The latest eruption occurred at 09:28 a.m. local time, sending ash columns 500 meters above the summit, or 4,176 meters above sea level, according to Mukdas Sofian from Semeru’s monitoring post.
The plume was white to gray with dense intensity, recorded on seismographs with a maximum amplitude of 22 mm and a duration of 145 seconds.
Earlier the same morning, at 05:01 a.m., Semeru also erupted, though it was not visually observed.
Seismic data showed a similar amplitude and lasted 140 seconds.
Semeru’s daily activity remains high, with 45 eruption quakes recorded on Wednesday, ranging from 10–22 mm in amplitude and lasting about 50–179 seconds.
The volcano is still on Alert Level II (Waspada). Indonesia’s Geological Agency has prohibited all activities within 8 km of the crater, particularly along the Besuk Kobokan river channel.
Residents outside that zone are advised to stay at least 500 meters from riverbanks due to the risk of pyroclastic flows and lahars, which may extend up to 13 km. People are also urged to avoid areas within 3 km of the summit because of the danger of flying lava bombs.
Communities near Semeru and its river valleys — Besuk Kobokan, Bang, Kembar, and Sat — have been told to stay alert for hot clouds, lava, and rain-triggered lahars.
With volcanic activity rising nationwide, the Geological Agency is also urging tourists and hikers to strictly follow safety rules around active volcanoes.
“People need to stay alert and respect the safety boundaries we’ve put in place,” said Hadi Wijaya, head of the Center for Volcanology and Geological Hazard Mitigation (PVMBG), in a statement issued in August.
During the dry season, good weather often attracts more climbers to Indonesia’s peaks. Out of the country’s 500 volcanoes, 127 are considered active.
Officials warned that ignoring restrictions can be fatal. In late 2023, 23 hikers were killed near Mount Marapi in West Sumatra after climbing without permission.
Similar violations occurred in 2024 at Mount Dukono in North Maluku, while in East Nusa Tenggara, rising crater lake temperatures at Mount Kelimutu in August also triggered concerns of sudden eruptions.
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Translator: Zumrotun S, Rahmad Nasution
Editor: M Razi Rahman
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