A volcanic mudflow buried the Colombian town of Armero
On this day · 13 November 1985
When Nevado del Ruiz erupted on November 13, 1985, melting glaciers unleashed lahars that erased a town in minutes.
At 9:09 p.m. on November 13, 1985, the glacier-capped Colombian volcano Nevado del Ruiz roared back to life, hurling ash high into the night sky. The eruption itself was modest. The danger lay underfoot: the heat melted the summit ice, sending lahars — fast-moving slurries of mud, rock, and meltwater — racing down the river valleys.
The first wave reached the sleeping town of Armero around 11:30 p.m., more than two hours after the eruption. It buried much of the town under meters of debris, killing more than 20,000 of Armero’s roughly 29,000 residents. In all, over 23,000 people died.
Warnings had been issued, but power was out and the message never reached the people who needed it most.
The tragedy became a grim lesson in volcanic hazard mapping and the cost of failing to act on a forecast that was, in fact, broadly correct.
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