Semeru Spews 600-Meter Ash Columns in Triple Eruption, Authorities Issue Warnings

Lumajang: Mount Semeru, located on the border of Lumajang and Malang Regencies, East Java, erupted three times, with a plume reaching 600 meters above the summit on Wednesday morning, November 19, 2025. The first eruption occurred at 4:10 a.m. Western Indonesian Time (WIB), with an observed plume height of approximately 500 meters above the summit, or 4,176 meters above sea level (masl).

The ash column was observed to be white to gray in color and thick, heading southwest. The eruption was recorded on a seismograph with a maximum amplitude of 22 mm and a duration of 142 seconds, said Mukdas Sofian, an officer at the Mount Semeru Observation Post, in Lumajang on Wednesday, November 19, 2025, as reported by Antara.

The highest mountain on Java Island then erupted again at 5:09 a.m. Western Indonesian Time (WIB), with an observed plume height of approximately 600 meters above the summit. The ash column was observed to be white to gray in color, with a thick intensity toward the southeast.

"The eruption of Mount Semeru was recorded on a seismograph with a maximum amplitude of 22 mm and a duration of 150 seconds," he explained.

The third eruption occurred at 6:05 a.m. Western Indonesian Time, with an observed eruption column height of approximately 600 meters above the summit, or 4,276 meters above sea level (masl). The ash column was observed to be white to gray in color, with a thick intensity toward the southeast and south.

"The eruption was recorded on a seismograph with a maximum amplitude of 22 mm and a duration of 137 seconds," explained Mukdas.

He explained that Mount Semeru remains at Alert status, or Level II. The Center for Volcanology and Geological Hazard Mitigation (PVMBG) has issued several recommendations, including:

The public is prohibited from engaging in any activities in the southeast sector, along Besuk Kobokan, eight kilometers from the summit (the epicenter of the eruption).

The public is prohibited from engaging in activities within 500 meters of the riverbank along Besuk Kobokan, as this could potentially extend the hot plains and lava flows up to 13 kilometers from the summit.

Public is asked to be aware of the potential for pyroclastic flows, lava avalanches, and lahar rain along rivers and valleys that originate at the summit 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.

"We urge the public to avoid activities within a three-kilometer radius of the crater or summit of Mount Semeru, due to the risk of ejected incandescent rocks," said Mukdas.