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 4 300 m (14 100 feet) above sea level at 03:40 UTC on October 9, 2025. The advisory was issued by the Darwin VAAC at 04:00 UTC.

Ash was reported from the surface up to flight level 140 (approximately 4 300 m or 14 100 feet). The ash cloud was moving west at approximately 9 km/h (6 mph). The current Aviation Color Code is Orange. Recent satellite imagery did not detect volcanic ash due to meteorological cloud cover, but ground reports confirmed intermittent eruptions. The reported ash height and movement are based on ground observations and model guidance.

According to the Smithsonian / USGS Weekly Volcanic Activity Report for September 24–30, 2025, Semeru experienced daily eruptive events, with white-and-gray ash plumes rising 400–900 m above the summit and drifting in multiple directions. The alert level remained at 2 (the second lowest level on a scale of 1–4), and residents were advised to remain at least 3 km from the summit in all directions, 8 km to the southeast, 500 m from the banks of the Kobokan drainage as far as 13 km from the summit, and to avoid other drainages due to lahar, avalanche, and pyroclastic flow hazards.

Semeru is a large stratovolcano located in East Java, Indonesia. Known hazards include ashfall, pyroclastic flows, lava domes, and lahars, which can threaten nearby settlements such as Lumajang and areas along river drainages. The volcano has a history of frequent eruptions, and local populations remain at risk from rapidly changing volcanic conditions within a radius of several kilometers.