Lumajang, East Java. Mount Semeru erupted three times on Monday morning, sending volcanic ash as high as 1,000 meters above its summit, according to an observation post monitoring Indonesia’s tallest volcano.

The first eruption occurred at 4:20 a.m. Western Indonesia Time, producing an ash column about 500 meters above the summit, or 4,176 meters above sea level.

“The ash column was observed to be white and gray with thick intensity, moving northwest. The eruption was recorded on a seismograph with a maximum amplitude of 21 millimeters and a duration of 128 seconds,” Mount Semeru Observation Post officer Sigit Rian Alfian said in a report.

Semeru, located on the border between Lumajang and Malang regencies in East Java, erupted again at 5:53 a.m., sending an ash column about 800 meters above the summit.

The thick gray ash plume moved north and northwest. The eruption was recorded with a maximum amplitude of 23 millimeters and lasted 133 seconds.

The third eruption occurred at 6:28 a.m., producing the highest ash column of the morning at about 1,000 meters above the summit.

“The ash column was observed to be gray with thick intensity, moving east. The eruption was recorded on a seismograph with a maximum amplitude of 23 millimeters and a duration of 140 seconds,” Sigit said.

Semeru Remains at Level III Alert
Sigit said Mount Semeru remains at Level III, or Siaga, the second-highest level in Indonesia’s four-tier volcano alert system.

Authorities have prohibited all activity in the southeastern sector along the Besuk Kobokan River within 13 kilometers of the summit, the center of the eruptions.

Beyond that distance, people are also prohibited from conducting activities within 500 meters of the riverbanks along Besuk Kobokan because pyroclastic flows and lahars could extend as far as 17 kilometers from the summit.

People are also prohibited from entering an area within a 5-kilometer radius of Semeru’s summit because of the risk of ejected incandescent rocks.

Sigit urged residents to remain alert to the potential for pyroclastic flows, lava avalanches and lahars along rivers and valleys originating on Mount Semeru.

The warning particularly applies to the Besuk Kobokan, Besuk Bang, Besuk Kembar and Besuk Sat waterways, as well as smaller rivers that are tributaries of Besuk Kobokan.

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