Report on Nevado del Ruiz (Colombia) — April 1987
Scientific Event Alert Network Bulletin, vol. 12, no. 4 (April 1987)
Managing Editor: Lindsay McClelland.
Nevado del Ruiz (Colombia) Continued moderate-high seismicity; acid rain kills birds
Please cite this report as:
Global Volcanism Program, 1987. Report on Nevado del Ruiz (Colombia) (McClelland, L., ed.). Scientific Event Alert Network Bulletin, 12:4. Smithsonian Institution. https://doi.org/10.5479/si.GVP.SEAN198704-351020.
Nevado del Ruiz
4.892°N, 75.324°W; summit elev. 5279 m
All times are local (unless otherwise noted)
Seismicity continued at moderately high levels in April; 920 low-frequency and 172 high-frequency events were registered. The tremor signal has remained weak compared to 1986. Seismic activity peaked on 16 and 17 April when 80-90 events were recorded each day [see also 12:05]. One week later, deformation measurements showed changes of as much as 5 µrad/day. SO2 levels, measured by COSPEC, averaged 1,000-1,200 t/d.
Geologic Background. Nevado del Ruiz is a broad, glacier-covered volcano in central Colombia that covers more than 200 km2. Three major edifices, composed of andesitic and dacitic lavas and andesitic pyroclastics, have been constructed since the beginning of the Pleistocene. The modern cone consists of a broad cluster of lava domes built within the caldera of an older edifice. The 1-km-wide, 240-m-deep Arenas crater occupies the summit. The prominent La Olleta pyroclastic cone located on the SW flank may also have been active in historical time. Steep headwalls of massive landslides cut the flanks. Melting of its summit icecap during historical eruptions, which date back to the 16th century, has resulted in devastating lahars, including one in 1985 that was South America's deadliest eruption.
Information Contacts: E. Parra, INGEOMINAS, Manizales.