INSIVUMEH reported that eruptive activity continued at Santa Maria’s Santiaguito lava dome complex during 5-11 July. Lava effusion at Caliente dome fed lava flows, and occasionally produced both avalanches and pyroclastic flows that traveled short distances down the S, SW, and W flanks. Daily weak and sometimes moderate explosions ejected ash plumes as high as 900 m above the dome that drifted W and NW, and triggered avalanches down the E, SE, and S flanks. Incandescence was observed at the crater and along lava flow margins during most nights and early mornings.

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)