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

Volcanic ash from Semeru volcano in Indonesia was observed at an altitude of 4 600 m (15 000 feet) above sea level at 15:10 UTC on November 4, 2025. The advisory was issued by the Darwin VAAC at 15:30 UTC on the same day.

According to the advisory, volcanic ash was observed in the area from the surface up to 4 600 m (15 000 feet). The ash cloud was reported moving northeast at a speed of approximately 19 km/h (12 mph). Satellite detection was not possible due to meteorological cloud cover, but recent ground reports indicate intermittent discrete eruptions are ongoing. The reported ash height and movement are based on ground observations and model guidance. The current Aviation Color Code is Orange.

The Smithsonian / USGS Weekly Volcanic Activity Report for September 24–30, 2025, notes that Semeru continued to experience daily eruptive events, with ash plumes rising 400–900 m above the summit and drifting in multiple directions. The public is advised to remain at least 3 km (1.9 miles) from the summit, 8 km (5 miles) from the summit to the southeast, and to avoid river drainages due to lahar, avalanche, and pyroclastic flow hazards.

Semeru is Indonesia’s highest volcano and is classified as a stratovolcano. It is known for frequent explosive eruptions that can produce ashfall, pyroclastic flows, and volcanic mudflows (lahars). Populations at risk include those living in villages near the eastern and southern slopes, such as Pronojiwo and Lumajang, located within 25 km (16 miles) of the volcano. Ongoing activity at Semeru poses persistent hazards to these nearby populations, as well as to aviation in the region.