Mount Semeru Erupts Again, Ash Column Reaches 1 Kilometer Above Summit

LUMAJANG - Mount Semeru, located on the border of Lumajang and Malang Regencies, East Java, erupted again, with a plume reaching 1 kilometer above the summit on Thursday morning, November 6.

"Mount Semeru erupted on Thursday, November 6, 2025, at 6:07 a.m. Western Indonesian Time (WIB), with an observed eruption column height of approximately 1,000 meters above the summit, or 4,676 meters above sea level," said Mukdas Sofian, an officer at the Mount Semeru Observation Post, in a written report received in Lumajang on Thursday, November 6.

He noted that the ash column was observed to be white to gray in color, with a thick intensity to the north and northeast. The eruption was recorded on a seismograph with a maximum amplitude of 22 mm and a duration of 157 seconds.

According to official data, the highest mountain on Java Island recorded 2,766 eruptions between January and November 6, 2025, at 7:00 a.m. Western Indonesian Time.

Mount Semeru's seismic activity is still dominated by daily eruptions, but these eruptions have not significantly impacted the activities of residents living near the slopes of the 3,676-meter-high mountain.

Mukdas explained that Mount Semeru remains at Alert Status (Level II), so the Center for Volcanology and Geological Hazard Mitigation (PVMBG) has issued several recommendations: prohibiting the public from engaging in any activity in the southeastern sector, along Besuk Kobokan, within eight kilometers of the summit (the eruption epicenter).

Beyond this distance, he said, the public should not engage in any activity within 500 meters of the riverbank along Besuk Kobokan, due to the potential for spreading pyroclastic flows and lava flows up to 13 kilometers from the summit.

"The public is also advised to avoid activities within a three-kilometer radius of the crater or peak of Mount Semeru, due to the risk of ejected incandescent rocks," he said.

He urged the public to be aware of the potential for hot clouds, lava flows, and lahars along rivers and valleys that originate at the peak of Mount Semeru, especially along Besuk Kobokan, Besuk Bang, Besuk Kembar, and Besuk Sat, as well as the potential for lahars in small rivers that are tributaries of Besuk Kobokan.