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Chaitén bulletin no. 99 (2 July 2009) 11 July 2009

Posted by admin in activity reports, Chaitén, Chile, eruptions.
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The following is Chaitén bulletin number 99 from SERNAGEOMIN, dated 2 July 2009, and covering the period 24 June to 2 July 2009. It is available as a PDF via the informes page of the Observatorio Volcanológico de los Andes del Sur (OVDAS) website, and there is also a summary version, combined with a report on Llaima, on the SERNAGEOMIN website.

SERNAGEOMIN bulletins for Chaitén are currently characterized by brevity, a formulaic approach, and an almost complete lack of useful detail. This one is no exception. Translation as follows.

24 JUNE-2 JULY 2009

1. Visual monitoring

The images obtained by the DGAC camera located in Chaitén to the south of the volcano, show that the eruption has continued in an unchanging form with one column of gas and ash which has occasionally risen to 1.5 km above the dome complex. During the brief periods observation because of the clouds and rain in the area, a predominance of water vapour has been observed in the column. The block-and-ash flows still persist, indicating that the dome complex continues its growth, particularly towards the western sector of the caldera.

2. Seismic activity

The Chaitén volcano seismological monitoring network has registered an average of 17 HB-type earthquakes per day, with maximum magnitudes reaching 4.1. During this period, there has been a tendency towards decline, both in the number of earthquakes and their magnitude, compared with the preceding weeks. HB-type seismicity of magnitudes under 2.5 has declined to an average of 7 events per day. The majority of the seismicity displays very similar wave forms, which suggests a common sources and a similar mechanism of origin. The energy released RSAM is calculated on the available data as not exceeding 150000 units.

3. Conclusions and interpretation

The eruptive activity continues with the growth of the dome complex, observable at times. The seismic activity for this period has declined in daily average, both in the number of earthquakes and their magnitude. The latent danger continues of collapse because of the growth of the domes, with possible explosions and generation of block-and-ash flows, which may affect the valleys adjacent to Chaitén volcano. Moreover, the quantity of pyroclastic material from fallen volcanic rock originating from both block-and-ash flows and lateral explosions has formed important accumulations in the adjacent valleys and especially towards the valley of the Chaitén river, from which the fresh occurrence of lahars towards Chaitén during torrential rains cannot be ruled out. In consequence, given that the seismic activity remains elevated as a result of the growth of the dome complex, with the possibility of the generation of block-and-ash flows which may affect the surrounding valleys including the new generation of new lahars, SERNAGEOMIN maintains Volcanic Red Alert.


[End of SERNAGEOMIN bulletin.]

For all our Chaitén coverage: Chaitén « The Volcanism Blog.

Global Volcanism Program: Chaitén – summary information for Chaitén (1508-41)
SERNAGEOMIN – Servicio Nacional de Geología y Minería (Spanish)
Erupción del Volcán Chaitén – extensive coverage of the Chaitén eruption

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