Mount Semeru Erupts, Ash Plume Reaches 4,476 Meters Above Sea Level

Mount Semeru, the prominent stratovolcano in East Java, Indonesia, experienced a significant eruptive event on the morning of Tuesday, November 18, 2025. The volcano ejected a substantial column of volcanic ash that ascended approximately 800 meters above the crater rim, reaching an elevation of about 4,476 meters above sea level. This activity occurred while the Center for Volcanology and Geological Hazard Mitigation (PVMBG) maintained the volcano’s alert status at Level II, signifying moderate to high levels of unrest.

The PVMBG has issued specific safety directives following the eruption. Authorities strongly advise against any approach within an 8-kilometer radius to the southeast of the summit, which is identified as the primary eruption center along the Besuk Kobokan path. Furthermore, to mitigate the risk of pyroclastic flows and lahars, residents must maintain a minimum distance of 500 meters from the riverbanks along Besuk Kobokan, as these flows could potentially extend up to 13 kilometers from the peak.

Seismic monitoring data from the Mount Semeru Observation Post indicated that the November 18 event produced a maximum amplitude of 22 millimeters and lasted for 112 seconds, according to the officer on duty, Sigit Rian Alfian. This specific event is part of a broader pattern of heightened activity. Over the preceding 24-hour period ending November 18, 2025, MAGMA Indonesia recorded 146 eruption earthquakes, 40 avalanche earthquakes, and 30 exhalation earthquakes. This frequency distinguishes Semeru as the most active volcano in Indonesia for 2025, having recorded 2,801 eruptions up to that date.

Mount Semeru, which stands as the highest mountain on the island of Java with its Mahameru summit reaching 3,676 meters above sea level, has been in a state of near-constant eruption since 1967. This latest event is reported to be the seventh or eighth eruption within the preceding week. The ash plume observed on November 18 was described as dense, ranging from white to gray, and drifting in a southerly direction, consistent with the ongoing Level II alert status maintained by geological authorities.