The Armero tragedy was the major consequence of the November 13, 1985 eruption of Nevado del Ruiz in Tolima, Colombia. Lahars (mudslides) from the mountain's melting ice cap swept down its slopes. One covered the town of Armero and killed most of its population, over 20,000 people out of 29,000 inhabitants. Deaths in other towns, particularly Chinchina, brought the overall death toll to 23,000. Footage and photos of Omayra Sanchez, a young victim of the tragedy, were published around the world.
This was the second-deadliest volcanic disaster in the 20th century, being surpassed only by the 1902 eruption of Mount Pelee, and is the fourth-deadliest volcanic eruption in recorded history.
Geologists and other experts had warned authorities and media outlets about the danger over the weeks and days leading up to the eruption. When interviewed by reporters, a number of different officials told the inhabitants that the city was safe and downplayed the possible effects, possibly due to the cynicism created by previous false evacuation orders. The night before the explosion, the mayor of Armero himself assured citizens that there was nothing to fear.
Armero was the third largest town in the Tolima Department after the Department capital, Ibague and the city of Espinal. The volcano had been dormant for almost 150 years before 1985.
Eruption and lahars
At 9:09 pm, on November 13, 1985, Nevado del Ruiz erupted, ejecting dacitic tephra more than into the atmosphere. The total mass of the erupted material (including magma) was 35 million tonnesonly 3% of the amount that erupted from Mount St. Helens in 1980. The eruption reached a value of 3 on the Volcanic Explosivity Index. The mass of the ejected sulfur dioxide was about 700,000 tonnes, or about 2% of the mass of the erupted solid material, making the eruption atypically sulfur-rich.
The eruption produced pyroclastic flows that melted summit glaciers and snow, generating four thick lahars that raced down river valleys on the volcano's flanks. It also destroyed a small lake that was observed in Arenas crater several months before the eruption. Water in such volcanic lakes tends to be extremely salty and contain dissolved volcanic gases. The lake's hot, acidic water significantly accelerated the melting of the ice; this effect was confirmed by the large amounts of sulfates and chlorides found in the lahar flow.
The lahars, formed of water, ice, pumice, and other rocks, mixed with clay as they traveled down the volcano's flanks. They ran down the volcano's sides at an average speed of 60 km per hour, eroding soil, dislodging rock, and destroying vegetation. After descending thousands of meters down the side of the volcano, the lahars were directed into all of the six river valleys leading from the volcano. While in the river valleys, the lahars grew to almost 4 times their original volume. In the Guali River, a lahar reached a maximum width of .
One of the lahars virtually erased the small town of Armero in Tolima Department, which lay in the Lagunilla River valley. Only one quarter of its 28,700 inhabitants survived. The next morning, the pilot of a plane transmitting to Colombia's Civil Defense system, overflying what was supposed to be Armero, is known to have remarked: "Dios mio, Armero ha sido borrado del mapa" .
A second lahar, which descended through the valley of Chinchina River, killed about 1,800 people and destroyed about 400 homes in the town of Chinchina. In total, over 23,000 people were killed and approximately 5,000 were injured. More than 5,000 homes were destroyed. The Armero tragedy, as the event came to be known, was the second-deadliest volcanic disaster in the 20th century, being surpassed only by the 1902 eruption of Mount Pelee, and is the fourth-deadliest volcanic eruption in recorded history. It is also the deadliest known lahar, and Colombia's worst natural disaster.
The loss of life during the 1985 eruption was due partly to the fact that scientists did not know precisely when the eruption would occur, and the authorities would not take costly preventative measures without clear warnings of imminent danger. Because the volcano's last substantial eruption occurred 140 years ago, it was also hard for many to accept the danger the volcano presented; locals even called it the "Sleeping Lion". Hazard maps showing Armero would be completely flooded after a eruption were distributed more than a month before the eruption, but the Colombian Congress criticized the scientific and civil defense agencies for scaremongering. Local authorities failed to alert people to the seriousness of the situation, with Armero's mayor and a priest both reassuring the populace after an ash eruption on the afternoon of November 13 and the consequent ashfall early that evening. Another factor was the storm that hit that evening, causing electrical outages and hindering communications. Civil defense officials from four nearby towns tried to warn Armero the lahar was approaching in the hour or so before it reached Armero, but failed to make radio contact.
Scientists later looked back to the hours before the eruption and noticed that several long-period earthquakes, which start out strong and then slowly die out, had occurred in the final hours before the eruption. Volcanologist Bernard Chouet said that, "the volcano was screaming 'I'm about to explode'", but the scientists who were studying the volcano at the time of the eruption were not able to read this signal.
The eruption occurred at the same time as the 1985 Mexico City earthquake, so the amount of supplies sent was slightly lowered. The US government spent over one million dollars to help and US Ambassador to Colombia Charles S. Gillespie Jr. donated an initial 25,000 dollars to Colombian disaster assistance institutions. The Office of Foreign Disaster Assistance of the US Agency for International Development (AID) additionally sent one member of the United States Geological Survey (USGS), along with an AID disaster-relief expert and 12 helicopters with support and medical personnel from Panama. The US then sent other aircraft, in addition to more supplies, including 500 tents, 2,250 blankets, and several tent repair kits. Twenty-four other nations contributed to the rescue and assistance of survivors. Ecuador supplied a mobile hospital, while Iceland's Red Cross sent 4,650 dollars. French government sent their own medical supplies with 1,300 tents. Japan sent a total of 1.25 million dollars along with eight doctors, nurses, and engineers to the site, plus 50,000 dollars to the United Nations for relief efforts.
The eruption cost Colombia 7.7 billion dollars, which was about 20% of the countrys GNP for that year.
A lack of preparation for the disaster contributed to the high death toll. Armero had been built on old mudflows; authorities had ignored a hazard-zone map that showed the potential damage to the town if lahar were to avalanche down the mountain. Habitants also stayed inside their dwellings and avoided the falling ash, not thinking that the mudflows would bury them, as officials from the area told them to.
The disaster gained major international notoriety due in part to a photograph taken by photographer Frank Fournier of a young girl named Omayra Sanchez, who was trapped beneath rubble for three days before she died. Two photographers from the Miami Herald also won a Pulitzer Prize for photography of the effects of the lahar. Dr. Stanley Williams of Louisiana University said that following the eruption, "With the possible exception of Mount St. Helens in the state of Washington, no other volcano in the Western Hemisphere is being watched so elaborately." In response to the eruption, the USGS Volcano Crisis Assistance Team was formed in 1986, and the Volcano Disaster Assistance Program.
The volcano erupted several more times through 1985–1994.
The tragedy at Armero bears resemblances to what happened to Pompeii and Herculaneum in the AD 79 eruption of Mount Vesuvius. However, in that eruption, the towns were buried directly by volcanic ash and pyroclastic surges, not by a lahar, as Armero.
Information about Armero
Video about emergency response to the tragedy (15 minutes), Pan American Health Organization
This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article Armero tragedy