Chaitén bulletin no. 106 (17 September 2009)

SERNAGEOMIN bulletin no. 106 on the Chaitén eruption, covering the period 1-16 September 2009, has been published on the website of the Argentinian state geology service SEGEMAR. Click here to see the original document (PDF). A shortened version (combined with a report on Llaima) is available at the SERNAGEOMIN website. Translation as follows.

CHAITÉN VOLCANO
TECHNICAL BULLETIN NO. 106
1-16 SEPTEMBER 2009
OVDAS-SERNAGEOMIN

1. Visual monitoring

The images observed through the DGAC camera, located in Chaitén to the south of the volcano, show that the eruption continues in unchanging form with its column of gas and ash, which occasionally reaches up to 1.5 km above the dome complex. It is notable that the width of the eruption column has been observed to be a little greater than that occasionally referred to earlier, covering almost the entirety of the caldera interior (Fig. 1). Block and ash flows still continue, indicating that the dome complex is present [sic], particularly towards the western area of the caldera.

Figure 1. Image captured by the DGAC [camera] on 14 September 2009 (07:15 local time).

2. Seismic activity

Between 1 and 16 September, the Chaitén volcano seismological monitoring network recorded the following seismicity:

Earthquake type	Average	Total	Magnitude		RSAM
Hybrid HB	18 daily	289	Max. 4.0	Min. 1.5	less than 140,000 units

The majority of the seismicity presents very similar wave forms, which suggests that they originate from the same source and are caused by the same mechanism of origin.

3. Conclusions and interpretation

The eruptive activity continues with the growth of the dome complex, observable only on some occasions because of the winter weather. Consequently the latent danger of collapse because of the growth of the domes continues, with possible explosions and generation of block-and-ash flows, which may affect the valleys adjacent to the 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 – a result of the growth of the dome complex – and the eruptive activity continues with the possibility of the generation of block-and-ash flows in random directions which may affect the surrounding valleys including the generation of new lahars, SERNAGEOMIN suggests maintaining Volcanic Red Alert.

OVDAS-SERNAGEOMIN
17.09.09

[End of SERNAGEOMIN 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