Instituto Nacional de Sismologia, Vulcanologia, Meteorologia, e Hidrologia (INSIVUMEH) reported ongoing eruptive activity at Santa Maria’s Santiaguito lava-dome complex during 17-24 September with lava extrusion, block collapses, and avalanches at the Caliente dome complex. Effusion of blocky lava produced block avalanches on the dome’s flanks and occasional short pyroclastic flows that descended the W, SW, and S flanks; the deposits created promontories of unstable material near the top of the 2022 lava flow located in the Zanjón Seco and San Isidro drainages. Incandescence was visible during dark hours from avalanches of material at the dome as well as explosions. Daily explosions (a few per hour) generated gas-and-ash plumes that rose as high as 800 m above the summit and sometimes drifted mainly W and SW. Ashfall was reported in San Marcos (8 km SW), Loma Linda Palajunoj (7 km SW), and surrounding areas during 17-18 September.

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)