Richard Fortey

On 21 August 1986, Hadari, a peasant farmer in the highlands of the Cameroon, was woken by a rumbling sound. Startled, he observed vapours pour from the edge of the nearby volcanic Lake Nyos, to form a miasmic cloud which silently spilled over the edge of the lake and sought lower ground, like a heavy morning mist. By the following day seventeen hundred people lay dead in the valley villages of Subum, Cha and Nyos. The corpses of their cattle lay strewn about, surrounded by the motionless bodies of the flies that had plagued them in life. Nothing that needed to breathe survived. What Hadari had witnessed was a volcanic eruption consisting only of the heavy gas carbon dioxide, a gas that smothered the villagers as it flowed down to the low ground. Survivors described a sensation of weakness in the legs, an unendurable lassitude. They felt weighed down, exhausted unto death: a subtle eruption all the more horrible for its stealth.

We usually think of volcanic eruptions as more blatant events: the literally petrified inhabitants of Pompeii seared by hot ashes, at once killed and immortalised, frozen for ever in the act of gasping for breath or pushing away the fearsome incandescence. But Volcanoes makes it clear that this is only one choice from a menu of destruction, on which the Nyos disaster is certainly the most arcane. Some eruptions are almost benign. The fires of Hawaii erupt regularly above hot spots that remain in the same site for millions of years, as the Earth’s crust glides above them, creating islands, or plastering new lava onto old flows. The lava extrudes as a liquid rather like boiling toffee, and spills down in a manner which would be described as orderly only by a volcanologist. Smaller flows can sometimes be turned aside to spill harmlessly into the sea. The basalt cools into dark, grotesque shapes like twisted rope or solidified rapids, instant monuments created from the smoothly flowing pahoehoe lava. Blocky, jumbled lava is known as aa, so providing Scrabble players with the ultimate crowner.

There is a type volcano: it is on the island of Vulcano in the Aeolian Islands, and its intermittent rumblings and eruptions were once interpreted as the sounds of Vulcan’s forge. In classical times the festival of Vulcanalia was held on 23 August to appease the unpredictable and temperamental god. His bad temper was seldom mollified. Santorini blew up 3600 years ago, a catastrophe that produced a caldera six kilometres in diameter and split the northern part of the island into three. This eruption may well have fatally weakened Minoan civilisation, thereby diverting the course of European history. The idea for Plato’s vanished island of Atlantis could have derived from this destruction, an idea that seems to be more indestructible than pumice, for even today the search for it extracts funds from the gullible.

Construction and destruction often go together. On 20 February 1943, a small fissure opened in a field in Mexico, and a new volcano appeared where there had been none before. During the next nine years, Paricutín produced 700 million cubic metres of lava and a billion cubic metres of volcanic ash. A fertile valley was blighted, plants and animals sickened and died – those of a religious cast of mind saw it as a visitation on the sinful.

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