VDAP Responses at Chaitén in Chile
Eruption of Chaitén volcano, Chile May 2008
Earthquakes felt near Chaitén late on April 30, 2008 provided the first warning of increasing volcanic activity in the area. Twenty-seven hours later, on May 2, 2008, the volcano erupted with an ash column that rose to about 17 km and lasted for 6 hours. Chaitén continued to erupt from May 2nd to May 8th with nearly continuous ash emission and intermittent large explosions. An effective response by Chiles SERNAGEOMIN (Servicio Nacional de Geologia y Mineria) and ONEMI (Oficina Nacional de Emergencia del Ministerio del Interior) led to full evacuation of the town before May 5th when heavy rains generated lahars and devastated Chaitén town.
On May 8, the U.S. Government offered to send a VDAP team to help SERNAGEOMIN install real-time seismic monitoring. One week later, a VDAP team and 15 trunks of gear were in Chile.
At the time, this eruption was thought to be the first from Chaitén caldera in about 9,400 years. Subsequent field work has found evidence for younger eruptive periods. Preliminary estimates of the eruption volume are about one cubic kilometer making it the largest eruption since Hudson, the southernmost Chilean volcano, which erupted in 1991. It was also the first monitored eruption of rhyolite (high silica and explosive magma).
Devastation in Chaitén Town
On May 2, 2008, 1300 people were evacuated from Chaitén. By May 3, all of the people (~5000) living in the Chaitén area had been evacuated by ship. In the sudden evacuation, pets and livestock were left behind, but were eventually relocated as well.
During the first week of the eruption, sediment was remobilized by intense rainfall and roughly 80% of Chaitén town was damaged. Sediment from flood waters buried buildings up to 1.5 m (5 ft). There was extensive damage to the airport & marine facilities.
On May 6, the second plinian eruption occurred, sending ash as high as 30 km. The Government of Chile ordered a total evacuation of people with 50 km of Chaitén. Downwind ash fall extended 1000 km to the coast of Argentina. On multiple occasions ash from the eruption disrupted air traffic in South America. Two experts on volcanic ash hazards to aviation from the USGS Volcano Hazards Program traveled to Argentina and Chile to advise civilian and military aviation interests on safe operations while the volcano was creating conditions hazardous to flight safety.
A lava dome continued to grow and on February 19, 2009 a portion of the dome collapsed sending a pyroclastic flow to within 4 km Chaitén town.
Birth of a new volcano hazards program in Chile
Chile has within its borders more than 122 active volcanoes, in 2008 only a handful of which have any monitoring in place or modern hazard assessment completed. The eruption of Chaitén served as a catalyst, spurring the Government of Chile to develop a national plan to address its considerable volcano hazards.
For more images of Chaiten, see the images section.
S. A. Carn, J. S. Pallister, L. Lara, J. W. Ewert, S. Watt, A. J. Prata, R. J. Thomas, AND G. Villarosa, 2009, The Unexpected Awakening of Chaitén Volcano, Chile, Eos, Vol. 90, No. 24, p. 205-206.