Mount Semeru Remains on Alert Following Multiple Eruptions in East Java
Mount Semeru in East Java, Indonesia, continues to exhibit heightened volcanic activity, with multiple eruptions reported over the past several days. The volcano erupted seven times between dawn and morning on Wednesday, February 4, 2026, according to reports from the Semeru Volcano Observation Post (PGA) in Lumajang.
The eruptions began at 4:58 a.m. Western Indonesian Time (WIB) and continued until 8:02 a.m. WIB. The PGA reported that eruption columns reached heights of 300 to 800 meters above the summit. Ash plumes were observed as white to gray in color, ranging from thin to thick intensity, and drifted towards the northeast.
Seismographic recordings captured the eruptions, with a maximum amplitude of 22 mm and durations of up to 138 seconds. Between midnight and 6:00 a.m. WIB on February 4th, the seismic network detected 20 eruption earthquakes, with amplitudes ranging from 10-22 mm and durations of 72-152 seconds. One avalanche earthquake, with an amplitude of 5 mm and a duration of 76 seconds, was also recorded, along with seven gust earthquakes (amplitudes of 3-7 mm, durations of 40-101 seconds) and four distant tectonic earthquakes (amplitudes of 5-30 mm, S-P times of 13-41 seconds, durations of 33-147 seconds).
As of February 4, 2026, the Alert Level for Mount Semeru remained at 3, the second lowest level on a scale of 1-4. Edi Slameto, Acting Head of the Center for Volcanology, Mitigation, and Geological Hazard Mitigation (PVMBG) of the Geological Agency, stated that the activity level “remains at alert.”
Authorities are urging the public to stay at least 5 km away from the summit in all directions, 13 km from the summit on the southeast flank along the Kobokan drainage, and 500 meters from the banks of the Kobokan drainage as far as 17 km southeast of the summit. These recommendations are in place to mitigate risks associated with potential volcanic hazards.
Recent weekly reports, covering the period from January 29th to February 3rd, 2026, indicate that daily eruptive events have been consistently recorded by the seismic network. Daily ash plumes, either gray or white-to-gray, have risen as high as 1 kilometer above the summit, drifting in northerly, northeasterly, easterly, and southeasterly directions. Incandescent material has also been visible on the southeast flank, particularly during February 1st and 2nd, as observed through webcam views.
Mount Semeru is located in East Java, Indonesia, and contains the active Jonggring-Seloko vent at the Mahameru summit. The volcano has a history of frequent eruptions, characterized by small-to-moderate explosions from the summit crater, occasional lava flows, and larger explosive eruptions accompanied by pyroclastic flows that have reached the lower flanks of the volcano. The current eruption began in June 2017 and has since been characterized by intermittent gas-and-ash plumes and incandescent avalanches.
The climbing route to Mount Semeru remains completely closed due to fluctuating volcanic activity, a measure expected to remain in effect through early 2026. Management priorities are focused on ensuring the safety of climbers and the surrounding communities.
In December 2021, a major eruption of Mount Semeru caused significant devastation, destroying over 3,000 homes and displacing more than 10,500 people. Nearly 60 people were killed and over 2,000 injured. The eruption blocked roads with lava flows, ash, and fallen trees, and disrupted electricity, phone, and internet services in the affected areas.
