Mount Semeru Erupts Again Tonight, Ash Plume Approximately 700 Meters High

Mount Semeru in East Java erupted again on Thursday (December 11, 2025) at 09:20 PM Western Indonesian Time (WIB). In the last week, Mount Semeru has erupted 29 times.

Based on eruption information from the Center for Volcanology and Geological Hazard Mitigation (PVMBG) via the MAGMA Indonesia application, the ash plume was observed to be approximately 700 meters above the peak or 4,376 meters above sea level.

The ash plume was observed to be white to grey with thick intensity towards the southwest. The eruption was recorded on a seismograph with a maximum amplitude of 22 millimeters and a duration of 152 seconds.

(Read: Volcanic Eruption Trends in Recent Years)

According to MAGMA Indonesia's volcanic activity report, Mount Semeru's activity level is at Level III (Alert). Seismic observations on December 11, 2025, from 12:00 PM to 06:00 PM WIB, showed 37 eruption tremors with amplitudes of 10-23 millimeters and durations of 67-132 seconds.

Furthermore, there were 2 avalanche tremors with amplitudes of 2-5 mm and durations of 48-59 seconds, and 4 emission tremors with amplitudes of 4-7 millimeters and durations of 54-90 seconds.

PVMBG advises against any activities in the southeast sector along Besuk Kobokan, as far as 13 kilometers from the peak (eruption center). Beyond that distance, the public is advised not to engage in activities within 500 meters from the riverbanks (river border) along Besuk Kobokan, as there is a potential for hot cloud expansion and lahars to extend up to 17 kilometers from the peak.

Throughout 2025, MAGMA Indonesia has recorded 7,305 volcanic eruptions across Indonesia. Mount Semeru in East Java has erupted the most, with 3,007 eruptions.

(Read: Countries with the Most Active Volcanoes in the World, Indonesia Ranks First)