Intermittent weak explosions at Gamalama resulting in ash plumes have occurred for many decades, most recently in September 2012, December 2014, and July-September 2015 (BGVN 40:12). This report covers activity between 1 December 2015 and February 2017. 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).

During 1 January-6 March 2016, PVMBG noted that seismicity fluctuated but decreased overall; shallow volcanic earthquakes and signals indicating emissions appeared on 3 March and a series of deep volcanic earthquakes were detected on 6 March. The Alert Level remained at 2 (on a scale of 1-4), and visitors and residents were warned not to approach the crater within a 1.5-km radius.

PVMBG reported that, at 0628 on 3 August 2016, a weak explosion generated an ash plume that rose 500-600 m above the crater and drifted SE and S. Ash emissions decreased at 0655. Consistent with this, the Darwin VAAC, based on analyses of satellite imagery and wind model data, and information from PVMBG, reported that ash plumes reached a maximum altitude of 2.7 km (summit elevation is 1.7 km) and drifted S, SE, E, and NE. Ashfall was reported in areas on the SSE flank, including the Ake Huda area.

A news account (Jakarta Globe) stated that the Babullah Airport in Ternate, North Maluku, was closed for a day while volcanic ash was cleared from the runway (about 6 km ENE of the volcano). On 5 August PVMBG noted that seismicity continued to be elevated, although inclement weather prevented visual observations.

Geological Summary. Gamalama is a near-conical stratovolcano that comprises the entire island of Ternate off the western coast of Halmahera, and is one of Indonesia's most active volcanoes. The island was a major regional center in the Portuguese and Dutch spice trade for several centuries, which contributed to the extensive documentation of activity. Three cones, progressively younger to the north, form the summit. Several maars and vents define a rift zone, parallel to the Halmahera island arc, that cuts the volcano; the S-flank Ngade maar formed after about 14,500–13,000 cal. BP (Faral et al., 2022). Eruptions, recorded frequently since the 16th century, typically originated from the summit craters, although flank eruptions have occurred in 1763, 1770, 1775, and 1962-63.

Information Contacts: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as Center of 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/); Jakarta Globe (URL: http://jakartaglobe.id/).