Armero Tragedy (1985): Nevado del Ruiz Eruption in Colombia

The Armero tragedy took place on the night of 13 November 1985, when an eruption of the Nevado del Ruiz volcano in Colombia sent torrents of volcanic mud down river valleys and buried the town of Armero. About 23,000 people died, most of them in Armero, making it the deadliest volcanic disaster of the twentieth century after the eruption of Mount Pelée in 1902. Because scientists had warned of the danger beforehand, Armero became a lasting symbol of how hazard warnings can fail.

Background: the volcano and the town

Nevado del Ruiz is a glacier-capped stratovolcano in the Central Cordillera of the Colombian Andes, about 5,300 metres high and some 130 kilometres west of Bogotá. Its ice cap feeds several rivers that flow down steep valleys to the lowlands. Earlier eruptions, in 1595 and 1845, had sent lahars down the same valleys; in 1845 mudflows killed around 1,000 people in the area where Armero later stood.

Armero was a prosperous agricultural town on the plain of the Lagunilla River in Tolima department, known for its cotton and rice. In 1985 it had about 29,000 inhabitants. The town was built partly on deposits left by earlier lahars, though few residents were aware of this.

Warning signs

The volcano showed signs of unrest from November 1984, with earthquakes, steam emissions and sulphur deposits. On 11 September 1985 a steam-driven (phreatic) explosion produced a mudflow that travelled about 27 kilometres down the Azufrado valley. Colombian and foreign scientists began monitoring the mountain with limited equipment.

On 7 October 1985 Colombia’s geological service, INGEOMINAS, released a preliminary hazard map. It showed that lahars could reach Armero within a few hours of an eruption and that the town was at very high risk. The map received some attention in the press, but it was criticised by some officials as alarmist, and no evacuation plan was put in place. Emergency planning was also hampered by uncertainty about whether the volcano would erupt at all and by fears of the cost of an unnecessary evacuation.

The government’s attention was further divided. On 6-7 November 1985, a week before the eruption, the guerrilla group M-19 seized the Palace of Justice in Bogotá, and the siege and military recapture left around 100 people dead, including judges of the Supreme Court.

13 November 1985: the eruption

On the afternoon of 13 November ash began to fall on Armero. Local authorities and the town’s radio station advised people to stay calm and remain indoors. At about 9:08 p.m. the volcano erupted more violently. Hot pyroclastic flows swept across the summit ice cap and melted roughly a tenth of its snow and ice.

The meltwater mixed with loose ash and rock to form lahars, flows with the consistency of wet concrete. They poured down the Lagunilla, Gualí, Azufrado and other river valleys, growing as they picked up soil and debris and reaching speeds of tens of kilometres per hour. At around 11:30 p.m. the first lahar reached Armero, about 74 kilometres from the summit, followed by further pulses. In places the mud was several metres deep. Most of the town was destroyed within minutes, and power had already failed.

Survivors later described a roar like an approaching train before the mud arrived in the dark. Some people escaped by running to higher ground on the edge of town or by climbing onto roofs and into trees, while others were carried for long distances by the flow. Many of those who survived the night were trapped in the mud with serious injuries, and helicopter crews began to reach them only after daybreak on 14 November. On the western side of the volcano, a lahar down the Chinchiná River killed about 1,800 people.

Omayra Sánchez

In the days after the disaster, rescue efforts were slow and difficult because of the mud and a lack of equipment, and many survivors waited for hours or days. The most famous victim was Omayra Sánchez, a 13-year-old girl trapped up to her neck in water and debris in the ruins of her family’s home. Rescuers could not free her without heavy machinery, which did not arrive. She spoke with journalists and volunteers for about three days before dying on 16 November 1985.

The French photojournalist Frank Fournier photographed her shortly before her death. The image, which won the World Press Photo of the Year award, provoked worldwide debate both about journalism and about the Colombian government’s handling of the crisis.

Death toll and aftermath

About 23,000 people died in total, more than 20,000 of them in Armero, where roughly three-quarters of the population was killed. Thousands more were injured, and many children were separated from their families. President Belisario Betancur declared a national emergency, and aid came from many countries.

Armero was never rebuilt. Survivors were resettled in nearby towns, especially Guayabal and Lérida. The ruins became a memorial site, visited in July 1986 by Pope John Paul II, who prayed for the victims. The eruption itself was relatively small, rated 3 on the Volcanic Explosivity Index, which made the scale of loss all the more striking.

By the numbers

Lessons for volcano hazards

Investigators, including the volcanologist Barry Voight, concluded that the catastrophe was not caused by a lack of scientific knowledge but by failures of communication, decision-making and planning. The hazard map was broadly accurate, yet it did not lead to timely action.

The disaster led the US Geological Survey and the US Agency for International Development to found the Volcano Disaster Assistance Program in 1986, drawing on lessons from the Mount St. Helens eruption. The programme helps countries monitor volcanoes and plan evacuations, and it played a key role in forecasting the 1991 eruption of Mount Pinatubo in the Philippines. After further unrest in 2012 and in 2023, Colombian authorities raised alert levels and prepared evacuations of communities in the river valleys around the volcano, drawing directly on the memory of Armero. Colombia had also created a national disaster prevention system and strengthened monitoring of Nevado del Ruiz through an observatory in Manizales.

Timeline

• 1845: Lahars from Nevado del Ruiz kill about 1,000 people in the Lagunilla valley.
• 1984, November: The volcano begins showing signs of unrest.
• 1985, 11 September: A phreatic eruption produces a lahar on the Azufrado River.
• 1985, 7 October: INGEOMINAS publishes a hazard map showing Armero at high risk.
• 1985, 13 November, c. 9:08 p.m.: The main eruption melts part of the summit ice cap.
• 1985, 13 November, c. 11:30 p.m.: Lahars reach and bury Armero.
• 1985, 16 November: Omayra Sánchez dies after three days trapped in the ruins.
• 1986: The Volcano Disaster Assistance Program is founded.

Why it matters

Armero showed that even a small eruption can be catastrophic when people live in the path of lahars, and that accurate science is useless without effective warning and evacuation. Like the destruction of Saint-Pierre in the eruption of Mount Pelée, it remains a central case study in volcanic risk management worldwide.