Volcanic ash from Semeru volcano observed at 4 600 m (15 000 feet) a.s.l., Indonesia

Volcanic ash from Semeru in Indonesia was observed at 4 600 m (15 000 feet) above sea level at 03:20 UTC on November 5, 2025. The advisory was issued by the Darwin VAAC at 03:40 UTC.

According to the VAAC advisory, ash was reported between the surface and flight level 150, corresponding to approximately 4 600 m (15 000 feet). The ash cloud was reported moving northeast at 18 km/h (11 mph). Ash cloud height and movement were determined by ground observations and model guidance, as the ash cloud was not identifiable in satellite imagery due to meteorological cloud cover. The current Aviation Color Code is Orange.

The most recent Global Volcanism Program summary for Semeru (report for September 24–30, 2025) indicates ongoing eruptive activity with daily seismic events and ash plumes rising 400–900 m (1 300–3 000 feet) above the summit. The Alert Level remained at 2 (on a scale of 1–4). The public was advised to stay at least 3 km (1.9 miles) away from the summit in all directions, 8 km (5 miles) from the summit to the southeast, and to avoid riverbanks in certain drainages due to lahar, avalanche, and pyroclastic flow hazards.

Semeru is a stratovolcano located in East Java, Indonesia. It is the highest volcano on Java and is known for frequent explosive eruptions, producing ashfall and pyroclastic flows. Hazards include ashfall, lava flows, and pyroclastic density currents, which can threaten nearby populations, including the locality of Lumajang, situated approximately 25 km (16 miles) southeast of the volcano.