Warning! Mount Semeru Erupts Again Tonight (Monday, December 1, 2025)

Mount Semeru in East Java erupted again on Monday (12/1/2025) at 19:37 WIB. In the last week, Mount Semeru has erupted 12 times.

According to eruption information from the Center for Volcanology and Geological Hazard Mitigation (PVMBG) via the MAGMA Indonesia application, the height of the observed ash column reached 800 meters above the peak (4,476 meters above sea level).

The ash column 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 19 millimeters and a duration of 103 seconds.

(Read: West Kalimantan Produced the Most CO2 Emissions from Forest Fires Until July 2023)

According to the MAGMA Indonesia volcanic activity report, Mount Semeru's activity level is at Level III (Alert). Seismic observations on December 1, 2025, from 12:00-18:00 WIB showed 36 eruption tremors/earthquakes with amplitudes of 10-22 millimeters and durations of 53-139 seconds.

Furthermore, there were 10 rockfall earthquakes with amplitudes of 2-18 mm and durations of 49-96 seconds, and 7 exhalation earthquakes with amplitudes of 6-7 millimeters and durations of 66-117 seconds.

PVMBG advises against any activity in the southeast sector along Besuk Kobokan, as far as 13 kilometers from the peak (eruption center). Beyond that distance, people should not engage in activities within 500 meters from the riverbanks (river borders) along Besuk Kobokan, as there is a potential for expansion of hot clouds and lava flows up to 17 kilometers from the peak.

Throughout 2025, MAGMA Indonesia has recorded 7,135 volcanic eruptions across Indonesia. Mount Semeru in East Java had the most eruptions, with 2,891 occurrences.

(Read: Indication of Forest Fire Area in Central Kalimantan Province in the Last Decade)