INSIVUMEH reported that the eruption at Santa María’s Santiaguito lava-dome complex continued during 2-9 August. Lava flows continued to advance in the San Isidro and El Tambor drainages on the W and SW flanks and were as long as 3.7 km by 5 August. Block avalanches from the W part of Caliente cone, and from both the ends and sides of the flows descended the S, SW, and W flanks. The avalanches generated ash plumes that rose about 1 km and drifted SW, S, and E, causing ashfall in areas downwind including La Florida, Monte Claro, San Marcos Palajunoj, Loma Linda, and Las Marías. Incandescence from Caliente cone and the lava-flow fronts was sometimes visible at night.

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)