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A-Z of thought: Volcanoes

Bob White

Volcanic eruptions capture the imagination: powerful, brooding, but beautiful. Volcanoes make the earth a fruitful place. Most minerals on which life depends come ultimately from volcanoes which cycle material from the deep earth to the surface. Volcanic islands are the most biodiverse areas on earth.

There are almost always warnings before major eruptions, giving time for evacuation. The 1628 BC Santorini eruption blasted 60 km3 of rock into the sky, buried the Minoan town of Akrotiri and caused a tsunami to sweep through the eastern Mediterranean. Yet Santorini was evacuated before the eruption: all valuables had been removed from houses and the only skeleton found was of one stray pig.

There was a less happy outcome from the eruption of Mount PelĂ©e in Martinique on Ascension Day, 1902. This was the worst volcanic disaster of the 20th century, killing 26,000 - 36,000 people. Although earthquakes and ash falls gave two weeks' warning, the governor asked people to stay because elections were due.  But he and his wife died, along with all the inhabitants bar two of Saint-Pierre in just a few minutes when a burning plume of ash swept through the city. Everyone could have been evacuated had the precursors been heeded.

Famine is a frequent side effect of major eruptions, following the death of livestock or crop failure. The 1815 Tambora eruption in Indonesia depressed temperatures throughout the northern hemisphere. 1816 became known as 'the year without a summer': 90,000 people died from famine, many in Europe or North America, far from the site of the eruption.

Likewise the Haze famine of winter 1773-74 in Iceland followed the 1773 eruption of Lakagigar. This caused fluorine poisoning of 50-80 percent of the livestock, and eventually 25 per cent of Icelanders starved to death. Yet the initial volcanism killed no-one. The lack of outside aid was a material factor in the enormous death toll. It is not difficult to find contemporary analogues for the failure of rich nations to supply sufficient aid to distant nations facing famine. To this extent a natural event developed, unnecessarily, into a disaster.

A long history of pagan religious views holds that volcanoes are the homes of gods who must be appeased by offerings to prevent them bringing destruction. Parades of sacred relics and liturgies of propitiation remain a feature of popular Catholicism during eruptions of Etna in Sicily, Popocatépetl in Mexico and Pintatubo in the Philippines. It is possible that a major volcanic eruption provided the pillar of cloud by day and of fire by night that guided the Israelites during the Exodus: if so, Sinai itself was an active volcano. Bob White