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Chaitén bulletin no. 98 (23 June 2009) 25 June 2009

Posted by admin in activity reports, Chaitén, Chile, eruptions.
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Another somewhat insubstantial bulletin on the Chaitén eruption from SERNAGEOMIN. This is number 98, dated 23 June 2009, and covering the period 16-23 June 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 on the SERNAGEOMIN website. Translation as follows.

16-23 JUNE 2009

1. Visual monitoring

The images obtained through the DGAC camera located to the south of Chaitén volcano show that the eruption continues unchanging with its column of gases and ashes, which occasionally rises to 1.5 km above the dome complex. During the few periods of observation, because of 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 seismic monitoring network of Chaitén volcano has registered an average of 23 HB-type [hybrid] earthquakes per day, with maximum magnitudes reaching 4.1, displaying a slight increase compared to the previous weeks. Regarding the seismicity of magnitudes of under 2.5, these have continued with an average of 12 HB-type earthquakes per day. Most of the seismicity has shown very similar wave forms, which suggests that they may come from the same source and the same originating mechanism. With regard to the seismic energy liberated RSAM, this has not exceeded 150000 units.

3. Conclusions and interpretation

The eruptive activity continues with the sometimes visible growth of the dome complex, which continues its expansion in height and extent. The seismic activity for this period shows a slight increase in the daily average, but the magnitudes have been maintained. There is a continuing latent danger 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 adjancent 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 an effect of the growth of the dome complex, with the possibility of the generation of block-and-ash flows in random directions that may affect surrounding valleys and include the 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

The Volcanism Blog