Mount Semeru is a volcano located in East Java, Indonesia. It has an elevation of about 3,676 meters (12,060 ft) and the peak of the volcano is known as Mahameru and is part of the Bromo-Tengger-Semeru National Park. Geologically, it lies in the Sunda Arc which is a part of the Pacific “Ring of Fire.” There are many recorded eruptions of this mountain throughout history such as the first recorded event in 1818, significant activity in 1941-1942, and the volcano has been in almost continuous eruption with ash emissions and pyroclastic flows since 1967. 

On November 19, 2025 Mount Semeru produced a major eruption with pyroclastic flows traveling up to 10km and ash columns that reach 16.5 km (54,000 ft). 170 climbers had to be rescued after being stranded at Ranu Kumbolo camping area and many local villages had to be evacuated. At least 950,000 people live in the region, with 50,000 directly exposed to volcanic hazards on the east, south, and southeast slopes. This eruption will cause significant damages throughout these villages and also cause disruptions in tourism and aviation in the region.

Pyroclastic Flow: a fast moving, high-density avalanche of volcanic ash, pumice, lava blocks, and hot gas that explodes from a volcano. 

Sources:

“Semeru Volcano, East Java, Indonesia: New Radar Acquisition Detected Significant Ash Deposits.” Volcano Discovery, 23 Nov. 2025, www.volcanodiscovery.com/semeru/news/287760/Semeru-volcano-East-Java-Indonesia-new-radar-acquisition-detected-significant-ash-deposits.html.

Accessed 26 Nov. 2025.

“Semeru Volcano, Indonesia Activity Update Nov 24, 2025: Continuing Eruption.” Volcano Discovery, 24 Nov. 2025, www.volcanodiscovery.com/semeru/news/287778/Semeru-Volcano-Indonesia-activity-update-Nov-24-2025-Continuing-eruption.html. Accessed 26 Nov. 2025.

“The Long History of Mount Semeru Eruption.” Nusantara Pol, 6 Dec. 2021, www.nusantarapol.com/2021/12/the-long-history-of-mount-semeru-eruption.html?m=1. Accessed 26 Nov. 2025.

“Volcano Eruption Forces Rescue of 170 Climbers on Indonesia’s Mount Semeru.” ABC News, 19 Nov. 2025, abcnews.go.com/International/wireStory/volcano-eruption-forces-rescue-170-climbers-indonesias-mount-127700649.Accessed 26 Nov. 2025.

“Climbers Rescued, Locals Evacuated after Mount Semeru Eruption.” ABC News (Australia), 21 Nov. 2025, www.abc.net.au/news/2025-11-21/climbers-rescued-locals-evacuated-after-mount-semeru-eruption/106035320. Accessed 26 Nov. 2025.