Report on San Miguel (El Salvador) — 28 February-6 March 2018
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 28 February-6 March 2018
Managing Editor: Sally Kuhn Sennert
Please cite this report as:
Global Volcanism Program, 2018. Report on San Miguel (El Salvador). In: Sennert, S K (ed.), Weekly Volcanic Activity Report, 28 February-6 March 2018. Smithsonian Institution and US Geological Survey.
13.434°N, 88.269°W; summit elev. 2130 m
All times are local (unless otherwise noted)
On 2 March SNET reported that gas plumes rose as high as 400 m above San Miguel’s crater rim during the previous week. Ash was in the emissions on 24, 26, and 28 February, and 1 March. RSAM values fluctuated between 70 and 179 units (normal values are 50-150 units) during 1-2 March. At 2200 on 5 March seismic amplitude began to increase, with RSAM values rising to 318 units by 0600 on 6 March. A webcam recorded minor gas emission during 5-6 March.
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.