Armero tragedy Colombia (1985)

The Armero tragedy was one of the major consequences of the eruption of the Nevado del Ruiz in Tolima, Colombia on November 13, 1985. After 69 years of dormancy, the volcano's eruption caught nearby towns unaware, even though the government had received warnings to evacuate the area.
As pyroclastic flows erupted from the volcano's crater, they melted the mountain's glaciers, sending four enormous lahars (volcanically induced mudslides, landslides, and debris flows) down its slopes at 60 kilometers per hour (40 miles per hour). The lahars picked up speed in gullies and coursed into the six major rivers at the base of the volcano; they engulfed the town of Armero, killing more than 20,000 of its almost 29,000 inhabitants. Casualties in other towns, particularly Chinchiná, brought the overall death toll to 23,000.

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TheDisaster.net 2013