Mount Semeru Erupts Again, Ash Column Reaches 1.3 Kilometers
TEMPO.CO, Jakarta - Mount Semeru, located on the border of Lumajang and Malang Regencies in East Java, Indonesia, erupted again on Sunday morning, September 27, 2026, sending an eruption column reaching 1,300 meters above the Mahameru peak.
"An eruption of Mount Semeru occurred at 05:55 WIB (Western Indonesian Time), with the observed ash column reaching approximately 1,300 meters above the peak, or 4,976 meters above sea level," stated Liswanto, an officer at the Mount Semeru Observation Post, in a written report received in Lumajang.
The ash column appeared white to gray with moderate intensity and was drifting toward the northeast. The eruption was recorded on the seismograph with a maximum amplitude of 22 mm and an initial duration of approximately 2 minutes and 20 seconds.
"The eruption was still ongoing at the time the report was being prepared," he said.
According to official records, Mount Semeru erupted four times on Sunday between 00:21 WIB and 06:22 WIB, with observed eruption heights ranging from 500 meters to 1.3 kilometers above the peak.
Liswanto explained that Mount Semeru is currently at Alert Level III (Siaga). The recommendation is that the public must not conduct any activities in the southeastern sector along the Besuk Kobokan river, within a 13-kilometer radius of the peak (the eruption center).
"Beyond that distance, the public should not carry out activities within 500 meters of the riverbanks along Besuk Kobokan, due to the potential risk of expanding hot cloud surges and lahar (volcanic mudflows) reaching up to 17 kilometers from the peak," he stated.
He also urged the public to avoid activities within a 5-kilometer radius of the Mount Semeru crater or peak, as the area is prone to the danger of ejected incandescent rocks.
The public is also advised to remain vigilant regarding the potential for hot cloud surges, lava avalanches, and lahar flows along the river channels and valleys originating from the peak of Mount Semeru. "Especially along Besuk Kobokan, Besuk Bang, Besuk Kembar, and Besuk Sat, as well as the potential for lahar flows in the small rivers that are tributaries of Besuk Kobokan," he said.
