INSIVUMEH reported that during 30 March-3 April cloud cover prevented visual observations of Caliente cone, part of Santa María's Santiaguito lava-dome complex, though sounds of small avalanches were noted. At 1000 on 3 April INSIVUMEH issued a special report stating that a strong explosion occurred, and pyroclastic flows descended the E and SE flanks. Parts of the E and W crater rim collapsed, and a mushroom-shaped ash cloud rose 4 km and drifted 30 km S, SW, W, and NW. During 4-5 April white plumes drifted SW and SE, and weak avalanches traveled short distances.

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)