On 10 October, INSIVUMEH reported that explosions from Santa María's Santiaguito lava dome complex produced ash plumes that rose to an altitude of 4.4 km (14,400 ft) a.s.l. and drifted SE. A lava flow on the SW flank produced avalanches of blocks. On 12 October, lahars in multiple drainages that carried tree branches, fine sediment, and blocks of multiple sizes, flooded the Samala river (to the E and S) as far as the Pacific coast, 70 km 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)