INSIVUMEH reported that on 8 December explosions from Santa María's Santiaguito lava dome complex produced ash plumes that rose 700 m above Caliente dome and drifted SE. Ashfall was reported on the SE flanks and in the village of San José. The seismic network recorded block avalanches in addition to the explosions. The Washington VAAC stated that on 10 December an ash plume was observed in satellite imagery drifting 21 km W. According to INSIVUMEH, explosions ejected ash plumes that rose 300-700 m above the crater and drifted SE on 13 December. During 13-14 December block avalanches were detected by the seismic network. On 14 December weak pyroclastic flows were observed.

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)