VSI reported that at Karangetang during 25 February-3 March small volcanic plumes were emitted, a "red reflection" extended 25 m above the crater, and seismicity was high although it decreased in comparison to the previous week. A pilot report to the Darwin VAAC stated that a layer of apparent ash was seen on 5 March at 1544. The layer was located 18.5-37 km from Karangetang at an altitude near 7.5 km (winds in the area suggest ash was at least as high as ~5.5 km). The Karangetang Volcano Observatory reported that an explosion at 1344 the same day rose 1 km above the volcano's summit (2.8 km a.s.l.). No ash was visible in satellite imagery under clear conditions; the ash layer may have been too thin to detect. The volcano remained at Alert Level 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.

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