Mount Semeru, located in East Java, was observed erupting again on Monday (6/7/2026) morning. The eruption, which occurred precisely at 08:13 WIB, produced a column of volcanic ash reaching a height of 1,000 meters above the peak, or approximately 4,676 meters above sea level.
According to reports from the Volcano Observation Post officer, Sigit Rian Alfian, the observed ash column was thick with color variations ranging from white to gray, moving east and northeast. This volcanic activity was clearly recorded on a seismograph with a maximum amplitude of 22 millimeters and a duration of 134 seconds.
The relevant authorities have issued a strong warning advising the public not to conduct any activities in the southeastern sector along Besuk Kobokan within a 13-kilometer radius from the eruption center. A similar prohibition applies to areas beyond that distance, specifically a 500-meter radius from the riverbanks along Besuk Kobokan, due to the risk of pyroclastic flows and lahar flows that could extend up to 17 kilometers.
In addition, residents are requested to stay away from the area within a 5-kilometer radius of the crater peak to avoid the danger of ejecting incandescent rocks. The public is urged to remain vigilant against the threat of lava flows and cold lahar floods that could potentially occur along the river channels originating at the peak of Semeru, such as Besuk Bang, Besuk Kembar, Besuk Sat, and several other tributaries.
