Report on Nevado del Ruiz (Colombia) — October 1991
Bulletin of the Global Volcanism Network, vol. 16, no. 10 (October 1991)
Managing Editor: Lindsay McClelland.
Nevado del Ruiz (Colombia) Continued weak seismicity and SO2 emission
Please cite this report as:
Global Volcanism Program, 1991. Report on Nevado del Ruiz (Colombia) (McClelland, L., ed.). Bulletin of the Global Volcanism Network, 16:10. Smithsonian Institution.
Nevado del Ruiz
4.892°N, 75.324°W; summit elev. 5279 m
All times are local (unless otherwise noted)
Although seismicity remained at very low levels in October (figure 46), there was a slight relative increase in long-period activity. High-frequency earthquakes were centered NE and SW of the summit. The SO2 flux varied between moderate and low values, and deformation measurements showed no significant changes.
Geological Summary. 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: C. Carvajal, INGEOMINAS, Manizales.