"An eruption occurred at 2:02 a.m. with an ash column reaching approximately 1,000 meters above the summit," observation post officer Yadi Yuliandi said in a written report.
He said the thick gray ash column drifted westward. The eruption was recorded on a seismogram with a maximum amplitude of 22 mm and lasted about 3 minutes and 29 seconds.
"The eruption was accompanied by a pyroclastic flow reaching 3.5 kilometers from the summit," he said.
The 3,676-meter-high volcano erupted again at 6:55 a.m., producing an ash column about 800 meters high.
The ash appeared white to gray and drifted southwest and west, with a recorded duration of 134 seconds.
Seven minutes later, another eruption sent ash up to 600 meters above the summit.
A fourth eruption occurred at 7:53 a.m. with an ash column reaching 800 meters, while observations at 8:50 a.m. were obscured by fog.
Yuliandi said Mount Semeru remains at Level III (Standby).
Authorities advise the public to avoid activities in the southeastern sector along Besuk Kobokan within 13 kilometers of the summit.
Beyond that, residents should stay at least 500 meters away from riverbanks along Besuk Kobokan due to the risk of expanding pyroclastic flows and lava reaching up to 17 kilometers.
The public is also urged to avoid a 5-kilometer radius from the crater due to the risk of ejected incandescent rocks.
He also warned of potential pyroclastic flows, lava avalanches, and lahars along rivers originating from the summit, including Besuk Bang, Besuk Kembar, and Besuk Sat.
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Translator: Arie Novarina
Editor: Anton Santoso
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