Dozens of Earthquakes Rattle a Chilean Volcano, Raising Alerts

Dead trees in the River Ibanez valley killed by ash from the Cerro Hudson eruption in 2011.John Warburton-Lee/Getty Images Last night, the ONEMI (Oficina Nacional de Emergencias) and SERNGEOMIN (Chilean Geological Survey) in Chile raised the alert status for the area around Cerro Hudson in the southern Andes. Normally, raising the alert status like this is due to an acute change, when the behavior of the volcano shifts suddenly. However, this time, the elevation to Yellow alert status at Cerro Hudson is due to accumulated events over the past month. Dozens of small earthquakes have occurred since the start of November, none stronger than M3.2. But their location (in geographic space and depth) are similar to those before the last eruption of Hudson in 2011. The number of earthquakes hasn't increased much above the baseline activity at an active volcano like Hudson, but energy released by the largest earthquakes has ...