Java's Mount Semeru Erupts, Prompting Highest Alert and Mass Evacuation

Mount Semeru, the highest peak on the Indonesian island of Java, experienced a series of vigorous eruptions culminating on Wednesday, November 19, 2025. The stratovolcano, located in East Java province, is recognized as one of Indonesia's most active mountains, having been in near-continuous eruption since 1967. The intense volcanic episode prompted Indonesian authorities to immediately elevate the mountain's hazard status to Level IV, the highest possible designation, reflecting the severity of the ongoing activity.

Following the significant eruptions, authorities reported that searing clouds composed of ash, rock fragments, and gas were projected down the slopes, with some flows reaching distances up to 13 kilometers from the central crater between midday and dusk on Wednesday. The Indonesian Geology Agency confirmed that a thick column of hot clouds ascended approximately 2 kilometers into the atmosphere during the peak of the activity. In response to the persistent instability and the threat posed by these pyroclastic density currents, the mandatory exclusion zone surrounding the crater was substantially expanded to an 8-kilometer radius.

As a direct consequence of the escalating threat, an organized evacuation effort was initiated, resulting in the relocation of over 900 residents from the most vulnerable communities in the Lumajang district. A spokesperson for the National Disaster Mitigation Agency (BNPB), Abdul Muhari, noted that more than 300 residents from the three villages deemed most at risk were moved to government-provided shelters. The Lumajang Regent, Indah Amperawati, called for immediate evacuation of high-risk areas, including communities in Sumberwuluh Village, Jugosari, Candipuro Subdistrict, and Pronojiwo Subdistrict, emphasizing resident safety as the paramount concern.

Compounding the ground-level evacuation challenge, rescue operations were mobilized on Thursday, November 20, to address a group stranded overnight near the summit. Approximately 170 individuals, identified as climbers, porters, and guides, were reported to be in need of safe relocation from the Ranu Kumbolo monitoring post on the 3,676-meter mountain. Officials from the Bromo-Tengger-Semeru National Park (TNBTS) confirmed the group's status, noting the stranded individuals were currently safe at the monitoring post.

Although the intensity of the eruptions demonstrated a slight abatement by Thursday morning, officials maintained a high state of caution, stressing that the overall situation remained highly volatile. The public was strictly advised to adhere to the established safety perimeters, particularly avoiding the area along the Besuk Kobokan River, which serves as a primary channel for potential lava flows. This event recalls the significant December 2021 eruption, which resulted in 51 fatalities and the displacement of over 10,000 people, underscoring the inherent risks of residing near this geologically active zone situated on the Pacific "Ring of Fire." The Lumajang Regency Government declared a seven-day emergency response status, effective from November 19 to November 26, 2025, to manage the immediate aftermath and recovery.