Nevado del Ruiz

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Nevado del Ruiz
Steam in July, 2007
Elevation	5,321 metres (17,457 ft)
Location	Colombia
Range	Cordillera Central
Coordinates	4°53′33″N, 75°19′25″W
Type	Stratovolcano
Volcanic arc/belt	Andean Volcanic Belt
Last eruption	1991
First ascent	1936 by M. Rapp and party

Nevado del Ruiz is an Andean stratovolcano in Caldas Department, Colombia. It is the northernmost volcano of the Andean Volcanic Belt and lies about 15 miles southeast of Manizales, with the town of Armero in the valley below. It is the northernmost and highest Colombian volcano with historical activity. Its 1985 eruption produced a lahar which completely buried the city and caused an estimated 23,000 deaths in what came to be known as the Armero tragedy.

The Nevado del Ruiz was produced by subduction of the oceanic Nazca Plate beneath the continental South American Plate. Stratovolcanoes in the Andes are for the most part Plinian, as is Nevado del Ruiz, and produce pyroclastic flows. Nevado del Ruiz consists of andesite and dacite lava.

Nevado del Ruiz has been called "the Sleeping Lion" by the local towns around it. It had been a dormant volcano for nearly 150 years.

1 1985 eruption
2 Aftermath
3 See also
4 Footnotes
5 References

[edit] 1985 eruption

Before the eruption in 1985

Space radar image of Nevado del Ruiz

On November 13th , 1985, at 9:08 pm, Nevado del Ruiz erupted. Pyroclastic flows melted ice and snow at the summit which formed lahars that rushed down several river valleys. The lahars were up to 50 meters thick and traveled more than 100 kilometers.^[1]

Many houses and towns were destroyed by the lahars. The town of Armero was completely covered by debris, killing approximately 21,000 people (out of 28,700). The eruption caused an estimated 23,000 deaths, 5,000 injuries, and destroyed more than 5,000 homes. This was the second-deadliest volcanic disaster in the 20th century (the 1902 eruption of Mount Pelée was the worst). The disaster gained some major international notoriety due in part to a photograph taken by photographer Frank Fournier, of a young girl named Omayra Sánchez who was trapped beneath rubble for three days before she died. ^[2]

Survivors who fled to other towns in the area were gradually housed in new government schemes, but problems for the displaced population occurred for many years after. The villagers were warned about the possibility of the disaster but because of past false information about it happening and the false statements of the Tolima Department Governor, among other officials, saying that the volcano was not going to erupt, many people did not believe these warnings.

There were hundreds of cases where people a few feet apart were either killed by the massive mud and stone wave or survived the disaster. Among the terrible consequences for survivors was that the temperature of the mud and rock avalanche served as a gigantic culture media for all kinds of pathogenic fungus and bacteria. Some survivors who had minor cuts were killed by the infections, which could not be treated with known antibiotics.

[edit] Aftermath

Nevado del Ruiz 2006

The eruption cost Colombia 7.7 billion dollars; about 20% of the country’s GNP for the year in question. A lack of preparation contributed to the high death toll. Armero had been built directly on old mudflows and authorities ignored a hazard-zone map which showed the potential damage to the town if lahars were to avalanche down the mountain. Habitants were also told to stay inside and avoid the falling ash, not thinking the mudflows would bury them.

Several years later the scarred sides of the creeks along which the lahar flowed were clearly visible from commercial airplanes. Even in the mid 1990s the town was covered with up to 20 feet of ash and debris. Local villagers harvested stones for building work and often, still found human bones that they placed on the shrines that dot the area. A few small trees were trying to grow, protected from wandering animals by makeshift fences.

Now a new system can detect lahars, giving people more warning to evacuate before they happen. The system involves the use of Acoustic Flow Monitors (AFM) which analyze ground shaking that could potentially result in a lahar. These AFMs are placed in the volcano and warn officials if there is an exceedingly high amount of shaking.