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Semeru Erupts Again Early Sunday, 29 Eruption Quakes Recorded Overnight

Stateline MEDIA Newsroom•October 18, 2026•3 min read

Mount Semeru erupted again on Sunday (18/10/2026) at 00:39 local time, with 29 eruption quakes recorded in one overnight observation period. Its activity status remains at Level III (Alert).

Key Facts

Mount Semeru on the border of Lumajang and Malang regencies, East Java, erupted again on Sunday (18/10/2026) at 00:39 local time; the eruption was still ongoing when the activity report was published, with the ash column not visually observed.
Seismograph monitoring for the 18:00–23:59 observation period recorded 29 eruption quakes (amplitude 12–25 mm, duration 0.6–160 seconds), 3 rockfall quakes (2–5 mm, 59–86 seconds), and 3 gas-emission quakes (5–9 mm, 38–50 seconds).
Semeru's volcanic activity status remains at Level III (Alert), according to the report published on October 18, 2026.
On Saturday (17/10/2026), Semeru monitoring post officer Liswanto reported incandescent lava avalanches reaching 1.5 kilometers to the southeast toward Besuk Kobokan, accompanied by eruptions with ash columns of around 400–600 meters above the summit.
Cumulative data reported on October 18, 2026, records Semeru with 2,009 eruptions so far in 2026, the most among Indonesian volcanoes.
The volcanology agency prohibits activity within a 5-km radius of the crater and in the southeastern sector along Besuk Kobokan up to 13 km from the summit; residents are also told to stay 500 meters away from riverbanks, as pyroclastic flows and lahars could reach up to 17 km.

Eruption Recorded at 00:39, Status Remains at Level III Alert

Mount Semeru on the border of Lumajang and Malang regencies, East Java, erupted again on Sunday (18/10/2026) at 00:39 local time. When the activity report was published, the eruption was still ongoing, while the height of the ash column was not visually observed.

The volcanic activity of Java's highest mountain remains at Level III (Alert). Instrumental monitoring continues to record seismic activity as part of volcano surveillance.

29 Eruption Quakes Recorded in a Single Observation Period

Seismographs for the 18:00–23:59 observation period recorded 29 eruption quakes with amplitudes of 12–25 millimeters and durations of 0.6–160 seconds. Three rockfall quakes (2–5 mm amplitude, 59–86 seconds) and three gas-emission quakes (5–9 mm, 38–50 seconds) were also logged.

Those figures cover a single observation period, not a full day. Cumulative data reported on October 18, 2026, records Semeru with 2,009 eruptions so far this year, the most among Indonesian volcanoes.

The previous day, Saturday (17/10/2026), Semeru monitoring post officer Liswanto reported incandescent lava avalanches traveling 1.5 kilometers southeast toward Besuk Kobokan, accompanied by ash columns of around 400–600 meters above the summit drifting eastward.

Danger Zones: Besuk Kobokan up to 13 Km from the Summit

The volcanology agency bars all activity within a 5-kilometer radius of the crater due to the risk of incandescent rock projectiles. The danger zone also covers the southeastern sector along the Besuk Kobokan drainage up to 13 kilometers from the summit or eruption center.

Beyond that limit, residents are asked to stay at least 500 meters from riverbanks along Besuk Kobokan, which could be affected by expanding pyroclastic flows and lahars reaching up to 17 kilometers from the summit.

Rivers to watch include Besuk Kobokan, Besuk Bang, Besuk Kembar, and Besuk Sat. Communities on Semeru's slopes are urged to follow official information via MAGMA Indonesia and Lumajang regency disaster agency instructions should evacuation be required.