PVMBG reported that Ibu continued to erupt. A few notable eruptive events occurred during 24-29 April. On 24 April ash plumes rose 800-1,500 m above the summit and roaring was heard at the Ibu observation post (9 km W). On 26 April an eruptive event produced a dense gray ash plume that rose 2 km and drifted SW and W, incandescence that emanated about 700 m from the summit, a boom followed by a roaring noise, and ashfall in residential areas downwind. At 0037 on 28 April an ash plume rose 3.5 km and produced lightning in the plume. Booming and roaring was heard at the observation post and ash fell in residential areas to the W. At 2137 on 29 April a dense gray ash plume rose around 1 km and drifted W and NW; incandescent material was ejected 500 m NW, W, and SW. Booming and rumbling was heard at the observation post. During 1-2 and 5 May dense gray or gray-and-white ash plumes rose as high as 2 km and drifted in multiple directions. White steam-and-gas plumes rose as high as 300 m and drifted E, SE, and S on 4 May. An eruptive event was recorded by the seismic network on 6 May but was not visually confirmed. The Alert Level remained at 2 (the second highest level on a four-level scale) and the public was advised to stay 3.5 km away from the active 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)