According to INGEOMINAS, the Observatorio Vulcanológico and Sismológico de Manizales reported that a satellite image of Nevado del Ruiz acquired on 6 June showed an ash plume rising from the crater and drifting NW, and ash deposits on the N, NW, W and SW flanks. Based on analysis of satellite imagery and information from INGEOMINAS, the Washington VAAC reported that gas plumes possibly containing some ash drifted 75-110 km W, WNW, and N during 7 and 9-10 June. Ash plumes drifted almost 30 km SE on 8 June. INGEOMINAS reported that on 11 June seismic signals indicated continuing ash emissions. The Alert Level remained at II (Orange; "eruption likely within days or weeks").

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.

Sources: Washington Volcanic Ash Advisory Center (VAAC), Servicio Geológico Colombiano (SGC)