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On 19 November 2025 Mount Semeru, an active stratovolcano in East Java, Indonesia, erupted violently. The eruption sent a column of ash and gas more than 13 kilometres into the atmosphere and generated pyroclastic flows that cascaded down its slopes. Authorities raised the alert to the highest level and evacuated about 300 residents from nearby villages.
Background
Mount Semeru (also known locally as Mahameru) is the highest peak on Java, rising 3 676 metres above sea level. It forms part of the Bromo–Tengger–Semeru National Park and sits on the Pacific Ring of Fire, where the Australian and Eurasian tectonic plates converge. Semeru is one of Indonesia’s most active volcanoes, frequently erupting with varying intensity.
The volcano has a history of dangerous eruptions. In December 2021 an explosive episode triggered pyroclastic flows and lahars (mudflows) that buried villages and killed more than 50 people. Because of its persistent activity, Indonesian authorities maintain a multi‑tiered alert system and encourage residents to stay beyond a safety radius of 5–8 kilometres from the crater.
Details of the 2025 eruption
- Eruption timing and plume: The eruption occurred at 2:13 pm local time. Volcanologists reported an ash plume rising to about 13 km, which can disrupt aviation and rain ash on settlements downwind.
- Pyroclastic flows: Avalanches of hot gas, ash and volcanic debris flowed down the volcano’s south‑eastern slopes into river valleys. Such flows can reach speeds of hundreds of kilometres per hour and are lethal within minutes.
- Evacuations: Local disaster management agencies evacuated around 300 villagers to temporary shelters. Residents were advised to avoid river valleys and to wear masks to protect against ash inhalation.
- Alert level and monitoring: Indonesia’s Centre for Volcanology and Geological Hazard Mitigation raised the alert status to Level IV (Awas), the highest tier. Continuous monitoring using seismographs and satellite imagery helps authorities issue early warnings.
About Semeru
- Geology: Semeru is a stratovolcano composed of layers of lava and ash. Its summit crater periodically emits lava domes that can collapse and trigger pyroclastic flows.
- Human settlement: Fertile volcanic soils support agriculture on the lower slopes. Numerous villages and coffee plantations exist within 10 km of the crater, making evacuation and disaster preparedness crucial.
- Volcanic hazards in Indonesia: Indonesia hosts more than 130 active volcanoes—the most of any country—due to its tectonic setting. The government continuously monitors them and runs community‑based preparedness programmes.
Significance
The Semeru eruption highlights the perennial risk posed by Indonesia’s volcanoes. Rapid evacuation and effective warning systems can save lives, but long‑term resilience requires land‑use planning, community education and investment in monitoring technology. The 2025 eruption is a reminder of the dynamic nature of Earth’s geology and the importance of disaster preparedness in vulnerable regions.
Source: NDTV