INSIVUMEH reported that the eruption at Santa María’s Santiaguito lava-dome complex continued during 4-11 April. Daily explosions produced gas, steam, ash plumes that rose as high as 1 km above the complex and drifted sometimes as far as 8 km W, SW, and S; during 8-9 April the plumes drifted W and rose as high as 1.8 km. Rumbling was barely audible on nearby farms during 8-9 April. Effusion from Caliente dome fed lava flows that slowly descended the San Isidro and Zanjón Seco drainages on the W and SW flanks. Incandescence from the dome and the lava flows was visible nightly and some early mornings. Block avalanches from the dome, and from both the ends and sides of the flows, descended the S, SW, and W flanks were reported almost daily. Residents were reminded to stay at least 6 km away from the complex.

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)