Geological Agency Warns of Repeated Hot Clouds at Mount Semeru

February 15, 2026 | 09:17 am

TEMPO.CO, Jakarta - The Indonesian Geological Agency assesses that Mount Semeru's volcanic activity remains high. Repeated pyroclastic avalanches, primarily directed toward the southeast sector with a sliding distance of up to 4,000 meters from the summit toward Besuk Kobokan, indicate the high activity of this volcano, which is geographically located in Lumajang and Malang Regencies, East Java.

Acting Head of the Geological Agency, Lana Saria, stated that Mount Semeru's activity level remains at Level III (Alert). Based on visual and instrumental monitoring, on Saturday, February 14, 2026, two pyroclastic avalanches were observed with a sliding distance of up to 6,000 meters from the summit toward the southeast.

According to Geological Agency data for the period February 1–13, 2026, pyroclastic avalanches were also observed several times with a sliding distance of up to 2,500–4,000 meters, accompanied by material avalanches. Seismic activity is dominated by eruption earthquakes, collapse earthquakes, gust earthquakes, and harmonic tremors.

"The recorded earthquakes indicate that there is still supply from beneath the surface of Mount Semeru, along with the release of material to the surface through eruptions and plumes," said Lana Saria in a written statement received by Tempo on Saturday evening.

The seismic velocity variation parameters, Lana Saria said, fluctuate but still show a decreasing pattern since mid-October 2025. "This indicates that the volcanic system is in a relaxation phase and is not experiencing high pressure (pressurization), but is still very vulnerable to increased pressure," she added.

According to Lana, monitoring data from the Argosuko Tiltmeter Station on the radial component indicates rapid acceleration/change. "This is interpreted as a local mechanical response in the shallow system (e.g., adjustment of stress and load on the near-surface/shallow body), not as a deformation response controlled by strong magmatic inflation," she said.

Based on the analysis and evaluation results, Mount Semeru's activity level remains at Level III (Alert). Several key recommendations include prohibiting the public, visitors, and climbers from engaging in activities within a 5-kilometer radius of the Jonggring Seloko Crater and refraining from entering the southeastern sector, extending 13 kilometers from the summit to the southeast, which could extend up to 17 kilometers along the Besuk Kobokan flow.

The public is advised to be aware of the potential for pyroclastic flows and lava flows along rivers and valleys originating at the summit of Mount Semeru, particularly 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.

Read: Mount Semeru Erupts Twice After Midnight, Alert Status Maintained

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