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 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 destroying structures in their paths various estimates of deaths ranged as high as 24000 residents though the nature and extent of risk posed by the mudflows to local communities were well documented before the event and extensive efforts had been made to communicate this information to those at risk the affected communities were caught largely unaware. The 13 november 1985 eruption of nevado del ruiz volcano in colombia released a small volume of pyroclastic material and a disproportionately large volume of volcanic gas before the eruption. Eruption of the nevado del ruiz volcano colombia on 13 november 1985 tephra fall and lahars naranjo jl sigurdsson h carey sn fritz w a small plinian eruption of the nevado del ruiz volcano in colombia ejected 35 x 1010 kilograms of mixed dacite and andesite tephra on 13 november 1985 with a maximum column height of 31 kilometers above sea level small pyroclastic flows and surges