The eruption of nevado del ruiz volcano colombia south america november 13 1985 natural disaster studies vol 4 band 4 amazonde national research council division on engineering and physical sci commission on engineering and technical bucher. On november 13 1985 catastrophic mudflows swept down the slopes of the erupting nevado del ruiz volcano in colombia south america destroying structures in their paths various estimates of deaths ranged as high as 24000 area residents. The 1985 eruption of nevado del ruiz in colombia unleashed deadly lahars that swept through armero killing 20000 people in that town alone credit us geological survey by bethany augliere on nov 13 1985 at a little after 9 pm local time nevado del ruiz a volcano about 130 kilometers from colombias capital city of bogota erupted . The eruption of nevado del ruiz volcano colombia south america november 13 1985 washington dc the national academies press doi 1017226 1784 x save cancel 5 the warning period how did so many people get caught by surprise by ruizs catastrophic lahars in spite of accurate risk assessments and intensive efforts at public education how is it that so many people lost their lives . The november 13 1985 eruption of nevado del ruiz was one in a series of prolonged volcanic and seismic events suggesting that magma is moving near the surface of the volcano