Based on observations conducted at the Karangetang Volcano Observation Post in the village of Salili, PVMBG reported during 9-16 September that lava fountains rose as high as 250 m and lava flows traveled as far as 2.5 km. Incandescent avalanches from the fronts of 150-m-long lava flows traveled as far as 2.5 km E down the Batuawang and Kahetang drainages. Seismicity was dominated by multi-phase earthquakes and signals characteristic of avalanches, with rare volcanic earthquakes. The Alert Level remained at 3 (on a scale of 1-4); visitors and residents were warned not to approach Karangetang within a 4-km radius.

Based on analyses of satellite imagery and wind data, the Darwin VAAC reported that during 16-17 September ash plumes rose to altitudes of 2.4-3 km (6,000-10,000 ft) a.s.l. and drifted 30-85 km NE, E, and ESE.

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: Darwin Volcanic Ash Advisory Centre (VAAC), Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as CVGHM)