Volcanic activity at Mount Semeru in East Java was observed to increase significantly on Tuesday (6/9/2026). The Mount Semeru Observation Post recorded that the highest volcano on Java Island experienced ten eruptions between morning and afternoon.
The first eruption was detected at 04:43 WIB and continued to fluctuate until 12:47 WIB. Mount Semeru Observation Post officer Liswanto confirmed that the eruption with the highest ash column reached 1.2 kilometers above the peak, or 4,876 meters above sea level (masl), occurring precisely at 12:09 WIB. The observed ash column ranged from white to gray with moderate intensity, drifting toward the northeast.
To date, the status of Mount Semeru remains at Level III (Alert). The public is urged to remain calm while increasing vigilance and strictly complying with all safety recommendations issued by relevant authorities.
Observers emphasized a prohibition on activities in the southeastern sector along Besuk Kobokan up to a distance of 13 kilometers from the eruption center. In addition, residents are forbidden from conducting activities within a 500-meter radius of the riverbanks along Besuk Kobokan to anticipate the risk of expanding pyroclastic flows and lahar flows.
The potential threat of incandescent rock falls also restricts activities within a five-kilometer radius from the crater. Residents are advised to be aware of potential lava and lahar flows along river channels and valleys originating at the peak, such as Besuk Bang, Besuk Kembar, and Besuk Sat.
