Report on Nevado del Ruiz (Colombia) — 25 August-31 August 2021
Smithsonian Institution / US Geological Survey
Weekly Volcanic Activity Report, 25 August-31 August 2021
Managing Editor: Sally Sennert.
Please cite this report as:
Global Volcanism Program, 2021. Report on Nevado del Ruiz (Colombia) (Sennert, S, ed.). Weekly Volcanic Activity Report, 25 August-31 August 2021. Smithsonian Institution and US Geological Survey.
Nevado del Ruiz
4.892°N, 75.324°W; summit elev. 5279 m
All times are local (unless otherwise noted)
Servicio Geológico Colombiano’s (SGC) Observatorio Vulcanológico y Sismológico de Manizales reported that during 25-31 August seismicity at Nevado del Ruiz had generally decreased compared to the previous week. Deformation data indicated minor changes. Gas-and-steam emissions were sometimes visible in satellite data and webcam images rising as high as 1.2 km above the summit and drifting NW and W. These emissions sometimes contained ash; on 26 August an ash emission rose 490 m and drifted WNW. The Alert Level remained at 3 (Yellow; the second lowest level on a four-color scale).
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.