INSIVUMEH reported that during 1-5 March as many as four explosions per hour at Santa María's Santiaguito lava-dome complex generated white plumes with ash that rose 500-700 m above the domes and drifted SE and SW. Avalanches of material descended the E and SE flanks of the lava dome. An explosion at 2155 on 4 March was heard in areas as far away as 10 km W, SW, S, and SE. The event ejected incandescent material 100 m high, produced ashfall around the volcano, and generated avalanches that traveled down the E and SE dome flanks reaching the base.

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)