Mount Semeru, which stands tall on the border of Lumajang and Malang regencies, East Java, has once again shown a significant increase in volcanic activity. On Sunday (28/6/2026), the highest mountain on the island of Java was recorded to have erupted four times within a single day.
Mount Semeru Observation Post officer, Mukdas Sofian, reported that the largest eruption occurred at 11:37 WIB. The volcanic ash column was observed rising up to 1,000 meters above the peak, or equivalent to 4,676 meters above sea level. The ejected ash material was observed to be white to gray with a thick intensity, moving towards the southeast and south.
Based on seismograph data, the eruption was recorded with a maximum amplitude of 22 mm and a vibration duration of 170 seconds. Prior to this midday eruption, volcanic activity was also recorded at 05:35 WIB, 06:32 WIB, and 09:11 WIB with varying eruption characteristics.
Currently, volcanology authorities have set the status of Mount Semeru at Level III or Alert (Siaga). The public is urged not to conduct any activities within a five-kilometer radius of the crater or peak, considering the risk of incandescent rock ejection which poses a hazard to residents' safety.
Furthermore, the public is also asked to avoid the southeastern sector along Besuk Kobokan up to 13 kilometers from the eruption center. This warning includes riverbank areas up to 500 meters, given the potential threat of expanding hot clouds and lahar flows that could reach a distance of up to 17 kilometers from the peak.
Residents living around river valleys originating from Mount Semeru, especially along the flows of Besuk Kobokan, Besuk Bang, Besuk Kembar, and Besuk Sat, are asked to increase extra vigilance against the potential for lava avalanches and cold lahar flows during this eruption period.
