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

Volcanic ash from Semeru volcano in Indonesia was observed at an altitude of 4 300 m (14 100 feet) above sea level at 03:10 UTC on October 26, 2025. The advisory was issued by the Darwin VAAC at 03:30 UTC.

Ground-based reports indicated intermittent discrete eruptions, with ash cloud heights and movement based on observations at 20:56 UTC on October 25 and model guidance. The ash cloud was reported between the surface and 4 300 m (14 100 feet) and was moving west at 19 km/h (12 mph). The cloud’s forecast extended at similar levels up to 18 hours ahead. The current Aviation Color Code is Orange. Ash was not identifiable in satellite imagery due to meteorological cloud cover.

According to the Smithsonian/USGS Weekly Volcanic Activity Report, Semeru volcano showed ongoing eruptive activity during September 24–30, 2025. Daily seismic records indicated frequent eruptions, with ash plumes rising 400–900 m (1 300–3 000 feet) above the summit and drifting in multiple directions. The Alert Level remained at 2, with warnings for the public to stay at least 3 km (1.9 miles) away from the summit and avoid several drainages due to lahar and pyroclastic flow hazards.

Semeru is a stratovolcano located in East Java, Indonesia, and is the highest volcano on the island. Known hazards include ashfall, pyroclastic flows, lava flows, and lahars. The nearby population is most concentrated in the town of Lumajang, situated approximately 22 km (14 miles) southeast of the volcano. Semeru’s frequent activity poses ongoing risks to local settlements and infrastructure, particularly in river valleys downstream from the summit.