The latest eruption of Sinabung that began mid-September 2013 (BGVN 38:09) had persisted through April 2016 (BGVN 41:09). This report describes the continuing activity from May-October 2016, and unfortunately included a fatality. Data were primarily drawn from reports issued by the Indonesian Center of Volcanology and Geological Hazard Mitigation (PVMBG, CVGHM), the Darwin Volcanic Ash Advisory Centre (VAAC), and the Badan Nacional Penanggulangan Bencana (National Disaster Management Authority, BNPB).

Inclement weather sometimes prevented visual observations. Throughout the reporting period, the Alert Level remained at 4 (on a scale of 1-4), indicating that the public should remain outside of a 3-km radius; those within 7 km of the volcano on the SSE sector, and within 6 km in the ESE sector, and 4 km in the NNE sector should evacuate.

According to the Darwin VAAC and PVMBG reports, a number of ash plumes were observed each month (table 6). They generally rose to altitudes of 3.3-5.5, although one rose as high as 5.9 km.

Table 6. Ash plumes with altitudes and drift directions reported at Sinabung from May 2016 to October 2016. Weather clouds often prevented observations. Courtesy of PVMBG, Darwin VAAC, and BNPB.

According to BNPB, a lahar passed through Kutambaru village, 20 km NW of Sinabung and near the Lau Barus River, at 1545 on 9 May 2016, killing a boy and injuring four more. One person was missing. A news article (Okezone News) noted that three houses were also damaged.

BNPB reported that a pyroclastic flow descended the flanks at 1648 on 21 May, killing six people and critically injuring three more. A later CBS news account on 22 May indicated that seven people had died, with two in critical condition. The victims were gardening in the village of Gamber, 4 km SE from the summit crater, in the restricted zone. The report noted that activity remained high; four pyroclastic flows descended the flanks on 21 May.

On 3 July, BNPB reported that the eruption continued at a very high level. Lava was incandescent as far as 1 km down the SE and E flanks, and multiple avalanches were detected. An explosion at 1829 generated an ash plume that rose 1.5 km and drifted E and SE, causing ashfall in Medan (55 km NE). There were 2,592 families (9,319 people) displaced to nine shelters, and an additional 1,683 families in temporary shelters waiting for relocation.

According to BNPB, on 24 August, observers at the PVMBG Sinabung observation post noted a marked increase in seismicity and counted 19 pyroclastic flows and 137 avalanches from the early morning until the late afternoon. Foggy conditions obscured visual observations through most of the day, although incandescent lava as far as 500 m SSE and 1 km ESE was noted in the morning, and a pyroclastic flow was seen traveling 3.5 km ESE at 1546. The lava dome had grown to a volume of 2.6 million cubic meters. Activity remained very high on 25 August; pyroclastic flows continuously descended the flanks, traveling as far as 2.5 km E and SE, and 84 avalanches occurred during the first part of the day.

Thermal anomalies. During the reporting period, thermal anomalies, based on MODIS satellite instruments analyzed using the MODVOLC algorithm, occurred during one to five days every month. Only three days had more than one pixel (1, 3 May, 8 October). The Mirova (Middle InfraRed Observation of Volcanic Activity) volcano hotspot detection system, also based on analysis of MODIS data, detected thermal anomalies every month during the reporting period within 5 km of the volcano, with the heaviest concentration in May and fewest in September and October.

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: Badan Nasional Penanggulangan Bencana (BNPB), National Disaster Management Agency, Graha BNPB - Jl. Scout Kav.38, East Jakarta 13120, Indonesia (URL: http://www.bnpb.go.id/); 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/); 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/); MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/); Okezone News (URL: http://news.okezone.com/); CBS News (URL: http://www.cbsnews.com/).