CVGHM reported that white plumes from Ibu rose to an altitude of 1.5 km (5,000 ft) a.s.l. during 17-31 March and were spotted "often." The plume altitudes increased to 1.6 km (5,200 ft) a.s.l. on 31 March. During 4-5 April, seismicity increased in amplitude and plume altitude increased to 1.8-2.0 km (5,900-6,600 ft) a.s.l. On 5 April, the eruption plume was gray and material fell onto the crater. The Alert Level remained at 2 (on a scale of 1-4). The community was not permitted to climb or approach the crater.

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.

Source: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as CVGHM)