CVGHM reported that during 21-23 March incandescent material from Karangetang was ejected 50-75 m above the crater. Lava flows traveled as far as 2 km and collapses from the lava-flow fronts generated avalanches that moved down the flanks up to 300 m further. On 24 March lava was incandescent in areas 1.5 km away from the crater. Incandescent material from the lava-flow fronts rolled an additional 200-500 m down the flanks. Incandescent material was again ejected 75 m above the crater. Later that day, due to decreased seismicity and a decline in the lava-flow effusion rate, the Alert Level was lowered to 3 (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)