Eruption History:

Throughout its existence, Nevado del Ruiz has had 22 eruptions. Its earliest eruption occurred in 6660 BC in the Arenas Crater, its most recent in 1985 as a VEI 3 also in the Arenas Crater. A technique called Tephrochronology has been used to prove this very early eruption, and the first historically documented eruption occurred in 1570. Nevado del Ruiz's largest eruption occurred in 1595 in the Arenas Crater as a VEI 4, but the most well known, and the most recent was the 1985 eruption. As the worst volcanic disaster of the 21 century in South America, beginning at 3:06 pm, this eruption killed over 23,000 people. It consisted of hot pyroclastice flows and surges, as well as deadly floods and lahars that surged through the valleys. The eruption ejected ash for miles and a very small amount of magma, but generated high-volume debris flows that were the the killers of many. Mudflows and lahars traveled over 60 miles, buried whole towns, more than 5,000 homes, killed over 23,000 inhabitants, and injured over 5,000 people. The explosion also left 15,000 animals dead, 8,000 homeless, and the estimated cost of the eruption was 1 billion dollars. The town of Armero, which was closest to the volcanoes base, was hit the hardest. The whole town was buried and destroyed, and three quarters of the 28,700 people who lived there died. Since this lethal eruption, the volcano has has very limited volcanic activity, but the effects of the Nevado del Ruiz eruption can still be seen today.