Warning! Mount Semeru Erupts Again Tonight (Sunday, December 21, 2025)

Mount Semeru in East Java erupted again on Sunday (12/21/2025) at 00:26 WIB. In the last week, Mount Semeru has erupted 61 times.

Based on eruption information from the Center for Volcanology and Geological Hazard Mitigation (PVMBG) via the MAGMA Indonesia application, the height of the ash column was observed to be around 500 meters above the peak (4,176 meters above sea level).

The ash column was observed to be white to gray with moderate intensity towards the southwest. Mount Semeru's eruption was still ongoing when this report was made.

(Read: Distribution of Fatalities Due to Floods and Landslides in West Sumatra (December 9, 2025))

According to MAGMA Indonesia's volcano activity report, Mount Semeru's activity level is at Level III (Alert). Seismic observations on December 21, 2025, from 18:00-23:59 WIB showed 40 eruption earthquakes with amplitudes of 13-22 millimeters and earthquake durations of 71-131 seconds.

Furthermore, there were 5 avalanche earthquakes with amplitudes of 4-11 mm and durations of 38-49 seconds, and 3 harmonic earthquakes with amplitudes of 10-12 millimeters and durations of 94-144 seconds.

PVMBG urges 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 conduct activities within 500 meters from the riverbanks along Besuk Kobokan as there is a potential to be affected by the expansion of hot clouds and lava flows up to 17 kilometers from the peak.

Throughout 2025, MAGMA Indonesia has recorded 7,445 volcano eruptions across Indonesia. Mount Semeru in East Java had the most eruptions, with 3,085 occurrences.

(Read: Number of Houses Damaged by Floods and Landslides in Sumatra (December 16, 2025))