INSIVUMEH reported that during 17-18 September explosions from Santa María's Santiaguito lava-dome complex produced ash plumes that rose 900 m and drifted W. Block avalanches descended the E flank of Caliente cone. Degassing sounds were reported during 19-21 September; gas plumes rose 150 m and drifted SW on 21 September. At 0820 on 21 September explosions from Caliente cone collapsed part of the SE crater rim, produced an ash plume that rose 2 km and drifted N and NE, and generated pyroclastic flows that descended the flanks. A strong shock wave was detected 20 km away and shook structures within 10 km. Explosions on 23 September produced ash plumes that rose 700 m and drifted E. Block avalanches again descended the E flank of Caliente cone. Two explosions on 24 September generated light gray ash plumes that rose 500 m and caused ashfall in areas around Monte Claro (S).

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)