Mount Semeru, one of Indonesia’s most active volcanoes, erupted Tuesday evening, sending an ash column approximately 1,000 meters (3,280 feet) into the sky and triggering evacuations in East Java province. The eruption, which began on March 10, 2026, produced a hot avalanche cloud that traveled roughly three kilometers (1.86 miles) southeast along the Besuk Kobokan river channel, posing a significant threat to nearby communities.
The Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG), Indonesia’s volcanology agency, reported continued activity at Semeru between March 5th and March 11th, with daily eruptive events recorded by seismic networks. Although no emissions were visible on March 5th, subsequent days saw white-to-gray ash plumes rising between 300 and 1,000 meters above the summit, drifting in northerly, northeasterly, and easterly directions. The latest eruption on Wednesday, March 11th, continued this pattern of ash emissions, prompting further alerts.
Eruption Details and Impact
The eruption on Tuesday lasted nearly five minutes, registering a maximum seismic amplitude of 12 mm, according to monitoring officials. The thick gray ash drifted towards the northeast and east, impacting villages and prompting authorities to urge residents to avoid activities within a five-kilometer (3.1 mile) radius of the crater. A wider area, extending up to 13 kilometers (8.1 miles) from the summit in the southeastern sector along the Besuk Kobokan river channel, is also under alert due to the risk of pyroclastic flows, lava avalanches, and lahars.
On Wednesday, March 11th, discrete volcanic ash emissions were observed at Flight Level 150 (approximately 15,000 feet or 4,600 meters), moving in a northeasterly direction. This poses a potential hazard to aviation, and authorities are monitoring the situation closely. The alert level for Mount Semeru remains at “Level 3 – Standby,” indicating that the volcano is exhibiting signs of increased activity.
Evacuations and Safety Measures
Authorities have initiated evacuations in vulnerable areas, prioritizing the safety of residents living near the volcano. The Indonesian government is working to provide assistance to those displaced by the eruption, including shelter, food, and medical care. The National Disaster Management Agency (BNPB) is coordinating the response efforts, working with local authorities to assess the damage and provide support to affected communities.
The risk of lahars – mixtures of volcanic ash, rock, and water – remains a significant concern, particularly during periods of rainfall. The Besuk Kobokan river channel is particularly vulnerable, and residents in that area have been advised to remain vigilant and follow the instructions of local authorities.
Ongoing Monitoring and Future Outlook
The PVMBG continues to closely monitor Mount Semeru’s activity, analyzing seismic data, gas emissions, and visual observations to assess the volcano’s behavior. The agency is providing regular updates to the public and coordinating with local authorities to ensure effective disaster preparedness and response. The alert level will be adjusted based on the volcano’s activity, and further evacuations may be necessary if the situation escalates.
As of March 11, 2026, Mount Semeru remains under close observation, and the potential for further eruptions remains. Residents in the surrounding areas are urged to stay informed, heed the warnings of authorities, and be prepared to evacuate if necessary. The situation is dynamic, and ongoing monitoring is crucial to mitigating the risks associated with this active volcano.
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