PVMBG reported that dense white gas-and-steam plumes from Karangetang were visible rising as high as 100 m and drifting E, NE, NW, and W on most days during 19-25 July. The Darwin VAAC noted that ash plumes rose as high as 2.4 km (8,000 ft) a.s.l. at 1710 on 21 July, at 1530 on 22 July, and at 0850 on 23 July, that drifted NE and E. According to a news source, lava avalanches traveled more than 1.7 km down the Kahetang drainage, 1 km down the Batuawang and Batang drainages, 800 m down the Timbelang drainage, and about 1.5 km down the West Beha drainage during 21-22 July. Dense gray-to-white plumes sometimes accompanied the lava avalanches. The Alert Level remained at 3 (on a scale of 1-4) and the public were advised to stay 2.5 km away from Main Crater with an extension to 3.5 km on the S and SE flanks.

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), Darwin Volcanic Ash Advisory Centre (VAAC), Antara News, Antara News