Nevado Del RuizNovember 13th 1985

Estimated 23,000 dead (BBC News)

Type of Volcano• Stratovolcano - meaning steep

sides, characterised by a ‘cone’ shape. These volcanos form due to particularly explosive eruptions with very viscous lava. The debri ends up miles away however the lava cannot travel very far before it cools, thus forming the steep, pointed shape.

Location• The volcano is located in the Andes mountain range, in its volcanic

belt, on the border between Caldas and Tomila in Columbia. • The volcano forms part of the Ruiz-Tomila massif(Cordillera Central)

which is on the cross road of four fault lines.• As well as this the volcano is in the ‘Ring of Fire’ which is a circle of

volcanos (mostly Stratovolcanos) that surround both the Pacific and Nazca plates. The Nazca plate is being subducted beneath the South American plate it borders onto.

Location Continued• 129Km west of the

capital city – Bogota• The town of Amero

stood at the foot of the volcano.

The Eruption

• After nearly a year of minor earthquakes and steam explosions from Nevado del Ruiz, the volcano exploded violently on November 13, 1985. The initial blast began at 3:06 p.m• The eruption creates pyroclastic flows that

melt the the glaciers and snow generating lahars that run down the valleys of the volcano.• The prescance of volcanic lakes accelerate

the melting of the glaciers.• At 11:30 the first wave of water hit Amero, it

was strong enough to tip cars.• Just afterwards the first lahar hit only to be

followed by others.

• The lahars were the most destructive part of the disaster:• They lasted a total of around two

hours.• They were up to 30metres deep.• They carried large debri that

crushed people and smaller debri that slashed into skin and gouged into limbs.• If submerged long enough the

sheer force of the lahars was enough to asphyxiate a person by stopping the blood flow in their body.

Causes of the Disaster

Physical Causes For The Extreme Effects• It had not erupted for over 100 years, which causes a build-up of pressure• A sudden melt of the ice cap by hot pyroclastic material caused lahars, this

provided the volcanic material with a path to travel down the slope• Lahars were also caused by pyroclastic flow and water from the mountains• The volcano sits on the boundary between the oceanic Nazca plate and the

continental South American plate – this is a convergent plate margin• As the volcano is on a convergent plate margin, the oceanic plate

submerged the continental plate, causing the continental plate to rise, resulting in the formation of the Nevado del Ruiz

• As the Nazca plate is subducted beneath the South American plate it begins to melt. This magma becomes lighter as it mixes with gases, water and soil from the surface. The magma rises forming a volcano. The pressure builds up until eventually the volcano erupts. The lahars were formed when the heat from the eruption melted glaciers on top of the volcano. The water from the glaciers mixes with volcanic debris and surges down the volcano.• A severe storm occoured at the same time as the eruption, potentially

stopping people from hearing the volcano, they simply stayed inside their houses as instructed.

Human Causes For The Extreme Effects• Towns and cities such as Armero and Mariquita were built in valleys as these were the

easiest places for construction• The lahars followed river valleys as this is the easiest path for them to go down due to

gravity• The Columbian government did not act quickly enough to evacuate the settlements at

risk, even though the volcano gave plenty of warning by several small eruptions prior to the main eruption• There were Hazard maps for the area but they were poorly distributed.• The population were generally undereducated about volcanoes and their possible

effects.• Contact with the local areas at the time of the eruption was difficult due to a severe

storm.

Primary Effects

• The eruption melted the glacier and created boiling hot lahars. These were up to 40 metres thick and travelled at up to 50km/h.• 70% of Amero was destroyed. (20K of 29K dead)• 3400Ha of agricultural land was destroyed • Most travel links, roads and tracks, destroyed and blocked.• 23000 people dead, 5000 injured.• The six major rivers around the volcano were polluted with the lahars

mud and volcanic substances, along with whatever they had picked up along the way.

• Soil was eroded and vegetation destroyed along the paths of the lahars.• An astronomical $1 Billion was spent trying to help the victims and

the area. Recovery efforts were thought to have cost equivalent to one fifth of Columbia’s 1985 gross national product. • 13 villages destroyed.• 23000 refugee survivors that were displaced due to the 110km² of

land destroyed.

Secondary Effects

• The destruction of the infrastructure and remaining mud from the lahars delayed the recovery operations and added to the death toll as many people with severe injuries died before they could be rescued. It was 12 hours before the first aid managed to get into Amero.• Pollution of the area in and around the volcano with large amounts of water and

mud.• The lahars mud and water meant that many people could be given no more help than

comfort as they died of hypothermia or gangrene. A famous example of this was Omayra Sánchez who was photographed by a media photographer as she slowly died. She could not be removed from the water as her legs were trapped by debri and her families bodies, the only escape would have been to remove her legs- which was not viable in the conditions. Her last few days was recorded by the media and influenced the political effects of the disaster.

• The guerrilla warfare between the government and insurgent forces was halted in respect for the disaster.• A great deal of the blame for the severity of the disaster was placed upon

the, already unpopular, Columbian government who had failed to prepare or see warning signs- dismissing scientists as fear-mongering. However at the same time the insurgent forces and the government had a major clash the day before the eruption which may have led to some of the incredibly lacking evacuation plans. Adversely this pressure and blame made the Columbian government begin to take action to plan for potential disasters in the future.• Amero was completely abandoned and no attempts to reconstruct were

made, only monuments to the victims were built on the site.

Preparation for the eruption

• The citizens of Amero remained calm as reassuring messages from the mayor over radio and from a local priest over the church public address system. • 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 – who the government refused to listen to.• The Red Cross ordered an evacuation of the town at 7:00 p.m. However,

shortly after the evacuation order the ash stopped falling and the evacuation was called off.• The background to this slide is the actual risk map presented to the

Columbian government.

When you compare the post-eruption map, to the map drawn up by the foreign scientists beforehand, you can see that they had predicted the disaster in almost exact detail to what happened.

It is unclear whether the Columbian government refused to listen on grounds of the knowledge being foreign or that they didn’t have the resources to prepare, however it is very clear that they were not listening to very obvious facts. Something was going to happen and it would be big, the foreigners were not fear-mongering.

Responses Short Term

• The Colombian Red Cross and civil defence personnel were the principle first responders to Amero, participating in and organizing recue and medical care.• The Colombian military also played an important role in the logistics

of the rescue activities by providing helicopter airlift for victims in need of medical care, distributing supplies and establishing field medical care and shelter facilities. • Early on in the emergency aid period, the Colombian president made

a request for international assistance and much aid was received.• After the first 24 hours, resources of all types began to arrive through

the joint efforts of international disaster relief community and individual efforts of over 30 foreign countries.

Responses Long Term

• In the wake of the Amero disaster, Colombia established a plan for the warning and evacuation of threatened areas in the event of another eruption of Nevado del Ruiz.• It outlined tropical planning areas such as:• Identification of hazard zones• Population and property census• Evacuation route identification• Rescue and medical aid• Security in evacuated areas• Alert procedures

• A public education programme was also underway in early 1896.• Schools educated students about volcanic hazards in general and

specifically what to do if Nevado del Ruiz erupted• Red Cross circulated thousands of flyers to the public about the volcanic

hazards with information on evacuation warning systems such as sirens.• Hazard maps in the form of posters were distributed for towns at risk to

illustrate appropriate protective action in response to hearing sirens to evacuate to high ground.• Evacuation route markers were painted on buildings in towns at risk.• They also created the Oficina Nacional para la Atención de

Desastres (National Office for Disaster Preparedness), now known as the Dirección de Prevención y Atención de Desastres (Directorate for Disaster Prevention and Preparedness)