Mount Semeru Erupts Multiple Times, Maintains Level III Alert Status

Volcanic Activity Intensifies on Mount Semeru

Mount Semeru, an active volcano located in East Java, Indonesia, experienced a series of eruptions throughout Sunday, December 28, 2025. The eruptions, which began early Sunday morning, sent ash columns soaring up to 500 meters above its peak, reaching an altitude of 4,176 meters above sea level. The Center for Volcanology and Geological Hazard Mitigation (PVMBG) confirmed that the volcano's alert status remains at Level III (Alert).

One significant eruption was recorded at 04:59 AM Western Indonesian Time (WIB), producing a gray ash column of moderate to thick intensity that drifted northeast. Later in the day, another eruption occurred at 23:34 WIB, with a white to gray ash column of thick intensity observed moving north. These events are part of a frequent pattern of activity, with Mount Semeru having erupted 38 to 43 times in the week leading up to December 28, 2025. Throughout 2025, the volcano has been Indonesia's most active, recording over 3,130 eruptions.

Official Warnings and Exclusion Zones

In response to the ongoing volcanic activity, the PVMBG, through the MAGMA Indonesia application, has reiterated critical safety advisories for the public. Residents and visitors are strictly prohibited from engaging in any activities within the southeast sector along Besuk Kobokan, extending up to 13 kilometers from the eruption center at the peak. Beyond this 13-kilometer radius, a 500-meter exclusion zone is enforced along the riverbanks of Besuk Kobokan due to the persistent threat of hot clouds and lava flows, which can extend up to 17 kilometers from the summit.

Furthermore, authorities have established a 5-kilometer radius cordon around the crater, advising against any activities within this area due to the risk of ejected incandescent rocks. These measures are crucial for ensuring the safety of communities residing near the volcano, which is situated on the border between the Lumajang and Malang districts.

Seismic Activity and Monitoring

The eruptions on December 28 were accompanied by notable seismic activity. Seismographs recorded maximum amplitudes of 22 millimeters, with eruption durations ranging from 108 to 129 seconds. Throughout the day, monitoring stations observed numerous seismic events, including:

• Multiple eruption/explosion earthquakes
• Rockfall earthquakes
• Harmonic earthquakes

These seismic observations provide vital data for the PVMBG to continuously assess the volcano's behavior and potential hazards, allowing for timely updates and warnings to the public. Mount Semeru, rising 3,676 meters above sea level, is one of Indonesia's most active volcanoes and is part of the Pacific 'Ring of Fire,' a region known for its high seismic and volcanic activity.