INSIVUMEH reported that the eruption at Santa Maria’s Santiaguito lava dome complex continued during 27 June-4 July. Lava dome effusion generated avalanches, pyroclastic density currents (PDC) on all flanks, and fed active lava flows. Daily weak-to-moderate explosions also caused avalanches on all flanks. Explosive activity was highest during 28-29 June with 40 events that produced W- and NW-drifting ash plumes. Almost daily emissions of steam, gas, and sometimes ash rose as high as 1 km above the dome and drifted in multiple directions. Incandescence at the crater and along lava flow margins was visible 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)