Based on a SIGMET, the Darwin VAAC reported that an ash plume from Soputan rose to an altitude of 5.5 km (18,000 ft) a.s.l. on 18 January. BNPB reported that an eruption at 1138 that same day generated an ash plume that rose 4 km and drifted SW; the report did not specify if 4 km was height above volcano or altitude a.s.l. Strombolian activity ejected material 500 m above the crater and incandescent avalanches of material traveled 500 m down the SW flank. The Alert Level was at 3 (on a scale of 1-4).

Geological Summary. The Soputan stratovolcano on the southern rim of the Quaternary Tondano caldera on the northern arm of Sulawesi Island is one of Sulawesi's most active volcanoes. The youthful, largely unvegetated volcano is the only active cone in the Sempu-Soputan volcanic complex, which includes the Soputan caldera, Rindengan, and Manimporok (3.5 km ESE). Kawah Masem maar was formed in the W part of the caldera and contains a crater lake; sulfur has been extracted from fumarolic areas in the maar since 1938. Recent eruptions have originated at both the summit crater and Aeseput, a prominent NE-flank vent that formed in 1906 and was the source of intermittent major lava flows until 1924.

Sources: Badan Nacional Penanggulangan Bencana (BNPB), Darwin Volcanic Ash Advisory Centre (VAAC)