warning system in place the night of the disaster failed to get word to the citizens of Armero, most of whom were in bed for the evening after ashfall and other volcanic events of the day were thought to have ceased. An estimated 5,000 people did survive and were displaced by the disaster.

The continuation of sporadic volcanic activity recorded since the November 13, 1985 eruption, combined with the extensive ice cap still remaining around the summit, could result in future lahars with equally devastating consequences for the large population still living in proximity to the volcano.

The study team characterized the magnitude and extent of the flows, catalogued much of the damage, and analyzed the nature of the geologic processes that led to both the initiation of the lahars and the extensive damage resulting from them. In addition, the team interviewed many survivors and participants in the emergency preparedness and recovery efforts. The lessons learned can be summarized as follows:

  • The Nevado del Ruiz volcano continues to present a threat to the region from the formation of additional and potentially larger lahars to other volcanic-related phenomena such as ash fallout. Longer-term research to continuously assess the Ruiz hazard is needed.

  • Special care must be given to properly educate as well as warn those members of the community who will be required to take action during an emergency situation to effectively communicate the potential risk.

  • Risk communication and warnings are taken more seriously when accompanied by materials that provide adequate information, specifically about both the nature of the hazard and the steps that must be taken to mitigate the effect of the hazard. These factors are particularly important for hazards that have not manifested themselves in the lifetimes of the people who face them.

  • The recovery efforts in many ways had characteristics similar to other disaster recovery efforts. The study and analysis of these efforts would have been enhanced had collection of socioeconomic data been undertaken prior to the event.

  • A need to warn quickly and effectively must be emphasized.

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