The lava dome at Chaitén volcano in southern Chile is growing very rapidly and its instability has been highlighted as a potential source of hazard in recent reports from the Chilean geological service SERNAGEOMIN (see particularly the report of 16 December 2008). Partial collapses of the steep sides and rapidly extruded lava pinnacles of the growing dome and/or failures of over-pressurized sections of the dome, producing ash-heavy plumes, rockfalls and pyroclastic flows, are daily occurrences. This post showcases a recent example, from 9 January 2009. My attention was drawn to this event by readers of this blog who submitted the images used below – my grateful thanks to them. The images come from the north-facing DGAC camera at Chaitén airfield.

This is an image-heavy post, so to read the whole thing (12 images in total) click on ‘more’.

18:18. A partial collapse took place on the western (left) flank of the currently growing dome (which SERNAGEOMIN has dubbed Domo Nuevo 2, ‘New Dome 2′) at around 18:20 local time on 9 January 2009. This image shows the scene just before the collapse, with the dome steaming away steadily and producing a small whitish plume consisting mainly of water vapour. The wispy brownish plume hanging slightly lower over the summit and blowing away to the east consists of ash produced by earlier collapses – both smaller than the one that is about to happen – at 17:22 and 17:53.

18:23. A column of steam and debris from the collapse (producing a brown colouring) rises above the dome. Debris flows can be seen descending the slopes of the lava dome on the left.

18:28. The plume produced by the collapse and associated explosions disperses towards the east (the right of the picture). The red-brown of suspended ash and debris is clearly visible.

18:33. The white eruption column, with its predominance of water vapour, can be seen emerging on the left, contrasting with the brown clouds of debris now dispersing and descending to the right.

18:38. The hazy, ash-heavy plume hugs the hills to the east of the volcano.

18:43. Continuing dispersal of the ash plume. The white steam of the main eruption column climbs above the clouds of ash and debris.

18:48. Continuing dispersal of the ash plume.

18:53. The main eruption column being produced by the dome, temporarily deflected and lowered by the ash and debris cloud produced by the explosion, re-asserts itself above the summit.

18:58. The ash plume segregates itself by weight of particulate matter as it disperses, with the heavier material continuing to descend and the lighter being carried further in suspense, forming a reddish-brown haze across the landscape to the right.

19:03. The column above the dome is now showing predominantly the white of steam once again.

19:08. A share of the ash deposited across the terrain to the east of the volcano will in due course make its way through Chaitén town via the river on the right (the Río Blanco, also known as the Río Chaitén).

19:13. Nearly an hour after the collapse event, a haze of ash persists about the hills to the right. Shortly after this, at 19:18, a further but smaller collapse took place.

The collapse shown above was not an unusual event. Collapses on this scale appear to be happening several times a day, and there are many more smaller such events.

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 – Servicio Nacional de Geología y Minería (Spanish)
Erupción del Volcán Chaitén – extensive coverage of the Chaitén eruption