Ash cloud 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 03:30 UTC on October 11, 2025. The advisory was issued by the Darwin VAAC at 04:00 UTC on the same day.

The ash cloud was reported in the surface to flight level 140 (approximately 4 300 m or 14 100 feet) and was moving southwest at a speed of 28 km/h (17 mph). Ash could not be identified in recent satellite imagery due to meteorological cloud cover. The ongoing eruptions were reported by CVGHM, and the ash cloud height and forecast are based on ground observations and model guidance. The current Aviation Color Code is Orange.

According to the Smithsonian / USGS Weekly Volcanic Activity Report, Semeru displayed daily eruptive activity during the week of September 24–30, 2025, with white-and-gray ash plumes rising 400–900 m (1 300–3 000 feet) above the summit and drifting in multiple directions. The alert level remained at 2, and the public was advised to remain at least 3 km (1.9 miles) from the summit and avoid specific drainages due to lahar, avalanche, and pyroclastic flow risks.

Semeru is an active stratovolcano located in East Java, Indonesia. It is Indonesia’s highest volcano and is known for frequent explosive eruptions that can produce ashfall, lava flows, and hazardous pyroclastic flows. Nearby populations at risk include villages on the flanks of the volcano such as Pronojiwo and Lumajang, and areas downstream of river valleys prone to volcanic flows.