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 03:30 UTC on October 22, 2025. The advisory was issued by the Darwin VAAC at 04:00 UTC.

According to the advisory, intermittent discrete eruptions generated volcanic ash reaching flight level 140, or approximately 4 300 m (14 100 feet) above sea level. Ground reports at 22:07 UTC on October 21 indicated an eruption to 500 m (1 600 feet) above the summit. Ash movement was reported towards the west at a speed of 19 km/h (12 mph). The current Aviation Color Code is Orange. Volcanic ash was not identifiable in satellite imagery due to meteorological clouds; estimates are based on ground observation and model guidance.

The Global Volcanism Program reports that Semeru exhibited daily eruptive activity during late September 2025, with ash plumes rising 400–900 m (1 300–3 000 feet) above the summit. The public was advised to maintain a minimum distance of 3 km (1.9 miles) from the summit in all directions, and up to 8 km (5 miles) to the southeast, with additional exclusion zones along drainages due to lahar, avalanche, and pyroclastic flow hazards.

Semeru is a large stratovolcano located in East Java, Indonesia. It is the highest volcano on the island and is known for frequent explosive eruptions, often producing ashfall, pyroclastic flows, and lava domes. Settlements such as Lumajang and surrounding villages lie within tens of kilometers of the volcano and may be at risk from future activity, particularly from ashfall and downstream lahar flows.