The Chilean state geological service SERNAGEOMIN has published a joint bulletin covering activity at Llaima and Chaitén volcanoes. The Llaima report covers the period 22 August to 1 September, and the Chaitén report covers 20-31 August. Translation as follows.

SERNAGEOMIN bulletin on Chaitén and Llaima volcanoes
Monday 7 September 2009

Llaima volcano

Although the seismicity of Llaima volcano has remained stable during the period between 22 August and 1 September, with RSAM values within normal ranges, sudden changes cannot be ruled out, possibly associated with instability in the magma column, which can be inferred from the marked instability in behaviour shown by the volcano during recent months. As a result, there is the continuing latent possibility of a volcanic reactivation.

In consequence, SERNAGEOMIN maintains Alert Level Green II and suggests keeping an exclusion zone of 4 km radius around the principal crater. It should be noted that OVDAS personnel are constantly attentive to the development of the volcano’s activity. It is reiterated that this alert could change suddenly, therefore it is recommended that the community stay prepared for any changes in activity that may occur and for corresponding revision and updating of emergency plans.

Photographs taken by Victor Hazeldine on 01-09-2009.

Chaitén volcano

For its part, the eruptive activity of Chaitén in the period between 20 and 31 August continued with the growth of the dome complex, which was only occasionally observed because of the winter weather conditions.

The images recorded by the DGAC camera, located in Chaitén, to the south of the volcano, show that the eruption continues in unchanging form with a column of gas and ash climbing, occasionally, to 1.5 km above the dome complex. Also block-and-ash flows persist, indicating that this structure continues to grow, particularly towards the western sector of the caldera.

The quantity of deposited pyroclastic material both from volcanic rocks that have been emitted by the block-and-ash flows and from lateral explosions have created large accumulations in the adjacent valleys and especially the Chaitén river valley, so that the occurrence of lahars towards Chaitén [town] during intense rains cannot be ruled out.

In consequence, given that the seismicity remains at high levels – an effect of the growth of the dome complex – and that the eruptive activity persists with the possibility of the generation of block-and-ash flows in random directions, which may affect the surrounding valleys and generate new lahars, SERNAGEOMIN suggests maintaining Volcanic Red Alert.

[End of SERNAGEOMIN bulletin.]

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

Information
Global Volcanism Program: Chaitén – summary information for Chaitén (1508-41)
Erupción del Volcán Chaitén – extensive coverage of the Chaitén eruption
Global Volcanism Program: Llaima – summary information for Llaima (1507-11=)
Proyecto Observación Visual Volcán Llaima – Llaima Visual Observation Project
SERNAGEOMIN – Servicio Nacional de Geología y Minería, Chile

The Chilean state geological service SERNAGEOMIN has published brief updates on Chaitén and Llaima volcanoes on its website in a combined bulletin dated 31 August 2009. Translation as follows.

SERNAGEOMIN bulletin on Chaitén and Llaima volcanoes

Chaitén Volcano

In the period between 4 and 20 August the eruptive activity of Chaitén has continued with the growth of the dome complex – particularly towards the western sector of the caldera – observable only occasionally because of the winter season. The column of gases, composed of water vapour and ash, has occasionally risen to 1.5 km above the complex.

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.

Llaima Volcano

While seismicity at Llaima volcano tended to decrease in the early days of August, it has subsequently increased, slightly exceeding its usual values in this latest period (17-21 August). These oscillations in seismic activity (LP-type earthquakes [Long Period earthquakes] of high and low frequency) could be related to the rising and falling of the magma column located in the principal conduit of the volcano, demonstrating the instability of the magma column.

The absence of other types of seismic activity in this type of phenomenon suggests the existence of an unobstructed volcanic conduit, in which magmatic fluids can suddenly rise freely, bringing about a new eruptive phase.

Due to the markedly erratic behaviour which the volcano has shown during recent times, it is not possible to rule out its reactivation. Because of the foregoing, SERNAGEOMIN continues with Green Alert level 2, maintaining a 4-km radius of exclusion around the principal crater.

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

Information
Global Volcanism Program: Chaitén – summary information for Chaitén (1508-41)
Erupción del Volcán Chaitén – extensive coverage of the Chaitén eruption
Global Volcanism Program: Llaima – summary information for Llaima (1507-11=)
Proyecto Observación Visual Volcán Llaima – Llaima Visual Observation Project
SERNAGEOMIN – Servicio Nacional de Geología y Minería, Chile