During 28-29 October, weak-to-moderate explosions occurred at Santa María's Santiaguito lava-dome complex, producing gas-and-ash plumes to ~800 m above the volcano. Some explosions were followed by collapses of the lava dome in the crater of Caliente dome. Pyroclastic flows traveled down the volcano's NE and SW flanks after some collapses. The Washington VAAC reported on 31 October that satellite imagery showed a possible ash-bearing plume at a height of ~4.5 km a.s.l.

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 W 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)