INSIVUMEH reported that eruptive activity continued at Santa Maria’s Santiaguito lava dome complex during 20-26 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 WSW flank lava flow. Daily explosions generated ash, gas, and steam plumes that rose as high as 900 m above the summit and drifted multiple directions on most days, and on 20 March rose 2.2 km above the summit. The explosions occurred at rates between 1 and 7 per hour that generated block avalanches on the dome’s flanks and occasional short pyroclastic flows that descended multiple flanks. Sometimes the block avalanches were accompanied by rumbling sounds. On 21 and 22 March ashfall was reported in Loma Linda (7 km W), San Marcos Palajunoj (8 km SW) and other communities in this area; ash caused hazy conditions around the volcano on 24 and 25 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)