Nevado del Ruiz is a stratovolcano, with a history of generating deadly lahars from relatively small eruptions (SDSU, 2006). The Nevado del Ruiz volcano stands at an elevation of 5, 389 meters above sea level. It is the tallest volcano of any Columbian Mountain. It is also the most northern of any stratovolcano in the area. Nevado del Ruiz is part of the Andes Volcanic Chain of western South America. It is located approximately 500 kilometers from the equator and its summit is covered with 25 square meters of snow and ice (SDSU, 2006). The Nevado del Ruiz volcano usually has only steam eruptions, with minimal to no pyroclastics ejected. It is also famous for starting lahars (mudflows) that generate to great speeds, knocking anything down in their path.


There were many precursors leading up to the 1985 eruption of Nevado del Ruiz. Small earthquakes and fumaroles that spew gas and steam were detected near the summit. There were also small eruptions detected along the summit that contained small magma explosions (Suite101, 2009). These precursors signaled the 1985 eruption. On November 13, 1985, the Nevado del Ruiz volcano started with a small eruption at 3:06pm and two hours later pumice fragments and ash were showering down on Armero, the town 74 kilometers below. At 7:00pm the town started an evacuation and at 9:08pm molten rock began to erupt from the summit for the first time, previous eruptions were only steam explosions (SDSU, 2006). The eruption also generated deadly lahars that started at 11:35pm and moved downwards at speeds of 24 feet per second or 50 kilometers per hour (Suite101, 2009). The ice and snow on the summit of the volcano melted from the heat and sent large amounts of water and mud/materials picked up, speeding down the side towards Armero and hit within an hour.


Although Armero was 74 kilometers from the crater of Nevado del Ruiz, it took only two and a half hours for the lahars to reach to village, after the eruption began. The town of Armero was nearly destroyed. Over 23, 000 people died directly from the lahars and molten rocks that were thrown from the volcano during eruption. Many people later died because of smoke inhalation and starvation, etc. (Scribd, 2010). Approximately 15, 000 animals died and this eruption is said to be one of the ten deadliest eruptions in South American history.

Top Ten Key Points

·         The eruption was predicted. The government put out a report 3 months before warning people about the eruption, but people did not think it was urgent.
·        The eruption of Nevado Del Ruiz in 1985 was only a VEI-3, but was the worst lahar incidents in recorded history. (Wikipedia)
·         There were warning signs 51 weeks prior to the eruption, but Columbia had no equipment to monitor the volcano. The properly skilled geologists came from other countries. (SDSU, 2006)
·         Precursors began in November of 1984. There were small earthquakes, fumaroles (spew gas and steam), small magma eruptions, tremors, and large ejections of ash from the peak of the volcano.  (Suite101,2009 and SDSU, 2006)
·         Two hours after the eruption began, a lahar traveling 50 kilometres per hour hit Armero. In a few minutes nearly the entire town was swept away or buried. Chinchina was also hit, killing 1,927 people. (SDSU, 2006)
·         Dispite the Armero tragedy, the volcano’s lahars continues to pose a threat to many nearby town. Up to 500,000 people could be at risk. (Wikipedia)
·         Later there was a violent ejection of molten rock, which generated pyroclastic flows. A storm blocked most citizens view so they were not able to tell there was a pyroclastic eruption. (SDSU, 2006)
·         About 23,000 people were killed as well as 15,000 animals. 4500 people were injured and 8,000 people were homeless. The estimated cost is $1,000,000,000. (SDSU, 2006)
·         The eruption caused a mass ejection of sulphur dioxide that was about 700,000 tonnes, or about 2% of the mass of the solid material erupted. (Wikipedia)
·         Nevado Del Ruiz commonly produces Plinian eruptions, which generate pyroclastic flows, and massive lahars. (Wikipedia)
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