Lessons from Armero, Colombia

It should come as no surprise that efficient information flow is essential for effective hazards assessment and risk mitigation during a volcano crisis. That fact was made terribly clear on the night of 13 November 1985, when huge lahar triggered by a small eruption of ice-clad Nevado del Ruiz Volcano in Colombia killed more than 23,000 people, most of them asleep, and virtually erased the hapless town of Armero from the map.

The first warnings had come almost a year earlier. Climbers on the 5,200-m peak noticed increased fumarolic activity and felt earthquakes starting in November 1984 and, on 22 December, three widely felt earthquakes were accompanied by small explosions from Arenas Crater near the volcano’s summit. Felt earthquakes and abnormal fumarolic activity persisted into 1985. Seismometers installed at the volcano in July confirmed a high level of earthquake activity that intensified in early September before a strong phreatic eruption on 11 September. A preliminary volcano hazards map published in October warned that a magmatic eruption would almost surely trigger damaging lahars. The final version of the map, issued publicly on 8 November 1985, placed the town of Armero squarely in a zone of high lahar hazard. Five days later, and more than 8 hours after the beginning of the paroxysmal eruption, Armero and most of its residents disappeared under a river of mud (Herd and Comité de Estudios Vulcanologicos, 1986).

In hindsight, this terrible tragedy could have been avoided. The volcano provided ample warning, an accurate hazards zonation map was available, the volcano was being continuously monitored, an evacuation order was issued hours before the lahar reached Armero, and the safety of higher ground was within walking distance for most residents. What went so terribly wrong? In spite of hard work by many and heroic efforts by some, essential information about how to mitigate the impending disaster was not available where and when it was critically needed. The advance warning was not understood by many of those at risk, and they received no short-term instructions to move to higher ground as the giant lahar bore down on them. In the words of one scientist who experienced the Armero tragedy firsthand: ‘... the catastrophe was not caused by technological ineffectiveness or defectiveness, nor by an overwhelming eruption or an improbable run of bad luck, but rather by cumulative human error’ (Voight, 1996, p.719). Shortly after the disaster, the US Geological Survey (USGS) and the Office of Foreign Disaster Assistance of the US Agency for International Development (USAID OFDA) established the Volcano Disaster Assistance Program (VDAP) to mitigate losses from future eruptions worldwide by applying the lessons learned so tragically at Armero.

Source: Volcano Deformation by Dzurisin