Indonesia's Mount Semeru Erupts Six Times in One Day: Pyroclastic Flows Race 4.5 Kilometers as Alert Stays at Level III
East Java, Indonesia — Mount Semeru, on the border of Lumajang and Malang regencies in East Java Province, erupted repeatedly from the early hours of November 5, erupting six times in a single day. Several pyroclastic flows raced down its southeastern slopes, the longest reaching 4.5 kilometers. As of the authorities' announcements, no casualties or property damage had been reported.
At 3,676 meters, Semeru is the highest peak on Java and one of Indonesia's most active volcanoes. According to a written report by Sigit Rian Alfian, an officer at the Mount Semeru observation post, an eruption at 6:33 a.m. local time sent an ash column about 700 meters above the summit (about 4,376 meters above sea level); seismographs recorded a maximum amplitude of 22 millimeters over about 3 minutes 44 seconds, and a pyroclastic flow traveled about 3 kilometers southeast toward the Besuk Kobokan river valley.
Eruptions had already occurred at 3:33 a.m. and 5:37 a.m., with further eruptions at 8:42 a.m. and 9:24 a.m. The 9:24 a.m. eruption produced another ash column of about 700 meters, gray to black and thick, with a maximum amplitude of 31 millimeters lasting about 7 minutes 27 seconds. Muhammad Amrul, head of the operations control center of the East Java disaster management agency, said three pyroclastic flows had been recorded by noon, traveling between 3 and 4.5 kilometers, and sand miners near the mountain fled to safety.
Indonesia's Center for Volcanology and Geological Hazard Mitigation (PVMBG) kept Semeru at Alert Level III (Siaga), the second-highest of four levels, urging residents of Lumajang and Malang to stay vigilant, keep away from the southeastern danger zone and from river valleys prone to lahars, and follow official information from PVMBG and local disaster agencies.
Semeru's activity had already intensified earlier this month: it erupted with a pyroclastic flow on the morning of November 4, and heavy rain on November 1-2 sent a cold lahar down the Glidik River that cut off 117 families in Lumajang, though no lives were lost. Authorities continue to monitor the volcano after the latest eruptions.
(Source: Indonesia's Center for Volcanology and Geological Hazard Mitigation (PVMBG))
Source: 印度尼西亚火山与地质灾害减灾中心
Published by GSM · USA (original Chinese edition)
Photo: 图：印度尼西亚东爪哇省塞梅鲁火山喷发（资料图，2025年11月19日喷发）。公共领域，经 Wikimedia Commons。 / Photo: Mount Semeru erupting in East Java, Indonesia (file photo, November 19, 2025 eruption). Public domain, via Wikimedia Commons.
