Mount Semeru saw increased seismic activity with 32 avalanche quakes over six hours on Thursday morning (20/11/2025). The Center for Volcanology and Geological Hazard Mitigation (PVMBG) urged the public to avoid the 8 km radius from the peak. The volcano's status remains at Level IV Alert since Wednesday night.
Mount Semeru, standing at 3,676 meters above sea level on the border of Lumajang and Malang regencies in East Java, erupted on Wednesday (19/11/2025) at 16:00 WIB. The eruption produced an ash column 2,000 meters above the peak, with hot clouds traveling up to 7 km southeast, and ash drifting north and northwest. The activity lasted 16 minutes 40 seconds with a maximum amplitude of 40 mm, ending at 18:11 WIB.
On Thursday (20/11/2025) from 00:00 to 06:00 WIB, the volcano recorded 32 avalanche quakes with amplitudes of 3-16 mm and durations of 69-108 seconds. Additionally, there were 25 eruption quakes with amplitudes of 10-22 mm and durations of 71-141 seconds, one exhalation quake with amplitude 3 mm and duration 67 seconds, and one distant tectonic quake with amplitude 30 mm, S-P 21 seconds, and duration 77 seconds. Visual observations showed the mountain clear to fog-covered 0-II, no crater smoke observed, cloudy weather, and weak winds from north, southeast, and south.
PVMBG raised the status to Level IV Alert since Wednesday at 17:00 WIB. Recommendations include prohibiting activities within an 8 km radius of the crater due to risks of flying incandescent material, no activities in the southeast sector along Besuk Kobokan up to 20 km from the peak, and 500 meters from riverbanks. The public is advised to beware of hot clouds, lava avalanches, and lahars in Besuk Kobokan, Besuk Bang, Besuk Kembar, Besuk Sat, and small tributaries of Besuk Kobokan.
Lumajang Regency Government declared an emergency response on Wednesday night. About 60 hikers and 15 guides trapped at Ranu Kumbolo (2,400 m above sea level) are safe and prepared for evacuation, though foggy weather delayed descent. A couple from Kediri suffered 20 percent burns after slipping on the slippery Gladak Perak Bridge due to hot ash; they were referred to Pasirian Hospital after initial treatment at Candipuro Health Center.
"Aktivitas Gunung Semeru untuk pengamatan kegempaan tercatat 32 kali gempa guguran dengan amplitudo 3-16 mm dan lama gempa 69-108 detik," said Yadi Yuliandi, Officer at the Mount Semeru Observation Post.
