Nevado Del Ruiz November 13, 1985

LEDC VOLCANIC ERUPTION/ LAHARS- CASE STUDY

Location• Colombia• Located on the border of the

departments (provinces) of Caldas and Tolima in Colombia

• Part of the Andes Mountain Range • 129 km west of the capital

city Bogotá• Overshadowed the town of

Armero• Part of Los Nevados National

Natural Park• The current volcanic cone formed

during the "present" eruptive period, which began 150 thousand years ago.

Location continued

• Nevado Del Ruiz is part of the Ruiz–Tolima volcanic massif (Cordillera Central)

• The massif is located at the intersection of four faults - some of which still are active

• Nevado del Ruiz lies within the Pacific Ring of Fire

• Part of the Andean Volcanic Belt

Geology• It is a stratovolcano composed of many layers

of lava alternating with hardened volcanic ash and other pyroclastic rocks

• Nevado del Ruiz has been active for about two million years

• 5400 m with 30 m ice cap on top• The Nevado del Ruiz usually generates Plinian

eruptions• The Andean Volcanic Belt is produced by the

eastward subduction of the oceanic Nazca Plate beneath the SA continental plate

Physical Causes

• Had previously not erupted for over 100 years- Built up Pressure

• Lahars were caused by the sudden melting of the ice cap by hot pyroclastic material

• This providing the volcanic material with a medium with which to travel down the slope

• The pyroclastic flow and water from the mountain caused the Lahars

Human Causes• Towns and cities such as Armero and

Mariquita were built in valleys as they are easiest for construction

• The lahars followed river valleys as they are the easiest path to go down due to gravity

• The Colombian government did not act quick enough and evacuate the Settlements at risk

• The Volcano gave enough warning as it erupted multiple times on a small scale previous to the main eruption

Effects• Eruption was relatively small• Lahars killed 70% of Armero (22000 people) 45 km

away• lahars were as much as 40 meters thick and traveled

at velocities as fast as 50 kilometers per hour• Most were killed by suffocation as lahars up to 8m

buried them• Lahars killed 1800 people in Chinchina• 3400 ha of agricultural land is lost in the eruption• Virtually all roads , communications and poer

supplies are destroyed within the affected area

Lahar and Pyroclastic Map

Effects Continued

• Hot pyroclastic flows and surges caused rapid melting of the snow and ice, and created large volumes of water that swept down canyons leading away from the summit

• As floods of water descended the volcano, they picked up loose debris and soil from the canyon floors and walls, growing both in volume and density forming hot lahars

Effects Continued• The region was isolated• 50 schools, 2 hospitals, 58 industrial plants

and 343 commercial establishments were damaged or destroyed

• The cost for the Colombian economy was immense $7.7 billion which was 20 percent of GDP for 1985

• Equivalent to the UK spending 450 billion on natural hazard

Local Effects• Clean water, in short supply due to damage to

water systems• There was an initial concern about possible

threats to the emergency operations from guerrilla groups active in the Colombian countryside

• The mudflows affected many km2 - survivors were scattered over a wide area

• mobility in the valley was hampered by the impassable mud deposits

• Aircraft, primarily helicopters, thus became the main method of search and rescue

Hazard Map

Response – Short Term• The Colombian Red Cross and Civil Defense

personnel were the principal first responders to Armero, participating in and organizing rescue 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

Short Term Response

• Early on in the emergency 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 the international disaster relief community, and the individual efforts of over 30 foreign countries

Response - Long Term• In the wake of the Armero 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 topical 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

Long Term Response• A public education campaign was also under

way in early 1986• 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 hazard, with information on evacuation warning systems such as sirens

Long Term Response

• Hazard maps in the form of posters were distributed for towns at risk to illustrate appropriate protective action in response to hearing sirens such as to evacuate to high ground

• Evacuation route markers were painted on buildings in towns at risk to illustrate proper egress from danger areas if sirens were heard

Links

• http://www.nap.edu/openbook.php?record_id=1784&page=65

• http://vulcan.wr.usgs.gov/Volcanoes/Colombia/Ruiz/description_eruption_lahar_1985.html