During 18-22 December, weak-to-moderate explosions occurred at Santa Maria's Santiaguito lava-dome complex. The resultant plumes drifted mainly S and SE towards the Monte Claro, Monte Bello, La Florida, and El Faro fincas (ranches). Nearly constant avalanches of volcanic material traveled S and SW from the fronts of lava flows. Based on information from Retalhuleu airport, the Washington VAAC reported a minor emission from Santiaguito on 18 December. No ash was visible on satellite imagery.

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