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

Volcanic ash from Semeru in Indonesia was observed at 4 300 m (14 100 feet) above sea level at 21:40 UTC on October 9, 2025. The advisory was issued by the Darwin VAAC at 22:00 UTC on the same day.

Ash was reported by ground observers to reach flight level 140, which is approximately 4 300 m (14 100 feet) above sea level. The ash cloud was moving west at approximately 9 km/h (5 mph). Recent satellite imagery from Himawari-9 could not identify volcanic ash due to meteorological cloud cover; ash height and movement were therefore based on ground reports and model guidance. The current Aviation Color Code is Orange.

According to the Smithsonian / USGS Weekly Volcanic Activity Report for September 24-30, 2025, activity continued at Semeru with daily eruptive events. White-and-gray or gray ash plumes rose 400–900 m above the summit and drifted in multiple directions. The public was advised to stay at least 3 km (1.9 miles) from the summit in all directions, and farther in certain areas due to hazards.

Semeru is a stratovolcano and the highest volcano on Java, Indonesia. Its steep slopes and persistent eruptions pose hazards including ashfall, lava flows, pyroclastic flows, and lahars. Nearby communities, including the town of Lumajang located about 40 km (25 miles) to the southeast, may be at risk during significant eruptive episodes.