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Chile: seismic upswing at Puyehue, alert level raised 4 June 2011

Posted by admin in activity reports, Chile, Puyehue, volcanoes.
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The Puyehue-Cordón Caulle Volcanic Complex (PCCVC) is a large volcanic massif in central Chile, incorporating no fewer than four volcanoes: the Cordillera Nevada caldera, the Cordón Caulle fissure complex, Mencheca volcano and Puyehue volcano. With a history of volcanic activity going back to the Pleistocene, the complex has produced a complicated and highly varied volcanic landscape which is today a Chilean National Park, as well as one of the most geothermically active (PDF) parts of Chile. During the Holocene volcanic activity has been restricted to Cordón Caulle and Puyehue. The Cordón Caulle fissures have been particularly active with frequent eruptions including notable events  in 1921, 1960 (just after the Valdivia earthquake) and 1990. At Puyehue the most recent eruption is dated by the GVP to ‘860 AD ± 75 years’.

There were reports of increased seismicity at Puyehue in May 2008. All quiet since, apparently, until this year, when it appears that things may be stirring under Puyehue once again. The Chilean geological authority SERNAGEOMIN (Servicio Nacional de Geología y Minería) reported increased seismicity in late April and early May this year, and a column of gases was observed (PDF bulletin 26 April 2011) rising from Puyehue on 26 April. An overflight on the following day (PDF bulletin 27 April 2011) did not detect any visual anomalies, but given the continuing elevated seismicity the alert level for Puyehue was raised to Yellow 3. On 5 May SERNAGEOMIN reported (PDF bulletin 5 May 2011) the detection of earthquakes associated with rock fracturing, indicating magma moving at depth, and this seismic activity has continued during the succeeding month. On 2 June a ‘notable increase’ (PDF bulletin 2 June 2011) in the levels of seismicity at Puyehue was detected, and the alert level was raised to Yellow 4, where it remains. The latest bulletin (PDF bulletin 3 June 2011) reports a continuing marked rise in both the number and the magnitude of earthquakes detected, although an overflight did not detect any visual changes in the volcano.

At the beginning of the current phase of unrest in early May there was some concern in the area around the volcano that the authorities were not keeping the public informed about potential hazards, but it appears the local authorities are now doing what they can to reassure the population and keep the information flowing. With the eruption of Chaitén a recent memory the people of south-central Chile have good reason to be sensitive about potential volcanic dangers.

[Thanks to long-standing and good friend of this blog Guillermo for alerting me to the news from Puyehue.]

News
Alcalde de Río Bueno responde a críticas por falta de información sobre alerta en volcán Puyehue – Radio Bío-Bío, 2 May 2011
Decretan alerta amarilla en Puyehue por situación de complejo volcánico – Terra Chile, 2 June 2011
Intendente Varas llama a la calma tras alerta amarilla por sismo volcánico en volcán PuyehueEl Naveghable, 4 June 2011
Más de 16 sismos se han registrado por actividad en complejo volcánico PuyehueEl Mercurio, 4 June 2011

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

The Volcanism Blog