PVMBG described activity at Sinabung during 10-17 January based on observations from a post in the Ndokum Siroga village, 8.5 km away. Each day brownish white or gray and white ash plumes rose as high as 5 km, pyroclastic flows traveled 0.5-4.5 km E, SE, and S, and incandescent material was observed on the S and SE flanks as far as 3 km. Seismicity remained high, with constant tremor, hybrid earthquakes indicating a growing lava dome, and volcanic earthquakes. The number of low-frequency earthquakes continued to drop, however. 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.

Source: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as CVGHM)