PVMBG reported that at 0158 on 8 August a phreatic eruption at Sinabung produced a brown-gray ash plume that rose 2 km above the summit and drifted E and SE. A news article stated that ashfall impacted at least four districts, including Naman Teran, Merdeka, Berastagi, and Dolat Rayat. BNPB noted that clean water was distributed, and emergency vehicles were deployed to clean up the ashfall. Later that day at 1718 an ash plume rose at least 1 km above the summit and drifted ESE. There is a general exclusion zone set at 3 km from the summit, with extensions to 5 km on the SE and 4 km on the NE. A news article noted that authorities began enforcing a 7-km exclusion zone.

An eruptive event at 1016 on 10 August produced a dense gray ash plume that rose at least 5 km above the summit (24,500 ft a.s.l.) and drifted NE and SE. Parts of the plume drifted down the flank; ashfall was reported in several areas downwind. The Darwin VAAC advisory stated that satellite observations showed ash plumes drifting WNW at 9.8 km (32,000 ft) a.s.l. at 1430 and ENE at 4.3 km (14,000 ft) a.s.l. at 1630. The Alert Level remained at 3 (on a scale of 1-4). Residents and tourists in Berastagi (13 km E) turned on headlights to navigate through the ash according to a news article.

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: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as CVGHM), Badan Nacional Penanggulangan Bencana (BNPB), Darwin Volcanic Ash Advisory Centre (VAAC), The Jakarta Post, NBC News, Gatra