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Chaitén update, 5 February 2009 5 February 2009

Posted by admin in activity reports, Chaitén, Chile, eruptions.
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SERNAGEOMIN have published bulletin no. 72 on the Chaitén eruption. The original document in Spanish can be found at the OVDAS website (PDF). Translation as follows.

ERUPTION OF CHAITÉN VOLCANO
TECHNICAL BULLETIN NO. 72
28 JANUARY TO 2 FEBRUARY 2009
OVDAS-SERNAGEOMIN

1. Visual monitoring

Observations made through the DGAC camera during this period reveal that Dome 2 is maintaining constant eruption and is increasing in volume, as judged from the recurrent collapses of its unstable walls. On 28 January between 10:39 and 10:44 a marked vertical projection of ash was noted, forming a dense column of some 500m in height, possibly caused by a small explosion. However, there was an immediate collapse of the dome and a block-and-ash flow was produced to the west, and it is not possible to rule out the occurrence of a lateral explosion in the same direction (Fig. 1). On that day and also on 30 January block-and-ash flows continued to form.

Figure 1.
Figure 1. View from the DGAC camera in which a dense vertical column of ash some 500m in height can be seen (left, red arrow) and the generation of a block-and-ash flow to the west because of a collapse of Dome 2 and/or a lateral blast.

Figure 2.
Figure 2. Collapses and formation of block-and-ash flows towards the west on 28 January (left and centre) and 30 January (right).

2. Seismic activity

The seismicity recorded by the Chaitén volcano monitoring network has remained relatively similar to the preceding period. It showed an average of one HB-type earthquake per hour, with magnitudes varying between 1.5 and 3.9. On 29, 30 and 31 January earthquakes of greater magnitudes of between 3.8 and 3.9 were registered. Subsequently, the magnitude of these events decreased to a maximum value of 3.2. Preliminary calculations locate these HB-type earthquakes in the area to the south of, and in some cases beneath, the caldera of Chaitén volcano. In addition occasional VT-type earthquakes appeared with magnitudes of less than 1.0.

3. Conclusions and interpretation

The seismic activity of Chaitén volcano has remained unchanged in number and magnitude of envents, which indicates that the growth of Dome 2 continues, although the rate of extrusion of viscous lava could be somewhat lower than at previous stages. Continuing dome growth, with the continued generation of new collapses forming block-and-ash flows, could eventually affect the heads of the main valleys.

In consequence, bearing in mind the persistence of seismic activity associated with the growth of the erupting dome, with the consequent generation of block-and-ash flows, SERNAGEOMIN maintains Volcanic Red Alert.

[End of bulletin.]

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

Information
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