Evacuations ordered after powerful eruption at Semeru volcano sends ash to 17.9 km (59 000 feet), Indonesia
Indonesia’s Geological Agency raised the alert level for Semeru volcano to the highest (Level IV) following a major eruption on November 19, 2025, that produced an ash column up to 17.9 km (59 000 feet) above sea level. Authorities ordered evacuations of at least 300 residents from nearby villages and expanded exclusion zones up to 8 km (5 miles) from the crater and along the Besuk Kobokan valley.
A major eruption occurred at Semeru volcano, East Java, Indonesia, on November 19, producing a large pyroclastic flow and an ash column reaching approximately 17.9 km (59 000 feet) above sea level (a.s.l.), according to the Darwin Volcanic Ash Advisory Centre (VAAC) and Japan Meteorological Agency’s (JMA) Himawari-8 satellite data. The Aviation Color Code was raised to Red during the eruption.
Infrared imagery showed a rapidly intensifying column between 08:00 and 09:20 UTC (15:00–16:20 WIB), dispersing primarily toward the north and northwest, but continuous emissions were detected throughout the afternoon.
Ground observations confirmed the generation of extensive pyroclastic density currents (PDCs) moving through the southeastern flanks. The largest flows followed the Besuk Kobokan drainage, reaching distances of up to 15 km (9.3 miles) from the summit.
Local monitoring networks and community recordings documented multiple PDC pulses starting around 14:30 WIB (07:30 UTC). The flows caused dense, low-lying ash conditions throughout the Kobokan valley system.
Following the eruption, Indonesia’s Geological Agency, Ministry of Energy and Mineral Resources, raised the alert level of Mount Semeru from Level III to Level IV — the highest on the national scale.
“The public is advised not to engage in activities within an 8 km (5 miles) radius of the crater or peak of Mount Semeru due to the risk of being struck by ejected rocks,” said Muhammad Wafid, head of the agency.
The National Disaster Management Agency (BNPB) reported that at least 300 residents from nearby settlements were evacuated to two temporary shelters.
Spokesman Abdul Muhari stated that there were no immediate reports of casualties.
Exclusion zones were expanded to 8 km (5 miles) from the summit and along Besuk Kobokan, with an additional 2.5 km (1.5 miles) summit exclusion radius remaining in effect due to ballistic hazards. Authorities also warned residents to avoid riverbanks beyond the restricted area because of the potential for lahar flows.
At 05:20 UTC on November 20, Darwin VAAC reported that high-altitude ash had largely dissipated, while continuous emissions persisted to 4.6 km (15 000 feet) a.s.l., drifting southeast. The previous VAAC advisory issued at 23:30 UTC on November 19 noted detached volcanic ash to 17.9 km (59 000 feet) a.s.l. moving southwest and expected to dissipate within 12 hours.
Eruptive activity remained elevated into the morning of November 20, with low-level ash plumes confined near the summit and elevated seismic and thermal signals continuing.
Semeru’s last major eruption in December 2021 caused extensive destruction, killing more than 50 people and damaging over 5 000 homes across East Java.
Featured image: Pyroclastic flow produced during major eruption at Semeru volcano on November 19, 2025. Credit: afarTV
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