Volcanic ash from Semeru volcano not detected as of October 18, 2025, Indonesia

Volcanic ash from Semeru in Indonesia was not observed at 23:00 UTC on October 18, 2025. The advisory was issued by VAAC Darwin at 23:30 UTC on the same day.

No ash cloud was detected on satellite imagery (Himawari-8), and ground reports confirmed absence of ash emissions for a 24-hour period prior to the advisory. The last reported volcanic ash was at flight level 140 (approximately 4 300 m or 14 000 feet) at 21:29 UTC on October 17, 2025. The current Aviation Color Code is Orange. This advisory has now been terminated, and no further advisories are expected unless circumstances change.

According to the Smithsonian / USGS Weekly Volcanic Activity Report for September 24–30, 2025, Semeru’s seismic network recorded daily eruptive events, producing white-and-gray ash plumes rising 400–900 m (1 300–3 000 feet) above the summit. The Alert Level was at 2 (second lowest on a scale of 1–4), and the public was advised to maintain safe distances from hazardous areas.

Semeru is a stratovolcano located in East Java, Indonesia. It is known for frequent explosive eruptions, with hazards including ashfall, pyroclastic flows, and lahars. Nearby communities such as Lumajang and Malang, along with areas close to drainages like Kobokan, are at risk from volcanic hazards depending on the scale and nature of eruptions. All distances, altitudes, and advisories are officially specified in metric units along with imperial equivalents.