The Servicio Nacional de Geología y Minería (SERNAGEOMIN) reported increasing unrest at Láscar. Satellite images detected progressively increasing sulfur dioxide emissions since 6 February (188 tons per day) with an average of 1,191 tons per day (t/d) recorded on 20 February. Sulfur dioxide emissions measured with Differential Optical Absorption Spectroscopy (DOAS) instrumentation located at the Emú station, 6 km ESE, averaged 1,010 t/d on 22 February. Thermal anomalies occasionally detected in satellite data indicated increased temperatures on the crater floor during 6-23 February. Additionally, crater incandescence was visible in webcam images during 19 and 22-23 February. Seismicity during 19-24 February was characterized by a decrease in long-period earthquakes and an increase in signals indicating surficial activity such as landslides. The Alert Level remained at Yellow (the second lowest level on a four-color scale) and the public was warned to stay at least 1 km away from the crater.

Geological Summary. Láscar is the most active volcano of the northern Chilean Andes. The andesitic-to-dacitic stratovolcano contains six overlapping summit craters. Prominent lava flows descend its NW flanks. An older, higher stratovolcano 5 km E, Volcán Aguas Calientes, displays a well-developed summit crater and a probable Holocene lava flow near its summit (de Silva and Francis, 1991). Láscar consists of two major edifices; activity began at the eastern volcano and then shifted to the western cone. The largest eruption took place about 26,500 years ago, and following the eruption of the Tumbres scoria flow about 9000 years ago, activity shifted back to the eastern edifice, where three overlapping craters were formed. Frequent small-to-moderate explosive eruptions have been recorded since the mid-19th century, along with periodic larger eruptions that produced ashfall hundreds of kilometers away. The largest historical eruption took place in 1993, producing pyroclastic flows to 8.5 km NW of the summit and ashfall in Buenos Aires.

Source: Servicio Nacional de Geología y Minería (SERNAGEOMIN)