PVMBG described activity at Sinabung during 23 March-8 April based on observations from a post in the Ndokum Siroga village, 8.5 km away. Dense white plumes rose at most 1.2 km above the lava dome. Lava had traveled 2.5 km down the flanks as of 6 April and was incandescent at various locations. Incandescent material originating from the edges of the lava dome and flow traveled up to 2 km S and 500 m SE. Tremor and volcanic earthquakes were detected, and signals representing avalanches from the unstable and still-growing dome decreased. Sulfur dioxide emissions varied but were relatively insignificant. The Alert Level was lowered to 3 (on a scale of 1-4). Visitors and tourists were prohibited from approaching the crater within a radius of 5 km on the S and SE flanks, and 3 km in the other directions.

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)