PVMBG reported that white plumes rose as high as 500 m above Sinabung’s summit on most days during 20-27 October; foggy conditions sometimes prevented visual observations. On 23 October white-and-gray ash plumes rose as high as 1 km and drifted in multiple directions. Pyroclastic flows traveled 1.5-2.5 km down the E and SE flanks on 25 October. According to a news article ash plumes drifted SE of the volcano twice that same day, causing some local residents to evacuate. The report noted that a lava dome in the summit crater continued to grow. The Alert Level remained at 3 (on a scale of 1-4), with a general exclusion zone of 3 km and extensions to 5 km in the SE sector and 4 km in the NE sector.

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), The Jakarta Post