Increased seismic activity at San Miguel volcano, El Salvador


Ash emissions, small explosions and increasing tremor were recorded at San Miguel (Chaparrastique) volcano in El Salvador during July 13/14, 2014. National Ministry of Environment and Natural Resources (MARN) reported that the seismic vibration of San Miguel volcano remains at very high levels. 

Internal seismic vibration has fluctuated between 860 and 1312 units during July 13/14, 2014, more than 25 times normal levels.  

Seismic network stations located on the flanks of the volcano registered a total of 335 microearthquakes, all located on the northern flank of the volcano. The magnitudes ranged between 0.4 and 2.1. Volcano remains at very unstable conditions and could erupt from the summit vent or from the northern flank in the coming days. 

Epicenters of microearthquakes located in the volcano Chaparrastique in period between January 27, 2014 to July 14, 2014. (Credit: MARN)

San Miguel is one of El Salvador’s most active volcanoes. After 11 years of sleep (2002 VEI 1) the volcano suddenly woke up in December 2013 and sent a plume of ash about 9 km (30 000 feet) into the atmosphere. The ash settled both on the slope of the volcano, as seen here, and on nearby towns, forcing 5 000 people to evacuate.

The Advanced Land Imager (ALI) on the Earth Observing-1 (EO-1) satellite aquired this image of San Miguel volcano on January 15, 2014. (Credit: NASA Earth Observatory/Jesse Allen and Robert Simmon/Caption by Robert Simmon and Holli Riebeek)

Geologic summary

The symmetrical cone of San Miguel volcano, one of the most active in El Salvador, rises from near sea level to form one of the country's most prominent landmarks. The unvegetated summit of the 2130-m-high volcano rises above slopes draped with coffee plantations. A broad, deep crater complex that has been frequently modified by historical eruptions (recorded since the early 16th century) caps the truncated summit of the towering volcano, which is also known locally as Chaparrastique. 

Radial fissures on the flanks of the basaltic-andesitic volcano have fed a series of historical lava flows, including several erupted during the 17th-19th centuries that reached beyond the base of the volcano on the north, NE, and SE sides. The SE-flank lava flows are the largest and form broad, sparsely vegetated lava fields crossed by highways and a railroad skirting the base of the volcano. The location of flank vents has migrated higher on the edifice during historical time, and the most recent activity has consisted of minor ash eruptions from the summit crater. (GVP)

Featured image: San Miguel pictured in 1996. (Credit: Carlos Pullinger/Servicio Nacional de Estudios Territoriales, El Salvador)


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