INSIVUMEH reported that explosions from Santa María's Santiaguito lava-dome complex on 12 January produced ash plumes that rose to altitudes of 3.9-4.2 km (12,800-13,800 ft) a.s.l. Plumes drifted SW and ashfall was reported from areas downwind. Explosions occasionally produced incandescent blocks that rolled SW on 12 and 16 January. Based on satellite imagery, the Washington VAAC reported that diffuse ash plumes on 10, 12, and 14-16 January drifted SW and W. Plumes reached an altitude of 3.7 km (12,000 ft) a.s.l. on 14 January.

Geological Summary. Symmetrical, forest-covered Santa María volcano is part of a chain of large stratovolcanoes that rise above the Pacific coastal plain of Guatemala. The sharp-topped, conical profile is cut on the SW flank by a 1.5-km-wide crater. The oval-shaped crater extends from just below the summit to the lower flank, and was formed during a catastrophic eruption in 1902. The renowned Plinian eruption of 1902 that devastated much of SW Guatemala followed a long repose period after construction of the large basaltic-andesite stratovolcano. The massive dacitic Santiaguito lava-dome complex has been growing at the base of the 1902 crater since 1922. Compound dome growth at Santiaguito has occurred episodically from four vents, with activity progressing E towards the most recent, Caliente. Dome growth has been accompanied by almost continuous minor explosions, with periodic lava extrusion, larger explosions, pyroclastic flows, and lahars.

Sources: Washington Volcanic Ash Advisory Center (VAAC), Instituto Nacional de Sismologia, Vulcanologia, Meteorologia, e Hidrologia (INSIVUMEH)