During 19-23 October, seismicity was relatively stable and there were low-level gas emissions at Santa Ana. On 22 October, a lahar was reactivated in the Potrero Arriba area, NE of the volcano. During 22-25 October, there was an increase in the amount of tremor at the volcano. In addition, seismicity associated with gas emissions slightly increased. The Alert Level within a 5-km radius around the volcano's central crater was at Red, the highest level.

Geological Summary. Santa Ana (also known as Ilamatepec), is a massive, dominantly andesitic-to-trachyandesitic stratovolcano in El Salvador immediately W of Coatepeque Caldera. Collapse 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 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. Small to moderate explosive eruptions from both summit and flank vents have 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.

Source: Servicio Nacional de Estudios Territoriales (SNET)