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Reventador update, 24 October 2009 24 October 2009

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Ecuador’s Instituto Geofísico has issued a new special bulletin for Reventador volcano, no. 7 of 23 October 2009 (PDF), which includes reports from an overflight that took place on 22 October.

The bulletin reports an increase in the number of long period seismic events and of explosions from 17:30 on 20 October. This was followed, from the afternoon of 22 October, by ‘a slight decline’ in the volcano’s activity, which nevertheless continued at ‘levels considered to be high’. Some of the explosions have been clearly audible in towns around the volcano and have generated ‘columns of steam and gas with little or no ash content which have reached a maximum altitude of 4 km’.

Instituto Geofísico staff carried out fieldwork at the volcano on 21 October and reported sounds of ‘cannonades’ of varying intensities, and the expulsion of incandescent material in the form of blocks and lava flows. An overflight on the morning of 22 October revealed that lava flows on the north and south flanks of the volcano are still active, and that the lava dome in the crater shows no signs of instability. The southern lava flow ‘has divided into four branches, and the greater part of it is situated above 2500 m above sea level (Figure 1)’, while ‘the northern flow is small and is situated above 3000 m above sea level (Figure 2)’. Temperatures of about 400°C within the crater and 250°C on the fronts of the lava flows have been shown in thermal images. SO2 emissions have averaged 500 tonnes/day.

Distribution of lava flows in the area south of the caldera of Reventador volcano, 22 October 2009 (S. Vallejo)
Figure 1. Distribution of lava flows in the area south of the caldera of Reventador volcano, 22 October 2009 (S. Vallejo).

Distribution of lava flows around the caldera of Reventador volcano, 22 October 2009 (S. Vallejo)
Figure 2. Distribution of lava flows on the north flank of Reventador volcano, 22 October 2009 (S. Vallejo).

The Instituto Geofísico daily bulletin for 24 October (PDF) reports continuing seismic signals of explosive events but no reports of ‘surface manifestations related to this type of activity’. Over the preceding 24 hours, 28 long period events were recorded, along with 17 explosive signals, ’16 bands of harmonic tremor and 9 of spasmodic tremor’. Loud rumbling sounds have been heard from the volcano.

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

Information
Global Volcanism Program: Reventador – summary information for Reventador (1502-01=)
Instituto Geofísico – Geophysical Institute of Ecuador

The Volcanism Blog