Report on San Miguel (El Salvador) — 11 August-17 August 2010
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 11 August-17 August 2010
Managing Editor: Sally Kuhn Sennert
Please cite this report as:
Global Volcanism Program, 2010. Report on San Miguel (El Salvador). In: Sennert, S K (ed.), Weekly Volcanic Activity Report, 11 August-17 August 2010. Smithsonian Institution and US Geological Survey.
13.434°N, 88.269°W; summit elev. 2130 m
All times are local (unless otherwise noted)
On 13 August, Servicio Nacional de Estudios Territoriales (SNET) reported that seismicity remained above background levels after an increase was detected on 1 August. Average background RSAM values ranged from 15 to 50 units per day. During 12-13 August, RSAM values ranged between 433 and 465. Over the next few days, seismicity decreased significantly; from 14 August to 16 August, RSAM values decreased from 188 to 132. Access to areas within a 2-km-radius remained restricted.
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.