Report on Santa Ana (El Salvador) — 16 November-22 November 2005
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 16 November-22 November 2005
Managing Editor: Gari Mayberry
Please cite this report as:
Global Volcanism Program, 2005. Report on Santa Ana (El Salvador). In: Mayberry, G (ed.), Weekly Volcanic Activity Report, 16 November-22 November 2005. Smithsonian Institution and US Geological Survey.
13.853°N, 89.63°W; summit elev. 2381 m
All times are local (unless otherwise noted)
During 16-21 November seismicity at Santa Ana was above background levels; a minor increase on 17 November was probably due to strong wind disturbing the seismic equipment. Small earthquakes occurred that were interpreted as being associated with the fracturing of rocks and gas pulses. The amount of gas emitted was low. The daily sulfur-dioxide flux averaged about 1,000 metric tons during 11-17 November. The Alert Level within a 5-km radius around the volcano's central crater remained at Red, the highest level.
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.