On 28 December the Technical and Scientific Committee for volcanic risk management of the Arequipa region (comprised of five groups including IGP's OVS and INGEMMET's OVI) recommended that the Alert Level for Sabancaya be raised from Yellow to Orange based on increased activity detected during 8 November-26 December. A progressive increase in the number of explosions per day to 52 was noted along with the detection of 14 daily hybrid events. Harmonic tremor was recorded on 21, 24, and 25 December. Thermal anomalies were identified by the MIROVA system with the last one being recorded on 24 December. Gas-and-ash plumes rose as high as 4.5 km above the crater and drifted 40 km in different directions, affecting the villages of Maca, Achoma, Yanque, and Chivay, and areas to the W and NW including Huambo, Cabanaconde, Pinchollo, Lari, Tapay, and Madrigal. The public was warned to stay at least 12 km away from the volcano. An explosion on 2 January 2017 generated an ash plume that rose 2.5 km and drifted more than 30 km S and SW.

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), Instituto Geológico Minero y Metalúrgico (INGEMMET)