INSIVUMEH reported that eruptive activity continued at Santa Maria’s Santiaguito lava dome complex during 11-17 October with lava extrusion at Caliente dome. Incandescence from the dome was visible during most nights and early mornings, and occasionally from the lava flow on the WSW flank. Explosions triggered incandescent avalanches that descended the dome’s flanks in all directions. Block avalanches descended drainages on the SW, S, SE, and E flanks; during 12-13 and 16-17 October the avalanches were occasionally accompanied by small pyroclastic flows. Daily weak-to-moderate explosions generated gas-and-ash plumes that rose 800-1,000 m above the dome and drifted in multiple directions. During 13-14 October explosions occurred at a rate of 1-2 per hour and produced block-and-ash flows that descended the SW, S, and SE flanks and left gray ash deposits.

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)