INSIVUMEH reported that the Santa Maria-Santiaguito lava dome complex remained highly active during 22-28 March. On most days steady degassing from the dome produced gas plumes that drifted S and SW. Incandescence from the dome and along lava flow margins was visible most nights or early mornings. The lava flow that extended 4.3 km down the SW flank in the San Isidro and Zanjón Seco drainages was active. Activity from the lava dome included explosions and avalanches, and small pyroclastic flows during 22-23 March. Daily weak to moderate explosions generated ash plumes up to 1 km above the crater that drifted SW and W, and avalanches traveled down multiple 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)