Report on San Miguel (El Salvador) — 25 December-31 December 2013
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 25 December-31 December 2013
Managing Editor: Sally Kuhn Sennert
Please cite this report as:
Global Volcanism Program, 2013. Report on San Miguel (El Salvador). In: Sennert, S K (ed.), Weekly Volcanic Activity Report, 25 December-31 December 2013. Smithsonian Institution and US Geological Survey.
13.434°N, 88.269°W; summit elev. 2130 m
All times are local (unless otherwise noted)
According to news articles, an explosive eruption at San Miguel that began at 1030 on 29 December prompted an evacuation of 1,400-2,600 people. A dense ash plume rose from the crater. Based on wind data, the Washington VAAC reported that the ash plume rose to an altitude of 9.7 km (32,000 ft) a.s.l. and drifted ENE at higher altitudes and W at lower altitudes.
SNET reported that sulfur dioxide flux was 637 tonnes per day on 29 December and 1,244 tonnes per day on 30 December. During 30-31 December seismicity decreased significantly. Through the morning of 31 December emissions had consisted of gas and slight amounts of ash that drifted WSW.
Geologic Background. 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 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, 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 N, NE, and SE sides. The SE-flank 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.