Report on Santa Ana (El Salvador) — 4 January-10 January 2006
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 4 January-10 January 2006
Managing Editor: Sally Kuhn Sennert
Please cite this report as:
Global Volcanism Program, 2006. Report on Santa Ana (El Salvador). In: Sennert, S K (ed.), Weekly Volcanic Activity Report, 4 January-10 January 2006. Smithsonian Institution and US Geological Survey.
13.853°N, 89.63°W; summit elev. 2381 m
All times are local (unless otherwise noted)
During 30 December to 6 January, volcanic activity was moderate at Santa Ana. Seismicity was a bit over normal levels with small earthquakes occurring, which were interpreted as being associated with gas pulses. Continuous low-level emissions of steam and gas originated from the lagoon and from fumaroles within the crater. Gas rose 200-500 m above the crater (or 8,400-9,400 ft a.s.l.) and drifted SW. The sulfur-dioxide flux ranged between 180 and 1,476 metric tons per day. The Alert Level remained at Red, the highest level, within a 5-km radius around the volcano's summit crater.
Geologic Background. Santa Ana, El Salvador's highest volcano, is a massive, dominantly andesitic-to-trachyandesitic stratovolcano that rises immediately W of Coatepeque caldera. Collapse of Santa Ana (also known as Ilamatepec) during the late Pleistocene produced a voluminous debris avalanche that swept into the Pacific Ocean, forming the Acajutla Peninsula. Reconstruction of the volcano subsequently filled most of the collapse scarp. The broad summit is cut by several crescentic craters, and a series of parasitic vents and cones have formed along a 20-km-long fissure system that extends from near the town of Chalchuapa NNW of the volcano to the San Marcelino and Cerro la Olla cinder cones on the SE flank. Historical activity, largely consisting of small-to-moderate explosive eruptions from both summit and flank vents, has been documented since the 16th century. The San Marcelino cinder cone on the SE flank produced a lava flow in 1722 that traveled 13 km E.