Chaitén update, 18 February 2009 18 February 2009Posted by admin in activity reports, Chaitén, Chile, eruptions, natural hazards.
Tags: Chaitén, Chile, natural hazards, South America, volcanic activity reports, volcanic eruptions
The Chilean state geological service SERNAGEOMIN have published a bulletin dated 11 February 2009 on their website. It is apparently available nowhere else at the moment. Translation as follows.
11.02.2009 SERNAGEOMIN Bulletin on Chaitén volcano
The seismic activity of Chaitén volcano between 2 and 9 February has remained unchanged in the number and the magnitude of events, indicating that the growth of Dome 2 continues, although the earthquakes have occurred more to the east or at greater depth beneath the volcano.
However, the speed of extrusion of viscous lava is somewhat higher than in previous periods, judging from the prominent pinnacle which forms the summit. The continuing growth of Dome 2 and the presence of this large pinnacle forming its summit is continuing to generate new gravitational collapses, creating block-and-ash flows which, eventually, could affect the heads of the principal valleys, depending on their volumes.
Observations carried out during a field trip to maintain the seismic stations installed in the area, between 2 and 9 February, showed that Dome 2 remains in constant eruption and continues to increase its volume.
Indeed, on 7 February between 12:00 and 14:30 two photographs were captured from the Chaitén locality which showed a bulky Dome 2 atop Dome 1.
[Figure 1 caption reads: Photographs of 7 February where the complex of domes can be seen and it is possible to see a prominent pinnacle on the summit of Dome 2 which forms its summit, with very sharp sides.]
Moreover, it is possible clearly to see a prominent and impressive pinnacle that forms the summit of Dome 2, with very unstable sharp and steep slopes, which could collapse at any moment and produce block-and-ash flows.
On 9 February at 12:00 another photograph showed the voluminous complex of zones with the enormous pinnacle that forms the summit of Dome 2. The eventual massive collapse of this pinnacle of the dome could generate voluminous block-and-ash flows, descending through the neighbouring valleys.
[Figure 2 caption reads: Photograph of 9 February showing the voluminous complex of domes, with a prominent pinnacle that forms the summit of Dome 2, the instability of which tends towards a gravitational collapse, generating block-and-ash flows possibly affecting the neighbouring valleys depending on their volume.]
During the latter period, the seismic monitoring network of Chaitén volcano has continued to show HB-type earthquakes, with an average of 2 earthquakes per hour and with magnitudes varying between 1.8 and 3.8.
Between 5 and 7 February a large number of earthquakes with magnitudes ranging between 3.3 and 3.8 were registered. On 8 February the number of earthquakes registered declined, however the magnitude of of these events has been maintained, with earthquakes up to [magnitude] 3.8.
According to preliminary calculations of the epicentral distances from Santa Bárbara station the earthquakes have been located more to the east or beneath Chaitén volcano at greater depths.
Moreover, on 6 February at 09:08 (local time) a VT-type earthquake located 22km from the Santa Bárbara station was registered, at a magnitude of 2.5.
Consequently, in view of the continuance of the seismic activity associated with the growth of the erupting dome and the formation of large pinnacle at its summmit, with the certain possibility of the generation of block-and-ash flows, SERNAGEOMIN maintains Volcanic Red Alert.
[End of SERNAGEOMIN bulletin.]
Yesterday, 17 February 2009, there was a significant collapse of some kind at Chaitén. The weather has been very poor there for the last few days, with heavy cloud cover and rain, so it is hard to see precisely what is going on, but a sharp-eyed reader drew my attention to events occurring at around 14:00 local time yesterday. Webcam images from the Chaitén airfield camera can be viewed below.
It appears that a partial collapse of the new dome brought a very large cloud of debris pouring down the Chaitén river valley towards the town itself: the reddish cloud of ash can be seen in the pictures from 14:00, 14:05 and 14:10 rolling out of the valley and against the dark flank of the hill that rises behind the town. Perhaps this was the collapse of the ‘large pinnacle’ referred to in the SERANGEOMIN bulletin above? The weather conditions at the moment make it impossible to confirm whether this was indeed the case – we shall just have to wait and see.
For all our Chaitén coverage: Chaitén « The Volcanism Blog.
Global Volcanism Program: Chaitén – summary information for Chaitén (1508-41)
SERNAGEOMIN – Servicio Nacional de Geología y Minería (Spanish)
Erupción del Volcán Chaitén – extensive coverage of the Chaitén eruption