[REVISION HISTORY]

Indonesia volcanic activity late July 2026

Updated 1 time since CLSTR started tracking revisions of this situation.

What changed

2026-07-26 09:33 UTC → 2026-08-18 16:44 UTC · added ~~removed~~

Indonesia’s principal volcanoes remained unsettled through late July 2026. After the July 18 eruptions of Gunung Semeru that sent a ~~1‑km~~ 1-km ash column skyward and prompted a Level III alert with a ~~5‑km~~ 5-km summit exclusion and a ~~13‑km river‑valley~~ 13-km river-valley restriction, the agency kept the same safety measures in place. The same day, the ~~Lewotobi‑Laki‑Laki~~ Lewotobi-Laki-Laki plume prompted a Level II warning for nearby communities. On July 21, Gunung Sorikmarapi experienced a surge of 40 deep volcanic earthquakes and several tectonic events, leading authorities to maintain a Level II alert and a ~~1.5‑km~~ 1.5-km crater exclusion zone. Semeru erupted twice on July 23 (00:29 and 05:48 WIB). No visible plume was recorded, but monitoring stations logged 19 eruption tremors ~~(13‑22~~ (13-22 mm) plus numerous embusan, harmonic, tectonic and ~~rock‑fall~~ rock-fall tremors. The Level III alert and exclusion zones (5 km radius, 13 km along river valleys) remained unchanged. Mount Lewotobi ~~Laki‑laki~~ Laki-laki showed renewed activity on July ~~25‑26,~~ 25-26, erupting three times on the 25th and four more on the 26th. Ash plumes reached up to 800 m, and seismic amplitudes varied from 5.1 to 29.6 mm. Residents were advised to stay at least 5 km from the summit as ash drifted ~~west‑~~ west- and southwest. National geological agencies continue to monitor all sites closely, maintaining current alert levels and exclusion zones while assessing further eruption risk for surrounding communities.

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