An eruption of Mount Semeru, a volcano in East Java province of the Indonesian island of Java, began on 4 December 2021. The eruption began after heavy precipitation caused the collapse of the lava dome at the summit. Pyroclastic flows and lahars damaged at least 5,205 homes and several public buildings. At least 69 people died, 104 more were injured, while more than five remain missing.
Why this event still matters
Historical incidents shape the rules that protect people today — building codes, evacuation policy, warning systems and inspection regimes almost always trace back to a specific disaster. Studying 2021 Semeru eruption alongside current events is how preparedness improves.
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