INSIVUMEH reported that an explosion from Santa María's Santiaguito lava-dome complex at 0529 on 1 August generated an ash plume that rose 150 m above the crater and drifted SW. Ashfall was reported in the ranches of Monte Claro (S) and La Florida (5 km S). A few avalanches from the lava dome traveled short distances. On 4 August a weak explosion at 0613 produced a white plume that rose 300 m and drifted SW. Minor amounts of ash fell in Monte Claro, El Rosario (45 km SW), and Palajunoj (S). Avalanches were generated by the lava flow on the S flank. Seven explosions were detected during 5-6 August; the explosions generated avalanches on the NE flank, and degassing, jet-engine, and rumbling sounds. The last explosion was followed by a weak pyroclastic flow that traveled S and a moderate one that traveled SW. White and gray plumes rose 500-800 m. Ashfall was reported in the Palajunoj area. Later that day on 6 August OVSAN reported that explosions were heard, and ash plumes that rose 500-800 m drifted W and SW.

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)