On 9 November Servicio Geológico Colombiano’s (SGC) Observatorio Vulcanológico y Sismológico de Manizales reported that intense seismicity at Nevado del Ruiz had been recorded for the previous few weeks. Deformation data indicated minor changes. Low-temperature thermal anomalies were visible in satellite images during the previous week. Gas-and-steam emissions were sometimes visible in satellite data and webcam images rising as high as 1.9 km above the summit and drifting NE and E. These emissions sometimes contained ash; during 0735-0815 on 3 November an ash plume rose 1.4 km above the summit. Ash emissions on 7 November drifted W and NW, causing ashfall in Manizales and Villamar?a, both 25 km NW. The La Nubia airport temporarily suspended operations. 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.

Source: Servicio Geológico Colombiano (SGC)