BNPB reported that activity at Sinabung remained high. On 17 June there were 120 avalanches, four pyroclastic flows that traveled 2-3 km ESE and S, and lava was incandescent as far as 2 km S and SE. On 18 June a pyroclastic flow traveled 2.5 km SE and incandescent lava as far as 1.5 km SE was observed. Based on ground observations, the Washington VAAC reported that an ash plume rose to an altitude of 4.3 km (14,000 ft) a.s.l. and drifted SE during 18-22 June. On 23 June BNPB noted that 10,184 people (3,030 families) were displaced, housed in 10 different shelters. The Alert Level remained at 4 (on a scale of 1-4).

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), Washington Volcanic Ash Advisory Center (VAAC)