Volcanic ash from Semeru volcano observed at 4 300 m (14 100 feet) a.s.l., Indonesia

Volcanic ash from Semeru in Indonesia was observed at 4 300 m (14 100 feet) above sea level at 16:00 UTC on October 8, 2025. The advisory was issued by the Darwin VAAC at 16:33 UTC.

According to the VAAC advisory, the ash cloud was reported between surface level and flight level 140 (approximately 4 300 m or 14 100 feet). The motion of the ash was generally toward the west at approximately 9 km/h (5 mph). The ash cloud was not identifiable on recent satellite imagery due to meteorological cloud cover. The current Aviation Color Code is Orange. The reported height and forecast were based on ground observations and model guidance.

The Smithsonian / USGS Weekly Volcanic Activity Report for September 24–30, 2025, states that Semeru continued eruptive activity during that period. Daily eruptive events produced white-and-gray or gray ash plumes rising 400–900 m above the summit and drifting in multiple directions. The Alert Level remained at 2, with warnings to stay at least 3 km from the summit in all directions and up to 8 km to the southeast due to possible hazards.

Semeru is a large stratovolcano located in East Java, Indonesia. Hazards from this volcano include explosive eruptions, ashfall, pyroclastic flows, lava flows, and lahars. Populations at risk include those in nearby villages such as Sumbersari and Pronojiwo within 20 km (12 miles) of the summit. Ongoing activity poses a persistent risk to surrounding communities and aviation in the region.