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Upsurge in activity at Chaitén causes alarm 24 July 2008

Posted by admin in activity reports, Chaitén, Chile, eruptions.
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The latest bulletin from SERNAGEOMIN has the volcano producing an eruption column ‘less vigorous than in previous days, with an altitude less than 2.0 km’ which suggests ‘a decline in superficial eruptive activity’. But an upsurge in seismic activity and its nature is causing concern, with SERNAGEOMIN suggesting that below the surface the volcano is building towards a new phase of elevated eruptive activity:

However, in the last 48 hours there has been a clear increase in the number and magnitude of earthquakes greater than 2.6M.

The earthquakes of greater magnitude (greater than 2.6M) occurred during 22 and 23 July, defining a new focus of seismicity to the east-north-east (ENE) of the volcano, and this activity began to be registered by stations located at distances of between 176 and 296 km from Chaitén volcano, which has not happened since the beginning of the eruptive process.

Preliminary calculations indicate that the recent earthquakes of greater magnitude have deep hypocentres (approximately 10-15km) and are located east-north-east (ENE) of the volcano, in a sector distinct in this respect from the earthquakes of this type of previous days reported in previous bulletins, located south and south-east of Chaitén.

This seismicity, especially that detected by remote stations, can be attributed to new injections of magma, which could prolong the eruption for a significant period, even months, and induce eventual upswings in superficial eruptive activity.

The increase in activity at Chaitén has caused the authorities to try to evacuate everyone who was still in the area. The government has the legal power to force evacuation, but seems to be relying on persuasion at the moment. According to a report today in La Nación ‘between 30 and 40 people who had returned [to the town of Chaitén], and 260 more who had travelled for the day by boat to collect their belongings began a plan of evacuation and headed to Puerto Montt in fear that an eruption of the volcano would follow’. 123 Chile has 100 people being present in the town in addition to the 260 visitors, and reports that all operations in Chaitén have been suspended because of the ‘resurgence in eruptive activity’ of recent hours. Radio Santiago quotes ONEMI director Carmen Fernández warning that ‘There could be a major explosion, the column may rise with increased seismicity, there may be emissions of pyroclasts’ and SERNAGEOMIN volcanologist Luis Lara describing increased activity and ‘intense emission of ashes’. The ash-laden eruption plume was directly over Chaitén town at low altitude today, making breathing difficult. ‘The city dawned cloudy’ admitted Chaitén’s mayor, José Miguel Fritis.

For all our Chaitén coverage: Chaitén « The Volcanism Blog

News
Inquietud genera reactivación del volcán ChaiténLa Nación, 24 July 2008 (Spanish)
Evalúan suspender operativos en Chaitén por reactivación eruptiva123 Chile, 24 July 2008 (Spanish)
Despertó el Chaitén: Inician evacuación tras recrudecimiento de la actividad del volcán – Radio Santiago, 24 July 2008 (Spanish)
The Chaiten rollercoaster ride continues – Eruptions, 24 July 2008

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)

The Volcanism Blog

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Comments

1. Hawkeye - 24 July 2008

Boy, this sure is one heck of an interesting eruption. I would love to know the total volume of magma erupted so far. I assume volcanologists will figure that out at a later date.

2. Beano - 25 July 2008

Question for Dr.Ralph. Once a Caldera, Always a Caldera?

With the volume of ejecta from this continuous eruption since early May, Would there not be a “big hole” somewhere underneath the area just ripe for a top collapse?

John Seach (From http://www.volcanolive.com/ )who visited the site in mid July reported that the Chaiten residents who had returned to gather their belongings had heard a strange noise beneath the ground in the Chaiten township – Like running water.

3. volcanism - 25 July 2008

SERNAGEOMIN is talking about an injection of new magma, which suggests that their monitoring is telling them that any big holes beneath the volcano are being filled up. The magma source for this eruption seems quite large enough to keep it going without a top collapse for a while yet. An explosive collapse is another matter. As for those ‘rumbling noises under the town, similar to the sound of running water’, I wonder if it could have been running water?

4. Fresh Bilge » Chaitén Update 39 - 25 July 2008

[...] The Volcanism Blog reports on new seismic information. It is very ominous. The webcam has shown occasional glimpses of plume beyond broken clouds today. The plume height is [...]

5. Is Chaiten a clogged volcano? « Eruptions - 25 July 2008

[...] eruption if it makes it all the way. The SERNAGEOMIN agrees with some of the ONEMI suggestions (covered nicely on the Volcanism Blog), but overall, the feeling I get from reading these reports is that the Chilean officials are [...]


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