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Fireballs flung to commemorate Salvadorean volcanic eruption 3 September 2009

Posted by admin in El Salvador, San Salvador, volcano culture.
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Bolas de fuego (image by Mario Pleitez, Creative Commons licensed)

In the town of Nejapa in El Salvador, to the north-east of San Salvador volcano, 31 August sees the festival of Bolas de Fuego – balls of fire. Local people paint their faces, take to the streets and joyously fling burning balls of petrol-soaked rags at each other. The BBC reports that the festival commemorates a volcanic eruption that occurred in 1922, but there was no eruption of San Salvador that year. The festival seems to have started in 1922, and perhaps marks the eruption of 1917; or it might be the 1658 eruption, which forced the evacuation of the town, that is being recalled. Local religious tradition has it that the event celebrates the refusal of the town’s patron saint San Gerónimo to be distracted from good works by the Devil, in the form of the volcano, throwing fireballs at him. Anyway, it all looks like good dangerous fun. Everybody has a good time and no-one has, as yet, been seriously hurt.

[Image of the Bolas de Fuego festival 2008 by Mario Pleitez at Flickr, reproduced here under a Creative Commons license.]

News
Nejapa ardió entre las bolas de fuego – elsalvador.com, 31 August 2009
Una batalla de luces enciende el cielo nejapenseDiario CoLatino, 1 September 2009
Fireballs hurled in El Salvador – BBC News, 2 September 2009 (with video)

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El Salvador: Chaparrastique/San Miguel calming down? 13 July 2009

Posted by admin in activity reports, El Salvador, San Miguel.
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San Miguel from the north, 22 February 2005. Image Courtesy Servicio Nacional de Estudios Territoriales (SNET).
San Miguel from the north, 22 February 2005. Courtesy Servicio Nacional de Estudios Territoriales (SNET). [source]

El Salvador’s geological service, the Servicio Nacional de Estudios Territoriales (SNET), issued a special bulletin on 10 July reporting that the seismic activity recently observed at San Miguel volcano (known locally as Chaparrastique) was ‘showing a tendency towards decline’:

Yesterday, 9 July 2009, the microseismicity at the volcano declined to a daily average of 147 units RSAM. Today [10 July 2009], up to 15:00, the seismic stations have registered a daily average of 116 units. If this is compared to the values of previous days it can be seen that there is a tendency towards decline. It is important to note that the seismic energy of the volcano normally fluctuates between 30 and 50 units RSAM.

SNET is continuing to monitor the situation closely, and for the moment security measures, including a 2-kilometre-radius exclusion zone around the summit of the volcano, are remaining in force.

News
Sigue disminuyendo sismicidad en volcán ChaparrastiqueDiario La Página, 11 July 2009

Information
Global Volcanism Program: San Miguel – summary information for San Miguel/Chaparristique (1403-10=)
Servicio Nacional de Estudios Territoriales (SNET) – Salvadorean national geological service

The Volcanism Blog

Increased seismicity at San Miguel volcano (Chaparrastique), El Salvador 7 July 2009

Posted by admin in activity reports, El Salvador, San Miguel.
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San Miguel volcano, also known locally as Chaparrastique, is situated in the east of El Salvador and is a mere 15 km away from the city of San Miguel (population more than 200,000). It is one of El Salvador’s most active volcanoes, with a record of frequent eruptions since the early sixteenth century.

There are now reports of increased seismic activity, in the form of microquakes, at the volcano. The Salvadorean geological service, the Servicio Nacional de Estudios Territoriales (SNET), reports in a special bulletin that there has been an ‘increase in microseismicity [microsismicidad] at Chaparrastique volcano beginning at 03:00 on 6 July 2009′ which is reflected in the RSAM signal which has been fluctuating at 700-1300 units, well above the normal hourly average of 30-50 units RSAM. Such ‘microseismicity’ has been associated in the past with other manifestations of volcanic activity, and is caused by the heating of water within the volcano. The SNET bulletin explains:

The microseismicity is associated with the pressure of [water] vapour which causes the volcanic structure to vibrate, and which is caused by the heating and evaporation of rainwater which infiltrates and moves through the strata of the volcano, increasing its internal pressure.

A 2-kilometre-radius ‘security zone’ has been imposed around the volcano, with local residents and tourists being advised to keep away while monitoring of the volcano continues.

News
Reportan major actividad del volcán de San MiguelEl Diario del Hoy, 6 July 2009
Volcán sube los niveles de actividadEl Diario del Hoy, 6 July 2009
Volcán Chaparrastique de El Salvador incrementa su actividad microsísmica – Terra.com, 7 July 2009
Vigilan volcán salvadoreño por actividad microsísmica – Univisión, 7 July 2009

Information
Global Volcanism Program: San Miguel – summary information for San Miguel/Chaparristique (1403-10=)
Servicio Nacional de Estudios Territoriales (SNET) – Salvadorean national geological service

The Volcanism Blog

Landslide mitigation works get under way at San Salvador 10 June 2009

Posted by admin in El Salvador, natural hazards, San Salvador.
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A little while ago we ran a report here at The Volcanism Blog on San Salvador volcano in El Salvador, which overlooks the country’s capital city (also called San Salvador). This massive compound volcano, which last erupted in 1917, presents – in addition to its violent eruptive character – a serious non-eruptive volcanic hazard in the form of lethal and destructive landslides generated by collapses of its unstable flanks. The populations of communities around the volcano have been campaigning to get mitigation measures put in place to protect them from this threat.

The appearance of a new large crack in the flank of the volcano that faces the capital has apparently helped to concentrate minds on the potential dangers. Last week the Salvadorean ministers of the interior and of public works visited the area to discuss what measures the government may take to deal with the problem. The mitigation techniques being considered include the planting of ‘living barriers’ of foliage on affected slopes and the construction of dykes and drainage channels. The main element is planned to be an 800-metre long and 10-metre wide drainage channel capable of carrying the large volumes of water runoff produced during the rainy season, which runs from May/June to November. A total of $10 million (or possibly $6 million, initially) is being sought from the government’s Special Investments Fund to begin work on the project.

The Ministry of Public Works (MOP) is now beginning a geological, geotechnical and hydrological survey of the area, which is expected to take four weeks. The MOP says that the work itself will probably be carried out this winter, once the imminent rainy season for this year is over.

News
MOP realizará obras de mitigación por grieta en volcán de San SalvadorLa Prensa Grafica, 5 June 2009
Gobernación pedirá $10 Mlls. para obras en volcánEl Diario del Hoy, 5 June 2009
MOP inicia procesos para obras de mitigación en volcán de San SalvadorDiario Co Latino, 8 June 2009
Obras de mitigación en volcán de San Salvador costarán unos $6 millonesLa Prensa Grafica, 8 June 2009
MOP inicia trabajos preventivos en volcánDiario El Mundo, 8 June 2009

Information
Global Volcanism Program: San Salvador – summary information for San Salvador (1403-05=)
Volcano Hazards in the San Salvador Region – USGS report, 2001, available at the CVO website
Volcano Landslides and their Effects – USGS Volcano Hazards Program

The Volcanism Blog

San Salvador: the dangers of volcanic landslides 17 April 2009

Posted by admin in El Salvador, natural hazards, San Salvador.
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San Salvador volcano (photo by Rick Wunderman, 1999, Smithsonian Institution).
San Salvador volcano, El Salvador, with the city of San Salvador in the foreground. Picture by Rick Wunderman, 1999 (Smithsonian Institution). [source]

When we think of the hazards presented by volcanoes, eruptions naturally come to mind: but volcanoes don’t have to erupt to be lethal. San Salvador volcano (or Quetzaltepec) in El Salvador, a complex compound volcano with a summit elevation of 1893 metres has a long history of violent eruptions, but has not erupted since 1917. The capital city of El Salvador, also called San Salvador, stands at the foot of the volcano, and as it has grown it has encroached increasingly upon the volcano’s slopes. As a result, any eruption of San Salvador volcano would have very serious consequences. Even without eruptions, however, the instability of the volcano’s slopes presents the city with another serious hazard: landslides.

The Salvadorean newspaper Diario Co Latino reports this week that community leaders from around San Salvador are calling on the government to recognize the hazard posed by volcanic landslides and declare a state of emergency for the area north-east of the volcano, between San Salvador and San Vicente volcanoes. They recall that a 1934 landslide from the latter volcano killed an unknown number of people in the village of Tepetitan, and that in 1982 heavy rainfall triggered a landslide on the flanks of San Salvador’s El Pichaco peak (on the right in the picture above) which descended more than 4 kilometres from its source and swept into the north-western part of the city, destroying homes and killing 300-500 people. There have been further potentially dangerous landslides in January 2001 and October 2008, when a large landslide took place which could have caused a similar disaster to that of 1982, if the debris flow had not taken a different course during its descent.

With this hazardous history in mind, along with other even deadlier examples of volcanic landslides such as Casita (October 1998, more than 2000 people killed), the concern expressed by the San Salvador community leaders is understandable. They are petitioning the national government for a thorough scientific survey of landslide-prone areas, improved monitoring and mitigation works, and the relocation of communities particularly at risk from landslides.

News
Piden declarar ‘Estado de Emergencia’ en volcán de San SalvadorDiario Co Latino, 15 April 2009

Information
Global Volcanism Program: San Salvador – summary information for San Salvador (1403-05=)
Global Volcanism Program: San Vicente – summary information for San Vicente (1403-07=)
Volcano Hazards in the San Salvador Region – USGS report, 2001, available at the CVO website
Volcano Landslides and their Effects – USGS Volcano Hazards Program

The Volcanism Blog