visited Switzerland, he would have seen at ohe significe of the carvedvalleys, the polished striations, the telltale strand lines where rocks had been dumped, and theother abundant clues that point to passing ice sheets. Unfortunately, Hutton was not a traveler.
But even with nothier at his disposal than sedhand ats, Huttoed out ofhand the idea that huge boulders ha