A Minor Eruption of Nevado del Ruiz Ended up Killing Tens of Thousands
Located about 75 miles northwest of Bogota, Colombia’s Nevado del Ruiz is a typical stratovolcano. Those are made of multiple layers, or strata, of hardened lava, pumice (volcanic debris), tephra (dust), and ash. What is atypical about it is that it is located by a river valley, which makes its eruptions produce flows known as “lahars”. Those are mudflows made of a slurry of volcanic debris, rocks, and water. The lahar flows are particularly powerful in Nevado del Rio’s case because it is located high up in the Andes, and its top is covered with a glacier. That is, a lot of frozen water just waiting to come down in an eruption as an avalanche and flow of snow, melted water, and debris.
On November 13th, 1985, after lying dormant for seven decades, Nevado del Ruiz awoke from its slumber and became active. It was a minor eruption, far as volcanic eruptions, but it produced a massive and massively devastating lahar. As lava erupted from the volcano, it melted the mountain’s glaciers, turning them into torrents of water. The result was four huge lahars of mudslides, landslides, and volcanic debris, racing down the mountainside at 30 miles an hour, and picking up speed as they reached and were channeled into mountain gullies.
The mud and debris flows struck nearby settlements, causing particular devastation in the town of Armero. There, about 20,000 of the town’s 29,000 population were killed in what came to be known as the Armero Tragedy. Thousands more died in nearby towns and villages. The haunting images of one victim in particular, 13 year old Omayara Sanchez and the fight to save her life, circulated around the world and was televised live. She was trapped in the mud and debris for days as rescuers frantically tried to free her, before dying of exposure on live TV.
The Nevado del Ruiz eruption killed about 25,000 people. That made it the 20th century’s second deadliest volcanic eruption, exceeded only by the Mount Pelee eruption. Sadly, the massive casualties could have easily been avoided, because volcanologists had detected clear signs of an impending eruption two months before it happened, and warned the authorities of impending disaster.
The location of Nevado del Ruiz by a river valley made the risk of lahars obvious. That, coupled with the glaciers atop the volcano which would supercharge such lahars in case of an eruption, made the dangers to Armero and its surroundings even clearer. Volcanologists and seismologists from multiple organizations warned the Colombian government to evacuate Armero, but were ignored.