The Servicio Nacional de Geología y Minería of Chile (SERNAGEOMIN) has issued a new bulletin dated 6 May 2008 on the Chaitén eruption, the first since their initial report on 2 May, the day the event began. SERNAGEOMIN scientists are not expecting a decline in the volcano’s activity any time soon, and warn that things may well become even more intense:

The Servicio Nacional de Geología y Minería reports that on the basis of the visual and seismic information collected since the date of the eruption of Chaitén volcano, we conclude that a major new explosion or explosions, and the eventual collapse of the eruption column and/or the rhyolite dome, cannot be ruled out.

The 962m-high rhyolite dome situated in the Chaitén caldera is the volcano’s major feature. The collapses of such lava domes are a major cause of pyroclastic flows.

The bulletin provides further information on the dramatic activity of yesterday morning, which forced the total evacuation of Chaitén town and the surrounding area:

… during the morning of 6 May, at 08:20, the eruptive cycle went through a recrudescence with vigorous and rhythmic explosions of great energy producing a much wider laterally expanding eruptive column of about 30 kilometres altitude in its initial phase, declining subsequently.

A subsequent helicopter overflight found that two craters on the northern side of the dome had joined into one, 800m-wide vent during this eruptive phase. (Assuming, as appears to be the case from photographs, that the initial site of the eruption was on the southern flank of the dome, it now seems that the volcano is erupting from both northern and southern flanks.) No pyroclastic flows were reported to the north, south or west (the eastern zone could not be inspected, presumably, being obscured by the eruption plume), and it was noted that the rivers around the volcano were carrying a greater load of erupted material.

Overall SERNAGEOMIN considers that the eruption may develop in two ways from this point onwards – although, as always with predictions of volcanic activity, it is impossible to be sure.

There is the possibility of a collapse of the eruptive column and/or the rhyolite dome, which would generate pyroclastic flows. On the other hand the fall of ashes may continue with accumulations whose thickness will depend on the intensity of the explosions and the prevailing winds.

The bulletin also observes that so far no lava has been erupted by the volcano.

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, Chile (Spanish)