Volcanic activity at Mount Semeru in Lumajang Regency, East Java, showed a significant increase again on Thursday (2/7/2026). According to data from the Mount Semeru Monitoring Post, the highest mountain on Java Island was observed sending pyroclastic flows up to 4 kilometers to the southeast.
The event was intensively recorded during the observation period from 12:00 to 18:00 local time. In addition to pyroclastic flows, an eruption column of white ash reaching 1.5 kilometers above the crater peak was observed at 16:37. According to seismogram records, the pyroclastic flow had an amplitude of 22 millimeters with a duration of up to 400 seconds.
Mount Semeru Monitoring Post officer, Liswanto, emphasized that the mountain's status remains at Level III (Alert). Relevant authorities have issued a strong warning for the public not to conduct any activities in the southeastern sector, particularly along the Besuk Kobokan riverbed within a 13-kilometer radius from the eruption center.
In addition to restrictions in the southeastern sector, residents are also asked to maintain a safe distance of 500 meters from the riverbanks along Besuk Kobokan. This is due to the potential expansion of pyroclastic flows and the threat of cold lava flows (lahars) that could reach up to 17 kilometers from the peak.
The public is also advised not to engage in activities within a 5-kilometer radius from the crater peak to anticipate the danger of incandescent rock ejecta. Residents around valleys originating at the peak of Semeru, such as Besuk Bang, Besuk Kembar, and Besuk Sat, are asked to remain vigilant against potential follow-up hazards.
