PVMBG reported that foggy weather often prevented visual observations of Sinabung during 19-25 May, except for a few clearer periods on some days. White plumes rose as high as 800 m during 19-20 and 22-24 May. Lava from the lava dome was active as far as 1.5 km S during 21-23 May. On 24 May a pyroclastic flow traveled 2 km down the S flank and produced an ash plume that rose 500 m. Seismicity consisted of avalanche signals, low-frequency and hybrid events, tectonic events, and volcanic earthquakes; RSAM values increased due to an increase of avalanche signals. 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)