Mount Semeru, the highest peak on Java Island, was reported to show volcanic activity again on Monday (6/7/2026). The eruption spewed a volcanic ash column up to 1,000 meters above the peak, or around 4,676 meters above sea level.
According to an official report from volcano observation post officer Sigit Rian Alfian via the Magma ESDM website, the observed ash column was thick and predominantly white to gray in color. The volcanic material spread toward the northeast and east. The eruption was recorded with a maximum amplitude of 22 mm and lasted for 134 seconds.
In response to these conditions, authorities issued a stern warning to the public not to conduct any activities in the southeastern sector along Besuk Kobokan, within a 13-kilometer radius of the eruption center. In addition, residents are prohibited from approaching within 500 meters of the riverbanks along that flow, given the threat of expanding pyroclastic flows and lahar flows that could reach up to 17 kilometers.
The public is also asked to remain vigilant and stay clear of the area within a 5-kilometer radius of Mount Semeru's main crater. This restriction is enforced to avoid the risk of incandescent rock ejection, which could occur at any time due to the volcano's unstable activity.
