Based on satellite images and information from PVMBG, the Darwin VAAC reported that during 18, 21-22, and 24 May ash plumes from Sinabung rose to altitudes of 3.6-5.5 km (12,000-18,000 ft) a.s.l. and drifted S and E. BNPB reported that pyroclastic flow descended the flanks at 1648 on 21 May, killing six people and critically injuring three more. The victims were gardening in the village of Gamber, 4 km SE from the summit crater, in the restricted zone. The report noted that activity at Sinabung remained high; four pyroclastic flows descended the flanks on 21 May, and ash plumes rose as high as 3 km.

Geological Summary. Gunung Sinabung is a Pleistocene-to-Holocene stratovolcano with many lava flows on its flanks. The migration of summit vents along a N-S line gives the summit crater complex an elongated form. The youngest crater of this conical andesitic-to-dacitic edifice is at the southern end of the four overlapping summit craters. The youngest deposit is a SE-flank pyroclastic flow 14C dated by Hendrasto et al. (2012) at 740-880 CE. An unconfirmed eruption was noted in 1881, and solfataric activity was seen at the summit and upper flanks in 1912. No confirmed historical eruptions were recorded prior to explosive eruptions during August-September 2010 that produced ash plumes to 5 km above the summit.

Sources: Badan Nacional Penanggulangan Bencana (BNPB), Darwin Volcanic Ash Advisory Centre (VAAC)