Puyehue-Cordón Caulle update, 6 June 2011

The eruption at Puyehue-Cordón Caulle appears to be continuing, but with declining force. The Chilean geological service SERNAGEOMIN reports in a bulletin (PDF) released at 13:30 local time yesterday, 5 June 2011, that ‘since 18:00 local time yesterday [4 June] the eruption which began at Cordón Caulle has declined in intensity’, with diminished seismicity characterized by low-frequency tremor and a reduced number of hybrid earthquakes ‘associated principally with the fracture of rigid material and explosions located in the area to the SE of Cordón Caulle. An overflight on the morning of 5 June ‘reported an eruption column of 10-12 km altitude and 2 km width’. The most recent advisories from Buenos Aires VAAC confirm ‘continuous emission’ with the plume reaching FL350/400 (35,000-40,000 feet, 10.6-12.2 km altitude). The alert level remains at Red 6, ‘moderate eruption’.

The state emergencies office ONEMI also released a bulletin yesterday which gives a summary of a news conference held by senior officials of the Interior Ministry, ONEMI and SERNAGEOMIN which highlighted the dangers posed by volcanic sediment in the river system around the volcano. A shift of the wind yesterday brought heavy ashfall to Lago Ranco, about 70 km north of the volcano, and the evacuation has been extended to that area. The Under-Secretary of the Interior warned that ”The zones of the upper and lower Riñinahue present a risk of floods produced by sediments that have been deposited’, while Enrique Valdivieso of SERNAGEOMIN reported that ‘through monitoring carried out both north and south of the [volcanic] range we have seen the presence of sediment and pumice in the southern sector’. The possibility of lahars is clearly of some concern at the moment. Valdivieso also said that lava had not been detected by SERNAGEOMIN, but pyroclastic flows had deposited sediment, mud and debris on the flanks which would descend the watercourses and reach surrounding districts during the morning of 6 June. Both SERNAGEOMIN and ONEMI are maintaining their related but slightly different Red Alerts for the Puyehue-Cordón Caulle area, and the evacuation orders remain in place.

The ashfall from this eruption has had a significant impact on Argentina, with reports that over 200 square kilometres of Chubut Province has been affected and suggestions that the ash has now been detected in Buenos Aires. Meanwhile the change in wind direction has brought renewed wories for the Chilean authorities about ashfall and hazardous emissions affecting areas to the north of the volcano.

Finally, it’s worth mentioning that the precise location of this eruption within the Puyehue-Cordón Caulle volcanic complex remains unclear from the reports that have been accessible so far. The past history of this chain of volcanoes suggests that almost any part of it is capable of doing almost anything. For the moment Puyehue, which was the initial identification, seems to be the most likely candidate, but we’ll hedge our bets and go on calling it Puyehue-Cordón Caulle. [EDIT: from Oxford volcanologist David Pyle’s Twitter, a map placing the eruption ‘just NE of the 1960 vents’: http://twitpic.com/57qpdb]

UPDATE: have a look at this remarkable HD video of the eruption, linked by Agustín Amenabar in the comments below: http://www.vimeo.com/24715989

FURTHER UPDATE: Erik Klemetti has a thorough and detailed update on events at Puyehue-Cordón Caulle at Eruptions.

News
Gran columna de cenizas de volcán Puyehue afecta a sur de Chile y Argentina – AFP, 5 June 2011
Gobierno ordenó evacuación preventiva de Riñinahue por riesgo de aluvión – Puranoticia, 5 June 2011
La nube de ceniza ya supera los doscientos kilómetros cuadrados – El Diario de Madryn, 6 June 2011
Erupción sobre Osorno: Ubilla advierte por gases y cambio de viento – La Nación, 6 June 2011
Chile volcano eruption: alert remains for ash cloud – BBC News, 6 June 2011

Information
Global Volcanism Program: Puyehue-Cordón Caulle volcanic complex – summary information for the PCCVC (1507-15=)