PVMBG reported that foggy weather prevented visual observations of Sinabung during 4-12 May, except for a few clearer periods on some days. On 4 May dense white-to-gray plumes rose 700 m above the summit. During 7-11 May white plumes rose as high as 700 m. Lava from the dome traveled 1 km S on 10 May. A pyroclastic flow originating from the lava dome traveled 3 km S on 12 May, and produced ash plumes mainly obscured by fog. Seismicity consisted of avalanche signals, low-frequency and hybrid events, tectonic events, and volcanic earthquakes; levels declined overall. The Alert Level remained at 3 (on a scale of 1-4). Visitors and tourists were prohibited from approaching the crater within a radius of 6 km on the S, 5 km on the 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)