Based on analysis of satellite imagery, the Washington VAAC reported that during 17-20 and 22 December ash plumes from Caliente dome in Santa María's Santiaguito lava dome complex drifted SW, W, and NW. Plumes rose to an altitude of 5.8 km (19,000 ft) a.s.l. on 18 December. On 22 December, INSIVUMEH reported that white plumes drifted SW and avalanches occurred from the crater rim. Explosions the next day resulted in pyroclastic flows that descended the flanks and ash plumes to an altitude of 3.3 km (10,800 ft) a.s.l. that drifted S and SW.

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