Report on Nevado del Ruiz (Colombia) — October 1990
Bulletin of the Global Volcanism Network, vol. 15, no. 10 (October 1990)
Managing Editor: Lindsay McClelland.
Nevado del Ruiz (Colombia) Small ash emissions and seismicity
Please cite this report as:
Global Volcanism Program, 1990. Report on Nevado del Ruiz (Colombia) (McClelland, L., ed.). Bulletin of the Global Volcanism Network, 15:10. Smithsonian Institution. https://doi.org/10.5479/si.GVP.BGVN199010-351020.
Nevado del Ruiz
4.892°N, 75.324°W; summit elev. 5279 m
All times are local (unless otherwise noted)
Many small ash emissions occurred during October, although seismicity remained at low levels. Two small swarms of high-frequency earthquakes were recorded on 14 and 22 October. Tremor episodes (2 cm2 maximum reduced displacement) were prominent and were occasionally associated with small ash emissions. Although EDM measurements showed important changes, dry-tilt did not show ground deformation. Similarly, EDM indicated 6.6 µrad of deformation at one station during September, while dry-tilt did not show any significant changes. The average SO2 flux for the month, measured by COSPEC, was 1,630 t/d, compared to 2,448 t/d in September.
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: C. Carvajal, INGEOMINAS, Manizales.