SERNAGEOMIN reported increased seismicity at Lonquimay during the first half of March, characterized by hybrid (HB) signals accompanied by long-period (LP) events, and fewer volcano-tectonic (VT) events. Only some of the HB and VT events could be located where the epicenters were within 2-7 km of the volcano with hypocenters at depths of 4-11 km. The number of HB and VT events increased on 9 March. Deformation was not detected and no abnormal gas emissions were recorded. During 18-21 March two additional earthquakes were recorded, a VT and an HB, both with magnitudes below 1.3. Although the events were low magnitude, the seismicity was anomalous in the data going back to 2010 when monitoring stations were installed. The Alert Level was raised to Yellow, the second lowest level on a four-color scale.

Geological Summary. Lonquimay is a small, flat-topped, symmetrical stratovolcano of late-Pleistocene to dominantly Holocene age immediately SE of Tolguaca volcano. A glacier fills its summit crater and flows down the S flank. It is dominantly andesitic, but basalt and dacite are also found. The prominent NE-SW Cordón Fissural Oriental fissure zone cuts across the entire volcano. A series of NE-flank vents and scoria cones were built along an E-W fissure, some of which have been the source of voluminous lava flows, including those during 1887-90 and 1988-90, that extended out to 10 km.

Source: Servicio Nacional de Geología y Minería (SERNAGEOMIN)