Based on visual observations, CVGHM reported that during 18-25 June ash plumes from Karangetang's main crater produced plumes that rose to an altitude of 2 km (6,600 ft) a.s.l. Activity at Crater II consisted of diffuse ash plumes that rose to an altitude of 1.8 km (5,900 ft) a.s.l. and incandescent ash that rose about 10 m. The Alert Level remained at 2 (on a scale of 1-4).

Geological Summary. Karangetang (Api Siau) volcano lies at the northern end of the island of Siau, about 125 km NNE of the NE-most point of Sulawesi. The stratovolcano contains five summit craters along a N-S line. It is one of Indonesia's most active volcanoes, with more than 40 eruptions recorded since 1675 and many additional small eruptions that were not documented (Neumann van Padang, 1951). Twentieth-century eruptions have included frequent explosive activity sometimes accompanied by pyroclastic flows and lahars. Lava dome growth has occurred in the summit craters; collapse of lava flow fronts have produced pyroclastic flows.

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