Ash plume from Semeru volcano reaches 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 09:10 UTC on November 4, 2025. The advisory was issued by the Darwin VAAC at 09:30 UTC.

The ash cloud was reported between the surface and flight level 150, corresponding to approximately 4 600 m (15 000 feet) based on recent ground observations and model guidance. The ash was moving east at about 19 km/h (12 mph). The current Aviation Color Code is Orange. Ash cloud was not identifiable on satellite imagery due to meteorological cloud cover; assessment is based on ground reports.

According to the Smithsonian / USGS Weekly Volcanic Activity Report for September 24-30, 2025, Semeru displayed daily eruptive events with white-and-gray or gray ash plumes rising 400-900 m above the summit and drifting in multiple directions. The Alert Level remained at 2 (on a scale of 1-4), with the public advised to maintain a safe distance due to ongoing hazards.

Semeru is Indonesia’s highest volcano, and is a stratovolcano known for frequent explosive eruptions, producing ashfall, lava flows, and pyroclastic flows. Settlements at risk include the town of Lumajang, located approximately 30 km (19 miles) southeast of the summit. Major hazards include ashfall affecting air quality and agriculture, lava and pyroclastic flows impacting river valleys, and lahars following heavy rainfall.