Chaitén: news from SERNAGEOMIN, 22 May 2008

SERNAGEOMIN have issued a new bulletin today about the situation at Chaitén. The key point is that Chaitén volcano is now busy building a lava dome: ‘The eruptive activity is continuing and has begun a phase of dome construction (the slow accumulation of viscose lava around an eruptive centre) inside the active crater, on the north flank of the old dome’. From its northern flank the new dome is active with ‘sporadic explosions’ and the generation of ‘profuse pyroclastic flows’, while from its western side ‘a white eruption column of steam’ is being produced. To the south of the new dome is the vent from which the main eruptive activity of the last few weeks has emerged; there ‘the main eruption column remains vigorous but low, pushed to the south-east by the prevailing winds. In general the column has maintained an oscillatory form, with occasional explosions lifting it above the volcanic edifice’.

The SERNAGEOMIN report includes this photograph, which is a view within Chaitén crater, looking southwards:

The new dome (‘Domo nuevo’) is in the foreground, with its slopes of debris and reddish eruption plume. it rises from the northern flank of the old dome (‘Domo antiguo’). Behind the new dome is a white steam plume (‘Columna principal’) erupting from the active vent on the southern side of the old dome. A larger version of this image, without the captions, can be found here.

The bulletin reports that the new seismic networks installed by SERNAGEOMIN and the USGS are being activitated today. The new network will be invaluable in assessing the processes now under way at the volcano and clarifying potential outcomes. Current seismological indications are suggestive:

The growth in seismic activity represented by a swarm of hybrid events can be attributed, mainly, to a migration of fluids (magma and volcanic gases). The low-frequency seismicity (3 hz) reflects movement associated with the emission of magma, the accumulation of which on the surface is the cause of the construction of a new dome. The high frequencies, in turn, would appear to correspond to landslides generated by the collapse of the growing dome.

Lava domes can grow for periods of weeks, months or years and that growth can be continuous or can proceed by fits and starts. The new Chaitén dome might represent the end of the volcano’s actively eruptive phase for a period of centuries (this was the case with the old Chaitén lava dome, now the unstable site of the current eruption); or it may collapse relatively peacefully (i.e. without violent accompaniments of new magma release and pyroclastic flows) at some future date; or it may collapse violently and initiate a new violent eruptive episode. SERNAGEOMIN are taking no chances and are maintaining their red alert:

SERNAGEOMIN is maintaining volcanic red alert and continues to be concerned about possible major explosions producing the destruction of the old dome and the generation of pyroclastic flows. Nor can the occurrence of lateral explosions be disregarded. The eruptive dynamic now includes the evolution of the new dome, the growth and collapse of which can, in turn, generate pyrocastic flows on its flanks.

The 2008 Chaitén eruption is not over. How things will develop remains to be seen. The future is full of uncertainty – above all, for the thousands who have lost their homes and livelihoods to the eruption and are now refugees in their own country.

(Thanks to Werner Luis for information received.)

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

Information
Global Volcanism Program: Chaitén – summary information for Chaitén (1508-41)
ONEMI, Oficina Nacional de Emergencia – Chilean government emergencies office (Spanish)
SERNAGEOMIN – volcanology information from the Servicio Nacional de Geología y Minería (Spanish)

News
Intensa erupción creó un nuevo domo en el volcán Chaitén – El Mercurio, 22 May 2008 (Spanish)
El volcán Chaitén continúa en actividad – La Voz, 22 May 2008 (Spanish)
Volcán Chaitén entró en nueva fase eruptiva – 123 Chile, 22 May 2008 (Spanish)
Chaitén: Autoridades chilenas mantienen el alerta volcánica roja – infochubut.com, 22 May 2008 (Spanish)
Erupción del Chaitén crea nuevo domo en el volcán – 24 Horas, 22 May 2008 (Spanish)