INSIVUMEH reported that a strong Vulcanian explosion at 2140 on 17 September generated a dense ash plume that rose 2.5 km above Santa María's Santiaguito lava-dome complex and drifted 30 km SW. Another large explosion occurred during 17-18 September that also produced a 2.5-km-high ash plume. Five more moderate explosions were also detected. A moderate explosion during the evening of 19 September produced an ash plume that rose 800 m and drifted SW. Ashfall was reported in San Marcos Palajunoj.

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)