Mount Semeru Eruptions Prompt Safety Warnings in East Java

Mount Semeru, a towering volcano on the border of Lumajang and Malang in East Java, has erupted dozens of times in recent days, spewing thick ash columns and triggering heavy ashfall on surrounding villages. Authorities have issued urgent warnings to residents, urging them to avoid rivers and areas near the summit due to the risks of deadly lava flows and pyroclastic clouds.

The Semeru observation post in Lumajang recorded three eruptions between midnight and 3 a.m. on Friday, with ash columns rising between 500 and 700 metres above the summit and drifting northwards. On Thursday alone, the volcano erupted 55 times, though fog obscured many of the ash columns from view, according to Mukdas Sofian, an official at the observation post. “We could not observe all of the ash columns because the mountain’s summit was obscured by fog,” Mukdas told Kompas.

Residents have been advised to steer clear of areas within 500 metres of the Besuk Kobokan River, a likely path for lava flows, where pyroclastic clouds and lahar—mudflows of volcanic debris—could extend up to 13 kilometres from the summit. Additionally, an 8-kilometre radius around the summit has been declared off-limits due to the danger of falling rocks. Similar warnings apply to the Besuk Kembar and Besuk Sat rivers and their tributaries.

Ashfall and Weather Challenges

The districts of Candipuro, Pronojiwo, and Pasrujambe, located 13 to 18 kilometres from Semeru’s summit, have experienced moderate to heavy ashfall in recent days. Authorities have recommended that residents wear masks and goggles when outdoors to protect against the volcanic dust. Sugiyono, an official at Semeru’s Curah Kobokan observation post, attributed the ashfall to strong winds at the summit, which have carried accumulated volcanic material downslope. “These strong winds have also made it challenging for us to observe Semeru’s ash columns,” he noted on Thursday.

Patria Dwi Hastiadi, head of the Lumajang Disaster Mitigation Agency (BPBD), described the recent eruptions as within the range of normal volcanic activity. However, he cautioned residents living at the foot of the mountain to avoid rivers due to the heightened risk of lahar flows, particularly amid ongoing adverse weather. “We urge residents to stay away from rivers due to the significant risk of lahar flows, especially given the ongoing bad weather,” Patria said.

A History of Volatility

Standing at 3,676 metres, Mount Semeru has shown increased activity since November last year. In January alone, it erupted 475 times, averaging 15 eruptions per day. The volcano, one of Indonesia’s most active, has a tragic history of destructive eruptions. In December 2021, an eruption claimed 51 lives and displaced nearly 10,000 people. A year later, in December 2022, another major eruption forced the evacuation of 2,000 residents as ash clouds soared 15 kilometres into the sky.

Given this recent spike in activity and the prevailing weather conditions, authorities have announced that Mount Semeru will remain off-limits to the public until further notice. The volcano’s alert status remains at Level II (Waspada, or advisory) on Indonesia’s four-tier alert system, indicating a need for heightened vigilance but stopping short of a full emergency declaration.

Community Impact and Preparedness

The recurring eruptions of Mount Semeru pose a persistent threat to the communities in East Java, many of whom rely on agriculture and live in close proximity to the volcano’s slopes. Ashfall can devastate crops, contaminate water sources, and pose respiratory risks, particularly to vulnerable groups such as children and the elderly. While the current eruptions have not yet necessitated large-scale evacuations, the memories of past disasters loom large, prompting local officials to prioritise safety measures.

Indonesia, situated on the Pacific Ring of Fire, is home to more than 70 active volcanoes, with Semeru being one of the most closely monitored due to its frequent activity and proximity to populated areas. The government’s disaster mitigation efforts, while robust in urban centres, often face challenges in rural regions where resources and infrastructure may be limited. For now, the focus remains on public awareness and adherence to safety guidelines to minimise the risks posed by Semeru’s unrest.

As weather conditions continue to complicate monitoring efforts, officials are bracing for the possibility of further eruptions. Residents in the affected districts are urged to remain vigilant, heed evacuation warnings if issued, and prepare for potential disruptions. Mount Semeru’s latest activity serves as a stark reminder of the volatile beauty of Indonesia’s natural landscape—a force that demands both respect and caution.