INSIVUMEH reported that on 24 March a loud explosion from Santa María's Santiaguito lava dome complex was followed by a pyroclastic flow that descended the E flank. A few hours later an explosion produced an ash plume that rose 600 m above Caliente dome and drifted W. Based on a METAR notice, information from INSIVUMEH, and analyses of satellite imagery, the Washington VAAC reported a diffuse ash plume on 28 March. Explosions reported by INSIVUMEH during 27-28 March produced ash plumes that rose 300-600 m above the dome and drifted over nearby farms and villages. Block avalanches descended the 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.

Sources: Instituto Nacional de Sismologia, Vulcanologia, Meteorologia, e Hidrologia (INSIVUMEH), Washington Volcanic Ash Advisory Center (VAAC)