INSIVUMEH reported that during 29 December-5 January explosions at Santa María's Santiaguito lava-dome complex generated ash plumes that rose 800-900 m above the complex. Plumes sometimes drifted about 1 km SW. The extrusion of blocky lava at Caliente dome generated block-and-ash flows that descended the NW, W, SW, and E flanks, often reaching the base of the complex. Ashfall on the flanks was noted almost daily, though during 1-2 January ashfall was also reported in Loma Linda (6 km WSW) and San Marcos Palajunoj (8 km 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.

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