Dome collapse event at Chaitén

A large-scale explosive dome collapse took place at Chaitén between late morning and early afternoon today, beginning at around 10:59 local time. The picture above, from the north-facing DGAC camera at Chaitén airfield, shows the scene during this event at 11:54. For the full sequence of 21 images, click on ‘more’ below.

UPDATE: M. Spadari (‘mic22’ – see comments below) has compiled a video of the entire event from start to finish. Click here to view the video (flv format, hosted at Photobucket).

10:49. The new dome – its pointed summit clearly visible – steaming away steadily and producing a relatively small plume.

10:54. The new dome still producing its plume, although it may be slightly bulkier and ashier than it was in the previous image.

10:59. A collapse and explosion has taken place on the eastern side of the dome (the right of this picture). The explosion column can be seen to the right of the main plume, which now has far more bulk and is darker, showing more ash content.

11:04. A greatyly thickened, ashy plume, the aftermath of the first event. Strong winds are pushing it quickly away to the north and east. If there was less wind, the plume would be climbing much higher.

11:09. A further eastward lateral explosion visible on the right. The brown colouring of the plume indicates heavy ash content.

11:14. A very substantial gas-and-debris cloud has been thrown up by the second lateral explosion.

11:19. This and the next three images show the thick, dark, ash-heavy column produced by the lateral explosion, rising alongside and blending with the main plume from the top of the dome (itself showing evidence of higher than normal ash content).

11:24.

11:29.

11:34.

11:39. A third explosive event blasts out powerfully to the east, projecting large quantities of ash and debris into the sky.

11:44. This and the next three images show the greatly augmented plume rising vigorously before being caught by the strong winds and blown towards the north-east.

11:49.

11:54.

12:00.

12:05. The column produced by the collapse is starting to recede.

12:10. The vigour of the emissions has waned a little more, but there is still a great deal of gas and ash being erupted from the area of the collapse.

12:15. What appears to be another small explosion from the unstable dome livens things up again.

12:20. This and the remaining two pictures show the plume losing its bulk and returning to its currently normal lighter colour, indicating little ash content and a predominance of water vapour.

12:25.

12:30.

The event shown above is larger and more spectacular than the normal run of such occurrences at Chaitén, but it is not different in kind from the scores of collapse events that are taking place at Chaitén’s rapidly-growing and unstable lava dome every day. We may see more such large-scale collapse/explosion sequences as that growth continues and the resulting edifice becomes still more unstable. Furthermore, as the dome grows higher the fallout from such collapses (lateral blast and pyroclastic flows) will be less constrained by the surrounding topography, acquire more energy in its descent and have ever more far-reaching effects. The strain exerted by the growth of this huge new dome on the old caldera walls, meanwhile, raises the possibility of a much larger structural failure and explosive collapse. This volcano remains highly dangerous.

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