INSIVUMEH reported that the eruption at Santa María’s Santiaguito lava-dome complex continued during 4-11 October. Effusion from Caliente cone fed lava flows that descended the San Isidro and El Tambor drainages on the W and SW flanks. Block avalanches from the dome, and from both the ends and sides of the flows, descended the S, SW, and W flanks. The avalanches sometimes generated minor ash plumes. Incandescence from the dome and the lava flows was often visible at night or during early mornings. Explosions during 6-7 October ejected incandescent material onto all flanks. A sulfur odor was reported in Mirador de Samriaguito. Small explosions were recorded during 9-10 October.

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)