Ash emissions from Semeru volcano reach 4 300 m (14 100 feet) a.s.l., Indonesia

Volcanic ash from Semeru in Indonesia was observed at an altitude of 4 300 m (14 100 feet) above sea level at 17:10 UTC on October 17, 2025. The advisory was issued by the Darwin VAAC at 17:29 UTC.

According to the advisory, the ash cloud was reported between the surface and flight level 140, corresponding to approximately 4 300 m (14 100 feet). The direction of movement was west at approximately 28 km/h (17 mph). Satellite imagery could not identify the ash cloud due to meteorological cloud cover, but multiple ground reports indicated intermittent discrete eruptions were ongoing. The current Aviation Color Code is Orange.

The most recent Smithsonian / USGS Weekly Volcanic Activity Report states that Semeru exhibited daily eruptive activity between September 24 and September 30, 2025. Ash plumes during that period rose 400–900 m (1 300–3 000 feet) above the summit, with continuing seismic events and public exclusion zones remaining in effect up to 8 km (5 miles) from the summit to the southeast due to hazard concerns.

Semeru is a stratovolcano and the highest volcano on Java, Indonesia. It regularly produces ash emissions, pyroclastic flows, and occasional lava domes. Known hazards include ashfall, lava flows, pyroclastic density currents, and lahars that may impact nearby settlements, with the town of Lumajang and surrounding villages at particular risk. Residents and visitors are advised to maintain distance consistent with official hazard zone recommendations.