1. LEDC Volcanic Eruption Case Study Nevado Del Ruiz, Colombia - 1985

2. Background Nevado Del Ruiz is an active stratovolcano located in Colombia. The volcano lies on the Andean Volcanic Belt which is produced by the subduction of the Nazca plate beneath the South American continental plate. The volcano has been active for 150,000 years – the eruption in 1985 is the most recent after being dormant for 69 years.

3. Eruption A rise in seismic activity was first noticed in late 1984, and by September 1985 people were warned an eruption was likely, with a very high risk of lahars. The main eruption occurred on 13 th November 1985, producing pyroclastic flows that melted glaciers and snow. Lahars formed of water, ice, volcanic rock and clay were created, and flowed down the river valleys at speeds of 60kph, growing to around four times their original size. The lahars reached the city of Armero around 2 hours after the eruption. The eruption was relatively small, measuring 3 on the VEI.

5. Impacts The lahars that hit the town of Armero killed three quarters of the 28,700 inhabitants. They lasted approximately two hours, burying 85% of the town in mud. Another lahar killed 1800 people and destroyed 400 homes in the town of Chinchina. Hundreds of people died from infections after the disaster, and many survivors faced concerns of disease such as yellow fever caused by mud getting into wounds. The loss of life was exacerbated by the unpreparedness of local people – although warnings were put in place, many people did not receive them or could not understand them, and the Colombian government accused scientists of scaremongering.

7. Response and Management An international aid effort was set up to respond to the disaster, with the US government spending $1 million in aid. Rescue workers and medical supplies were sent to the area, although rescue efforts were made difficult by collapsed bridges, and thick, soft mud.. The eruption occurred at the same time as the 1985 Mexico City earthquake, meaning the numbers of people available to help was limited. At the time there was guerrilla warfare in the capital city, so the army and government were not available.