The Instituto Nacional de Sismologia, Vulcanologia, Meteorologia, e Hidrologia (INSIVUMEH) reported ongoing eruptive activity at Santa Maria’s Santiaguito dome complex during 7-14 January with continuing lava extrusion at Caliente dome. Daily explosions, as many as 11 per hour when reported, generated gas-and-ash plumes that rose as high as 1.2 km above the dome and drifted as far as 40 km NW, W, SW, S, and SE. Effusion of blocky lava and collapses of material produced block avalanches that descended the flanks in multiple directions almost daily; the avalanches could sometimes be heard in areas several kilometers away. Collapsed material produced short pyroclastic flows on a few of the days. Incandescence at the crater was sometimes visible during dark hours. Ashfall was reported during 10-11 January in areas downwind including San Marcos (10 km SW), Finca El Patrocinio (9 km SSW), Loma Linda Palajunoj (7 km SW), Llanos de Pinal, and surrounding areas, and forecasted for areas downwind on most of the other days.

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)