IGP's OVS reported that during 12-18 December seismicity at Sabancaya continued to be dominated by long-period earthquakes; hybrid earthquakes decreased from 14 events per day to 6. Gas-and-ash plumes rose as high as 3.5 km above the crater and drifted more than 35 km NW, E, SE, and S.

Based on webcam and satellite views, the Buenos Aires VAAC reported that during 14-20 December gas-and-water-vapor emissions and sporadic ash puffs rose 6.4-8.2 km (21,000-27,000 ft) a.s.l. (2.3 km above the crater) and drifted SW, WSW, W, and NW.

Geological Summary. Sabancaya, located in the saddle NE of Ampato and SE of Hualca Hualca volcanoes, is the youngest of these volcanic centers and the only one to have erupted in historical time. The oldest of the three, Nevado Hualca Hualca, is of probable late-Pliocene to early Pleistocene age. The name Sabancaya (meaning "tongue of fire" in the Quechua language) first appeared in records in 1595 CE, suggesting activity prior to that date. Holocene activity has consisted of Plinian eruptions followed by emission of voluminous andesitic and dacitic lava flows, which form an extensive apron around the volcano on all sides but the south. Records of observed eruptions date back to 1750 CE.

Sources: Instituto Geofísico del Perú (IGP), Buenos Aires Volcanic Ash Advisory Center (VAAC)