SNET reported that sulfur dioxide gas flux in tonnes per day from San Miguel was high: 2,200 on 31 December 2013, 1,740 on 1 January 2014, and 700 on 2 January. The report noted that the measurement on 2 January was likely low due to changes in wind patterns that day. During 1-2 January RSAM values ranged from 17 to 28 units. On 5 January gas plumes rose as high as 150 m above the crater. The next day light-gray gas plumes rose 200 m and drifted SW. RSAM values during 5-6 January were between 15 and 33 units.

Geological Summary. The symmetrical cone of San Miguel, one of the most active volcanoes in El Salvador, rises from near sea level to form one of the country's most prominent landmarks. A broad, deep, crater complex that has been frequently modified by eruptions recorded since the early 16th century caps the truncated unvegetated summit, also known locally as Chaparrastique. Flanks eruptions of the basaltic-andesitic volcano have produced many lava flows, including several during the 17th-19th centuries that extended to the N, NE, and SE. 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. Flank vent locations have migrated higher on the edifice during historical time, and the most recent activity has consisted of minor ash eruptions from the summit crater.

Source: Servicio Nacional de Estudios Territoriales (SNET)