Mount Semeru Erupts Again This Morning (Thursday, August 21, 2025)

Mount Semeru in East Java erupted again on Thursday (August 21, 2025) at 06:58 AM Western Indonesian Time. In the last week, Mount Semeru has erupted 21 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 800 meters above the peak or 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 21 millimeters and a duration of 150 seconds.

(Read: These are the Provinces Hit by Many Floods in Early 2025)

According to the MAGMA Indonesia volcano activity report, Mount Semeru's activity level is at Level II (Alert). Seismic observations on August 21, 2025, from 00:00 to 23:59 Western Indonesian Time showed 42 eruption tremors/earthquakes with amplitudes of 10-22 millimeters and durations of 58-146 seconds.

Furthermore, there were 2 rockfall tremors with amplitudes of 2-3 mm and durations of 65-75 seconds, and 14 gas emission tremors with amplitudes of 3-8 millimeters and durations of 32-85 seconds.

PVMBG advises against any activity in the southeast sector along Besuk Kobokan, as far as 8 kilometers from the peak (eruption center). Beyond that distance, the public should not engage in activities within 500 meters from the riverbanks along Besuk Kobokan, as there is potential for expansion of hot clouds and lava flows up to 13 kilometers from the peak.

Throughout 2025, MAGMA Indonesia has recorded 5,718 volcanic eruptions/explosions across Indonesia. Mount Semeru in East Java had the most eruptions, with 2,296 recorded.

(Read: Despite the Dry Season, Many Flood Disasters Occurred in Early July 2024)