One of South America’s worst tragedies was the November 13, 1985 eruption of Colombia’s Nevado del Ruiz volcano. In the town of Armero with 29,000 residents, 20,000 died and it nearly vanished. The death toll across affected areas was 25,000. Armero was finally deserted and left in ruins.
The volcanic explosion caused a deadly mudflow called a lahar that destroyed everything. The mountain’s glaciers melted from the eruption’s heat, sending floods of mud, ash, and debris. Three large lahars hit Armero, killing many who survived the initial eruption. Despite earlier warnings from experts about eruption hazards, poor evacuation strategies made the disaster worse.