SGC reported that an episode of volcanic tremor at Nevado del Ruiz began at 0923 on 3 March and was associated with an ash plume that rose 3 km above the crater. Based on satellite and webcam images, the Washington VAAC stated that an ash plume rose to an altitude of 9.1 km (30,000 ft) a.s.l. (about 800 m higher than the SGC estimate) and drifted NW. Later that day satellite images detected an ash plume drifting 40 km W. According to the VAAC, the Bogota MWO reported that on 7 March an ash plume rose to an altitude of 6.1 km (20,000 ft) a.s.l. and drifted WNW.

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