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 09:10 UTC on October 26, 2025. The advisory was issued by the Darwin VAAC at 09:30 UTC on the same day.

According to the advisory, the ash cloud was reported at altitudes up to flight level 140, corresponding to about 4 300 m (14 100 feet). The motion of the ash cloud was to the west at approximately 19 km/h (12 mph). The current Aviation Color Code is Orange. Ash was not identifiable in satellite imagery due to meteorological cloud cover, but ground reports indicated intermittent discrete eruptions. The ash height and movement were based on earlier ground reports at 22:14 UTC on October 25 and model consensus guidance.

The most recent Smithsonian / USGS Weekly Volcanic Activity Report, covering September 24–30, 2025, states that daily eruptive events at Semeru continued, producing ash plumes rising 400–900 m above the summit and drifting in multiple directions. The Alert Level was at 2, with restrictions around the summit and nearby river drainages due to potential lahar, avalanche, and pyroclastic flow hazards.

Semeru is an active stratovolcano located in East Java, Indonesia. It is the highest volcano on Java, frequently producing ash plumes and pyroclastic flows. Hazards include ashfall, pyroclastic flows, and lahars that can threaten nearby communities such as Lumajang and Malang, situated within 20–50 km (12–31 miles) from the volcano.