On 31 August, INSIVUMEH reported that a lahar, 8 m wide and 1.5 m high, descended S down Santa María's Nima I river, carrying fine material, tree branches, and blocks. Explosions from the Santiaguito lava dome complex produced ash plumes that rose to 4.3 km (14,100 ft) a.s.l. and drifted SW. During 3-4 September, explosions produced ash plumes that rose to an altitude of 4.4 km (14,400 ft) a.s.l. and drifted W. A lava flow on the SW flank produced avalanches.

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)