The Unexpected Awakening of Chaitén Volcano, Chile

On 2 May 2008, a large eruption began unexpectedly at the inconspicuous Chaiten volcano in Chile’s southern volcanic zone. Ash columns abruptly jetted from the volcano into the stratosphere, followed by lava dome effusion and continuous low- altitude ash plumes [Lara, 2009]. Apocalyptic photographs of eruption plumes suffused with lightning were circulated globally. Effects of the eruption were extensive. Floods and lahars inundated the town of Chaiten, and its 4625 residents were evacuated. Widespread ashfall and drifting ash clouds closed regional airports and cancelled hundreds of domestic flights in Argentina and Chile and numerous international flights [Guffanti et al., 2008]. Ash heavily affected the aquaculture industry in the nearby Gulf of Corcovado, curtailed ecotourism, and closed regional nature preserves. To better prepare for future eruptions, the Chilean government has boosted support for monitoring and hazard mitigation at Chaiten and at 42 other highly hazardous, active volcanoes in Chile. The Chaiten eruption discharged rhyolite magma, a high-silica composition associated with extremes of eruptive behavior ranging from gentle lava effusion to violent, gas-driven explosions. As the first major rhyolitic eruption since that of Alaska’s Katmai-Novarupta in 1912, it permits observations that are benchmarks for future such events. It also reignites the debate on what processes rekindle long-dormant volcanoes, justifies efforts to mitigate rare but significant hazards through ground-based monitoring, and confi rms the value of timely satellite observations.