INSIVUMEH reported that eruptive activity continued at Santa Maria’s Santiaguito lava dome complex during 6-12 March with a lava extrusion and avalanches at the Caliente dome. Incandescence from the dome was visible during most nights and early mornings, and occasional incandescence was also present along the upper part of the lava flow on the WSW flank. Daily explosions generated gas-and-ash plumes that rose 600-900 m above the summit and drifted NW, W, SW, and S; the explosions occurred at a rate of 1-8 per hour on at least a few of the days where reported. The explosions produced block avalanches on the dome’s flanks and generated occasional, short-range pyroclastic flows that mainly descended the W, S, and E flanks. Block avalanches from the dome and the margins of the upper part of the lava flow were also sometimes visible. Rumblings were heard occasionally. Ashfall was reported in Belén (10 km S), Calaguache (9 km S), and Las Marías (10 km S) during 5-6 March and in San Marcos Palajunoj (8 km SW), Loma Linda (7 km W), and other nearby communities during 6-7 and 10-12 March; ash caused hazy conditions around the volcano during 8-9 March.

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)