Report on Nevado del Ruiz (Colombia) — October 1989
Scientific Event Alert Network Bulletin, vol. 14, no. 10 (October 1989)
Managing Editor: Lindsay McClelland.
Nevado del Ruiz (Colombia) Seismic energy release declines
Please cite this report as:
Global Volcanism Program, 1989. Report on Nevado del Ruiz (Colombia) (McClelland, L., ed.). Scientific Event Alert Network Bulletin, 14:10. Smithsonian Institution. https://doi.org/10.5479/si.GVP.SEAN198910-351020.
Nevado del Ruiz
4.892°N, 75.324°W; summit elev. 5279 m
All times are local (unless otherwise noted)
In October, seismic energy release and the number of high- and low-frequency events decreased to the lowest level since early 1988 (figure 35). High-frequency events were centered under and N of the crater. Tremor was unstable during October, with frequencies oscillating between 5 and 1.8 Hz during the first days of the month. Near the end of the month, tremor frequency reached 1.6 Hz with a reduced displacement of 0.38 cm2. SO2 emission ranged from 174 to 2,648 t/d, averaging 1,345 t/d during the month. Deformation measurements (electronic and dry-tilt) showed no significant changes.
|Figure 35. Daily seismic energy release (low- and high-frequency events) at Ruiz, July 1985-October 1989. Courtesy of INGEOMINAS.|
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.