PVMBG described activity at Sinabung during 15-22 March based on observations from a post in the Ndokum Siroga village, 8.5 km away. Dense white plumes rose 500 m above the lava dome daily, and as high as 1 km on 21 March. Lava had traveled 2.4 km down the flanks as of 20 March and was incandescent at various areas. Incandescent material originating from the edges of the lava dome and flow traveled up to 1.5 km S and 200 m SE. A pyroclastic flow traveled 3 km S on 17 March. Tremor and volcanic earthquakes were detected, and signals representing avalanches from the unstable and still-growing dome decreased slightly. Sulfur dioxide emissions varied between 300 and 598 tons per day, indicating no new magma. The Alert Level remained at 4 (on a scale of 1-4). Visitors and tourists were prohibited from approaching the crater within a radius of 5 km.

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)