Semeru eruption LUMAJANG, Indonesia — Indonesia’s highest volcano on Java island belched towering clouds of ash and hot clouds down its slopes as molten rocks shot high into the sky on Saturday, causing chaos among villagers who were fleeing in cars and motorbikes, while officials rushed to find missing people believed trapped under rubble. Puput Teguh Imelda Kamil semicom18-indo-volcano The Semeru volcano spews volcanic material as it erupts at Lumajang on Dec. Indonesia’s Semeru volcano eruption spread ash across nearby villages while registering pyroclastic flows of up to 13 kilometres (8 miles) this week, prompting the highest level alerts along a broader danger zone surrounding the mountain, Nov. 20, 2025.
Semeru left 178 climbers, porters and guides trapped at the Ranu Kumbolo camping area, some 6.4 kilometres (4 miles) from the crater, authorities said. All were registered and had been provided with enough supplies as they were led down in groups by rescuers after the national park closed its trails. Officials said the site is outside the nearby main 8-kilometre (5-mile) exclusion zone and would be at less risk of direct exposure to the hottest flows as ash continued to fall.
Semeru erupted at least 10 times on Wednesday, causing avalanches of ash, lava and rocks as far as 13 kilometres (8 miles) down its flanks and sending a column of grey clouds skyward over a mile high. Indonesia’s volcanology agency maintained its highest-level alert and warned residents to stay at least 5 miles from the crater and not to enter valleys that channel gas and debris down the Besuk Kobokan River.
About 1,000 residents from the most threatened villages in Lumajang district have been settled into schools, mosques and government offices that were turned into emergency shelters, where volunteers are handing out masks, blankets and food amid the accumulation of ash on rooftops and crops. Local authorities reported at least three residents with burns in accidents related to poor visibility and falling debris, but no loss of life as yet.
Yeast Java’s rescue agency has sent dozens of people in trucks and off-road vehicles to remote hamlets near the slopes, where they will also accompany hikers descending muddy trails. “We have also sent personnel out to search for whether there are still residents or not [in the area],” agency official Prahista Dian said, describing door-to-door checks along paths choked with ash.
The volcano, called Mahameru by locals, stands 3,676 meters (12,060 feet) high and is one of about 130 active volcanoes across the seismically active Indonesian archipelago. The current phase of activity began in 2017 with intermittent gas-and-ash plumes and avalanche deposits of incandescent blocks, the Smithsonian’s Global Volcanism Program said in a long-running Semeru activity summary. This week’s eruption of Semeru, scientists said, falls within that pattern of continuous restlessness, and sometimes fury.
For people in the areas around Semeru, the threat is painfully familiar. A partial collapse of the summit lava dome during the eruption in December 2021 unleashed a barrage of pyroclastic flows down river valleys, where they mixed with heavy rains to form lahars that buried homes and fields, according to an analysis of the disaster by NASA Earth Observatory.
Later humanitarian denominations and Indonesian government tallies would put the death toll in 2021 over 50, with more than 10,000 residents displaced from their homes and dozens still unaccounted for in the coming weeks. According to a field report of the crisis from CARE Indonesia in 2022, at least 50 people had died, and more than 10,400 people were taking shelter in over 400 evacuation points throughout Lumajang regency.
Early coverage of that tragedy, including a contemporaneous AP News report, charted an ever-increasing death toll and attempts to find survivors despite monsoon rains and drifting ash blocking access to buried villages — logistics challenges echoing those being faced by crews in the vicinity of the latest eruption.
For now, officials stress that the latest Semeru eruption has not caused the loss of life that the 2021 disaster did, but say they may need evacuations and trail closures to remain in place for days as they monitor the volcano, clean ash from homes, and keep climbers off its summit as it remains active with sporadic tremors and ash emissions.
