RRI.CO.ID, Lumajang - Mount Semeru, the highest volcanic peak on Java Island, registered a dramatic escalation in eruptive activity on Monday afternoon, June 29, 2026, spewing a dense cloud of volcanic ash 1.2 kilometers into the atmosphere accompanied by distinctly audible shockwaves.

The violent afternoon explosion forms part of a sustained volcanic surge, with state vulcanologists logging at least nine separate eruptions within a single 24-hour cycle. The continuous seismic unrest has prompted emergency officials to maintain a high-level security perimeter around the active crater to protect agricultural communities on the mountain's slopes.

The primary afternoon blast occurred precisely at 4.39 p.m. local time, according to a dispatch from the volcano's monitoring outpost in Lumajang, East Java.

"Semeru Volcano erupted at 16:39 local time with an observed eruption column height of around 1.2 km above the peak or 4,876 meters above sea level (masl)," reported a field officer with the Volcanology and Geological Disaster Mitigation Center (PVMBG) Sigit Rian Alfian, as quoted by Antara.

Sigit noted that the thick ash plume, shifting between shades of stark white and dark grey, drifted heavily toward the east and northeast corridors. The event registered an amplitude of 22 mm on seismographs and lasted for approximately 2 minutes and 9 seconds.

"The eruption of the highest mountain on Java Island was accompanied by a moderate explosion and currently Semeru Volcano is at Level III (Alert) status," he added.

Throughout Monday, the 3,676-meter volcano ruptured repeatedly between 12.04 a.m. and 7.23 p.m. local time, throwing ejecta at varying heights ranging from 500 to 1,200 meters above its peak.

Despite the booming detonations echoing across the Lumajang and Malang border regencies, disaster management authorities confirmed that no immediate civilian casualties or volcanic ash fallouts have impacted residential zones.

"So far, there has been no direct impact on the community, but BPBD officers are always on standby at the Curahkobokan Post and the Oro-oro Ombo Post to continue monitoring the development of Semeru Volcano's activity," said Chief Executive of the Lumajang Regional Disaster Mitigation Agency (BPBD), Isnugroho.

With Semeru Volcano firmly locked at Level III (Alert) status, Isnugroho reminded the public that the southeastern sector along the Besuk Kobokan river channel remains completely off-limits to a distance of 13 kilometers from the eruption center.

Outside of that immediate zone, civilians are strictly barred from working or traveling within 500 meters of the riverbanks up to 17 kilometers from the summit due to the high risk of sudden pyroclastic density currents (awan panas) and secondary mudflows (lahar).

"People are prohibited from carrying out activities within a five-kilometer radius of the crater/peak of Semeru Volcano, due to the risk of being ejected (incandescent) rocks," Isnugroho warned, emphasizing that incandescent ballistic rocks present an immediate threat to life.

The BPBD has urged surrounding populations to maintain extreme vigilance along all primary river systems feeding off the summit, including the Besuk Kobokan, Besuk Bang, Besuk Kembar, and Besuk Sat channels, as heavy highland rains could instantly transform volcanic debris into destructive lahars. ***