ued, and by October more seismographs and tiltmeters were installed on Ruiz. On November 12, 1985, the day prior to the major eruption of Ruiz, geologists who climbed to the summit to collect gas samples observed no clear signs of an imminent explosion.
A variety of efforts were undertaken to increase awareness of the risk presented by Nevado del Ruiz subsequent to the scientific discovery of an impending eruption and prior to the November 13, 1985 event. These efforts involved many Colombian and other organizations.
In August 1985, INGEOMINAS published the first of a variety of reports designed to organize for or further the understanding of volcanic risk in response to the Ruiz threat. The first of these reports, Riesgos Sísmicos y Volcánicos Del Parque Natural De Los Nevados (Seismic and Volcanic Risks of Los Nevados Natural Park), was an effort to report on recommended research and monitoring on six Colombian volcanoes and the areas around them. The research agenda proposed recognized the volcanic risk in Colombia, particularly in volcanic regions where people lived close by. The report requested a budget to perform the recommended studies and recognized the inevitable involvement of international scientists in the study of Ruiz.
The proposed project was designed to be undertaken in stages, and it recognized the need for additional funds and international assistance. It also pointed to the need to involve organizations at all levels of Colombian government—including local governments—to define risk and hazard. The preliminary request sought funding to prepare a volcanic risk map for Ruiz; it was recognized that such a map would be needed to help make good hazard preparedness decisions.
A preliminary version of the risk map was completed on October 7, 1985, and it was accompanied by an explanatory report entitled Mapa Preliminar De Riesgos Volcánicos Potenciales Del Nevado Del Ruiz (Preliminary Map of Potential Volcanic Risks Associated with Nevado del Ruiz). An additional report accompanied the preparation of the risk map. This report, entitled Informe Preliminar De Las Actividades Desarrolladas Período Julio 20-Octubre 7 de 1985, explained that Ruiz was in a stage of activity but that it could not be precisely predicted when an eruption would occur. Continued volcanic activity was reported along with minor ashfall, de-icing of the mountain top, small mudflows, and increased volcanic crater size. The