INSIVUMEH reported that during 9-15 December explosions at Santa María's Santiaguito lava-dome complex generated ash plumes that rose as high as 900 m above the complex. The extrusion of blocky lava at the WSW part of Caliente dome generated block-and-ash flows that descended the NW, WSW, SW, and E flanks often reaching the base of the complex. The activity increased at 0430 on 11 December with notable avalanches of material and block-and-ash flows lava dome traveling down the W and SW flanks. Ash plumes drifted 15 km SW, causing ashfall in areas downwind including Finca Montebello, Loma Linda, and San Marcos Palajunoj. Activity remained elevated at least through 13 December; ash plumes drifted as far as 20 km W, SW, and S, and pyroclastic flows descended the flanks.

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.

Source: Instituto Nacional de Sismologia, Vulcanologia, Meteorologia, e Hidrologia (INSIVUMEH)