Mount Semeru on the border of Lumajang and Malang in East Java erupted 16 times on Wednesday morning. The highest eruption reached 1,100 meters above the summit at 05:55 WIB. PVMBG recommends residents avoid hazardous areas to prevent disaster risks.
Mount Semeru, Java's highest volcano, recorded 16 eruptions from 00:31 WIB to 08:42 WIB on Wednesday, December 3, 2025. The first eruption at 00:31 WIB produced a column 500 meters above the summit, while the last at 08:42 WIB was obscured by fog.
The tallest eruption occurred at 05:55 WIB, reaching 1,100 meters above the summit or 4,776 meters above sea level. "The eruption with the highest plume happened at 05:55 WIB, observed at about 1,100 meters above the summit or 4,776 mdpl," said Semeru Observation Post officer Liswanto in a written report.
The ash column was white to gray with medium intensity drifting southwest, and eruptions continued at the time of reporting. Seismic monitoring from 00:00 to 06:00 WIB detected 53 eruption quakes with amplitudes of 11-22 mm, 26 avalanche quakes at 4-7 mm, and one tremor at 6 mm.
The volcano's status remains Alert or Level III. The Center for Volcanology and Geological Hazard Mitigation (PVMBG) prohibits activities in the southeast sector and along Besuk Kobokan up to 13 km from the summit. Beyond that, people must stay 500 meters from the riverbanks of Besuk Kobokan due to risks of hot clouds and lahars extending to 17 km. Activities are also banned within a 5 km radius of the crater owing to potential rock ejections.
Residents are urged to beware of hot clouds, lava avalanches, and lahars in rivers such as Besuk Kobokan, Besuk Bang, Besuk Kembar, Besuk Sat, and their tributaries.