The Alert Status of Karangetang was raised on 18 August from 3 to 4 (on a scale of 1-4) due to increased eruptive activity, based on visual observation and increased seismicity. According to news articles, lava flowed about 1 km down the S slope and "booming" noises were heard. Thick ashfall covered villages, farms, and trees on the slopes.

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.

Sources: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as CVGHM), The Jakarta Post, Reuters, Agence France-Presse (AFP)