The latest eruption of Sinabung began in mid-September 2013 (BGVN 38:09) and was previously described through October 2014 (BGVN 39:01 and 39:10). This report describes the continuing eruption from November 2014 through April 2015. Data were primarily drawn from reports issued by the Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as Center for Volcanology and Geological Hazard Mitigation) and the Darwin Volcanic Ash Advisory Centre (VAAC).

The Alert Level remained at 3 (on a scale of 1-4) throughout the reporting period. 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. According to the Badan Nacional Penanggulangan Bencana (National Disaster Management Authority, BNPB), by the middle of November, activity had displaced 2,086 people from 956 households.

Activity fluctuated during the reporting period, with frequent explosions, intermittent pyroclastic flows, and lava flows. Explosions generated ash plumes that generally rose to altitudes of 3-4.6 km. According to PVMBG, a new lava dome began to develop in October 2014 on the W side of the SSE-flank lava flow.

On 14 November there were 79 avalanches reported, with three of them generating pyroclastic flows that traveled 4 km S. PVMBG reported that 53 pyroclastic flows occurred during 8-16 December 2014 and they traveled as far as 4.5 km S and 1 km SE; ash plumes rose as high as 5 km. By 15 December the dome was 215 m long and the main lava flow was about 3 km long.

BNPB reported that an explosion in the evening of 3 January 2015 was larger than previous, almost daily, explosions. Pyroclastic flows traveled 2-4 km down the flanks and ash plumes rose as high as 3 km. Ashfall was reported in Payung (5 km SSW), Tiganderket (7 km W), Selandi (5 km SSW), Juhar (20 km SW), and Laubaleng (35 km WSW).

On 18 January BNPB reported that activity remained high, with low-frequency earthquakes and constant tremor being recorded. A pyroclastic flow traveled 2 km S and ash plumes rose 700 m. The number of displaced people had increased to 2,443 (795 families).

Elevated activity continued through February and March 2015. Plumes on 20 February and 5 March 2015 rose to altitudes as high as 13.7 km and 9.1 km, respectively. Based on PVMBG notices, BNPB reported that activity increased on 1 April. Seismicity increased and pyroclastic flows traveled 3.5 km S and produced ash plumes that rose 2 km. Avalanches were detected and incandescent lava was observed at night. On 2 April pyroclastic flows traveled 4 km S and 1 km SE, and avalanches continued.

PVMBG reported that seismicity declined during 6-12 April, compared to 30 March-6 April. However, lava was incandescent as far as 1.5 km S and SE of the lava dome. The main lava flow remained 2.9 km long. After pyroclastic flows descended the flanks on 2 April, a new lava flow from the growing dome formed near the crater and traveled 170 m SSE. Seismicity consisted of avalanche signals, low-frequency and hybrid events, local and distant tectonic events, and volcanic earthquakes. Tilt and EDM (Electronic Distance Measurement) data fluctuated but showed overall deflation.

Thermal anomalies, based on MODIS satellite instruments analyzed using the MODVOLC algorithm, were observed an average of 3-5 days per month during the reporting period. Four pixels were observed 8 and 15 December 2014, 5 March 2015, and 2 April 2015, and five pixels were observed on 13 December 2015.

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.

Information Contacts: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as Indonesian Center for Volcanology and Geological Hazard Mitigation, CVGHM), Jalan Diponegoro 57, Bandung 40122, Indonesia (URL: http://www.vsi.esdm.go.id/); Darwin Volcanic Ash Advisory Centre (VAAC), Bureau of Meteorology, Northern Territory Regional Office, PO Box 40050, Casuarina, NT 0811, Australia (URL: http://www.bom.gov.au/info/vaac/); Badan Nacional Penanggulangan Bencana (National Disaster Management Authority, BNPB) (URL: http://www.bnpb.go.id/); Hawai'i Institute of Geophysics and Planetology (HIGP) MODVOLC Thermal Alerts System, School of Ocean and Earth Science and Technology (SOEST), Univ. of Hawai'i, 2525 Correa Road, Honolulu, HI 96822, USA (URL: http://modis.higp.hawaii.edu/)