Based on reports from PVMBG, BNPB reported four eruptions from Sinabung on 5 October. The first one occurred at 0146, and produced a pyroclastic flow that traveled 4.5 km S and an ash plume that rose 2 km. The next three events, at 0638, 0736, and 0753, all generated pyroclastic flows that traveled 2.5-4.5 km S. The fourth event also produced an ash plume that rose 3 km. A news article stated that pyroclastic flows from a fifth event at 0900 were smaller, but again traveled 4.5 km after a sixth event at 1200.

According to the Darwin VAAC a low-level eruption recorded by the PVMBG webcam generated a pyroclastic flow on 6 October; some of the ash rose higher and drifted E. The Jakarta MWO noted that an ash plume rose to an altitude of 5.2 km (17,000 ft) a.s.l. and drifted S on 7 October. Cloud cover prevented satellite observations. A news article posted on 8 October noted that eruptions in the previous four days caused some evacuations.

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), NBC News