Mount Semeru, located in East Java, showed significant volcanic activity again on Saturday (4/7/2026) morning. The eruption, which occurred at precisely 06:08 WIB, spewed a volcanic ash column reaching a height of 1,400 meters above the crater peak. Based on observations by the Center for Volcanology and Geological Hazard Mitigation (PVMBG), the white to gray ash column of moderate intensity was seen moving south.
Seismogram data recorded that this eruption had a maximum amplitude of 22 millimeters with a duration of approximately 2 minutes and 17 seconds. As of the time of writing, volcanic activity at the peak of Java's highest mountain continues to be monitored as ongoing.
Currently, Mount Semeru remains at Level III (Alert) status. PVMBG issued a strict warning urging the public not to conduct any activities in the southeastern sector along Besuk Kobokan, specifically within a 13-kilometer radius from the eruption center. This restriction includes a ban on activities within a 500-meter radius of the riverbank along Besuk Kobokan due to the threat of expanding pyroclastic flows and lahar flows that could reach up to 17 kilometers.
In addition to the threat of pyroclastic flows, the public is also advised to stay clear of a 5-kilometer radius from the main crater to avoid the risk of hazardous incandescent rock ejecta. Residents and tourists are urged to remain vigilant for potential pyroclastic density currents, lava avalanches, and lahars along river basins originating from Semeru's peak, particularly along the Besuk Kobokan, Besuk Bang, Besuk Kembar, and Besuk Sat rivers.
