Ash emissions 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 17:10 UTC on October 16, 2025. The advisory was issued by the Darwin VAAC at 17:30 UTC.

Ash was observed between the surface and flight level 140, which corresponds to approximately 4 300 m (14 100 feet) above sea level. Ash movement was reported towards the west at 9 km/h (6 mph). The presence of volcanic ash was based on satellite imagery (Himawari-8) and ground reports, but recent satellite imagery did not clearly show the ash cloud due to meteorological cloud cover. Discrete eruptions were reported as ongoing. The current Aviation Color Code is Orange.

According to the Smithsonian / USGS Weekly Volcanic Activity Report for the period of September 24–30, 2025, Semeru exhibited daily eruptive events with white-and-gray or gray ash plumes rising 400–900 m (1 300–2 950 feet) above the summit, drifting in multiple directions. The Alert Level remained at 2. The public was warned to stay at least 3 km (1.9 miles) away from the summit in all directions, 8 km (5 miles) to the southeast, and to avoid river drainages due to lahar, avalanche, and pyroclastic flow hazards.

Semeru is a stratovolcano located in East Java, Indonesia. Known hazards from Semeru include ashfall, pyroclastic flows, lava flows, and lahars. Settlements at risk include villages on the lower slopes and the city of Lumajang, located approximately 35 km (22 miles) to the southeast of the volcano.