Report on Santa Ana (El Salvador) — 5 October-11 October 2005
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 5 October-11 October 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, 5 October-11 October 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 5-11 October, small explosions, degassing, and low-to-moderate seismicity occurred at Santa Ana. Inclement weather during much of the report period prohibited ground and satellite observations and sulfur-dioxide measurements. During an aerial inspection of the volcano on 11 October, no changes were observed at the crater. Around the 11th, sulfur-dioxide measurements were at 600-700 metric tons per day. SNET noted that eruptive activity could continue at the volcano and an eruption similar to, or smaller than, the October 1 eruption could occur in the future. The Alert Level within a 5-km radius around the volcano's central crater was 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.