Volcanic ash from Semeru volcano observed at 4 600 m (15 100 feet) a.s.l., Indonesia

Volcanic ash from Semeru volcano in Indonesia was observed at 4 600 m (15 100 feet) above sea level at 13:30 UTC on August 21, 2025. The advisory was issued by the Darwin VAAC at 14:00 UTC on the same day.

According to the VAAC advisory, the ash cloud was observed at an altitude extending from the surface up to 4 600 m (15 100 feet). The ash cloud was moving west at a speed of approximately 19 km/h (12 mph). Ash was not identifiable on the latest satellite imagery due to meteorological cloud cover, but ground reports indicated ongoing intermittent eruptions. The current Aviation Color Code is Orange.

The Smithsonian / USGS Weekly Volcanic Activity Report for August 13–19, 2025, notes that Semeru experienced frequent eruptive events, with daily white-and-gray ash plumes rising 500–1 000 m (1 600–3 300 feet) above the summit and drifting in multiple directions. Minor incandescence was observed at the summit. The volcano remained at Alert Level 2, with the public advised to stay at least 3 km (1.9 miles) from the summit and 8 km (5 miles) to the southeast due to potential hazards.

Semeru is a stratovolcano located in East Java, Indonesia, and is the highest volcano on the island at 3 657 m (11 998 feet). It is known for frequent explosive eruptions that produce ashfall, pyroclastic flows, and lava avalanches. Nearby settlements, including the towns of Lumajang and Malang, are at risk from volcanic hazards, particularly lahars, pyroclastic flows, and ash clouds.