On 2 August, the Alert Level at Karangetang was raised to 4, the highest level. During 1-5 August, white plumes reached heights of 50-300 m (164-984 ft) above the summit (6,000-6,800 ft a.s.l.). Lava flows advanced hundreds of meters to over a kilometer E toward the Batu Awang river and S towards the Keting river during the reporting period. Incandescent rockfalls originating from the summit and ends of the lava flows traveled hundreds of meters E toward the Kahetang and Batu Awang rivers and S towards the Keting and Batang rivers. On 5 August, the Alert level was lowered to 3.

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)