The 1985 eruption of Nevado del Ruiz volcano in Colombia caused lahars (volcanic mudflows and debris flows) that buried the town of Armero, killing approximately 23,000 people. The disaster was exacerbated by a lack of adequate warning and preparedness from the Colombian government, despite warnings from foreign scientists. In the aftermath, the government established new disaster response and evacuation plans, as well as public education programs about volcanic hazards to help prevent future devastation from eruptions of Nevado del Ruiz.

1. Nevado Del Ruiz
November 13th 1985
Estimated 23,000 dead (BBC News)

2. 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.

3. 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.

4. Location Continued
• 129Km west of the
capital city – Bogota
• The town of Amero
stood at the foot of
the volcano.

5. The Eruption

6. • 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.

7. • 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.

8. Causes of the Disaster

9. 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

10. • 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.

11. 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.

12. Primary Effects

13. • 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.

14. • 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.

15. Secondary Effects

16. • 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.

17. • 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.

18. Preparation for the eruption

19. • 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.

20. 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.

21. Responses
Short Term

22. • 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.

23. Responses
Long Term

24. • 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

25. • 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)