The eruption of Nevado del Ruiz

The eruption of Nevado del Ruiz

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Nevado del Ruiz, the highest active volcano in the Andes Mountains of Colombia, suffers a mild eruption that generates a series of lava flows and surges over the volcano’s broad ice-covered summit. Flowing mixtures of water, ice, pumice and other rock debris poured off the summit and sides of the volcano, forming “lahars” that flooded into the river valleys surrounding Ruiz. The lahars joined normal river channels, and massive flooding and mudslides was exacerbated by heavy rain. Within four hours of the eruption, the lahars traveled over 60 miles, killing more than 23,000 people, injuring over 5,000, and destroying more than 5,000 homes. Hardest hit was the town of Armero, where three quarters of the 28,700 inhabitants died.

The volcano first began showing signs of an imminent eruption a full year before, and most of the river valley’s residents would have survived had they have moved to higher ground.

READ MORE: The Deadliest Volcanic Eruption in History

Which was the costliest volcanic eruption in history?

With the recent eruption of Indonesia's Mount Sinabung comes a reminder that volcanoes still present a deadly risk in many parts of the world.

Several people died as villages were burned, farmland destroyed and ash clouds threatened to cause damage to surrounding areas.

While naturally the primary concern is saving lives, the economic damage this geological activity causes is thought to amount to billions of dollars a year.

Is it possible to determine the economic cost?

Direct costs include damage to infrastructure and homes, while indirect costs can include disruption to industry and transport.

The International Disaster Database lists the most expensive volcanic eruption as Nevado Del Ruiz in Colombia, which killed around 20,000 people when a mudslide hit the nearby town of Armero. The economic impact of the eruption is estimated at 1 billion dollars.

The 1980 Mount St Helens eruption in Washington State in America cost $860 million. The column of smoke and gas reached 15 miles into the atmosphere, depositing ash across a dozen states.

The most expensive eruption in recent years, Calbuco in Chile, is third on the list, at $600 million. Thousands of homes had to be evacuated and the agricultural and tourism industries in Chile suffered severe damage.

inevitably, placing an exact cost on such large events is difficult and some estimates vary. Allianz estimates the most expensive volcanic eruption to be the Sidoarjo Mud Volcano in Indonesia it was triggered during a gas drilling operation. Toxic volcanic mud has now been coming out of the ground for 10 years, and Allianz puts the total cost so far at $3 billion.

Although seismologists do not believe volcanic activity is increasing, inevitably the costs of such events grow as countries become more developed and their populations increase.

The most devastating incident, in terms of loss of human life, is believed to be the eruption of Tambora in Indonesia in 1815. While it's difficult to quantify the economic cost of historical disasters in the same way as those in the modern era, 92,000 people are thought to have starved to death in the months following the eruption, due to destroyed food supplies and farmland.

How do volcanoes compare with other natural disasters?

The United Nations has assessed the economic damage caused by all types of natural disasters between 1995 and 2015.

It found that geophysical disasters (volcanoes and earthquakes) cost $763 billion. Of these, 20% were volcanic, which puts the cost of volcanic activity at $152.6 billion over 20 years (or an average of $7.6 billion a year).

Quaternary eruptive history of Nevado del Ruiz (Colombia)

Nevado del Ruiz has a 1.8-m.y.-long eruptive record that includes alternate construction and destruction of three edifices during three main eruptive periods, termed “ancestral Ruiz”, “older Ruiz” and “Ruiz”. Nevado del Ruiz is located on a complex intersection of four groups of faults, the most significant being the N20° E Palestina strike-slip fault and the N50° W Villamaria-Termales normal fault.

Ancestral Ruiz was a broad stratovolcano built by two eruptive stages of lava flows starting about 1.8 Ma ago and ending 1.0 Ma ago. A partial collapse and formation of a caldera are thought to have occurred between 1.0 and 0.8 Ma ago.

Older Ruiz was a stratovolcano constructed by lava flows in three stages starting about 0.8 Ma ago and ending about 0.2 Ma ago. Extensive and voluminous welded and nonwelded pyroclastic-flow deposits that partly fill preexisting valleys record the formation of a young summit caldera between 0.2 and 0.15 Ma ago.

Present Ruiz is formed by a cluster of composite lava domes that probably filled the summit caldera of older Ruiz. Present Ruiz eruptive activity is mostly explosive, but also includes dome growth, and parasitic dome activity of La Olleta and Alto La Piramide.

Twelve eruptive stages occurred during the last 11,000 years, accompanied by rockslide-debris avalanches, pyroclastic flows or surges, and their subsequent interactions with the ice cap, as well as by glacial erosion and mass-wasting. Diverse processes within these twelve stages have led to a partial destruction of the summit domes. This long and complex Pleistocene and Holocene eruptive sequence helps to put the November 13, 1985, eruption into a broader perspective.

The Eruption of Nevado Del Ruiz Volcano Colombia, South America, November 13, 1985 (1991)


Experience with disasters has long been recognized as an important factor that can influence what people&mdashas individuals and in groups&mdashperceive future risk to be, as well as what they do to mitigate and prepare for future events. Prior to the November 13, 1985 eruption of Nevado del Ruiz, however, recent history did not provide the people of Colombia with experiences to point out the dangers of the Ruiz volcano.

It has been estimated that some ten major eruptions of the Ruiz volcano have taken place during the past 10,000 years, occurring on an average interval of 160 to 400 years (Herd, 1986). The last major volcanic event at Ruiz was in 1595. In 1845, an earthquake, phreatic eruption (Herd, 1986), or avalanche (UNDRO, 1985) caused a giant mudflow that killed 1,000 people as it traveled 86 km down the Lagunillas River to the Magdalena River. This 1845 lahar traversed the current site of Armero (Acosta, 1850). Two significant earthquakes occurred in 1826 and 1827. Finally, in 1916, a more minor event resulted in ashfall in the city of Manizales in Caldas State. The volcano has remained virtually dormant since then.

The relatively minor eruptive events at Ruiz since 1595 and the lack of events of sufficient magnitude (from a social perspective) to illustrate lahar risk since 1845 did little to convince those at risk that volcanoes are a major and significant Colombian natural hazard.

This is illustrated by a 1985 Colombian Civil Defense publication, What to do in Case of Disaster. The booklet, which was prepared for public distribution, describes about a dozen hazards along with suggested protective public actions volcanic hazard is not mentioned.

Pointing up this oversight is in no way an attempt to single out the

people of Colombia for criticism. Few are able to recognize a hazard that, for all practical purposes, has not manifested itself for some 140 years. This lack of local experience with volcanic hazards, and, thus, the virtual absence of volcano risk perception among the Ruiz area residents, was likely a major obstacle faced by those scientists and officials who recognized the danger, engaged in preparedness for an emergency, and sought to ready the public to respond.


The ability to predict the precise time and magnitude of a natural disaster depends on two factors: the current state of scientific knowledge about a particular disaster and local observations of precursor activities to the disaster. The earliest perception of threat associated with Ruiz was in December 1984. A landslide formed a dangerous natural dam. At about the same time, mountain climbers began to feel and report earthquakes and gas plumes. These activities persisted, and in February 1985 several geologists from INGEOMINAS (the National Institute of Geology and Mines) conducted a site visit. In March 1985, the Colombian Civil Defense (Defensa Civil de Colombia) and INGEOMINAS requested that the United Nations Disaster Relief Organization (UNDRO) send a scientist to study the volcano.

John Tomblin of UNDRO inspected Ruiz in March 1985. Tomblin concluded that the observed earthquakes and gas plumes could be indicative of an eruption and he recommended that INGEOMINAS install seismographs to monitor the volcano. In addition, he suggested that a risk map be prepared to illustrate the potential hazard associated with an eruption of the volcano. Further, he recommended that the Defensa Civil de Colombia draft an emergency plan to facilitate public warnings and evacuation for high-risk areas.

Thus, INGEOMINAS began a project to monitor and define the volcanic risk in the Ruiz vicinity. In May, UNDRO funded a reevaluation of Ruiz by Minard Hall of the Instituto Geofísico of the Escuela Politécnica Nacional of Ecuador. In May 1985, the U.S. Geological Survey initiated a cooperative effort with UNDRO to provide scientific equipment to monitor Ruiz. First steps began in July 1985 when four portable seismographs were installed on the mountain. At about the same time, the Ruiz Volcanic Risk Committee was formed. Its charge was to begin volcanic monitoring, local emergency planning, and public education about volcanic risk.

In August, the installed seismographs recorded 5-20 earthquakes each day (Herd, 1986). INGEOMINAS pointed out that, on average, such earthquakes have, on a global basis, accompanied large volcanic eruptions about 25 percent of the time throughout recorded history. A minor eruption of steam, ash, and rock occurred on September 11, 1985 this event captured government attention although no one was injured. Surveillance of the volcano contin-

ued, and by October more seismographs and tiltmeters were installed on Ruiz. On November 12, 1985, the day prior to the major eruption of Ruiz, geologists who climbed to the summit to collect gas samples observed no clear signs of an imminent explosion.


A variety of efforts were undertaken to increase awareness of the risk presented by Nevado del Ruiz subsequent to the scientific discovery of an impending eruption and prior to the November 13, 1985 event. These efforts involved many Colombian and other organizations.

Instituto Nacional de Investigaciones Geológico-Mineras (INGEOMINAS)

In August 1985, INGEOMINAS published the first of a variety of reports designed to organize for or further the understanding of volcanic risk in response to the Ruiz threat. The first of these reports, Riesgos Sísmicos y Volcánicos Del Parque Natural De Los Nevados (Seismic and Volcanic Risks of Los Nevados Natural Park), was an effort to report on recommended research and monitoring on six Colombian volcanoes and the areas around them. The research agenda proposed recognized the volcanic risk in Colombia, particularly in volcanic regions where people lived close by. The report requested a budget to perform the recommended studies and recognized the inevitable involvement of international scientists in the study of Ruiz.

The proposed project was designed to be undertaken in stages, and it recognized the need for additional funds and international assistance. It also pointed to the need to involve organizations at all levels of Colombian government&mdashincluding local governments&mdashto define risk and hazard. The preliminary request sought funding to prepare a volcanic risk map for Ruiz it was recognized that such a map would be needed to help make good hazard preparedness decisions.

A preliminary version of the risk map was completed on October 7, 1985, and it was accompanied by an explanatory report entitled Mapa Preliminar De Riesgos Volcánicos Potenciales Del Nevado Del Ruiz (Preliminary Map of Potential Volcanic Risks Associated with Nevado del Ruiz). An additional report accompanied the preparation of the risk map. This report, entitled Informe Preliminar De Las Actividades Desarrolladas Período Julio 20-Octubre 7 de 1985, explained that Ruiz was in a stage of activity but that it could not be precisely predicted when an eruption would occur. Continued volcanic activity was reported along with minor ashfall, de-icing of the mountain top, small mudflows, and increased volcanic crater size. The

Nevado del Ruiz Volcanic Eruption – Colombia – November 13, 1985

On November 13, 1985, Colombia’s Nevado del Ruiz, South America’s most northerly active volcano, erupted close to midnight. Pyroclastic flows melted ice and snow at the 17,500-foot summit, forming mudflows that rushed down several river valleys. These mudflows, known locally as lahars, were as thick as 150 feet and they traveled at more than 65 mph, devastating houses and towns in their paths. The town of Armero, fifty miles from Colombia’s capital, Bogota, was completely covered by them, killing 21,000 of its population of 28,700. In all there were 23,000 deaths, 5,000 injuries, and the destruction of more than 5,000 homes.

There were hundreds of instances where people that were only a few feet apart were either killed or survived the massive mudflows. Among the terrible consequences for some survivors was that the high temperature of the mudflows had made them collectors of all kinds of pathogenic fungi and bacteria. Some survivors who had minor cuts were killed by the infections because they could not be treated with known antibiotics. The villagers had been warned of the impending disaster but, because of false information that had been circulating about it for some time, these warnings were ignored. The first sign of activity occurred in the afternoon of November 13 and local officials immediately ordered a general evacuation but then cancelled it within a couple of hours when the mountain became quiescent.

Nevado del Ruiz is an active volcano with a history of generating deadly volcanic mudflows from relatively small-volume eruptions. In 1595, a lahar swept down the valleys of the River Guali and the River Lagunillas, killing 636 people. In 1845, an immense lahar flooded the upper valley of the River Lagunillas, killing over 1,000 people. It continued for forty-five miles downstream before spreading across a plain in the lower valley floor. The young village of Armero was built directly on top of the 1845 mudflow deposit. Over the ensuing years, Armero grew into a vibrant town with over 27,000 residents. On November 13, 1985, history repeated itself for the third time in four hundred years, with another eruption and another deadly lahar racing down the River Lagunillas.

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. Several years later, the scarred sides of the creeks along which the lahar flowed were clearly visible from commercial aircraft. Even in the mid-1990s the town was covered with up to twenty feet of ash and debris. Local villagers harvested stones for building work. A few small trees were trying to grow, protected from wandering animals by makeshift fences. The eruption cost Colombia 7.7 billion dollars about 20 percent of the country’s GNP for the year in question. Following the 1985 eruption, Nevado del Ruiz remained active for several more years, culminating in smaller eruptions in 1991 and 1992, well below the VEI of 3 that defined the 1985 eruption.

Ultimately, this was a tragedy that could have been averted. Nevado del Ruiz had served up a steady menu of minor earthquakes and steam eruptions for fifty-one weeks prior to the November 13 eruption. The on- going activity was just enough to keep people nervous, but not enough to convince authorities that the volcano provided a real threat to the communities surrounding the volcano. Since Colombia had no equipment to monitor the volcano, or geologists skilled in using such equipment, expertise could only come from other countries. A scientific commission and some journalists visited the crater in late February and soon after a report of the volcanic activity first appeared in the newspaper La Patria in early March.

By July, seismographs were obtained from several countries that would help in plotting the movement of rising magma beneath the volcano. Money was obtained from the Unified Nations to help map the areas that were thought to be at the greatest risk. The resulting report and volcanic hazards map were finished on October 7, but only ten copies were distributed. Based on the report, the National Bureau of Geology and Mines declared that a moderate eruption would produce a percent hundred percent probability of mudflows with the greatest danger for Armero.

The eruption of Nevado del Ruiz - HISTORY

The May 18, 1980, eruption of Mount St. Helens was exceeded in "size" by many other eruptions, both in historic times and in the recent geologic past.

For the study of earthquakes, two standard measures of the "size" of the seismic event are commonly used: the Richter Magnitude Scale (based on energy released as measured by seismometers) and the Modified Mercalli Intensity Scale (based on damage caused as assessed by people). Although some attempts have been made to develop a scale to compare the relative sizes of volcanic eruptions, none has yet been adopted for general use. Volcanologists have proposed and used various schemes to rank eruptions, and these generally included one or more of the following factors--height of eruption column, volume of material erupted, distance and height of hurled blocks and fragments, amount of aerosols injected into the upper atmosphere, and duration of eruption. All these factors relate directly or indirectly to the total amount of energy released during the eruption. Perhaps the two most commonly used and directly measurable factors are eruption volume and height of the eruption column.

The May 18 eruption ejected about 0.3 cubic mile of uncompacted ash, not counting an unknown but probably much smaller amount that was deposited in the atmosphere or too diffuse to form measurable deposits. This volume of ash is less than those of several earlier eruptions of Mount St. Helens and considerably less than the ejecta volumes of some historic eruptions elsewhere. The 1815 eruption of Tambora (Sumbawa, Indonesia) ejected about 30 to 80 times more ash than did Mount St. Helens in 1980. The 1815 Tambora eruption ranks as the largest known explosive eruption in historic times. But even the Tambora eruption pales by comparison with the gigantic pyroclastic eruptions from volcanic systems such as Long Valley Caldera (California), Valles Caldera (New Mexico), and Yellowstone Caldera (Wyoming)--which, within about the last million years, produced ejecta volumes as much as 100 times greater.

Ejecta volume, in cubic miles

Some scientists recently proposed the Volcanic Explosivity Index (VEI) to attempt to standardize the assignment of the size of an explosive eruption, using ejecta volume as well as the other criteria mentioned earlier. The VEI scale ranges from 0 to 8. A VEI of 0 denotes a nonexplosive eruption, regardless of volume of erupted products. Eruptions designated a VEI of 5 or higher are considered "very large" explosive events, which occur worldwide only on an average of about once every 2 decades. The May 1980 eruption of Mount St. Helens rated a VEI of 5, but just barely its lateral blast was powerful, but its output of magma was rather small. The VEI has been determined for more than 5,000 eruptions in the last 10,000 years. None of these eruptions rates the maximum VEI of 8. For example, the eruption of Vesuvius Volcano in A.D. 79, which destroyed Pompeii and Herculaneum, only rates a VEI of 5. Since A.D. 1500, only 21 eruptions with VEI 5 or greater have occurred: one VEI 7 (the 1815 Tambora eruption), four of VEI 6 (including Krakatau in 1883), and sixteen of VEI 5 (counting Mount St. Helens in 1989 and El Chichon, Mexico in 1982). Considered barely "very large," the eruption of Mount St. Helens in May 1980 was smaller than most other "very large" eruptions within the past 10,000 years and much smaller than the enormous caldera-forming eruptions--which would rate VEl's of 8--that took place earlier than 10,000 years ago.

The number of casualties and extent of destruction also have been used to compare the "bigness" of volcanic eruptions. For obvious reasons, such comparisons are limited at best and misleading at worst. Some of the most destructive eruptions have not been in other terms "very large." For example, mudflows triggered by the November 1985 eruption of Nevado del Ruiz (Colombia) killed more than 25,000 people--resulting in the worst volcanic disaster in the 20th century since the catastrophe at Mont Pelee in 1902. Yet, the eruption was very small, producing only about 3 percent of the volume of ash ejected during the May 1980 eruption of Mount St. Helens. As the table below clearly shows, of the seven greatest volcanic disasters in terms of casualties since A.D. 1500, only two of them (Tambora and Krakatau) qualify as "very large" eruptions (VEl's greater than 5) in terms of their explosive force.

The May 1980 eruption of Mount St. Helens has a higher VEI (5) than five of the deadliest eruptions in the history of mankind, but it resulted in the loss of far fewer lives (57). Loss of life would have been much greater if a hazard warning had not been issued and a zone of restricted access had not been established.

Tag: Nevado del Ruiz

Omayra Sánchez Garzón was a little girl on this day in 1985, a typical thirteen-year-old and one among many, living in Armero. There is not enough meanness in all the world, to wish on anyone what this one little girl would endure for the next three days.

Fifty miles from the Colombian capital of Bogotá, the municipality of Armero was once home to 30,000 souls. Long known as “Colombia’s White City”, Armero was at one time a major cotton producer, seat of the prosperous agricultural region located in the northern Tolima Department, of Colombia.

Today, the place is a ghost town.

the “Armero Tragedy’, before and after

Some forty miles from Armero, the Nevado del Ruiz Stratovolcano in the Central Andes, is the site of three major eruptive periods since the early Pleistocene era. The present volcanic cone formed some 150,000 years ago during the present eruptive period. Known to locals as the “Sleeping Lion”, Nevado del Ruiz had not experienced a major eruption, since 1845. 140 years later, it was hard to imagine the thing presented much of a threat.

The eruption of November 13, 1985 was small by volcanic standards. For its unsuspecting victims, it was a distinction without a difference. Much as the ant may fail to notice. He was crushed by a very small elephant.

Nevado del Ruiz Stratovolcano

The eruption of Mount Vesuvius in 79AD was later described in a letter written by Pliny the Younger, describing the catastrophe that killed the philosopher’s uncle. The “Plinian Eruption” which killed the Roman author and naturalist Pliny the Elder would be repeated half a world away and some 2,000 years later, as a sleeping lion came to life.

The fast moving clouds of gas and volcanic material came in the dead of night, the “pyroclastic flow” super-heated to 1,000° Fahrenheit and racing away from the cone at speeds as high as 430 miles-per-hour. Next came the Lahars, the violent and terrifying mud flow of pyroclastic material, rocky debris and vast quantities of water released by the near-instantaneous melting of the Nevado del Ruiz glacier. Imagine a wall of rocky mud coming at you at 22mph, only a little slower than Jamaican sprinter Usain Bolt’s best 100-meter dash. Usain Bolt just happens to be the fastest man who ever lived.

Mount Merapi Lahar, Central Java

Lahars flow at depths as great as 460-feet. Vast, hideous walls of mud, rock and debris the consistency of wet concrete, speeding down rivers and valleys. The first of three lahars and the most powerful of that night wiped fourteen towns and villages from the face of the earth, killing as many as 20,000 in Armero, alone.

Galungung Lahar, Indonesia

Omayra Sánchez Garzón was a little girl on this day in 1985, a typical thirteen-year-old and one among many, living in Armero. There is not enough meanness in all the world, to wish on anyone what this one little girl would endure for the next three days.

Many years ago, I found myself pinned under a car while working on the engine. The motor and transmission assembly, free of its mount, swung down and pinned my hand underneath. It obviously hurt but, more than that, there was the strangest feeling of being…trapped. Permanently pinned in place like an insect in a child’s science project, entirely denied the power of voluntary movement. It may as well have been a locomotive, sitting there on my fingers.

Omayra Sánchez suffered her legs to be so trapped, pinned under the collapsed stony structure of her own home, legs entangled in the dead arms of her aunt and submerged up to her neck, in water.

The nation of Colombia was a basket case at this time, engaged in a fight for its life with Leftist guerrilla organizations such as the M-19 Democratic Alliance (19th of April Movement), and the FARC. The Palace of Justice siege of less than a week earlier resulted in the murder of fully half the 25-member Colombian Supreme Court, as the Colombian military mobilized across the capital city of Bogotá.

Rescue efforts on the ground in Armero were frantic, disorganized and mostly local. Official government assistance was all but, non-existent, pumps altogether unavailable. Soon even supplies of simple hand tools such as stretchers, shovels and cutting tools, began to give out. Foreign aid rushed in from nations from around the world but, for most victims, such well-intended help arrived, too late..

After the lahar passed, Sánchez found herself buried in rubble. She managed to get one hand out of the wreckage as rescuers desperately worked to clear the wood, stone and debris from her upper body. As the water rose, a tire was placed around her body to keep her from drowning. Divers attempted to free her legs, but without success. She was trapped. Bilateral amputation was considered but there were no means, even to remove the water. In the end, doctors determined the most humane course was to comfort this child as much as humanly possible, and let her die.

Colombian Ambassador to Portugal Germán Santa María Barragán was at that time a journalist and volunteer in the Armero rescue. Barragán was with Omayra for much of her last three days. Sánchez herself remained relatively positive throughout the ordeal, sometimes asking for sweets or soda, sometimes even singing to the journalist. Some times she cried and others, she prayed. Stuck there as she was she agreed to be interviewed, her face and her desperate plight quickly becoming known, around the world.

“Colombia and half of the world remained with the bitter sensation that Omayra Sánchez could have been able to continue living after remaining for almost 60 hours trapped from head to toe amidst the rubble of Armero. Her face, her words, and her courage, which streamed throughout the world on television and were a heartbreaking image in the largest newspapers and magazines of the United States and Europe, remained a testimony of accusation against those who could have at the very least made the tragedy less serious. – Germán Santa María Barragán in El Tiempo, November 23, 1985

The color of her hands make it appear, as Sánchez is wearing gloves. She isn’t.

French photographer Frank Fournier arrived at dawn on the 16th. Omayra Sánchez had been in the water for nearly three days and nights by this time. She was all but abandoned when Fournier first saw her, the whole place eerily silent, save for the occasional scream.

Fournier received vehement backlash for his pictures. How could he do that, just taking pictures like that, without trying to help. What are you, some kind of ghoul? A “vulture”!? Fournier himself had no means to help this girl, save to use his skill and his camera, to bring her story to the world. He was a photographer.

In her final hours, Sánchez began to hallucinate. She asked the photographer to bring her to school. She didn’t want to miss her lessons. She had a math exam. At one point she even told her rescuers, to go get some rest.

Omayra Sánchez was trapped for sixty hours with only head and shoulders above water, caught in a kneeling position and pinned under massive and impenetrable piles of bricks and masonry. Her eyes reddened toward the end as her face swelled and her usually brown hands turned from pale, to white.

Two years later, the world held its breath for fifty-eight hours as scores of frantic volunteers worked ’round the clock, to free Baby Jessica from a West Texas well. Omayra Sánchez waited sixty hours for a rescue, that never arrived.

Red Cross workers desperately appealed to the Colombian government for a pump, and for help in freeing the trapped girl. In the end there was no alternative but to stay by her side, and pray. She died at 10:05am local time, from a combination of gangrene and hypothermia. Three hours after Fournier took the picture above.

In time, the water subsided. Those left alive moved away, to Bogotá or to Cali or a few kilometers north to the new town of Armero-Guayabal. Armero itself is a dead place now, save for a few memorials marking important places such as hospitals, parks, and theaters. And a small shrine, dedicated to one little girl.

Little was left of Omayra’s family. Her father was killed in the collapse. Her aunt was dead. Two-thirds of the town in which she had spent her short life, were gone. 85% of Armero itself, had ceased to exist. From that day to this, the once prosperous “White City” of Colombia, remains a ghost town.

Omayra’s brother survived the disaster, with only the loss of a single digit. Her mother expressed the forlorn anguish only the parent of a dead child, will ever experience: “It is horrible, but we have to think about the living … I will live for my son, who only lost a finger.”

November 13, 1985: The Nevado del Ruiz Lahars

The eruption started at 15:00 o'clock local time November 13, 1985 with smaller explosions in the crater. Ash was carried by the wind in north-eastern direction, however only minor ash fall occurred in the city of Armero (Colombia), located 48 kilometers east of the "Cumanday" - the smoking nose, as the Indians used to call the volcano.

In the evening the intensity of the eruption increased, however it was still considered only a medium sized event for the Nevado del Ruiz. At 23:00 most of the 25.000 inhabitants of Armero were sleeping, despite some preoccupation for the sounds coming from the distant mountain, then suddenly - as an eyewitness describes - "the world screamed."

The underground was trembling and a terrible roar followed. A mixture of water and debris overwhelmed the entire city. In 20 to 30 minutes three or four lahars (mudflows of volcanic material) occurred. Some survivors later reported that the first waves were formed by cold mud, followed by waves of hot mud. Nearly 22.000 people were killed by these mudflows that coming from the summit of the volcano followed the river valley of Lagunillas until reaching Armero.

Video 1. Video produced by the World Health Organization to document the aftermath and rescue operations at Armero (the video shows victims and injured people - viewers discretion is advised).

The volcanic nature of the Nevado del Ruiz (5.389m) was already known in ancient times as the indigenous name reveals. The volcano erupted in historic times in the years 1595 and 1845 and already during this last eruption a mudflow killed 1.000 people in the Lagunillas valley.

Before 1985 the presence of vapour on the mountain summit was noted and a small glacial lake filled the bottom of the crater. In November 1984 an intense earthquake activity started, probably marking the slow rise of magma inside the volcano. In the last year, between December 1984 and September 1985, the volcanic activity steadily increased. The relatively small eruption from November 1985 melted partially the glaciers covering the Nevado del Ruiz (estimated 10% of the ice-area), forming the lahars that had such disastrous effects in the valleys surrounding the volcano.

After the catastrophe an intense debate about responsibility began, the compiled hazard map (one of the first in Colombia) of the entire area got widely ignored and misinterpreted, as were the signals of activity by the volcano. The authorities were informed previously that Armero was located on the deposits of the lahar of 1845 and a similar disaster could occur again even by minor eruption. After the disaster the government of Colombia created a special program to prevent such incidents in the future.

DECKER, R. & DECKER, B. (1991): Mountains of Fire: The Nature of Volcanoes. Cambridge University Press. Cambridge: 243

The views expressed are those of the author(s) and are not necessarily those of Scientific American.


My name is David Bressan and I'm a freelance geologist working mainly in the Austroalpine crystalline rocks and the South Alpine Palaeozoic and Mesozoic cover-sediments in the Eastern Alps. I graduated with a project on Rock Glaciers dynamics and hydrology, this phase left a special interest for quaternary deposits and modern glacial environments. During my research on glaciers, studying old maps, photography and reports on the former extent of these features, I became interested in history, especially the development of geomorphologic and geological concepts by naturalists and geologists. Living in one of the key area for the history of geology, I combine field trips with the historic research done in these regions, accompanied by historic maps and depictions. I discuss broadly also general geological concepts, especially in glaciology, seismology, volcanology, palaeontology and the relationship of society and geology.

7. Mount Tambora (1815)

Tambora’s eruption in 1815 holds the record for being the most destructive and deadliest in recorded human history. Located once again in Indonesia, its explosion disrupted the global climate so much that 1816 was dubbed the “year without summer.”

This caused a chain of events leading to crop failure and deaths of livestock. The resulting famine was the worst one recorded in the 19th century—this, combined with the eruption itself, caused around 92,000 deaths.

All these demonstrate that Mother Earth is as beautiful as she is frightening.

Nevado del Ruiz Volcanic Eruption of 1985

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.

Watch the video: Volcanoes Daily. 7421 - Increased Activity - Big Eruptions at Nevado Del Ruiz u0026 Sangay