November 1985 volcanic eruption in Colombia
Source (Wikipedia): Armero tragedy

The Armero tragedy occurred following the eruption of the Nevado del Ruiz stratovolcano in Tolima, Colombia, on November 13, 1985. The volcano’s eruption after 69 years of dormancy caught nearby towns unprepared, even though volcanological organizations had warned the government to evacuate the area after they detected volcanic activity two months earlier.