All eyes have been on Mount Agung for the past week, watching the mesmerising clouds of ash pouring out of this tempestuous Indonesian volcano. Right now, the question is whether it is building for a repeat of the devastating eruption in 1963, when lava and lahars (rivers of water and rock) flooded hectares of land in minutes, killing 1,100 people.
While the news bulletins focus on Agung, geologists are starting to feel jittery about another volcano, thousands of kilometres away in Iceland. The unpronounceable Öræfajökull last erupted in 1727, so we don’t have measurements to show how this volcano behaves in the lead-up to an eruption. The glaciated mountain, which is Iceland’s highest volcano, is teasing scientists by producing swarms of small earthquakes under its flanks. “Earthquakes are rare at Öræfajökull, so they may indicate a reawakening,” says Dave McGarvie, a volcanologist at the Open University.
Three people died during the relatively small eruption in 1727, when a meltwater flood swept their farm away. But the really scary eruption occurred in 1362, when sailors reported pumice “in such masses that ships could hardly make their way through it”. Thick volcanic deposits obliterated the rich farmland surrounding the volcano, and ash travelled as far as western Europe.
“It was Iceland’s largest explosive eruption since the island was settled, about 1,100 years ago,” says McGarvie. But the abandoned farmsteads reveal that this volcano produced many earthquakes before both previous eruptions, giving people time to evacuate. For now, Icelandic scientists have installed extra earthquake monitoring equipment and are listening intently to the rumblings below.
