INSIVUMEH reported that nighttime incandescence was observed in the crater of Santa María’s Santiaguito lava-dome complex during 9-15 November. The lava flows continued to descend the San Isidro and El Tambor drainages, as well as the S flank. Block-and-ash avalanches from the dome, and from the middle and front of the lava flows, descended the W, SW, and S flanks. Fine ash fell on the perimeter of the volcano. Moderate gas-and-steam plumes rose as high as 500-700 m above the dome complex that extended 3-6 km E, SE, S, SW, and W.

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 W 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)