The eruption of the highest volcano on the island of Java occurred at 17:30 WIB (Western Indonesian Time). The observed ash column was white to gray with moderate intensity leaning towards the north. This eruption was recorded on a seismogram with a maximum amplitude of 22 mm and a duration of approximately 2 minutes 16 seconds.
One hour later, at 18:29, the volcano with a height of 3,676 meters above sea level erupted again with an observed ash column height of approximately 900 meters above the peak (approximately 4576 meters above sea level). The observed ash column was white to gray with thick intensity towards the south and southwest. This eruption was recorded on a seismograph with a maximum amplitude of 23 mm and a duration of 163 seconds.
These two eruption events were reported alternately by the Semeru Volcano Observation Post (PGA) officers, Liswanto and Sigit Rian Alfian. "The activity level of Mount Semeru volcano remains at level II (Alert)," said Liswanto and Rian in their report on Wednesday night, February 26, 2025.
The results of seismological observations in the last 24 hours until early Wednesday morning mentioned several recorded earthquakes, namely 60 times of eruption or explosion earthquakes with amplitudes of 10-23 mm and earthquake durations of 57-191 seconds. The seismogram also recorded 2 times of Avalanche earthquakes with amplitudes of 4-6 mm and earthquake durations of 45-50 seconds.
In addition, there were also 9 times of emission earthquakes with amplitudes of 3-8 mm, earthquake durations of 43-76 seconds. Then 1 time of harmonic earthquake with an amplitude of 3 mm, and an earthquake duration of 212 seconds.
The PGA station located on Mount Sawur, Sumber Wuluh Village, Candipuro Subdistrict, Lumajang also recorded 2 times of Distant Tectonic earthquakes with amplitudes of 8-23 mm, S-P 16-74 seconds, and earthquake durations of 48-120 seconds.
At this level II activity level or Alert, residents are recommended not to carry out any activities in the southeastern sector along Besuk Kobokan, within a distance of 8 km from the peak (eruption center).
Outside this distance, the community is advised not to carry out activities within 500 meters from the river edge (river borders) along Besuk Kobokan because of the potential for being affected by the expansion of hot clouds and lava flows up to a distance of 13 km from the peak.
The Center for Volcanology Mitigation and Geological Disaster also recommends residents not to engage in activities within a 3 km radius from the crater or peak of Mount Semeru due to the danger of rock projectiles (pyroclastic flows).
People are also advised to be cautious of the potential for pyroclastic flows and lava flows along the river/valley originating from the peak of Mount Semeru, especially along Besuk Kobokan, Besuk Bang, Besuk Kembar, and Besuk Sat, as well as the potential for lahar in small rivers that are tributaries of Besuk Kobokan.
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