“The eruption occurred Thursday (Jan. 8) at 07:14 a.m. local time, with the ash column reaching roughly 700 meters above the 4,376-meter summit,” said Semeru observation post officer Sigit Rian Alfian.
He added that the ash plume appeared white to gray and was thickest toward the northwest. The eruption registered on seismographs with a maximum amplitude of 14 mm and lasted about 120 seconds.
Semeru recorded four eruptions on Thursday, starting at 00:33 a.m. local time.
The first ash column reached 700 meters, followed by 600 meters at 05:19 a.m.
Subsequent eruptions occurred at 05:25 a.m. and 07:14 a.m., both reaching approximately 700 meters above the summit.
The volcano remains at Level III (Alert) activity. The Center for Volcanology and Geological Disaster Mitigation (PVMBG) issued safety recommendations for residents.
People are prohibited from entering the southeast sector along Besuk Kobokan within 13 km of the summit.
Outside that zone, residents must stay at least 500 meters from riverbanks along Besuk Kobokan due to potential pyroclastic flows and lahars, which can extend up to 17 km from the summit.
Activity is also banned within a 5-km radius of the crater due to the risk of volcanic rock ejections.
Authorities warned residents to remain alert for pyroclastic flows, lava collapses, and lahars along rivers originating from the summit, including Besuk Kobokan, Besuk Bang, Besuk Kembar, Besuk Sat, and smaller tributaries.
Mount Semeru has a history of repeated eruptions. On Thursday night, Jan. 1, 2026, an eruption at 18:37 local time sent an ash column approximately 900 meters above the summit, or 4,576 meters above sea level.
The ash appeared white to gray, thickest toward the northeast and east, and registered 23 mm on seismographs, lasting 153 seconds. Data show that Semeru erupted four times at the start of 2026, including an eruption at 01:26 a.m., when the ash column reached roughly 1,000 meters above the summit.
Related news: Mount Semeru erupts six times, ash columns reach 900 meters
Related news: BNPB suggests centralized Semeru evacuation centers modeled on Merapi
Translator: Zumrotun S, Rahmad Nasution
Editor: M Razi Rahman
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