Instituto Nacional de Sismología, Vulcanologia, Meteorologia e Hidrología (INSIVUMEH) reported that eruptive activity continued at Santa Maria’s Santiaguito lava-dome complex during 31 July-6 August with lava extrusion, block collapses, and avalanches at the Caliente dome complex. The continuous effusion of blocky lava produced block avalanches on the dome’s flanks and occasional short pyroclastic flows that descended multiple flanks. During most nights and early mornings incandescence was visible around Caliente dome, along the upper parts of the lava flow, and at several locations on other flanks. Daily explosions (a few per hour on most days) generated gas-and-ash plumes that rose 400-800 m above the summit and drifted NW, W, and SW. Ashfall was reported in San Marcos (8 km SW) and Loma Linda Palajunoj (7 km SW) on 1 and 4 August.

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)