During March 2014-March 2017, activity at Ibu consisted of lava-dome growth, occasional weak emissions containing ash (figure 11), and frequent thermal anomalies (BGVN 40:11 and 42:05). Ongoing activity between April and August 2017 consisted primarily of intermittent ash explosions. Data come from Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as CVGHM) and the Darwin Volcanic Ash Advisory Centre (VAAC).

Figure 11. Photo of an ash explosion from Ibu's central vent in November 2014. Courtesy of Tom Pfeiffer, Volcano Discovery.

On 3 April 2017, at 0757 (local), an explosion produced an ash plume that rose to an altitude of 1.7 km and drifted S. Seismic signals indicated explosions and avalanches. During the rest of April through August, occasional explosions generated weak ash plumes that generally rose to altitudes of 1.5-1.8 km (0.2-0.5 km above the volcano) and drifted in various directions (table 2).

Table 2. Ash plume data for Ibu, April-August 2017. Courtesy of PVMBG and Darwin VAAC.

Between April and August 2017, thermal anomalies (based on MODIS satellite instruments analyzed using the MODVOLC algorithm) were recorded 2-5 days per month, with no monthly trend. The MIROVA (Middle InfraRed Observation of Volcanic Activity) system detected numerous hotspots each month; all except one were within 3 km of the volcano, and all were of low or moderately-low power.

Geological Summary. The truncated summit of Gunung Ibu stratovolcano along the NW coast of Halmahera Island has large nested summit craters. The inner crater, 1 km wide and 400 m deep, has contained several small crater lakes. The 1.2-km-wide outer crater is breached on the N, creating a steep-walled valley. A large cone grew ENE of the summit, and a smaller one to the WSW has fed a lava flow down the W flank. A group of maars is located below the N and W flanks. The first observed and recorded eruption was a small explosion from the summit crater in 1911. Eruptive activity began again in December 1998, producing a lava dome that eventually covered much of the floor of the inner summit crater along with ongoing explosive ash emissions.

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/); 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/); 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/); Tom Pfeiffer, Volcano Discovery (URL: http://www.volcanodiscovery.com/).