Mount Semeru in East Java erupted Wednesday, sending hot ash, pyroclastic flows and lava down its slopes and prompting authorities to raise the alert to the highest level. More than 300 residents from three high-risk villages in Lumajang district were evacuated and the exclusion zone was extended to 8 kilometers (5 miles). About 178 people remained at the Ranu Kumbolo monitoring post but were reported safe after being forced to stay overnight by bad weather. Semeru’s last major eruption in December 2021 killed 51 people and forced large-scale evacuations.
Mount Semeru Erupts in East Java: Ash, Lava Flows and Mass Evacuations
Mount Semeru in East Java erupted Wednesday, sending hot ash, pyroclastic flows and lava down its slopes and prompting authorities to raise the alert to the highest level. More than 300 residents from three high-risk villages in Lumajang district were evacuated and the exclusion zone was extended to 8 kilometers (5 miles). About 178 people remained at the Ranu Kumbolo monitoring post but were reported safe after being forced to stay overnight by bad weather. Semeru’s last major eruption in December 2021 killed 51 people and forced large-scale evacuations.
11:20 PM, 11/19/2025Environment
Indonesia’s Mount Semeru, the highest peak on Java, erupted Wednesday, sending scorching clouds of ash and flows of rock, lava and gas down its slopes and blanketing nearby villages. Authorities raised the volcano’s alert to the highest level and ordered evacuations as they widened the danger zone around the crater.
What happened
Indonesia’s Geology Agency said Semeru in East Java unleashed hot pyroclastic flows that traveled as far as 7 kilometers (4.3 miles) down the mountain multiple times from midday into the evening. A dense column of hot material rose roughly 2 kilometers (1.2 miles) into the air.
Impact and response
Officials raised the alert level twice during the day, moving it from the third-highest setting to the maximum. National Disaster Mitigation Agency spokesperson Abdul Muhari said more than 300 residents from three high-risk villages in Lumajang district were moved to government shelters. Authorities expanded the exclusion zone to 8 kilometers (5 miles) from the crater and warned people to avoid the Besuk Kobokan River valley, a known channel for hot flows and lahars.
“They are currently safe at Ranu Kumbolo monitoring post,” Endrip Wahyutama, a spokesperson for Bromo-Tengger-Semeru National Park (TNBTS), said in a video statement, noting the post is about 4.5 kilometers (2.7 miles) from the crater and not in the path of the observed hot cloud.
People on the mountain
Local authorities reported about 178 people remained at the Ranu Kumbolo monitoring post on the mountain—137 climbers, 15 porters, seven guides and six tourism officials—but they were reported safe. Park officials said bad weather and rain forced the group to spend the night at the post.
Context
Semeru, also known locally as Mahameru, has been intermittently active for centuries. Its most recent major eruption in December 2021 killed 51 people and burned many others after villages were buried in volcanic mudflows; more than 10,000 people were evacuated at that time and roughly 2,970 homes were later moved out of the danger zone. Indonesia—an archipelago of more than 280 million people—lies on the Pacific "Ring of Fire," a region of frequent earthquakes and volcanic eruptions.
Authorities continue to monitor the situation closely and urge residents and visitors to follow official guidance and evacuation orders. Travel and access restrictions remain in effect around the mountain while assessments continue.