Servicio Geológico Colombiano’s (SGC) Observatorio Vulcanológico y Sismológico de Manizales reported that during 28 December 2021 to 3 January 2022 seismicity at Nevado del Ruiz was at similar levels to the week before, characterized by periods of continuous volcanic tremor, long-period events, and very-long-period earthquakes, indicating movement of fluids. These earthquakes occurred in the vicinity of Arenas Crater. Additional earthquake signals indicating rock fracturing were located in the SW, SE, and NE parts of the volcano. Several periods of “drumbeat” seismicity, indicting growth of the lava dome, were recorded during 29-30 December and 3 January. Several low-level thermal anomalies were identified in satellite images during the week. The highest gas-and-steam plume rose about 1.2 km above the summit, recorded on 3 January. 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)