Reventador update, 24 October 2009 24 October 2009

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.

Figure 1. Distribution of lava flows in the area south of 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

Restless Reventador: increased activity reported 17 October 2009

Ecuador’s Instituto Geofísico reports that Reventador volcano is showing signs of increased activity. In a special bulletin (PDF) issued on 15 October (PDF) intensified seismic activity was reported, with harmonic tremor signals saturating the seismic network; signals associated with rockfalls were also detected. There were also reports of crater incandescence and rumbling sounds. Thermal anomalies were detected over the volcano by satellite, and increased sulphur dioxide emissions were registered.

A further special bulletin (PDF) issued on 16 October reports that the seismic activity has continued, principally characterized by bands of harmonic tremor interspersed with sporadic long-period (LP) events. During an overflight yesterday scientists observed a lava dome within the crater, a lava flow on the north flank of the volcano and blue-ish gas emissions. The emissions reached up to 100 metres above the crater. Explosions and the ejection of incandescent blocks were reported, and the presence of incandescent material on the south flank of the volcano indicated that a lava flow had recently descended that flank. Thermal imagery revealed that incandescent material around the crater was reaching temperatures of 300°C.

Washington VAAC reported an increase in seismic activity at around 19:00 UTC, and emissions and a hotspot at 20:15 UTC today. An ash cloud was reported moving NW at FL150 (15000 feet/4500 metres).

News
Advierten del aumento en la actividad del volcán ecuatoriano Reventador – EFE, 17 October 2009

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

Reventador: increased activity 24 April 2009

Ecuador’s Reventador volcano is showing a significant increase in activity, according to reports in the Ecuadorian press, quoting the country’s Instituto Geofísico. According to the news site Confirmado.net, the seismic signals have included ‘spasmodic and harmonic bands of tremor’ interspersed with long period earthquakes.

UPDATE: A special bulletin from the Instituto Geofísico (PDF) reports the significant activity which occurred at Reventador during 23 April 2009.

• Gradual but steady increase in seismicity, with spasmodic and harmonic bands of tremor showing periods of high and low activity, interspersed with long period events.
• Column of water vapour reaching an estimated 2-3 km altitude, with low ash content: satellite imagery indicated that the plume extended approximately 26 km WSW.
• Persistent thermal anomaly detected on the volcano, increasing in intensity during periods of increased tremor.
• Loud noises reported from the volcano.
• No reports of ashfall.

News
Volcán ‘El Reventador’ presenta incremento de actividad – Confirmado.net, 23 April 2009
Aumenta paulatinamente la actividad sísmica del volcán Reventador, en Ecuador – Terra España, 23 April 2009
Reventador reanuda su actividad – El Universo, 24 April 2009

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